Intense Eutrophication Research Articles

Trends in succession of parasitofauna of fish of eutrophied water bodies

The established trends in the change of parasitofauna of fish under conditions of an intense eutrophication of a water body have a common pattern. The use of revealed indicator species of parasites enables the monitoring and control of the parasitological situation under conditions of an increase in the delivery of biogenic elements, among them, in organizing fish farms.

Fish community changes in the cooler of the Ignalina Nuclear Power Plant

Th e study focuses on the changes of fi sh community and population parameters (abundance, biomass, growth rate) in Lake Drūksiai as the cooler of the Ignalina Nuclear Power Plant. Results of investigations before launching the INPP and in diff erent stages of its exploitation as well as the impact on ecological processes of the ecosystem of the cooler, including biological productivity, are generalised. Ichthyological investigations in diff erent aquatic areas of the lake in 2005–2007 revealed rather signifi cant changes in fi sh species diversity and community structure as a result of changes in its thermal regime and intensive anthropogenic eutrophication. Th e tendencies of changes in fi sh diversity and community structure are revealed. Fish growth rates in diff erent aquatic areas of the lake are estimated. Roach and perch populations served as an example to demonstrate higher growth rates in the “warm water” zone of the lake as compared with the “cold water” zone. As regards fi shery, Lake Drūksiai continues to be a high-productivity water body with intensive angling, but insuffi cient commercial fi shing. In 2007, fi sh stocks in the lake averaged 671.78 t and the commercial fi sh catching limit was ca. 67.180 t, or 18.5 kg/ha. Our investigations show that fi sh stocks in Lake Drūksiai have decreased by 9% compared with the results of earlier investigations.

Dynamics of invertebrate communities on the stony littoral of the Neva Estuary (Baltic Sea) under macroalgal blooms and bioinvasions

1 - The Littoral zone of the Neva Estuary is strongly influenced by (mainly Cladophora glomerata). The present paper aims to study species composition, abundance and seasonal dynamics of littoral invertebrate communities in the Neva Estuary in order to assess their current status and the influence of macroalgal blooms on invertebrates. 2 - Littoral communities at three sites in the Neva Estuary were monitored during May to October of 2002, 2004 and 2005. Quantitative sampling of macroinvertebrates at a depth of 0.5 m was carried out with a 0.03 m2 cylindrical metal frame. Temperature, conductivity, dissolved oxygen and total phosphorus in water were measured at studied sites using a WTW Oxi330 oxygen meter, a DistWP4 conductivity meter and standard analytic techniques. 3 - A list of macroinvertebrate species includes 104 taxa in the freshwater part of the Neva Estuary and considerably fewer in its oligohaline part due to the disappearance of some species of typical freshwater groups (oligochaetes and dipterans). Amphipods Gmelinoides fasciatus and Pontogammarus robustoides, recent invaders to the Neva Estuary, were abundant species at all studied habitats of the estuary, accounting for 73% of the total biomass of zoobenthos. 4 - We obtained significant positive correlations between the density of invertebrate groups (oligochaetes, chironomids, ephemeropterans, trichopterans, amphipods) and oxygen content in water. Temporary hypoxia (0.62–2.8 mgl-1) and a 4-10-fold decrease in the density of amphipods, oligochaetes and aquatic insects were recorded in littoral habitats during decomposition of drifting filamentous algae (July-August). We conclude that intensive macroalgal blooms in the littoral zone due to the intense eutrophication of the Neva Estuary can negatively affect the density of intolerant species and groups and the structure of the invertebrate community through deterioration of oxygen conditions and increase of nutrients during intensive decomposition of drifting algae.

