Planktonic Ciliates of the Neva Estuary (Baltic Sea): Community Structure and Spatial Distribution

Ciliate communities in open waters of the meso-eutrophic Neva Estuary (the Baltic Sea) were studied in summer 2010. Abundance and biomass of ciliates were surprisingly low (0.03–1.9 ind ml–1 and 0.04–2.4 × 10–3 μg C ml–1), especially in samples with high detritus content. During this study we detected four ciliate species which are new for the Baltic Sea. Mixotrophic ciliates dominated at the majority of stations (28–67% of overall ciliate numbers). Their contribution was significantly higher in the outfall area and northern part of the Neva Estuary (Resort District), where total density of ciliates was low. Medium-sized ciliates (30–60 μm) were the most diverse and abundant (average contribution 59% of total abundance). The two parts of the estuary, separated from each other by a storm-surge barrier, differed slightly in their community structure (p < 0.05) but did not significantly differ in ciliate numbers and biomass values

Status of Biodiversity in the Baltic Sea

The brackish Baltic Sea hosts species of various origins and environmental tolerances. These immigrated to the sea 10,000 to 15,000 years ago or have been introduced to the area over the relatively recent history of the system. The Baltic Sea has only one known endemic species. While information on some abiotic parameters extends back as long as five centuries and first quantitative snapshot data on biota (on exploited fish populations) originate generally from the same time, international coordination of research began in the early twentieth century. Continuous, annual Baltic Sea-wide long-term datasets on several organism groups (plankton, benthos, fish) are generally available since the mid-1950s. Based on a variety of available data sources (published papers, reports, grey literature, unpublished data), the Baltic Sea, incl. Kattegat, hosts altogether at least 6,065 species, including at least 1,700 phytoplankton, 442 phytobenthos, at least 1,199 zooplankton, at least 569 meiozoobenthos, 1,476 macrozoobenthos, at least 380 vertebrate parasites, about 200 fish, 3 seal, and 83 bird species. In general, but not in all organism groups, high sub-regional total species richness is associated with elevated salinity. Although in comparison with fully marine areas the Baltic Sea supports fewer species, several facets of the system's diversity remain underexplored to this day, such as micro-organisms, foraminiferans, meiobenthos and parasites. In the future, climate change and its interactions with multiple anthropogenic forcings are likely to have major impacts on the Baltic biodiversity

Small details of big importance: Carbon mass determination in the invasive cladoceran Cercopagis pengoi (Ostroumov, 1891) by the high temperature combustion method

Volume: 33Start Page: 19End Page: 3

Small details of big importance: Carbon mass determination in the invasive cladoceran Cercopagis pengoi (Ostroumov, 1891) by the high temperature combustion method

Carbon mass of the non-indigenous predatory fishhook water flea Cercopagis pengoi (Ostroumov, 1891) from the eastern Gulf of Finland, the Baltic Sea, was for the first time measured using the high temperature combustion method. Prior to the analysis, individual dry weight of Cercopagis was determined; altogether ca. 500 organisms were examined. Mean individual dry weight of C. pengoi for July-September was estimated as 34.0 μg; carbon mass averaged 15.8 μg; carbon content, calculated as percent of dry weight, averaged 43.4%. Those values varied over months, mainly because of different population structure of C. pengoi and variation in their diet due to seasonal dynamics of the food objects. However, relations between carbon mass and dry weight for different months did not differ statistically (p<0.001). Therefore, the general polynomial regressions (k=2), describing carbon mass-to-dry weight and carbon content-to-dry weight relationships, were calculated for the entire dataset of individual measurements of C. pengoi body metrics. These data will contribute to adequate evaluation of food web structure and ecosystem alterations in various water bodies invaded by C. pengoi which has got a strong potential to pelagic food web transformations that may impact the overall energy balance and decrease the size of fish stocks

Wide ecological niches ensure frequent harmful dinoflagellate blooms

Harmful algal blooms (HABs) and their consequences cause multiple devastating effects in various freshwater, brackish and marine ecosystems. However, HAB species at moderate population densities have positive ecological roles as primary producers of organic matter and food for zooplankton and fish. They also enhance benthic-pelagic coupling and participate in the biogeochemical cycles. The consequences of HABs are transported across the conventional environmental boundaries by numerous cascade effects in the food webs and beyond. Meanwhile, forecasts of bloom events are still limited, largely because of scarcity of reliable information on ecological niches of the bloom-forming algae. To fill up this knowledge gap, this study focused on dinoflagellates, a diverse group of mostly photosynthesizing protists (unicellular eukaryotes) capable of mixotrophy, since they play a key role in primary production and formation of blooms in marine and brackish waters worldwide. In this study, ecological niches of 17 abundant bloom-forming dinoflagellate species from coastal regions of the southern Baltic Sea were identified for the first time. It was hypothesized that wider ecological niches ensure more frequent dinoflagellate blooms compared to the species with narrower niches. This hypothesis was verified using the long-term (44 years) database on phytoplankton abundance and physical-chemical characteristics of the environment. It were analyzed 4534 datasets collected from 1972 to 2016. Fourteen abiotic parameters (water temperature, salinity, Secchi depth, pH, Chl a, and concentration of basic nutrients) were considered as ecological niche dimensions. The Principal Component Analysis presented the dissolved inorganic nitrogen, total nitrogen, Chl a, and temperature as principal niche dimensions of dinoflagellates. The algal bloom criteria were refined. It was for the first time proved statistically that HAB frequency of dinoflagellate species robustly correlated with the width of their ecological niches

Planktonic Ciliates of the Neva Estuary (Baltic Sea): Community Structure and Spatial Distribution

Ciliate communities in open waters of the meso-eutrophic Neva Estuary (the Baltic Sea) were studied in summer 2010. Abundance and biomass of ciliates were surprisingly low (0.03–1.9 ind ml–1 and 0.04–2.4 × 10–3 μg C ml–1), especially in samples with high detritus content. During this study we detected four ciliate species which are new for the Baltic Sea. Mixotrophic ciliates dominated at the majority of stations (28–67% of overall ciliate numbers). Their contribution was significantly higher in the outfall area and northern part of the Neva Estuary (Resort District), where total density of ciliates was low. Medium-sized ciliates (30–60 μm) were the most diverse and abundant (average contribution 59% of total abundance). The two parts of the estuary, separated from each other by a storm-surge barrier, differed slightly in their community structure (p &lt; 0.05) but did not significantly differ in ciliate numbers and biomass values

Functional response of midsummer planktonic and benthic communities in the Neva Estuary (eastern Gulf of Finland) to anthropogenic stress

Long-term hydrobiological research has shown that the functioning of the ecosystem of the Neva Estuary, one of the largest Baltic estuaries, has changed greatly since the beginning of the 20th century. Ineffective local water management in St. Petersburg during thelast twenty years has stimulated the development of a natural "biological plug" in the salt barrier zone in the inner part ofthe estuary and has altered the ecosystem's functioning. These changes include an increase in primary production, in the primary production:organic matter decomposition ratio, and in pelagic-benthic coupling. It has also given rise to filamentous algae blooms and intensive secondary pollution in the coastal zone of the Neva Estuary. The primary production of phytoplankton in the inner part of the estuary has reached 2.3 gC m^-2, that of the filamentous algae <i>Cladophora glomerata</i> 5.5 gC m^-2 these figures are much higher than in other regions of the Gulf of Finland

Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake Ontario

1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake