Reservoirs are the main drinking water sources in Taiwan. However, about half of 23 reservoirs suffer the eutrophication problems based on the calculated Carlson¡¦s TSI indexes for them. Thus, the reservoir water is seriously polluted. Chen-Ching Lake Reservoir, Fengshan Reservoir, and A-Kong-Tien Reservoir are three major reservoirs that supply water for the domestic, industrial, and agricultural uses in the Kaohsiung area. Due to the long-term sediment deposition at A-Kong-Tien Reservoir, a sediment dredge system is under construction at this reservoir. Thus, only Chen-Ching Lake Reservoir and Fengshan Reservoir play the most important roles in water supply at this moment. However, both Chen-Ching Lake Reservoir and Fengshan Reservoir are in the list of the most eutrophized reservoirs. There are several ways to evaluate the status of eutrophication of reservoirs. The single-index method and multi-variable modeling method are two of the most commonly methods for water quality analysis and eutrophication evaluation for the reservoirs in Taiwan. Based on the analytical results from previous studies, eutrophication results in the fast growing of seaweeds and they spread and cover the whole water bodies, which is called algal bloom. The type of seaweed causing eutrophication in Taiwan reservoirs are mainly Cyanobacteria, especially the commonly found Microcystis. They can not only cause some foul smells but release toxins into the water bodies. That endangers the safety of drinking water and affects the normal water usage. To prevent eutrophication, the nutrients loadings outside and inside of the reservoir areas must be reduced and controlled, which can effectively prohibit the growth of seaweeds. An air-pumping system can also be built for the same purpose. Regular water quality inspection should be carried out to monitor the fluctuation of water quality.

A novel phosphorus (P) adsorbent, ferrihydrite-modified diatomite (FHMD) was developed and characterized in this study. The FHMD was made through surface modification treatments, including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO2 was partially dissolved in the NaOH solution. The dissolved Si contributed to form stable 2-line ferrihydrite, which deposited into the larger mesopores and macropores of the diatomite. The 2-line ferrihydrite not only deposited into the pores of the diatomite but also aggregated on the surface. Filling the larger mesopores and macropores of the diatomite and aggregation on the diatomite surface with 0.24 g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1 m2/g for the FHMD, which is an 8.5-fold increase over the raw diatomite (24.77 m2/g). The surface modification also increased the point of zero charge (pHPZC) values to 10 for the FHMD from 5.8 for the raw diatomite.<p> Effects of the formation process parameters such as concentrations of FeCl2, NaOH, and drying temperature on the formation mechanism and crystalline characteristics of FHMD were studied by using X-ray absorption near-edge structure (XANES) spectroscopy. The spectra were recorded in both the total electron yield (TEY) and the fluorescence yield (FY) modes to investigate the chemical nature of Fe and Si on the surface and in the bulk of ferrihydrite-modified diatomite, respectively. It was found that only the surface SiO2 was partially dissolved in the NaOH solution with stirring and heating, whereas the bulk of diatomite seemed to be preserved. The dissolved Si was incorporated into the structure of ferrihydrite to form the 2-line Si-containing ferrihydrite. The crystalline degree of ferrihydrite increased with the increasing FeCl2 concentration and the Brunauer-Emmett-Teller (BET) specific surface area of FHMD decreased with the increasing FeCl2 concentration. The NaOH solution of higher concentration partially dissolved more surface SiO2 and the crystalline degree of ferrihydrite decreased with the increase in NaOH concentration. The dehydroxylation on the surface of FHMD occurred in the high temperature calcination, causing an energy shift in the Si L-edge spectra to the high energy side and an increase in the crystalline degree of ferrihydrite. In this study, the optimal synthesis conditions for the FHMD with the least crystalline degree and the highest surface area were found to be as the follows: 100 mL of 0.5M FeCl2 solution, 6M NaOH solution and the drying temperature of 50 ºC.