Assessment of the Neva Estuary ecosystem state on the basis of structural characteristics of benthic animal communities in 1994–2005

In the years 1994–2005, the values of the integrated index IP’ at some stations of the Neva Bay changed from 38.1 to 81.9%, water quality changed from class 3 to class 5, and the states of some areas of the ecosystem that were evaluated as “tense” went to “catastrophic.” The integrated mean assessment of water quality according to the IP’ index over the entire Neva Bay throughout 12 years (1994–2005) remained relatively stable, waters were assessed as “polluted” (fourth class), and the state of the ecosystem was considered “critical.” The state of the eastern part of the Gulf of Finland in 1994–2005 was less favorable. The species diversity of zoobenthos in the resort zone of the eastern part of the Gulf of Finland is considerably lower than in the Neva Bay. Waters of the resort zone of the eastern part of the Gulf of Finland in 1994–2005 were assessed as one class lower than in the Neva Bay, i.e., as “polluted-dirty” (fourth-fifth class), and the state of the ecosystem was assessed as being in a “crisis.” In the resort zone, there was a decline in species diversity and abundance and biomass of benthic animals; i.e., all characteristics of the degradation of benthic animal communities were observed.     

Response of eutrophication in the eastern Gulf of Finland to nutrient load reduction scenarios

The trophic status of the eastern Gulf of Finland, where the largest Baltic metropolis St. Petersburg sits at the mouth of the largest Baltic river Neva, is elevated but existing recommendations on water protection measures are controversial. In this study, the effects of nutrient load reductions on this ecosystem were estimated with the aid of a three-dimensional coupled hydrodynamic-biogeochemical model. As a reference, the contemporary seasonal dynamics were simulated with nutrient inputs corresponding to the recent estimates of point and riverine sources. In order to eliminate the effects of natural inter-annual variations, the computations were run under recurrent annual forcing for 3 years, until quasi steady-state seasonal dynamics were reached. Reasonable comparability of simulated concentrations and biogeochemical fluxes to available field estimates provides credibility to scenario simulations. These simulations show that substantial reductions of nutrient point sources in St. Petersburg would affect only the Neva Bay as the immediate receptor of treated sewage waters, where primary production could decrease by up to 20%. Eutrophication in the other parts of the Neva Estuary and in the entire eastern Gulf of Finland would change insignificantly owing to increased nutrient import from the offshore waters. Therefore, more significant changes can occur only via a reduction in nutrient pools in the open Gulf of Finland and the Baltic Proper, which would require a longer time. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Structure of littoral zoocenoses in the macroalgae zones of the Neva River Estuary

The biodiversity and spatial distribution of macrofauna biomass are studied for 12 sites of stonesand littoral in the Neva Estuary in 2002–2005. The highest biodiversity has been observed for chironomids and oligochaetes in the Neva Bay (36% and 24% of total species number) and in the eastern Gulf of Finland (33% and 23%). Amphipods (≤89%), molluscs (≤61%), and chironomids (≤37%) dominate by biomass. The biomass spatial distribution vary dramatically from 9 to 37 g m⁻² in the freshwater Neva Bay and from 1 to 68 g m⁻² for the other Neva Estuary areas. The bottom fauna biomass in the Neva Bay is significantly lower than in the 1980–1990’s and constitutes 20–50% of the biomass previously observed. We explain such a significant decrease by a reduction of the insects and aborigine crustaceans Gammarus lacustris Sars and Asellus aquaticus L. The invasive amphipod species Gmelinoides fasciatus (Stebbing) dominated by biomass for the study period (3.8–15.6 g m⁻², or >30% of total macrozoobenthos biomass).     

Rotifer assemblages in the Neva Bay,Russia: principles of formation,present state and perspectives

A comparative study of species composition, abundance and spatial distribution of the rotifers of Neva Bay (Gulf of Finland, Baltic Sea), between 1982–1993, was carried out. The rotifer fauna in the central basin of Neva Bay is determined by and originates in Lake Ladoga and is very similar to that of the Neva River. High turbidity and effect of winds affecting water residence time influence composition and density of rotifers in this shallow estuary. The importance of rotifer assemblages for evaluation of the quality of the estuary is discussed.     

