Southeastern Black Sea Research Articles

Occurrence of microplastics in the gastrointestinal tracts of four most consumed fish species in Giresun, the Southeastern Black Sea.

Microplastic studies investigating concentrations in water are numerous, but the majority of microplastics settle and are retained in sediment, and higher concentrations are regularly reported in sediments. Thus, MPs accumulation may be more threatening to benthic fish living in sediments than to pelagic fish. The presence, abundance and diversity of microplastics were investigated by collecting samples from two pelagic, European anchovy, and horse mackerel and two benthic fish species, red mullet, and whiting that are popularly consumed in Giresun province of Türkiye, located on the southern coast of the Black Sea. Visual classification and chemical compositions of microplastics was performed using a light microscope and ATR-FTIR spectrophotometry, consecutively. The overall incidence and mean microplastics abundance in sampled fishes were 17 and 1.7 ± 0.18 MP fish-1, respectively. MPs were within the range of 0.026-5mm in size. In most of the cases, the MP was black in color with 41%. With the rates of 56%, polypropylene was the predominant polymer type. The most dominant MP type was identified as fiber followed by fragments and pellets. The relationship between MP amounts in fish and Fulton condition factor was not strong enough to establish a cause-effect relationship.

Water Quality Assessment with Artificial Neural Network Models: Performance Comparison Between SMN, MLP and PS-ANN Methodologies

AbstractIdentifying and measuring potential sources of pollution is essential for water management and pollution control. Using a range of artificial intelligence models to analyze water quality (WQ) is one of the most effective techniques for estimating water quality index (WQI). In this context, machine learning–based models are introduced to predict the WQ factors of Southeastern Black Sea Basin. The data comprising monthly samples of different WQ factors were collected for 12 months at eight locations of the Türkiye region in Southeastern Black Sea. The traditional evaluation with WQI of surface water was calculated as average (i.e. good WQ). Single multiplicative neuron (SMN) model, multilayer perceptron (MLP) and pi-sigma artificial neural networks (PS-ANNs) were used to predict WQI, and the accuracy of the proposed algorithms were compared. SMN model and PS-ANNs were used for WQ prediction modeling for the first time in the literature. According to the results obtained from the proposed ANN models, it was found to provide a highly reliable modeling approach that allows capturing the nonlinear structure of complex time series and thus to generate more accurate predictions. The results of the analyses demonstrate the applicability of the proposed pi-sigma model instead of using other computational methods to predict WQ both in particular and other surface water resources in general.

Nutrient Dynamics in the South-Eastern Black Sea

Güney Doğu Karadeniz (Artvin-Giresun) kıyıları boyunca Kasım 2014-Ağustos 2016 tarihleri arasında mevsimsel olarak yürütülen bu çalışmada besim tuzu konsantrasyonlarının zamansal ve alansal değişimleri araştırılmıştır. Çalışma kapsamında 12 farklı istasyonda yüzeyden itibaren 10 m aralıklarla 40 m derinliğe kadar mevsimsel örneklemeler yapılmıştır. Çalışma bölgesinde sonbahar ve kış mevsiminde besin tuzu konsantrasyonları yüksek olup ilkbahar ve yaz mevsiminde fitoplanktonik aktiviteye bağlı olarak düşüş göstermiştir. Örnekleme istasyonlarında SiO2 (0,01-13,625 µM) en yüksek konsantrasyonda okunan besin elementi olup, bunu NO2+NO3 (0,001-3,346 µM) takip etmiştir. Bölgede o-PO4 konsantrasyonları (0,001-0,932 µM) genel anlamda düşük bulunmuştur. Çalışma bölgesinde yüzey suyu besin tuzu konsantrasyonları alansal ve zamansal önemli değişimler göstermiş ve kıyısal bölgenin daha zengin olduğu ve açığa gidildikçe konsantrasyonlarda önemli oranda azalmalar tespit edilmiştir. Çalışmanın ikinci yılında silikat ve fosfat konsantrasyonları 2 kata yakın bir oranda artış eğilimi sergilerken benzer bir artış eğilimi nitrit+nitrat için sadece ilkbahar mevsiminde gözlenmiştir. Bu çalışma, bölgede besin tuzu dinamiğinin biyolojik aktiviteye bağlı mevsimsel ölçekte önemli değişimler gösterdiğini gösterirken bölgenin sürekli olarak izlenmesi gerekliliğini de ortaya koymaktadır.

