Human-induced Eutrophication Research Articles

Helminth communities of fish as ecological indicators of lake health

This paper deals largely with the dynamics and changes in the helminth parasite communities of fish along the trophic gradient of lakes. The use of parasitological community data as a bioindicator of environmental health underlines the need to study parasite communities at comparable localities with known pollution levels. The comparison of the conditions in different habitats might be helpful to differentiate between normal fluctuations in ambient conditions and pollution-mediated effects. Therefore, the present study was designed to examine the community structure of parasites in snow trout (Schizothorax niger Heckel) inhabiting 3 lakes of contrasting trophic status in Kashmir. The idea of selecting the lakes, namely Anchar (strongly hypereutrophic), Dal (eutrophic) and Manasbal (mesotrophic) for this study was intentional as they depict different trophic gradients and exhibit the desirable pattern which was a prerequisite for this study. The findings presented in this article suggest an apparent lake-wise gradient in community structure, as the increase in trematode and cestode infections in Anchar was markedly greater, to levels clearly distinguishable from those in the other two water bodies. We conclude that human-induced eutrophication of lakes modifies the parasite community at component level and community-level studies on parasites may provide information on health status of lakes.

Algal blooms impact the quality of nest construction in three-spined sticklebacks

Purpose-built nests for rearing offspring have important fitness consequences. Nests not only provide a protective environment for developing young but also in some species can serve as important signalling devices that reveal crucial information about the quality of the builder. Nesting behaviour and nest structure are often adjusted to suit local environmental conditions. An important question is what happens when conditions are altered as a result of anthropogenic activities. Human-induced eutrophication is an insidious, global problem. Here, we investigated experimentally the impact of algal blooms on nest construction in a fish: the three-spined stickleback, Gasterosteus aculeatus. We found that males took longer to complete their nests under algal conditions. Completed nests were also smaller and possessed wider nest entrances. Together, our results suggest that human-induced algal blooms can have profound effects on nesting behaviour and nest construction, with implications for both offspring survival and the utility of nests as extended phenotypic signals.

Habitat change influences mate search behaviour in three-spined sticklebacks

Mate choice is one of the main mechanisms of sexual selection, with profound implications for individual fitness. Changes in environmental conditions can cause individuals to alter their mate search behaviour, with consequences for mate choice. Human-induced eutrophication of water bodies is a global problem that alters habitat structure and visibility in aquatic ecosystems. We investigated whether changes in habitat complexity and male cue modality, visual or olfactory, influence mate search behaviour of female three-spined sticklebacks, Gasterosteus aculeatus. We allowed gravid females to search for mates in experimental pools that contained two nesting males and one social female, under low and high structural complexity (created from green Plexiglas sheets), with access to either visual or olfactory cues of the individuals. We found increased habitat complexity reduced the number of visits to nesting males, while a switch from visual to olfactory cues reduced the time spent searching for males, the number of visits to nesting males, the time spent evaluating males, and the relative time spent associating with males rather than females. Thus, females decreased mate searching and mate evaluation in the absence of visual stimulation. This reduced the rate of mate encounters and probably also the opportunity for choice. Our results show that changes in habitat structure and visibility can alter female mate searching, with potential consequences for the opportunity for sexual selection.

Density-Dependent Habitat Selection in a Growing Threespine Stickleback Population

Human-induced eutrophication has increased offspring production in a population of threespine sticklebackGasterosteus aculeatusin the Baltic Sea. Here, we experimentally investigated the effects of an increased density of juveniles on behaviours that influence survival and dispersal, and, hence, population growth—habitat choice, risk taking, and foraging rate. Juveniles were allowed to choose between two habitats that differed in structural complexity, in the absence and presence of predators and conspecific juveniles. In the absence of predators or conspecifics, juveniles preferred the more complex habitat. The preference was further enhanced in the presence of a natural predator, a perchPerca fluviatilis(behind a transparent Plexiglas wall). However, an increased density of conspecifics relaxed the predator-enhanced preference for the complex habitat and increased the use of the open, more predator-exposed habitat. Foraging rate was reduced under increased perceived predation risk. These results suggest that density-dependent behaviours can cause individuals to choose suboptimal habitats where predation risk is high and foraging rate low. This could contribute to the regulation of population growth in eutrophicated areas where offspring production is high.

