Dissertations / Theses on the topic 'Macrobentho'

Hypoxia and anoxia have significant deleterious ecological effects on living resources throughout many estuarine and marine ecosystems worldwide. Brief periods of low oxygen facilitate transfer of benthic production to higher trophic levels as many benthic infaunal species have shallower sediment depth distributions during hypoxic events. A baited time-lapse camera equipped with a water quality datalogger was used to document in situ exploitation of oxygen-stressed benthic invertebrate prey organisms by mobile fish and crustacean predators during alternating normoxia-hypoxia cycles in the York River. Based on photographic and diver observations, this hypoxiainduced benthic-pelagic transfer of production is more likely to occur when environmental dissolved oxygen concentrations rise above an apparent threshold between 1 and 2 ml/1. When oxygen concentrations decline below 2 ml/1, the functional response of the predator to increased prey availability is interrupted. There is no energy gain by the predator until oxygen concentrations rise above this critical level when predators return to affected areas and resume feeding activity.

La tesi illustra due diverse attivita' svolte: Dredging activities for beach nourishment in an area offshore Montalto di Castro (VT): effects on Polychaete community In collaboration with ICRAM Istituto Centrale per la Ricerca scientifica e Tecnologica applicata al Mare, Roma (i risultati del lavoro sono stati pubblicati nell'articolo Marzialetti S., Gabellini M., La Porta B., Lattanzi L., La Valle P., Paganelli D., Panfili M, Targusi M., Nicoletti L., (2006) Attivita' di dragaggio ai fini di ripascimento al largo di Montalto di Castro (VT): effetti sul popolamento a policheti Biol. Mar. Med. 13(1), 601-605 e Changes in benthic diversity along a salinity gradient in the North Sea (Kattegat) Baltic Sea transition. Spatial scales and taxonomical affiliation. In collaboration with NERI National Environmental Research Institute, Roskilde - DK, i cui risultati sono illustrati nella tesi

The benthic macroinvertebrate fauna of deep (>3.0m) and shallow ( <0.5m) regions at four sites in the upper Swan River estuary were sampled over a six month period from September 1993 to December 1994. Changes in the benthos were examined in order to determine the effect of a number of physico-chemical parameters pertaining to the progression of a saline wedge from the middle to upper regions of the estuary during spring and summer. The saline wedge was characterised by a higher salinity than overlying waters, and low dissolved oxygen concentration. With the arrival of the saline wedge, salinities increased rapidly and dissolved oxygen concentrations fell to below 2.0mgL·1. Oxygen recovery was evident two to three weeks after the arrival of the saline wedge, however, the magnitude of oxygen recovery was highly variable between sites. Turbidities at all sampling sites increased abruptly with the arrival of the saline wedge. This was due to the coagulation of colloidal particles caused by an increase in metallic ions, particularly calcium and magnesium in more saline water. Turbidities fell as abruptly as a more homogenous salinity profile was established. The movement of the saline wedge through the upper estuary was affected by a number of factors including surface freshwater discharge, barometric pressure and tidal variation. Forty seven benthic macroinvertebrate species were collected from the upper Swan River Estuary. Shallow sites supported a diverse, species rich fauna comprising bivalves, polychaetes, crustaceans and other taxa. Deep sites were comparatively depauperate, being dominated by one species of polychaete. Classification and ordination techniques revealed further separation of shallow sites into upstream/downstream groups. Downstream sites had a more diverse and species rich fauna, whereas the fauna upstream was dominated by a small leptonid bivalve. The differences in the faunal assemblages were explained by habitat variation between deep and shallow and upstream and downstream sites, and physical stress induced by the saline wedge. Shallow sites, in general, were characterised by fine to medium sands which provided suitable attachment sites for a number of bivalves and a tube building media for some amphipods and polychaetes. Dissolved oxygen concentrations in the shallows were generally high throughout the sampling period at all sites. Deep sites however, were characterised by black, organically enriched anoxic mud, which was inhabited only by a spionid polychaete. Salinity was an important factor in the distribution of relatively few species, predominantly the amphipods and isopods. This may be due to the euryhaline nature of the species inhabiting this region and their adaptations to extremes in salinity and temperature. A negative correlation between species richness and turbidity suggested that the higher turbidities present in the deeper regions may have impacted on the benthic fauna. Absence of a number of deposit feeding species contributed to the decrease in richness, which suggested these species were intolerant to large particulate fluxes. The main effect of the saline wedge appeared to be deoxygenation, which explained much of the spatial and temporal variation of the benthos. The dominant species (particularly Prionospio cirrifera) in the deep regions were largely opportunistic and flourished in a very stressful environment characterised by hypoxia and on some occasions anoxia. Larger, non opportunistic species, intolerant to low dissolved oxygen concentrations, were either absent from the deeper regions or suffered population collapses during periods of oxygen stress. Further research is required to observe whether many of the trends recorded in this study persist under different annual climatic conditions. In particular, this study did not encompass autumn and winter periods, where investigation into the response of the benthos to winter flushing and the subsequent development of riverine conditions is still needed.

The lower Rappahannock River, a subestuary of the Chesapeake Bay, is affected by seasonal low dissolved oxygen events that are intermittent and vary in intensity. Overall, macrobenthic abundance and species number were low, decreasing towards the channel and upriver, where dissolved oxygen concentrations were lowest. Mortality of macrobenthos in early summer was attributed to hypoxia. Species abundances and number declined with the onset of hypoxia, and did not recover in the deep channel until the fall. Tolerance of macrobenthos to hypoxia appeared to be species-specific. Recruitment of hesionid polychaetes occurred in summer during normoxia, but mortality followed during hypoxia, suggesting that macrobenthic assemblages in affected areas may be largely structured by the relationship between the timing of low dissolved oxygen events and species life histories. Laboratory experiments with dominant polychaete species (Streblospio benedicti and Lomia medusa) were conducted to determine their tolerance and behavior to hypoxia, anoxia, and hydrogen sulfide. Under severe hypoxia, S. benedicti survived for two weeks without significant mortality at two experimental dissolved oxygen concentrations (14.5 and 7% air saturation). In anoxia, all worms died within 55 hrs. Larvae survived severe hypoxia without displaying behavioral ill effects for at least 4 days. The behavior of S. benedicti was modified; feeding and burrowing activities ceased, and worms came out of their tubes onto the sediment surface. L. medusa showed higher tolerance of anoxia, surviving up to 5 days. Survival under prolonged hypoxia was significantly reduced. The behavior of L. medusa was also modified by hypoxia and anoxia. Worms ceased feeding and protruded head and abdominal tip out of their tubes. Worm occurrences on the sediment surface at time of death were treatment-dependent. Survival of both species was not significantly reduced when worms were exposed to anoxia with moderate concentrations of hydrogen sulfide. These results are discussed in terms of species distributions, presence of hydrogen sulfide in sediment, and mechanisms of resistance to sulfide toxicity.

La presente tesi si inserisce nel contesto del progetto europeo Theseus, che ha l’obiettivo di pianificare strategie di difesa sostenibili nei confronti dell’erosione costiera e del rischio di inondazioni. E’ stata indagata la zona intertidale di sei spiagge della costa emiliano-romagnola, diverse per caratteristiche morfodinamiche, grado di antropizzazione e modalità di gestione contro l’erosione. Lido di Spina, Bellocchio e lido di Dante sono siti più naturali, Cervia, Cesenatico e Cesenatico sud sono antropizzati per la presenza di strutture di difesa costiera o attività di bulldozing. Lo scopo principale è stato quello di valutare la risposta della componente macrobentonica a variazioni morfodinamiche conseguenti alla differente gestione. I principali risultati possono essere così riassunti. Bellocchio, sito naturale, si è rivelato il più differente per tipologia di sedimento, fine e argilloso, e comunità presenti, con specie non tipiche delle spiagge sabbiose, quali Polydora e Mytilus galloprovincialis. Lido di Dante, anch’esso naturale, si pone all’opposto, con un sedimento più grossolano e caratterizzato sia dalla dominanza di Lentidium mediterraneum, la cui presenza evidenzia il maggiore grado di idrodinamismo del sito, sia dalle specie Scolelepis squamata ed Eurydice spinigera, tipiche delle spiagge sabbiose esposte al moto ondoso. Cervia, Cesenatico e Cesenatico sud presentano un numero di specie e di individui minore rispetto agli altri siti, come probabile conseguenza della gestione antropica, e comunità che rispecchiano le variazioni idrodinamiche dovute alla presenza di barriere. In generale, le differenze individuate sia fra le comunità che fra i descrittori sedimentari e morfodinamici, sembrano dovute alle caratteristiche peculiari dei siti e dal grado di antropizzazione piuttosto che dalla presenza di un vero e proprio gradiente morfodinamico o geografico. Questi risultati portano un contributo sostanziale alla problematica generale dell’impatto conseguente ai cambiamenti climatici e alla messa in opera di programmi di gestione sostenibili da un punto di vista anche ambientale.

