Rozprawy doktorskie na temat „Eutrophication”

Aquatic plants need two essential nutrients for growth: phosphorus and nitrogen. They receive these nutrients through a process known as eutrophication, in which water bodies accumulate plant nutrients. In a healthy lake both nutrients occur in limited amounts, restricting plant growth. However, human factors can dramatically increase the concentration of plant nutrients in water bodies, a phenomenon known as “cultural eutrophication”. The rise in eutrophic events has been attributed to the rapid increase in intensive agricultural practices, industrial activities, and population growth which together have increased nitrogen and phosphorus flows in the environment. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/31125

The process of eutrophication is natural. For many lakes, as they age over centuries, there is a buildup of nutrients, sediment, and plant material, which slowly fill the lake basin. Eventually, the process ends and the basin becomes colonized by terrestrial vegetation. The timing of natural eutrophication is highly variable and depends on the characteristics of the basin, watershed, and climate.

Changes in trophic status are often related to increases or decreases in the allocthonous inputs of nutrients from changes in land use and management practices. Lake and reservoir managers are continually faced with the questions of what to monitor, how to monitor it, and how much change is necessary to be considered significant. This study is a compilation of four manuscripts, addressing one of these questions, using data from six reservoirs in Texas.

This thesis presents predictive models for important variables concerning eutrophication effects in lakes. The keystone is a dynamic phosphorus model based on ordinary differential equations. By calculating mass fluxes of phosphorus into, within and out from a lake, the concentrations of different forms of phosphorus in different compartments of the lake are estimated.

The dynamic phosphorus model is critically tested and several improvements are presented, including two new compartments for colloidal phosphorus, a sub-model for suspended particulate matter (SPM) and new algorithms for lake outflow, water mixing, diffusion, water content and organic content of accumulation sediments are implemented. Predictions with the new version show good agreement against empirical data in five tested lakes.

The sub-model for SPM uses the same driving variables as the basic phosphorus model, so the inclusion of this model as a sub-model does not require any additional variables. The model for SPM may also be used as a separate model giving monthly predictions of suspended particulate matter in two water compartments and one compartment with SPM available for resuspension in ET-sediments.

Empirical data from Lake Erken (Sweden) and Lake Balaton (Hungary) are used to evaluate the variability in settling velocity of SPM. It is found that the variability is substantial and may be accounted for by using a dimensionless moderator for SPM concentration. Empirical data from accumulation area sediments in Lake Erken are used to develop a model for the dynamics of phosphorus sedimentation, burial and diffusion in the sediments. The model is shown to provide reasonable monthly predictions of four functional forms of phosphorus at different sediment depths.

Simulations with the lake phosphorus model using two different climate scenarios indicate that lakes may respond very differently to climate change depending on their physical character. Lake Erken, with a water retention time of 7 years, appears to be much more sensitive than two basins of Lake Mälaren (Sweden) with substantially shorter retention times. The implication would be that in eutrophic lakes with long water retention times, eutrophication problems may become serious if the future becomes warmer. This will be important in contexts of lake management when remedial measures against lake eutrophication have to be taken.

Water quality and ecological integrity of estuaries reflect activities within the entire upstream catchment. Much emphasis has been placed on the response of estuaries to anthropogenic stressors through the use of monitoring programmes. Key to the success of these programmes is the use of indicators as they transform data into useful information. The ultimate aim of this study was to identify eutrophic symptoms in selected estuaries in the Gouritz Water Management Area (WMA) using a multi-metric classification method. The study sites included the permanently open Duiwenhoks, Goukou, Gouritz, and Kaaimans estuaries, as well as the temporarily open/closed Hartenbos, Klein Brak, Great Brak, Gwaing, and Goukamma estuaries. Initially, the “pressure” associated with all the estuaries in the Gouritz WMA was determined (e.g. total daily nutrient loads and changes in river inflow affecting flushing time) using long-term flow and water quality monitoring data provided by the Department of Water Affairs (DWA). Subsequently, the “state” of the selected estuaries was assessed using a variety of indicators, including: inorganic nutrients (~ N and P), phytoplankton, epiphytes and microphytobenthos. Estuaries with longer flushing time suggested greater vulnerability to eutrophication. For example, the Gwaing (281.11 kg DIN d-1; 78.85 kg DIP d-1) and Hartenbos (38.33 kg DIN d-1; 21.51 kg DIP d-1) estuaries generally received the highest daily inorganic nutrient loads. However, at the time of sampling, the Hartenbos Estuary had a longer flushing time (i.e. weeks) compared to the Gwaing Estuary (i.e. couple of days). Field data confirmed the greater vulnerability to eutrophication associated with longer flushing times, as the indicators measured in the Hartenbos Estuary exceeded all the proposed ‘thresholds’ of a eutrophic system (~ overall ‘Poor’ condition). The Great Brak Estuary (~ overall ‘Fair’ condition) provided an interesting example where eutrophic symptoms were only detected when assessing the microalgal primary producers (i.e. high biomass and low diversity). Furthermore, the need to distinguish between naturally and anthropogenically induced symptoms was highlighted. One such scenario was noted in the Kaaimans Estuary, where its natural hydro-morphological characteristics (i.e. steep banks, low river inflow, and deep/narrow channel) led to the possible exaggeration of its overall eutrophic condition, i.e. received a ‘Fair’ rather than ‘Good’ rating, arising from ‘Poor’ ratings for dissolved oxygen and benthic diatom diversity. Overall, this study demonstrated the importance of adopting a holistic approach when assessing the condition and trophic status of estuaries. Studies such as these allow for the detection of vulnerable and degraded systems, which can provide important information with regards to the identification of management priorities.

Many lakes around the world have been exposed to increased nutrient input from anthropogenic sources such as sewage discharge and runoff from fertilised agricultural areas. This has led to eutrophication, manifested as intensified algal blooms, murky waters, oxygen depleted lake bottoms, and alterations of considerable parts of the foodweb. However, many of these lakes have also recovered, due to improved nutrient abatement techniques and to an improved quantitative scientific understanding of eutrophication and its causes. General, predictive models have played a crucial role in the latter development, as they have made it possible to quantitatively assess expected ecosystem changes from various planned actions against eutrophication. The present thesis has been aimed at improving the domain of validity and predictive power of a general, dynamic total phosphorus (TP) model (LakeMab) and to provide the basis for constructing a similar model for total nitrogen (TN). Among the findings in the thesis is that dissolved nitrogen gas is probably always available in excess for nitrogen fixation and nitrogen modelling in eutrophication contexts. Two papers have laid the ground for improved nutrient modelling in calcareous lakes, where sedimentation is particularly pronounced. Static models for predicting concentrations of particulate phosphorus, nitrogen, and organic carbon have been presented that may be incorporated into sedimentation algorithms in dynamic nutrient models. Boundary conditions for various flux algorithms have made it possible to greatly expand the domain of LakeMab for TP. The typical uncertainty of TP concentration values is 17% when predicted with LakeMab, whereas the uncertainty in predictions using older, static models is about twice as high. LakeMab may be very useful for resolving practical issues such as predicting climate-induced eutrophication and drawing up operational guidelines for achieving good water quality as prescribed by, e.g., the European Water Framework Directive.

This study investigates effects of eutrophication on settlement, abundance, mortality and community structure of soleractinian corals on fringing reefs on the west coast of Barbados, W.I. Juvenile abundance was lower, but juvenile size larger, on eutrophic than less eutrophic reefs. The lower abundance results at least in part from a higher juvenile mortality on eutrophic reefs. Algae were more abundant and grazers (Diadema antillarum and herbivorous fish) less abundant on eutrophic reefs. Juvenile community structure on all reefs, and adult community structure on eutrophic reefs, was dominated by type 1 corals (high recruitment, high natural mortality). Type 2 corals (low recruitment, low natural mortality) were common in adult communities on less eutrophic reefs. Settlement of coral recruits on artificial substrates was lower on more eutrophic reefs.

