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/6093a2f6a8c0980825868ca7/cover-image.jpg?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20220814T161406Z&X-Amz-SignedHeaders=host&X-Amz-Expires=604800&X-Amz-Credential=AKIA6AP2G7AKP25APDM2%2F20220814%2Feu-central-1%2Fs3%2Faws4_request&X-Amz-Signature=2654ba21d83f470f83d67af986a31faac195fcaf7b361eb07cebee6f23d00dba200300Effects of anthropogenic activities on nutrient parameters in the North Eastern Mediterranean Sea (Bay of Sığacık/Aegean Sea)https://sciendo.com/article/10.26881/oandhs-2022.2.07<abstract> <title style='display:none'>Abstract</title> <p>This study aims to examine the physicochemical parameters of seawater (temperature, pH, salinity, dissolved oxygen, suspended particulate matter, ammonium-nitrogen, nitrite-nitrogen, nitrate-nitrogen, and phosphate-phosphorus, burnable organic matter in the sediment), and possible effects of pollution in Sığacık Bay where different anthropogenic activities are carried out. Samples of surface seawater (0 m), bottom seawater (2 m), and sediment were collected monthly from four sampling sites between September 2013 and September 2014. Annual mean nutrient values were determined as 1.6 ± 0.14 μg.at.NH<sub>4</sub><sup>+</sup>-N l<sup>-1</sup>, 0.1 ± 0.01 μg.at.NO<sub>2</sub><sup>-</sup>-N l<sup>-1</sup>, 0.8 ± 0.08 μg.at.NO<sub>3</sub><sup>-</sup>-N l<sup>-1</sup>, 0.7 ± 0.08 μg.at.PO<sub>4</sub><sup>3-</sup>-P l<sup>-1</sup>, SPM 21.4 ± 0.33 mg l<sup>-1</sup>. The BOM content in the sediment was 5.6 ± 0.39%. As a result of the study, it was determined that Sığacık Bay was polluted by anthropogenic point and non-point source pollution. According to the water quality criteria, the bay was found to be in the group of polluted seawater in terms of phosphate phosphorus.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Intercellular and extracellular amino acids of different bloom species in the Mediterranean Seahttps://sciendo.com/article/10.26881/oandhs-2022.2.06<abstract> <title style='display:none'>Abstract</title> <p>The presented laboratory experiment was designed to characterize the quantity and compositional variation of algal extracellular amino acids (AAs) that may represent an alternative nutrient source in a natural environment. To resemble algal bloom scenarios, analyses were conducted in mono- and/or co-cultures of the bloom-forming species <italic>Skeletonema costatum, Scrippsiella trochoidea, Ulva fasciata</italic>, and <italic>Corallina officinalis</italic> during their active growth phase. The study revealed that <italic>S. costatum</italic> exhibited higher production of the dominant AAs than <italic>S. trochoidea</italic>. Alanine, lysine, and threonine acids are the dominant amino acids in <italic>S. costatum</italic> and <italic>S. trochoidea</italic> filtrates, which may play a role in mucus formation during mucosal phytoplankton blooms with negative ecological effects. On the other hand, aspartic, glutamine, alanine, and leucine acids are the dominant amino acids in macroalgae. In co-culture experiments, <italic>U. fasciata</italic> shows strong and rapid allelopathic activity against these two potentially harmful species. The AA production offers an advantage to species with the capacity to absorb them to form blooms. Thus, anthropogenic inorganic nutrient inputs may be less important for the development of algal blooms in coastal waters. A major difference that distinguishes this work from others is the use of specific multi-taxa cultures of phytoplankton and macroalgae. The study represents a new research effort in Alexandria waters.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Skeletal deformities in (Teleostei: Cyprinidae) collected from the Dalaman River in southwestern Turkeyhttps://sciendo.com/article/10.26881/oandhs-2022.2.08<abstract> <title style='display:none'>Abstract</title> <p>In this study, skeletal anomalies such as vertebral centra deformation, lordosis (ventral curvature), and consecutive repetition of lordosis and kyphosis were examined in specimens of <italic>Barbus xanthos</italic> (Güçlü, Kalaycı, Küçük &amp; Turan, 2020) collected from the Dalaman River, southwestern Turkey. Abnormalities of the vertebral column were observed in both thoracic and caudal vertebrae. Cases of lordosis and consecutive repetition of lordosis and kyphosis showed varying degrees of severity. Specimens with consecutive repetition of lordosis showed the most acute deformities among the cases studied, as they revealed complicated incidences of skeletal anomalies. None of the cases were fatal as they occurred in adult individuals. This study discusses the possible causes of such deformities and the usefulness of this type of study in environmental monitoring.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00First record of the common sun star (L., 1767) in the Baltic Sea in over 100 yearshttps://sciendo.com/article/10.26881/oandhs-2022.2.02<abstract> <title style='display:none'>Abstract</title> <p>The rare in the German North and Baltic Sea waters and strictly protected sea star <italic>Crossaster papposus</italic> was found in 2019 and 2021 during monitoring activities in a marine protected area. This unique observation was achieved by using towed camera platform imagery along a transect in the Fehmarn Belt, which allows monitoring of a much larger area of the seafloor compared to traditional invasive grab and dredge sampling. The last time <italic>C. papposus</italic> was documented in this area was in 1871, indicating the rarity of this species in the Baltic Sea. Possible explanations for such rare records of the occurrence of this presumably native species in the study region are briefly discussed, including uncommon survival due to salinity conditions caused by prior inflows of saline water from the North Sea.