Nadezhda A. Berezina

Invasions of alien amphipods (Amphipoda: Gammaridea) in aquatic ecosystems of North-Western Russia: pathways and consequences

Since the middle of the 20th century, six species of Ponto-Caspian amphipods (Chaetogammarus ischnus, C. warpachowskyi, Chelicorophium curvispinum, Dikerogammarus haemobaphes, Obesogammarus crassus, Pontogammarus robustoides), one Baikalian amphipod Gmelinoides fasciatus and one amphipod of Atlantic origin Gammarus tigrinus have expanded in Russia and adjacent regions. A wide variety of human mediated vectors such as deliberate and accidental introductions, natural migration via constructed inland waterways and high rates of spread, survival and reproduction in these species have facilitated rapid dispersal and successful establishment of these alien species. Causes of successful establishment of these invaders and potential consequences of the invasions including extinctions of native species in rivers, lakes and estuaries of north-western Russia are discussed.

The causes and consequences of algal blooms: The Cladophora glomerata bloom and the Neva estuary (eastern Baltic Sea)

The biomass dynamics of the green alga Cladophora glomerata was studied in the shallow-water littoral zone of the Neva estuary during May-October of 2003-2005. Additionally, the average production rate of C. glomerata, the biomass of drifting algae and oxygen depletion were examined during period of algae decomposition. Two peaks in C. glomerata biomass, in July and in September, were observed during all years studied, reaching a maximum 300+/-100 g DW m(-2). The primary production of C. glomerata varied from 3.6 to 7.9 g C m(-2) contributing to around 90% of the total primary production in this habitat. From the middle of July to late August the biomass of drifting C. glomerata exceeded the biomass of the attached algae, accounting for 62% of the total algal biomass in shallow areas (0-1m). The hypoxia (a minimum oxygen level of 5% or 0.62 mg dm(-3)) in the water was recorded near shore (to 20-m distance from the shore), negatively influencing the quality of shallow-water habitats.

Alien Malacostracan Crustaceans in the Eastern Baltic Sea: Pathways and Consequences

The recent invasion history of malacostracan crustaceans into the eastern Baltic Sea is reviewed with 16 alien species being recorded from the easternmost area. These invasives constitute 3% of the total species richness (50% of the alien biota), and comprise up to 80% of the total benthic biomass in several localities. The Ponto-Azov-Caspian species are the most diverse and abundant component. Their taxonomical and ecological dominance could be explained by a combination of factors including similarities between the Baltic, the donor regions and the waterway network that allows their dispersal. The high vulnerability of the Baltic Sea to invasion may be a consequence of low native biodiversity coupled with anthropogenic and natural factors. The potential impact of alien Malacostraca on the native community was assessed following predatory studies of alien amphipods on native benthic biota. These studies indicated that the alien amphipods may alter the structure of their prey communities. Alien crustaceans have outnumbered or even completely replaced native species and/or earlier established invaders locally in the eastern Baltic Sea.

Changes in the aquatic systems of north-eastern Europe after invasion by Gmelinoides fasciatus

The main pathways which have caused an increase in the dispersal rate of amphipods in Europe are associated with human activity (Jaz . dz . ewski 1980). Destruction of natural geographic barriers has resulted in range expansions of many amphipod species in different directions. For example, since the 20th century, eight amphipod species of Ponto-Caspian, Baikalian, and Atlantic origin have expanded widely within Russia due to both several human-mediated vectors (shipping, intentional and accidental introductions, or natural migration via the constructed waterways of Europe) and the elevated plasticity of some non-indigenous species (Alimov and Bogutskaya 2004). The successful establishment of non-indigenous amphipod species at new locations and often the consequent local extinction of indigenous species are the main causes of structural alterations of natural habitats. According to Elton (1958), each introduction of a new species, whether followed or not by an explosion of its density, exerts some influence on the indigenous communities and ecosystem stability. Even a relatively small number of specimens may be sufficient to cause severe damage in the recipient ecosystem (Mack et al. 2000). Especially in the cases of addition of functionally dominant species (keystone

SEDIMENT QUALITY ASSESSMENT USING GMELINOIDES FASCIATUS AND MONOPOREIA AFFINIS (AMPHIPODA, GAMMARIDEA) IN THE NORTHEASTERN BALTIC SEA

Crustaceans in the order Amphipoda are sensitive organisms for the assessment of sediment quality. In this work we performed 10-day toxicity tests on muddy sediments collected from a total of 29 sites in the Gulf of Finland, the Gulf of Riga and the Gulf of Bothnia (northeastern Baltic Sea) using Baltic Sea species such as the native amphipod Monoporeia affinis (Bousfield, 1989) and the invasive amphipod Gmelinoides fasciatus (Stebbing, 1899), and also compared these results with those of bioassays carried out using the standard test species, laboratory-cultivated amphipod Hyalella azteca (Saussure, 1858). The sediment samples (three cm of the upper layer) were collected by a GEMAX Dual Corer during the R/V “Aranda” cruises in August and September of 2009 and 2010. Toxicity of sediments in bioassays with M. affinis and G. fasciatus gave varied results depending on the amphipod species used. The lowest quality of sediments determined using M. affinis was recorded at sites located in the offshore and deepwater areas (60-100 m depths) of the Gulf of Finland characterized by hypoxic/anoxic conditions. Toxicity testing applying G. fasciatus showed that sediments at >50% of the study sites in the Gulf of Finland and in the Gulf of Riga can be assessed as highly contaminated. Males of G. fasciatus were significantly more sensitive to potential contamination in sediments than females. The lower survival of males under contaminant stress may result in a skewed sex ratio in natural populations and in a decline of reproduction success. The survival rate of G. fasciatus in the toxicity tests correlated positively with the Shannon diversity index (calculated for macrozoobenthos at the study sites), weight losses on ignition (%) in sediments, and it also showed a negative relation with the bottom water oxygen content (mg/l). The results suggest that G. fasciatus is the more sensitive species of the three amphipods tested and can be used as a indicator of sediment quality in the Baltic Sea and other water bodies.

