The effects of increasing nitrogen and phosphorus loading on submerged macrophyte development was tested in a mesocosm experiment for three months. Experiment consisted of three NO3-N loadings with factorial of two PO4-P loadings in a fourfold replicated design. Twenty four enclosures placed at one meter depth were isolated from the lake but kept open to sediment and atmosphere. Each enclosure stocked with ten Myriophyllum spicatum shoots with underyearling fish to reduce zooplankton grazers. Biweekly sampling and weekly nutrient additions were performed for three months. Mean total nitrogen (TN) concentrations sustained in nitrogen treatments through out the experiment were 0.52, 1.99, 8.07 mg/l. Both phosphorus treatments converged to a mean concentration below the targeted level, ranging between 0.05-0.1 mg/l TP. In comparison to mesocosm studies in temperate lakes, higher assimilation rates for nutrients were observed in Lake Pedina. Due to extraordinarily high evapotranspiration and drought in 2007, the water level decreased 0.6 m in enclosures. Total macrophyte biomass remained indifferent to nutrient treatments with continuous growth and failed to validate any direct or indirect negative effect of increasing nutrient concentrations. Phytoplankton biomass differed significantly among factorial treatments but remained low, while periphyton biomass differed among nitrogen treatments. In comparison with other studies the phytoplankton biomass remained low and the periphyton biomass became high for reference TP concentrations, indicating a competitive advantage of periphyton over phytoplankton on nutrient utilization in the enclosures. Zooplankton:phytoplankton biomass ratio was low throughout the experiment and zooplankton community mainly consists of smaller species, reflecting high predation pressure.

A mesocosm experiment was conducted in Lake Eymir between June &ndash / September 2009 in order to elucidate the effects of water level changes and fish predation on periphyton growth and macroinvertebrates in semi-arid shallow lakes. Twenty four cylindrical enclosures, each with 1.2 m diameter, open to lake bottom and atmosphere, were placed at three different depths, i.e. 0.8 m (low water level, LW), 1.6 m (high water level, HW) and 2.3 m (however, data regarding the enclosures at 2.3 m were excluded in this study due to complications after fifth sampling) to simulate water level fluctuations. At each water level, four replicates were stocked with omnivorous&ndash / planktivorous fish (Tinca tinca and Alburnus escherichii) and the other four replicates were left fishless to observe the effect of fish predation. Ten shoots of submerged macrophytes (Potamogeton pectinatus) were planted and six polyethylene strips were hung in the water column in each enclosure to monitor macrophyte and periphyton growth. The mesocosms were sampled for physical, chemical and biological parameters weekly in the first month and fortnightly thereafter. Benthic macroinvertebrate samples were taken before the start, in the middle and at the end of the experiment with Kajak corer. Macrophytes were harvested after the last sampling for determination of dry weight, epiphyton, and the associated macroinvertebrates. All macroinvertebrate samples were sieved through 212 &mu / m mesh size before identification and counting. Over the course of the experiment, an average of 0.46 &plusmn / 0.03 m water level decrease in the mesocosms triggered submerged macrophyte growth in all LW enclosures, overriding the negative effects of fish predation. The results indicate that while fish predation pressure had negative influences on macroinvertebrate communities in terms of both abundance and richness, structural complexity created by dense vegetation in the LW mesocosms weakened the top-down effect of fish on macroinvertebrates by acting as a refuge in this semi-arid shallow lake.

Cattle farming is vital to the economy of the United States. Frequently, cattle are given access to ponds and streams for water. The relative impacts of cattle access in natural water sources on the periphyton community have been rarely investigated. Periphyton is the basis of the aquatic food web, and community composition can serve as a bioindicator of pollution. Thus, my objectives were to quantify the effects of cattle access in aquatic lentic systems on periphyton community structure and biovolume, identify taxa that were associated with cattle access, and identify abiotic mechanisms that might be driving assemblage changes. I conducted my research in 4 cattle-access (CA) and 4 no-access (NA) farm ponds on the University of Tennessee Plateau Research and Education Center from May 2005 – April 2006. Periphyton community composition and water quality were measured every 2 weeks using standard environmental monitoring procedures. I documented 181 new periphyton taxonomic records (7 phyla, 52 families, and 132 genera) in Cumberland County, Tennessee. Periphyton species richness was greatest in NA ponds. Mean biovolume of pollution-sensitive diatoms (e.g., Achnanthidium minutissimum, Cymbella sp., Eunotia sp., Fragilaria crotonensis and Tabellaria fenestrata) was greater in NA ponds. In contrast, pollution-tolerant diatoms (e.g., Gomphonema sp. and Navicula sp.) and non-diatoms (e.g., Oscillatoria sp. and Scenedesmus sp.) were more abundant in CA ponds. Turbidity, pH, conductivity, and concentrations of the total Kjeldahl nitrogen, total phosphorus, potassium, periphyton phosphorus, silicon, iron, magnesium and aluminum were greater in CA ponds. Thus, changes in water quality associated with cattle-access likely mediated changes in the periphyton community. Considering that changes in periphyton community composition can destabilize higher trophic levels, I recommend that cattle farmers take advantage of USDA conservation programs that provide funds for fencing cattle from watersheds and developing alternate water sources. My results also provide evidence that monitoring the periphyton community is a reliable technique to detect water pollution from cattle.