СОТРУДНИЧЕСТВО РОССИЙСКОЙ ФЕДЕРАЦИИ И РЕСПУБЛИКИ АБХАЗИЯ В СФЕРЕ РЫБНОГО ХОЗЯЙСТВА: ИТОГИ И ПЕРСПЕКТИВЫ

Background. The Republic of Abkhazia has a high natural and climatic potential for the development of fisheries and aquaculture, which creates a reliable basis for its cooperation with the Russian Federation in the field of fisheries. Relevance. The analysis of the efforts of these two countries in the field of fisheries is relevant for the further advancement of their cooperation and can facilitate the sustainable development of fisheries and aquaculture, as well as rational and economically efficient use of aquatic resources in the Southeastern Black Sea. The aim of this work is to give an overview of the dynamics of the fisheries activities conducted by the Republic of Abkhazia over the past decade and to present the results of its international cooperation with the Russian Federation undertaken within the scope of the Intergovernmental Russian-Abkhazian Fisheries Commission in 2011-2024. Methods. The analysis of the developmental indices of the fisheries of the Republic of Abkhazia and the provisions of the sessions of the Russian-Abkhazian Fisheries Commission in the context of implementation of its decisions has been conducted. Results. The achievements in the main avenues of scientific, technological, educational, and economic cooperation between the Russian Federation and the Republic of Abkhazia in the field of fisheries are shown. Eight sessions of the Commission have been conducted, under the auspices of which the scientific and technological cooperation between fisheries organizations of Russia and Abkhazia in the area of multidisciplinary ecological and fisheries research has been envisioned and implemented, annual catches of anchovy during its wintering in the waters of the Republic of Abkhazia have been coordinated, operating conditions of the Russian fishing vessels in the Abkhazian sea waters have been established, and the Fishing Regulations for the waters of the Republic of Abkhazia have been developed in compliance with the provisions and articles of the Russian Fishing Regulations for the Azov and Black Sea Fishery Basin. Conclusion. Cooperation between the Russian Federation and the Republic of Abkhazia in the field of fisheries has a significant potential for deepening and development.

Spatio-temporal Distribution and Population Dynamics of the Red Mullet Mullus barbatus Linnaeus, 1758 from the South-east Black Sea

A total of 2930 Mullus barbatus individuals collected from the Southeastern Black Sea coast between March 2017 and April 2018 were investigated regarding growth, mortality rates and the distribution determined by depth and season. M. barbatus is abundant along of 30-45 m depth in winter. Total length-weight relationship was determined as W=0.005L3.2344. Von Bertalanffy growth parameters for all individuals were calculated as L∞=28.19 cm, K=0.16 years-1, t0=-0.144 years. The maximum age was 5 years. The total length at 50% maturity was estimated as 11.63 cm in males and 11.68 cm in females. Exponential coefficients of natural mortality, total mortality, and fishing mortality rate of red mullet are estimated as 0.33 year-1, 1.001 year-1 and 0.67 year-1, respectively. The exploitation rate of population was calculated as 0.66 year-1. The fact that exploitation rate is above 0.5 may reflect a high fishing pressure on stock.

First record of Sebastes schlegelii Hilgendorf, 1880 along the Turkish Black Sea coast – new addition to the alien species inventory

Sebastes schlegelii is a typical bottom dwelling boreal species, whose native distribution range includes Japan, Korean peninsula and China. This northwest Pacific originated species has recently been recorded from the Crimean and Caucasian coast (northern Black Sea), whose introduction was assumed to be either by balast waters or the acclimatization of Crassostrea gigas (Pacific oyster). On 16 August 2023, a single S. schlegelii specimen with 20.6 cm standard length and 282.1 g in weight was captured off Ünye, Ordu coast (southeastern Black Sea), which was previously an unreported fish from the Turkish marine waters. Detailed morphometric and meristic characteristics are presented in the paper, and species identification was further confirmed by genetic analysis. Available information reveals this alien species to be fished regularly, although in small quantities, indicating a presumably established population in the region. The species should be treated as a potentially invasive fish, since it may negatively influence to the local biodiversity through interspecific competition. Close monitoring of its existing population is strongly suggested.

Monitoring Sediment Transport in Certain Harbor Launches in the Southeastern Black Sea

The problem of shoaling on coastal structures is the result of an event that occurs as part of the natural cycle. In cases where shoaling cannot be detected or prevented, various economic and operational problems may arise and may cause disruptions. In this study, the complex coastal dynamic impact of shoaling on three sequential fishery coastal structures located within the borders of Rize province in the Eastern Black Sea region of Türkiye was examined in terms of bathymetric changes and sediment transport under the influence of the incident wave climate. The effects of these structures on each other were also investigated. With this aim, bathymetric measurements were carried out to examine the impact of waves on seabed erosion and deposition. A serious shoaling problem was identified at one of the harbor launches under investigation, where approximately 13,200 m3 of deposition occurs annually in a relatively small harbor launch area. Such physical problems are thought to be the result of shoaling, the selection of sites that are not viable for fishery-related coastal structures, or the wrong positioning of the breakwater.

Comparison of Publicly Available Bathymetric Data with Real Measurements in the Southeastern Black Sea

Being able to access accurate and reliable depth information has uncountable benefits for not only fields of oceanography, geophysics, geology, natural resources but also navigation & logistics. There is an ever-increasing demand for high-resolution bathymetric data for those fields since only a small portion of the world seas and oceans have been explored, observed, and charted so far. There are some sources which provide publicly available global bathymetric data to its stakeholders and users such as widely used European Marine Observation and Data Network (EMODnet) and General Bathymetric Chart of the Oceans (GEBCO). In general, it is challenging for researchers to select the best fit for their studies among available datasets, due to the fact that their sole reliability is not well-assessed. The purpose of our study, thus, is to compare those publicly available bathymetric data with field measurements obtained from the surveys carried out by the Office of Navigation, Hydrography and Oceanography for an area of interest in the southeastern Black Sea comprising various characteristics as to the bottom topography (i.e. homogeneous elevation, steep slope, mild slope, etc.). Validation is conducted focusing on these distinct features by means of visual assessment and quantitative comparison. Results reveal that, even though there is an overall agreement, local discrepancies are also present. Nonetheless, GEBCO and EMODnet datasets are proved to be great assets for any hydrospatial application that does not necessarily require high spatial resolution.

First approximation of the growth and the spawning period of Symphodus ocellatus (Linnaeus, 1758) (Pisces: Labridae) in the southeastern Black Sea

The aim of this study was to provide a first approximation of the growth, reproduction, and length–weight relationships of Symphodus ocellatus in the southeastern Black Sea, Turkey. A total of 320 specimens (273 males, 47 females) were collected between June 2015 and May 2016, and their biological parameters were estimated for each sex and both sexes combined. Total length ranged from 6.90 to 13.70 cm and the parameters (a, b) in the power length–weight relationships were a = 0.065 and b = 2.38 for males and a = 0.102 and b = 2.20 for females. Age was successfully estimated by commonly accepted procedures for otolith analysis. The von Bertalanffy growth parameters from the otolith age estimation were L∞ = 12.66 cm, k = 0.764, and t0 = –1.151 (0–3 years) for males, and L∞ = 14.15 cm, k = 0.764, and t0 = –0.188 (1–3 years) for females. The monthly gonadosomatic index values reflected a spawning period between April and July, with a spawning peak in May–June. The present study provides the first estimate of the growth and reproduction of S. ocellatus in the southeastern Black Sea of Turkey and compares the results with those from other areas.

Length–weight relationship and seasonal variations in diet composition of whiting (Merlangius merlangus) in the South-eastern Black Sea

ABSTRACT The sex ratio, length–weight relationship (LWR) and diets based on stomach contents of whiting (Merlangius merlangus) were investigated in the south-eastern Black Sea, Turkey. A total of 3507 females (7.5–24.0 cm), 1602 males (9.4–20.0 cm), and 78 unidentified sex (5.5–16.5 cm) whiting were caught during monthly sampling from February to December 2017. The sex ratio was dominated by females, and their ratio (♀:♂, 1:0.46) significantly deviated from 1:1. The LWR indicated a negative allometric growth for males, while females had a positive allometric growth pattern. The stomach content analysis based on the relative importance index (IRI%) indicated exclusively piscivorous diets dominant by Sprattus sprattus and Engraulis encrasicolus made up more than 91 IRI% of the total diets of M. merlangus. The modified Costello-Amundsen’s graphical analyses evinced the specialized feeding strategy of M. merlangus throughout this study. The contribution of these two preys to the diets of M. merlangus showed considerable seasonal variations that were totally dependent on their abundance. Sprattus sprattus contributed to more than 98% of the total diets during June, July and August, while in the following months, E. encrasicolus appeared to take its position. Based on fish size, a general trend of a rise in prey diversity was found with increasing fish size. Also, the contribution of S. sprattus tended to decrease with increasing predator size, which is replaced by a rise in E. encrasicolus contribution. Hence, larger M. merlangus predominantly fed on E. encrasicolus while smaller size predators preferred to feed on S. sprattus.

Genetic Identification of Ichthyoplankton in the Black Sea and Their Abundance and Community Assemblages

Accurate identification of fish species during the planktonic stages is vital for detecting spawning, foraging, and growth sites of fish species to provide data for stock assessment, environmental impact assessment, and ecological monitoring. In this study, seasonal ichthyoplankton abundance, community composition, and main possible environmental drivers that influence their community composition were investigated in the Southeastern Black Sea. Ichthyoplankton samples were seasonally collected for a year from four stations, two coastal and two offshore sites. DNA barcoding method was applied to identify ichthyoplankton specimens. Of 33 ichthyoplankton taxa identified using DNA barcoding, 31 taxa were identified at species level and 2 taxa were identified at genus level due to unavailability of reference sequences from the Black Sea in public databases. Engraulis encrasicolus, Sprattus sprattus, Mullus barbatus, and Trachurus mediterraneus were identified as the most abundant species. Engraulis encrasicolus alone accounted for nearly 91.5% of the total catch. Seasonality had a strong influence on the ichthyoplankton assemblages. The highest ichthyoplankton abundance was found in summer, followed by winter, autumn, and spring. While 30 fish taxa were identified in summer, 10 taxa were identified in spring, 3 taxa were identified in both autumn and winter. Ichthyoplankton communities were dominated by E. encrasicolus, M. barbatus, and T. mediterraneus specimens in summer, S. sprattus, and M. merlangus specimens in winter, S. sprattus and G. mediterraneus specimens in autumn, Alosa immaculata and Merlangius merlangus in spring. The ichthyoplankton abundance and richness was generally higher in coastal stations in each season. Engraulis encrasicolus, S. sprattus, M. merlangus, P. incognitus were the only species that detected in more than 4 hauls. On the other hand, M. batrachocephalus, P. flesus, S. abester, T. draco, U. cirrosa, and C. lucerna were only detected in a single haul. Overall, the dominant environmental variable affecting abundance of ichthyoplankton was temperature. The relationship between community composition and environmental variable based on nMDS analysis indicated that ichthyoplankton assemblage structure is also influenced by salinity, dissolved oxygen, chlorophyll-a, NO2, and NO3.

An Evaluation of the Success and Failure of Traps Designed for Exotic Sea Snail (Rapana venosa) Fishing Located on the South-Eastern Black Sea Coast

Abstract Research trials were carried out in the Samsun shelf region, where snail fishing is most common, in summer and autumn. The design of the net in the trap trials was inspired by the model used in South Korea. In the trials, the traps were kept in the sea for 24, 48, and 72 hours. According to the findings, an average of 0.31, 0.13, and 0.10 kg/day/basket were caught in the summer period, and an average of 0.15, 0.06, and 0.04 kg/day/basket in the fall for all three holding periods, respectively. In terms of catch per unit effort (CPUE) compared to the traditional beam trawler, economically satisfactory results could not be obtained.

From source to sink: A comparative study of streamside and beach litter in the Black Sea

The increasing amount of marine litter pollution and its impact on the marine environment raises global concern. This study aims to reveal the effect of streams on marine litter density and composition. A total of ten stations on the southeastern Black Sea and six stations on the Manahoz stream were seasonally surveyed. The litter density ranged between 0.838 ± 0.33 and 4.01 ± 0.55 items/m2 in the beach stations, and 0.93 ± 0.27 2.40 ± 2.18 items/m2 in the streamside stations. No significant difference was determined among the seasons for both beach and streamside (Kruskal-Wallis test, p > 0.05). On the other hand, the litter density was also similar in beach and streamside stations in the same season. The litter composition consisted of > 75% plastic. Principal component analysis and PERMANOVA determined no significant difference in litter composition among beach and streamside stations. The litter items mostly consisted of single-use items. Among them, plastic beverage containers were the most abundant litter subcategory during the study (ranging between 18.79% and 34.50%). The subcategory composition exhibited a significant difference among beach and streamside stations (ANOSIM, p < 0.05), which was mainly explained by plastic pieces, beverage containers, and foams according to SIMPER analysis. Personal protection equipment that was not reported before the COVID-19 pandemic emerged. The results of our study can be used for marine litter modeling studies and legislation for restriction or ban of most abundant single-use litter items.

A holistic approach to the eco-geochemical risk assessment of trace elements in the estuarine sediments of the Southeastern Black Sea

The estuarine sediments were sampled seasonally along the southeast coast of the Black Sea, to assess the concentrations, sources, distributions, and possible ecological risks of trace elements (TEs). The mean concentrations of TEs (mg/kg) were ranked as Fe (56,659.83) > Al (39,758.00) > Mn (1168.53) > Zn (155.03) > Cr (120.75) > Pb (93.71) > Cu (82.66) > Ni (44.93) > Co (17.98) > As (13.66) > Cd (0.99) > Hg (0.18), respectively. The stations S4 and S6 showed “very high contamination” for Pb, “significantly enrichment” for Pb and Cd, “high ecological risk” for Cd, and “heavily polluted” for Pb and Cd according to the results of CF, EF, Eri, Igeo, respectively. The rest of the stations were in the low or moderate contamination through the all seasons as assessed by different eco-geochemical risk assessment indices. The integrated risk evaluation indices indicated no contamination in stations S3 and S5.

Protracted dynamicity of microplastics in the coastal sediment of the Southeast Black Sea

This study provided the first evaluation of microplastic abundance, features, risk assessment, and decade-changing status in sediment along the southeastern Black Sea coast. Sediment samples were collected from thirteen stations in the Southeast Black Sea in 2012 and 2022. >70 % of the detected microplastics had a length of up to 2.5 mm and consisted of fragments and fibers in shape. The average microplastic abundance in the sediment samples was 108 MP/kg. The composition in the sediment (particles/kg) was dominated by polyethylene (PE) (44.9 %), polyethylene terephthalate (PET) (27.2 %), and polypropylene PP (15.2 %). Remarkable results for contamination factors, polymeric risk assessment and contamination risk indices. The sharp rise in MPS highlighted the heavily populated stations and stream discharge locations. The data shed light on anthropogenic and basal microplastic pollution in the Southeast Black Sea, assisting in developing effective policies for preserving and managing the Black Sea environment.

Spatiotemporal PAH levels in surface water of the Southeastern Black Sea; baseline study from the Giresun shores

Samples of surface water were collected seasonally along the 121 km long Giresun coastline to comparatively evaluate the source, distribution, and ecological risk of 16 polycyclic aromatic hydrocarbons (PAHs). The total PAHs levels, varied between 47.42 and 576.69 ng L−1 with the mean of 161.5 ng L−1, were consistent with seawater studies worldwide. Diagnosis rates evinced that PAHs in seawater along the Giresun coastline are primarily sourced from biomass, coal and petroleum combustion and petroleum at lesser extent. The three-ring PAHs (40.2 %) was proportionally high, followed by 2-ring PAHs (26.5 %). The toxicity equivalent quotient (TEQ) and risk quotients (RQ) were employed to assess ecological risk posed by PAHs in Giresun coastal seawater. As a result, the ecological risk in all seasons was at moderate to high risk level, except for autumn, which shows low to moderate risk according to TEQ. RQ values of ∑PAHs displayed low to moderate ecological risk.