<p> Phosphorus adsorption behavior and adsorption mechanism of FHMD were investigated in the research. The Langmuir model best described the P adsorption data for FHMD. Because of increased surface area and surface charge, the maximum adsorption capacity of FHMD at pH 4 and pH 8.5 was increased from 10.2 mg P/g and 1.7 mg P/g of raw diatomite to 37.3 mg P/g and 13.6 mg P/g, respectively. Phosphorus showed the best affinity of adsorption onto FHMD among common anions. K-edge P XANES spectra demonstrate that P is not precipitated with Fe (III) of FHMD, but adsorbed on the surface layer of FHMD.<p> Phosphorus removal from lake water and limiting phosphorus release from sediment by FHMD was examined. Phosphorus removal from lake water proceeded primarily through P adsorption onto the surface of FHMD. When a dose of FHMD of 250 mg/L was applied to lake water, a total phosphorus (TP) removal efficiency of 88% was achieved and a residual TP concentration was 17.0 µg/L which falls within the oligotrophic TP range (3.0-17.7 µg/L). FHMD settled down to the bottom of the 43 cm high cylinder within 6 hours, which suggested that retention time of FHMD in the 5.5 m of Jackfish lake water column was close to the equilibrium time of P adsorption onto FHMD (72 hours). During the 30-day anoxic incubation period, TP concentrations in lake water treated by 400, 500 and 600 mg/L of FHMD showed a slight decrease and maximum TP concentrations remained at levels lower than 15 µg/L. The addition of FHMD resulted in a marked increase in Fe-P fraction, a pronounced decrease in labile-P and organic-P fractions, and stable Al-P, Ca-P and residual-P fractions. The effect of FHMD on limiting P release was comparable with those of the combination of FHMD and alum solutions with logarithmic ratios of Al to mobile P of 0.5 and 0.8. FHMD not only can effectively remove P from lake water but also keep a strong P-binding capacity under anoxic conditions and competition for P with alum at high amounts.<p> The role of gypsum on stabilizing sediment and the optimum dose of gypsum were investigated. The effectiveness of gypsum in stabilizing sediment was proved by the fact that at the same agitation speed, turbidities and soluble reactive P (SRP) concentrations of samples treated with gypsum were much lower than those of sample without gypsum. The optimal thickness of the gypsum layer was found to be 0.8 cm.<p> Combined application of FHMD and gypsum to P control was investigated in the research. It was found in the 30-day incubation of lake water and sediment treated by FHMD and gypsum that no P release seemed to occur regardless of oxic or anoxic conditions. In order to investigate the 120-day effects of FHMD and gypsum on the P control under anoxic and agitation conditions a lab-scale artificial aquarium was established in an environmental chamber. Daily oscillation of a metal grid did not yield the sediment resuspension due to the gypsum stabilization. The combined application of FHMD and gypsum resulted in a 1 g/L increase in the SO42- concentration in the 120-day aquarium compared with that in the control aquarium; however it did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. The addition of FHMD and gypsum enhanced total alkalinity in the 120-day aquarium, thereby improving buffering capacity of lake water. Under anoxic conditions and sediment resuspension conditions, relative to a large increase in total P (TP) concentrations in the control aquarium, TP concentrations in the 120-day aquarium stayed relatively stable, fluctuating within the range of 9.1-13.3 µg/L. Relative to control sediment, Fe-P was significantly enhanced during the 60-day incubation; however, Fe-P did not appear to increase significantly in the second 60-day incubation. Labile-P and organic-P decreased with sediment depths in both control aquarium and test aquariums; however, Al-P, Ca-P and residue-P increased with sediment depth. Lower Al-P is observed in treatment aquariums than in control sediment.<p> As an effective P adsorbent, FHMD showed a high adsorption capacity as well as a significantly higher affinity for P than other anions. A combined application of FHMD and gypsum effectively reduced sediment resuspension and maintained TP levels within the oligotrophic range under anoxic conditions in the laboratory-scale artificial aquarium.

