Volume 47 (2018): Edizione 2 (June 2018)

Yellow catfish, Pelteobagrus fulvidraco, is an important commercial freshwater species in China. Knowledge about the genetic diversity of the yellow catfish is important to support the management and conservation programs, which would subsequently support the sustainable production of this species. To investigate the genetic diversity and the structure of yellow catfish in the middle and lower reaches of the Yangtze River, 125 individuals from five lakes were genotyped using 13 microsatellite markers. Moderate genetic diversity was determined in all populations, with the observed heterozygosity (H_O) ranging from 0.42 to 0.49 and the expected heterozygosity (H_E) ranging from 0.51 to 0.61. Low to moderate genetic differentiation among the populations was revealed from pairwise F_ST values (p < 0.05), as well as from analysis of molecular variance (AMOVA). The UPGMA dendrogram and Bayesian clustering analysis indicated a correlation between genetic differences and geographic distance – four populations from the lower reaches clustered together, whereas the Poyang Lake (PY) population formed a separate cluster. The present study would be helpful in the wild stock management and artificial propagation programs for yellow catfish in the middle and lower reaches of the Yangtze River.

Ascidians are filter-feeding sac-like marine urochordates of great evolutionary, ecological and economic importance. Andaman and Nicobar Islands are one of the most important hot spots of biodiversity in India, while the ascidian diversity of this region is very scanty. Ascidians belonging to 29 species were identified at the Andaman and Nicobar Islands during the field research carried out from March 2014 to April 2015. Eight species (Didemnum granulatum, Didemnum molle, Didemnum psammatodes, Diplosoma listerianum, Lissoclinum fragile, Lissoclinum levitum, Lissoclinum patella, Trididemnum Cyclops) from the Didemnidae family were found and identified. Various diversity indices, such as the Shannon -Wiener index (H’), Margalef’s index (D), Pielou’s index (J’), K-dominance curves, Cluster Analysis and Multidimensional Scaling, were used to analyze the diversity, richness and evenness of species, and to compare the diversity between samples and their resemblance in terms of species composition. The maximum species richness was observed in Campbell Bay (2.424) and the minimum in Haddo Wharf (0.910). This finding shows the rich species diversity of ascidian fauna at Andaman and Nicobar Islands.

Monthly variations of size-fractionated chlorophyll a and phycocyanin were studied in Lake Pamvotis between August 2016 and January 2017. Sampling was conducted at two sampling sites: in the main lake (Site 1: Lake) and in an adjacent man-made water ski lake with karstic springs (Site 2: Springs). Samples were fractionated into three size classes: 0.2–2 μm (pico), 2–20 μm (nano) and 20–180 μm (micro). According to chlorophyll a values, eutrophic to hypereutrophic conditions prevail at Site 1 and oligotrophic to mesotrophic conditions – at Site 2. Similarly, Site 1 was distinguished by higher concentration of phycocyanin compared to Site 2. Fractionated chlorophyll a showed monthly variations at Site 1 with alternations in the dominance between the two larger fractions. The maximum of the 0.2–2 μm fraction was observed in October but it contributed less to the total chlorophyll a content than nano- or microphytoplankton. Its contribution was higher at Site 2, reaching occasionally ~ 40% of the bulk chlorophyll a. However, nanophytoplankton was the fraction found to respond faster when disturbances occurred. At Site 1, phycocyanin correlated well with total chlorophyll a as well as with the micro- and nanophytoplankton fractions, indicating that cyanobacteria represent an important component of the large-sized phytoplankton in Lake Pamvotis.

The Ascaridoidea are parasites with heteroxenous life cycles. The study shows that fish can be paratenic, intermediate, or final hosts for parasites, and parasitic fauna reflects the feeding behavior of the hosts. Each species of parasites has also different environmental preferences and host specificity. Parasitic nematodes of fish representing Pleuronectidae, Gadidae, Sebastidae, and Macrouridae were studied. Worms were collected separately from different infection sites: stomach, intestine, liver and body cavity. Nematodes were identified using both morphological and molecular methods (PCR-RFLP). Six nematode species were recorded: Anisakis simplex s.s., Contracaecum osculatum A, B, and C. osculatum C (s.s.), Hysterothylacium aduncum and Pseudoterranova bulbosa. Anisakis simplex s.s. was the most numerous nematode species of all catches combined. Differences in parasite species composition were related to the depth and location of sampling areas. In the fish from deep waters, the abundance of A. simplex s.s. decreased compared to fish from shallow waters and P. bulbosa was the dominant species. Ascaridoid species have specific preferences regarding the impact on various internal organs of fish, which is reflected in their abundance. The presence of Ascaridoidea in the Barents Sea is associated with the distribution of hosts and varying food preferences related to the age of fish. The abundance of parasites varied between different host species.