Increased inputs of nutrients to estuaries and coastal waters can cause undesirable effects associated with eutrophication, including nuisance and toxic algal blooms, reduced amenity value, changes in species composition, bottom anoxia and fish kills. The main sources of nutrients to estuaries are river runoff, sewage discharges, atmospheric inputs and possibly submarine groundwater discharges. For the UK, estuarine eutrophication has been shown to occur in at least 16 estuaries (including the Taw in North Devon). Consequently, these systems have been designated as '(Potential) Problem Area' under the OSPAR Common Procedure for the Identification of Eutrophication and also as a 'Eutrophic Water' under the EU's Nitrates Directive and I or a 'Sensitive Area (Eutrophic)' under the Urban Wastewater Treatment Directive or both. Significant reductions in N and P inputs have been realized following application of the EU's Urban Waste Water Treatment Directive. Atmospheric NOx and NHx emissions have also decreased and are expected to decrease further as implementation of existing legislation continues and new controls are introduced for activities such as shipping. The Nitrates Directive was introduced to tackle N discharges from agriculture but little change in N loads to estuaries has been recorded. Using the Taw Estuary as an example, data routinely collected by the Environment Agency for England and Wales (EA) over the period 1990-2004 were interrogated to identify the drivers of excessive algal growth. The estuary was highly productive with chlorophyll a concentrations regularly exceeding 100 µg Lˉ¹ , mostly during periods of low freshwater input from the River Taw when estuarine water residence times were longest. The reported approach demonstrates the value of applying conventional statistical analyses in a structured way to existing monitoring data and is recommended as a useful tool for the rapid assessment of estuarine eutrophication. However, understanding of primary production dynamics in the Taw was constrained because of the low temporal resolution, heterogeneity and gaps in the EA data. Therefore, a temporal high resolution monitoring campaign was conducted in summer 2008 to document the development and decline of three algal blooms. The significance of long water residence times following low freshwater inflow and neap tides was confirmed. During peaks in chlorophyll a concentration (max. 226 µg Lˉ¹ ) , nutrient limitation switched from P to Si and persisted for more than 2 weeks in the outer estuary. Signs of ammonium and phosphate ( <0.2 µM) and silicate ( <2 µM) depletion were also observed. Using multivariate statistics, five distinct sets of environmental conditions present in the Taw at different stages of algal growth were identified and directly linked to freshwater inflow. UK Climate Impacts Programme scenarios predict a 30-50% decrease in Q95 flows (the flow which is exceeded 95% of the time) of rivers in south Britain by 2050. Under the current nutrient regime, this is likely to severely increase the severity and duration of symptoms of eutrophication in the Taw and favour potentially hazardous phytoplankton groups instead of diatoms. To mitigate future eutrophication events in the Taw, it is recommended to further reduce N and P inputs. It is also crucial to perform a detailed assessment of potential climate change consequences for the Taw Estuary and similar systems.

A good ecological status of streams and rivers is crucial for maintaining ecological functionality of running waters. Worldwide eutrophication threatens to change structure and function of freshwater ecosystems (Dodds et al., 2008). To reduce the symptoms of eutrophication in streams and rivers an additional approach, besides the reduction of external nutrient inputs from catchment areas, is needed. Therefore the goal has been set to transfer the approach of biomanipulation, which is widely accepted as tool in water quality management in lakes and reservoirs, to streams. The objective of this study was accordingly to analyse and evaluate some crucial preconditions for top-down control of stream food webs. For that purpose the present thesis examined effects of fish predation (stone loach and gudgeon) on grazer-periphyton interaction in small streams by assessing predator avoidance by benthic grazers, effects of benthic grazers on periphyton community composition during fish presence/absence and the possibility of top-down control on algal biomass by benthivorous fish.

Thesis (M.Phil.)--City University of Hong Kong, 2005.
"Submitted to Department of Biology and Chemistry in partial fulfillment of the requirements for the degree of Master of Philosophy" Includes bibliographical references (leaves 153-181)

The first two parts of this study are concerned with a natural field project in which I measured specific plant traits, community state variables, species frequencies, and soil fertility in a large scale comparative study of eight Great Lakes wetlands. I asked the following questions: (1) Are there measurable, quantifiable differences between wetlands--with respect to plant traits, community state variables and fertility, and (2) Are there empirical relationships between plant traits/community state variables and fertility variables. Significant differences between four productive and four unproductive wetlands were found across all the plant traits, except rhizome diameter, all the community state variables and all the fertility variables, except nitrogen. Productive wetlands had lower species richness and were taxonomically distinct from unproductive wetlands. I found that total phosphorus was the most important independent variable and that the most important dependent variables were plant height, standing crop, and species richness. I ran a large outdoor screening experiment bioassaying 40 wetland plants, at two fertility levels, to measure a trait I call 'biomass sensitivity'. I found that all species produced more biomass in the fertile treatment. By comparing species according to the proportional 'biomass sensitivity' (P($\Delta$B)) trait, that is the proportional change in biomass between high and low nutrients, I find there are no differences between species. (Abstract shortened by UMI.)

This research investigates the links between nutrient enrichment, bryozoan abundance and the development of myxozoan parasites in bryozoans. It was found that bryozoan abundances are elevated in nutrient-rich rivers, demonstrating the potential bio-indicator value of bryozoans and predicting increased bryozoan abundances with increased planktonic productivity when space is not limiting. A comprehensive set of laboratory microcosm studies showed also that experimental nutrient enrichment increased growth rates and statoblast production in Fredericella sultana, corroborating the results from field surveys.

Release of phosphorus (P) from bed sediments to overlying waters (internal P-loading) can detrimentally alter ecological structure and function in shallow lakes. The theory of regime shifts states that shallow lakes can exist in alternative states and that shifts between states can occur as a result of disturbance. The main hypothesis of this study was that the use of a P-capping agent (Phoslock®) in shallow lakes (i.e. a controlled disturbance) will break down the internal P-loading feedback mechanism resulting in a regime shift. Experiments, ranging in scale from mesocosm to whole-lake, showed that Phoslock® significantly reduced internal P-loading by increasing the mass of P stored in more refractory sediment P-fractions relative to potentially release-sensitive P-fractions. Intact sediment core experiments highlighted that the application of high areal loads of Phoslock® can, at least temporarily, significantly alter the vertical distribution of sediment dissolved oxygen concentrations and cycling of nutrients other than P, suggesting that the application of high areal loads of Phoslock® to lakes should be avoided. Disruption of internal P-loading in Loch Flemington (Inverness, UK) caused a significant reduction of in-lake P concentrations, a decrease of phytoplankton biomass and an increase in water clarity. The observed changes were generally comparable to those observed in long-term multi-lake studies investigating the recovery of shallow lakes following external P-load control, but occurred over a shorter time scale (1 year compared to decades). Alterations in ecological structure and function indicated that a change in state from a ‘phytoplankton dominated turbid state’ to a ‘macrophyte dominated clear water state’ was achieved in Loch Flemington. This study confirms that it is possible to force a state change in shallow lakes by disturbing feedback mechanisms and documents further work required to improve the efficacy of the Pcapping approach in lake remediation.

Eutrophication of marine and coastal waters is a growing concern throughout Europe's regional seas and an historical problem in the Black Sea and regions of the North-East Atlantic, particularly the North Sea. As the base of the marine pelagic food web, phytoplankton are sensitive indicators of environmental change and therefore may be used as indicators of eutrophication for the monitoring, management and mitigation of the effects of nutrient loading on coastal and marine ecosystems. However, due to the interactive effects of climate and eutrophication, it can be difficult to separate the climatedriven response of phytoplankton from changes induced by excess nutrients. Therefore, the aim of this work is to separate these two signals in order to explore eutrophication effects. Without historical knowledge of 'pristine' or unimpacted ecosystem states it is difficult to identify and assess the severity and magnitude of change. Even w~re spatially and temporally comprehensive ecological datasets are available, equivalent nutrient timeseries are rare and a method of linking phytoplankton dynamics to eutrophication is required. Because open sea ecosystems are less impacted by anthropogenic nutrients than those near shore, offshore regions may be used as reference areas in comparison with coastal systems to investigate the effects of nutrient loading. Changes observed solely in coastal systems are mo$1likely a result of local processes (such as eutrophication) while those observed in both open sea and coastal areas are probably a response to large-scale drivers (such as climate). Therefore the comparison of coastal and open sea data may reveal different (or similar) patterns ofchange in phytoplankton indicators. Throughout most of the North-East Atlantic climate appears to override the effects of nutrients on phytoplankton dynamics, although the two drivers have been found to have synergistic effects resulting in increasing chlorophyll levels in the coastal North Sea. Additionally, the 1980s North-East Atlantic regime shift is clearly visible in coastal and open sea chlorophyll concentrations and diatom and' dinoflagellate abundances, demonstrating the sensitivity of phytoplankton as indicators at both the biomass and functional group scales. In the Black Sea, an observed decrease in chlorophyll appears to be at least partially a result of changes in climate and is not solely attributable to the 'recovery' of the Black Sea ecosystem. Black Sea chlorophyll has also undergone a possible recent (2002) regime shift, although its significance is difficult to determine due to the short time-series of chlorophyll data available. . The successful use of phytoplankton as indicators of eutrophication in these two disparate sea regions at two different ecological scales suggests that the method of comparing coastal and open sea phytoplankton data could be applied to other European seas as a means of distinguishing betWeen the effects of climate and eutrophication.

The primary aim of this study was to develop a diatom based nutrient transfer function for central México, and apply it to a sediment core from Laguna Zirahuén, Michoacán Mexico, (19⁰ 26' N, 101⁰ 44' W) reconstruct change in nutrient availability over the last ca. 200 years. The principle techniques employed were analysis of diatoms, stable isotopes of carbon and nitrogen and lipid biomarkers. These were supplemented by magnetic susceptibility and isotopic measurements of modern aquatic and terrestrial organic matter. In order to interpret the diatom record and quantitatively reconstruction the change in the diatom flora a calibration data set, from 30 lakes, was collected during both the wet and the dry seasons. Detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) were used to explore species-environment relationships and to establish which environmental variables made independent and significant contributions to species variance. Results showed that electrical conductivity and chlorophyll-a caused a significant and independent proportion of variance in the species data (12.54%, p = 0.001), this was supported by variance partitioning and the ratio of CCA axis one to CCA axis two. Weighted averaging regression and calibration was then used to create an inference model to reconstruct changes in Chlorophyll-a. The strength of the model was assessed using the squared coefficient of determination (r2 = 0.83) and root mean square of errors (RMSE = 0.32). Application of cross validation resulted in a substantial drop in r2 and increase in RMSEP, this is most likely associated with the small and heterogeneous nature of the data set. Numerical reconstruction of the change in nutrient status was complicated by a high number of non-planktonic species and a lack of modern analogues. In the upper 3 cm the trajectory of change inferred by the reconstruction was, however, in line with other existing contemporary nutrient data from the lake. There is a marked decrease in productivity between 24 and 9 cm, shown by declining concentrations of 013C, lipid biomarkers, 013C and diatom inferred Chl-a and corresponding increase C/N. This may correspond to the decline in the copper smelting industry in the basin the in the late 19th early 20th century. A rise in productivity is noted over the top 3 cm of the core, possibly the last 15-20 years. The majority of proxies showed a marked response to the deposition of the Paricutín tephra. Despite the fact that electrical conductivity is the primary variable in controlling diatom species variation, it is evident that human impact on lake basins though increased levels of nutrients in having an impact on the ecology of the lake. In the case of Laguna Zirahuén its sensitivity and the current trajectory of change may be an important consideration in its future management.