Macrobenthos of the deep, northern Gulf of Mexico have been sampled with large box cores along multiple cross-depth transects extending from depths of 200 m out to 3700 m. Four major depth zones have been identified based on the faunal similarities (beta diversity) between geographic sites, with the two intermediate-depth zones being divided horizontally down the middle of the basin. The input of food resources appears to control the observed patterns. Each zone and sub-zone can be described by a characteristic animal density, biomass and biodiversity (alpha diversity). Highest densities and biomass occurred in two large submarine canyons, the Mississippi and De Soto Canyon, but the two habitats are markedly different. The alpha diversity displays an intermediate depth maximum. Species richness (gamma diversity) is highest on east mid-slope, due, we suggest, to habitat complexity, but alpha diversity is lowest at the canyon head due to extreme dominance by amphipods. Small mean individual size and low densities encountered are a reflection of the meager surface water primary production, albeit with exceptional isolated habitats in which detrital material is concentrated, such as canyons on the upper continental slope.

High latitude reef communities consisting of typical Caribbean fauna of variable composition and density exist on four parallel ridges at varying depths along the Broward County (FL, USA) coast. At least two of these ridges, at 7-13m and 15-30m depth, are drowned early Holocene coral reefs of 5 ky and 7 ky uncorrected radiocarbon age, respectively. Previous work has shown that the present reef communities growing on these ridges can be detected and mapped using acoustic remote sensing and has suggested that different benthic assemblages may exist between each of these reefs. In this study, in situ community data was taken in four corridors on each reef using fifty-meter line-intercept transects. Multidimensional scaling analyses of the in situ community data show distinct differences in benthic community structure across several spatial gradients within the county. This clustering agrees well with an acoustic data set, taken in the same four corridors along the Broward County coast. Analysis of diversity statistics revealed that whereas species diversity (H’) was consistent throughout the county, species richness (d) and eveness (J’) increased along a north-south gradient. Total scleractinian cover was generally low in all areas (<6% mean cover), and also increased along a north-south gradient in the reef communities closest to shore (ridge complex communities). Percent scleractinian coral cover on all other reef communities (inner, middle, and outer reefs) was consistent throughout the county with Montastrea cavernosa being dominant over the M. annularis complex, which is the more typically dominant reef builder in Caribbean systems. Notably absent from the scleractinian fauna of this area was the major Caribbean reef-builder Acropora palmata. A rich alcyonacean fauna (12 genera) was present on all reefs in the county, and typically was the faunal group with highest cover (~20% mean cover countywide) and most important in terms of determining community structure. Although 2-year average water temperature never fell below 21 degrees C, which is within generally accepted limits for reef building, scleractinia were small in size and though not directly investigated, no observable evidence for late Holocene reef building exists. Habitat maps produced from this study show evidence for the unevenly distributed existence of at least six different community types within Broward County: Type 1: shallow, sponge-dominated community; Type 2: shallow, stony- and soft coral-dominated community; Type 3: shallow, zoanthid and soft coral-dominated community; Type 4: soft coral-dominated community; Type 5: zoanthid and macroalgae-dominated community; Type 6: Macroalgae, massive sponge, and soft coral-dominated community.

Macrozoobenthic community structure and composition was investigated along a subtidal-intertidal gradient in the Mngazana Estuary. Six transects were sampled between the spring high water mark (HWST) and the bottom of the river channel in the lower estuary. Fifteen replicate samples were collected along each transect using a Van Veen type grab (211 cm2 bite) during each of three sampling sessions. Samples were sieved through a 500 μm mesh bag and the invertebrates stored in bottles for further analysis in the laboratory. Additional grab samples were collected for sediment particle size analysis and organic matter. Physical variables measured at each transect included: salinity, temperature, dissolved oxygen, depth, pH, percentage mud, organic content and turbidity. Sediment compactness was measured at all intertidal transects and additional sediment samples were collected at mid shore and high shore transects for percentage water content analysis. A total of 104 species were recorded along the intertidal-subtidal gradient in the sampling area. Species richness was higher in the subtidal zone compared to the intertidal zone and polychaetes numerically dominated the macrozoobenthic community at most transects, during all three sessions. At high shore transects the community was characterised by having fewer species, consisting mostly of brachyurans, polychaetes and gastropods. Shannon diversity index (H’) was generally higher for subtidal transects (x¯ = 2.3; range: 2.8 to 1) than for intertidal transects (x¯ = 1.4; range: 2.2 to 0.6) indicating that the distribution of individuals among species in the intertidal zone experienced greater variability. Results for Hill’s numbers followed the same trend as Shannon diversity with subtidal communities mostly consisting of abundant species followed by very abundant species. Intertidal communities generally exhibited lower numbers of abundant and very abundant species. Sedimentary characteristics played a major role in structuring benthic communities in comparison to other physico-chemical variables. Organic content and mud content of the substrate were identified as important factors influencing community patterns observed along the subtidal-intertidal gradient. In addition, sediment compactness and water content of the substrate was found to influence intertidal community structure. Subtidal community structure possibly had a greater dependence on seasonal variations in abiotic and/or biotic factors. Cluster dendrograms used in conjunction with MDS ordination mapping revealed that macrozoobenthic communities were generally distinct between high shore intertidal transects iii and subtidal transects. Most species exhibited a broad spatial distribution along the subtidal-intertidal gradient with mid and high shore transects being the exception. Most species also exhibited marked shifts in abundance and this was especially noticeable at the transition between the subtidal and intertidal zone. Two polychaete species, Prionospio sexoculata and Capitella capitata, were very abundant species and featured amongst the most numerically dominant species collected during each sampling session.

A macroalga Sargassum C. Agardh é de reconhecida importância ecológica nos ecossistemas costeiros, particularmente nas comunidades de costões rochosos de regiões tropicais e temperadas quentes. Está amplamente distribuída na costa sudeste brasileira, sendo frequente em costões rochosos de locais moderados ou protegidos do embate de ondas. Nesses ambientes pode formar bancos densos e extensos, estruturalmente complexos, capaz de prover microhabitats variados para uma grande diversidade de organismos. Os bancos de Sargassum são suscetíveis a mudanças sazonais na sua biomassa e/ou estado fisiológico relacionados a fatores abióticos e bióticos, sendo que essas variações podem influenciar drasticamente a distribuição e densidade dos organismos associados às algas. A complexidade desse substrato tem sido avaliada por meio de várias medidas, sendo quantitativas, como peso, as mais utilizadas. O presente trabalho tem como objetivo avaliar o desempenho de diferentes medidas quantitativas da complexidade estrutural de bancos de Sargassum filipendula i) no desenvolvimento temporal da complexidade estrutural da alga em dois ambientes hidrodinamicamente diferentes e ii) na composição e distribuição dos organismos epifaunais. Foram coletadas 15 frondes de S. filipendula por mês, durante 13 meses, nas praias da Fortaleza e do Lamberto, Ubatuba, SP. A fauna presente nessas frondes foi obtida através de lavagem e peneiramento contínuo. O período de amostragem caracterizou-se por ser atípico, apresentando altas temperaturas ao longo de todo o ano e um verão com baixa pluviometria. Este fato influenciou fortemente a variação sazonal do S. filipendula e epífitas associadas, ocasionando elevados valores de peso seco entre a primavera e verão. Os resultados das comparações das medidas analisadas mostraram que um único parâmetro não é representativo da complexidade estrutural da alga, uma vez que cada medida apresentou diferenças em relação à abundância e diversidade da fauna. Estes dois indicadores também mostraram correlação positiva com todos os parâmetros de complexidade do substrato. Houve diferença significativa entre as praias, e as frondes do Lamberto foram estruturalmente mais complexas, suportando a maior abundância. Contudo, foram as frondes do Fortaleza que exibiram os maiores valores de riqueza de grupos. Discute-se o emprego de mais uma de uma medida quantitativa para mensurar a complexidade estrutural do habitat.
The Sargassum C. Agardh macroalgae is of recognized ecological importance in coastal ecosystems, particularly in the rocky coastal communities of tropical and warm temperate regions. It is widely distributed on the southeast coast of Brazil, being frequent in rocky shores of moderate locations or protected from the impacts of waves. In these environments can form dense and extensive banks, structurally complex, capable of providing microhabitats varied for a great diversity of organisms. The Sargassum banks are susceptible to seasonal changes in their biomass and/or physiological status related to abiotic and biotic factors, and these variations can drastically influence the distribution and density of organisms associated with algae. The complexity of this substrate has been evaluated by means of several measures, being quantitative, as dry weight, the most used. The present work aims to evaluate the performance of different quantitative measures of the structural complexity of Sargassum filipendula banks i) in the temporal development of algae structural complexity in two hydrodynamically different environments and ii) in the composition and distribution of epifaunal organisms. Fifteen fronds of S. filipendula were collected per month, during 13 months, on the beaches of Fortaleza and Lamberto, Ubatuba, SP. The fauna present in these fronds was obtained through continuous washing and sieving. The sampling period was characterized by being atypical, presenting high temperatures throughout the year and a summer with low rainfall. This fact strongly influenced the seasonal variation of S. filipendula and associated epiphytes, causing high values of dry weight between spring and summer. The results of the comparisons of the measures analyzed showed that a single parameter is not representative of the structural complexity of the algae, since each measure presented differences in relation to the abundance and diversity of the fauna. These two indicators also showed a positive correlation with all parameters of substrate complexity. There was a significant difference between the beaches, and the Lambert fronds were structurally more complex, bearing the greatest abundance. However, it was the fronds of Fortaleza that exhibited the highest values of group richness. We discuss the use of one more of a quantitative measure to measure the structural complexity of the habitat.