Habitat preferences and conservation of Vertigo geyeri (Gastropoda: Pulmonata) in Slovakia and Poland

The tiny land snail Vertigo geyeri Lindholm, 1925 is a rare relict from the Late Glacial, inhabiting treeless spring fens. The main aims of this study were (1) to summarize present knowledge on distribution of V. geyeri in Slovakia and in Poland; (2) to analyse its ecology and habitat preferences; and (3) to suggest suitable conservation and management measures for this EUHSD Annex II species. In the course of field research on 122 fens in Slovakia and Poland, carried out between 2001 and 2011, we documented 33 Slovak and 24 Polish sites where this species occurred. Based on analysis of these populations, we identified a strong preference for permanently wet, but not extremely waterlogged, open fen sites with low-productivity nutrient-limited vegetation. The species displayed a unimodal response to calcium concentration in the groundwater, avoiding both calcium-poor Sphagnum-dominated fens and extremely mineral-rich and salt travertine fens. All sites in which V. geyeri occurs should be protected to prevent any hydrological changes resulting in successional shifts towards more productive and shrubby vegetation. Human-induced eutrophication should be also controlled to ensure the long-term maintenance of viable populations of the species. The locations of all Slovak and Polish fen sites in which V. geyeri has been recorded are provided to enable or maintain protection of the species at these sites.

Algal blooms decrease care but increase egg survival in a fish with paternal care

Human-induced eutrophication, resulting in algal blooms and increased water turbidity, is an alarming problem in aquatic systems. Here, we experimentally tested the impact of algal turbidity on parental care, egg fanning, and time in the nest, in the sand goby, Pomatoschistus minutus, a fish with uniparental male care. We allowed males to care for their eggs in either clear water or water made turbid by planktonic algae. In the early brood cycle, males fanned their eggs less in turbid than in clear water, but this difference disappeared later. Despite decreased care, egg survival was higher in turbid conditions, indicating that early fanning may partly be redundant for egg survival and perhaps used more as courtship. Males also spent more time out of their nest in turbid water, perhaps as a means to encounter additional females under conditions of low visibility.

Vertical variability of pelagic zooplankton fauna in deep Latvian lakes, with some notes on changes in ecological conditions

Vertical structure of zooplankton communities from five deep Latvian lakes during the late summer and early autumn season was analysed. Changes in species composition, abundance, and dominant species assemblages were assessed in relation to temperature, oxygen, pH, chlorophyll a, oxidation reduction potential, and conductivity. Where possible, comparison with historical data was made. No significant changes of ecological conditions and annual dynamics of zooplankton diversity and abundance during the last 50 years were observed. However, a decrease of oxygen concentration occurred in deep lakes, caused probably by the pressure of human induced eutrophication. Also, slight differences were observed in the species composition, which most likely mark changes in the trophic status. A total of 24 to 38 Rotifera and Cladocera species were found during investigations from all lakes. The dominant species were Conochilus hippocrepis, Keratella cochlearis, Polyarthra vulgaris, Filinia longiseta, Kellicottia longispina, Daphnia (Daphnia) cucullata, Diaphanosoma brachyurum, Bosmina (Eubosmina) crassicornis, and B. (Eubosmina) longispina. Zooplankton communities can be defined as distinct groups both at species and higher levels on the basis of seasonal stratification in deep lakes. Temperature, oxidation reduction potential, and chlorophyll a concentration were found to be statistically the most influential environmental factors in the vertical distribution of zooplankton. Also sampling date and depth showed strong trends concerning zooplankton abundance and species composition. Vertical segregation between samples occurred within water layers of 0-10 m, 10-20 m, and below 20 m depth. The samples collected at the beginning of the sampling season assembled into a separate group.

