Dissertations / Theses on the topic 'Benthic invertebrate community'

I investigated the role of land use in structuring benthic invertebrate assemblages in agricultural streams in the French Broad River drainage in western North Carolina. I sampled six agricultural streams (3 with cleared headwaters and 3 with forested headwaters) at three points along a gradient (headwaters, a midpoint, and a downstream site). At each site, I measured a variety of physico-chemical parameters, including temperature, chlorophyll a, discharge, nutrients, and suspended solids. Invertebrates were sampled at all sites in October 1996 and April 1997. Riparian vegetation was assessed for each site at mutiple spatial scales using GIS data from the 1950s, 1970s, and 1990s. Forested agricultural (FA) streams had more riparian vegetation than cleared agricultural (CA) streams in both the 1950s and the 1970s. Cleared agricultural streams had less organic matter, more primary production, higher nitrates, and warmer temperatures than FA streams. Total and EPT taxa richness was greater in FA streams. Pollution-sensitive Plecoptera were relatively more abundant in FA streams, while tolerant Diptera were more abundant in CA streams. High diversity and Plecoptera abundance was related to high habitat quality, more riparian vegetation, low nitrates, and low summer temperatures. Higher invertebrate diversity was related to the land use 25-50 years as well as the current land use (forested, moderate agriculture, or heavy cattle impact). These results indicate a long-term legacy of agricultural influences on stream invertebrate assemblages.
Master of Science

In the first chapter of this dissertation, I explore the role of shared evolutionary history in determining predation preferences of a suite of three generalist muricid whelks preying on oysters and mussels. Various theories such as the enemy release and novel weapons hypotheses predict how evolutionary novelty will affect predator-prey interactions, but it is not clear how applicable these theories are to interactions between generalist predators and familiar prey types. In addition to determining whether the one native and two invasive whelks preferred to consume evolutionarily familiar or novel oysters and mussels, I determined the optimality of each prey species via metrics such as food reward, ease of predation (shell thickness), and food:handling time ratios. By explicitly asking if predation hierarchies mirrored optimality, I was able to determine whether evolutionary constraints were preventing the whelks from consuming prey that were more optimal.

In the second chapter of the dissertation, I asked whether there had been post-invasive changes in predation preferences for one of the invasive whelks used in the first chapter, the Eastern oyster drill Urosalpinx cinerea. The results of this study, which indicate that even highly generalist invasive predators consuming a familiar prey type can experience post-invasion changes in naïveté and predation preference strength, serve as a reminder that a potential or new invader's interactions with and impact on species in the recipient community can be hard to predict.

The third chapter of this dissertation documents the loss of an invasive predator's naïveté towards new species prey in real time, and compares the two prey species' behavioral and morphological responses to both general and specific predation cues. I studied the predator-prey dynamics of the invasive European green crab Carcinus maenas and two species of snails, both of which are invasive on the Pacific coast of North America: the Eastern mud snail Ilyanassa obsoleta and the Asian hornsnail Batillaria attramentaria.The results of this research lead me to conclude that, as with the results of Chapter 2, even generalist predators are capable of losing naïveté to new prey and of changing prey preferences following relatively short exposure to new prey. In addition, this research indicates that between species that do not share an evolutionary history, CEs may be very quick to develop, while NCEs that are induced by predator cues may not be like NCEs between evolutionarily familiar species, and may augment the CEs. (Abstract shortened by UMI.)