Eutrophication of the Baltic Sea is considered a major threat to its ecological status. We present and discuss Polish riverine flow normalized loads of total nitrogen (TN) and total phosphorus (TP) discharged into the Baltic Sea in (i)1988–2014, (ii) periods of maximum TN (1992–1994), TP (1988–1991) emission, (iii) the reference period (1997–2003) established by the Helsinki Commission (HELCOM), (iv) 2012–2014, last years of our study. Despite considerable nutrient load reductions prior to the HELCOM reference period, Poland is expected to reduce TN and TP loads by 30% and 66%, respectively. In the light of our historical and up-to-date findings defining ecological status of the Baltic Sea, we suggest that the proposed TP load reduction is overestimated and its realization may lead to (i) undesirable consequences for the Baltic ecosystem, (ii) would require a decline in TP concentrations to 0.067 mg P dm^-3 (the Vistula River) and 0.083 mg P dm^-3 (the Oder River), values reported for pre-industrial times. The current nutrient concentrations in the Vistula and Oder safely comply with the requirements of the Water Framework Directive. We also comment on the top-down and bottom-up effect resulting in quantitative and qualitative reorganization of the Baltic ecosystem, a phenomenon already observed in the Baltic Sea.

This study describes the subfossil diatom flora in the surface sediments of the Polish coastal waters in relation to human impact. The material studied consists of the uppermost parts of seven sediment cores collected from the SW Gulf of Gdańsk and eight cores from the Vistula Lagoon. Our results show the present-day ecological state of both basins just before the planned construction of a navigable channel of the Vistula Spit, which will be the next factor affecting their hydrology. In different parts of the Gulf of Gdańsk, cultural eutrophication resulted in a distinct “anthropogenic assemblage” in the surface sediments. Its structure relates directly to the distance from the mouth of the Vistula River. In the surface assemblages of the Vistula Lagoon, the number of salt-tolerant diatoms increased with the salinity of the basin. Locally, a large number of pollution-resistant taxa was also observed.

The aim of the study was to indicate the abiotic parameters of water and bottom sediments, which significantly affect the reproduction of Potamothrix hammoniensis in 9 shallow eutrophic lakes, of which 5 were dominated by macrophytes and 4 – by phytoplankton. Samples were collected once a month from January to December 2012.

The percentage of Potamothrix hammoniensis individuals with a developed reproductive system varied in individual lakes and ranged from 14 to 72%. There was no correlation between the distinguished lake types and the proportion of sexually mature individuals. The reproductive activity was not observed in summer and early autumn. Among the measured parameters, the highest values of the Pearson correlation coefficient were found between the percentage of individuals with a developed reproductive system and the conductivity (r = 0.69; p < 0.001), pH (r = 0.51; p = 0.002) and the organic matter content in the sediments (r = −0.42; p = 0.012). It is worth noting that there was no correlation between the percentage of sexually mature specimens and the water temperature (r = −0.22, p = 0.204) and the oxygen concentration (r = −0.08; p = 0.648).

The significant wave height field over the Gulf of Gdańsk in the Baltic Sea is simulated back to the late 19^th century using selected data-driven System Identification techniques (Takagi-Sugeno-Kang neuro-fuzzy system and non-linear optimization methods) and the NOAA/OAR/ESRL PSD Reanalysis 2 wind fields. Spatial variability of trends in the simulated dataset is briefly presented to show a cumulative “storminess” increase in the open, eastern part of the Gulf of Gdańsk and a decrease in the sheltered, western part of the Gulf.

Paramecium bursaria (Ciliophora) is a cosmopolitan unicellular organism that plays a significant role in aquatic ecosystems. P. bursaria contains symbiotic algae and this association is a mutual symbiosis. The aim of the present study was to determine the activity of photosystem II (PSII) in Chlorella sp. inside P. bursaria cells. Ciliates were incubated for 7 days at different temperatures from 6 to 18°C, under the circadian cycle: 12 h light/12 h dark, at light intensity of 200 μmol m^-2 s^-1 and under constant darkness conditions. The control group was kept at a temperature of 18°C under constant light conditions. Changes in PSII were monitored using different fluorescence parameters. Differences in responses between endosymbiotic algae of two P. bursaria strains – Ard7 from a warm climate and KD64 from a cold climate – were determined. The highest photosynthetic activity of P. bursaria green endosymbionts was observed at a temperature of 18°C, regardless of the light conditions. Algae from warm climate were more sensitive to cold temperature stress than algae from P. bursaria collected in cold climate.

Sigara assimilis (Fieber, 1848) is an aquatic true bug from the family Corixidae. Our paper is the first report on this species from Poland. Numerous males and females of the species were found in a hypohaline coal mine settling pond in southern Poland.