Seasonal succession of cyanoprokaryotes in a hypereutrophic oligo-mesohaline lagoon from the South of France

The Bolmon lagoon (South of France) is an oligo-mesohaline coastal lagoon that has undergone intense eutrophication in the past decades, resulting from a strong concentration of human activities in its drainage basin. Consequently, it exhibits some characteristics typical of an advanced trophic state; namely, the disappearance of submerged vegetation, the permanently intense phytoplankton growth and the recurrence of cyanoprokaryote blooms. As cyanoprokaryote dominance in south-temperate saline lagoons is little reported, we carried out this study in order to understand the seasonal variations in the phytoplankton composition and biomass, and to analyse the influence of environmental parameters such as salinity, nutrients and climate on the seasonal succession of species. In this lagoon, the phytoplankton was permanently dominated by cyanoprokaryotes, probably because of high availability of nutrients, low light penetration in the water column and frequent turbulent mixing induced by wind. The two most abundant species Planktothrix agardhii (in winter–spring) and Pseudanabaena limnetica (in summer) have low light requirements and are well adapted to a high mixing frequency, which defines the S1 functional group in Reynolds' typology for phytoplankton. Although widely studied in north-temperate lakes, blooms of these typically freshwater species are almost unreported in the Mediterranean area, especially in brackish ecosystems that are not their normal habitat. In the Bolmon lagoon, all their requirements for nutrients, light and mixing are satisfied and they seem to cope with a moderate presence of salt but P. agardhii was less competitive than P. limnetica at highest salinities, the latter being probably more halophytic. Contrary to the observations in lakes located at higher latitudes, the Mediterranean climate seems to induce a typical seasonal pattern of succession characterised by the dominance of P. agardhii (winter) – Chroococcales (spring) – Pseudanabaenaceae (summer) – P. agardhii (autumn, winter). The warm temperatures seemed to have a major influence on the phytoplankton succession, being responsible for the survival of Planktothrix during winter and its rapid and intense development in early spring. Intense mixing and high irradiance in summer promoted the development of Pseudanabaenaceae, as reported in another south-temperate lagoon, the Albufera of Valencia (Spain). The ecological success of Oscillatoriales observed in the Bolmon lagoon is a perfect example of a shift to the “turbid stable state” as proposed for freshwater shallow lakes only. Our work demonstrated that hypereutrophic Mediterranean lagoons can function very similarly to shallow lakes at higher latitudes; but the warmer climate and higher irradiances are probably responsible for differences in the seasonal pattern of species dominance.

Contribution of Crenarchaeota and Euryarchaeota to the prokaryotic plankton in the coastal northwestern Black Sea

The NW Black Sea is an area with peculiar hydrological, hydrochemical and biological features (river plume dynamics, coastal upwelling, intense eutrophication, blooms algae). We determined the abundance and distribution of the two major groups of Archaea (Crenarchaeota and Euryarchaeota) in three contrasting sites of the NW Black Sea from May to August 2004 to estimate the contribution of non-extremophilic Archaea to the coastal prokaryotic plankton. Using catalyzed reporter deposition-fluorescence in situ hybridization, Euryarchaeota were found to be particularly prominent (11‐22% of total prokaryotic plankton) in the low-salinity waters during late-spring and summer, whereas Crenarchaeota contributed only � 5% to the prokaryotic community in these waters. The abundance of Crenarchaeota was highest in nutrient- and particle-rich waters and lowest in offshore Black Sea surface waters. These results confirm recent studies on the distribution of planktonic Archaea with Euryarchaeota dominating the archaeal community in surface waters. Statistical analyses indicated significant correlations between crenarchaeotal abundance, ammonia and nitrate concentrations at each sites. Our data show that the archaeal plankton constitute an important and dynamic component of the prokaryotic plankton in the coastal oxygenated waters of the NW Black Sea and might play a significant role in the nitrogen cycle.

