rss_2.0Oceanological and Hydrobiological Studies FeedSciendo RSS Feed for Oceanological and Hydrobiological Studies and Hydrobiological Studies Feed activity of bacterial extracts associated with soft coral and macroalgae from the Red Sea<abstract> <title style='display:none'>Abstract</title> <p>In marine environments where biofouling occurs and has an impact on the maritime economy and environment, compounds that inhibit the attachment, growth and survival of microorganisms in a biofilm complex as well as settlement of larvae are considered potential antifouling compounds. In this study, the extracellular metabolites from two surface-associated bacteria isolated from soft coral and macroalga were evaluated for antibiofilm and antisettlement activity. The bacteria were identified using 16S rRNA gene sequencing, and the culture supernatant extract of each strain was evaluated for antibiofilm activity. The compounds present in the extracts were analysed using GC-MS. The two bacterial strains were identified as <italic>Bacillus licheniformis</italic> MBR1 and <italic>Vibrio alginolyticus</italic> MBR4 for the isolates from soft coral and macroalgae, respectively. The extracts inhibited the growth of biofilm-forming bacteria, biofilm formation and barnacle larval settlement. The GC-MS analysis of the extract detected the presence of compounds such as tetrapentacontane, octadecanoic acid, 2,3-dihydroxypropyl ester, hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester and 17-pentatriacontene. The results of the study show that extracellular metabolites of the bacteria associated with marine organisms could be used as natural antifouling compounds to control biofouling.</p> </abstract>ARTICLEtrue record of economically important big-scale sand smelt ( Risso, 1810, Pisces: Atherinidae) with some biological parameters from Reyhanlı Dam Lake, Türkiye<abstract> <title style='display:none'>Abstract</title> <p>This paper is the first report on the occurrence of <italic>Atherina boyeri</italic> in this region. A total of 103 individuals of <italic>A. boyeri</italic> were caught with fyke-nets (mesh size: 5 mm, polyamide) in May and June 2022. The length and weight of the sampled fish ranged from 6.52 to 8.57 cm and 1.44 to 3.46 g, respectively. The exponent b of length/weight ratio was calculated as 3.091 indicating that species presented an isometric growth. The mean value of the relative condition factor K<sub>n</sub> was calculated as 1.106 ± 0.011. In conclusion, this study provides the first and valuable information about the spatial distribution of <italic>A. boyeri</italic> and the biodiversity of the new habitat of Reyhanlı Dam Lake. Within the scope of the traceability of a newly formed ecosystem, it would be beneficial to more extensively investigate this species in terms of the food web, population dynamics, etc. Therefore, more studies should be carried out to determine the aquatic biodiversity and population dynamics of the fishery resources in the lake. The results of this study should be considered by local fishery management authorities and decision-makers to ensure the sustainability of fishery resources and to implement appropriate fishery management approaches.</p> </abstract>ARTICLEtrue intensity and daily mussel consumption of Rapa whelk () in the north-western Black Sea<abstract> <title style='display:none'>Abstract</title> <p>Based on an experiment carried out in the north-western Black Sea (Snake Island), the feeding behavior of the Rapa whelk (<italic>Rapana venosa</italic> Valenciennes, 1846) was analyzed in relation to its size (N = 58; shell height: 30–90 mm). Mediterranean mussels (<italic>Mytilus galloprovincialis</italic> Lamarck, 1819) were placed in experimental cages with <italic>R. venosa</italic> to be used as food. It was found that the size of the prey was determined by the size of the predator. The mussels with a shell length of 20–40 mm were most affected by <italic>R. venosa</italic>. It was determined that the predator's contribution to the deposition of mussel shells in the bottom sediments is also associated with its size. Feeding intensity varies from 41 mg to 99 mg of the total mass of mussels per 1 g of the total mass of <italic>R. venosa</italic> per day, depending on the size of the predator. The daily consumption of mussel soft tissue varied from 0.189 g ind.<sup>−1</sup> per day<sup>−1</sup> in small <italic>R. venosa</italic> specimens to 0.917 g ind.<sup>−1</sup> per day<sup>−1</sup> in large predators. Regression equations were obtained between the length and mass of the mussels consumed (total mass, soft tissue mass and shell mass) and the shell height of the predator.</p> </abstract>ARTICLEtrue distribution and community structure of surface water mesozooplankton from the eastern Mediterranean Sea<abstract> <title style='display:none'>Abstract</title> <p>The zooplankton community structure and its relationship with environmental parameters were evaluated in the surface waters (0–50 m) of the eastern Mediterranean (the Aegean Sea's coastal waters and the Levanine Sea's coastal and offshore waters), from coastal waters to open sea waters, during the summer for two years. A total of 157 species/groups were registered in the study area. Copepods, cladocerans, doliolids, meroplankton and appendicularians represented the most important zooplankton groups. Five copepod species (<italic>Corycaeus</italic> [<italic>Onychocorycaeus</italic>] <italic>ovalis</italic>, <italic>Goniopsyllus clausi</italic>, <italic>Oncaea scottodicarloi</italic>, <italic>Sapphirina bicuspidata</italic> and <italic>Scaphocalanus curtus</italic>) have been recorded for the first time in Turkish coastal regions; three species (<italic>Centropages bradyi</italic>, <italic>Goniopsyllus clausi</italic> and <italic>Oncaea scottodicarloi</italic>) had not previously been found in the Aegean Sea; and one species (<italic>Goniopsyllus clausi</italic>) has been added for the first time to the eastern Mediterranean fauna. Moreover, <italic>Pleopis schmackeri</italic> was already found to be present in both the Aegean Sea and Mediterranean coasts of Turkey in August 2006. Dominant species varied from the coastal waters to open waters. A small number of species belonging to the coastal community (e.g. <italic>Penilia avirostris</italic>, <italic>Pseudevadne tergestina</italic>, <italic>Oithona plumifera</italic>, <italic>Paracalanus parvus</italic> and <italic>Centropages kroyeri</italic>) dominated all coastal areas. In contrast, the open water stations were characterised by the presence of typically epipelagic species of the Mediterranean Sea (e.g. <italic>Calocalanus</italic> spp., <italic>Clausocalanus furcatus</italic>, <italic>Lucicutia flavicornis</italic>, <italic>Mecynocera clausi</italic>, <italic>Farranula rostrata</italic>, <italic>Oncaea scottodicarloi</italic> and <italic>Oncaea mediterranea</italic>).</p> </abstract>ARTICLEtrue of heavy metal pollution in seawater, benthic flora and fauna and their ability to survive under stressors along the northern Red Sea, Egypt<abstract> <title style='display:none'>Abstract</title> <p>The purpose of this study was to assess the north coasts of the Egyptian Red Sea, including Ras Gharieb, Hurghada, Safaga and Qusier, by evaluating the heavy metal pollution in seawater and benthic flora and fauna in the winter and summer of 2016. The concentrations of heavy metals (Fe, Mn, Zn, Cu, Ni, Cd and Pb) were analysed with an atomic absorption spectrophotometer. The results revealed that the Fe levels in the seawater ranged from 7.86 and 27.95 μg l<sup>−1</sup>, while the Zn concentrations fell between 1.83 and 5.63 μg l<sup>−1</sup>. In contrast, the recorded values of Mn, Cu, Ni, Pb and Cd in the seawater were minimal at the study sites. Regarding the biota samples, Porifera species were more adaptable than others to an accumulation of most metals in their tissues. Furthermore, seaweeds and seagrasses demonstrated remarkable adaptation in highly polluted regions, especially those with high turbidity, landfilling, sedimentation and high eutrophication rates – much more than the benthic fauna. Our research highlights the critical need for strict regulation of metal emissions in these coastal regions.</p> </abstract>ARTICLEtrue do mussel provenance and spat size affect mussel aquaculture performance in the South-Western Mediterranean (Algeria)?