Ce travail aborde un point particulier du fonctionnement bioenergetique des systemes fluviaux. L'importance et les modalites des processus engendres par la frequence et l'amplitude des incursions fluviales dans differents types d'annexes en liaison permanente ou non avec le fleuve, en l'occurrence le haut-rhone francais, sont abordees a des niveaux complementaires d'integration: l'eau, les sediments et les macro-invertebres endobenthiques consommateurs de sediments. L'existence d'un gradient des processus allogenes dans les annexes connectees au chenal principal du rhone est percue au travers de variables sedimentologiques telles que la texture, la porosite, la charge en carbone, la teneur en pigments chlorophylliens et le rapport c/n. Les macro-invertebres dominants du zoobenthos sont des tubificides (oligochetes limivores), en particulier le genre limnodrilus. Les implications de nature energetique des relations entre sediment et benthos sont abordees par une analyse des strategies adoptees par les tubificides et affectant notamment le mode de repartition, les densites, les biomasses et la productivite. Il s'avere que les zones de plus forte instabilite hebergent en regle generale des populations de tubificides a productivite plus elevee. D'autre part, le calcul d'un rendement ecologique a ete defini par le rapport entre la production nette des tubificides et la production nette de sediment (taux d'accumulation nette de sediment) exprimees conjointement en equivalent de carbone organique. Les resultats montrent qu'au niveau de deux annexes fluviales connectees en permanence au chenal principal et appartenant au meme secteur geographique (l'anse de la chavanne et la lone des pecheurs), les apports allochtones provenant du fleuve conjointement avec les apports autochtones generent un taux de sedimentation variable de 3,3 a 22,6 kg de sediment par m#2 et par an, soit l'equivalent de 74 a 471 g de cot par m#2 et par an. Le taux de reconversion annuel de cet apport en biomasse par les tubificides est beaucoup plus stable et voisin de 5%

Orientadores : Dr. Paulo da Cunha Lana, Dr. Britas Klemens Eriksson
Tese (doutorado) - Universidade Federal do Paraná, Setor de Ciências da Terra, Programa de Pós-Graduação em Sistemas Costeiros e Oceânicos. Defesa: Pontal do Paraná, 21/04/2017
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Resumo: Na presente tese, investiguei como a função do macrobentos marinho de sistemas sedimentares rasos é afetada pela poluição ambiental, complexidade do habitat e mudanças na composição específica das assembleias. Utilizei uma abordagem analítica baseada em traços biológicos para estimar potenciais mudanças na função do macrobentos nos processos ecossistêmicos associados aos sedimentos. Meus objetivos de pesquisa incluem avaliações do papel dos gradientes ambientais naturais ou antropogênicos na estrutura funcional do macrobentos; da aplicabilidade das abordagens baseadas em traços biológicos para analisar a qualidade ambiental do bentos; dos efeitos das mudanças na composição específica das assembleias na função do macrobentos; do efeito da complexidade do habitat na diversidade de traços funcionais; e do impacto de espécies funcionalmente relevantes no funcionamento ecossistêmico. Os resultados e conclusões mais importantes desta tese foram: 1. Baixa qualidade do ambiente bêntico causada pelo enriquecimento orgânico prejudica o estabelecimento de espécies com determinados traços funcionais, resultando em assembleias com baixa diversidade funcional. 2. Abordagens baseadas em traços biológicos são uma forma válida de avaliação os efeitos gerais da poluição orgânica no macrobentos. Tanto a análise de traços biológicos quanto os índices multivariados de diversidade funcional representam boas ferramentas analíticas para a investigação de mudanças na estrutura macrobêntica ao longo de gradientes de contaminação orgânica. 3. As mudanças na estrutura das assembleias promovidas pelo estabelecimento de espécies exóticas podem levar a grandes mudanças na diversidade funcional do macrobentos. Essas mudanças podem aumentar o potencial de bioturbação das assembleias e ter implicações para o funcionamento do ecossistema nos sistemas sedimentares. 4. O aumento da complexidade do habitat promovido pelas gramas marinhas pode promover funções relacionadas com os sedimentos devido ao estabelecimento de organismos bioturbadores que habitam camadas superficiais do sedimento. 5. As espécies funcionalmente relevantes do macrobentos podem promover o microfitobentos, seja através do aumento da bioturbação dos sedimentos ou através da estabilização dos sedimentos devido à atenuação da hidrodinâmica local. 6. As espécies funcionalmente relevantes podem promover cascatas funcionais por favorecer o estabelecimento de organismos que desempenham outras funções. Nos casos abordados nesta tese, as gramas marinhas promovem a infauna que vive próximo à superfície do sedimento e indiretamente media processos relacionados à bioturbação; a bioturbação macrobêntica influencia os produtores primários por afetar a estrutura microfitobêntica e os bancos de mexilhões promovem a produção primária por favorecer o microfitobentos. 7. Os índices de diversidade funcional são úteis como uma ferramenta exploratória para avaliar os efeitos gerais de perturbações ou gradientes ambientais na estrutura do macrobentos. Por outro lado, a análise de traços biológicos ou o enfoque em identidades funcionais representa uma melhor abordagem para avaliar os efeitos funcionais gerais do macrobentos na estrutura e nos processos ecossistêmicos.
Abstract: In this doctoral thesis, I investigate how the function of sediment living organisms is affected by environmental pollution, habitat complexity and changes in assemblage composition in shallow sedimentary systems. I used a trait-based approach to estimate potential changes in function of the macrobenthos in sediment-related ecosystem processes. My research subjects include: the role of natural and human induced gradients in shaping assemblage functional trait structure; the applicability of trait-based approaches to assess environmental status; the effects of changes in assemblage composition on macrobenthic function; the effect of complexity on functional diversity; and the impact of functionally relevant species on ecosystem functioning. The most important findings and conclusions of this thesis are: 1. Low benthic environmental quality driven by organic enrichment hinders the establishment of macrobenthic species with specific functional traits, resulting in assemblages with differentiated trait composition and decreased functional diversity. 2. Trait-based approaches are a reliable way to assess general effects of organic pollution on the macrobenthos. Both biological trait analysis and multivariate functional diversity are good analytical tools to analyze changes in macrobenthic structure across organic contamination gradients, although biomass- and abundancebased analysis can differ. 3. Changes in assemblage structure driven by establishing alien species can drive major changes in macrobenthic functional diversity. These changes can drive increased bioturbation potential, and have implications for ecosystem functioning in sedimentary systems. 4. Increased habitat complexity driven by seagrasses can promote sediment-related functions by favoring the establishment of shallow-living macrobenthic bioturbators. 5. Functionally relevant macrobenthic species can promote microphytobenthos either by increasing sediment bioturbation or by sediment stabilization via flow attenuation. 6. Functionally relevant species can promote functional cascades by favoring the establishment of organisms that perform other functions. In the cases addressed in this thesis, seagrasses promote shallow-living infauna and indirectly mediate bioturbation-related processes; macrobenthic bioturbation drives primary producers by affecting microphytobenthic structure; and mussel beds promote primary production by favoring microphytobenthos. 7. Functional diversity indices are useful as an exploratory tool to assess general effects of disturbances or gradients on macrobenthic structure. On the other hand, biological trait analysis or the focus on functional identities represents a better approach to assess the general functional effects of the macrobenthos on ecosystem structure and processes.
Samenvatting: In dit proefschrift onderzoek ik hoe de ecologische functie van bodemorganismen wordt beïnvloed door milieuvervuiling, habitatcomplexiteit en veranderingen in de soortensamenstelling binnen ondiepe sedimentaire ecosystemen. Ik heb gebruik gemaakt van een aanpak gericht op fenotypische kenmerken (een zogeheten trait-based approach) om een inschatting te maken van potentiële veranderingen in de functie van het macrobenthos binnen sedimentgerelateerde ecosysteemprocessen. Onderwerpen binnen mijn onderzoek zijn: de rol van natuurlijke en door de mens veroorzaakte gradiënten bij het vormen van de functionele structuur van ecologische gemeenschappen; de toepasbaarheid van de trait-based approach om de toestand van het milieu te beoordelen; de effecten van veranderingen in de soortensamenstelling op de functie van het macrobenthos; de effecten van complexiteit op functionele diversiteit; en de invloed van functioneel relevante soorten op het functioneren van ecosystemen. De belangrijkste bevindingen en conclusies van dit proefschrift zijn: 1. Lage kwaliteit van de benthische omgeving, gedreven door organische verrijking, verhindert de vestiging van macrobenthische soorten met specifieke functionele kenmerken. Dit resulteert in samenstellingen met verschillende eigenschappen en verminderde functionele diversiteit. 2. De trait-based approach is een betrouwbare manier om de algemene effecten van organische vervuiling op het macrobenthos te beoordelen. Zowel een analyse van biologische kenmerken als multivariate indices van functionele diversiteit zijn nuttige analytische methoden om de veranderingen in macrobenthische structuur in verschillende gradiënten van organische vervuiling te analyseren, ondanks dat biomassa- en abundantie-analyse kunnen verschillen. 3. Veranderingen in de structuur van de soortensamenstelling gedreven door de vestiging van uitheemse soorten, kan grote veranderingen in de macrobenthische functionele diversiteit veroorzaken. Deze veranderingen kunnen een verhoogd bioturbatiepotentieel veroorzaken en hebben implicaties voor het functioneren van bodemecosystemen. 4. Toegenomen habitatcomplexiteit gedreven door zeegrassen kan sedimentgerelateerde functies bevorderen door de vestiging van ondiep levende macrobenthische bioturbators. 5. Functioneel relevante macrobenthische soorten kunnen het microfytobenthos begunstigen door bioturbatie van het sediment te verhogen of door het sediment te stabiliseren middels het verzwakken van de stroming. 6. Functioneel relevante soorten kunnen functionele cascades bevorderen door de vestiging van organismen die andere functies uitvoeren te begunstigen zoals in de gevallen besproken in dit proefschrift: zeegrassen bevorderen ondiep levende infauna en bemiddelen indirect bioturbatiegerelateerde processen; macrobenthische bioturbatie drijft primaire producenten door de microfytobenthische structuur te beïnvloeden; en mosselbedden bevorderen primaire productie door microfytobenthos te begunstigen. 7. Indicatoren van functionele diversiteit zijn nuttig als verkennend hulpmiddel om de algemene effecten van verstoringen of gradiënten op de macrobenthische structuur te beoordelen. Anderzijds vertegenwoordigen de analyse van biologische kenmerken of de focus op functionele identiteit een betere aanpak om algemene functionele effecten van het macrobenthos op de processen en de structuur van het ecosysteem te beoordelen.

