rss_2.0Oceanological and Hydrobiological Studies FeedSciendo RSS Feed for Oceanological and Hydrobiological Studieshttps://sciendo.com/journal/OANDHShttps://www.sciendo.comOceanological and Hydrobiological Studies 's Coverhttps://sciendo-parsed-data-feed.s3.eu-central-1.amazonaws.com/61a9a0c332fa2f51bbc1e76f/cover-image.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20220627T214413Z&X-Amz-SignedHeaders=host&X-Amz-Expires=604800&X-Amz-Credential=AKIA6AP2G7AKP25APDM2%2F20220627%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Signature=003af64aa30fc88808221e6abac77cb4e57e70bc415bc86d07aec9d699bf0596200300Effects of morphometric and biochemical parameters on collagen and pepsin-solubilized collagen yields of (Gmelin, 1790) and () (Delle Chiaje, 1823)https://sciendo.com/article/10.26881/oahs.2022.1.09<abstract><title style='display:none'>Abstract</title><p>Due to their unique biochemical composition, sea cucumbers are highly prized marine echinoderm species. One of their most important properties is that they contain a high amount of collagen in their body wall. In this study, the relationship between collagen and pepsin-solubilized collagen yields from <italic>Holothuria tubulosa</italic> and <italic>Holothuria poli</italic> and morphometric and biochemical parameters were investigated.</p><p>Collagen yields were in the range of 10.63–16.04% for <italic>H. tubulosa</italic> and 7.12–13.10% for <italic>H. poli</italic>. It was determined that they may be related to length, body wall weight, and biochemical composition at different length frequencies. Moreover, maturity may have a direct effect on the yield, as mature specimens were found to have lower content of collagen, whereas immature small specimens contained a higher percentage of collagen. It was found that with increasing pepsin concentration, the PSC yield increased to 1.83–1.89% in <italic>H. tubulosa</italic> and <italic>H. poli</italic>, respectively. It was determined that collagen from smaller individuals, which contained more moisture and ash, was likely more susceptible to pepsin hydrolyzation.</p><p>This is the first published study demonstrating that collagen yield of sea cucumbers can vary with length, weight, maturity, and biochemical composition, in addition to species-specific differences.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Parasites of the invasive Chinese sleeper (Actinopterygii: Odontobutidae) in the region of the first introduction of the Carpathian populationhttps://sciendo.com/article/10.26881/oahs.2022.1.01<abstract><title style='display:none'>Abstract</title><p>Parasites of the invasive Chinese sleeper (<italic>Perccottus glenii</italic>) were studied in five different localities at the site of the first introduction of the Carpathian population of this fish. We recorded eight taxa of parasites in Lviv water bodies. The monogenean <italic>Gyrodactylus perccotti</italic> and the cestode <italic>Nippoteania perccotti</italic> were recorded in all five lakes studied. These parasites represent Far East species introduced together with their host. Also the copepod <italic>Neoergasilus japonicus</italic> is a Far East parasite introduced to Europe with its aquaculture vector. Differences between the surveyed bodies of water were mainly related to their local seasonal conditions and watershed characteristics. The current data confirm the presence of co-introduced populations of <italic>G. perccotti</italic> and <italic>N. perccotti</italic>, which probably affects the future invasiveness of their host. Due to low acquisition of local parasites, we cannot confirm any significant effect of invasive fish on local parasite assemblages in this region. However, the presence of the non-indigenous copepod, <italic>N. japonicus</italic>, requires additional attention in the future.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Assessment of inorganic nitrogen and phosphorus compounds removal efficiency from different types of wastewater using microalgae cultureshttps://sciendo.com/article/10.26881/oahs.2022.1.05<abstract><title style='display:none'>Abstract</title><p>The efficiency of ammonium nitrogen (N-NH<sub>4</sub><sup>+</sup>) and phosphate (P-PO<sub>4</sub><sup>3−</sup>) removal from wastewater with different loads of these nutrients was evaluated using <italic>Chlamydomonas reinhardtii</italic> (Chlorophyta) and <italic>Oscillatoria neglecta</italic> (Cyanophyta/Cyanoprokaryota). In addition, functional characteristics of the microalgae under the studied conditions were determined. It was demonstrated that <italic>Ch. reinhardtii</italic> is resistant to a wide range of concentrations of inorganic nitrogen and phosphorus compounds. Microalgae