Long-term dynamics of zooplankton in the Matiţa and Merhei shallow lakes (the Danube Delta, Romania). 1. Diversity and abundance

Long-term dynamics of zooplankton in the Matiţa and Merhei shallow lakes (the Danube Delta, Romania). 1. Diversity and abundance The present paper presents significant changes occurred in the multi-annual dynamics of zooplankton diversity and abundance (1980-2007), under the pressure of human-induced eutrophication in two shallow lakes specific for the Danube Delta. Zooplankton community from lakes Matiţa and Merhei was characterized by high species richness but low abundance values until 1981, in ecological conditions unaffected by eutrophication. For the next ten years, due to obvious increases of human pressures, zooplankton species richness decreased with 52% and 63%, respectively, while abundance values increased with 39% and 16%, respectively. After 1991, the social and economic changes in the Danube countries from the Central Europe led to nutrient input decreases. As a result, lake ecosystems from the Danube Delta showed lower trophicity values and their ecological parameters tended to recover. Analyses on the dynamics of the Shannon-Wiener's informational entropy index, Pielou's evenness and Simpson's index of dominance offered additional information and reduced the heterogeneity of the data regarding the species richness and the numerical abundance dynamics. Moreover, correlation analyses suggested the influences of human-induced changes of nutrient inputs on the multi-annual zooplankton dynamics.

Changes in physicochemical and biological factors during regime shifts in a restoration demonstration of macrophytes in a small hypereutrophic Chinese lake

Shallow, eutrophic lakes are usually characterized by a turbid state devoid of submerged vegetation subject to human-induced eutrophication. In most cases, it is rather hard to restore a vegetated clear state due to reduced resilience caused by a blend of complicated factors. In this study, we successfully reestablished a plant community in a small hypereutrophic lake over a certain period. In winter and spring with transparency of >55 cm and temperature of <20 °C, a submerged stands bed formed gradually under strong human interventions. The reestablished plant bed displayed obvious seasonal succession and prolonged the clear-water stage until July 2005, when it collapsed. The regime shift to a turbid state was mainly attributed to the decreasing biomass of stands bed and mechanical damage brought about by the elimination of Spirodela polyrhiza, increasing water temperature, P concentration as well as periphyton biomass, etc. The reestablishment also changed the aquatic ecosystem greatly. A ‘clear-water’ stage was characterized by higher NO 3 −–N, NH 4 +–N, electrical conductivity, transparency and TN/TP level and more cladocerans (mainly Daphnia pulex), while the turbid state was characterized by higher temperature, chlorophyll a and TP level and more abundant rotifers. It is thus viable to restore submerged macrophytes in such lakes in winter and spring, when transparency is relatively high while temperature and water level are low. Nevertheless, to obtain a long-term, vegetated clear state, control of internal nutrient loading by means of obstruction, purification, dredging or solidification, is extremely necessary since nutrients play an important role in regime shifts as evidenced by the present case, too.

Assessment of the risk of cyanobacterial bloom occurrence in urban ponds: probabilistic approach

Blooms of toxic cyanobacteria became a common feature of temperate lakes and ponds owing to human induced eutrophication. Occurrence of cyanobacterial blooms in an urban context may pose serious health concerns. This necessitates the development of tools for assessment of the risk of noxious bloom occurrence. A five year study of 42 Brussels ponds showed that cyanobacteria have threshold rather than linear relationships with environmental variables controlling them. Hence, linear relationships have limited predictive capacity for cyanobacterial blooms. A probabilistic approach to prediction of bloom occurrence using environmental thresholds as conditions in conditional probability calculation proved to be more useful. It permitted the risk of cyanobacterial bloom occurrence to be quantified and thus the conditions and thence the ponds the most prone to cyanobacterial bloom development to be singled out. This approach can be applied for the assessment of the risk of cyanobacterial bloom occurrence in urban ponds and thus can facilitate monitoring planning, remediation efforts and setting restoration priorities.

Patterns of morphological changes and hybridization between sympatric whitefish morphs (Coregonus spp.) in a Swiss lake: a role for eutrophication?

