Occurrence and distribution of novel botryococcene hydrocarbons in freshwater wetlands of the Florida Everglades

A high abundance of isoprenoid hydrocarbons, the botryococcenes, with carbon numbers from 32 to 34 were detected in the Florida Everglades freshwater wetlands. These compounds were present in varying amounts up to 106 μg/gdw in periphyton, 278 μg/gdw in floc, and 46 μg/gdw in soils. Their structures were determined based on comparison to standards, interpretation of their mass spectra and those of their hydrogenation products, and comparison of Kovats indexes to those reported in the literature. A total of 26 cyclic and acyclic botryococcenes with 8 skeletons were identified, including those with fewer degrees of unsaturation, which are proposed as early diagenetic derivatives from the natural products. This is the first report that botryococcenes occur in the Everglades freshwater wetlands. Their potential biogenetic sources from green algae and cyanobacteria were examined, but neither contained botryococcenes. Thus, the source implication of botryococcenes in this ecosystem needs further study.

The White Ibis and Wood Stork as indicators for restoration of the everglades ecosystem

Large numbers of colonially nesting herons, egrets, ibises, storks and spoonbills were one of the defining natural phenomena of the historical Everglades. Reproduction of these species has been tracked over at least a century, and some clear responses to dramatic anthropogenic hydrological alterations have been established. These include a marked decline in nesting populations of several species, and a movement of colonies away from the over-drained estuarine region. Ponding in a large portion of the freshwater marsh has favored species that hunt by sight in deep water (egrets, cf. 25–45 cm), while tactile feeders (ibises and storks) that depend on concentrated prey in shallow water (5–25 cm) have become proportionately much less common. There has been a marked increase in the interval between exceptionally large breeding aggregations of White Ibises (Eudocimus albus). Loss of short hydroperiod wetlands on the margins of the Everglades have delayed nest initiations 1–2 months by Wood Storks (Mycteria americana) resulting in poor nesting success. These responses are consistent with mechanisms that involve foraging, and the availability and production of prey animals, and each of the relationships is highly dependent on hydrology. Here, we define a group of characteristics about wading bird dynamics (= indicators) that collectively track the specific ecological relationships that supported ibises and storks in the past. We suggest four metrics as indicators of restoration success: timing of nesting by storks, the ratio of nesting ibises + storks to Great Egrets, the proportion of all nests located in the estuarine/freshwater ecotone, and the interval between years with exceptionally large ibis nestings. Each of these metrics has historical (e.g., predrainage) data upon which to base expectations for restoration, and the metrics have little measurement error relative to the large annual variation in numbers of nests. In addition to the strong scientific basis for the use of these indicators, wading birds are also a powerful tool for public communication because they have strong aesthetic appeal, and their ecological relationships with water are intuitively understandable. In the interests of communicating with the public and decision-makers, we integrate these metrics into a single-page annual “traffic-light” report card for wading bird responses. Collectively, we believe these metrics offer an excellent chance of detecting restoration of the ecosystem functions that supported historical wading bird nesting patterns.

Dynamics of ecosystem metabolism and flocculent detritus transport in estuarine Taylor River

Estuaries and estuarine wetlands are ecologically and societally important systems, exhibiting high rates of primary production that fuel offshore secondary production. Hydrological processes play a central role in shaping estuarine ecosystem structure and function by controlling nutrient loading and the relative contributions of marine and terrestrial influences on the estuary. The Comprehensive Everglades Restoration Plan includes plans to restore freshwater delivery to Taylor Slough, a shallow drainage basin in the southern Everglades, ultimately resulting in increased freshwater flow to the downstream Taylor River estuary. The existing seasonal and inter-annual variability of water flow and source in Taylor River affords the opportunity to investigate relationships between ecosystem function and hydrologic forcing. Estimates of aquatic ecosystem metabolism, derived from free-water, diel changes in dissolved oxygen, were combined with assessments of wetland flocculent detritus quality and transport within the context of seasonal changes in Everglades hydrology. Variation in ecosystem gross primary production and respiration were linked to seasonal changes in estuarine water quality using multiple autoregression models. Furthermore, Taylor River was observed to be net heterotrophic, indicating that an allochthonous source of carbon maintained ecosystem respiration in excess of autochthonous primary production. Wetland-derived detritus appears to be an important vector of energy and nutrients across the Everglades landscape; and in Taylor River, is seasonally flushed into ponded segments of the river where it is then respired. Lastly, seasonal water delivery appears to govern feedbacks regulating water column phosphorus availability in the Taylor River estuary.

Chemical characteristics of dissolved organic matter in an oligotrophic subtropical wetland/estuarine ecosystem

Fluorescence properties of whole water samples and molecular characteristics of ultrafiltrated dissolved organic matter (UDOM > 1,000 D) such as lignin phenol and neutral sugar compositions and 13C nuclear magnetic resonance (NMR) spectra were determined along a freshwater to marine gradient in Everglades National Park. Furthermore, UDOM samples were categorized by hierarchical cluster analysis based on their pyrolysis gas chromatography/mass spectrometry products. Fluorescence properties suggest that autochthonous DOM leached/exuded from biomass is quantitatively important in this system. 13C NMR spectra showed that UDOM from the oligotrophic Taylor Slough (TS) and Florida Bay (FB) ecosystems has low aromatic C (13% ± 3% for TS; 2% ± 2% for FB) and very high O-alkyl C (54% ± 4% for TS; 75% ± 4% for FB) concentrations. High O-alkyl C concentrations in FB suggest seagrass/phytoplankton communities as dominant sources of UDOM. The amount of neutral sugars was not appreciably different between the TS and FB sites (115 ± 12 mg C g C-1 UDOM) but their concentrations suggest a low level of diagenesis and high production rates of this material in this oligotrophic environment. Total yield of lignin phenols (vanillyl + syringyl phenols) in TS was low (0.20–0.39 mg 100 mg C-1 UDOM) compared with other riverine environments and even lower in FB (0.04–0.07 mg 100 mg C-1 UDOM) and could be a result of photodegradation and/or dilution by other utochthonous DOM. The high O-alkyl and low aromatic nature of this UDOM suggests significant biogenic inputs (as compared with soils) and limited bioavailability in this ecosystem.

Chemical characterization of dissolved organic nitrogen in an oligotrophic subtropical coastal ecosystem

Water samples were collected from rivers and estuarine environments within the Florida Coastal Everglades (FCE) ecosystem, USA, and ultrafiltered dissolved organic matter (UDOM; 1 kDa) was isolated for characterization of its source, bioavailability and diagenetic state. A combination of techniques, including 15N cross-polarization magic angle spinning nuclear magnetic resonance (15N CPMAS NMR) and X-ray photoelectron spectroscopy (XPS), were used to analyze the N components of UDOM. The concentrations and compositions of total hydrolysable amino acids (HAAs) were analyzed to estimate UDOM bioavailability and diagenetic state. Optical properties (UV–visible and fluorescence) and the stable isotope ratios of C and N were measured to assess the source and dynamics of UDOM. Spectroscopic analyses consistently showed that the major N species of UDOM are in amide form, but significant contributions of aromatic-N were also observed. XPS showed a very high pyridinic-N concentration in the FCE–UDOM (21.7 ± 2.7%) compared with those in other environments. The sources of this aromatic-N are unclear, but could include soot and charred materials from wild fires. Relatively high total HAA concentrations (4 ± 2% UDOC or 27 ± 4% UDON) are indicative of bioavailable components, and HAA compositions suggest FCE–UDOM has not undergone extensive diagenetic processing. These observations can be attributed to the low microbial activity and a continuous supply of fresh UDOM in this oligotrophic ecosystem. Marsh plants appear to be the dominant source of UDOM in freshwater regions of the FCE, whereas seagrasses and algae are the dominant sources of UDOM in Florida Bay. This study demonstrates the utility of a multi-technique and multi-proxy approach to advance our understanding of DON biogeochemistry.