actively participate in the removal of N-NH<sub>4</sub><sup>+</sup> from wastewater (removal efficiency of 49–63%, depending on the initial concentration). At the same time, <italic>Ch. reinhardtii</italic> showed low levels of P-PO<sub>4</sub><sup>3−</sup> removal (7–18%) from the aquatic environment. <italic>O. neglecta</italic>, unlike <italic>Ch. reinhardtii</italic>, is sensitive to excessively high concentrations of N-NH<sub>4</sub><sup>+</sup> (90–140 mg l<sup>−1</sup>) and P-PO<sub>4</sub><sup>3−</sup> (26–90 mg l<sup>−1</sup>). However, it is characterized by high removal efficiency for both forms of nitrogen (60–61%) and phosphorus (43–55%) at their initial concentrations of 30–50 mg l<sup>−1</sup> and 7–14 mg l<sup>−1</sup>, respectively. Therefore, <italic>O. neglecta</italic> is best suited for use in wastewater post-treatment.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Molecular identification and distribution of insect larvae in the Lower Danube Riverhttps://sciendo.com/article/10.26881/oahs.2022.1.07<abstract><title style='display:none'>Abstract</title><p>As a major component of freshwater ecosystems, insect species play an important role in nutrient cycling and are often used as bioindicators of water pollution. Although extensive studies have characterized insects from freshwater habitats, little is known about the distribution of these species along the Lower Sector of the Danube River. Therefore, this survey conducted in the Danube section within the Romanian territory aimed to identify insect larvae belonging to seven different species of Odonata, Trichoptera, Ephemeroptera, Lepidoptera and Megaloptera by DNA barcoding and to investigate their distribution, density and frequency. A total of 41 quantitative macrozoobenthic samples were collected during two consecutive years (2019 and 2020). Species showed large differences in the distribution and density along different sections, and an overall tendency to populate downstream areas, except for <italic>Sialis morio</italic>. On the other hand, only <italic>Hydropsyche bulgaromanorum</italic>, <italic>Triaenodes bicolor</italic> and <italic>S. morio</italic> larvae were identified in the upstream section (Sulina branch). These data provide baseline information on the larger range of some of the most common aquatic insects in the Romanian Danube section in relation to several environmental parameters based on the first molecular identification of these species using COI gene sequencing.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Life history of wahoo, , in the Tropical Eastern Atlantic Ocean – the importance of applying a suite of methods for fisheries assessment in data-limited situationshttps://sciendo.com/article/10.26881/oahs.2022.1.10<abstract><title style='display:none'>Abstract</title><p>Unassessed fisheries, mostly non-targeted fisheries, are now particularly predominant in many commercial fisheries and are critical to food security in developing countries. These fisheries typically lack reliable data essential for assessing their stocks, leaving them susceptible to overfishing and declining yield over time. This study proposes a framework for determining the life history and management of such fisheries. Data on the length composition and reproduction of wahoo <italic>Acanthocybium solandri</italic>, a common bycatch species in commercial fisheries, were obtained from observers aboard Chinese longline vessels in the Eastern Atlantic between 2010 and 2020 and were used as a case study. A comprehensive methodological approach was applied using data on this species to estimate its life history parameters, to evaluate biological reference points, and to provide proxies for the stock status. The final main growth parameters obtained were: L<sub>inf</sub> = 161.21 cm FL (157.34–194.68), <italic>K</italic> = 0.47/year (0.14–0.65); estimated size at first maturity was 89.6 cm FL. As assessed by the set of methods applied, the wahoo stock state was healthy in the Tropical Eastern Atlantic Ocean. This study advises against using a single approach to determining life history parameters in data-limited fisheries, as this may affect reference points and thus management recommendations. This study provides a route whereby many easy-to-apply methods can be used to understand the status of multiple stocks in poorly managed fisheries, and thus provide management plans.