Distribution,population structure and salinity tolerance of the invasive amphipod Gmelinoides fasciatus (Stebbing) in the Neva Estuary (Gulf of Finland,Baltic Sea)

In the early 1970s, the Baikalian amphipod Gmelinoides fasciatus (Stebbing) was intentionally introduced into several lakes in the Gulf of Finland basin in order to enhance fish production. By 1996, G. fasciatus successfully colonized the littoral zone of Lake Ladoga and, via the Neva River, invaded the Neva Bay, the freshwater part of the Neva Estuary. In 1999, G. fasciatus was first registered in the inner Neva Estuary, the very first record of the Baikalian amphipod in brackish waters of the Baltic Sea. Distribution, abundance, reproduction and population structure of G. fasciatus in the Neva Estuary were studied during 1998–2000. In some locations of the Neva Estuary, maximum densities of G. fasciatus reached 3500 ind. m⁻². In general, density and biomass of G. fasciatus in the freshwater part of the Neva Estuary were higher (around 1.5 fold) than in the brackish-water part. Fecundity of this amphipod averaged 10–20 eggs per female, depending on body size of females and season. In order to assess the possibility of further spread of G. fasciatus in the Baltic Sea, the salinity tolerance of this species was determined in a series of laboratory experiments. Our results showed that the invasive amphipod G. fasciatus is potentially able to colonize shallow coastal habitats of, for example, the Gulf of Bothnia, Gulf of Riga and other parts of the Baltic Sea with water salinities ranging from 1 to 5 psu.

     

Evidence for predatory control of the invasive round goby

We coupled bioenergetics modeling with bottom trawl survey results to evaluate the capacity of piscivorous fish in eastern Lake Erie to exert predatory control of the invading population of round goby Neogobius melanostomus. In the offshore (>20 m deep) waters of eastern Lake Erie, burbot Lota lota is a native top predator, feeding on a suite of prey fishes. The round goby invaded eastern Lake Erie during the late 1990s, and round goby population size increased dramatically during 1999–2004. According to annual bottom trawl survey results, round goby abundance in offshore waters peaked in 2004, but then declined during 2004–2008. Coincidentally, round goby became an important component of burbot diet beginning in 2003. Using bottom trawling and gill netting, we estimated adult burbot abundance and age structure in eastern Lake Erie during 2007. Diet composition and energy density of eastern Lake Erie burbot were also determined during 2007. This information, along with estimates of burbot growth, burbot mortality, burbot water temperature regime, and energy densities of prey fish from the literature, were incorporated into a bioenergetics model application to estimate annual consumption of round goby by the adult burbot population. Results indicated that the adult burbot population in eastern Lake Erie annually consumed 1,361 metric tons of round goby. Based on the results of bottom trawling, we estimated the biomass of yearling and older round goby in offshore waters eastern Lake Erie during 2007–2008 to be 2,232 metric tons. Thus, the adult burbot population was feeding on round goby at an annual rate equal to 61% of the estimated round goby standing stock. We concluded that the burbot population had high potential to exert predatory control on round goby in offshore waters of eastern Lake Erie.     

The influence of seasonal and year-to-year variability of water discharge from the Lake Ladoga—Neva River system on the salinity regime of the Baltic Sea

The study is based on multi-year monthly and yearly averaged time series of the Neva River discharge, monthly salinity observations from near-shore hydrographic and hydrometeorological stations in the Gulf of Finland, and several years of data from international seasonal salinity observations in the open region of NE Baltic Sea. There is a good coherence between seasonal variations of the Neva River flow and the salinity regime in the upper layer of the Baltic Sea. Near the shores periods of low, normal and high salinity correspond to the periods of high, normal and low river runoff, and the same trends are observed with some time lag in the open parts of the Sea as well. The impacts of the Neva River discharge oscillations on salinity of the Gulf of Finland surface waters are analyzed in terms of time regression probability models. The obtained river flow-marine salinity transfer functions summarize well the observation data on both multiannual and seasonal scales of variability. Some seasonal periods with different anomalies of the influence are distinguished.     