Comparison of snail density, standing stock, and body size between Caribbean karst wetlands and other freshwater ecosystems

Synthesizing data from multiple studies generates hypotheses about factors that affect the distribution and abundance of species among ecosystems. Snails are dominant herbivores in many freshwater ecosystems, but there is no comprehensive review of snail density, standing stock, or body size among freshwater ecosystems. We compile data on snail density and standing stock, estimate body size with their quotient, and discuss the major pattern that emerges. We report data from 215 freshwater ecosystems taken from 88 studies that we placed into nine categories. Sixty-five studies reported density, seven reported standing stock, and 16 reported both. Despite the breadth of studies, spatial and temporal sampling scales were limited. Researchers used 25 different sampling devices ranging in area from 0.0015 to 2.5 m2. Most ecosystem categories had similar snail densities, standing stocks, and body sizes suggesting snails shared a similar function among ecosystems. Caribbean karst wetlands were a striking exception with much lower density and standing stock, but large body size. Disparity in body size results from the presence of ampullariids in Caribbean karst wetlands suggesting that biogeography affects the distribution of taxa, and in this case size, among aquatic ecosystems. We propose that resource quality explains the disparity in density and standing stock between Caribbean karst wetlands and other categories. Periphyton in Caribbean karst wetlands has high carbon-to-phosphorous ratios and defensive characteristics that inhibit grazers. Unlike many freshwater ecosystems where snails are key grazers, we hypothesize that a microbial loop captures much of the primary production in Caribbean karst wetlands.

Ecosystem structure, nutrient dynamics, and hydrologic relationships in tree islands of the southern Everglades, Florida, USA

Tree islands are an important structural component of many graminoid-dominated wetlands because they increase ecological complexity in the landscape. Tree island area has been drastically reduced with hydrologic modifications within the Everglades ecosystem, yet still little is known about the ecosystem ecology of Everglades tree islands. As part of an ongoing study to investigate the effects of hydrologic restoration on short hydroperiod marshes of the southern Everglades, we report an ecosystem characterization of seasonally flooded tree islands relative to locations described by variation in freshwater flow (i.e. locally enhanced freshwater flow by levee removal). We quantified: (1) forest structure, litterfall production, nutrient utilization, soil dynamics, and hydrologic properties of six tree islands and (2) soil and surface water physico-chemical properties of adjacent marshes. Tree islands efficiently utilized both phosphorus and nitrogen, but indices of nutrient-use efficiency indicated stronger P than N limitation. Tree islands were distinct in structure and biogeochemical properties from the surrounding marsh, maintaining higher organically bound P and N, but lower inorganic N. Annual variation resulting in increased hydroperiod and lower wet season water levels not only increased nitrogen use by tree species and decreased N:P values of the dominant plant species (Chrysobalanus icaco), but also increased soil pH and decreased soil temperature. When compared with other forested wetlands, these Everglades tree islands were among the most nutrient efficient, likely a function of nutrient immobilization in soils and the calcium carbonate bedrock. Tree islands of our study area are defined by: (1) unique biogeochemical properties when compared with adjacent short hydroperiod marshes and other forested wetlands and (2) an intricate relationship with marsh hydrology. As such, they may play an important and disproportionate role in nutrient and carbon cycling in Everglades wetlands. With the loss of tree islands that has occurred with the degradation of the Everglades system, these landscape processes may have been altered. With this baseline dataset, we have established a long-term ecosystem-scale experiment to follow the ecosystem trajectory of seasonally flooded tree islands in response to hydrologic restoration of the southern Everglades.

Top down control in a relatively pristine seagrass ecosystem

The loss of large-bodied herbivores and/or top predators has been associated with large-scale changes in terrestrial, freshwater, and marine ecosystems around the world. Understanding the consequences of these declines has been hampered by a lack of studies in relatively pristine systems. To fill this gap, I investigated the dynamics of the relatively pristine seagrass ecosystem of Shark Bay, Australia. I began by examining the seagrass species distributions, stoichiometry, and patterns of nutrient limitation across the whole of Shark Bay. Large areas were N-limited, P-limited, or limited by factors other than nutrients. Phosphorus-limitation was centered in areas of restricted water exchange with the ocean. Nutrient content of seagrasses varied seasonally, but the strength of seasonal responses were species-specific. Using a cafeteria-style experiment, I found that fast-growing seagrass species, which had higher nutrient content experienced higher rates of herbivory than slow-growing species that are dominant in the bay but have low nutrient content. Although removal rates correlated well with nutrient content at a broad scale, within fast-growing species removal rates were not closely tied to N or P content. Using a combination of stable isotope analysis and animal borne video, I found that green turtles (Chelonia mydas)—one of the most abundant large-bodied herbivores in Shark Bay—appear to assimilate little energy from seagrasses at the population level. There was, however, evidence of individual specialization in turtle diets with some individuals foraging largely on seagrasses and others feeding primarily on macroalgae and gelatinous macroplankton. Finally, I used exclusion cages, to examine whether predation-sensitive habitat shifts by megagrazers (green turtles, dugongs) transmitted a behavior-mediated trophic cascade (BMTC) between sharks and seagrasses. In general, data were consistent with predictions of a behavior-mediated trophic cascade. Megaherbivore impacts on seagrasses were large only in the microhabitat where megaherbivores congregate to reduce predation risk. My study highlights the importance of large herbivores in structuring seagrass communities and, more generally, suggests that roving top predators likely are important in structuring communities—and possibly ecosystems—through non-consumptive pathways.