Discriminating zooplankton assemblages through multivariate methods: A case for a tropical polluted harbour and Bar-built estuary

A comparative study (June–July 2001) on zooplankton community structure amid polluted conditions in a stagnant harbour and relatively unaffected tidal estuary near Visakhapatnam, on the east coast of India, revealed a marked disparity in species composition and abundance. While the harbour supported a rich population of calanoids (46.4%), the estuary sustained mostly cyclopoids (55.2%). Univariate and multivariate techniques (species diversity, clustering, non-metric multi-dimensional scaling and one-way ANOSIM) revealed the existence of two differing zooplankton assemblages and associated water quality (similarity 50.6%). While the estuary is typified by high amounts of dissolved silica (67.4 ± 17.7 μmol l−1) linked with monsoon influx, the harbour waters revealed abnormal levels of phosphate (40.9 ± 9.2 μmol l−1) and nitrate (15.3 ± 5.41 μmol l− 1) suggestive of intense eutrophication, caused by the discharge of fertilizer-factory waste and domestic sewage. On the basis of routines (e.g. BVSTEP, SIMPER) implemented in Plymouth Routines in Multivariate Ecological Research, it was possible to demonstrate that while species such as Oithona rigida, Oithona brevicornis, crustacean nauplii, gastropod veligers, Acartia spinicauda, and Acartia centrura played a key role in discriminating the zooplankton assemblage in the estuary, Acrocalanus spp. (mainly Acrocalanus gracilis) played a keyed role in harbour waters. Canonical Correspondence Analysis revealed species–environment relationships; for example, while the distribution of Oithona spp. and its associates in the estuary corresponded intimately with high silicate, temperature, and low salinity, it was high salinity, phosphate, and nitrate in the harbour channel that supported a different assemblage of copepods dominated by calanoids.

Is the destabilisation of lake Peipsi ecosystem caused by increased phosphorus loading or decreased nitrogen loading?

Lake Peipsi (3555 km2, mean depth 7.1 m) located on the border of Estonia and Russia is the largest transboundary lake in Europe. L. Peipsi consists of three parts. The shared largest northern part L. Peipsi s.s. (2611 km2, 8.3 m) and the southern L. Pihkva (708 km2, 3.8 m) which belongs mainly to Russia are connected by the river-shaped L. Lämmijärv (236 km2, 2.5 m). The catchment area (44,245 km2 without lake area) is shared between Estonia (33.3%), Russia (58.6%) and Latvia (8%). Intensive eutrophication of L. Peipsi started in the 1970s. The biomass of N2-fixing cyanobacteria was low at heavy nutrient loading in the 1980s. After the collapse of soviet-type agriculture in the early 1990s, the loading of nitrogen sharply decreased. A certain improvement of L. Peipsi s.s. was noticed at the beginning of the 1990s together with the temporary reduction of phosphorus loading from Estonian catchment while in recent years a destabilisation of the ecosystem has been observed. This deterioration has been expressed mainly as intensive blue-green blooms and fish-kills in summer. Reappearance of blooms has been explained by the decrease in N/P loading ratio due to reduced N discharge while in some periods increased phosphorus loading could have supported this trend.

Changes in Fish Biomass under Impact of a Thermal Effluent and Eutrophication in Lake Drūkšiai

In the period 1993–1999, discharged thermal effluent and intensive anthropogenic eutrophication impact on the fish biomass were studied in Lake Drūksiai, the cooler of Ignalina Nuclear Power Plant (INPP). Since 1950, the total biomass of fish has increased 50% and, in addition, great changes have occurred in the biomass of different fish species. In comparison to the period 1950–1975, the total biomass of cold-water stenothermic fish species has decreased more than six times. In comparison to the period 1984–1986, the biomass of stenothermic fish species has increased almost twice (due to the increase in the vendace population). The mean biomass of eurythermic fish species, in comparison to the period 1950–1975, has increased 2.3 times. The biomass of cold-water dwelling stenothermic fish correlated negatively with the mean temperatures of the water surface during the warm season of the year, whereas the biomass of eurythermic fish correlated with the mean temperatures of the water surface positively. A p...