The need to increase productivity in grasslands has led to the addition of nutrients to the point where plant species have been lost. The cascading effect of this loss on the community of associated species is not well understood. The aim of my thesis is to study how variation in soil nutrients - both natural and by the addition of fertilisers - changes plant community composition and how these changes affect the structure of plant-flower visitor networks, plant-herbivore networks and herbivore-parasitoid networks. There are three parts to my study. First, I tested if high fertility decreases insect specialization using natural variation in soil fertility and a nutrient enrichment simulation. I observed that higher nutrients led to less specialist, but more robust ecological networks in both current and simulated scenarios. In the second study, I evaluated the effects of a 27-year experiment, which added both organic and inorganic fertiliser to replicate plots, on the three types of network. Eutrophication decreased the number of forb species, and this changed the structure of the ecological networks. These changes however, took place with no change in insect species richness. Finally, I compared the performance of organic and inorganic fertilisers on the production of livestock forage alongside its impact on biodiversity, asking if there is an optimum fertilizer strategy where both livestock and biodiversity can co-exist? While there was no fertiliser treatment that had the best performance for all the variables studied, the application of farmyard manure offered the closest to a win-win scenario. Looking forward, to evaluate the consequences of eutrophication and achieve sustainable production in grasslands, an interdisciplinary approach is needed where ecologists and livestock managers work closely together to identify management solutions acceptable to both.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior
Com o crescente aumento da demanda de Ãgua e a preocupaÃÃo de que a oferta estabelecida nÃo consiga suprir esse consumo, torna-se necessÃria a conservaÃÃo da quantidade e, principalmente, da qualidade da Ãgua disponÃvel, especialmente em regiÃes semiÃridas como o Nordeste brasileiro (NEB), onde esse recurso à escasso. As principais causas da poluiÃÃo da pequena aÃudagem no semiÃrido sÃo: a presenÃa de animais nas margens dos aÃudes, onde defecam e urinam; os efluentes domÃsticos (e.g. lavagem de roupas, Ãguas utilizadas nas atividades domÃsticas); o desmatamento da mata ciliar, que protegeria os aÃudes contra o assoreamento e a entrada de matÃria orgÃnica; a presenÃa de lixo ao ar livre; e o uso de insumos agrÃcolas que contribuem para o processo de eutrofizaÃÃo. Por sua vez, a principal caracterÃstica do processo de eutrofizaÃÃo à o excesso de nutrientes nos corpos dâÃgua, apresentando grandes oscilaÃÃes de crescimento e mortandade de algas e macrÃfitas. AtravÃs da continuidade do processo, hà o acÃmulo de matÃria morta na regiÃo mais profunda desses ambientes, causando o aumento do metabolismo de bactÃrias que ocasiona a mortandade de peixes e outros organismos pela falta ou diminuiÃÃo de oxigÃnio, acrescentando-se, ainda, o fato da produÃÃo de toxinas, por algas cianofÃceas, ser prejudicial à biota e à saÃde humana. Diante disso, estudos que estimem o aporte de nutrientes tornam-se impostergÃveis para que, a partir daÃ, medidas que auxiliem na recuperaÃÃo de reservatÃrios eutrofizados possam ser tomadas. Entre tais medidas hà a biomanipulaÃÃo. Esta à uma ferramenta biolÃgica e o seu preceito basilar consiste na utilizaÃÃo de organismos aquÃticos (e.g. peixes), no sentido de melhorar a qualidade do ecossistema aquÃtico. Pergunta de Partida: à possÃvel tratar um aÃude eutrofizado usando biomanipulaÃÃo No caso afirmativo, quais as particularidades para um aÃude no semiÃrido, principalmente no que tange a sua ictiofauna a qual apresenta maior riqueza de espÃcies, estoques com dominÃncia de peixes onÃvoros e onde a reproduÃÃo dos peixes ocorre durante todo o ano? Assim sendo, com o escopo de responder as aludidas questÃes a presente tese foi dividida em duas partes: a primeira compara o estado de eutrofizaÃÃo e suas provÃveis causas em dois reservatÃrios tropicais, um em clima Ãmido (La Juventud, Cuba) e o outro em clima semiÃrido (Marengo, Brasil). ApÃs estimar o estado trÃfico dos dois reservatÃrios nas estaÃÃes chuvosa e seca, avaliou-se a influÃncia hidrolÃgica e de uso do solo sobre o grau de trofia dos lagos. Concluiu-se que o lago tropical semiÃrido encontrava-se eutrÃfico, enquanto que o lago Ãmido encontrava-se mesotrÃfico. Considerando-se que hà similitude entre os usos do solo nas duas bacias e que, na estaÃÃo chuvosa, o aporte de nutrientes na bacia Ãmida à consideravelmente superior ao da bacia semiÃrida, o maior estado trÃfico da bacia seca sur-preende. A variÃvel que melhor explica esse fenÃmeno à o tempo de residÃncia da Ãgua, que influencia diretamente o tempo de residÃncia do fÃsforo no lago. O elevado tempo de residÃncia da Ãgua na bacia semiÃrida (trÃs vezes superior ao do lago Ãmido) deve-se tanto ao reduzido coeficiente de escoamento superficial (93 versus 595 mm anuais na bacia Ãmida) quanto à excessiva evaporaÃÃo da Ãgua armazenada no reservatÃrio seco (1,2 vezes superior à do reservatÃrio Ãmido). Esses resultados indicam que lagos semiÃridos sÃo mais vulnerÃveis à eutrofizaÃÃo que lagos Ãmidos nos perÃodos de estio e que, portanto, o manejo de suas bacias deve ser mais restritivo à produÃÃo de nutrientes; consoante a segunda parte, essa retrata em particular a questÃo da biomanipulaÃÃo. Nesse sentido, em mesocosmos experimentais de 2.000 L, foram delineados seis tratamentos para avaliar o efeito de duas espÃcies onÃvoras (tilÃpia do Nilo â Oreochromis niloticus e piaba â Astyanax bimaculatus) sobre Ãguas eutrÃficas. Observou-se, ainda, a influÃncia do sedimento como fonte de nutriente para o processo de eutrofizaÃÃo. Os tratamentos avaliados foram: 1. Oreochromis niloticus sem sedimento; 2. Oreochromis niloticus com sedimento; 3. Oreochromis niloticus + Astyanax bimaculatus sem sedimento; 4. Oreochromis niloticus + Astyanax bimaculatus com sedimento; 5. Astyanax bimaculatus sem sedimento e; 6. Astyanax bimaculatus com sedimento. Cada ensaio foi conduzidos por 45 dias. Coletas dâÃgua foram realizadas a cada 15 dias. Foram feitas anÃlises de fÃsforo total, ortofosfato, clorofila a e nitrogÃnio total, sendo este analisado somente no inÃcio e final de cada tratamento. As concentraÃÃes de oxigÃnio dissolvido, temperatura, pH e transparÃncia de Secchi foram feitas in situ. No sedimento realizou-se anÃlises de pH, concentraÃÃo de Ãons e nutrientes tais como Ca2+, Mg2+, Al3+, ferro, fÃsforo assimilÃvel e anÃlise granulomÃtrica. Para se estimar o grau de trofia da Ãgua dos tratamentos foi aplicado o Ãndice de estado trÃfico (IET) de Toledo Jr. et al. (1983). DiferenÃas entre os IETs foram calculadas conforme Carlson (1991). Fez-se, ainda, a anÃlise do teor de fÃsforo total nos peixes. Os resultados sugeriram que os sistemas que continham tilÃpias do Nilo apresentaram baixa eficiÃncia na recuperaÃÃo de Ãguas eutrofizadas. O IET mÃdio obtido nesses ensaios mostrou que a Ãgua manteve-se sempre eutrÃfica. Os tratamentos com piabas mostraram uma melhor eficiÃncia no controle da eutrofizaÃÃo. O IET mÃdio obtido nesses ensaios revelou que a Ãgua passou de eutrÃfica para mesotrÃfica, ao final dos mesmos. Contudo, os resultados encontrados pelas diferenÃas dos IETs nÃo confirmam que as piabas foram sozinhas as principais responsÃveis por esse fato. O mesmo pode ter sido influenciado, tambÃm, pela luz e pela temperatura. Quanto ao teor de fÃsforo total, para os espÃcimes advindos dos tratamentos, a tilÃpia apresentou bioacumulaÃÃo superior ao encontrado nas piabas. Todavia, os resultados foram antagÃnicos para os espÃcimes oriundos diretamente da natureza. Em suma, foram avaliados aspectos da biomanipulaÃÃo de duas espÃcies onÃvoras; o Oreochromis nilotucus que, em funÃÃo de seu comportamento, revelou-se um agente perturbador da qualidade da Ãgua e o Astyanax bimaculatus, a qual se apresentou potencialmente viÃvel para futuras pesquisas de biomanipulaÃÃo.
With the increasing water demand and the concern that the supply can not meet that consumption, it is increasingly necessary conserving the available water, in quantity and (especially) quality. This conservation is especially important in semi-arid regions such as the Brazilian Northeast (NEB), where water is scarce. The main causes of pollution (water waste) in smal reservoirs (in the semiarid) are: the animal presence on the reservoir margins, where they defecate and urinate; domestic wastewater (e.g. laundry water, water used in the household); removal of riparian vegetation, which protects reservoirs against silting and organic matter input; presence of outdoor trash; and use of agricultural inputs that contribute to the process of eutrophication. In turn, the main feature of eutrophication process is excess nutrients in water bodies, with considerable growth fluctuations and eventual death of algae and weeds. With the continuity of the process, there is the accumulation of dead matter in the deepest region of these environments, causing the increase in bacterial metabolism that causes the death of fish and other organisms by oxygen lack or reduction, plus the toxin production by blue-green algae, which are harmful to human health and to the biota at large. Therefore, studies that estimating the nutrient input become urgent. With such studies, strategies for the restoration of eutrophic reservoirs can be implemented. Among such strategies there is biomanipulation. Biomanipulation is a biological strategy based in the use of aquatic organisms (e.g. fish), to balance the aquatic ecosystem. Hypothesis: "Is it possible to treat an eutrophic reservoir using biomanipulation?â If so, what are the particularities of biomanipulating a reservoir the semiarid region, especially considering its rich ictiological diversity, with predominantly omnivorous fish population and where fish reproduction occurs throughout the year? Therefore, in order to answer these questions, this thesis was divided in two parts, the first comparing the state of eutrophication and its probable causes in two tropical reservoirs, one in wet climate (La Juventud, Cuba) and the other in semiarid climate (Marengo, Brazil). After estimating the trophic state of the two reservoirs in rainy and dry seasons, we evaluated the influence of hydrology and of land use on reservoir trophic level. It was found that the semi-arid tropical reservoir was eutrophic, while the reservoir on humid climate was mesotrophic. Considering that there is similar land use in the two basins and that, in the rainy season, the nutrient input in the wet basin is considerably higher than the nutrient input in the semiarid basin, the higher trophic state of the semi-arid basin is surprising. The variable that best explains this phenomenon is the water residence time, which directly influences the phosphorus residence time in the reservoir. The high water residence time in the semiarid basin reservoir (three times that of the reservoir in humid climate) is due as much to the low runoff coefficient (93 versus 595 mm per year in the reservoir in humid climate) as to the excessive water evaporation in the semiarid reservoir (1.2 times that of the reservoir in humid climate). These results indicate that semiarid reservoirs are more vulnerable to eutrophication than reservoirs in humid climate in summer periods and, therefore, the management of their basins should be more restrictive to nutrient production; as to the second part, it reflects the particularities of the biomanipulation issue. Thus, in experimental 2000L mesocosms, six treatments were outlined to evaluate the effects of two omnivorous species (Nile tilapia â Oreochromis niloticus and piaba â Astyanax bimaculatus) on eutrophic waters. It was also taken into account the sediment influence as a nutrient source for the eutrophication process. The treatments were: 1. Oreochromis niloticus without sediment; 2. Oreochromis niloticus with sediment; 3. Oreochromis niloticus plus Astyanax bimaculatus without sediment; 4. Oreochromis niloticus plus Astyanax bimaculatus with sediment; 5. Astyanax bimaculatus without sediment and; 6. Astyanax bimaculatus with sediment. Each test was conducted for 45 days. Water samples were taken every 15 days. Tests were performed for total phosphorus, orthophosphate, chlorophyll a and total nitrogen (TN being tested only at the beginning and at the end of each treatment). Testing for dissolved oxygen concentration, temperature, pH and Secchi transparency was done in situ. The sediment was tested for pH, ion content, nutrients (such as Ca2+, Mg2+, Al3+, iron and assimilable phosphorous) and particle size. In order to estimate the treatment water trophic level, the trophic state index (TSI) of Toledo Jr. et al. (1983) was applied. Differences between the TSI values were calculated acording to Carlson (1991). Also, the fish were tested for total phosphorus content. The results suggested that systems containing tilapia showed low efficiency in the recovery of eutrophic waters. The average TSI obtained in these tests showed that the water remained eutrophic. Treatments with piabas showed better efficiency in controlling eutrophication. The average TSI obtained in these tests showed that the water went from eutrophic to mesotrophic. However, the results found by TSI differences do not confirm if the piabas (Astyanax bimaculatus) were alone responsible for this. The same results could be also influenced by light and temperature. As to the total phosphorus content of specimens coming from treatments, tilapia showed higher bioaccumulation than that shown by piabas. However, the results were antagonic to those obtained from specimens taken directly from nature. In short, two omnivorous species were tested for their biomanipulation potential; the Oreochromis nilotucus, which, due to its behavior, proved to be an agent of water quality disruption and the Astyanax bimaculatus, which was shown as being potentially viable for future biomanipulation research.