Relating Freshwater Flow with Estuarine Water Quality in the Southern Everglades Mangrove Ecotone

Florida Bay is more saline than it was historically, and reduced freshwater flows may lead to more phosphorus inputs to the mangrove ecotone from the marine end-member. This is important given plans to restore freshwater flow into eastern Florida Bay. We investigated the relationships between salinity, nutrients, and hydrologic variables in the mangrove ecotone of Taylor Slough. We expected that total phosphorus (TP) would increase with salinity, reflecting a downstream marine source, while total nitrogen (TN) would increase with flow in the mangrove ecotone. Despite expectations of increased flows improving the ecological health of lower Taylor Slough and Florida Bay, total nitrogen (TN) and total phosphorus (TP) dynamics may shift in response to new conditions of flow and salinity as well as organic carbon, N, and P availability. Our results showed that TP concentrations are more discharge-driven while TN is more variable and potentially derived from different sources along the flow path from the freshwater Everglades marshes to Florida Bay. Increased flow of freshwater through Taylor Slough will likely decrease TP concentrations in this historically oligotrophic and P-limited ecosystem. However, more studies along the mangrove ecotone is needed to understand how increased flows will affect nitrogen dynamics relative to phosphorus.

Application of biomarkers and compound specific stable isotopes for the assessment of hydrology as a driver of organic matter dynamics in the Everglades ecosystem

The Everglades is a sub-tropical coastal wetland characterized among others by its hydrological features and deposits of peat. Formation and preservation of organic matter in soils and sediments in this wetland ecosystem is critical for its sustainability and hydrological processes are important divers in the origin, transport and fate of organic matter. With this in mind, organic matter dynamics in the greater Florida Everglades was studied though various organic geochemistry techniques, especially biomarkers, bulk and compound specific δ13C and δD isotope analysis. The main objectives were focused on how different hydrological regimes in this ecosystem control organic matter dynamics, such as the mobilization of particulate organic matter (POM) in freshwater marshes and estuaries, and how organic geochemistry techniques can be applied to reconstruct Everglades paleo-hydrology. For this purpose organic matter in typical vegetation, floc, surface soils, soil cores, and estuarine suspended particulates were characterized in samples selected along hydrological gradients in the Water Conservation Area 3, Shark River Slough and Taylor Slough. ^ This research focused on three general themes: (1) Assessment of the environmental dynamics and source-specific particulate organic carbon export in a mangrove-dominated estuary. (2) Assessment of the origin, transport and fate of organic matter in freshwater marsh. (3) Assessment of historical changes in hydrological conditions in the Everglades (paleo-hydrology) though biomarkes and compound specific isotope analyses. This study reports the first estimate of particulate organic carbon loss from mangrove ecosystems in the Everglades, provides evidence for particulate organic matter transport with regards to the formation of ridge and slough landscapes in the Everglades, and demonstrates the applicability of the combined biomarker and compound-specific stable isotope approach as a means to generate paleohydrological data in wetlands. The data suggests that: (1) Carbon loss from mangrove estuaries is roughly split 50/50 between dissolved and particulate carbon; (2) hydrological remobilization of particulate organic matter from slough to ridge environments may play an important role in the maintenance of the Everglades freshwater landscape; and (3) Historical changes in hydrology have resulted in significant vegetation shifts from historical slough type vegetation to present ridge type vegetation. ^

Environmental impacts of freshwater use and suspended solids in life cycle assessment