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Heavy metal content in coral reef-associated fish collected from the central Red Sea, Saudi Arabiahttps://sciendo.com/article/10.26881/oandhs-2022.2.03<abstract> <title style='display:none'>Abstract</title> <p>The concentration of heavy metals in marine fish is important for assessing the health risks associated with fish consumption. In this study, the concentration of metals such as copper, lead and manganese were analyzed in the muscle tissue of five coral reef-associated fish species collected from the central Red Sea, Saudi Arabia. The maximum copper content of 0.183 μg g<sup>-1</sup> (ww) was detected in fish samples. Fish samples also showed maximum lead and manganese values of 0.030 and 0.064 μg g<sup>-1</sup> (ww), respectively. The metal concentration in fish tissue samples did not vary significantly between the fish species. In conclusion, the results obtained indicate that the content of heavy metals in the coral reef-associated fishes is below the values determined by various agencies for seafood safety.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Effects of diet quantity on growth performance of juvenile sea cucumbers https://sciendo.com/article/10.26881/oandhs-2022.2.04<abstract> <title style='display:none'>Abstract</title> <p>Sea cucumbers are in high demand in the world market due to their nutritional and medicinal values. In this study, the growth performance of juvenile sea cucumbers <italic>Holothuria scabra</italic> fed with different proportions of two feeds was analyzed. Commercially available sea cucumber feed (feed-A) and formulated feed (feed-B) were used for the experiments. Animals fed with 2% feed-A showed a negative growth rate. Maximum growth was observed in animals fed with 8% feed-A and feed-B. While feed-A treated groups showed significant variation (<italic>P</italic> &lt; 0.05) in growth performance between different percentages of diets, feed-B treated animals showed no such variation. Feed-B treated animals showed higher growth rates compared to feed-A treated sea cucumbers. Water quality parameters and anoxic conditions of the soil in culture tanks did not change due to the higher percentage of feeds. In conclusion, this study showed that diet percentage is an important factor for the optimum growth of sea cucumbers.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Evaluation of ecological risk analysis for benthic macroinvertebrates in paddy fields in the Meriç–Ergene River Basin (Turkish Thrace)https://sciendo.com/article/10.26881/oandhs-2022.2.09<abstract> <title style='display:none'>Abstract</title> <p>Benthic macroinvertebrates are very important components of aquatic environments, and monitoring their population dynamics helps us understand the effects of environmental factors on ecosystems. This study aimed to determine the dynamics of benthic macroinvertebrate fauna in paddy fields in the Meriç–Ergene River Basin (Turkish Thrace region) by investigating some physicochemical environmental parameters that may affect its distribution. For this purpose, water and sediment samples were collected from paddy fields in the study area during the cultivation season, including spring, summer and autumn of 2016, taking into account the water resources that supply the rice fields (artesian water, the Meriç River, the Ergene River and Meriç–Ergene mixed water). A total of 47 taxa (on average 8953 individuals per m<sup>2</sup>) were identified at the study sites. Water samples were analyzed to determine water temperature, pH, conductivity, salinity, total dissolved solids, calcium, magnesium, total hardness, nitrite nitrogen, nitrate nitrogen, phosphate, sulfate, dissolved oxygen and pesticides, and sediment samples were analyzed to determine the content of some heavy metals, including Cd, Ni, Cu, and Mn. The biological risk index (mERM-Q) and the potential ecological risk index (RI) were applied to the data and a hypothetical ecological risk analysis was conducted using our data and data available in the literature to assess the ecological risk profile of the ecosystem based on benthic macroinvertebrates. To this end, environmental factors were grouped based on the literature as heavy metals (S1), nutrients (S2), other physicochemical parameters (S3) and pesticides (S4), while organisms were grouped as Oligochaeta, Chironomidae, Insecta and others based on the dynamics of benthic macroinvertebrates to assess pressure factors. As a result, pesticides (S4) were found to exert the strongest ecological pressure on benthic macroinvertebrate fauna in paddy fields in the Meriç–Ergene River Basin.