Effects of pollution on benthic invertebrate communities of the St. Marys River, 1985

A survey was undertaken in 1985 to assess spatial and temporal trends in the benthic community structure in relation to sediment contamination and wastewater sources at 70 stations between Whitefish Bay and lower Lake George in the St. Marys River. Cluster analysis identified seven benthic communities. Three were identified as pollution impacted, based on a preponderance of tubificids and nematodes, usually at high densities (up to 259 000 m^-2), but sometimes at low densities (< 100 m^-2) at individual stations. Impacted communities occurred downstream of industrial and municipal sources and in depositional areas, and were confined mainly to Canadian waters. Unimpacted communities had greater numbers of taxa, and occurred upstream of point sources, along the U.S. shoreline, and in most areas of downstream lakes. Impacted and unimpacted communities were separated along particle size and contaminant gradients in river sediments. Despite recent reductions in pollutant loadings and improvements in sediment quality, no major changes were apparent in the status of the benthic community from earlier surveys.     

A survey of toxicity of cyanobacterial blooms in Lake Ladoga and adjacent water bodies

Twentyfive cyanobacterial blooms in Lake Ladoga and adjacent water bodies were studied in the summer of 1990–1992. Toxicity of the water bloom material for mice was detected in 9 cases. The maximal tolerable doses (MTD) of the material extracted from biomass varied within 3–30 mg kg^–1 mouse body weight; 50% lethal doses (LD₅₀) were within 45–125 mg kg^–1. Toxic water blooms were registered in Karelian lakes and in the Neva Bay, Gulf of Finland. Cyanobacterial samples collected on the eastern coast of Lake Ladoga proved to be non-toxic. The species identified in toxic bloom material included Anabaena circinalis, A. flos-aquae, A. lemmermannii, Anabaena sp., Aphanizomenonflos-aquae, Gloeotrichia echinulata, G. pisum, Microcystis aeruginosa and Oscillatoria sp. These data suggest that toxic forms of cyanobacteria are widespread in Karelian lakes belonging to the drainage basin of Lake Ladoga.     

Establishment of the zebra mussel,Dreissena polymorpha (Pallas), in the Neva Estuary (Gulf of Finland,Baltic Sea): distribution,population structure and possible impact on local unionid bivalves

Hydrobiologia - The zebra mussel, Dreissena polymorpha (Pallas), has invaded the Neva Estuary (eastern Gulf of Finland) by mid 1980s. In order to assess the current status of the zebra mussel...     

The multidimensional space of integral characteristics: Invariance of its structure to various biocenotic assemblages

In the virtual multidimensional space of integral biocenotic characteristics, such as abundance, the sizes of individuals, and the components of species diversity, which are scaled on corresponding coordinate axes, the points that represent samples from various biocenotic assemblages, form similar multi-layered hill-shaped figures. The examples we considered are the pelagic macrofauna of the Bering Sea, the Sea of Okhotsk, the Sea of Japan and the adjacent waters of the Northwestern Pacific Ocean; the phytoplankton, zooplankton, and zoobenthos of Lake Ladoga, the Neva Bay, and the Gulf of Finland in the Baltic Sea; the beetle guild in the rainforest of Borneo Island on the Malay Archipelago; and the bird taxocenes and biotope groups of soil mites in North America, among others. The obvious similarity of the composed diagrams results from the close interrelationships of all the integral characteristics and also from the universality of the structure of links between them, which is tolerant to movements in the real space-time continuum and invariant towards the subject of the studies. The multidimensional domain of the analyzed variables is a set of points that are aggregated along a segment, whose length and orientation relative to the coordinate axes determine the general rules of the biocenotic organization of the living matter.     

