Coastal Marine Waters Research Articles

Chromosome-level genome assembly of the cosmopolitan diatom Skeletonema costatum provides insights into ecological adaptation

The cosmopolitan diatom species Skeletonema costatum is an ecologically important dominant phytoplankton frequently found in the coastal estuarine and marine waters, and often causes harmful algae blooms. Despite of its critical ecological importance, chromosome-level genome assemble is still unavailable, hindering in-depth understanding of their evolution and environmental adaption. Here, we report a chromosome-level genome assembly for the marine diatom species S. costatum. The assembled genome size was 136.49 Mb, with a contig N50 of 302 Kb and 95.30 % of the reads anchored into 23 pseudo-chromosomes with a scaffold N50 of 6.19 Mb. A total of 28,321 protein-coding genes were predicted, with 86.03 % being functional annotated. The BUSCO assessment of genome assembly and genome annotation were both above 90 %. Phylogenetic analysis showed the expected topology, with S. costatum and its closely related species S. marinoi diverged from their common ancestor around 22.6 million years ago. The genome size of S. costatum is comparatively larger than those of its closely related diatoms, due mostly to its higher transposable element contents and larger number of proteincoding genes. Collinearity analysis revealed strong collinearity between S. costatum and other Skeletonema with most chromosomes showing clear one-to-one correspondences. A larger family of nine copies of the cryptochrome genes that function as blue light photoreceptors were identified in S. costatum, which could contribute its ecological success. The availability of the high-quality chromosome-level genome assembly for S. costatum represents a valuable resource that may facilitate comparative genomics for revealing important ecological clues and gene families, and future genetics and environmental studies among Skeletonema species.

Hydrographic shifts in coastal waters reflect climate-driven changes in hydrological regimes across Northwestern Patagonia

Climate-driven changes in freshwater inputs have been shown to affect the structure and function of coastal ecosystems. We evaluated changes in the influence of river runoff on coastal systems of Northwestern Patagonia (NWP) over recent decades (1993–2021) by combined analysis of long-term streamflow time series, hydrological simulation, satellite-derived and reanalysis data on sea surface conditions (temperature, turbidity, and salinity). Significant decreases in minimum streamflow across a zone spanning six major river basins were evident at weekly, monthly, and seasonal scales. These changes have been most pronounced in mixed-regime northern basins (e.g., Puelo River) but appear to be progressing southward to rivers characterised by a nival regime. In the adjacent two-layer inner sea, reduced freshwater input corresponds with a shallower halocline and increased surface temperatures across northern Patagonia. Our results underscore the rapidly evolving influence of rivers on adjacent estuarine and coastal waters in NWP. We highlight the need for cross-ecosystem observation, forecasting, mitigation and adaptation strategies in a changing climate, together with corresponding adaptive basin management of systems that supply runoff to the coastal marine waters.

Tracking suspended particulate organic matter biochemistry from glacial meltwater runoff to coastal waters of an Antarctic fjord

Increased glacier melting runoff in Antarctica involves intensification of freshwater, nutrients, sediments and organic matter inputs from land to the sea, which is impacting coastal ecosystems. Basic environmental characteristics of water and biochemical composition of suspended particulate organic matter (POM) both in the proglacial melting runoff system (PROGLARS) of Collins Glacier and marine surface waters of Collins Bay was studied based on organic biopolymers and molecular level analysis of amino acids (AAs), to discern among sources and degradation state in the two environments. Hierarchical Clustering Analysis revealed that PROGLARS stations and marine stations form two distinct groups in terms of water physicochemical characteristics and suspended POM biochemical composition. These differences are the consequence of low restricted contribution of freshwater from Collins Glacier runoff into the coastal-marine environment. Our results evidenced low concentrations of terrestrial suspended POM in marine waters of Collins Bay mainly attributed to low meltwater inputs between the 1st and 7th of February 2018. In terms of macromolecular composition, the predominance of proteins, denote the labile nature of suspended POM in the two environments. Suspended POM in Collins Bay is labile, poorly degraded, representing a protein supplemented food resource, with high energetic value and easily assimilated by heterotrophic marine organism. AAs composition supported less degraded suspended POM derived from marine phytoplankton in surface waters of Collins Bay, whereas, great degradation of suspended POM in the proglacial runoff system of Collins Glacier. Changes in the biochemistry of suspended POM caused by glacial melting and retreat, may affect food features and availability, the productivity of ecosystems, and ultimately, the capacity of Antarctic fjords to act as carbon sinks and climate regulators. Considering low influence of Collins Glacier meltwater in coastal marine waters of Collins Bay, due to the relatively slow retreat of Collins Glacier and low development of its meltwater runoff system, the results of our work are relevant as baseline information for comparison with other Antarctic fjords. Further knowledge about meltwater runoff and suspended POM input dynamics in Antarctic coastal ecosystems, is critical, particularly in areas prone to undergo increased glacier melting in the following decades.