Oyster reefs are declining worldwide, as well as the economic and ecological value of oysters to their respective systems. Numerous restoration efforts have been undertaken in hopes of re-establishing these shellfish populations. This study evaluated a restoration project within the Guana Tolomato Matanzas estuary in northeast Florida, U.S.A., to investigate community structure as well as seasonal patterns in species abundance and diversity of juvenile fish and benthic macrofauna within restored and unrestored intertidal habitats along the Guana Peninsula. The first objective was to determine whether the artificially created reefs provided similar quantity and diversity of benthic macrofauna as adjacent unrestored habitats. The second objective was to specifically characterize resident and transient fish assemblages associated with the artificial reef and adjacent unrestored habitats. Benthic macrofauna were quantified using plastic settlement trays deployed in triplicate at each site and sampled monthly for a year. Community structure differed by habitat, confirmed through an analysis of similarity. High abundances of Petrolisthes armatus on the natural reef sites largely contributed to dissimilarity in community composition between the natural reef and the restored sites. Fish assemblages were quantified using monthly seine and gill nets set adjacent to restored and unrestored intertidal habitats. Diversity was similar between the restored and unrestored sites, however, there was very little species overlap between the two sites. The dominance of post-larval and juvenile spot (Leiostomus xanthurus), anchovies (Anchoa mitchelli and A. hepsetus) and mullet (Mugil sp.) led to high density and low diversity in seine collections during the winter months. Overall, the gill net survey did not show any patterns in fish abundance associated with particular habitats in the area, however this is the first assessment in this region using gill netting. Constructed oyster reefs created immediate habitat for resident species and enhanced habitat value compared to unstructured mud bottom.

Benthic animals have been widely used as health indicators of the marine benthic ecosystems in temperate regions. My PhD thesis mainly aimed to understand the responses of benthic ecosystem in tropical Hong Kong waters to the two management measures - pollution control and trawling ban. My study was based on sediment grab samples collected from 28 stations in three territory-wide surveys conducted in 2001, 2012 and 2015 in Hong Kong waters. I compared the spatial and temporal changes in macrobenthic community structure as well as physical and chemical characteristics of benthic habitats between surveys conducted before and after the pollution control measures in 2001 and 2012, as well as surveys before and after the fishery management measure in 2012 and 2015. The impacts of sewage pollution to benthic ecosystems had been noted in many studies, which included deteriorated water quality and bottom sediment, and disturbed, less diverse macrobenthic community dominated by opportunistic small-sized species. Therefore, sewage treatment and cessation of sewage effluent discharge were expected to lead to notable improvement in benthic habitats, biodiversity and macrobenthic communities; besides, responses of benthic ecosystems to pollution control may be hydrologically varied. In Hong Kong, a series of sewage treatment schemes, e.g. Stage 1 of Harbour Area Treatment Scheme (HATS), Tolo Harbour Action Plan (THAP), Tolo Harbour Effluent Export Scheme (THEES) and a number of sewage treatment works had been conducted in different areas of Hong Kong. Changes in the community structure were noted in the three focal areas with pollution control measures, i.e. Victoria Harbour, Deep Bay and Tolo Harbour; while apparent recoveries were noted inside the Victoria Harbour, the changes in benthic communities inside the Tolo Harbour and Deep Bay could not be attributed to the pollution control measures. Specifically, a decline in nutrient input to the eastern part of Victoria Harbour due to the implementation of HATS might have led to declined sedimentary total organic matter and the disappearance of the opportunistic species, and hence a recovery of benthic ecosystem therein. But in the sheltered Tolo Harbour and Deep Bay, neither improvement in sediment quality nor biodiversity were noted, thus indicating a longer duration is needed for the recovery of benthic ecosystems to take place in these land-locked bays. Degraded marine fishery resources and destruction in marine ecosystems had been noted since the introduction of modern trawling vessels had into Hong Kong since the 1950s and 1960s. Currently, most reports of benthic ecosystem responses to cessation of trawling originate from temperate regions, while it is not well understood for the situation in tropical areas. The territory-wide trawling ban in tropical Hong Kong waters was implemented by the Hong Kong government since December 31, 2012. Although improvement in benthic ecosystems was anticipated after the ban, it was unknown when this would happen and how different parts of the Hong Kong waters would respond to the trawling ban. My study showed that, around 3 years after the trawling ban, sedimentary organic matter content had increased significantly, and bottom water suspended solid loads had decreased in most of the survey stations, indicating territory-wide improvement in the benthic environment. Moreover, significant increases in richness, abundance and functional diversity of macrobenthos, as well as a more aggregated, fewer but larger station groups of macrobenthic communities were also detected after the trawling ban, indicating rapid recovery of the benthic communities. In conclusion, my study indicates that benthic communities in tropical Hong Kong can be used as bioindicators of environmental changes. Due to their restricted mobility, benthic organisms should be an integral part of the ecosystem monitoring aiming to detect the consequences of management measures to the marine environment. Environmental data including habitat complexity and hydrology are also required to fully understand the spatial and temporal dynamics of benthic ecosystems. Besides, my study has provided two territory-wide baseline data on the biodiversity and macrobenthic community structure in the tropical Hong Kong waters, which will be valuable for detecting future changes in the benthic ecosystems. My benthic ecology studies have resulted in a published paper and a manuscript ready for submission for publication. Besides focusing on benthic ecology, I have conducted taxonomic studies on benthic polychaetes, resulting in two published papers. As good taxonomy is the basis of high-quality data in benthic ecology, the training I received from studying these benthic polychaetes has enhanced my understanding of the biology of benthos, which is also important for my career development. However, since these papers do not fall into the main theme of my thesis, they are included in the thesis as appendixes only.