Macroalgal blooms and species diversity in the Transition Zone of the eastern Gulf of Finland

The Macroalgal flora of the Transition Zone of the eastern part of the Gulf of Finland was studied between 2003 and 2008. Sixteen species were found from a depth of 0.5–5 m. Three species (Cladophora aegagropila, Pseudolithoderma subextensum and Hildenbrandtia rubra) are listed as rare in The Red Data Book of Nature of the Leningrad Region (Tzvelev, 2000). Nine species are recorded here for the first time in Transition Zone of eastern Gulf of Finland. The dominant species growing at a 0.5–1.5 m depth was the green alga Cladophora glomerata. Our study shows that in 2003–2008 in the shallow (0.5–1.5 m) zone of the eastern Gulf of Finland, the biomass of C. glomerata peaks several times in a season reaching 450 ± 130 g DW m⁻². Our study corrects earlier data for the species composition of macroalgae and describes their depth and horizontal distribution in the Gulf of Finland.     

A Comparison of the Benthic Bacterial Communities Within and Surrounding <Emphasis Type="Italic">Dreissena</Emphasis> Clusters in Lakes

The impact of Dreissena (Dreissena polymorpha and D. bugensis) on the benthic bacterial community in lakes is largely unknown. Therefore, we quantified differences in the structure and activity of bacterial communities living in sediments (1) associated with Dreissena clusters, and (2) unassociated with established clusters (lake bottom sediments). Dreissena clusters and sediments were collected from locations in Lake Erie, Lake Ontario, and several inland lakes. Denaturing gradient gel electrophoresis (DGGE) analysis of the benthic bacterial community showed that the bacterial populations selected for by Dreissena represent a subset of the bottom communities and are geographically distinct. Community-level physiological profiling (CLPP) showed that overall bacterial activity and metabolic diversity were enhanced by the presence of clusters in all samples, with the exception of those harvested from the two Lake Erie sites. Therefore, Dreissena appears to affect both structure and metabolic function of the benthic bacterial community and may have yet unexplored ecosystem and food web consequences.     

Bioassessment of Selected Inland Water Bodies in Sri Lanka Using Benthic Oligochaetes with Consideration of Temporal Variations

The organic pollution status of three inland water bodies in Sri Lanka was evaluated using benthic oligochaete communities with the environmental characteristics considering temporal variation over one year period. Oligochaete species richness and abundance was consistently higher in the highly eutrophic and organically polluted Lake Beira in comparison with the less polluted water bodies. In a cluster analysis of oligochaete community compositions, the assemblages grouped by the water bodies rather than by months. Principal component analysis revealed that the structure of the oligochate community was mainly influenced by conductivity, nitrate, biochemical oxygen demand levels of water and organic carbon content of the sediment. In the ordination, the polluted Lake Beira separated from the other water bodies along the first axis. The results revealed that there could be a potential for using benthic oligochaetes for bioassessment of inland water bodies in Sri Lanka. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Impact of bleached kraft pulp mill effluent on benthic community structure in relation to environmental factors

In this study, we assessed the impact of bleachedkraft pulp mill effluent (BKME) on the distributionand composition of benthic communities at JackfishBay, Lake Superior. Sediment samples were collectedfrom 44 stations from which several environmentalvariables (extractable organic chlorine [EOCl],metals, organic carbon, particle size, secchi depth,and water depth) and benthic community compositionwere determined. Relationships between environmentalvariables and benthic community structure wereassessed using canonical correspondence analysis(CCA). CCA revealed two distinct biological gradientsat Jackfish Bay, the first associated with degradedbottom sediments and nutrient enrichment and thesecond associated with water depth. Both gradientsrevealed three distinct regions at Jackfish Bay: 1) anarea of highly degraded sediments, located 300–1200 mbelow the outfall, 2) a small, mesotrophic (nutrientenriched) area adjacent to this zone, and 3) remainingareas of Jackfish Bay, including the internalreference sites in Tunnel Bay. Sediments in theimpaired region contained high concentrations oforganic matter (7–21% as loss on ignition [LOI]) andEOCl (up to 5200 mg/kg dw); together these variablesaccounted for 73% of the variation associated withthe first canonical axis of the CCA. This region wasdominated by the oligochaetes Tubifex tubifexand Limnodrilus hoffmeisteri (64–100% of thebenthic community). Sediments in the second regionwere characterized by an abundant and diverse benthiccommunity comprised of benthic harpacticoids,Chironomidae, and oligochaetes. Stations outside ofthese two regions were characterized by a benthiccommunity similar in composition to that expected foroligotrophic Lake Superior waters, including Diporiea sp., Stylodrilus heringianus, Mysis relicta, Sphaerium, Pisidium and benthicharpacticoids. Based on a Monte Carlo significancetest, benthic community structure was significantly(p = 0.01) related to the environmental variablescomprising the first axis of the CCA. Water depth wasthe most important explanatory variable associatedwith the second axis of the CCA; both taxa richnessand abundance declined significantly with increasingdepth. The comprehensive approach employed in thisstudy clearly delineated the occurrence and degree ofimpact on the benthic environment and may be useful infuture risk assessments of sites affected byanthropogenic activity.     