Perturbation of natural ecosystems, namely by increasing freshwater use and its degradative use, as well as topsoil erosion by water of land-use production systems, have been emerging as topics of high environmental concern. Freshwater use has become a focus of attention in the last few years for all stakeholders involved in the production of goods, mainly agro-industrial and forest-based products, which are freshwater-intensive consumers, requiring large inputs of green and blue water. This thesis presents a global review on the available Water Footprint Assessment and Life Cycle Assessment (LCA)-based methods for measuring and assessing the environmental relevance of freshwater resources use, based on a life cycle perspective. Using some of the available midpoint LCA-based methods, the freshwater use-related impacts of a Portuguese wine (white ‘vinho verde’) were assessed. However, the relevance of environmental green water has been neglected because of the absence of a comprehensive impact assessment method associated with green water flows. To overcome this constraint, this thesis helps to improve and enhance the LCA-based methods by providing a midpoint and spatially explicit Life Cycle Impact Assessment (LCIA) method for assessing impacts on terrestrial green water flow and addressing reductions in surface blue water production caused by reductions in surface runoff due to land-use production systems. The applicability of the proposed method is illustrated by a case study on Eucalyptus globulus conducted in Portugal, as the growth of short rotation forestry is largely dependent on local precipitation. Topsoil erosion by water has been characterised as one of the most upsetting problems for rivers. Because of this, this thesis also focuses on the ecosystem impacts caused by suspended solids (SS) from topsoil erosion that reach freshwater systems. A framework to conduct a spatially distributed SS delivery to freshwater streams and a fate and effect LCIA method to derive site-specific characterisation factors (CFs) for endpoint damage on aquatic ecosystem diversity, namely on algae, macrophyte, and macroinvertebrates organisms, were developed. The applicability of this framework, combined with the derived site-specific CFs, is shown by conducting a case study on E. globulus stands located in Portugal as an example of a land use based system. A spatially explicit LCA assessment was shown to be necessary, since the impacts associated with both green water flows and SS vary greatly as a function of spatial location.

A mesocosm analytical study on the impact of freshwater mussel (Lamellidens marginalis Lamarck) mediated bioturbation and biodeposition on some ecological factors of a freshwater lake

The biotic potential of the benthic filter feeding freshwater bivalve mollusc Lamellidens marginalis (Lamarck) influencing the nutrient dynamics of the bottom sediments of the lake by means of biodeposition and bioturbation activities were analysed using a lake mesocosm experiment. Five control as well as experimental mesocosms was maintained up to 60 days (d). The factors studied included the percentage of water content of the sediment, percentage of total nitrogen, percentage of organic matter along with the total phosphorus and humic acid content. While total phosphorus and humic acid content of the experimental mesocosoms showed gradual and significant increases from 30d of the experiment to reach the maximum levels after 60d, the percentage of organic matter registered significant increases right from 15d onwards and reached the maximum values after 60d. On the other hand, while the percentage of water content of the sediments of the experimental mesocosoms increased only up to 30d experiment, percentage of nitrogen was increased during the first half and at the fag end of the experiment. All the investigated ecological factors were found to be significantly influenced by the presence of L. marginalis in the experimental mesocosms. The study indicated that the mussel influence the nutrient dynamics of the inhabitant ecosystem through the processes of excretion, biodeposition of pseudofaeces and faeces, along with the bioturbation of the sediments brought about by their ploughing movements. KEYWORDS: freshwater mussel, Lamellidens marginalis, bioturbation, biodeposition, mesocosms.

Influência dos obstáculos de pequena dimensão na estruturação dos agrupamentos piscícolas: The impact of small physical obstacles on the structure of freshwater fish assemblages