Whitefish, genus Coregonus, show exceptional levels of phenotypic diversity with sympatric morphs occurring in numerous postglacial lakes in the northern hemisphere. Here, we studied the effects of human-induced eutrophication on sympatric whitefish morphs in the Swiss lake, Lake Thun. In particular, we addressed the questions whether eutrophication (i) induced hybridization between two ecologically divergent summer-spawning morphs through a loss of environmental heterogeneity, and (ii) induced rapid adaptive morphological changes through changes in the food web structure. Genetic analysis based on 11 microsatellite loci of 282 spawners revealed that the pelagic and the benthic morph represent highly distinct gene pools occurring at different relative proportions on all seven known spawning sites. Gill raker counts, a highly heritable trait, showed nearly discrete distributions for the two morphs. Multilocus genotypes characteristic of the pelagic morph had more gill rakers than genotypes characteristic of benthic morph. Using Bayesian methods, we found indications of recent but limited introgressive hybridization. Comparisons with historical gill raker data yielded median evolutionary rates of 0.24 haldanes and median selection intensities of 0.27 for this trait in both morphs for 1948-2004 suggesting rapid evolution through directional selection at this trait. However, phenotypic plasticity as an alternative explanation for this phenotypic change cannot be discarded. We hypothesize that both the temporal shifts in mean gill raker counts and the recent hybridization reflect responses to changes in the trophic state of the lake induced by pollution in the 1960s, which created novel selection pressures with respect to feeding niches and spawning site preferences.

Recent environmental changes and filamentous algal mats in shallow bays on the Swedish west coast — A result of climate change?

Over the last thirty years, many shallow estuarine bays, located in Scandinavian sheltered coastal environments, have been subject to the increased dominance of opportunistic species of filamentous green algae, oxygen deficiency in bottom waters and the alteration of flora and fauna. Human-induced eutrophication has been held responsible for these recent changes, but from this study the importance of climatic factors emerges. This research is based on the analysis of sediment cores from 8 shallow areas ( d < 50 cm) along the Bohuslän archipelago, Swedish west coast, and focuses on their recent (< 100 years) sedimentary evolution. Evidence of hydrodynamic change was observed in the sediments, where modern fining-upward sequences contrast with the expected coarsening upward model due to ongoing land uplift. Heavy metal concentrations from modern pollution and 14C dating of mollusk shells and eelgrass roots provided the age control, and allowed to place these changes within the last three decades. Data were compared with historical meteorological records (seasonal warming, modification of dominant winds and upwelling and reduction of sea-ice), and a clear connection emerged between the environmental changes and variations in the North Atlantic Ocean weather pattern. The increase of winter temperature and reduction of reworking winter sea-ice in these sheltered bays increased the storing of nutrients in the sediments and the turnover of organic matter, favoring the early growth stage of opportunistic algae in the most sheltered areas of the archipelago. This, together with human-induced modifications (overfishing and eutrophication), increased the possibility of opportunistic explosions, which in turn determined a reduced water exchange, the increased deposition of fine sediments and organic matter and evolving hypoxic conditions.

Population responses to anthropogenic disturbance: lessons from three‐spined sticklebacksGasterosteus aculeatusin eutrophic habitats

Human-induced environmental changes differ from most natural changes in which they happen at a faster rate and require quicker responses from populations. The first response of populations is usually phenotypically plastic alterations of morphology, physiology and behaviour. This plasticity can be favourable and move the population closer to an adaptive peak in the altered environment and, hence, maintain a viable population, or be maladaptive and move the population further from the peak and increase the risk of extinction. The radiation of the three-spined stickleback Gasterosteus aculeatus from the ocean to different freshwater habitats has provided much information on adaptation to new environmental conditions. Currently, human-induced eutrophication is changing the breeding areas of these fish, which creates a model system for investigation of responses to rapid environmental disturbance. Results show that a primary reaction is plastic alterations of behaviour, with some adjustments being adaptive while others are not. At the same time, the strength of sexual selection on several traits is relaxed, which could increase the relative importance of survival selection. Whether this will restore population viability depends on the amount of standing genetic variation in the right direction. Human disturbances can be dramatic and resolution of the limit of flexibility and the possibility of genetic adaptation should be important targets of future research.