Long-term changes in a benthic assemblage associated with artificial reefs

The aim of the study was to evaluate the long-term development of a hard bottom benthic assemblage over a period of 20 years in an area off the mouth of a large river. The artificial reef of Fregene was selected because benthic assemblage data were available for the period 1981–1992. This artificial reef is located in the mid Tyrrhenian Sea, 5 nautical miles north of the two mouths of the Tevere River (Latium, Italy) and 1.5 nautical miles offshore from Fregene (Rome, Italy). The artificial reef was deployed in March 1981 for fisheries enhancement in 10–14 m of water on a sandy-silty seabed. The Tevere River carries suspended materials and a heavy load of organics since it transports Rome’s effluent, resulting in the eutrophic state of area waters. Benthic sampling was conducted in 2001 by SCUBA diving; two standard surfaces of 400 cm² were scraped from the vertical walls of the same uppermost block in four different periods. All organisms were identified and counted. The methodology used is the same as that adopted in the previous periods, so that the 2001 data could be compared with past collected data. The benthic assemblage was analysed by cluster analysis using the Bray-Curtis index and clustered using the group average clustering algorithm. The SIMPER procedure was used to identify those taxa that characterize each station group identified by cluster analysis. Changes in benthic assemblages and hydrological trends of the Tevere River were investigated using the cumulative sum series method. The 20-year development of the benthic community, starting from the new substratum, is composed of different phases characterised by different benthic assemblages. In particular five different phases were distinguished: 1. Pioneer species recruitment (May 1981–June 1981); 2. Mytilus galloprovincialis (mussel) dominance (August 1981–November 1983); 3. M. galloprovincialis regression (July 1984–October 1985); 4. M. galloprovincialis absence (91–92); 5. Bryozoans bioconstruction dominance (2001). The dynamic succession of the observed benthic assemblages exhibited a good relation with the Tevere River flow. The Tevere River flow, and the subsequent sedimentation process, seems to have strongly influenced the benthic assemblage succession of the Fregene artificial reef. Guest editors: G. Relini & J. Ryland Biodiversity in Enclosed Seas and Artificial Marine Habitats     

Abundance and ecological significance of the clam Rangia cuneata (Sowerby, 1831) in the upper Barataria Estuary (Louisiana,USA)

We proposed that Rangia cuneata (Sowerby, 1831) is an important estuarine bivalve with ecological significance in three coastal lakes in Barataria Bay, Gulf of Mexico—Lake Cataouatche, Lake Salvador and Lac des Allemands. Our goals were to determine the abundance and distribution of Rangia in these lakes and to measure clearance times to elucidate its potential impacts on phytoplankton communities. The estimated average densities of R. cuneata in Lake Cataouatche, Lake Salvador, and Lac des Allemands were 63, 157, and 107 individuals m⁻², respectively, which is 30% lower than that observed in nearby Lake Pontchartrain. The size of clams in Lake Salvador was between 4 and 50 mm, while individuals in Lake Cataouatche and Lac des Allemands were mostly >20 mm. We postulate that a relatively infrequent large tropical storm transported the larvae from Lake Salvador to the other two lakes 1 year before our sampling to create this size difference. The clams were up to 99.9% of the total benthic biomass in Lake Salvador, 15.9% in Lake Cataouatche, and 40.0% in Lac des Allemands. The R. cuneata biomass values were between 16.2 and 27.6 g m⁻² and the clearance times were 1.0–1.5 days. The clearance times are among the highest previously reported for coastal bivalve communities, which were from cooler climates. The results demonstrate that Rangia can be a critical part of the ecological processes in shallow water systems of the Gulf of Mexico.     