A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Apesar de sua reconhecida importância em termos de complexidade e biodiversidade, os estuários vêm sofrendo considerável processo de degradação gerado pela ação antrópica. Diversos estudos têm enfatizado o papel do macrobentos como indicador da qualidade ambiental desses ecossistemas, o que tem levado ao desenvolvimento de ferramentas e métodos baseados em seus atributos (abundância, biomassa, composição específica, etc.). Dentre esses, os índices bióticos têm sido preferidos em termos de precisão e de custo-benefício, sendo o AMBI (Índice Biótico Marinho) o mais aplicado, com sucesso, em várias áreas geográficas submetidas a diferentes fontes de impacto. Contudo, poucas informações a respeito da ecologia das comunidades macrobentônicas estão disponíveis para a costa atlântica da América do Sul, estando concentradas nas regiões sudeste e sul do continente. Dessa forma, o presente estudo teve como objetivos descrever a composição e distribuição do macrobentos de áreas estuarinas de Pernambuco, testando o efeito do tamanho da abertura da peneira (1,0mm x 0,5mm) e da profundidade de amostragem (0-10cm x 0-20cm) na descrição das associações da fauna e examinar a eficiência do AMBI na avaliação da qualidade ambiental desses estuários. As coletas ocorreram em Outubro-2007, em 14 pontos situados na costa de Pernambuco, sendo amostrados além do macrobentos, parâmetros físico-químicos de água (salinidade, temperatura, oxigênio dissolvido, amônia) e de sedimento (matéria orgânica, granulometria, potencial redox, nitrogênio-total), além do microfitobentos. Um total de 14.257 indivíduos distribuídos em 78 táxons e com uma biomassa total de 83,64g foram observados. Em geral, as diferenças na retenção das peneiras foram importantes para a abundância total (já que a peneira de 1,0mm reteve apenas 28% dos indivíduos), sendo pouco evidente para a biomassa total (92% da biomassa). Por outro lado, em termos de profundidade de amostragem, o estrato de 0-10cm compreendeu quase todos os indivíduos (94% da abundância total), mas contribuiu apenas com 39% da biomassa total. Foram encontradas apenas relações significativas para o fator peneiras tanto para a diversidade N1 (ANOVA 2-way: F1;13=5,17; p=0,02) quanto para a estrutura das comunidades (ANOSIM 2-way: Rglobal= 0,142; p=0,002). Correlações significativas foram estabelecidas entre as variáveis nitrogênio total (r=0,860; p<0,0001), matéria orgânica (r=0,801; p<0,001) e microfitobentos (r=0,749; p=0,005 and r=0,795; p=0,002, para clorofila-a e feopigmentos, respectivamente) contra a abundância da fauna retida nas peneiras de 1,0mm e de 0,5mm. De modo geral, o macrobentos dos estuários estudados é composto por pequenas espécies (1,0-0,5mm), de modo que o uso da peneira de 0,5mm permite uma interpretação mais precisa dos dados; além disso, para a composição da fauna e abundância, a camada superficial (0-10cm) é claramente mais importante enquanto que, para biomassa, a camada de fundo (10-20cm) deve ser considerada. Para a avaliação da qualidade ambiental, o índice AMBI mostrou que todas as áreas estudadas apresentaram algum nível de distúrbio, variando de 2,395 (pouco poluído, Ariquindá) a 5,236 (fortemente poluído, Capibaribe). Em geral, todas as áreas estiveram dentro dos limites de pouco a moderadamente poluído, devido à grande proporção dos táxons Oligochaeta e Nematoda (espécies tolerantes, grupo ecológico III). O índice provou ser eficiente na detecção da qualidade desses estuários, embora sua aplicação para águas tropicais requeira algumas adaptações na classificação ecológica das espécies

Estuaries are dynamic physical environments. The stability of the sediment-water interface is influenced by sources and rates of sediment delivery and physical reworking of sediments by currents, tides, waves and biology, but effects of disruption of this interface on benthic biology are poorly resolved. For this study, I investigated effects of prevalent gradients in seabed disturbance processes and associated seabed characteristics on estuarine benthic community structure and function in the mesohaline York River, a tributary of Chesapeake Bay, USA. I used a variety of approaches to characterize the seabed, including sediment grain size, sediment water content, maximum depth of 7Be, depth of the oxidized sediment layer, profiles of sediment Eh, physical structure of the sediment, sediment chlorophyll a, and sediment organic content. Differences in magnitude of deposition and subsequent reworking of sediments by physical processes were documented among the five benthic subenvironments sampled (south shoal, secondary channel, main channel flank, main channel, and north shoal). Temporal and spatial variations in spring recruitment were observed among subenvironments sampled weekly for recruits: the south shoal, secondary channel and main channel flank. Total recruitment was greatest in the main channel flank, which experienced the highest sediment deposition, and was limited in the secondary channel, which had the strongest tidal currents. The five benthic subenvironments sampled for patterns of community structure and estimates of secondary production were dominated by estuarine opportunist species. Total abundance was greatest in the north shoal, which experienced minimal deposition and physical reworking of sediment. Biomass and secondary production estimates were driven by presence of deep-dwelling bivalves, and were greatest in subenvironments that experienced deposition. These results suggest that variations in seabed characteristics across relatively small spatial scales can influence estuarine benthic community structure and function. Laboratory experiments were conducted to further elucidate the effect of sediment deposition on estuarine organism survival. Species representing both infaunal and epifaunal taxa ranged from highly susceptible to highly tolerant of burial by sediment. Survival was a function of organism motility, residence depth and perhaps physiological adaptations. Small, shallow-dwelling juveniles of some common estuarine species were highly tolerant of burial.

L’estrazione di gas rappresenta uno dei maggiori fattori di stress antropici presenti in Mar Adriatico, dove si trova un’alta concentrazione di piattaforme. Inoltre le strutture esistenti si stanno avvicinando alla fine della loro vita produttiva e nel corso dei prossimi anni la loro dismissione diventerà inevitabile. Per fornire approfondimenti sugli effetti delle piattaforme sull’ecosistema marino la tesi, che ha considerato un pozzo, una piattaforma a 4-gambe e una monopalo, è stata strutturata in quattro argomenti: - quantità e composizione biochimica della sostanza organica nel sedimento; - abbondanza e biodiversità delle comunità macrobentoniche; - abbondanza, biomassa e biodiversità del popolamento ittico; - dieta di Scorpaena notata e S. porcus. I contenuti sedimentari di clorofilla-a e i feopigmenti sono risultati maggiori all'aumentare della distanza dalla piattaforma, suggerendo che piattaforme con una struttura complessa possono riflettere il comportamento di ecosystem engineering dei coralli che vivono in sedimenti incoerenti. Inoltre è stato evidenziato l'effetto aggregazione delle strutture in esame sulla comunità ittica, registrando abbondanza e biomassa maggiori nei pressi delle strutture e indicando che l'entità dell’attrazione è legata a dimensione, volume e complessità delle strutture. Risultati simili sono emersi per le comunità bentoniche, evidenziando che dimensione e complessità delle strutture hanno diversi effetti sulle comunità bentoniche, influenzando i tempi necessari per raggiungere una nuova comunità diversificata. Infine, i risultati hanno mostrato che le strutture possono offrire rifugio e aumentare la disponibilità di prede per le specie presenti anche se, per le specie studiate, questo è stato dimostrato più chiaramente per S. notata che per S. porcus. Alla luce di questi risultati si suggerisce una valutazione caso per caso delle opzioni di dismissione in Mare Adriatico, per evitare effetti secondari sulla comunità ittica e bentonica.
The extraction of natural gas represents one of the most relevant anthropogenic stressors affecting the Adriatic Sea, due to the high concentration of gas platforms. Moreover, the existing structures are approaching the end of their productive life and over the next years their decommissioning will be inevitable. To provide insights on the effects of offshore platforms on hosting ecosystems the thesis, taking into account a subsea well-site, a 4-leg platform and a 1-leg platform, has been built upon four main tasks: - quantity and biochemical composition of organic matter in the sediment; - abundance and biodiversity of macrobenthic communities; - abundance, biomass and biodiversity of fish assemblages; - diet of Scorpaena notata and S. porcus. The thesis showed higher chlorophyll-a and phaeopigment sedimentary contents at increasing distance from the 4-leg platform suggesting that structures with a complex architecture can mirror the ecosystem engineering behavior of branched corals living in incoherent sediments. Moreover, the results highlighted the aggregation effect of the artificial structures under scrutiny on fish assemblages, with higher abundance and biomass of fish close to the structures. The results evidenced also that the magnitude of the attraction is related to dimension, volume and design of the structures. Similar results emerged for macrobenthic communities, highlighting that dimension and complexity of structures have different effects on benthic communities, affecting amplitude and timing required to reach a new diversified community. Moreover, the results showed that the artificial structures can offer shelter and increase prey availability for the studied species, even if more clearly for S. notata than for S. porcus. In the light of these findings, a case-by-case evaluation of decommissioning options in the Adriatic Sea should be recommended to avoid any secondary effect on the established fish and benthic communities.