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Biodiversity of the benthic diatom flora in the coastal zone of the Gulf of Gdańsk: a case study of the Gdynia–Sopot transecthttps://sciendo.com/article/10.26881/oandhs-2022.2.10<abstract> <title style='display:none'>Abstract</title> <p>The objective of this study is to determine microhabitat preferences of benthic species occurring in epilithic (living on stones), epipsammic (growing on sand), epipelic (growing on mud) and epiphytic (living on seagrass) assemblages of the shallows of the Gulf of Gdańsk (southern Baltic Sea). The study material was collected from 19 sites along the Gdynia–Sopot coastal zone, including the Port of Gdynia. Most of the identified diatom taxa were observed in two or three microhabitats. However, diatom species living in only one type of microhabitat and those occurring in all analyzed microhabitats were also recorded. Autecological preferences of the identified diatoms indicate organic pollution of the coastal zone of Gdynia and Sopot. However, a higher frequency of α-mesosaprobionts and polysaprobionts indicates an increase in organic pollution in the Port of Gdynia and Marina Sopot, which is associated with intense port activity and large tourist traffic.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Assessment of 8-hydroxy-2-deoxyguanosine activity, apoptosis, acetylcholinesterase and antioxidant enzyme activity in brain exposed to chlorpyrifoshttps://sciendo.com/article/10.26881/oandhs-2022.2.05<abstract> <title style='display:none'>Abstract</title> <p>In this study, neurotoxic responses to exposure to chlorpyrifos (CPF) at different doses (55 and 110 μg l<sup>-1</sup>) and at different time intervals (24 and 96 h) were investigated in Siraz fish (<italic>Capoeta umbla</italic>) using 8-hydroxy 2-deoxyguanosine (8-OHdG) activity, caspase-3, acetylcholinesterase (AChE) and oxidative stress parameters [malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR)]. In this study, the LC<sub>50</sub> value of CPF was determined for the first time for <italic>C. umbla</italic> and calculated as 440 μg l<sup>-1</sup>. In this study, 12.5% (55 μg l<sup>-1</sup>) and 25% (110 μg l<sup>-1</sup>) of the LC<sub>50</sub> value were used. The obtained data indicate a significant increase in the MDA level and inhibition of antioxidant enzymes in the brain (<italic>p</italic> &lt; 0.05). Considering DNA damage and the apoptotic process, no significant changes were found in 8-OHdG and caspase-3 activity at both doses exposed for 24 h, but a significant increase was detected in both markers at 96 hours compared to the control group (<italic>p</italic> &lt; 0.05). In the case of AChE activity, which is one of the neurotoxic markers in the brain, while inhibition was determined only at the high concentration (110 μg l<sup>-1</sup>) at the end of 24 hours, a decrease in enzyme activity was observed at the end of 96 hours in both concentration groups. In the light of all these results, we can say that CPF showed inhibitory effects on enzyme activity and inducing effects on MDA, caspase-3 and 8-OHdG levels. Based on these results, it can be concluded that CPF contributes to oxidative stress in fish and may have neurotoxic effects.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Pre-probiotic effects of different bacterial species in aquaculture: behavioral, hematological and oxidative stress responseshttps://sciendo.com/article/10.26881/oandhs-2022.2.01<abstract> <title style='display:none'>Abstract</title> <p>There is very limited aquaculture research on candidate probiotics and their effects on fish physiology. In this study, acute applications of four different molecularly identified bacterial species – <italic>Brevibacillus brevis</italic> FD-1 (A), <italic>Pseudomonas fluorescens</italic> FDG-37 (B), <italic>Bacillus sphaericus</italic> FD-48 (C), and <italic>B. amyloliquefaciens</italic> TV-17C (D), with potential in aquaculture, were tested in rainbow trout (<italic>Oncorhynchus mykiss</italic>) under static conditions. Physiological changes in blood tissue [hematological indices: erythrocyte count (RBC), leukocyte count (WBC), hemoglobin (Hb), hematocrit (Hct), platelet count (PLT), mean cell hemoglobin concentration (MCHC), mean cell hemoglobin (MCH), and mean cell volume (MCV)], oxidative stress responses in liver and gill tissues [malondialdehyde (MDA) level, antioxidant enzyme activities: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GP<sub>X</sub>), glutathione reductase (GR), glutathione-S-transferase (GST), glucose-6-phosphate dehydrogenase (G6PD)] and acetylcholinesterase (AChE) activity in brain tissue (as neurotoxic biomarker) were investigated. Additionally, behavioral differences were recorded by measuring swimming performance to support neurotoxic findings in all treatment groups. The LC<sub>50</sub>24 value of FDG-37 strain was determined through analysis as 1.0 × 10<sup>8</sup> CFU ml<sup>-1</sup>. Inhibition of enzyme activity, increase in the MDA level, as well as significant differences in hematological indices and swimming performance were determined in rainbow trout treated with B compared to control and other bacterial groups in gills. The potential for using group FD-48 and TV-17C bacterial strains as probiotics in aquaculture is more pertinent when considering the research findings and water quality parameters.</p> </abstract>ARTICLE2022-07-07T00:00:00.000+00:00Effects 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+00:00en-us-1