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia do Ambiente, perfil Engenharia Sanitária
Coastal eutrophication is a global problem which affects many natural systems and human activities throughout the world. The phenomenon of eutrophication has increased substantially due to human activities. It is caused by excess nutrients and is identified by the emergence of some symptoms. The proposed assessment will address this problem in a more specific way. The Assessment of Estuarine Trophic Status (ASSETS)methodology is going to be performed to two Northern Irish Loughs in order to rank their eutrophication status and allow a comparison with other existing methods. The data available for these systems allowed the implementation of this innovative methodology, which can provide a classification based on pressure, state and response. Thus, by considering the influences of anthropogenic activities over the coastal areas, examination of specific symptoms of the water systems and analyzing the indicators for future response, it is possible to achieve consistent results regarding the quality of the water in the “loughs” and, consequently, identify the most adequate tools to enable their proper management. By controlling the nutrient enrichment of coastal areas it is possible to avoid problems, such as, fish kills, interdiction of shellfish aquaculture, loss or degradation of sea grass beds and smothering of bivalves and other benthic organisms. As a result, many social and economical costs can be reduced. ASSETS was successfully applied to both Strangford Lough and Belfast Lough, classifying them as “Moderate”. This classification will not change their water quality status under the Water Framework Directive, Urban Wastewater Treatment Directive or Nitrates Directive, however, it is a tool to guide policy makers into better decisions in terms of future management.

Lake Manassas is a man-made impoundment in the Northern Virginia suburbs of Washington, D.C. The lake currently supplies drinking water at an average rate of 10.5 million gallons per day to the City of Manassas, Virginia. The lake discharges, via the Broad Run, a tributary of the Occoquan Reservoir. The Occoquan Reservoir supplies potable water to over 750,000 people in the Northern Virginia area. This thesis presents the results of a limnological analysis of Lake Manassas. The techniques used are established limnological techniques to arrive at a profile which can be compared to accepted scales of ranking. One conclusion from the analysis is that Lake Manassas is eutrophic, which means that the production of biomass in the lake is at a higher than desired rate. The result of this eutrophic condition is that the water quality of the lake will decline rather rapidly. Another conclusion is that Broad Run is the major supplier of nutrients into Lake Manassas, but that conditions are also affected by a point source discharge from a sewage treatment plant. These conclusions are consistent with previous studies done on Lake Manassas. In summary, Lake Manassas is an important water resource in the Northern Virginia area, and it is important to continue to closely monitor and manage runoff practices in the watershed to ensure the lake does not degrade to unacceptable conditions.
Master of Science

Coastal eutrophication, defined as an increase in algal biomass (as chlorophyll (Chl)) is of increasing international concern. Although coastal eutrophication will likely increase as coastal populations grow, few models exist to support its management. Lake eutrophication has also long been recognized as an important environmental concern. However, effective lake eutrophication management exists, supported by regression and mass-balance models. Traditionally, these "Vollenweider" models link land-use to Chl via total phosphorus (TP), the nutrient considered to be limiting Chl. However, based on a data set of 63 lakes, Chl was more accurately predicted by models based on land-use than by those based on TP. This result provided the rationale to build Chl:land-use models for estuaries where the Chl:nutrient relations are unclear. Chl:land-use models were developed for 15 estuaries in PEI, 19 estuaries in Finland and 26 US estuaries. Land-use models predicted Chl more accurately than TP in the US estuaries and in some of the Finnish estuaries. In the Finnish estuaries, Chl was best predicted by a land-use model in estuaries dominated by nonpoint source loading whereas Chl was most accurately predicted by the Vollenweider approach in estuaries dominated by point-source loading. In the PEI estuaries, the accuracy of the land-use model was comparable to the accuracy of the TP model. The PEI estuaries had much lower yields of Chl per unit nutrient than lakes suggesting differences among systems. This Chl deficit (expected-observed Chl) was accounted for by herbivory and turbidity, neither of which factors are exclusive to estuaries. The comparison of Chl response to nutrients and land-use across lakes and estuaries demonstrated no systematic differences as a function of tidal energy, openness or salinity. The regression models based on the combined data accurately predicted Chl as a function of TP and percentage of the catchment forested and mean depth. These results sug

Brown Moss is a Site of Special Scientific Interest and a part of a RAMSAR site located within a small catchment area in North Shropshire. Despite its small size, it is important and has ostensibly high ecological values. It comprises a series of standing water bodies that are crucial natural habitats for rare aquatic plants and animals such as Luronium natans (Linnaeus) and Triturus cristatus (Laurenti). However, located within such small catchment area, Brown Moss may have been eutrophicated by nutrients from land use and other factors around the site and this can lead to reduction of importance and ecological values. Being waterfowl habitats, the pools may also have become affected by nutrient input from birds and aquatic macrophytes communities may have been damaged.