Les hydro-écorégions du bassin de la Loire (France) sont établies à partir du relief, du climat de la géologie et de l'hydrogéologie (Wasson et al. , 1993). Elles impliquent des variations des paramètres abiotiques et du macrobenthos. Trente sites naturels (têtes de bassins) ont été sélectionnés comme stations de référence dans six regions-test différentes. Deux composantes chimiques permettent d'établir un gradient régional : la dureté et la contamination par les nitrates. Les stations du Massif Central restent préservées en opposition aux stations des plaines calcaires et du granitique armoricain marquées par l'agriculture intensive et l'élevage. Les stations à forte pente, avec radiers, à fort courant et à substrat grossier sont situées dans le Massif Central tandis que les stations à pente faible, avec mouilles, à faible courant et à substrat fin sont situées en plaine. Le gradient de courant explique en partie les différences régionales faunistiques ; cependant, l'effet régional est dominant sur l'effet pente. Le niveau taxonomique de la famille implique des conséquences en bioindication : seules les stations du Massif Central comportent les taxons polluosensibles (perloidea) systématiquement. Ils sont absents ou rares dans les autres régions du fait de l'impact agricole et de l'environnement physique. Le niveau générique permet d'établir des stratégies écologiques régionales à l'aide des traits. Les communautés algales montrent que la biomasse épilithique est supérieure dans les tables calcaires, environnement plus productif. Les relations trophiques (algues, macrophytes, matières organiques) ne montrent pas de différences régionales et tous les essais sur les groupes fonctionnels alimentaires conduisent à un schema de fonctionnement global sur l'ensemble des régions-test. Les racleurs sont dominants en calcaire. Ces résultats valident pour partie la variabilité naturelle des hydro-écorégions et fournissent des éléments pour la gestion

Cold seeps are areas of high biomass in the deep-sea, the impacts of these food-rich environments upon the sediment community is unknown in the Gulf of Mexico. The structure and function of benthic communities was investigated at food-rich and food-limited sites on the northern Gulf of Mexico continental slope. Cold seeps were richer in macrofauna densities and total sediment respiration, but were poorer in biomass and taxa diversity than normal slope communities. Decreased diversity is seen at most chemosynthetic communities and suggests a competition for resources. The spatial extent of these results at seeps is unknown and may be a localized, bioenhancement effect caused by seeping fluids.

The structure of macrobenthic communities was investigated in carbonate and transitional carbonate-terrigenous sediments of the Southern Gulf of Mexico (Campeche Bank). The aim was to assess the influence of natural disturbance represented by winter storms and river runoff and the putative influence of oil-related activities using a regional approach. At a scale of > 100 km community composition of benthic macroinfauna was characterised as distinct assemblages within the carbonate and transitional sedimentary provinces controlled by natural disturbance. The carbonate assemblage was numerous and diverse influenced by a heterogeneous substratum. Winter storms had a severe impact with mortality probably resulting from abrasion and passive transport causing low values of number of taxa, abundance, biomass and diversity measurements. Conversely, on the transitional shelf a sequence of disturbance from river runoff and winter storms resulted in a general impoverished community due to fine sedimentation and sediment instability. Immediately after the rainy season, values of biological measures were low, but the severity of disturbance was contingent with depth. At a scale of 10s km within the transitional shelf, the combined effect from natural and anthropogenic disturbance caused extremely low values of biological measures within the so called oil exclusion zone. Despite the lack of adequate controls the effects of oil related activities were identified as severe reductions in macroinfauna densities and biomass resulting in a very simple community. Large spatial variability at this scale masks the temporal variation observed in other areas of the Campeche Bank and the relationship between biological measures and indicators of oil activities (Barium, Nickel and oil-hydrocarbons). Finally the increased variability resulting from the influence of oil activities interrupts the natural gradient of macroinfauna patterns across the shelf.

Publicación a texto completo no autorizada por el autor
Se investigó los cambios inducidos por el evento La Niña (LN) 2007 sobre el macrobentos de una estación fija a 32 m de profundidad en Bahía Independencia, Pisco, Ica. Los muestreos se realizaron mensualmente entre noviembre del 2006 y junio del 2008, incluyeron muestras de macrobentos y datos de concentración de oxígeno disuelto y temperatura en el fondo. El enfriamiento del evento LN se extendió 9 meses, de mayo de 2007 a enero de 2008. Sin embargo, el periodo considerado LN oficialmente se extendió desde mayo a diciembre de 2007. La concentración de oxígeno disuelto cerca al fondo del mar tuvo valores de hipoxia (<0,05 mL/L) durante el periodo Pre LN, alcanzando el valor de 1,04 mL/L durante LN; y luego en el periodo denominado Post LN la concentración de oxígeno disminuyó alcanzando valores de hipóxia de 0,21 – 0,37 mL/L. El número de especies, densidad y biomasa en peso seco sin ceniza (PSSC) de la comunidad de macrobentos fueron diferentes entre las fases Pre-LN, LN y Post-LN. Durante LN la densidad del macrobentos alcanzó valores dos a tres veces mayores respecto a lo reportado durante las etapas pre y post-LN. Además, el número de especies y PSSC mostraron un comportamiento similar. Se concluye que los efectos biológicos del evento LN 2007 en Bahía Independencia fueron complejos y modulados por la concentración de oxígeno disuelto, durante la cual se observaron cambios ampliamente positivos en la estructura comunitaria del macrobentos destacando los poliquetos.
Tesis

Fish and macrobenthic invertebrates were sampled in the shallow (< 2.0 m) and deeper waters (> 2.5 m) of the upper Swan Estuary in each season between the winter of 1995 and the autumn of 1997. The diets of four abundant benthic teleosts in this region were also determined in each of those seasons. Further sampling was undertaken prior to, during and after large blooms of dinoflagellates were present in that part of the estuary to determine whether these blooms had a deleterious effect on the fish and macrobenthic faunas. A total of 18351 fish, representing 31 species, was caught by seine netting in the shallow waters of three regions in the upper Swan Estuary. These regions were the upstream and downstream saline regions of the Swan River and the saline region of the Canning River. The most abundant fish species by far in the shallow waters were Engraulis australis and Nematalosa vlaminghi, which collectively contributed 55.6% of the total fish catch. The next seven most abundant teleosts included the benthic and estuarine-spawning species Leptatherina wallacei, Amniataba caudavittata, Pseudogobius olorum and Acanthopagrus butcheri, which were used for the dietary analyses. The most abundant species caught using gill nets in the deeper waters were N. vlaminghi, A. caudavittata and A. butcheri, these species collectively contributing 88.5% to the total fish catch in those waters. The compositions of the ichthyofauna in the shallows of the two Swan River regions differed from that in the Canning River. The number of species, density and biomass in both shallow and deeper waters, were highest in summer and autumn, when salinities were highest, and were lowest in winter, when salinities were lowest. The compositions of the fish fauna in the shallow and deeper waters in summer and autumn also differed from those in winter, a difference that reflected in part the presence of greater numbers of N. vlaminghi and A. caudavittata which spawn and provide 0+ recruits in that area during those two seasons. The 31 species recorded in the shallows of the upper Swan Estuary contained 14 marine species, which contributed oz 11% to the total number of fish caught. Although the number of estuarine-spawning species was the same as that of marine species, i.e. 14, this group made a far greater contribution, i.e. > 69%, to the total abundance of fish. The contribution made to the total abundance of fish by marine species was also lower than that of estuarine-spawning species in the deeper waters, i.e. 10.1 vs 41.2%. The semi-anadromous N. vlaminghi made relatively high contributions to the total numbers in both the shallow (19.6%) and deeper waters (48.6%). Forty two species of macrobenthic invertebrates were collected using an Ekman grab in the shallow and deeper waters of the three regions in the upper Swan Estuary. The bivalve mollusc Arthritica semen contributed 25.6 and 27.7% to the total number of macrobenthic invertebrates in the shallow and deeper waters, respectively. The polychaetes Boccardiella limnicola (16.8%) and Ceratonereis aequisetis (25.2%) also made substantial contributions in the shallow waters, as did a sabellid species (24.6%) in the deeper waters. The number of species and number of individuals of macrobenthic invertebrates were both greater in the shallow than deeper waters. Furthermore, the compositions of the macrobenthic invertebrate fauna in the shallow and deeper waters differed, reflecting the relatively greater abundance of the bivalve mollusc Xenostrobus securis, the nereid polychaete Ceratonereis aequisetis and the spionid polychaete Boccardiella limnicola in the shallows. Although the composition of the invertebrate fauna did not differ between regions and did so only marginally between seasons, it did differ between the two years of the study. The composition of the diets of the two small species L. wallacei and P. olorum, with maximum lengths of 73 and 54 mm, respectively, and the two larger species, A caudavittata and A. butcheri, with maximum lengths of 240 and 415 mm, respectively, were significantly different from each other. This feature is reflected both by the results of classification and ordination and by the very limited prevalence of significant dietary overlap between the diets of the different size classes of these four species. Leptatherina wallacei consumed both epibenthic and benthic crustaceans, including copepods, amphipods and cladocerans, as well as prey found throughout the water column. In contrast, P. olorum ingested mainly diatoms and detritus and, to a lesser extent, epibenthic amphipods and nereid polychaetes, which suggests that this species feeds predominantly on and within the sediment. Amniataba caiidavittata fed on a wide variety of prey, including nereids, eunicids, spionids and a sabellid polychaete, epibenthic crustaceans, detritus and algae. This wide diversity of prey was reflected by far the greatest value for dietary breadth of any species. Acanthopagrus butcheri was the only species that fed mainly on molluscs, with the estuarine mussel Xenostrobus spp., which was mainly X. securis, constituting 46.8% of it's diet by volume. Leptatherina wallacei, P.olorum, A. caudavittata and A. butcheri underwent ontogenetic changes in diet. Furthermore, the dietary breadth of A. butcheri declined progressively with increasing body size as this teleost focused increasingly on Xenostrobus spp. as a food source. The trends exhibited by the density of fish in the shallows and by catch rates of fish in deeper waters in the period prior to and during the bloom of dinoflagellates in the upper Swan Estuary, suggests that either a lowering of oxygen and/or the production of toxins may have had a detrimental influence on the abundance of fish. However, no such trends were observed with the macrobenthic fauna and there was no evidence that the blooms led to a change in the compositions of either the fish or macrobenthic faunas.