Traditionally, hypoxia has been defined as the situation where DO levels have fallen below 2.0 mg O2 L-1, but increasing evidence suggests that this low level of DO is inadequate to describe the onset of hypoxia impacts for many organisms. Consequently, there is a need for a greater understanding of how ‘moderate’ alterations in DO levels will affect ecosystem processes and functionality, specifically through behavioural and physiological alterations at the organism and community level. This thesis reports on mesocosm experiments which were conducted to examine the effects of moderate ( > 3.0 mg O2 L-1) hypoxia on firstly, a key ecosystem engineer, the brittlestar Amphiura filiformis, and secondly, on the Station L4 infaunal macrobenthic community. Station L4 is a longstanding marine biodiversity and MSFD reference site and forms part of the Western Channel Observatory. At the organism level, short-term (14 d) exposure to moderate hypoxia significantly reduced oxygen uptake rates, oocyte diameter and oocyte development in A. filiformis. However, these physiological affects occurred irrespective of brittlestar population density. Additionally, moderate hypoxia reduced brittlestar activity, in terms of bioturbation behaviour, consequentially having an effect on ammonium and silicate fluxes. These observations were only detected when brittlestar population density was high. It was concluded that denser populations of A. filiformis may therefore exhibit the greatest changes in behaviour and shifts in ecosystem function as competition for resources and oxygen heightens. The benthic community at Station L4, displayed considerable tolerance to medium-term (6 wk.) exposure to moderate hypoxia, in terms of structure, diversity and bioturbatory behaviour, but these results may be different if exposure was longer or more severe. Alterations in nutrient fluxes were detected, but there was little evidence to suggest these changes were due to macrofaunal behavioural alterations. Additionally, results from this study revealed that bringing complex natural communities into the mesocosm caused a substantial loss of individuals and species, mainly due to translocation and disturbance effects. This important insight into the effects of bringing community assemblages into the mesocosm confirms that even with a loss of diversity, the L4 community maintained functionality and was resilient to alterations in DO. This suggests that the L4 benthic community does not depend on any one specific species for the provision of important ecosystem processes, resulting in considerable functional resilience within the L4 system. However, vulnerability to benthic systems may increase if functionality is dominated by species such as A. filiformis. Consequently, moderate hypoxia may not immediately affect benthic communities in terms of structure and diversity, but the physiological effects on individuals, especially to reproductive development, may cause alterations in the quality and quantity of planktonic propagules supplied by benthic species to the pelagic environment. This could affect benthic community diversity and functionality in the long term if repeated hypoxic events occur.

A study of the aquatic invertebrate communities from two locations (Location 1 and Location 2) within the Matapouri catchment in Northland, New Zealand, was conducted to assess community structure in differing local-scale habitats. Four data collection methods were utilised generating 33,058 adult or larval invertebrates. The sampling methods comprised benthic kick-sampling, sticky trapping, light trapping, and emergence trapping. For the sticky trapping and light trapping, sampling was carried out at three different sites (Sites 1–3) within each location. The sites were situated within three habitat types; native forest, native forest-fringe, and raupo wetland. Emergence trapping also commenced within the three sites, at both locations, but was discontinued after two months, due to the equipment being destroyed by consecutive flooding events (method described in Appendix 1). Benthic sampling was carried out within the Forest and Forest-fringe habitats. Benthic sampling, sticky trapping, and light trapping were carried out following a monthly schedule between June and November 2005. Conductivity, pH, and water temperature measurements were taken concurrently with benthic sampling on a monthly basis, while water velocity and substrate measurements were taken once to assist in habitat characterisation. Overall, 71 taxa were recorded by benthic sampling over the six month period, with a mean of approximately 30 taxa per site per month. In comparison with similar studies elsewhere in New Zealand, a figure of around 30 taxa per sample was high. The benthic macroinvertebrate fauna at all sites was dominated by Trichoptera (19 taxa), Diptera (16 taxa) and Ephemeroptera (10 taxa). This pattern of diversity is similar to that reported in other New Zealand studies. However, in contrast to previous studies, the leptophlebiid mayfly genus Deleatidium was not numerically dominant over the rest of the community, and other leptophlebiid genera (Acanthophlebia, Atalophlebioides, Mauiulus and Zephlebia) were equally represented, possibly reflecting niche partitioning between the groups. The genus Nesameletus was not recorded at any site, despite being one of the core mayfly species in New Zealand streams. The rare mayfly Isothraulus abditus was recorded at one of the forest locations. There are no published records of this species from Northland. Although acknowledged as another of the core New Zealand benthic taxa, the hydropsychid caddisfly Aoteapsyche was not recorded during the study. However, another hydropsychid, Orthopsyche, was commonly recorded, and these may be filling a similar niche to the Aoteapsyche genus. In contrast to the Trichoptera, Diptera, and Ephemeroptera, the Plecoptera fauna was relatively depauperate, probably reflecting the warmer climate of the region and lack of temperature-buffered spring-fed streams. Surprisingly, Zelandobius, a core New Zealand genus, was absent but is regularly recorded in Northland. A species of conservation interest, Spaniocercoides watti, currently recognised as a Northland endemic, was recorded in low numbers. There were no apparent trends in diversity or abundance of benthic invertebrates over time. Also, there were no significant differences in species diversity between the two locations. However, in many cases, taxa were more abundant at Location 2. This may have been due to steeper gradients at Location 2, and the consequent effects on substrate size and streambed stability, as all other physical factors appeared similar between locations. Although several significant differences of individual benthic taxa were recorded, no broad effect of habitat (sites) on species diversity was observable. However, at Location 2, abundances were significantly higher at Site 3 (Forest) compared to Site 2 (Forest-fringe). The reasons were uncertain, but may be attributed to higher retention of allochthonous organic materials, trapped by in-stream cover and larger substrates. Investigations of adult stages by sticky traps supported benthic results recording community compositions and abundances dominated by Trichoptera and Diptera. Plecoptera were poorly represented. Location 2 recorded higher abundances of taxa, particularly Ephemeroptera and Plecoptera. Investigations of adult stages by light traps however did not produce any statistically significant differences in abundances between sites, between locations, or between sites across locations, and it is believed to be due to limited sampling replication combined with some biases of light trapping. This study indicates that the aquatic invertebrate community at Matapouri is diverse but also reasonably representative. Several rare or uncommon insects inhabit the catchment. It is therefore important that Iwi and the local Landcare Group, who invited and supported this research, together with the Department of Conservation, continue their efforts in protecting these areas. The resident fauna have the capacity to restock areas downstream, which are intended to be improved and restored through sediment control and riparian management.