Spatial distribution of zoobenthos in the watercourses of the Biya River basin (Altai)

The composition and spatial distribution of macrozoobenthos were studied in 26 watercourses of the Biya River basin from 1997 to 2004. The bottom fauna of the basin’s rivers includes 382 species, 217 genera, 81 families, 21 orders, 11 classes, and 7 types of invertebrates. Species common in the northern and eastern Palearctic prevail, presumably evidencing the oriental origin of the rheophylic benthic fauna. Four basic and two intermediate types of benthic communities were revealed. These communities differ in the structures of the complexes dominant by biomass. The successive substitution of the communities from the upper reaches of Lake Teletskoye tributaries to the Biya mouth depends on factors related to the basin’s relief and corresponds to changes in the landscape and hydrological conditions. This substitution generally conforms to the concept of river continuum.     

European smelt Osmerus eperlanus in the eastern Gulf of Finland,Baltic Sea: Stock status and fishery

In the eastern Gulf of Finland, European smelt Osmerus eperlanus occurs as an anadromous ecological form that spawns in coastal, low-salinity zones and in several rivers entering the gulf, most importantly in the River Neva. Osmerus eperlanus is a key commercial fish species for the population of St. Petersburg, and the city's fish symbol. However, the state of the smelt stock has considerably deteriorated over the past few decades. Monitoring shows that annual catches during 1965–1992 averaged 2274 t, compared to 292 t in 2002–2017, although some improvement is inidicated by a gradual increase in catches in recent years (e.g., to 595 t in 2017). This paper addresses long-term and recent changes in the fisheries for smelt in the eastern Gulf of Finland, including both commercial and recreational fisheries, and the range of fishing gears used. The commercial smelt fishery is mainly conducted during the spawning period (April–May) on migrating fish, using trap nets of various designs and beach seines. There has been an increase in recreational fisheries for smelt; in years when ice cover on the gulf during winter (December–April) is steady, recreational fishers from St. Petersburg, using hook and line, may catch quantities that are comparable to those of commercial catches. Several factors may account for the stock dynamics and associated changes in catches of smelt: these include a decrease in prey availability in the gulf; loss and degradation of spawning and nursery habitats, partly associated with large-scale hydroengineering operations in Neva Bay; and illegal, unreported and unregulated (IUU) fishing which became widespread in post-Soviet decades. In spite of a gradual increase in smelt abundance in the most recent 15 years, a failure to accurately monitor and manage the extent of IUU and recreational fishing for smelt, to assess the status of the stock, or to forecast catches, increases the risk of overfishing of the spawning stock.     

The multidimensional space of the integral characteristics of biocenotic assemblages: The self-similarity or scale invariance of its structure

In a virtual multidimensional space whose coordinate axes are integral characteristics, such as logarithms of the abundance and size of individuals, as well as the components of species diversity, the points that correspond to samples from various biocenotic assemblages form multilayered geometric figures of a similar shape. As was shown based on examples of pelagic macrofauna in the Bering Sea, Sea of Okhotsk, Sea of Japan, and adjacent waters of the Pacific Ocean, as well as phytoplankton, zooplankton, and zoobenthos in Lake Ladoga, Neva Bay, and the Gulf of Finland in the Baltic Sea, these figures possess some properties of fractals. This phenomenon results from the multidimensional domain of the integral characteristics, in which a multitude of points is aggregated along a segment, whose length and orientation relative to the coordinate axes reflects universal power laws at the biocenotic level of the organization of matter; power laws, such as y = a · x ^b , are known to be an unlimited source of self-similarity and scale invariance.