Variations in the chemistry of the Black Sea on a time scale of decades (1960–1995)

We use data collected on 52 cruises from 1960 to 1995 to analyze the decadal variability in basic chemical properties (oxygen, sulfide, nitrate, phosphate and silicate) throughout the water column of the Black Sea. This analysis reveals some new features in the recent evolution of the chemical structure of the Black Sea: an increase in the inventory of sulfide and nutrients in the anoxic zone, a decrease in the inventory of oxygen in the upper layer, and variations in the thickness of the sub-oxic zone. These changes suggest that an increase in the flux of sinking particulate organic matter (POM) has perturbed the biogeochemistry of the Black Sea. The flux balance that controlled the distribution of nutrients before the early 1970s has been modified due to intensive eutrophication. That has led to an increase in the inventory of nutrients in the anoxic zone due to an increased flux of POM. This increased flux of POM increased the rate of sulfate reduction and created an imbalance in the sulfide budget. As a result, sulfide concentrations have increased in the anoxic zone over the past 20 to 25 years. Additional anthropogenic changes are reflected in the distributions of nitrate and oxygen. Climate related and anthropogenic changes in the sources and sinks of these compounds appear to be equally important for causing variations in their inventory. Unlike oxygen and nitrate, the budget of sulfide depends primarily on the flux of sinking POM and the intensity of the lateral flux of oxygen contained in the Bosporus plume. More than 50% of sulfide production appears to be oxidized by the lateral ventilation flux of oxygen. Thus, different processes govern the dynamics of the upper and lower boundaries of the sub-oxic zone. Variations in the upper boundary of suboxic zone depend on consumption of oxygen by the flux of sinking POM, while the lower boundary is controlled by the balance between the upward flux of sulfide within the anoxic zone and the lateral flux of oxygen associated with the Bosporus plume.

No extinctions during Oceanic Anoxic Event 1b: the Aptian-Albian benthic foraminiferal record of ODP Leg 171

Abstract Outstandingly well-preserved benthic foraminiferal successions from upper Aptian-lower Albian sediments at Site 1049 (Leg 171, Blake Nose escarpment, western North Atlantic) provide a detailed record of the faunal turnover across Oceanic Anoxic Event 1b (OAE 1b). Changes in abundance, diversity and species composition reflect strong fluctuations in carbon flux and bottom-water oxygenation. Before the onset of black shale sedimentation, the originally diverse assemblages are replaced by low-diversity associations, dominated by species inferred to be opportunistic phytodetritus feeders and thriving on an enhanced carbon flux to the sea floor. The 46 cm thick laminated black shale horizon corresponding to OAE 1b is virtually devoid of benthic formainifers or contains highly impoverished assemblages, suggesting that intense eutrophication and/or strong stratification triggered near anoxia at the sea floor during black shale deposition. Above the black shale, reoccurrence of the pre-black shale fauna points to relatively rapid bottom-water reoxygenation. The benthic formainiferal record of Leg 171 provides clear evidence that no major extinctions occurred across OAE 1b, as most of the species occurring below the black shale reappear above it. In contrast to other Cretaceous anoxic events, OAE 1b may have been more limited in duration or in geographical and water-depth extent, allowing recolonization from adjacent, more hospitable areas, once local conditions improved at the sea floor. Prolific radiation within the suborder Rotaliina and diversification of Textulariina with calcareous cement appear to have started in the Aptian time before OAE 1b, and continued into early Albian time to give rise to many of the modern lineages.

Effect of urbanization on metal deposition in the bay of Töölönlahti, Southern Finland

A sediment core from the Bay of Töölönlahti in the centre of Helsinki, Finland was analysed by a selective extraction method in order to examine the geochemical impacts of urbanization. Concentrations of Al, Ca, Cu, Fe, Mn and Zn in the extracts and total P and S were measured at intervals of 1 cm to a depth of 100 cm. The data were subjected to principal components analysis. Sedimentation rate was determined using 137Cs- and 14C-measurements and SCP-analysis and it varied from 0.4 to 0.6 mm·yr −1. Most of the background metal deposition in the basin is acid soluble. The intense eutrophication began around 1900 and is reflected in the sediment by a rise in the concentrations of S, P, organically bound Cu, Fe, Mn, Zn and hydroxide Zn, Total Al, Ca and Mn decrease towards the surface, probably because of dilution by organic inputs or by biogenic silica. The total Cu and Zn were high in the surface with a large proportion of labile forms.