Long-Term (1996–2006) Variation of Nitrogen and Phosphorus and Their Spatial Distributions in Tianjin Coastal Seawater

The spatio-temporal varying characteristics of dissolved inorganic nitrogen, reactive phosphate (RP), chemical oxygen demand (COD), and dissolving oxygen (DO) in Tianjin coastal seawater were investigated based on observation from May 1996 to October 2006. The concentrations of dissolved inorganic nitrogen (DIN), RP and COD ascended gradually and their varying ranges were 0.103-2.432, 0.009-0.12, and 0.8-2.9 mg L(-1), respectively. While DO in seawater decreased from 8.9 to 6.1 mg L(-1) gradually. Those indicated that human-induced eutrophication occurred and the seawater quality deteriorated. The spatial distributions of DIN, RP and COD were largely uniform, where isopleths generally descended from estuarine zones and bays to the central areas and from northern area to southern area, indicating that continental input is the dominant source of those pollutants. Especially, peak zones of those pollutants usually appeared near estuaries, Tianjin harbors, and dumping site of dredged sediment, which indicates that the urban and industrial sewage, shipping waste, dredged soil were the main sources for those contaminants in seawater.

Eutrophication of U.S. Freshwaters: Analysis of Potential Economic Damages

Human-induced eutrophication degrades freshwater systems worldwide by reducing water quality and altering ecosystem structure and function. We compared current total nitrogen (TN) and phosphorus (TP) concentrations for the U.S. Environmental Protection Agency nutrient ecoregions with estimated reference conditions. In all nutrient ecoregions, current median TN and TP values for rivers and lakes exceeded reference median values. In 12 of 14 ecoregions, over 90% of rivers currently exceed reference median values. We calculated potential annual value losses in recreational water usage, waterfront real estate, spending on recovery of threatened and endangered species, and drinking water. The combined costs were approximately $2.2 billion annually as a result of eutrophication in U.S. freshwaters. The greatest economic losses were attributed to lakefront property values ($0.3-2.8 billion per year, although this number was poorly constrained) and recreational use ($0.37-1.16 billion per year). Our evaluation likely underestimates economic losses incurred from freshwater eutrophication. We document potential costs to identify where restoring natural nutrient regimes can have the greatest economic benefits. Our research exposes gaps in current records (e.g., accounting for frequency of algal blooms and fish kills) and suggests further research is necessary to refine cost estimates.

Production of renewable bioproducts and reduction of phosphate pollution through the lime pretreatment and acidogenic digestion of dairy manure

Acidogenic digestion with lime pretreatment was proposed as a means of reducing soluble reactive phosphorous concentrations in dairy cow manure while producing calcium carboxylate salts as a chemical platform for production of fuels and chemicals via the MixAlco Process. When concentrated in small geographic areas, large dairy operations can have environmentally harmful impacts on their watersheds, due to excess nutrients causing eutrophication of local water bodies. In Central Texas, as in many other areas, phosphorous contamination from confined animal feeding operations is a leading cause of human induced eutrophication. It was found that lime pretreatment followed by acidogenic or methanogenic anaerobic digestion led to substantial reductions in soluble reactive phosphate (SRP) levels while also producing potentially valuable products. Dairy manure filtrate was analyzed for SRP before and after the process steps of lime pretreatment and anaerobic digestion. An average reduction of SRP by 89% was observed through the two step process for lime pretreatment coupled with acidogenic digestion. Acidogenic digestion was demonstrated to produce mixed organic acids at mesophillic temperatures and primarily acetic acid at thermophillic temperatures. Using the MixAlco Process, the carboxylate salts of these organic acids could potentially be converted into marketable fuels and chemicals. © 2008 American Institute of Chemical Engineers Environ Prog, 2009

Estudo dos fatores limitantes à produção primária por macrófitas aquáticas no Brasil