PREDATION RATE AND SIZE SELECTIVITY OF THE INVASIVE AMPHIPOD GMELINOIDES FASCIATUS PREYING UPON THE NATIVE ISOPOD ASELLUS AQUATICUS

Experimental studies were carried out on the predation pressure of the invasive Baikalian amphipod Gmelinoides fasciatus on the native isopod Asellus aquaticus to explain the decrease in the density of this native after a successful establishment of G. fasciatus in many aquatic systems of eastern Europe. Experimental results confirmed that adult males of G. fasciatus preyed upon A. aquaticus. Predation rates of G. fasciatus varied from 0.28 to 1.07 ind. day-1, depending on prey density, with a maximum rate at a prey density of 30?40 ind. dm-2. Although amphipods showed the absence of selectivity to prey size (-0.5 < I < +0.5), the positive selectivity index (I = +0.37) of G. fasciatus feeding obtained for small-sized isopods (3.8 mm) indicates the preference for juveniles over larger adult isopods (7.2 and 9.5 mm). Our experiments conclude that the amphipod G. fasciatus may have a strong impact on the density of A. aquaticus in natural habitats, because the potential maximum losses of A. aquaticus from th...

A relative contribution of carbon from green tide algae Cladophora glomerata and Ulva intestinalis in the coastal food webs in the Neva Estuary (Baltic Sea)

We analyzed stable isotope composition of carbon and nitrogen of suspended organic matter (seston) and tissues of macroalgae, macroinvertebrates and fish from the coastal area of the highly eutrophic Neva Estuary to test a hypothesis that organic carbon of macroalgae Cladophora glomerata and Ulva intestinalis produced during green tides may be among primary sources supporting coastal food webs. The Stable Isotope Bayesian mixing model (SIAR) showed that consumers poorly use organic carbon produced by macroalgae. According to the results of SIAR modeling, benthic macroinvertebrates and fish mostly rely on pelagic derived carbon as a basal resource for their production. Only some species of macroinvertebrates consumed macroalgae. Fish used this resource directly consuming zooplankton or indirectly via benthic macroinvertebrates. This was consistent with the results of the gut content analysis, which revealed a high proportion of zooplankton in the guts of non-predatory fish.

Excretion by Benthic Invertebrates as Important Source of Phosphorus in Oligotrophic Ecosystem (Lake Krivoe, Northern Russia)

We studied contribution of benthic invertebrates to the dissolved phosphates flux from the bottom sediments to the water in an oligotrophic lake (Lake Krivoe, near the White Sea biological station “Kartesh”, Northern European Russia) in 2009-2013 with the aim to quantify specific (among and within taxa), spatial (littoral and deep sites) and seasonal variability. The excretion rates (Pexc) of soluble reactive phosphorus (SRP) were estimated in experiment with dominating taxa of benthic invertebrates (amphipods, oligochaetes, mollusks, and chironomids), freshly collected from the lake. Mass-specific P excretion rate was calculated as Pexc divided by animal dry mass and further used for calculations of benthic P efflux rates. Also, in other experimental series with and without animals (amphipods) we measured extracellular alkaline phosphatase activity. The results showed that the SRP excretion rates varied significantly between taxa and between different-sized individuals within the same taxa (the SRP excretion rate elevates with an increase in individual weight). Notable spatial and seasonal differences in biomass of benthic animals and phosphorus released by them in the lake were found. The calculated phosphorus efflux by excretory activity of benthic animals was more intensive in littoral sites (up to 14.4 μmol m-2d-1 in July), that 7 times greater than maximum efflux in deep areas (2.2 μmol m-2d-1). The mobile burrowing animals (the amphipods Gammarus lacustris, Monoporeia affinis, and Gammaracanthus loricatus) are able to move from the bottom sediments to water and transfer the nutrient; they contributed 80 % of P flux caused by benthic excretion in the lake and affected the activity of the extracellular alkaline phosphatase, increasing its level in water

The meio- to macrozoobenthos ratio in a lake benthic community: Dynamic aspect

Multiyear data (2002−2015) on the biomasses of meio- and macrozoobenthic communities have been studied at different depths of a small lake in northern Karelia. A trend towards anti-phase changes in meio- and macrobenthic biomasses was observed and, as a consequence, the ratio between these components varied significantly in different years. Thus, inter-annual dynamics should be taken into account in analysis of hydrobiological data.

Sediment biotesting in the Baltic Sea : The CONTEST Project

Sediments contaminated by human activities usually contain a mixture of chemicals that produce unforeseen combined toxic effects in organisms. Thus, traditional risk assessments based on the concen ...