Eutrophication of lakes and streams are nowadays a well known environmental problem and implies an enrichment of the nutrients phosphorus (P) and nitrogen (N). Phosphorus is considered to be the most important component for the growth of aquatic plants and leads in too large quantities to an intensification of growth. Phosphate (PO4) is the fraction of phosphorus that can easiest be taken up by plants and thus have the greatest impact on eutrophication. Increased plant growth in lakes and unfavorable conditions for aquatic animals are two examples of negative consequences. A significant portion of the increased nutrient supply to nearby water can be derived to phosphate leaching from agricultural areas, where private sewers and agriculture is two main sources. How much of the diffuse leakage of phosphate derived from each source is uncertain. With an improved understanding of how the source and flow distribution of phosphate relationship works in an agricultural dominated catchment could a more cost efficient planning for choice of methods against leakage of the nutrient be achieved. The source and flow distribution of phosphate was therefore studied and a high resolution set of SMHI's hydrological model HYPE where set up over the area. Sampling of phosphate from different parts of the area where used together with modeled water flow and phosphate transport where calculated. Upstream and downstream dynamics of phosphate were compared during high water flow. Also sampling of the oxygen isotopic composition in phosphate ions from sewage and agricultural land were analyzed and used to estimate the source distribution at different situations of water flow. The collected information from these studies where used to identify from which source to phosphate and during which flow the leakage of phosphate where the most in the area. In addition to this an evaluation of the importance of the time and space resolution for the HYPE-model where made. Phosphate transports in space shows that the sewage-dominated basins where the areas that leak most phosphate per area unit and during low water flows. Agricultural areas account for more significant leakage during a high water flow. This is evident in autumn and winter and less evident during spring and summer. Oxygen isotopic composition of phosphate ions from wastewater and agricultural land could with a 99 % confidence be separated. This information was used for source separation of phosphate sources where sewage was the main source of water flow up to 23 l/s. At higher water flow increases agricultural land as a primary source and increases positively linearly with increasing water discharge. Both studies indicate that sewage accounts for the greatest leakage during low water. During a snow-melting period the phosphate leaching is highest at the beginning and gradually flushed out from the soil when the water flow remains high for several days in a row. The importance of a high resolution time and space step affected modeled data marginally positive in HYPE where time step had a more important role.

The goal of this work is to contribute to the understanding eutrophication in large rivers with a detailed study of the Grand River, an impacted river in highly agricultural and urbanized Southern Ontario. It focuses on the role of nitrogen (N) and phosphorus (P) in the distribution and abundance of benthic submersed macrophytes, which are important actors in river N and P cycles. Chapter 1 uses data from the Provincial Water Quality Monitoring Network to examine seasonal, long term and spatial patterns in total P (TP), soluble reactive P (SRP), nitrate and nitrite (NO3- + NO2-) and ammonium (NH4+). The monitoring of many sites in the Grand River began in 1965, and I examine data from the period from 1965 to 2009. The monitoring program began prior to the Canada-USA ban on the use of phosphate in detergents, which came into effect in 1973, and also before major improvements to municipal waste water treatment. The phosphate ban is analyzed as an example of a whole-system nutrient manipulation experiment, and the seasonal and long term response of the river system, from headwaters to mouth, is examined. TP and SRP declined over the monitoring period, with the greatest response found in TP, which declined by 120 µg/l/y immediately downstream of the of the watershed’s largest treatment plant in the years 1972-1975. Thereafter, TP and SRP continued to decline over most of the lower river, with rates of decline in nutrient concentration accelerating with distance from the wastewater treatment plants (WWTPs). NO3+NO2 increased during the monitoring period in the upper portion of the river with the highest increase of 158 µg-N/l/y observed in the 10 year period of 1975-1985. It did not change in response to WWTP upgrades that occurred in the early 1970s. WWTPs were a clear source of TP, SRP and NH4+ to the river system, but not NO3 +NO2 , and the continual increase in NO3 +NO2 was due to increases in diffuse sources. The seasonal and spatial data suggest that non-point sources of N and P dominate in the Grand River watershed. However, the largest WWTP in the region at Kitchener is an important source of nutrients, and was an especially large source of P prior to changes in detergent standards and wastewater treatment. The submersed macrophyte biomass in the Grand River was examined as a function of proximity to WWTPs in chapter 2. Spatial surveys were conducted in 2007 and 2009 on three reaches of approximately 10 km in length each, with two reaches having an upstream and downstream section, separated