O efeito das grandes barragens na comunidade piscícola vem sendo documentado por numerosos estudos, enquanto o número de trabalhos que incidem sobre o efeito dos obstáculos de pequena dimensão é bastante mais reduzido. A comunidade piscícola foi amostrada e as variáveis ambientais foram caracterizadas em 28 locais divididos por dois cursos de água da Península Ibérica, 14 dos quais localizados imediatamente a montante, jusante e entre cinco pequenos obstáculos na Ribeira de Muge e 14 na Ribeira de Erra, considerada a linha de água de referência. Através de análise estatística multivariada foi possível verificar que variáveis de habitat como a velocidade de corrente e a profundidade, e não as variáveis físico-químicas, foram as principais responsáveis pela discriminação dos vários grupos de locais nas duas ribeiras. A ribeira de referência exibiu um gradiente longitudinal de velocidade de corrente que, contudo, não era suficientemente forte para causar alterações significativas na composição e estrutura dos agrupamentos piscícolas. Através da sucessiva e drástica repetição deste gradiente junto a cada estrutura, a ribeira com obstáculos apresentou diferenças na fauna piscícola entre os três tipos de locais. Os troços lênticos a montante apresentavam uma densidade mais elevada de espécies limnofilicas, omnívoras e exóticas, como o góbio (Gobio lozanoi), que estão bem adaptadas a este tipo de habitat. Os locais de amostragem situados a jusante e entre os obstáculos caracterizavam-se pela dominância de taxa reófilos e invetivo-os (i.e. barbo, Luciobarbus bocagei). As métricas relacionadas com a riqueza específica não apresentaram diferenças entre os três tipos de locais, ao contrário da diversidade que foi mais elevada nos pontos situados entre os obstáculos, afastados da sua influência directa, onde a diversidade de habitats também é mais elevada. Contrariamente aos locais a montante, os troços a jusante e entre os obstáculos apresentaram similaridades, em muitas das características estudadas, com a ribeira de referência, sugerindo que este tipo de estruturas provoca uma alteração mais significativa na comunidade piscícola a montante. Este estudo sugere que os efeitos dos pequenos obstáculos no habitat e na ictiofauna são, em parte, semelhantes aos descritos para as grandes barragens, fornecendo considerações importantes para os esforços de conservação dos ecossistemas ribeirinhos. ABSTRACT; Many studies have assessed the effects of large dams on fishes but few have examined the effects of small obstacles. Fishes were sampled and environmental variables were characterized at 28 sites in two lberian streams, 14 located immediately downstream, upstream and between five small obstacles at River Muge and 14 at River Erra, considered as the reference stream. Multivariate analysis indicated that habitat variables like current velocity and depth, but not physicochemistry, were the main responsible for site groups' discrimination in both streams. The reference stream exhibited a longitudinal gradient of current velocity that, however, wasn't strong enough to cause significant changes in the fish assemblage's composition and structure. By successive and drastically repeating this gradient near each structure, the obstac1es stream presented differences in fish fauna between the three site types. Lentic upstream sites presented higher density of limnophilic, omnivorous and exotic species, like gudgeon Gobio lozanoi, who are well adapted to this type of habitat. Downstream and between obstacles sites were characterized by the dominance of rheophilic and invertivorous taxa, especially barbel Luciobarbus bocagei. Richness metrics did not differ among site types, but diversity was higher in sites located between the obstacles away from its direct influence, where the habitat diversity was higher. Contrarily to upstream sites, downstream and between obstacles sites were similar in many of the studied features to the reference stream, implying that this type of structures cause a higher modification in the upstream fish community. This study suggests that the effects of small obstacles on habitat and fishes are similar, in some extent, to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.

Mineral and organic pollution in river Sabor (Northeastern Portugal): ecotoxicological effects on freshwater fauna