Dietary cadmium (Cd) can contribute significantly to chronic bioaccumulation and toxicity in aquatic organisms. This contribution needs to be quantified so that the relative importance of waterborne and dietary cadmium exposure pathways can be incorporated into protective water quality guidelines and ecological risk assessments. In this research, the contribution of dietary Cd from a natural periphyton diet to chronic (28 d) bioaccumulation and toxicity in the freshwater amphipod Hyalella azteca was quantified using a mechanistically-based saturation bioaccumulation model. Factors that influence dietary Cd bioavailability such as food type, food form, dietary Cd speciation and concentration were investigated. Assimilation efficiency, ingestion rate and the excretion rate constant of dietary Cd were determined for each of these factors. Food nutrition was also considered. Lastly, model predictions of Cd bioaccumulation and toxicity were compared to measurements of tissue concentration and survival when H. azteca were exposed to metal contaminated water and periphyton collected from lakes in the metal mining region of Rouyn-Noranda, Quebec, Canada. In 28 d laboratory experiments where H. azteca bioaccumulated Cd from water and food, dietary Cd was estimated to contribute markedly (21 – 94 %) to bioaccumulated Cd in H. azteca. Effects on chronic survival were best predicted from body concentration rather than water or food exposure concentration. Assimilation efficiency of dietary Cd differed with food type likely as a result of Cd speciation, but did not differ with Cd concentration or food form. Ingestion rate differed with food form while excretion rate constants were unaffected by dietary Cd bioavailability. Predictions of chronic Cd bioaccumulation in H. azteca exposed to field contaminated samples were robust, however the model did not account for effects of water chemistry on Cd bioaccumulation and is thus constrained in its application. Predictions of chronic survival were over-estimated likely due to the additional toxicity caused by the low nutritional quality of the field contaminated periphyton. This research demonstrated that both waterborne and dietary Cd need to be considered in models that assess chronic risk of exposure and effects to H. azteca.

No description available.

Acid mine drainage (AMD) is a major environmental issue worldwide. On the West Coast of the South Island, New Zealand, numerous catchments receive AMD, with significant negative impacts on in-stream flora and fauna. Diatoms are commonly regarded as powerful biological indicators and may be found in high abundance in AMD-contaminated streams; however, relatively little work has been done on diatoms in mining environments in New Zealand. Initially, I conducted a survey of epiphytic diatom communities in 39 streams ranging from non-impacted reference streams to those severely impacted by AMD. Streams were assigned to one of four classes along an AMD gradient: circum-neutral reference, naturally acidic reference, moderately impacted, and severely impacted. There was a wide range in diatom taxonomic richness in reference and moderately impacted streams (8 – 33 taxa). Taxonomic richness was greatly reduced in severely impacted streams (1 – 5 taxa) at a threshold of pH 3.4 and was dominated by Pinnularia cf. acidophila (69 – 100% relative abundance). Community composition differed between circum-neutral reference, moderately, and severely impacted streams; however, naturally acidic and moderately impacted streams had similar diatom communities primarily composed of acid-tolerant Eunotia and Frustulia species. This indicated that diatoms are strongly structured by pH and able to tolerate moderate conductivity and metal concentrations without a corresponding shift in community composition. Survey data were then used to develop two diatom-based indices for streams impacted by AMD: a single Biotic Index and a Multimetric Index. While neither index was able to distinguish naturally acidic from moderately impacted streams, both indices successfully categorised streams as circum-neutral reference, moderately or severely impacted by AMD. These indices may be useful in assessing AMD impact on circum-neutral streams or in identifying when a stream has crossed a threshold from moderately to severely impacted by AMD. Diatoms would be especially useful as bioindicators of AMD if they respond rapidly to a change in mine discharge. To test this, mature algal biofilms were reciprocally transferred between circum-neutral reference streams and streams of varying degrees of AMD over a period of 13 days. Diatom mortality increased rapidly in the reciprocal transfer between reference and severely impacted streams. Reference communities resembled the ambient diatom community of severely impacted streams 13 days post-transfer. However, in the reverse transfer, a change in community composition was slow to occur. Diatoms respond faster to an increase in pollution than to pollution amelioration. Overall, results indicated that diatom communities may be a useful tool for monitoring the presence and magnitude of AMD in New Zealand streams.