Groundwater is an important resource for drinking water, agriculture, and industry, but it also plays an essential role in supporting the functioning of freshwater ecosystems and providing habitat for a number of rare species. However, despite its importance, groundwater ecology often receives little attention in environmental legislation or research. This study aims to improve our understanding of the organisms living in groundwater-dependent habitats and the influence of environmental conditions on their distribution. Invertebrate communities occurring in the benthic, hyporheic and phreatic habitats were surveyed at twelve sites over four years across the Stour Chalk Block, a lowland catchment in southern England. A diverse range of stygoxenes, stygophiles and stygobionts, including the first record of Gammarus fossarum in the British Isles, were identified using morphological and molecular techniques. The results indicate that under normal conditions, each habitat provided differing environmental conditions which supported a distinctive invertebrate community. While the community recorded in the benthic habitat was characterised by a diverse assemblage of surface water species typical of Chalk streams, the phreatic community comprised a small number of exclusively crustacean stygofauna (such as Niphargus kochianus and Crangonyx subterraneus) and the hyporheic habitat supported a mixture of surface and groundwater species. Surprisingly, the results indicate that some species, such as Agapetus fuscipes (normally considered a surface water taxon), move into the hyporheic habitat in a predictable, seasonal pattern, potentially in response to grazing opportunities. However, the results collected during the high and low flow events which occurred during this study also show the widespread movement of multiple species (such as Gammarus pulex and Niphargus fontanus) between habitats in response to environmental disturbance. Collectively, these results reflect the movement of fauna longitudinally, laterally and vertically over time throughout the catchment, as though along a continuum rather than between three separate habitats. This suggests that our conceptualisation of lotic functioning should be expanded to better integrate the contribution from groundwater. The approach taken by this study provides a greater understanding of the full diversity of aquatic invertebrates within this catchment and the way in which their distribution fluctuates across habitats. This study is one of the first to concurrently assess invertebrate distribution across the benthic, hyporheic and phreatic habitats; in addition, the relatively frequent and long-term sampling approach also facilitated a more detailed temporal assessment of these communities. A greater understanding of the distribution and requirements of the fauna inhabiting groundwater-dependent habitats, and their response to environmental change is essential for the conservation of these species and management of lotic ecosystems.

