Current state of bacterial community of Lake Ladoga

The data are presented on a quantitative assessment of the bacterioplankton community of Lake Ladoga and total bacterial numbers dynamic in the period from 2009 to 2019. The trophic state of the lake and water quality in different areas have been characterized by microbiological parameters. Maximum concentrations of microorganisms and highest water temperatures were commonly observed in the shallow coastal area (Volkhov Bay, up to 6.40 ×106 cells ml−1), and minimum – in the deepest part of the lake (ca. 0.45 ×106 cells cm−3). The bacterial abundances correlate with water temperatures both within each year of observations and over the whole study period. The trophic state of the lake expressed by the total bacterial numbers during summer seasons closely matches the state during the first decade of the 21st century. In the period of 2009-2019, the trophic state varied from oligo-mesotrophic in the hypolimnion of deep-water areas to mesotrophic eutrophic in the shallow southern coastal area, which corresponds to the trophic state indicated by chlorophyll-a concentrations. Within the previous decade (2000-2008), the waters of Lake Ladoga were “clean” and “especially clean”, while during the 2017-2019 period, water masses all over the lake can be identified as “especially clean”. From 2017 to 2019 the coccoid forms of bacterial cells prevailed over rod-shaped cells comprising 57.6 ±5.1% (2017), 64.4 ±4.5% (2018), 61.1 ±4.6% (2019), which imply the high quality of the waters.

MORPHOMETRIC, MERISTIC, AND GROWTH PATTERNS OF THE STROMBUS TURTURELLA FROM THE DOMPAK ISLAND COASTAL AREA, TANJUNGPINANG KEPULAUAN RIAU

Strombus turturella is a type of gastropods that live in the shallow coastal area of the Dompak Island. A research aims to understand the morphometrical, meristical characteristics and growth patterns of S. turturella from the Dompak Island was conducted in June-July 2018. The number of snail sampled was 400, with 46.98-83.07 TL mm and 13-46 grams BW. There were six morphological characteristics measured, there were total length, shell length, aperture length, shell width, shell depth and lip thickness, and there was one meristical characteristic count, namely the number of spire. Results shown that there are 5 morphometrical characteristic differences in males and females. Total length of male is longer than that of the female. While other characteristics, such as the shell length and aperture of the females were longer, the shell was wider, deeper and the lip was thicker than those of the males. The number of spire was 4-9 in males and 4-8 in females. The lenghweight relationship shown that the growth of males and females is allometric negative (b=0.503).

Seasonal shifts in the vertical distribution of fish in a shallow coastal area

Depth structures aquatic habitats, creating substantial differences in the species composition of underwater communities even at small intervals. Those communities also undergo considerable cyclic variation annually. In this study, we surveyed variation in the vertical distribution of fish in a shallow (20 m) coastal basin in the northern Baltic Sea during the ice-free period from May to October. The waters were strongly mixed throughout the season and only transient signs of stratification were observed. As production shifted towards higher trophic levels over summer, with sequential biomass peaks in zooplankton and juvenile fish, the vertical distribution of the entire fish assemblage became increasingly even. The results suggest that spatial resource partitioning can be strongly correlated with seasonal productivity cycles even in physically uniform environments with high connectivity. Further, the results stress the importance of sampling design (seasonal and vertical coverage) of fish studies in shallow coastal areas.

Distribution of phytoplankton community in Kotor Bay (south-eastern Adriatic Sea)

The goal of this paper was to explain variability of phytoplankton in a shallow coastal area in relation to physico-chemical parameters. Temporal variability and composition of phytoplankton were investigated in the Kotor Bay, a small bay located in the south-eastern part of the Adriatic Sea. Samplings were performed weekly from February 2008 to January 2009 at one station in the inner part of the Kotor Bay, at five depths (0 m, 2 m, 5 m, 10 m, 15 m). Phosphates, nitrites and nitrates ranged from values under the level of detection to the maximum values of 1.54, 1.53 and 23.91 µmol l−1, respectively. The phytoplankton biomass — represented by chlorophyll a concentration — ranged from 0.12 to 6.78 mg m−3, reaching a maximum in summer. Diatoms were present throughout the whole sampling period, reaching the highest abundance in March (3.42×105 cells l−1at surface). The peak of dinoflagellates in July (2.2×106 cells l−1 at surface) was due to a single species, Prorocentrum micans. The toxic dinoflagellate Dinophysis fortii occurred at a concentration of 2140 cells l−1 in May. The present results of phytoplankton assemblages and distribution provide valuable information for this part of the south-eastern Adriatic Sea where data is currently absent.