by a WWTP. Macrophyte patches were mapped, biomass was estimated, and plants were analyzed for N and P. Tissue N and P were compared to published thresholds for evidence of nutrient limitation. Biomass was greater downstream of the WWTPs than upstream in both reaches and both years, indicating that nutrient loading leads to increased biomass downstream, evidence that even in a heavily agricultural watershed, point sources have a demonstrable effect on macrophyte biomass. Depth was important in explaining some of the variation, while river width and orientation were not important. Even though macrophyte biomass was elevated downstream of the WWTPs, there was no strong evidence of N or P limitation upstream based on tissue concentrations and a laboratory determined critical nutrient threshold, and I hypothesize that the nutrient limitation affecting biomass occurs earlier in the growing season, before peak biomass. This suggests that the eutrophication process in rivers is distinct from that in lakes, and future work should view eutrophication in rivers in the context of seasonal succession. Drivers of seasonal and inter-annual variability in submersed macrophyte biomass were examined in chapter 3 with a multi-year, reach-scale spatial survey of three reaches near the WWTPs of Waterloo and Kitchener. Biomass differed among reaches, years and sites, and showed distinct seasonal patterns. The reach downstream of the WWTPs had the highest biomass, and peak biomass came soonest in the growing season, while the upstream reach had the smallest and latest peak biomass. Weather was significantly correlated to both the quantity and the time of the peak biomass, with higher temperatures associated with larger and earlier peak biomass and precipitation and higher flow associated with later and lower peak biomass. Therefore, the eutrophication response in rivers can depend on weather, and these drivers of variation should be accounted for when forecasting responses to future changes in nutrient loading. The effect of nitrogen discharged by WWTPs on the riverine submersed macrophyte community, and the suitability of macrophyte tissues as indicators of point source impact, were quantified in chapter 4 using δ15N as a tracer of WWTP effluent impact. Macrophytes and water for NO3- and NH4+ concentration and isotope analysis was collected by canoe along two 10 km reaches of the river, up and downstream of two WWTPs. Macrophytes incorporated effluent nitrogen into their tissues downstream of the WWTPs, using effluent NH4+ rather than NO3-. Impacts of the effluent on macrophytes can be traced as far as 10 km downstream, while daytime chemical evidence of the plume disappeared much sooner. The δ15N-NH4+ value rapidly increased downstream of the WWTP, changing in one instance from +13‰ to +31‰ over 1 km, with macrophyte δ15N values changing from +6‰ to +24‰ over 5 km, while δ15N- NO3- values showed no such change. These data lead to the conclusion that riverine submersed macrophytes record the influence of WWTP effluent, specifically effluent NH4+, but that using two end-member mixing models to determine N sources would be inappropriate in such dynamic environments. Nitrogen cycle processes such as nitrification and denitrification are influenced by dissolved oxygen (DO) and rapid transformations occur in environments with strong DO gradients. Because development of dense macrophyte beds in eutrophic rivers has the potential to greatly alter daily oxygen cycling, producing strong redox potentials, macrophytes could influence microbial nitrogen cycling. In Chapter 5, nitrogen uptake by macrophytes using a 15N-NH4+ tracer and N2O production was investigated using in situ chamber incubations upstream and downstream of a WWTP. NH4+ uptake occurred in chambers, while measurable net N2O production occurred in some chambers only. Neither N2O production nor NH4+ uptake differed between chambers with and without PO43- addition, nor did they differ between light and dark treatments. NH4+ uptake was higher at the upstream site, indicating that above the WWTP there was NH4+ demand in the macrophyte community. NH4+ uptake was a hyperbolic function of mean chamber NH4+ concentration. Turnover time for the macrophyte N pool due to NH4+ uptake was as long as 47 d, while the turnover of the dissolved NH4+ pool was as rapid as 14 h. Because net uptake was a small fraction of gross uptake, calculated release rates were almost as high as uptake rates, again indicating rapid NH4+ cycling. Eutrophication of rivers has elements that make it a process distinct from that in lakes. I showed that, in the Grand River, N and P were both high in concentration throughout the river, with a distinct increase downstream of the largest WWTPs in the watershed. The biomass of benthic submersed macrophytes was elevated below the WWTPs, but there was no evidence of nutrient limitation upstream during the time of peak biomass. Macrophyte biomass development followed a seasonal pattern, but was also influenced by seasonal temperature and precipitation patterns. Thus, the riverine eutrophication process has an important seasonal component, much as the plants themselves do, peaking in the summer and senescing in the fall. As part of the eutrophication response, macrophytes altered the chemical cycles of nutrients that fuel their growth. Though changes in benthic biomass themselves are part of riverine eutrophication, this thesis provides evidence that changes in macrophyte biomass produces chemical and ecological changes that are characteristic of increased trophic conditions.