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Sustainability or fun? Recreational angling in Marine Protected Areashttps://sciendo.com/article/10.26881/oahs.2022.1.04<abstract><title style='display:none'>Abstract</title><p>Gökova Bay MPAs (southern Aegean Sea, Turkey) include six different no-take zones (NTZs: Akyaka, Çamlı, Akbük, Boncuk-Karaca, İngiliz Limanı, Bördübet), in four of which shore angling is permitted (Akyaka, Çamlı, Akbük, Boncuk-Karaca). This study determined the total catch and size of fish caught in the Akyaka MPA during recreational fishing. In total, fish representing 22 species belonging to 10 families were caught and most of them were smaller than their length at first maturity. The projection showed that the total catch weight reached significant values for recreational angling in the Akyaka MPA. The results of this study indicate that recreational angling may pose a threat to both MPAs and no-take zones, causing them to deviate from their primary conservation goal due to the harvesting of juveniles by recreational anglers.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Prospects and opportunities for mussel farming in the southern Baltic Sea (the Gulf of Gdańsk)https://sciendo.com/article/10.26881/oahs.2022.1.06<abstract><title style='display:none'>Abstract</title><p>In the Baltic Sea, where osmotic stress limits the growth of marine organisms, mariculture is driven primarily by the need to improve the status of the environment. To this end, several mussel farms have been attempted in selected areas, except the southern Baltic. The pilot culture of <italic>Mytilus trossulus</italic> was carried out with the use of a modified long-line system in the Gulf of Gdańsk in 2009–2012, providing the first evaluation of the mussel farming potential in this area. The growth rate of mussels (3.0–6.7 mm year<sup>−1</sup>) in the gulf was in the low range, but the mean wet biomass gain (1.50 kg m<sup>−1</sup> normalized culture rope) was among the highest in the Baltic. After a two-year growth period, one tonne of mussels fixed in their soft tissues from 93 to 98 kg N t<sup>−1</sup> and 11 kg P t<sup>−1</sup>. The cost-benefit analysis revealed a negative budget balance of production for human consumption, with a total income covering only 12.0% of the cumulative costs. Mussel farming in the gulf can therefore only be justified to improve the environmental quality if additional funding mechanisms are put in place to support farming activity.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Diversity and succession of microbial communities on typical microplastics in Xincun Bay, a long-term mariculture tropical lagoonhttps://sciendo.com/article/10.26881/oahs.2022.1.02<abstract><title style='display:none'>Abstract</title><p>In this study, three polymer types of microplastics (MPs), polyethylene (PE), polystyrene (PS) and polypropylene (PP), were exposed for 60 days in Xincun Bay (Hainan, China), a long-term mariculture tropical lagoon. High-throughput sequencing and scanning electron microscopy (SEM) were used to investigate the succession of microbial community structure and function on MPs after 10, 30, and 60 days of exposure, respectively. The results showed that diversity indices for bacteria from MPs were higher than those for bacteria from seawater. Significant differences were observed in community structure and metabolic function between MPs and seawater. The microbial network structure on MPs was more complex and dispersed than that in seawater. No significant differences in bacterial community structure and metabolic function were observed among different types of MPs. The biofilm on PS was the thickest, and the network structure on PP was the most complex one. With increasing exposure time, the biofilm attached to the surface of MPs became thicker and microbial composition showed some differences. The analysis of potential degradation bacteria and pathogens with abundance above 0.01% showed that the abundance of several potential plastic biodegraders on MPs was higher than that in seawater, while no potential pathogen was found enriched on MPs.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Effects of fishing and environmental parameters on the commercial bony fish assemblage in the southern Caspian Seahttps://sciendo.com/article/10.26881/oahs.2022.1.08<abstract><title style='display:none'>Abstract</title><p>Since the 1990s, anthropogenic activities have been the major direct or indirect threats to the structural and functional organization of the unique ecosystem of the Caspian Sea (CS). This study attempts to investigate the relationships between fish community structure and environmental parameters and to analyze the Abundance Biomass Comparison (ABC) in the CS. The input data, including catch data by species and environmental parameters, were collected from 1996 to 2017. Of the 13 bony fish species identified, only two species <italic>Rutilus kutum</italic> and <italic>Chelon aurata</italic> accounted for 47.14% and 62.65%, and 40.80% and 29.34% of CPUE and NPUE, respectively. DisTLM revealed that five environmental variables showed a significant linear relationship with the NPUE resemblance matrix. Based on the AIC criteria, the combination of year, precipitation, SST_Apr, SSL, SST, GTA, Iranian rivers, and Volga discharges explain 80.3% of the total variability. Based on the ABC curves and W statistics, it was concluded that the fish assemblage was environmentally stressed from 1996 to 2003. The Shannon diversity index (H′) showed a decreasing trend, suggesting that fish species have been exposed to increasing stress over the past 22 years. Considering the current environmental conditions (downward trend in SSL river discharge and increase in SST) and anthropogenic activities, it appears that the downward trend will continue in the future.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00 gen. nov. & comb. nov. (Bacillariophyta) – a pantropical marine member of Cocconeidaceaehttps://sciendo.com/article/10.26881/oahs.2022.1.03<abstract><title style='display:none'>Abstract</title><p><italic>Cocconeis dapalistriata</italic>, first described as a member of the genus <italic>Cocconeis</italic>, is re-examined due to its unique ultrastructure. Both valvocopulae of this taxon show significant differences compared to those found in the genus <italic>Cocconeis</italic>. They are expanded and show some similarities with those found in <italic>Amphicocconeis</italic>. On the other hand, terminal parts of the raphe valve (RV) in <italic>C. dapalistriata</italic> are simple and the raphe valve (RV) striae are composed of small round areolae with a hymenate occlusion with radial slits, similar to those observed in <italic>Cocconeis</italic>. <italic>Campyloneis</italic> and <italic>Xenococconeis</italic> also have expanded valvocopulae but with numerous morphological differences compared to those found in <italic>C. dapalistriata</italic>. Furthermore, the areolae of the sternum valve (SV) in <italic>C. dapalistriata</italic> are occluded by a concave velum with no apparent internal slits, and externally ornamented with irregular silica crystals. <italic>Upsilococconeis</italic> Riaux-Gobin, Witkowski &amp; Risjani gen. nov. is proposed to accommodate the latter taxon. First described from the Western Indian Ocean (Mascarenes), it was subsequently listed from the Western Pacific Ocean (Guam), the South Pacific Ocean (French Polynesia and New Caledonia) and from the Eastern Indian Ocean (Indonesia), and thus may qualify as pantropical.</p></abstract>ARTICLE2022-03-31T00:00:00.000+00:00Determination of functional structure of soft-bottom marine macrobenthic communities of the Samsun Shelf Area using biological traits analysishttps://sciendo.com/article/10.2478/oandhs-2021-0040<abstract> <title style='display:none'>Abstract</title> <p>Biological Traits Analysis (BTA) was used to investigate the functional structure of marine macrobenthic communities along the Samsun Shelf Area (SSA). Benthic samples were collected seasonally from five different locations and at four different depths using a Van Veen grab sampler. Macrofaunal communities distributed in the SSA were assessed using 10 biological traits to identify characteristic traits for each depth and location. It was found that variability of benthic ecosystem functions in the SSA was driven by biological traits such as maximum size, living habit, sediment position, feeding mode and type of reproductive behavior. Bivalves, polychaetes and crustaceans of small to medium size, biodepositing, burying themselves in the sediment (burrowers) and feeding in suspension were relatively more abundant at depths of 0–60 m. However, the biomass of <italic>Amphiura</italic>, <italic>Abra</italic>, <italic>Papillicardium</italic> and some polychaetes characterized by medium to large sizes, diffusive mixing, free living and feeding on deposit and subsurface deposit showed higher values at depths below 60 m. In general, it is concluded that the functional structure of the benthic infauna in the SSA has adapted to physical disturbance, and communities distributed in this area consist mainly of taxa resistant to mechanical pressure.