An ecological shift in a remote coral atoll of Belize over 25 years

Many coral reefs in the Caribbean, and elsewhere, have undergone changes from hard coral to fleshy algal dominance over the past two decades which has often been interpreted as a localized response to eutrophication and fishing. Here, data on the abundance of hard corals and algae from lagoonal patch reefs distributed throughout a large (260 km2) remote reef atoll located approximately 30 km offshore from the sparsely-populated coast of Belize, Central America, are compared with a study of these patch reefs conducted 25 years previously. Data and observations indicate that these patch reefs have undergone a major change in their ecology associated with a 75% reduction in total hard coral, a 99% loss in the cover of Acropora cervicornis and A. palmata, and a 315% increase in algae, which are mostly erect brown algae species in the genera Lobophora, Dictyota, Turbinaria and Sargassum. Such changes have been reported from other Caribbean reefs during the 1980s, but not on such a remote reef and the present changes may be attributed primarily to both a disease that began killing Acropora in this region in the mid 1980s and a reduction in herbivory. The low level of herbivory may be attributable to the disease-induced loss of the sea urchin Diadema antillarum in 1983, or fishing of herbivorous fishes, but both explanations are speculative. The present density of fisherfolk is low, and their efforts are not targetted at herbivorous fishes, and population densities of D. antillarum 14 years after the mortality are <1 individual per 1000 m2, but there is no comparative data from before the die off. There is, however, no indication that these major changes occurred on the fore reef, because A. palmata is abundant and erect algal abundance is low. We suggest that reported changes in other Caribbean reefs are not necessarily or exclusively influenced by local human factors such as localized intense eutrophication or fishing.

Phytoplankton-metaphyton seasonal dynamics in a newly-created subtropical wetland lake

The dynamics of the algal populations of Lake Agmon, a newly created shallow lake in the Hula Valley, Israel, were monitored following its filling in April 1994 through 1996. Additional limited field observations and measurements were taken throughout 1997. Following an initial establishment period, the dynamics of the algal populations showed a repetitive annual pattern comprised of three phases: I. a clear water phase in January–February, with low phytoplankton biomass and no metaphyton; II. a metaphyton dominance phase during March–June when mats of filamentous chlorophytes covered most of the lake's sediments while phytoplankton biomass remained low; and III. an intense phytoplankton bloom phase from June till December. The shifts from phase I to II and from phase II to III were gradual, resulting from interplay between phosphorus availability, the underwater light climate, temperature effects and zooplankton grazing pressure. The shift from phase III back to phase I was abrupt, due to winter flushing of Lake Agmon. The summer phytoplankton blooms intensified from 1994 to 1996 and shifted from chlorophyte dominance in 1994 and 1995 to cyanobacteria-dominance in 1996 and 1997. These observations, jointly with the nutrient chemistry of Lake Agmon, suggest intense eutrophication. Criteria based on phytoplankton taxonomy also indicate that Lake Agmon is eutrophic to hypertrophic. Due to the typical unstable nature of hypertrophic systems, careful management is essential to maintain the delicate ecological balance needed to ensure that the lake will fulfill its intended role as a center for eco-tourism.

Aquatic vegetation in two pre-alpine lakes of different trophic levels (Lake Bled and Lake Bohinj): vegetation development from the aspect of bioindication

Summary The two lakes studied have some common characteristics as are origin and geological age, however apparent differences can be recognised in morphometry, hydrology, physico-chemical characteristics of water, type of watershed and management approach. Lake Bled is smaller and located in the middle of an urban surroundings. Intensive eutrophication has been an outstanding process in this century, accompanied occasionally with algal bloom. Two restoration measures were introduced to improve the state of the ecosystem but the equilibrium is still fragile. Consequently, aquatic vegetation was subject to constant changes in species composition, their abundance, frequency and depth of distribution. The other ecosystem, which is Lake Bohinj is located in natural surroundings of the Triglav National Park. It is considered as a mesotrophic lake. Littoral is for the most part well developed and in some parts abundantly colonised with macrophytes. Changes in communities were not as obvious and radical as in Lak...