Aquatic ecosystems are final collectors of all kinds of pollution as an outcome of anthropogenic inputs, such us untreated industrial and municipal sewage and agricultural pollutants. There are several aquatic ecosystems that are threatened by mineral and organic pollution. In Northeastern Portugal, near Bragança, different watercourses are suffering negative impacts of human activities. It has been developed several studies in the monitoring of environmental impacts in these river basins, namely in Rio Fervença, affected by organic pollution, and in Portelo stream, affected, since 2009, by the collapse and continuous input of mining deposits. In this sense, the present study aimed to continue the monitoring study of ecological status of freshwater ecosystems of Northeastern Portugal, namely the following objectives: a) mineral pollution effects of mining deposits sudden incorporated into Portelo stream; b) organic pollution due to domestic and industrial inputs in River Fervença. Also, since fish are useful experimental models to evaluate toxicological mechanisms of contaminants, c) acute toxicity tests with Cu were conducted in laboratory conditions. During 2015/2016, it was made abiotic and biotic characterization of 16 sampling sites distributed by both Portelo and Fervença rivers, tributaries of main River Sabor (Douro Basin). Several physicochemical parameters were determined and Riparian Quality (QBR Index) and Channel Quality (GQC) Indexes were determined for habitat evaluation. Fish and invertebrate communities were sampled, according to protocols of Water Framework Directive (WFD). Several metrics were determined, with particular emphasis on the Biotic Index IBMWP and the Northern Portuguese Invertebrate Index (IPtIN). Acute toxicity tests were conducted with an Iberian fish species, common barbel (Luciobarbus bocagei) and some plasmatic electrolytes levels were evaluated, to assess their contribution to mitigate osmoregulatory adverse effects of Cu. Also, same electrolytes were measured after changing to clean water, in attempt to assess fish capacity to reverse this situation. Results obtained for both rivers showed a significant level of disturbance that affected decisively water, habitat and biological quality of aquatic ecosystems. Mineral and Organic Pollution in River Sabor (NE Portugal): Ecotoxicological Effects on Freshwater Fauna Due to this change of environmental conditions in Portelo stream (extreme pH values, high conductivity and presence of heavy metals), several biological metrics (e.g. taxonomic richness, abundance, diversity, evenness) confirmed, comparatively with reference sites, a substantial decrease on ecological integrity status. The same pattern was found for Fervença River; however other water parameters, namely the content of most limiting nutrients (e.g. N and P) seemed to have more influence in the composition and structure of macroinvertebrate and fish communities. In fact, despite the operation of the Sewage Treatment Plant of Bragança, Fervença River presented significant levels of disturbance that affected decisively the quality and ecological integrity of the aquatic ecosystem. The synergic effect of domestic and industrial pollution, intensive agriculture, regulation and degradation of aquatic and riparian habitats contributed to the decrease of ecological condition, namely in the downstream zones (after Bragança). The results for acute toxicity, showed that fish can change Na+ and K+ levels face to Cu exposition and, depending of Cu concentration tested, can also return to normal levels, providing some insights to that are believed to occurred in fish population, near the Portelo mines. The low ecological integrity status detected in the lotic ecosystems in NE Portugal as a result of mineral and organic pollution deserves the development of several measures for rehabilitation and improving of water quality. On the other hand, environmental education actions are needed to contribute to improvement of ecological integrity of the river and its conservation.

Impacts of high-nitrate freshwater inputs on macrotidal ecosystems. I. Seasonal evolution of nutrient limitation for the diatom-dominated phytoplankton of the Bay of Brest (France)

The chemical factors (inorganic nitrogen, phosphate, silicic acid) that potentially or actually control primary production were determined for the Bay of Brest, France, a macrotidal ecosystem submitted to high-nitrate-loaded freshwater inputs (winter nitrate freshwater concentrations >700 mu M, Si:N molar ratio as low as 0.2, i.e. among the lowest ever published). Intensive data collection and observations were carried out from February 1993 to March 1994 to determine the variations of physical [salinity, temperature, photosynthetically active radiation (PAR), freshwater discharges] and chemical (oxygen and nutrients) parameters and their impacts on the phytoplankton cycle (fluorescence, pigments, primary production). With insufficient PAR the winter stocks of nutrients were almost nonutilized and the nitrate excess was exported to the adjacent ocean, due to rapid tidal exchange. By early April, a diatom-dominated spring bloom developed (chlorophyll a maximum = 7.7 mu g l(-1); primary production maximum = 2.34 g C m(-2) d(-1)) under high initial nutrient concentrations. Silicic acid was rapidly exhausted over the whole water column; it is inferred to be the primary limiting factor responsible for the collapse of the spring bloom by mid-May. Successive phytoplankton developments characterized the period of secondary blooms during summer and fall (successive surface chlorophyll a maxima = 3.5, 1.6, 1.8 and 1.0 mu g l(-1); primary production = 1.24, 1.18 and 0.35 g C m(-2) d(-1)). Those secondary blooms developed under lower nutrient concentrations, mostly originating from nutrient recycling. Until August, Si and P most likely limited primary production, whereas the last stage of the productive period in September seemed to be N limited instead, this being a period of total nitrate depletion in almost the whole water column. Si limitation of spring blooms has become a common feature in coastal ecosystems that receive freshwater inputs with Si:N molar ratios <1. The peculiarity of Si Limitation in the Bay of Brest is its extension through the summer period.