The aim of this work is to analyze if a change in the benthic community can be detected two years after a restoration of a small stream. The samples were taken in a small stream at Tinnerö Eklandskap just south of Linköping. In addition to the restored area, two reference sites upstream and downstream of the restored area were sampled to compare to the restored site. The method used for sampling of benthic fauna in the stream was kick sampling. ASPT, Berger-Parker and Renkonen-indices were used to find out if there was any difference between the reference areas and the restored area. In addition to indices, rank-abundance curves and species lists were made to see if there was any trend difference between the different areas. The only index that showed a difference between the different areas was Berger-Parker diversity index. The reason why there were no greater differences between the areas may be due to the fact that two years is too short to allow time for the benthos to re-colonize the restored area.

Dendritic stream networks are inherently spatially and hierarchically structured, but the effects of this structure on stream communities are largely unknown. My aim was to investigate spatial patterns in stream networks using extensive spatial sampling of both adult and benthic macroinvertebrates in four stream networks on the West Coast of the South Island, New Zealand. Using spatial modelling and analyses, I answered questions about appropriate spatial measurements to capture ecological processes in stream networks, metacommunity processes at different scales in space and time, and how local and regional processes interact to structure metacommunities in stream networks. Spatial eigenfunction analyses showed that distance measures that explained most variance in stream macroinvertebrate communities were stream distance and weighted stream distance measures. They performed better than Euclidean distance to measure spatial structure that is ecologically relevant to stream network communities. The spatial pattern of benthic stream macroinvertebrates was stable over time, whereas community composition changed significantly, as shown by space-time interactions modelled by MANOVA-like redundancy analysis. Thus, spatial processes structuring stream metacommunities remained constant, in agreement with neutral model predictions. Network-scale properties, particularly flood disturbances, influenced the relative importance of spatial and environmental variation in stream network metacommunities. Additionally, quantile regression indicated that three key variables, habitat size, isolation and local habitat conditions, jointly limited community structure in stream networks, providing empirical support for both island biogeography and metacommunity theories. My study indicated that spatial structuring has an important influence on stream macroinvertebrate communities. The results contribute to broader ecological theory and understanding of community assembly by relating empirical results to theoretical predictions. In particular, they advance understanding of spatial processes in stream networks. The research also highlights a number of new methods, which were successfully applied to stream systems to elucidate complex spatial patterns.

Most of the seafloor is soft sediment, so hard substrata are isolated and island-like. In this dissertation, I explore how species distribution patterns on isolated marine hard substrata resemble terrestrial island communities, drawing on classical island biogeography theory and assembly rules, and describe how benthic invertebrate communities assemble in these island-like habitats. Higher species richness occurred on larger substrata (dropstones and shipwrecks), paralleling terrestrial island communities. However, while larger islands have greater habitat diversity and primary productivity, marine hard substrata are simpler habitats. Greater elevation in the benthic boundary layer may expose fauna to faster current, higher food supply and larval flux. Substrata located closer together had more similar communities, another pattern that resembles terrestrial islands. Dropstone fauna had a clumped distribution, indicating that larvae may disperse among substrata located close together, resulting in similar communities. In Svalbard fjords, benthic megafaunal communities were significantly different between Arctic- and Atlantic-influenced fjords. Depth and temperature had the greatest influence, with the highest diversity occurring in cold Rijpfjorden and on the north Svalbard shelf. Recruitment in Svalbard fjords was spatially and temporally variable, with lower recruitment in Rijpfjorden than in Atlantic-influenced fjords and lower recruitment at greater depth. Most of the recruits in Svalbard fjords were fast-growing, poor-competitive opportunists. On shipwrecks, communities showed two mechanisms of colonization: mobile fauna with long-dispersing planktotrophic larvae, and encrusting fauna with lecithotrophic larvae. Encrusting species reproduce asexually to cover the wreck surface, and philopatry may build up dense populations, leading to uneven communities. On terrestrial islands, non-random co-occurrence is attributed to interspecific competition, but for marine substrata, there may not be a relationship. Fauna were distributed randomly on settlement plates in Svalbard fjords, even when interspecific competition was observed. On dropstones, some morphotypes co-occurred non-randomly in the absence of overgrowth competition. Non-random co-occurrence on isolated marine hard substrata may be a result of restricted larval dispersal (for pairs co-occurring less than by chance) or epibiontism (for pairs co-occurring more often than by chance). While species distribution patterns on island-like marine hard substrata resemble terrestrial islands, the mechanisms are not necessarily the same.

