Volume 46 (2017): Issue 3 (September 2017)

An ichthyoplankton survey was conducted between March 2012 and February 2013 along the Anatolian coast of the Dardanelles Strait, with the aim of describing the species composition and temporal variation of fish eggs and larvae. For this purpose, monthly samples were collected at three sites using a WP-2 plankton net equipped with 500 µm mesh during a one-year period. Biodiversity indices were calculated to understand differences in biodiversity. A total of 50 teleost fish species belonging to 25 families and 7 orders were identified. The highest species richness of fish eggs was recorded in spring, whereas the highest species richness of fish larvae – in spring and summer. On the other hand, species richness of fish eggs and larvae were at a minimum in the fall. The most dominant species recorded in the Dardanelles were Sprattus sprattus as fish eggs and Engraulis encrasicolus as fish larvae. The relatively lower abundance of eggs and lack of earlier egg phases indicate that Engraulis encrasicolus does not spawn in the Dardanelles Strait, and the spawned eggs develop while drifting from the spawning grounds in the Marmara Sea to the sampling area.

The comparison of the latest and previous data on the structure of phytoplankton and chlorophyll a concentration in Lake Charzykowskie indicated long-term changes and fluctuations. The main objective of this study was to assess the phytoplankton communities in the lake with reference to hydrochemical conditions. Detailed hydrobiological studies were carried out in 2014-2015 to explain the improvement in the trophic status of the lake observed in 2008-2009. The research has shown that the phytoplankton community structure does not change significantly during the limnological cycle. The spring/ autumn season is characterized by the highest contribution of diatoms and cryptophytes. Massive development of dinoflagellates was observed during the summer. Relative abundance of cyanobacteria (Aphanizomenon, Dolichospermum and Microcystis) was significantly lower compared to the previous years. In August 2014, cyanobacteria accounted for 100% of the total phytoplankton at site 2. In the following year, cyanobacteria represented only 13% in the summer phytoplankton. The current research has confirmed the favorable trophic changes in the phytoplankton of the lake. Unfortunately, very poor oxygen conditions will continue to affect the trophic status of the lake through mobilization of the internal nutrient supply. The current conditions of the lake require further monitoring of changes in the ecosystem.

The thickness and duration of ice cover are strongly influenced by global warming. The aim of this study was to determine chemical (organic carbon, total nitrogen and phosphorus concentrations) and biological (nanoflagellates, ciliates, phytoplankton, rotifers, crustaceans) parameters under the ice cover in three eutrophic lakes (Masurian Lake District, Poland), differing in their morphometry and fisheries management. All the studied groups of organisms showed high variability over a short time. Taxonomic composition of planktonic communities, except for rotifers and phytoplankton, was similar in all lakes. Nanoflagellates were dominated by autotrophic forms, while ciliates were primarily composed of small oligotrichs and prostomatids. Nano-sized diatoms and mixotrophic cryptophytes were the most important components of phytoplankton and they formed an under-ice bloom in one lake only. Rotifers were mainly represented by Keratella cochlearis, Polyarthra dolichoptera and Asplanchna priodonta. Among crustaceans, copepods clearly dominated over cladocerans. Our research suggests that winter was a very dynamic period. In the under-ice conditions, pelagic organisms were strongly dependent on each other. The shallow lake and the deeper, small lake differed significantly in nutrient and chlorophyll concentrations, ciliate and phytoplankton biomass and the ratio of autotrophic to heterotrophic biomass. These results suggest that morphometric parameters may affect planktonic organisms during the ice-covered period.

The generalization and analysis of original data have shown that the nature of epiphytic algae distribution on higher aquatic plants, representing different ecological groups, is very similar in various types of numerous water bodies in the Dnieper River basin. Their species richness and values of quantitative indices were mostly higher on submerged plants compared to plants of other ecological groups. The number of epiphytic algae species was 1.1-1.7 times higher on submerged plants compared to that on half-submerged plants and 1.6-3.1 times higher compared to plants with floating leaves. The taxonomic structure and species composition of epiphyton were very similar on half-submerged and submerged plants and moderately similar on plants with floating leaves compared to macrophytes of other ecological groups. It is emphasized that the specificity of epiphytic algae distribution on macrophytes of various ecological groups should be taken into account when performing monitoring and assessment of the ecological status of water bodies by the bioindication method.

The paper presents the chronology of the Holocene evolution of the Baltic Sea based on the optically stimulated luminescence (OSL) and radiocarbon dating methods applied to a core taken from the Arkona Basin. The dating results were supplemented by grain size and geochemical analysis. The obtained results of OSL and radiocarbon dating enabled the construction of an age-depth model and confirmed the continuous sedimentation since 9900 cal yrs BP. One of the most interesting findings of this study is a clear relationship between the rate of sedimentation and fluctuations in the energy of depositional environment. The analyzed sediment core revealed two sections of different accumulation rates. The bottom section was deposited until 2700 cal yrs BP when the Ancylus Lake and the Littorina Sea were present, characterized by the accumulation rate estimated at around 0.46 mm year^-1 and the dynamic sedimentation environment confirmed by grain size parameters. The accumulation rate at the top section deposited during the Post-Littorina Sea stage was estimated at around 1 mm year^-1. This stage, characterized by more stable deposition and lower-energy environment conditions, was confirmed by small grain size, symmetric skewness and increasing content of organic matter.