The Vaal Dam is one of South Africa’s important inland water resources, however it is experiencing ecological problems related to eutrophication. The dam supplies water for domestic, industrial, mining and agricultural usage. This research aims to assess and monitor the threats of eutrophication and cyanobacterial blooms within the Vaal Dam. A 10-year archive of remotely sensed satellite data was collected from the medium resolution imaging spectrometer full resolution (MERIS FR) satellite from 2002 to 2012. Data products on chlorophyll-a, cyanobacteria concentration, cyanobacteria and surface scum percentage coverage data were derived from MERIS satellite imagery, using the maximum peak height (MPH) algorithm. The derived data products were used as indicator measures of the trophic status. This research presents a time series analysis of chlorophyll-a (a proxy for eutrophication) and cyanobacteria to establish the status, seasonality and trends for the Vaal Dam. Statistical analysis methods were applied to determine the drivers of eutrophication. In addition, the effects of climate variables on eutrophication were analyzed. Geographic Information Systems methods were applied to determine the spatial distribution and variations of chlorophyll- a. The results indicate the trophic status of the Vaal Dam ranged from being eutrophic and hypertrophic over the 10-year period. Seasonality analysis indicated that cyanobacteria blooms increased in production during the summer period and decreased in winter. Statistical analysis of the results indicated that the correlation between Chl-a and nutrients is not statistically significant. Therefore, nutrients themselves are not driving eutrophication in the Vaal Dam. The produced maps from satellite images showed the spatial distribution of Chl-a within dam. The maps indicated the eastern areas of the Vaal Dam as areas where algal and cyanobacteria blooms occur in high concentrations. The correlation between Chl-a and climate variables indicates that there is a correlation with temperature and wind speed, and an indistinct relationship with rainfall. The study concludes that both nutrient and climatic variables contribute as drivers of eutrophication within the Vaal Dam. The methods applied in this research will help to transform the satellite data into useful knowledge products, which can be used to supplement current monitoring of inland freshwater resources.

The eutrophic state of North Lake is typical of other aquatic systems on the Swan Coastal plain. These bodies of water have long been regarded as convenient outlets for both urban and agricultural runoff. However, the runoff from such sources is high in phosphorus and nitrogen and as a consequence the ecosystem of the lake becomes dominated by free-floating single celled plant (algae). Their decay following peak growth periods leads to the production of noxious odours, and this in turn leads to complaints to the local council from nearby residents. This was the case at North Lake in December 1986. This study was commenced in August 1987 to assess the problems of nuisance algal growth at North Lake and to review relevant management strategies. The results of this study showed North Lake to be highly eutrophic throughout the year. Peak algal growth occurred during the winter months when the external loading of phosphorus and nitrogen to the lake was highest. Of the two external drains entering North Lake the south-east drain was the most significant contributor of nutrient to the lake. The catchment of this drain is the Murdoch University Veterinary Farm and contributes 73% of the total annual load of phosphorus and 56% of the total load nitrogen. The most immediate courses for management of North Lake is the treatment of runoff from the Murdoch University Veterinary Farm. However, patterns in algal growth and results of sediment exchange experiments strongly indicate that the internal loading of phosphorus and nitrogen is sufficient to maintain the eutrophic state of North Lake. In the long term, if the lake fails to improve after treatment of drain water, dredging or chemical treatment to remove phosphorus may become necessary.

Lake Manassas is an approximate 706 acre man-made lake located in greater Prince William County near the town of Gainesville, Virginia. The lake was created in 1968 on Broad Run to serve as the primary water supply for the City of Manassas and its residents. The Lake Manassas watershed lies within the greater Occoquan River watershed which drains into the Potomac River and Chesapeake Bay. Water within Lake Manassas and its tributaries has been monitored since 1971 and this thesis presents a comprehensive limnological analysis of the Lake with an analysis of water quality impacts over time.

Lake Manassas remains an enriched or eutrophic system, meaning the levels of nutrients and biomass production in lake waters is above desired standards. Nutrient loading occurs via a stream network with the largest contributor being Broad Run which is consistent with previous water quality studies.

The lake serves as the sole water source for nearly 40,000 residents and businesses and ensuring clean and safe water is of significant importance. Close monitoring in conjunction with the implementation of appropriate management practices within the watershed are necessary to prevent water quality from becoming significantly degraded.
Master of Science

In this study, a new analytical method for the simultaneous determination of total N, P and S using hydrogen peroxide oxidation has been developed for the analysis of water and sediment samples. The products of the oxidation reaction (nitrate, phosphate and sulphate) were determined by ion chromatography. A method for the simultaneous chemical speciation of arsenic, selenium and chromium was developed using ion chromatography coupled with ICP-MS. Reversed phase chromatography and ICP-MS was used for the simultaneous determination of mercury and selenium species. For the speciation of vanadium a new method using HPLC with reversed phase and ICP-MS detection was developed. The species arsenite, arsenate, selenite, selenate, chromate, methylmercury, inorganic mercury, selenocystine, selenomethionine, vanadium (IV) and vanadium (V) in samples of water, sediment, fish muscle tissue and mussel, were determined using the developed methods. Simultaneous determination of nutrients and metal species were applied to the study of pollution in Lake Maracaibo, Venezuela. The distribution of As, Se, Pb, Hg, Sn and V in sediment was studied using a sequential extraction scheme and related to the physicochemical parameters and nutrient content. The major concentrations of arsenic and lead found inside the lake were associated with the fraction associated with the Fe/Mn hydroxides phase, however, mercury and selenium were distributed at the main zone of the lake in the organic-sulphide fraction. In the strait and the gulf, metals were distributed mainly in the residual phase with the exception of tin. Conditions which favour mercury methylation in the lake are discussed. In the centre of the lake, with anaerobic conditions, methylmercury was the predominant species for mercury. The results found for vanadium and arsenic speciation showed that the predominant species in all the samples of Lake Maracaibo was vanadium (IV) and arsenite, respectively. Results were compared with those from lakes with similar pollution problems.

Seagrass meadows are highly productive, ecologically and economically valuable ecosystems. However, increased human activities along the coastal areas leading to processes such as eutrophication have resulted in the rapid loss and deterioration of seagrass ecosystems worldwide. This thesis focuses on the responses of seagrasses to increases in nutrients, subsequent increases in ephemeral algae, and changes in the physical-chemical properties of seawater induced by interaction with other marine biota. Both in situ and laboratory experiments conducted on the tropical seagrasses Cymodocea serrulata and Thalassia hemprichii revealed that increased concentrations of water column nutrients negatively affected seagrass photosynthesis by stimulating the growth of the epiphytic biomass on the seagrass leaves. Interaction between seagrasses and other marine organisms induced different responses in seagrass photosynthesis. Ulva intestinalis negatively affected the photosynthetic performance of the temperate seagrass Zostera marina both by reducing the light and by increasing the pH of the surrounding water. On the other hand, the coexistence of mussels Pinna muricata and seagrass Thalassia hemprichii enhanced the photosynthetic activity of the seagrass, but no effect on the mussels' calcification was recorded. This study demonstrates that seagrass productivity is affected by a multitude of indirect effects induced by nutrient over-enrichment, which act singly or in concert with each other. Understanding the responsive mechanisms involved is imperative to safeguard the ecosystem by providing knowledge and proposing measures to halt nutrient loading and to predict the future performance of seagrasses in response to increasing natural and human perturbations.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Papers 1, 3 and 4: Submitted. Paper 2: Manuscript.
Swedish Agency for Research Cooperation (Sida/SAREC) marine bilateral programme

A 1D numerical reaction-transport model (RTM) that is a coupled system of partial differential equations is created to simulate prominent physical and biogeochemical processes and interactions in limnological environments. The prognostic variables considered are temperature, horizontal velocity, salinity, and turbulent kinetic energy of the water column, and the concentrations of phytoplankton, zooplankton, detritus, phosphate (H3PO4), nitrate (NO3-), ammonium (NH4+), ferrous iron (Fe2+), iron(III) hydroxide (Fe(OH)3(s)), and oxygen (O2) suspended within the water column. Turbulence is modelled using the k-e closure scheme as implemented by Gaspar et al. (1990) for oceanic environments. The RTM is used to demonstrate how it is possible to investigate limnological trophic states by considering the problem of eutrophication as an example. A phenomenological investigation of processes leading to and sustaining eutrophication is carried out. A new indexing system that identifies different trophic states, the so-called Self-Consistent Trophic State Index (SCTSI), is proposed. This index does not rely on empirical measurements that are then compared to existing tables for classifying limnological environments into particular trophic states, for example, the concentrations of certain species at certain depths to indicate the trophic state, as is commonly done in the literature. Rather, the index is calculated using dynamic properties of only the limnological environment being considered and examines how those properties affect the sustainability of the ecosystem. Specifically, the index is calculated from a ratio of light attenuation by the ecosystem’s primary biomass to that of total light attenuation by all particulate species and molecular scattering throughout the entire water column. The index is used to probe various simulated scenarios that are believed to be relevant to eutrophication: nutrient loading, nutrient limitation, overabundance of phytoplankton, solar-induced turbulence, and wind-induced turbulence.