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Otolith phenotypic analysis for the endemic Anatolian fish species, Caucasian bleak Steindachner, 1897 (Teleostei, Leuciscidae), from Selevir Reservoir, Akarçay Basin, Turkeyhttps://sciendo.com/article/10.2478/oandhs-2021-0037<abstract> <title style='display:none'>Abstract</title> <p>Otolith phenotypic variability was analyzed in the Caucasian bleak (<italic>Alburnus escherichii</italic>) from the Selevir Reservoir in Turkey. Utricular (lapillus) and lagenar (asteriscus) otoliths were removed, while distinguishing between left and right otoliths. All otoliths were photographed on the distal (for asterisci) and dorsal surface (for lapilli) using a Leica DF295 digital camera. Otolith morphometrics were measured to the nearest 0.001 mm using Leica Imaging Software. Linear and nonlinear (power) models were applied to determine the relationships between otolith measurements and total length of fish individuals. Two length classes (Class I: 6.7–10.9 cm <italic>L<sub>t</sub></italic>; Class II: 11.0–15.0 cm <italic>L<sub>t</sub></italic>) were established to analyze the shape of otoliths. The Form Factor, Circularity, Roundness, Rectangularity, Aspect Ratio and Ellipticity were used to analyze the shape of otoliths. A standardized model was used to remove the effect of size on otolith measurements. Multivariate analysis was performed to detect differences in otolith shape variation. The results of discriminant function analysis showed that 79.9% of <italic>A. escherichii</italic> specimens were correctly classified by length classes. In this study, intraspecific variation of asteriscus and lapillus otoliths in <italic>A. escherichii</italic> is reported for the first time. The results of this study provide the first comprehensive data on otolith shape analysis and the relationship between otolith morphometrics and total length in the Caucasian bleak.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Tunisian inland water microflora as a source of phycobiliproteins and biological activity with beneficial effects on human healthhttps://sciendo.com/article/10.2478/oandhs-2021-0033<abstract> <title style='display:none'>Abstract</title> <p>Ten monoclonal microalgal cultures were obtained from several Tunisian inland water bodies, and their dichloromethane and methanolic extracts were screened for antibacterial, antileishmanial, and antioxidant properties, as well as phycobiliprotein production capacity. <italic>Cylindrospermopsis raciborskii</italic> has been shown to synthesize high levels of phycocyanin and may be an effective alternative source to other sources used for commercial production of phycocyanin. <italic>Chroococcus</italic> sp. and <italic>Leptolyngbya</italic> sp1. exhibited the strongest radical scavenging activity against DPPH (IC<sub>50</sub> = 212.15 and 263.91 μg ml<sup>−1</sup>, respectively), indicating their promising potential for use as new effective and non-toxic antioxidants. Furthermore, <italic>Dunaliella</italic> sp. showed an interesting antileishmanial activity against the pathogens <italic>Leishmania infantum</italic> and <italic>Leishmania major</italic> (IC<sub>50</sub> = 151 and 284 μg ml<sup>−1</sup>, respectively), thus representing a good candidate for use against cutaneous and visceral leishmaniasis in Tunisia, a country endemic to these diseases where thousands of new cases are registered every year. These results suggest that the strains of microalgae featured in this work have the potential to serve as natural alternative, safe and sustainable sources of high value-added products that could be used to improve the final biomass value.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Effects of seasonal changes and depth on growth parameters of the Mediterranean mussel () on a shipwreck in the Eastern Mediterranean Seahttps://sciendo.com/article/10.2478/oandhs-2021-0038<abstract> <title style='display:none'>Abstract</title> <p>The study was conducted between July 2018 and May 2020 to compare seasonal changes in growth parameters of the Mediterranean mussel (<italic>Mytilus galloprovincialis</italic>) at different depths in two different areas of the Northeastern Mediterranean Sea (Aegean Sea). In a preliminary study, mussels were placed in cages at different depths of an artificial reef (AR – shipwreck) and natural reef (NR). Temperature, salinity, pH, and dissolved oxygen were determined seasonally at both sites at a depth of 37 m (deepwater) and 25 m (midwater). Linear increases in length and width of mussels at the AR site were recorded, while no consistent changes were observed for mussels at the NR. There was negative correlation between the specific growth rate (SGR) and salinity (r<sup>2</sup> = 0.5098) and temperature (r<sup>2</sup> = 0.1470) at the AR site. Negative correlations were also recorded between pH and the commercial condition index (<italic>CCI</italic>) at both the AR (r<sup>2</sup> = 0.3869) and NR (r<sup>2</sup> = 0.3600) sites. Our findings show that depth had a significant effect (<italic>p</italic> &lt; 0.05) on the <italic>CCI</italic> of mussels at the NR site, while its effect was insignificant for this index at the AR site (<italic>p</italic> &gt; 0.05). This study indicates that natural reefs provide more suitable conditions for the growth of Mediterranean mussels than shipwrecks used as artificial reefs.