The aim of this thesis was to identify general structuring mechanisms in benthic food webs within the framework of ecological stoichiometry theory. Ecological stoichiometry is defined as the balance of multiple chemical substances in ecological interactions and explicitly considers the combined dynamics of key elements such as carbon (C), nitrogen (N) and phosphorus (P). Ecological stoichiometry theory was developed for pelagic environments, thus it must be tested whether the same mechanisms are applicable to benthic environments. In this thesis, ecological stoichiometry theory was used as a framework to investigate nutrient pathways in benthic littoral ecosystems. I conducted one invertebrate field sampling and six experiments. In the experiments, factors such as grazing, light, nutrients and fish presence were manipulated. The results showed that stoichiometric variability in consumers could mostly be explained by taxa. However, there was some stoichiometric variability due to sampling season, site, and nutrient enrichment. Grazing mostly increased periphyton N and P content, although nutrient recycling effects were dependent on grazer stoichiometry. Grazing changed benthic algal community composition by increasing the proportion of grazing resistant algae species. Additionally, grazing decreased algal diversity, especially under nutrient poor conditions. The manipulation of fish presence revealed that fish affected primary producer biomass and stoichiometry through nutrient recycling. The manipulation of abiotic factors, such as light and nutrient addition could affect periphyton nutrient content, biomass and benthic algal chlorophyll a content. The separate addition of N or P led to an increase of the added nutrient in the periphyton. Increased light intensities led to a decreased cellular chlorophyll a content and increased C:nutrient ratios. This thesis arrives at the conclusion that periphyton-grazer-predator interactions in the benthic are bound by stoichiometric constraints. Nutrient recycling by benthic invertebrates and fish are important mechanism in benthic littoral ecosystems.

Thesis (M.S.)--Ohio University, August, 2006. / Title from PDF t.p. Includes bibliographical references.

Thesis (M. Sc.)--University of Canterbury, 2007. / Typescript (photocopy). "June 2007." Includes bibliographical references (leaves 83-94). Also available via the World Wide Web.

Orientador: Viviane Moschini Carlos / Coorientador: Albano Geraldo Emílio Magrin / Banca: Renata Fracacio / Banca: Eduardo Luiz de Oliveira / Resumo: O reservatório de Itupararanga representa grande importância na bacia hidrográfica do rio Sorocaba devido aos usos múltiplos que este ecossistema propicia à população. Dentre as diversas atividades que usufruem dos serviços ambientais desse reservatório, podemos citar o abastecimento de água potável, irrigação, recreação, navegação e turismo. Dessa forma, o presente estudo objetivou estudar os estoques de carbono e as relações da comunidade periférica (biomassa e composição específica) com a qualidade da água no reservatório de Itupararanga. Para isso, foram realizadas cinco campanhas de amostragem em quatro estações amostrais ao longo do reservatório em duas espécies de macrófitas aquáticas. A biomassa perifitica aderida às raízes da macrófita aquática. Eichhornia spp. apresentou variação de 0,9 mg.m2 a 12,5 mg.m2 e a biomassa perifitica aderida às raízes da macrófita aquática Polygonum punctatum apresentou variação de 0,5 mg.m2 a 3,9 mg.m2 e mostraram-se controladas principalmente pelo regime hidrológico e pelas concentrações de nutrientes na água. Os estoques de carbono da comunidade perifitica aderida às raízes de Eichhornia spp. e nos pecíolos de P. punctatum variaram de 0,3 mgC.m2 a 2,5 mgC.m2 e 0,1 mgC.m2 a 1,2 mgC.m2 respectivamente. Já em relação à composição específica de algas perifiticas, foi encontrado um total de 156 táxons divididos em 8 classes e a densidade total das espécies variou de 10,2 mil a 171,8 mil indivíduos por milímetro quadrado. Em relação à qualidade da água, o reservatório de Itupararanga apresentou em diversas momentos concentrações acima do máximo permitido para fósforo total e abaixo do mínimo permitido para oxigênio dissolvido segundo a resolução CONAMA 357/2005. A comunidade de algas perifíticas mostrou-se controlada por... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Itupararanga reservoir has great importance in the Sorocaba River basin due to the multiple uses that uses that this ecosystem provides to the population. Among the many activities that take benefit of the environmental services from this reservoir, we can cite the drinking water supply, irrigation, recreation, navigation and tourism. Therefeore, this study aimed to study the carbon stocks and the relationships of the periphytic community (biomass and species composition) with the quality of the water in the reservoir Itupararanga. For this, five sampling campaigns in four sampling stations along the reservoir in two species of aquatic macrophytes were performed. The periphyton biomass attached to the roots of the aquatic macrophyte Eichhornia spp. presented a variation of 0.9 mg.m2 to 12,5 mg.m2 and periphyton biomass attached to the aquatic macrophyte Polygomum punctatum showed variation of 0,5 mg.m2 to 3.9 mg.m2 and were controleed mainly by the hydrological regime and nutrient concentrations in the water. The periphytic community carbon stocks attached to the roots of eichhornia spp. and the petioles of P. punctatum ranged from 0.3 mgC.m2 to 2.5 mgC.m2 and 0.1 mgC.m2 to 1.2 mgC.m2 respectively. In relation to the species composition of periphytic algae, it has been found a total of 156 taxa divided into eight classes and the overall density of the species ranged from 10,200 to 171,800 individuals per square millimeter. In relation to the water quality, the Itupararanga reservoir performed in several times above the maximum allowed concentrations for total phosphorus and below the minimum allowable concentrations for dissolved oxygen according to CONAMA 357/2005 resolution. The community of periphytic algae has shown to be controlled by spatial and temporal patterns, such as substrate type, the sampling stations... (Complete abstract click electronic access below) / Mestre