A novel phosphorus (P) adsorbent, ferrihydrite-modified diatomite (FHMD) was developed and characterized in this study. The FHMD was made through surface modification treatments, including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO2 was partially dissolved in the NaOH solution. The dissolved Si contributed to form stable 2-line ferrihydrite, which deposited into the larger mesopores and macropores of the diatomite. The 2-line ferrihydrite not only deposited into the pores of the diatomite but also aggregated on the surface. Filling the larger mesopores and macropores of the diatomite and aggregation on the diatomite surface with 0.24 g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1 m2/g for the FHMD, which is an 8.5-fold increase over the raw diatomite (24.77 m2/g). The surface modification also increased the point of zero charge (pHPZC) values to 10 for the FHMD from 5.8 for the raw diatomite.<p> Effects of the formation process parameters such as concentrations of FeCl2, NaOH, and drying temperature on the formation mechanism and crystalline characteristics of FHMD were studied by using X-ray absorption near-edge structure (XANES) spectroscopy. The spectra were recorded in both the total electron yield (TEY) and the fluorescence yield (FY) modes to investigate the chemical nature of Fe and Si on the surface and in the bulk of ferrihydrite-modified diatomite, respectively. It was found that only the surface SiO2 was partially dissolved in the NaOH solution with stirring and heating, whereas the bulk of diatomite seemed to be preserved. The dissolved Si was incorporated into the structure of ferrihydrite to form the 2-line Si-containing ferrihydrite. The crystalline degree of ferrihydrite increased with the increasing FeCl2 concentration and the Brunauer-Emmett-Teller (BET) specific surface area of FHMD decreased with the increasing FeCl2 concentration. The NaOH solution of higher concentration partially dissolved more surface SiO2 and the crystalline degree of ferrihydrite decreased with the increase in NaOH concentration. The dehydroxylation on the surface of FHMD occurred in the high temperature calcination, causing an energy shift in the Si L-edge spectra to the high energy side and an increase in the crystalline degree of ferrihydrite. In this study, the optimal synthesis conditions for the FHMD with the least crystalline degree and the highest surface area were found to be as the follows: 100 mL of 0.5M FeCl2 solution, 6M NaOH solution and the drying temperature of 50 ºC.<p> Phosphorus adsorption behavior and adsorption mechanism of FHMD were investigated in the research. The Langmuir model best described the P adsorption data for FHMD. Because of increased surface area and surface charge, the maximum adsorption capacity of FHMD at pH 4 and pH 8.5 was increased from 10.2 mg P/g and 1.7 mg P/g of raw diatomite to 37.3 mg P/g and 13.6 mg P/g, respectively. Phosphorus showed the best affinity of adsorption onto FHMD among common anions. K-edge P XANES spectra demonstrate that P is not precipitated with Fe (III) of FHMD, but adsorbed on the surface layer of FHMD.<p> Phosphorus removal from lake water and limiting phosphorus release from sediment by FHMD was examined. Phosphorus removal from lake water proceeded primarily through P adsorption onto the surface of FHMD. When a dose of FHMD of 250 mg/L was applied to lake water, a total phosphorus (TP) removal efficiency of 88% was achieved and a residual TP concentration was 17.0 µg/L which falls within the oligotrophic TP range (3.0-17.7 µg/L). FHMD settled down to the bottom of the 43 cm high cylinder within 6 hours, which suggested that retention time of FHMD in the 5.5 m of Jackfish lake water column was close to the equilibrium time of P adsorption onto FHMD (72 hours). During the 30-day anoxic incubation period, TP concentrations in lake water treated by 400, 500 and 600 mg/L of FHMD showed a slight decrease and maximum TP concentrations remained at levels lower than 15 µg/L. The addition of FHMD resulted in a marked increase in Fe-P fraction, a pronounced decrease in labile-P and organic-P fractions, and stable Al-P, Ca-P and residual-P fractions. The effect of FHMD on limiting P release was comparable with those of the combination of FHMD and alum solutions with logarithmic ratios of Al to mobile P of 0.5 and 0.8. FHMD not only can effectively remove P from lake water but also keep a strong P-binding capacity under anoxic conditions and competition for P with alum at high amounts.<p> The role of gypsum on stabilizing sediment and the optimum dose of gypsum were investigated. The effectiveness of gypsum in stabilizing sediment was proved by the fact that at the same agitation speed, turbidities and soluble reactive P (SRP) concentrations of samples treated with gypsum were much lower than those of sample without gypsum. The optimal thickness of the gypsum layer was found to be 0.8 cm.