<abstract> <title style='display:none'>Abstract</title> <p>The objective of this research was to study the effects of size and spat origin of farmed <italic>Mytilus galloprovinciallis</italic> in mussel longlines in the east of Bou-Ismail Bay (central coastal Algeria, south-western Mediterranean). The study was conducted from October 2017 to July 2020 in the east of Bou-Ismail Bay. The mussel spat were obtained from four origin sites (Tlemcen, Tenes, Ain Tagourait and the study site) and were seeded on three spat sizes (10–30, 30–60 and &gt;60 mm). The production performance of this species was analysed on 284 random mussel plots using average physical product (APP), gain and loss rates, condition index (CI), percentage of edibility (PE) and shell thickness index (STI). Apart from the CI and loss rate, the performance indicators showed significant differences according to spat size and source (<italic>p</italic> &lt; 0.05). Overall, the highest APP (4.3) was recorded for the small seeded mussels (10–30) mm and for those originating from Tlemcen, near finfish cages (APP = 4.14). These individuals exhibited more efficient growth and physiology for commercial size and performed better than the spat collected at the study site. The results can be considered a valid contribution to best farming practice for optimising the production of this species in Algeria. It also contributes to the development of integrated multitrophic aquaculture (IMTA) methodology, which is suitable for use in the oligotrophic Western Mediterranean.</p> </abstract>ARTICLEtrue metal accumulation in a bioindicator species, Limpet , in Yalova (İzmit Bay): Risk assessment for human health<abstract> <title style='display:none'>Abstract</title> <p>In this study, monthly heavy metal concentrations in the whole-body tissue of <italic>Patella caerulea</italic> (Mediterranean limpets), a bioindicator species living in the coastal zone of the Gulf of Izmit (Marmara Sea), were examined for the first time. The mean metal concentrations in <italic>Patella caerulea</italic> (mg kg<sup>−1</sup> dw) were 2.01–5.74 Cd, 2.45–12.90 Cu, 0.74–1.95 Pb, 21.12–109.57 Zn, 16.31–154.67 Ni, and 1120.67–3086.00 Fe. Cd levels in all months and Pb levels in October and November were found to be above the safe limits set by international organizations. The estimated daily intakes and estimated weekly intakes determined for each heavy metal were below the acceptable daily intakes and provisional tolerable weekly intakes. However, the target hazard quotient and total target hazard quotient values calculated for Cd, Ni, and Fe were found to be higher than 1. The carcinogenic risk value was also found to be high.</p> </abstract>ARTICLEtrue Ponto-Caspian and native amphipod life history in the Daugava River, Latvia<abstract> <title style='display:none'>Abstract</title> <p>Population structure, reproductive parameters and other life history traits are among the main preconditions for alien amphipods’ successful invasion. In the freshwaters of Northern Europe, i.e. Latvia, the overall life history of alien Ponto-Caspian amphipods is little known. Furthermore, the population structure and reproductivity of native <italic>Gammarus pulex</italic> have not been studied in Latvian freshwaters. The aim of the study was to describe the life history of <italic>Gammarus varsoviensis</italic>, <italic>Pontogammarus robustoides</italic> and the coexistent <italic>G. pulex</italic>. Their population structure, reproductive period and fecundity in the Daugava River were evaluated as part of this study from 2017 to 2019. The results revealed that the reproductive period of <italic>G. varsoviensis</italic> and <italic>P. robustoides</italic> lasted from four to five months, with up to three generations per year and a high proportion of juveniles. The average number of eggs for <italic>G. varsoviensis</italic> was 31 (maximum: 69) and for <italic>P. robustoides</italic> 28 (maximum: 81), with ovigerous females of both species being an average of 11.3 mm. <italic>Gammarus pulex</italic> had one generation per year with a high proportion of juveniles. The average number of eggs per brood was 27 (maximum: 41) with the average size of ovigerous females being 10.7 mm.