Biological parameters of grey wrasse Symphodus cinereus (Bonnaterre, 1788) (Pisces: Labridae) along the coasts of Rize in the south-eastern Black Sea

Abstract The present study was designed to investigate the age distribution and growth properties of Symphodus cinereus in the south-eastern Black Sea. Data on the growth and age of S. cinereus were obtained by investigating sagittal otoliths. A total of 384 specimens (220 female, 164 male) were collected between June 2015 and May 2016 in the south-eastern Black Sea. Total lengths of male specimens ranged from 10–16.4 cm, whereas they ranged from 8.2–15.8 cm for females. The von Bertalanffy growth curve was used to describe length at age and considerable differences were seen between females (t0 = −2.85, k = 0.296 and L∞ = 16.46 cm) and males (t0 = −2.84, k = 0.272 and L∞ = 17.23 cm). The maximum age was 5 years. The relationship for males was W = 0.009L3.2596 (r2 = 0.9174, P &lt; 0.005) and that for females was W = 0.0011L3.1821 (r2 = 0.9012, P &lt; 0.005). While the highest condition (K) value was calculated in spring, the lowest value was determined in winter for both sexes. The obtained data also revealed monthly changes in the gonadosomatic index and maturity stages of male and female specimens, and the annual spawning season of this population began in March and ended in June. Fecundity ranged between 1375 and 5493 eggs/individual (mean: 2868.11 ± 36–59.69 eggs), and the relationship between total length and egg production was highly statistically significant (P &lt; 0.0001). This study provides the first data on the growth and reproduction of S. cinereus along the south-eastern Black Sea coast of Turkey.

Modeling of accumulation areas of cohesive sediments entering the southeastern Black Sea from Degirmendere River

Modeling of accumulation areas of cohesive sediments entering the southeastern Black Sea from Degirmendere River

Modeling the spatial distribution of the ctenophore Mnemiopsis leidyi A. Agassiz, 1865 in the Black Sea using a fuzzy rule-based system

Species distribution models can predict species occurrences in areas where no data is available by finding relationships between occurrences and environmental parameters. In this study, we applied a fuzzy rule-based system to model the spatial distribution of Mnemiopsis leidyi in the Black Sea and predict the probability of its presence throughout the sea. Six variables were used as predictors, including water turbidity, organic and inorganic particulate carbon, photosynthetically active radiation, light absorption by phytoplankton, sea surface temperature, and chlorophyll-a concentration. The results revealed a 0.807 accuracy of the model based on the confusion matrix. The results also showed that photosynthetically active radiation and sea surface temperature were the most important predictors shaping the distribution of this species. The findings also showed that the northern Black Sea was with the highest probability of presence, especially in Ukraine and Russia’s coastal areas. In the coastal areas of Turkey, the highest presence probability was found near Rize, Trabzon, Ordu, and from Sinop to Zonguldak. Therefore, continuous monitoring of the Turkish coastal area is crucial to better understanding the effects of climate change and anthropogenic influences on the further distribution patterns of this invasive ctenophore in the southeastern Black Sea.

Changes in the Biochemical and Fatty Acids Composition of Different Body Parts of Warty Crab (Eriphia Verrucosa, Forsskål, 1775) Caught from the Southeastern Black Sea and Their Relationship to Seasons and Sex

The study was carried out by taking samples from 10 different stations between the Giresun and Hopa coasts of the Southeastern Black Sea. In this study, the nutritional value of various edible body parts (carapace, right and left claw, and legs) of the warty crab (Eriphia verrucosa, Forsskål, 1775) was evaluated, sex seasonal proximal biochemical and fatty acid composition were compared. The highest content of protein (20.85%) was found in females (left claw) in winter and the highest content of fat (1.11%) in males (legs) in winter. Furthermore, the most dominant fatty acids in the fatty acid composition were Palmitic acid (11.2-13.9%) in SFA, Oleic acid (10.09-15.7%) in MUFA, and docosahexaenoic acid (DHA, 17.5-21.9%) in PUFA. There were no significant differences in SFA and MUFA contents in the fatty acid composition of female and male crab flesh meat samples except for the spring and summer seasons. However, Differences were obtained between the sexes in the n-3 and EPA+DHA fatty acid values in the spring season (p&lt;0.05). In addition, the amount of EPA+DHA in 100g of edible crab meat was varied in 137.7-219.3 mg.