We collected flying fish (Exocoetus volitans) from the South China Sea to determine whether fish scale isotope values correlate with those from muscle, and discuss relevant eco-environmental implications. A significant positive correlation was determined between fish scales and muscle δ¹³C and δ¹⁵N, rendering a fish scale an alternative to muscle tissue for stable isotope analysis. However, muscle and scale isotopic offsets should be fully considered when using δ¹³C and δ¹⁵N to analyze the actual trophic level of fish and their food source. The average offsets of δ¹³C and δ¹⁵N between muscles and scales are -2.1 ± 0.5‰ and 2.3 ± 0.6‰, respectively, though these values vary slightly with fish mass. Weak correlations were found between δ¹³C and δ¹⁵N, both in the flying fish muscle and scales, suggesting that other factors are influencing δ¹³C and δ¹⁵N. Fish δ¹⁵N also correlates with the size of individuals, while δ¹³C reflects the marine habitat. Based on our data, it appears that more eco-environmental processes can be revealed from modern or ancient flying fish scales.

This is the first comprehensive study covering the parasite fauna of smelt, Osmerus eperlanus, from five estuary sites of the southern Baltic Sea in a stretch of almost 500 km. We examined 432 smelt from: the Neman River mouth, the Vistula River mouth, Pomeranian Bay, the Oder River, and Lake Dąbie and recovered 13 species/higher-rank taxa of parasites: Diplostomum spp., Posthodiplostomum cuticola, Eubothrium crassum, Proteocephalus longicolis, Cystidicola farionis, Hysterothylacium aduncum, Corynosoma semerme, Pomphorhynchus laevis, Unionidae gen sp., Ergasilus sieboldi, Argulus foliaceus, Piscicola geometra, and Saprolegniaceae gen sp. Basic infection parameters such as prevalence, intensity of infection, mean intensity of infection, and the dominance index were determined. The findings of the presently reported study constitute a number of new faunistic records. There were two new host records (Posthodiplostomum cuticola and Saprolegniaceae gen sp.), five new host records for Poland (Diplostomum spp., Pomphorhynchus laevis, Piscicola geometra, Argulus foliaceus, and Unionidae gen sp.), and two new host records for Lithuania (Argulus foliaceus and Unionidae gen sp.). We carefully analyzed the relevant information from more than 100 publications on smelt parasites to compare the data with our own findings.

In order to understand the variability of diatoms in coastal lakes and its relationship to salinity, the authors have conducted a two-year study at Lake Resko Przymorskie (the Southern Baltic coast), which has a salinity between 1.9-4.8 PSU. Redundancy analysis (RDA) was used to describe the relationship between the species composition and selected variables. Four of the 10 measured variables of surface water chemistry (Cl- and PO₄^3- concentrations, temperature, and pH) significantly explained 23% of the variation in the diatom species composition.

We found 82 taxa of diatoms (mostly tychoplanktonic) and determined the optimum and tolerance levels of salinity for predominant taxa (49 species with minimum 2% abundance). The optimum chloride concentration for the predominant diatoms ranged from 1471 to 2961 mg Cl^- l^-1.

The most abundant brackish water species was Pseudostaurosiropsis geocollegarum. Brackish-freshwater diatoms were represented by Cyclotella atomus, Cyclotella meneghiniana, Diatoma tenuis and Staurosira subsalina. The most abundant fresh-brackish water diatoms were Amphora pediculus, Fragilaria sopotensis, Hippodonta hungarica, Pseudostaurosira brevistriata and Staurosira construens. Freshwater taxa accounted for as little as 1% of the population. This study provides new data on the ecology of coastal lakes and the possibility of using diatom-based transfer functions in the reconstruction of past environmental changes.

The present study deals with macrozoobenthic species on soft substrates in İğneada (Turkish coast of the Black Sea). Benthic samples were collected seasonally at three stations between 2012 and 2013. A total of 155 species belonging to seven taxa (Turbellaria, Nemertea, Nematoda, Oligochaeta, Polychaeta, Crustacea, Phoronida, Mollusca, Hemichordata) were identified. Of these, four species are new records for the Black Sea fauna, 15 species are new to the Turkish coast of the Black Sea; and two species are new to the Turkish Seas. Polychaeta was the most representative taxon in the study area – it was represented by 58 species (39% of the total number of species). In terms of the number of individuals, Mollusca were the dominant taxon in all seasons (82% of the total number of individuals). The most dominant species were Bittium reticulatum and Caecum trachea and the most frequent species were Micronephtys stammeri, B. reticulatum and Chamelea gallina.

Cocconeis subantarctica sp. nov., a small monoraphid marine diatom, previously described as C. scutellum cf. var. parva Grunow, is reported from the Kerguelen Archipelago. Based on the careful re-examination of the material using SEM (scanning electron microscopy), both valves and the cingulum were described, which enabled a better classification of this small Subantarctic taxon. The shape of the frustule is widely rounded to subdiscoid, with uniseriate and radiate striae on both valves. The SV (sternum valve) areolae have rota-like hymenate pore occlusions, with larger marginal areolae separated by a hyaline rim. The RV (raphe valve) areolae are more complex than those of the SV, with several reniform concentric hymenate occlusions. This taxon has no real stauros, only one virga, which is larger on one side of each valve. The species is not a member of the Cocconeis scutellum ‘complex’, but is closely related to C. stauroneiformis despite several morphological differences.