<p> Combined application of FHMD and gypsum to P control was investigated in the research. It was found in the 30-day incubation of lake water and sediment treated by FHMD and gypsum that no P release seemed to occur regardless of oxic or anoxic conditions. In order to investigate the 120-day effects of FHMD and gypsum on the P control under anoxic and agitation conditions a lab-scale artificial aquarium was established in an environmental chamber. Daily oscillation of a metal grid did not yield the sediment resuspension due to the gypsum stabilization. The combined application of FHMD and gypsum resulted in a 1 g/L increase in the SO42- concentration in the 120-day aquarium compared with that in the control aquarium; however it did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. The addition of FHMD and gypsum enhanced total alkalinity in the 120-day aquarium, thereby improving buffering capacity of lake water. Under anoxic conditions and sediment resuspension conditions, relative to a large increase in total P (TP) concentrations in the control aquarium, TP concentrations in the 120-day aquarium stayed relatively stable, fluctuating within the range of 9.1-13.3 µg/L. Relative to control sediment, Fe-P was significantly enhanced during the 60-day incubation; however, Fe-P did not appear to increase significantly in the second 60-day incubation. Labile-P and organic-P decreased with sediment depths in both control aquarium and test aquariums; however, Al-P, Ca-P and residue-P increased with sediment depth. Lower Al-P is observed in treatment aquariums than in control sediment.<p> As an effective P adsorbent, FHMD showed a high adsorption capacity as well as a significantly higher affinity for P than other anions. A combined application of FHMD and gypsum effectively reduced sediment resuspension and maintained TP levels within the oligotrophic range under anoxic conditions in the laboratory-scale artificial aquarium.

Phosphorus flowing via rivers into the Baltic Sea is a major source of nutrients, and in some cases the limiting factor for the growth of algae which causes the phenomenon known as eutrophication. Remote sensing of phosphorus, here using Landsat TM-data, can help to give a better understanding of the process of eutrophication. Since Landsat TM-data is used, this could form a basis for further spatio-temporal analysis in the Baltic Sea region. A method originally described and previously applied for a Chinese river is here transferred and applied to three different rivers flowing into the Baltic Sea. The results show that by measuring the proxy variables of Secchi Depth and Chloryphyll-a the remote sensing model is able to explain 41% of the variance in total- phosphorus for the rivers Dalälven, Norrström and Gavleån without any consideration taken to CDOM, turbidity or other local features.

In recent years new ideas for nutrient management to control eutrophication in estuarine environments have been under consideration. One popular approach being considered in the Chesapeake Bay Program is called the “top down” approach based on the premise that restoring algal predators, such as oysters and menhaden, will limit excess phytoplankton production and possibly eliminate costly nutrient control programs. The approach is being considered to replace or use in conjunction with the “bottom up” approach of reducing nutrient loads. The ability to model higher trophic levels such as fish, as well as the eutrophication processes driving production of primary producers in an aquatic ecosystem is needed. CE-QUAL-ICM (ICM) and Ecopath were two models selected for this research. ICM is a time- and spatial-varying eutrophication model that uses nutrient loads to predict primary producers, while Ecopath is a static mass balance model representing an average time period (e.g., season or year) and uses values of primary producers and other groups to predict fish biomass. Linking the two models will provide the means of going up the food chain by trophic levels. The Chesapeake Bay was chosen as the study site since both models are in use there. Before coupling ICM and Ecopath, common links between the two models were found. Ten groups were identified with such variables as production rates, consumption rates, and unassimilated food/consumption. A post-processor/subroutine was developed for ICM to aggregate output data from 3-D to 0-D to be used in Ecopath. Two Ecopath runs were developed with data from ICM and the Chesapeake Bay (CB) Ecopath model to see how network interactions differed with data representing the same system. Four additional runs were made, creating perturbations (i.e., increased phytoplankton production) using the CB Ecopath model and replacing the primary producers with data from ICM. Final runs of ICM were conducted looking at adjusting three parameters to try to restore the Bay back to 1950 conditions. It was demonstrated that ICM data can be coupled with Ecopath to study management strategies in eutrophication. Because of model formulations there was no data exchange from Ecopath back to ICM.