</p> </abstract>ARTICLEtrue of cloud cover on local remote sensing – Piaśnica River case study<abstract> <title style='display:none'>Abstract</title> <p>New satellite-based techniques open up new horizons to researchers and local communities. Concurrently, however, requirements and expectations with regard to satel-lite-based remote sensing products are increasingly higher. By relying on satellite-derived information, environmental observations can cover areas of a few to several metres resolution. Here we are dealing with free-of-charge and generally available sources of satellite-based information. The Piaśnica River mouth area was selected as an observation site representing a highly dynamic morphological transect. The paper compares products of cloud cover detection, supplied with data and available in the Copernicus database for a local area in the coastal zone of the Baltic Sea. The absolute difference did not exceed 5%, which confirms a high efficiency of the solutions offered. More than 96% of the clouded area determined for the Sentinel-2/MSI (Multispectral Instrument) was correctly identified when compared with supervised observations. The rate was lower (92%) for the Sentinel-3/OLCI (Ocean and Land Colour Instrument). It was eventually concluded that, at the local level, successful observations can be conducted using the cloud cover map supplied with the satellite data. At the same time, the analyses presented do not rule out further efforts to, e.g., increase the accuracy and speed of the analyses.</p> </abstract>ARTICLEtrue efficiency of the smooth scallop in the Aegean Sea, Türkiye<abstract> <title style='display:none'>Abstract</title> <p>This study was carried out to determine the spat efficiency of the smooth scallop <italic>Flexopecten glaber</italic> (Linnaeus) in surface and bottom water at the Ozbek coast (Türkiye) of the Aegean Sea from September 2017 to August 2018. The environmental parameters (temperature, salinity, chlorophyll-<italic>a</italic>, and total particulate matter) were also monitored at two depths. The average water temperature at the surface and bottom were 19.79 ± 5.62°C and 19.73 ± 5.24°C, respectively. The lowest chlorophyll-<italic>a</italic> values were recorded in February (1.12 g l<sup>−1</sup>) and June (1.23 μg l<sup>−1</sup>) at the surface and bottom, respectively. The highest chlorophyll-<italic>a</italic> value was recorded in August at both depths. Throughout the study, the number of <italic>F. glaber</italic> on the collectors was 270.33 ± 43.54 spat m<sup>−2</sup> and 145.66 ± 18.03 spat m<sup>−2</sup> were detected on the bottom collectors. A statistically significant difference was found between the growth of the spat attached to the surface and bottom collectors (<italic>p</italic> &lt; 0.05).</p> </abstract>ARTICLEtrue of anthropogenic activities on nutrient parameters in the North Eastern Mediterranean Sea (Bay of Sığacık/Aegean Sea)<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 μ<sub>4</sub><sup>+</sup>-N l<sup>-1</sup>, 0.1 ± 0.01 μ<sub>2</sub><sup>-</sup>-N l<sup>-1</sup>, 0.8 ± 0.08 μ<sub>3</sub><sup>-</sup>-N l<sup>-1</sup>, 0.7 ± 0.08 μ<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>ARTICLEtrue and extracellular amino acids of different bloom species in the Mediterranean Sea<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>ARTICLEtrue deformities in (Teleostei: Cyprinidae) collected from the Dalaman River in southwestern Turkey<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>ARTICLEtrue record of the common sun star (L., 1767) in the Baltic Sea in over 100 years<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>ARTICLEtrue metal content in coral reef-associated fish collected from the central Red Sea, Saudi Arabia<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>ARTICLEtrue of diet quantity on growth performance of juvenile sea cucumbers<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>ARTICLEtrue of ecological risk analysis for benthic macroinvertebrates in paddy fields in the Meriç–Ergene River Basin (Turkish Thrace)<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>ARTICLEtrue of the benthic diatom flora in the coastal zone of the Gulf of Gdańsk: a case study of the Gdynia–Sopot transect<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>ARTICLEtrue of 8-hydroxy-2-deoxyguanosine activity, apoptosis, acetylcholinesterase and antioxidant enzyme activity in brain exposed to chlorpyrifos<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>ARTICLEtrue effects of different bacterial species in aquaculture: behavioral, hematological and oxidative stress responses<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>ARTICLEtrue