Most of the seafloor is soft sediment, so hard substrata are isolated and island-like. In this dissertation, I explore how species distribution patterns on isolated marine hard substrata resemble terrestrial island communities, drawing on classical island biogeography theory and assembly rules, and describe how benthic invertebrate communities assemble in these island-like habitats. Higher species richness occurred on larger substrata (dropstones and shipwrecks), paralleling terrestrial island communities. However, while larger islands have greater habitat diversity and primary productivity, marine hard substrata are simpler habitats. Greater elevation in the benthic boundary layer may expose fauna to faster current, higher food supply and larval flux. Substrata located closer together had more similar communities, another pattern that resembles terrestrial islands. Dropstone fauna had a clumped distribution, indicating that larvae may disperse among substrata located close together, resulting in similar communities. In Svalbard fjords, benthic megafaunal communities were significantly different between Arctic- and Atlantic-influenced fjords. Depth and temperature had the greatest influence, with the highest diversity occurring in cold Rijpfjorden and on the north Svalbard shelf. Recruitment in Svalbard fjords was spatially and temporally variable, with lower recruitment in Rijpfjorden than in Atlantic-influenced fjords and lower recruitment at greater depth. Most of the recruits in Svalbard fjords were fast-growing, poor-competitive opportunists. On shipwrecks, communities showed two mechanisms of colonization: mobile fauna with long-dispersing planktotrophic larvae, and encrusting fauna with lecithotrophic larvae. Encrusting species reproduce asexually to cover the wreck surface, and philopatry may build up dense populations, leading to uneven communities. On terrestrial islands, non-random co-occurrence is attributed to interspecific competition, but for marine substrata, there may not be a relationship. Fauna were distributed randomly on settlement plates in Svalbard fjords, even when interspecific competition was observed. On dropstones, some morphotypes co-occurred non-randomly in the absence of overgrowth competition. Non-random co-occurrence on isolated marine hard substrata may be a result of restricted larval dispersal (for pairs co-occurring less than by chance) or epibiontism (for pairs co-occurring more often than by chance). While species distribution patterns on island-like marine hard substrata resemble terrestrial islands, the mechanisms are not necessarily the same.