Normal 0 21 false false false MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} The littoranean ecosystems of Brazil generally present vast areas colonized by aquatic macrophyte plants. In this work we present and discuss a number of studies about the main limitant factors to primary production of aquatic macrophyte plants in Brazil, and the underlying effects of human activities. The limitant factors here discussed would include temperature, photosynthetic active radiation, current speed, and available amounts of nitrogen, phosphorus and inorganic carbon. Studies in the field as well as in the laboratory are discussed. Laboratory studies enable assessing the effects of isolated variations in the rearing conditions over the growth of aquatic macrophytes. Such studies are scant in Brazil. Anthropogenic alterations on aquatic ecosystems affect the growth and primary production of aquatic macrophytes. Humaninduced eutrophication promotes the growth of free-floating, emerged, and submerged algae. The construction of dams also interferes on macrophytes growth, because it causes changes in water flow and levels, which are important factors driving the production of these plants. Knowledge about ecology of aquatic macrophytes and limitant factors to their growth in Brazil is poor, as few environments and species were studied, making it difficult to compare results. We would suggest improving the technical formation of researchers, increasing the area of field investigations, increasing the number of laboratory tests with controlled conditions and promoting more scientific gatherings about aquatic macrophytes to amend that knowledge defficiency.

Quantifying human-induced eutrophication in Swiss mountain lakes since AD 1800 using diatoms

Sedimentary diatom assemblages from three lakes in the southeastern Swiss Alps were analysed at high temporal resolution since AD 1800. Altered land-use patterns, increasing population and exploitation through tourism are clearly reflected in annually laminated sediments of Lej da San Murezzan (Lake St Moritz) and Lej da Silvaplauna (Lake Silvaplana). Diatom assemblages originally dominated by Cyclotella taxa are replaced by taxa indicating higher total phosphorus (TP) concentrations, such as Asterionella formosa, Fragilaria crotonensis and Stephanodiscus parvus. In Lej da la Tscheppa, located well above the treeline in a catchment that was hardly exposed to human impact, Cyclotella comensis prevails throughout the entire sediment sequence. Quantitative estimates of past TP concentrations were inferred using a newly developed regional diatom-TP inference model based on 119 modern samples. In Lej da la Tscheppa diatoms imply stable, low TP concentrations (~10 µg/l), which can be considered as natural background concentration. Elevated TP levels are inferred for Lej da San Murezzan (max. 60 µg/l) since AD 1910 and for Lej da Silvaplauna (max. 40 µg/l) since AD 1950, corroborated by changes in sedimentary biogenic silica concentration and organic carbon content. Since ~AD 1970 improved waste water management led to a considerable reduction in TP loading in Lej da Silvaplauna and Lej da San Murezzan.

An increase in pH boosts olfactory communication in sticklebacks

Human-induced eutrophication is a serious environmental problem that constrains visual communication and influences the mate choice process in fishes. Eutrophication also changes the chemical environment and the pH of the water, which could influence the use of olfactory cues in mate choice. Here, we show that an increase in pH enhances the use of male olfactory cues in mate choice in three-spined sticklebacks, Gasterosteus aculeatus. In a laboratory choice experiment, gravid females were more attracted to male olfactory cues when pH was raised. This could compensate for impaired visual communication in eutrophied waters and facilitate adaptive mate choice.

Inferred Phosphorus Cycling in Shallow and Deep Basins of Eutrophied Lake Hormajärvi, Southern Finland

Lake Hormajärvi is a typical small lake in southern Finland suffering from human-induced eutrophication. The lake has a complex basin morphology; the western basin is deeper and does not suffer the consequences of eutrophication of the shallower eastern basin, where poor water quality prevents swimming, fishing and other recreational use of the lake. Two short sediment cores from both basins were taken and studied to understand the eutrophication history of the lake, phosphorus (P) cycling within the respective basins and to evaluate needs for lake management and restoration. Sediments were analyzed for diatoms, P fractions, and physical properties. Spherical carbonaceous particles (SCP) were used for dating. Results indicate that diatom inferred autumnal lake surface water total P (DITP) does not follow the trend in accumulated P in the western basin, whereas there is a clear correlation in the eastern basin. The western basin acts as a permanent sink for P, but in the unstratified eastern basin, P released from sediment circulated throughout the water column. Results demonstrate that lake management or restoration decisions should not be made based on water quality and algal bloom observations alone. Detailed paleolimnological studies provide essential information to understand processes in complicated basins like Lake Hormajärvi.