Ecological research on the animal communities of the Po River Delta lagoons

Abstract The main results of research on invertebrate biology and ecology in the lagoons of the Po River Delta (Sacca del Canarin, Sacca di Scardovari, Sacca di Goro) are presented and related to the more significant approaches followed in ecological research during the last two decades. The lagoons, which are intrinsically eutrophic water bodies, have recently undergone intense eutrophication due to the dramatic increase in the Po river nutrient loading. A shift towards a dystrophic state was indicated by the appearance of large Ulva rigida beds in spring and by extensive anoxia during the summer due to the decomposition of the huge macroalgal biomass. Particularly severe dystrophic crises occurred in the Sacca di Goro. Zooplankton and zoobenthos changes were analyzed according to the variations in hydrographic features as well as those in the trophic state of the water. The significance of population dynamics studies in evaluating biological responses to environmental stresses is emphasized. Investigati...

Changes in the hydrochemistry of the Black Sea inferred from water density profiles

DURING the past two decades, catastrophic changes have occurred in the Black Sea ecosystem: the influx of pollution from the major rivers has caused intense eutrophication at the northwest coastal margin1, and fish stocks have collapsed throughout the sea2. The hydrochemical details of these events are still poorly understood3–7, and a way needs to be found to distinguish long-term variations from short-term natural fluctuations3,4 if future management of the Black Sea ecosystem is to be successful. We show here that a coherent description may be achieved by analysing the hydro-chemical data as a function of water density rather than depth. Our findings suggest that, contrary to the suggestion of Murray et al.3, the upper boundary of the low-lying anoxic waters has remained stationary since 1969, whereas the intermediate suboxic zone has enlarged, reducing the overall depth of the oxygenated upper waters by ∼20 m. Moreover, a long-term increase in the nitrate concentration and a concomitant decrease in the silicate and ammonia concentrations in this upper layer are indicative of the considerable changes taking place in the biochemical regime of the Black Sea.

The fish fauna of the Jordan reservoir, one of the oldest man‐made lakes in central Europe

The Jordan reservoir, Czechoslovakia, was constructed in 1492 and the last full drainage and fish removal was in 1830. In this ‘mature’ fish community of 20 species (plus three hybrids), the roach, Rutilus rutilus (L.) (1446 fish ha–1) and beam, Abramis brama (L.) (1074 fish ha–1) dominated the fish stock (total of all species = 3628 fish ha–1). Predatory species made a small contribution to the total (maximum 7.7%, obligatory predators 2%). The contribution (12%) by perch, Perca fluviatilis L., was also low, and its numbers in successive age‐groups showed a steady decrease. The high variability and time‐synchronization in the year‐class strengths of the principal cyprinid species may indicate unstable environmental conditions or intra‐community cycles. The growth rates of non‐predatory species were low. There was a high fishing rate on predatory species but there was little impact by fishery management on the whole ‘mature’ community. Intensive eutrophication from both communal waters and agriculture probably caused the high biomass level (all species) and the low abundance of zander, Stizostedion lucioperca (L.).

Impact de la pollution sur un écosystème méditerranéen cǒtier. II. Relations entre la composition spécifique des populations phytoplanctoniques et les taux de pigments et de nucléotides adényliques (ATP, ADP, AMP)

AbstractInfluences of unsalted waters penetration, in the Gulf of Fos, are marked as much on the primary step structuration level as on the component cellular physiology one. At their outlet, the weak structuration and the considerable biomasses resulting from an intense eutrophication go with a strong mortality clearly shown as well as by ATP/chlorophyll ratio than these of ATP, ADP and AMP inside the adenylic nucleotides pool. The primary step acquires a larger maturity in the salt share of the south eastern area. Spectrum variations of the population specific cellular volumes in terms of population importance can in a certain measure explain the intracellular rate variations into biochemical components.