Human development has eroded Chesapeake Bay's health, resulting in an increase in the extent and severity of hypoxia (≤2 mg O2 l-1). The Bay's hypoxic zones have an adverse affect on community function and secondary production of macrobenthos. The production of macrobenthos is important as these fauna link energy transfer from primary consumers to epibenthic predators and demersal fish, and serve as the foremost pathway that carbon is recycled out of the sediment. Additionally, bioturbation, an essential macrobenthic function that causes the displacement and mixing of sediment particles, increases the quality of marine sediments. In the marine environment bioturbation is primarily mediated by macrofauna which are susceptible to perturbations in their surrounding environment due to their sedentary life history traits. The effect of hypoxia on macrobenthic production was assessed in Chesapeake Bay and three of its tributaries (Potomac, Rappahannock, and York rivers) from 1996 to 2004. Each year, 25 random samples were collected from each system and macrobenthic production estimated using Edgar's allometric equation. Efforts were then focused on the Rappahannock River, a sub-estuary of Chesapeake Bay known to experience seasonal hypoxia, to assess changes in macrobenthic production and function. During the spring, summer, fall, and following spring of 2007 and 2008, samples were collected each season in each year, and DO concentrations were measured continuously at two sites in 2007 and two in 2008. A benthic observing system (Wormcam) was also deployed in 2009 from early spring to late fall to assess the impact of hypoxia on bioturbation. Wormcam transmitted a time series of in situ images and water quality data in near real-time. Results from the previous projects was used to develop a continuous-time, biomass-based model, including phytoplankton, zooplankton, and macrobenthic state variables. The primary focus aimed at predicting the effect of hypoxia on macrobenthic biomass. Z', a sigmoid relationship between macrobenthic biomass and DO concentration, was derived from macrobenthic data collected from the 2007 and 2008 field experiments. Annual fluctuations in macrobenthic production were significantly correlated with DO. Hypoxia led to a 90% reduction in daily macrobenthic production relative to normoxia, and production at hypoxic sites was composed primarily of smaller, disturbance-related annelids. The reduced production resulted in an annual biomass loss of approximately 7320 to 13,200 metric tons C, which equated to a 6 to 12% annual displacement of the Bay's total macrobenthic productivity due to hypoxia. Macrobenthic production differed across seasons, and sediment reworking rates were significantly higher during normoxia, indicating a change in the functional role of the macrobenthic community. Hypoxia was found to significantly reduce bioturbation through reductions in burrow lengths, burrow rates, and burrowing depth. Although infaunal activity was greatly reduced during hypoxic and near anoxic conditions, some individuals remained active. The biomass-based model was successfully calibrated and verified, using independent data, to accurately predict B annually. Simulation analysis of the DO formulation showed B strongly linked to DO concentration, with fluctuations in biomass significantly correlated with the duration and severity of hypoxia.

Siltation and sediment accumulation is a problem that affects many ports and harbours worldwide. Usually, dredging is the most common technique to handle this issue, but nowadays there is increasing concern about its several effects and impacts to the marine environment, especially referred to benthic communities, so that the need to find sustainable alternatives is becoming a topic of wide interest. One of these possible alternatives is represented by the so-called sand by-passing plants. In this study, the potential ecological effects of a new sand by-passing plant, called ejectors plant, have been investigated through a before-after control-impact design (beyond-BACI). The plant was installed in the proximity of the port inlet of Cervia, a small municipality situated in Emilia-Romagna, on the northern Adriatic coast. For the study, 3 different sampling periods (one before and two after plant installation) and 5 different sampling locations (one impact and four control locations) were established. The analysis has evaluated the sediments organic matter percentages and grain size classes composition, the shell debris weight, the structure of benthic communities and fish assemblages. PCO analysis and DistLM were performed to evaluate similarity between benthic communities and to find taxa and environmental variables most correlated with macrofaunal patterns. Moreover, a literature analysis about impacts of dredging on benthic communities have been performed. All results indicate that in last sampling period, 2nd after plant installation, the two possibly affected areas (sand pickup and deposit areas, respectively) values were more similar to control ones than before, suggesting that the ejectors plant could represent an eco-friendly solution alternative to dredging for harbour siltation problems. This work is part of the LIFE15 MARINAPLAN PLUS project, which had the aim of testing the efficiency and sustainability of the ejectors plant at industrial scale.

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Understanding the composition and distribution of biological communities in landscape or region level, in the face of environmental conditions is a major challenge faced by the scientific community. Understanding these processes provides information on the functioning of ecosystems, facilitating decision-making aimed at conserving biodiversity. Thus, this work consists of two chapters, whose aims are, respectively: (i) assess whether the benthic macroinvertebrate communities in response to environmental factors of tropical estuaries, and (ii) assess whether the beta diversity of macrobenthic communities are structured by turnover (i.e., replacement of species) or nesting (i.e., nested subsets of species). The communities of benthic macroinvertebrates were sampled in two tropical estuaries, the estuary of the Paraíba do Norte River and Mamanguape, in the dry and wet seasons. The estuaries have differences in terms of use and occupation of land in the drainage basin. In each estuary, was previously defined the estuarine gradient being established four subtidal zones. In each area, three collection points were set with 3 sample units each. In the first chapter, in addition to samples of benthic macroinvertebrates subtidal, data were considered regarding the environmental factors measured in each estuary. The persistence of benthic macroinvertebrates, and the variability of environmental factors between seasonal periods and zones of the estuarine gradient was evaluated by the distance of the points from their centroids in the dimensional space. The higher proportions of contributions for each seasonal period and zones of the estuarine gradient were identified by analyzing the percentage of similarity (SIMPER). In the heavily impacted estuary, during the dry season, the environmental factors were more variable and communities of benthic macroinvertebrates were more persistent. In the estuary with lesser degrees of anthropogenic influences, environmental factors were more variable in the wet season, where communities were more persistent. The highest rate of contribution ratios in the estuary with higher anthropogenic influences in both seasonal periods was recorded for Laeonereis gender indicator organically enriched sites. In the estuary with the lowest degree of anthropogenic influence, Polypedilum was the taxa with major contributions of ecosystems, facilitating decision-making aimed at conserving measured in each estuary. The persistence of benthic to both seasonal periods, which is a genre associated with better local environmental quality. In conclusion, the environmental variability boosted the persistence of benthic macroinvertebrate communities in tropical estuaries. For the second chapter, the sample design was designed hierarchically and applied the additive partitioning method of diversity to determine the hierarchy with the highest dissimilarity (beta diversity) in the composition of benthic communities. The general beta diversity was measured by the dissimilarity index of Sorensen and partitioned in turnover and nesting components. The greatest dissimilarity in the composition of the communities occurred between the zones along the estuarine gradient in both seasons (dry = 58.6%; wet = 46.3%). In the estuary with the lowest degree of anthropogenic influence, regardless of the season, benthic macroinvertebrate diversity was generated by turnover. In the heavily impacted estuary, during the dry season, beta diversity was structured by turnover, while in the wet season it was structured by a combination of the two mechanisms. We conclude that the principal mechanism responsible for beta diversity in benthic macroinvertebrate communities of tropical estuaries is turnover (i.e., species substitution). As a general conclusion of the dissertation, the main approaches considered in this study (persistence of communities, additive partitioning and general beta diversity) were important tools for understanding the ecological processes that generate the distribution of benthic macroinvertebrate communities in tropical estuaries. These approaches should be taken into consideration in the development of projects aimed at management of estuarine ecosystems and consequent biodiversity conservation.
Compreender a composição e distribuição das comunidades biológicas em nível de paisagem ou região, frente às condições do ambiente é um dos principais desafios enfrentados pela comunidade cientifica. A compreensão desses processos proporciona a obtenção de informações sobre o funcionamento dos ecossistemas, facilitando a tomada de decisões voltadas à conservação da biodiversidade. Assim, esta dissertação é composta por dois capítulos, cujos objetivos são, respectivamente: (i) avaliar a persistência das comunidades de macroinvertebrados bentônicos em resposta aos fatores ambientais de estuários tropicais, e (ii) avaliar se a diversidade beta das comunidades macrobentônicas são estruturadas por turnover (i.e. substituição de espécies) ou aninhamento (i. e. aninhado subconjunto de espécies). As comunidades de macroinvertebrados bentônicos foram amostradas em dois estuários tropicais, o estuário do Rio Paraíba do Norte e Rio Mamanguape, no período de seca e chuva. Os estuários possuem diferenças em termos de uso e ocupação do solo na bacia de drenagem. Em cada estuário, foi previamente definido o gradiente estuarino, sendo estabelecidas quatro zonas subtidais. Em cada zona, foram definidos 3 pontos de coleta, com 3 unidades amostrais cada. No primeiro capítulo, além das amostras de macroinvertebrados bentônicos subtidais, foram utilizados dados dos fatores ambientais mensurados em cada ponto dos estuários. A persistência da macrofauna bentônica, assim como a variabilidade dos fatores ambientais entre os períodos sazonais e zonas do gradiente estuarino, foi avaliada através da distância dos pontos em relação aos seus centroides no espaço dimensional. Os taxa que apresentaram maiores proporções de contribuições aninhado subconjuntos de espécies). As comunidades de para cada período sazonal e zonas do gradiente estuarino foram identificados através da análise de porcentagem de similaridade (SIMPER). No estuário com maior grau de influência antrópica (Paraíba do Norte), os fatores ambientais foram mais variáveis no período de seca e as comunidades de macroinvertebrados bentônicos foram mais persistentes. No estuário com menor grau de influência antrópica (Mamanguape), os fatores ambientais foram mais variáveis no período de chuva, onde as comunidades foram mais persistentes. A maior proporção de contribuição de taxa no estuário com maior influência antrópica, em ambos os períodos sazonais, foi registrada para o gênero Laeonereis (Polychaeta), indicador de locais organicamente enriquecidos. No estuário com menor influência antrópica, Polypedilum (Diptera) foi o gênero com maior contribuição para ambos os períodos sazonais, sendo este um gênero associado a locais com melhor qualidade ambiental. Em conclusão, a variabilidade ambiental gerou a persistência das comunidades de macroinvertebrados bentônicos em estuários tropicais. Para o segundo capítulo, o desenho amostral foi delineado hierarquicamente e aplicado o método de partição aditiva da diversidade para determinar a escala hierárquica com maior dissimilaridade (diversidade beta) na composição das comunidades bentônicas. A diversidade beta geral foi mensurada através do índice de dissimilaridade de Sore nsen e particionado nos componentes turnover e aninhamento. A maior dissimilaridade na composição das comunidades ocorreu entre as zonas do gradiente estuarino (seca = 58,1%; chuva = 35,3%). No estuário com menor influência antrópica, a diversidade beta das comunidades de macroinvertebrados bentônicos foi gerada por turnover em ambos os períodos sazonais. No estuário mais impactado, a diversidade beta foi estruturada por turnover no período de seca, enquanto que no período de chuva a combinação dos dois mecanismos gerou a diversidade beta. Em conclusão, o principal mecanismo responsável pela diversidade beta das comunidades de macroinvertebrados bentônicos de estuários tropicais foi o turnover. Como conclusão geral da dissertação, as principais abordagens consideradas neste estudo (persistência das comunidades, particionamento aditivo e diversidade beta geral), foram ferramentas relevantes para a compreensão dos processos ecológicos que geram a distribuição das comunidades de macroinvertebrados bentônicos em estuários tropicais. Essas abordagens devem ser levadas em consideração no desenvolvimento de projetos voltados à gestão de ecossistemas estuarinos e consequente conservação da biodiversidade.