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Eutrophication due to enhanced nutrient concentrations can affect marine communities by altering the species composition of macroalgae and marine invertebrates, where certain species have shown tendencies to increase. The aim with this study was to assess how the species composition changed in relation to the distance from a nutrient enriched stream discharge. The study was conducted in an area with rocky shores and Fucus vesiculosus as the dominant alga, and also included the mouth of the eutrophic stream Kvarnabäcken. Macroalgae and invertebrate abundance was examined in eight locations (including an unaffected reference location) at different distances from the mouth of Kvarnabäcken. The concentrations of total nitrogen and total phosphorus were measured in the marine locations as well as in the stream. Although Kvarnabäcken displayed elevated nutrient concentrations, no distinct nutrient gradient was detected in the marine locations due to distance from the stream. The abundance of invertebrates and macroalgae varied to some extent in the locations, where the location in the immediate mouth area showed most differences, which contributed to the conclusion that the direct impact of nutrient discharge is limited. Although there are aspects indicating that the alterations in animal and algae abundance are consequences of nutrient discharge, other factors that regulate community composition must be considered when evaluating eutrophication in marine communities. / Övergödning kan påverka marina samhällen genom att artsammansättningen av makroalger och marina evertebrater ändras till följd av förhöjda närsalter, bland annat genom att vissa arter tenderar att öka i förekomst. Syftet med denna studie var att undersöka om artsammansättningen av marina evertebrater förändrades i relation till avståndet från ett utsläpp från en bäck med förhöjda närsaltkoncentrationer. Studien utfördes i ett område med klippiga stränder och Fucus vesiculosus som den dominerande algen och inkluderade även mynningen av den övergödda bäcken Kvarnabäcken. Förekomst av makroalger och evertebrater undersöktes i åtta lokaler (en opåverkad referenslokal inkluderad) längs kusten på varierande avstånd från bäcken. Koncentrationerna av totalkväve och totalfosfor mättes i de marina lokalerna och i bäcken. Trots att Kvarnabäcken visade höga halter av närsalter, visade inte resultatet någon tydlig näringsgradient från bäcken, medan det fanns en antydan till förändrad förekomst av evertebrater och alger i lokalerna. Lokalen närmast utsläppet skiljde sig något från övriga, vilket kan indikera att den direkta påverkan av näringstillförsel kan vara begränsat. Därtill är det viktigt att understryka att även om skillnader i förekomst av evertebrater och alger i lokalerna kan bero på närsalter från bäcken måste övriga faktorer tas hänsyn till vid undersökningar av marina samhällen.

The aim of this literature study is to compare and discuss different fields of paleolimnology, with a focus on three main research areas – eutrophication, acidification, and climate change. Pioneering work and the development of paleolimnological methods around these three areas were reviewed and synthesized. Paleolimnology started out as limnology and paleoecology, but has evolved tremendously over the past decades. Early paleolimnological studies focused on lake ontogeny and mechanics in the catchment such as weathering. The focus eventually shifted to nutrient loadings during the 1960s – 1970s as the debate on human induced eutrophication emerged. The important question to answer was which nutrient was the limiting factor in eutrophication. Acidification was the next topic of investigation during the 1980s – 1990s, and paleolimnology developed methods to infer past pH change based on chironomids and diatom fossils preserved in lake sediment. This research resulted in calibration sets and proxies which can be used to reconstruct past conditions. The paleolimnological community eventually shifted focus in the late 1990s to climate change and began to use lake sediment to reconstruct past climatic trends using multiproxy studies such as diatoms, chironomids and geochemistry. Varved lake sediment offered a much needed terrestrial high resolution option to the ice core records. History plays a fundamental role in all environmental issues and paleolimnology has the ability to provide historical records of past environmental conditions. Paleolimnology will most likely play a key role in management and restoration in the future. As technology and training sets develop, fast and cheap ways to interpret sediment proxies will emerge and maybe even fully automated identification of proxies.