Extensive growth of algal blooms as a consequence of eutrophication may bring serious health effects to humans including fatalities. Several attempts in reducing the eutrophication or algal blooms in waterbodies have been implemented in past few decades. However, most of the control methods were focused on temperate systems rather than tropical systems. Therefore, this study was aimed to develop a mitigation framework for reducing eutrophication and algal blooms in tropical regions. This work focusses more on humid tropic systems because there is a lack of research resources in this region. The study involved four main work packages: (a) systematic review study to track the available eutrophication control techniques; (b) development of eutrophication framework; (c) assessment of seasonal water quality in Durian Tunggal Reservoir (DT) and Jus Reservoir (Jus); and (d) evaluation of eutrophication management framework using DT and Jus reservoir as case study. The study starts with systematic review study to track the available eutrophication control techniques. Findings from the systematic review were used to develop the eutrophication framework by providing the established method that can be used to mitigate the eutrophication problem. The framework consists of two stages; a pre-selection stage and a selection stage. The pre-selection stage requires the decision maker to evaluate the condition of the waterbody. Meanwhile, the selection stage is where suitable control techniques are suggested based on Multiple Criteria Analysis (MCA). The performance of the framework was demonstrated by using a case study of two reservoirs in Malaysia. The results presented in this thesis show that the framework that is proposed using MCA as a decision support tool allows for the selection of robust investments in eutrophication and algal bloom management. The integration of scenario analysis can provide complementary insights into sustainability and cost efficiency for eutrophication management and policy for developing countries by giving the best available techniques according to the selected criteria.

In response to concern that excessive macroalgal growth and accumulation was occurring in some inshore areas of Lake Macquarie, the distribution, abundance and seasonality of macroalgae was investigated in relation to nutrient input and power station cooling water. Macroalgal dry weight biomass was measured at ten sites on a monthly basis for two years, with an analysis of community structure conducted using Multi-Dimensional Scaling. The macroalgal community in Lake Macquarie was typical of those found in other New South Wales coastal lagoons, exhibiting considerable spatial and temporal variation. A close similarity was observed in macroalgal community structure at sites affected by urban nutrient input, these being characterised by a high biomass often attributable to only one or two species. These nuisance macroalgae were mostly green algae, which were almost entirely absent from other sites. Biomass at sites affected by urban nutrient input was generally within the range documented for eutrophic estuaries elsewhere. Analysis of macroalgal community structure showed no evidence of large-scale changes macroalgal communities attributable to the effects of power station cooling water except within 500m of the outfall. At sites affected by a 1-2??C temperature increase, community structure and the magnitude of the biomass were similar to sites deemed as being relatively free of human impact. A reduction in species diversity occurred only within the immediate discharge zone, where water temperatures were approximately 6??C above ambient temperatures. Excessive growth of nuisance macroalgal species was not observed at any of the sites influenced by power station cooling water. There were no distinct patterns in seasonality of macroalgal growth in this study, though the greatest biomass appeared to occur in spring. The irregular temporal variation in macroalgal growth suggests that the most significant factors affecting growth occur on a time scale of weeks to months. It is therefore likely nutrient input to the nearshore through surface runoff is an important influence on the distribution and abundance of macroalgae in Lake Macquarie. This emphasises the need to reduce nitrogen and phosphorus input from urban sources in Lake management.

At present, eutrophication is one of the biggest threats to the Baltic Sea environment. Eutrophication is a process in which water body gathers essential plant nutrients, mainly phosphorus and nitrogen into its system. Eutrophication causes a variety of changes to the marine environment. These effects include an increased primary production, turbidity and sedimentation, the occurrence of anoxia and hypoxia, as well as changes in macroalgal community structures. The most common parameters used to study the negative effects of eutrophication on the environment are nitrogen, phosphorus, chlorophyll-a, water transparency and oxygen. In the past, several efforts and actions were made in order to minimize the negative effects of eutrophication to the sea, for example by European directives. Some of these directives require the use of biological quality elements such as marine flora and fauna as an indicator for the water quality. Because of these requirements, it is important to study the use of filamentous algae as an indicator of eutrophication. This thesis contributes to a better understanding of the impact of land use on the environmental indicators of eutrophication and the opportunity to use filamentous algae as an indicator of eutrophication in the Bothnian Bay. The study area is situated in the Finnish side of the Bay, extending from the city of Oulu in south to the city of Tornio in north. This thesis analyses the impact of the land use practices on the environmental indicators of eutrophication by determining the optimum buffer sizes for land use. Different land use practices show clear correlations to the environmental variables and, based on these results, it can be stated that there is a connection between the two components. In order to investigate the correlation between filamentous algae and eutrophication indicators, the used indicators needed were interpolated to the whole study area. The interpolation was needed, because the datasets were collected from different areas and the resolution of the data of the filamentous algae was much higher. Since the amount of data points from the environmental variables was relatively low with 59 sites, 61 additional data points were chosen to increase the coverage of the data. Linear regression models were created for the environmental variables and based on these models values were estimated for the added data point. The interpolations of the environmental variables were compared with the average values of filamentous algae with the help of Spearman’s rho correlation matrix. In the tests, statistically significant correlations towards the environmental indicators of eutrophication were found. The analyses indicate a connection between the amounts of filamentous algae and eutrophication related indicators. Based on this, in can be concluded that filamentous algae is a useful indicator of eutrophication in the northern Bothnian Bay, when it is used together with other eutrophication indicators. However, attention needs to be paid when comparing data of filamentous algae in a large scale, since other physical factors, such as water temperature, have a significant impact to the distribution and abundance of the algae.

Eutrophication is a major concern in the Baltic Sea and it is affecting macrophyte communities by promoting the growth of opportunistic algae and decreasing the cover of perennial macrophyte species via shading. It is however uncertain how common eutrophication and its symptoms are in the northern parts of the Baltic Sea, the Botnian Sea. The aim of this study was to evaluate if Sörleviken, a bay in the Bothnian Sea, show signs of increased eutrophication pressure in 2020 compared to 2007 based on changes in macrophyte cover and composition. The macrophyte community was inventoried with under-water video techniques in 2020 along three transects, matching transects previously inventoried by a diver in 2007. The three transects were located in the inner, middle and the outer parts of the bay. The results showed that macrophyte diversity was lower in 2020 than in 2007 along the outer transect, but overall, the total cover of macrophytes, relative cover of opportunistic algae, species richness and evenness remained unchanged. A possible higher presence of Stuckenia pectinata (former Potamogeton pectinatus) and a possible lower presence of Chara aspera in 2o2o compared to 2007 might be evidence of higher eutrophication pressure in 2020. However, by observing the general changes in the macrophyte community, this study only provides weak or inconclusive signs of increased eutrophication pressure, thus Sörleviken shows no signs of either improvement of or further increases in eutrophication pressure by 2020 compared to the observations in 2007.