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Biodiversity of freshwater macroinvertebrates on Gökçeada Island (North Aegean Sea, Turkey)https://sciendo.com/article/10.2478/oandhs-2021-0036<abstract> <title style='display:none'>Abstract</title> <p>Island ecosystems have attracted the attention of scientists since the early days of science because of their formation and biodiversity. Despite their abundant freshwater resources, data on freshwater diversity of Gökçeada are incomplete, especially for macroinvertebrates. This study was conducted in a wide range of freshwater ecosystems on Gökçeada between May 2016 and September 2018. Sampling of macroinvertebrates was performed using a hand net from 34 pre-selected sampling sites on the island. A total of 78 aquatic macroinvertebrate taxa were found, 46 of which are new records for the island. The most common species during the study were <italic>Gammarus komareki</italic> and <italic>Bythinella gokceadaensis</italic> with a frequency of 25.93%, followed by <italic>Tubifex tubifex</italic>, <italic>Gammarus</italic> sp. and <italic>Caenis</italic> sp. with a frequency of 22.22%. Endemic and invasive species on the island were assessed according to their presence and frequency values. Based on the results of the current study and previous data, it can be concluded that Gökçeada is characterized by a remarkable species diversity compared to aquatic macroinvertebrates on other Aegean islands.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Empirical approach to risk management strategies of Mediterranean mussel farmers in Greecehttps://sciendo.com/article/10.2478/oandhs-2021-0039<abstract> <title style='display:none'>Abstract</title> <p>Risk perception and risk responses of Greek mussel farmers are important for understanding their risk behavior and the likely success of different risk mitigation strategies. This allows policy makers and actuarial companies to decide what risk management products to offer to address specific types of risks.</p> <p>Results from an empirical survey showed that ex-farm prices and health/disability status of farmers are perceived as the most important sources of risk.</p> <p>Risk management decisions were strongly influenced by the attitudes of mussel farmers rather than their socioeconomic status or perception of risk sources.</p> <p>Financial reserves and an alternative source of stable income are both preferred by mussel farmers as risk management strategies, while optimizing farm management to produce at the lowest possible cost is commonly practiced to eliminate losses. Farmers recommend that for certain types of risks that lead to total losses, e.g. anoxia, tsunamis, harmful algal blooms (HABs), insurance contracts should be provided by the public sector, as in similar situations in agriculture. For other needs, customized insurance contracts should be provided by the actuarial market.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Distribution of oil, grease and polycyclic aromatic hydrocarbons in coastal water and sediments of Suez Bayhttps://sciendo.com/article/10.2478/oandhs-2021-0032<abstract> <title style='display:none'>Abstract</title> <p>The permanganate index (PI), oil and grease (O&amp;G), and 17 polycyclic aromatic hydrocarbons (PAHs) were analyzed in surface sediment and water samples collected at 13 sites along the western coast of Suez Bay (SB). PI and O&amp;G in the SB coastal seawater ranged from 9.6 mg O<sub>2</sub> l<sup>−1</sup> and 17.0 mg l<sup>−1</sup> to 16.0 mg O<sub>2</sub> l<sup>−1</sup> and 37.0 mg l<sup>−1</sup>, respectively. The level of polycyclic aromatic hydrocarbons (PAH) in water and sediment in the SB offshore area was determined by gas chromatography/flame ionization detection. The concentration ranged from 0.574 to 16873.2 ng g<sup>−1</sup> in the sediment and 0.502 to 43.540 ng l<sup>−1</sup> in water. The collected data were compared with values reported in the literature. The possible source and origin of pollution was also assessed based on the determined relative PAH levels at the study sites, the ratio of low molecular mass PAHs (LPAHs) to high molecular mass PAHs (HPAHs), and molecular indices of samples.