Coral reefs are being negatively impacted by various causes worldwide, and direct intervention is often warranted following disturbance to restore or replace lost ecosystem structure and function. An experimental coral reef restoration study involving standardized artificial reef modules (ReefballsTM) was conducted in Mexico’s Yucatan Peninsula in the towns of Puerto Morelos and Akumal. The purpose was to explore the use of artificial structure for restoration and mitigation applications in a highly diverse and dynamic Caribbean coral reef environment by applying and evaluating the performance of select experimental treatments hypothesized to accelerate development of the associated biota. The first treatment consisted of invertebrate enhancing artificial substrate padding material, which provided structurally complex refuge space for mobile epifaunal/infaunal invertebrates and other benthic organisms. The second treatment consisted of coral transplants, intended to provide additional structural complexity and kick-start development of stony coral populations. The third treatment consisted of settlement plates which were intended to provide data on coral recruitment and survival rates. Multiple hypotheses relating to the interactions between experimental treatments and the resulting macroalgal, non-coral invertebrate, stony coral, and coral reef fish assemblages were examined, and comparisons were made between natural and artificial substrates. In Puerto Morelos there were 40 modules; 10 controls and 10 of each of 3 treatments: substrate pads, coral transplants, and settlement plates. In Akumal there were 12 modules; 6 controls and 3 of each of 2 treatments: substrate pads and settlement plates. Following module deployment, 6 biannual monitoring trips were made over the course of three years to assess the development of the biota, with a final 7th trip made six years post-deployment. Divers conducted non-destructive visual surveys to evaluate total abundance, species richness, size class distribution, and assemblage structure of coral reef fishes. Other monitoring work included coral recruit surveys, mobile epifaunal invertebrate collections from substrate pads, and digital imaging of coral transplants, natural reef reference corals, and benthic quadrat areas. Hurricane Dean compromised the Akumal study site during the first year of the study, but Puerto Morelos was unaffected. There the modules developed biotic assemblages that differed from what was found on the natural reef, and the data suggests that the substrate pads may have had an effect on the development of faunal assemblages. Lobophora variegata macroaglae and Desmapsamma anchorata sponge were the major contributors to benthic community composition, and both had significantly greater coverage on the substrate pads treatment modules. Lobophora grew rapidly and peaked within the first year, while sponges increased steadily throughout the first three years of the study, surpassing the coverage of macroalgae before the end of the second year, much to the detriment of coral transplants and many coral recruits. By the end of the study, over 75% of the transplants were overgrown by D. anchorata, and density of new coral recruits on the Pads treatment modules was lower than the other treatments and controls. Coral recruitment was dominated by Porites astreoides on all treatments and controls, and the number of corals increased steadily throughout the study. The controls had consistently greater numbers of corals than the treatments, as well as lower percent coverage of macroalgae and sponges. Total abundance and species richness of reef fishes was generally unaffected by the treatments. However, at the family and species level, several differences were detected, particularly for the substrate pads treatment and to a lesser extent for the coral transplants treatment. For future restoration or mitigation efforts utilizing similar or identical treatments to artificial substrates, this study suggests that, in the absence of routine maintenance, greater success may be achieved after waiting several years post-deployment for the initial wave of unchecked growth by benthic organisms (i.e., macroalgae and sponges) to reach a balance point before a large investment of resources is devoted to coral transplanting. Further recommendations include routine monthly or quarterly on-site maintenance to enhance transplant survival, as well as a longer monitoring window to assess community development in response to experimental treatments. The results of this study suggest that the experimental treatments did indeed have an effect on the biota, but whether or not the effect was beneficial largely depends upon perspective. The Pads treatment in particular had the greatest effect on both reef fish and benthic community development, however, it was not beneficial for stony coral recruitment. Additional research is needed to fully understand the long-term performance and effects of the padding material on biotic assemblage development for future restoration or mitigation projects.

碩士
國立中興大學
生命科學系所
102
Algal reefs located in Taoyuan have the largest cover area in Taiwan. Invertebrates are important in coastal ecosystems, they are foods for high consumers and affect high consumers’ distribution and abundance. There were four sampling area along the coast of Taoyuan, including Sinwu river (SW), Datan power plant (DT), Guanyin beach (GY) and Shulinzih (SL). In this four sampling area, two transects of each area were surveyed for the distribution and abundance of epifauna in four seasons of a whole year from September 2012 to June 2013. In addition, a piece of reef was sampled at different elevation sites (high, medium and low) along the transects in each area for the survey of infauna. In total, 64 taxa of invertebrate were identified during the study period. Total abundance of epifauna ranged from 0-73 ind. m-2, and that of infauna ranged from 933-8866 ind. m-2. The highest abundance of epifauna was observed at SW, but the highest taxon number was found at DT. The most dominant species of epifauna was gastropods and the most dominant species of infauna was polychaetes. Higher abundance of malacostracans was found in DT. Polyplacophoras abundance was higher in the spring of DT and SW. The highest abundance and taxon number of infauna was at DT. However, the lowest abundance and taxon number of benthic invertebrates was observed at SL. The community composition was different from those of other sampling area. There were no significant differences of community composition between gravel beach and algal reefs. Our results showed the algal reefs at SL was heavily polluted and those at GY was disturbed by frequent sedimentation. It is clear that pollution and sedimentation is the major influencing factors on the benthic invertebrates inhabiting algal reefs along the coast of Taoyuan.