Samples of Porites porites rubble were collected from across three fringing reefs which lie along a eutrophication gradient in Barbados, West Indies. The coral skeleton fragments were examined for clionid sponges. Data collected from the reef crest and fore reef zones and from across the range of distances and depths were pooled for each reef to compare indices of sponge abundance along the eutrophication gradient. Significant differences between the reefs were found for the proportion of rubble invaded (ANCOVA, p = 0.004), number of invasions per sample (ANCOVA, p = 0.002), and number of species per sample (ANCOVA, p = 0.018) but not for total surface area of sponge invasions per sample (ANCOVA, p = 0.064). All the indices demonstrated an increase with increasing eutrophication level. Clionids were found in nearly twice as many of the pieces collected from the most eutrophic site (41%) as from the least eutrophic (24%). Since clionids may be the principal bioeroders of coral reefs, an increase in their abundance due to excessive pollution likely results in greater bioerosion of affected reefs. The mean abundance of Type 3 corals was found to be positively related to the frequency of boring sponge invasion, suggesting that increased bioeroision may be partly responsible for community shifts toward Type 3 corals in polluted waters. One new variety and three new species of boring sponges of the genus Cliona were found. A new variety of C. amplicavata Rutzler is described, Cliona species 2 of MacGeachy is redescribed and Cliona species 4 and Cliona species 5 are described for the first time. Cliona species 5 may become an important bioeroder in Barbados and other Caribbean islands since it flourishes under high eutrophic conditions which are beginning to plague West Indian reefs. (Abstract shortened by UMI.)

Lake Victoria (LV), is the largest tropical fresh water lake. It is however facing a myriad of challenges like eutrophication, introducing species, mass extinction and climate change. Eutrophication has mostly been seen as a result of non-point pollution from upstream agricultural areas. However, studies have found that atmospheric deposition could perhaps be the greatest cause of nutrient loading in the lake. Our study looked at black carbon as one of the factors favoring eutrophication in LV. Black carbon is a product of incomplete combustion of biomass or fossil fuel. Biomass burning is prevalent in many areas of Africa and our results have shown a great spatial and temporal variability in its concentration in sediments. The sedimentation rates calculated after analyzing 210Pb activity were 0.87, 0.53 and 0.35 g cm-2 yr-1 while the average black carbon concentrations were 4.6, 2.1 and 6.9 mg g-1 for Siaya, Kisumu and Busia, respectively. These results provided valuable information when compared to past historical events in the Lake region especially eutrophication. The study also found that soot BC has been increasing in the past 100 years suggesting the input from fossil fuels. This study elucidates the complexity of drivers of eutrophication in Lake Victoria. Nitrogen and Phosphorous from the upstream agricultural sites has long been seen as the main cause of eutrophication. Through this study we find that soot deposition in the lake coincides with the period of increased primary productivity. The Total Organic Carbon and Total Nitrogen were also analyzed and have shown increased remarkable increase with time. All these geochemical variables are a testament to the increased role of human activities on the lake’s productivity. While other studies on soot in marine environments have associated bacterial growth to nutrients attached to soot black carbon. We correlate the concentration of soot in Lake Victoria basin to blooming of cyanobacteria.

80% of Volatile Organic Compounds (VOCs) that are emitted every year to the atmosphere come from biogenic sources (BVOCs), where many different families are included, such as isoprenoids. The production and emission of those compounds is influenced by environmental variables such as light and temperature. Those environmental variables will be affected by global change which has been predicted for the next decades. The main objective of this thesis was to study the effect of global change, and specifically climate change, global warming and eutrophication, on isoprenoid, mono and sesquiterpene contents and emission rates. Moreover, we tested those effects in different families and genotypes, due to the intra and interespecific variability. In order to answer those questions we carried out different experiments, from seminatural conditions to more controlled conditions (lab), because the more control of the environmental sampling parameters the better conditions to study isolated factors. Identification and quantification of both contents and emission was carried out using gas chromatography with mass spectrometry. The main conclusions of the present thesis are: warming and drought increase both terpene content and emission independently of the specie (storing and non-storing species). However, different species responded differently to eutrophication: these responses depended on the species and on the sampling time. Finally, intra and interspecific differences where shown: different genotypes and different species behaved differently in both storing and non-storing species.
Un 80% dels Compostos Orgànics Volaltils (COVs) que s’emeten anualment a l’atmosfera provenen de fonts biogèniques (COVBs), entre els que destaquen diferents famílies com per exemple els isoprenoids. La producció i emissió d’aquests compostos està influenciada per variables ambientals com la llum i la temperatura. Aquestes variables ambientals es veuran afectades pel canvi global que s’ha predit per les properes dècades. L’objectiu de la present tesi va estar estudiar l’efecte del canvi global i específicament canvi climàtic, escalfament i eutrofització, sobre el continguts i les emissions de les famílies isoprenoids, mono i sesquiterpens. A més, varem testar aquests efectes en diferents famílies i genotips, donades les variacions intra i interespecífiques. Per aconseguir resoldre aquestes preguntes varem realitzar diferents experiments, des de condicions seminaturals fins a condicions més controlades (de laboratori), on un major control de les condicions ambientals de mostreig permet estudiar efectes de forma aïllada. La identificació i quantificació dels compostons, tant continguts com emesos, es va fer mitjançant cromatografia de gasos i espectrometria de masses. Les principals conclusions d’aquesta tesis són: l’escalfament i la sequera van incrementar tant el contingut com les emissions de terpens en espècies acumuladores i en espècies no acumuladores. No obstant, les respostes de les diferents espècies a l’eutrofització van ser diverses, depenent de l’espècie i de les condicions ambientals del moment de mostreig. Finalment, es van constatar les diferències intra i interespecífiques: espècies diferents i genotips diferents es van comportar de diferent manera, tant en espècies acumuladores com en espècies no acumuladores.

Eutrophication is a consequence of excess nutrients in the water which leads to increased algaegrowth, reduced water transparency and hypoxic bottoms. This is the biggest environmental problemfor the Baltic Sea which recently has resulted in stricter legislations and other initiatives to help theBaltic Sea to recover. However, the actions to reduce the nutrient input to the Baltic Sea have so farmainly been land-based. These actions seem to not be enough since the eutrophication continues tobe a problem for the Baltic Sea. Farming blue mussels has shown to have a mitigating effect on theeutrophication and could thus be a complementary action. Blue mussels are filter-feeding specieswhich means that they filter water for food and thus eat phytoplankton and accumulate nutrients atthe same time. When the blue mussels are removed from the sea, so is the nutrients accumulated inthe mussels, resulting in a mitigation of nutrients and thereby the eutrophication. Due to the brackishwater with the low salinity in the Baltic Sea, the blue mussels farmed there do not grow bigger thanaround 3 cm. This means that the mussels are not suitable for human food production and theharvested mussels need to be used for something else, even though the farming itself is anenvironmental action. Three possible mussel products from valorisation of the Baltic Sea blue musselshave been identified; producing mussel meal, biogas or compost.Region Östergötland is involved in a project, Baltic Blue Growth, with the main objective to study howto use mussel farming as an environmental measure and which of the three valorisation options is themost beneficial from an environmental perspective. This study is a part of their investigation to reachtheir goal and will study their mussel farm in St. Anna and the three valorisation options from anenvironmental perspective. The aim of this study is thus to investigate the net nutrient reduction froma mussel farm in the Baltic Sea in combination with the contribution to climate change. This is donefrom a life cycle perspective to include the valorisation of the mussels into the different productsmussel meal, biogas or compost. For this, an existing farm in the archipelago of St. Anna, Östergötland,Sweden is studied. The main results show that there is a nutrient reduction from the mussel farm andthis is not majorly affected regardless of which valorisation option that is chosen. However, the musselfarm does have an impact on climate change and the magnitude of the impact varies for the threevalorisation options. The results of the sensitivity analysis show that the result from the life cycle canbe improved with future improvements of the mussel farm and transportation. The nutrient reductioncan become larger and the impact on the climate change can be reduced. Outside the result from thelife cycle analysis it is discussed that there are other future improvement possibilities in the productionof the mussel products, which would impact the result. The mussel farm and the mussel products alsohave other positive impacts that is not included in the life cycle analysis but discussed in the study,such as increased water transparency, recycling of nutrients and reduction of over fishing. However,the mussel farm could also have negative impacts, such as emissions of microplastics and locallyincreased sedimentation which affect the hypoxia. Those are discussed in this study but the probabilityand possible impact of them are not fully investigated and need further research.