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Analysis of heavy metal contamination in surface sediments of Iskenderun Bay, Turkeyhttps://sciendo.com/article/10.2478/oandhs-2021-0035<abstract> <title style='display:none'>Abstract</title> <p>The ecological risk resulting from the accumulation of some heavy metals in the sediments of Iskenderun Bay was assessed using the following measures: enrichment and contamination factor, pollution load index (<italic>PLI</italic>), and potential ecological risk index (<italic>RI</italic>). The concentrations of the studied heavy metals were in the following order: Fe &gt; Ni &gt; Mn &gt; Cr &gt; Zn &gt; Cu &gt; As &gt; Pb &gt; Cd &gt; Hg. Ni and As had the highest <italic>EF</italic> values. This situation is most likely due to the presence of iron, pesticide, and fertilizer plants in the region. According to the United States Environmental Protection Agency, Ni, As, Mn, and Cr may have harmful effects on faunal communities in sediments. According to the <italic>RI</italic>, Site 4 was more contaminated and toxic than the other seven study sites, with “moderate” ecological risk. Pearson’s correlation coefficient was determined by multivariate methods – cluster and principal component analysis. As can be inferred from the <italic>RI</italic> values, the potential toxic effect of As and Ni in the sediments is moderate.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Effect of water quality on the spatial distribution of charophytes in the Peshawar Valley, Khyber Pakhtunkhwa, Pakistanhttps://sciendo.com/article/10.2478/oandhs-2021-0031<abstract> <title style='display:none'>Abstract</title> <p>The presented research was conducted in 2018–2019 in the Peshawar Valley, Pakistan, to study for the first time the effect of water quality on the spatial distribution of charophytes. A total of six taxa of charophytes were found at 41 sites in the Peshawar Valley along the banks of seven rivers, 16 streams and two wetlands: <italic>Chara braunii</italic> C.C.Gmelin, <italic>C. connivens</italic> Salzmann ex A. Braun, <italic>C. contraria</italic> A. Braun ex Kützing, <italic>C. globularis</italic> Thuiller, <italic>C. vulgaris</italic> Linnaeus, and <italic>Nitellopsis obtusa</italic> (Desvaux) J. Groves. <italic>Chara vulgaris</italic> was the most abundant species, followed by <italic>C. globularis</italic>, and <italic>C. contraria</italic>. Water pH, electrical conductivity (EC), total dissolved solids (TDS), salinity and dissolved oxygen (DO) were within the permissible limits for Pakistan, while water temperature, oxidation reduction potential (ORP) and resistivity showed deviations. Canonical Correspondence Analysis (CCA) revealed that DO affected <italic>Chara vulgaris,</italic> pH and resistivity affected <italic>C. braunii, C. connivens</italic> and <italic>C. globularis</italic>, temperature and ORP affected <italic>C. contraria</italic> and <italic>Nitellopsis obtusa.</italic> Furthermore, CCA showed that TDS, EC, and salinity had no effect on the spatial distribution of <italic>Chara contraria</italic>, <italic>C. vulgaris</italic> and <italic>Nitellopsis obtusa</italic>. <italic>Chara contraria</italic> and <italic>Nitellopsis obtusa</italic> should be protected under VU (Vulnerable) status (IUCN) along with their habitats.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00Growth pattern, mortality and reproductive biology of common sole, (Linneaus, 1758), in the Sea of Marmara, Turkeyhttps://sciendo.com/article/10.2478/oandhs-2021-0034<abstract> <title style='display:none'>Abstract</title> <p>The study deals with the growth pattern, mortality, and reproduction of common sole, <italic>Solea solea</italic> (Linneaus, 1758), from the Sea of Marmara (Turkey). A total of 580 fish specimens were sampled monthly from October 2017 to September 2018. The total length of all sampled individuals ranged from 11.1 to 29.5 cm, corresponding to ages from 1 to 3 years. The length–weight relationship was expressed as W = 0.022 TL<sup>2.6838</sup>, where the slope indicated negative allometric growth. Growth parameters were <italic>L</italic><sub>∞</sub> = 33.7 cm, <italic>k</italic> = 0.48, and <italic>t</italic><sub>0</sub> = −0.18 for all samples. A seasonally oscillating growth model, indicating the amplitude of oscillations, revealed an important seasonal growth pattern. Total, natural, and fishing mortality rates were calculated as 1.42, 0.47, and 1.01, respectively. The exploitation ratio (E = 0.68) indicates that the fishing pressure on the common sole in the Sea of Marmara was high. The sex ratio (♀/♂) was 1.18. The gonadosomatic index (GSI) for females showed that two main spawning seasons were observed: one in spring (May) and one in autumn (September–October). Sizes at the onset of sexual maturity were estimated for both females and males at 21.6 and 18.6 cm, respectively.</p> </abstract>ARTICLE2021-12-03T00:00:00.000+00:00en-us-1