Iron mining began in Wawa, Ontario in the late 1800s and ceased in 1998. The sintering process of iron pyrite produced sulfur dioxide which led to the acidification of nearby lakes. Benthic macroinvertebrate samples were collected from lakes along a gradient of historical impairment in Wawa to examine the extent to which the benthos of the lakes would separate along the historical impairment gradient. The results show that the lakes are not separated along a gradient of impairment, and acid-intolerant taxa were collected in previously acidified lakes. There was no ameliorative intervention to combat the historical acidification and the observed recovery of water chemistry and benthos is entirely due to natural ecosystem processes. The two sampling methods (littoral kick sampling using a D-net and Hester-Dendy substrates) used to sample the benthos in these lakes can lead to substantial differences in the taxa collected.

碩士
國立中山大學
海洋環境及工程學系研究所
99
The objectives of this study are to investigate the biodiversity in different unit of treatment systems, and to detect the function in a salt water type of constructed wetland. We investigated the benthic invertebrate community in different stage from 2010 July to 2011 May, while the parameters of TKN, NH3-N, organic nitrogen, TP, TOC and particle size were measured in the sediments of each sampling site at the same time in the wetland system. The results show that concentrations of organic matter and nutrients in the sediments were increased with time monthly. In May of 2010, the concentration of NH3-N were found the highest one(ANOVA, p<0.05). The particle size in sampling site 1 were the highest (ANOVA, p<0.05), while in November of 2010 all sampling sites were found exhibiting significantly different with other months (ANOVA, p<0.05). Further more, for the diversity of benthic invertebrate, we found that the parameter of the temperature was strongly negatively related to the species diversity, species abundance and species evenness, respectively (r=-387[H’]；-533[d]；-438[J’] ). The species diversity was increased with organic nitrogen concentrations in the sediments (r=0.492[TKN]；0.408[NH3-N]；0.493[org-N]), and were negatively related to the parameters of DO and particle size(r=-0.402[Particle size]；-0.287[DO] ). In addition, PCA shows that the parameters of particle size、org-N、NH3-N、TKN and TOC were all important factors. Generally, it was concluded that the constructed systems, which is functioned of wetland was wastewater treatment mainly, exhibit no significant function in biodiversity.

Marine ecosystems are increasingly being subject to human impact from diverse recreational and commercial activities, not necessarily restricted to those of a marine nature. This has significant implications for biodiversity. The large dog cockle, Tucetona laticostata, once occurred live in Rangitoto Channel, Hauraki Gulf, although this species no longer appears to occur there, most likely as a consequence of repeated dredging and channel excavation and continued siltation. Tucetona laticostata still occurs in a few isolated pockets of sea bed throughout Hauraki Gulf, particularly off Otata Island, part of the Noises complex of islands, where it resides partially buried in shell and rock gravels in shallow water (to 15 metres depth). The shells of T. laticostata collect in large post-mortem deposits in an area ramping from the sea bed off southwestern Otata Island. These mounds differ significantly in structural complexity from those of adjacent, extensively fragmented shell and rock gravels. Using the mounds of T. laticostata shell as a proxy for structural complexity, in order to appraise the effect of complexity on benthic-invertebrate diversity, the sea bed off southwestern Otata Island was sampled quarterly at two depths and in both T. laticostata shell mounds and adjacent extensively fragmented shell and rock gravels. These data were complemented with those from additional surveys around Otata Island, and off eastern Motutapu Island to determine the distribution and composition of benthic-invertebrate community assemblages throughout the region, and from concurrent surveys throughout the Waitemata Harbour and inner Hauraki Gulf to determine the current distribution of T. laticostata in this region. The number of benthic invertebrate species and individuals within T. laticostata habitat almost always was higher than that occurring within extensively fragmented shell- and rock gravel habitat, with densities to 142,385 individuals m-2 encountered. Temporal and spatial variations in benthic community structure also are reported for the two habitats, T. laticostata-based shells and extensively fragmented shell- and rock gravels. The numbers of species were higher amongst samples collected off the southwestern and eastern sides of Otata Island than elsewhere around this island, or of eastern Motutapu Island. Of the 351 species reported from all Otata and Motutapu Island samples combined, 73% of them occurred off southwestern Otata Island, 30% of which were found exclusively within T. laticostata shell habitat, and 10.5% within extensively fragmented shell and rock gravel habitat. The sea bed off southwestern Otata Island is regularly, seasonally dredged by recreational scallop fishers, in addition to being a popular small-vessel anchorage site. Both of these activities, dredging and anchorage, stand to reduce substratum complexity by fragmentation and dispersal of the valves of T. laticostata. Given the unique benthic invertebrates reported from T. laticostata shell deposits reported from southwestern Otata Island, any activity that damages the shells of this species, regardless of whether they are live or dead, is likely to result in loss of biodiversity. Admittedly, many of species identified as major contributors to differences in benthic invertebrate assemblages between T. laticostata shell-based habitats and those of extensively fragmented shell and rock gravels are not particularly charismatic or large, but each likely plays a role in local food webs and/or sediment and water column chemistry. It was not the intention of this research to determine the effects of anthropogenic disturbances like dredging or vessel anchorage on benthic-invertebrate communities off southwestern Otata Island. However, given the reported differences in species diversity within the structurally complex substratum provided by T. laticostata, conservation of biogenic reef-forming species like it might be a prudent, precautionary measure to take.