Resumo: Uma das características mais marcantes das associações bênticas é a distribuição dos organismos em manchas ao longo do espaço e do tempo. Neste sentido, definir ou reconhecer padrões de distribuição exige o conhecimento da importância relativa das diversas escalas espaciais envolvidas. Este estudo avalia os padrões de distribuição espacial das associações macrobênticas em uma área ao largo da plataforma continental interna do Estado do Paraná (25° 37’ 18’’ S e 48° 23’ 57’’ W), próximo à desembocadura da Baía de Paranaguá, através de um desenho amostral hierarquizado ao longo da isóbata de 10 m. Um delineamento amostral com quatro escalas espaciais de variação foi aplicado em períodos de verão e inverno: 3 setores (escala de 103 m), 3 locais (102), 3 pontos (101) e 6 réplicas (100), totalizando 162 amostras. Em cada ponto foi caracterizado o sedimento e determinados os teores de carbono orgânico total, nitrogênio e fósforo total, clorofila-a e feopigmentos. A significância das variações na densidade dos organismos macrobênticos, nas diferentes escalas espaciais, foi analisada através de uma análise de variância hierárquica (nested ANOVA) com a estimativa dos componentes de variância, em conjunto com análises multivariadas (PERMANOVA, nMDS e BioEnv). As características do fundo e as propriedades geoquímicas dos sedimentos exibiram marcada heterogeneidade espacial. A temperatura e a salinidade de fundo, tanto nas amostragens de verão como nas de inverno, mostraram um marcado padrão sazonal, mas sem alterações consistentes entre pontos, locais e setores, mantendo-se praticamente estáveis. A macrofauna local mostrou-se bastante diversificada e numericamente dominada por poliquetas de pequeno porte, que representaram 87% e 90% do total da macrofauna respectivamente nos períodos de inverno e verão. Crustáceos, bivalves, ofiuróides, sipúnculos, nemertinos, anfioxos e hemicordados ocorreram em menor densidade. A análise hierarquizada dos padrões de distribuição revelou que as associações acrobênticas podem variar em todas as escalas espaciais investigadas. Contudo, a menor escala de investigação foi a que mais contribuiu para os padrões observados. Uma mesma espécie, como é o caso do capitelídeo Mediomastus sp, pode apresentar padrões de distribuição distintos ao longo do tempo. O estudo mostrou que modelos amostrais hierarquizados devem ser de fato aplicados para avaliar a variabilidade temporal das associações bênticas e das propriedades geoquímicas e granulométricas dos sedimentos, condicionadores da distribuição dos animais. Os poliquetas podem ser usados com segurança como um proxy para representação da estrutura das associações macrobênticas locais.

Las variaciones de los parámetros oceanográficos y atmosféricos relacionadas a El Niño Oscilación Sur (ENOS) tienen un impacto sobre las comunidades marinas y terrestres, alterando su distribución y abundancia. En el presente trabajo, se analizó la relación entre los parámetros abióticos locales y remotos, y las respuestas de la comunidad del macrobentos de fondo blando de la Bahía de Ancón a dichos parámetros durante El Niño (EN). Las series de tiempo abióticas locales y remotas, y las biológicas del macrobentos de fondo blando de la Bahía de Ancón corresponden al período de marzo de 1990 a setiembre de 2000, que incluye dos eventos EN. Se demostró que tanto los parámetros abióticos locales como remotos tienen una fuerte influencia sobre la comunidad macrobentónica de la Bahía de Ancón. El incremento de la biomasa, tanto de la comunidad como de las especies, se produce en forma más lenta que el de la densidad. También se concluye que las respuestas de las especies a EN estarían relacionadas a sus características de estrategia r y K. Así, las especies oportunistas (estrategia r), como los poliquetos Paraprionospio pinnata, Owenia collaris, el ofiuroideo Ophiactis kröyeri y el forónido Phoronis sp., presentan adelanto y simultaneidad al inicio de los eventos EN; mientras que las especies competidoras (estrategia K), como el nemertino indet. 1, el bivalvo Pitar catharius, el poliqueto Leitoscoloplos chilensis, y el decápodo Pinnixa valdiviensis, presentan retardos a los eventos EN.
--- The variations of the oceanographic and atmospheric parameters related to El Niño Southern Oscillation (ENSO) have an impact on the marine and terrestrial communities, changing their distribution and abundance. The relationship between the local and remote abiotic parameters, and the responses of the soft-bottom macrobenthic community of Ancon Bay to these parameters during EN, was analysed. The local and remote abiotic time series and also the biological time series of the macrobenthos of Ancon Bay belong to the period March, 1990 to September, 2000, which includes two El Niño. The strong influence of both, local and remote abiotic parameters, on the macrobenthic community of Ancon Bay was demonstrated. The increase of the biomass of both, the community and the species, was slower than that of the density. It was also concluded that the responses of the species to EN would be related to their r- and K-strategist characteristics. The opportunists (r-strategist), such the polychaetes Paraprionospio pinnata, Owenia collaris, the ophiuroid Ophiactis kröyeri and the phoronid Phoronis sp., are earlier or simultaneous to the onset of EN events; on the other hand, the competitors (K-strategist), such the nemertine undet. 1, the bivalve Pitar catharius, the polychaete Leitoscoloplos chilensis and the decapod Pinnixa valdiviensis are delayed to EN events.
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