Dissertação de mestrado em Ecologia, apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
The main aim of this study was to investigate the functional composition of the subtidal benthic invertebrate communities of the Mondego estuary and thus contributing to a better understanding of the response of these communities to the pressures within this type of ecosystem. We characterized the environmental conditions and investigated the spatial and seasonal distribution of the communities by means of traditional taxonomic analysis and BTA. Moreover, we investigated the relation between taxonomic and functional composition by comparing indices of taxonomic and functional diversity. Traditional taxonomic analysis highlighted spatial and seasonal variations of community composition (i.e., a general reduction of species richness, Shannon-Wiener diversity, and an increase of species density towards the upper parts of the estuary). BTA analysis highlighted the functional characteristics of the benthic community within the estuary and common features across species that have appeared or disappeared among seasons. Furthermore, BTA allowed to investigate interactions among traits (i.e., the strong influence of the trait ‘salinity preference’) and was used to calculate functional diversity (FD). Indices of taxonomic diversity (Shannon-Wiener index) and FD (RQE index) allowed to explore the relation between taxonomic and functional composition. This relation might potentially have indicated that the community at the upper most reaches of the estuary exhibits lower functional redundancy than the downstream assemblages. This study represents one of the first attempts to investigate the functional composition of the benthic invertebrate community in an estuarine environment by means of BTA. BTA in addition to traditional taxonomic analysis provided a more comprehensive understanding of the functioning of this ecosystem. Therefore, the inclusion of BTA is highly recommendable for estuarine ecological studies, but more research is needed to improve its effectiveness regarding the following issues: (i) the set of selected biological traits should be optimized towards the inclusion of more relevant ecological information. This objective can be achieved by improving the knowledge on single species biological traits, which is at present still fragmentary; (ii) the biological traits of species should be linked with the services these environments provide. This traitservice association will be a crucial step in ecosystem service monitoring and management.

Activities associated with agricultural land use intensification, one of the primary sources of anthropogenic stress to aquatic ecosystems, degrade freshwater stream health and present a significant challenge to resource managers in terms of monitoring and remediation. Biomonitoring of benthic macroinvertebrates, a common method of measuring the impact of anthropogenic stress on freshwater stream health, has been used to characterize the impact of agricultural activities. However, in order for this technique to be useful to resource managers in the protection of freshwater streams from agricultural degradation, reliable methods are needed not only to determine the impact of agricultural stress on benthic macroinvertebrate communities, but also whether agriculture best management practices (BMP's) mitigate those impacts ...