Antimicrobial resistance characterization of Enterococcus faecium, Enterococcus faecalis and Enterococcus hirae isolated from marine coastal recreational waters in the State of São Paulo, Brazil.

Coastal water quality is facing increasing threats due to human activities. Their contamination by sewage discharges poses significant risks to the environment and public health. We aimed to investigate the presence of antibiotic-resistant Enterococcus in beach waters. Over a 10-month period, samples were collected from four beaches in the State of São Paulo (Brazil). Enterococcus isolates underwent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and molecular analysis for accurate genus and species identification. The antimicrobial susceptibility for 14 antibiotics was evaluated using the disc diffusion method followed by a multidrug-resistance (MDR) classification. PCR amplification method was used to detect antimicrobial resistance genes (ARGs). Our findings revealed the prevalence of Enterococcus faecalis, E. faecium and E. hirae. Out of 130 isolates, 118 were resistant to multiple antibiotics. The detection of resistance genes provided evidence of the potential transfer of antibiotic resistance within the environment. Our findings underscore the necessity for continuous research and surveillance to enhance understanding of the pathogenicity and antimicrobial resistance mechanisms of Enterococcus, which is crucial to implement effective measures to preserve the integrity of coastal ecosystems.

Present Scenario of Ocean Warming (OW) and Ocean Acidification (OA) in the Coastal and Marine Waters of the Bay of Bengal, Bangladesh and Implications of OW and OA on Fisheries and Seafood of Bangladesh: A First Regional Review Study

Bangladesh is one of the most vulnerable countries in the world to climate change. However, data relevant to ocean warming (OW) and ocean acidification (OA) are not readily available. This is the first study to review the available data relating to OW and OA covering the three parts (eastern, central and western parts) of the coastal marine waters (CMWs) of the Bay of Bengal (BoB), Bangladesh. The review compared the data collected from the three parts of the BoB, Bangladesh with the data and information of previous research carried out within the Indian subcontinent of the BoB (2000-2023). The present research provides an overview of water quality data relevant to OW and OA and the correlation among different water quality parameters. Our research found that the sea surface temperature is increasing and pH levels are decreasing in the BoB, Bangladesh. The current pH in BoB, Bangladesh is still alkaline, with an overall mean pH of 7.58 compared with the global ocean pH of 8.1. DO (overall mean: 6.09 mg/L), Ωarg (overall mean: 2.27) and Ωcal (overall mean: 3.59) levels were found to be within the safe thresholds for marine biota (fish, crustaceans, mussels, oysters, corals and echinoderms). Conversely, nitrate levels (mean: 2.29 mg/L) were found to be high, the concentration of which may enhance nitrogen pollution, algal blooms and hypoxia in the BoB, Bangladesh. The implications of OW and OA on Bangladesh’s fisheries and seafood have been briefly discussed.

Characterization of Opportunistic Pathogenic Multi-Drug Resistant Bacteria Isolated from Marine Coastal Water in Jazan, Saudi Arabia

Characterization of Opportunistic Pathogenic Multi-Drug Resistant Bacteria Isolated from Marine Coastal Water in Jazan, Saudi Arabia

Thermal conditions in the marine coastal waters as a factor favorable for formation of extra-strong year-classes of Karaginsky pink salmon

Variability of the timing for downstream migration of juvenile pink salmon from the Hailulya River to the adjacent coastal waters of Karaginsky Bay is considered and influence of the coastal water temperature on strength of the year-classes for two generative lines of pink salmon spawning in the Karaginsky Bay is analyzed for 1978–2020. The optimal conditions for the downstream migration in the period after 2002 are determined as the mean weighted per migration intensity water temperature > 5.6 o C (up to 7.8 о С on average with the maximum 9.9 о С in some years) and a stable increasing of the temperature during migration. The factor of food availability for juveniles became less important for formation of the Karaginsky pink salmon year-classes since the late 2000s, in comparison with the temperature. Statistical model is proposed for the year-class strength dependence on the temperature of coastal waters in late June and the parents number (R2 = 0.791). The modeled hindcasts of the pink salmon returns in 2021–2023 were rather satisfactory. Given these new results, the limits of pink salmon escapement to spawning grounds could be reconsidered and fishery management models should be adjusted to modern conditions of unrestricted juvenile feeding to get and rationally exploit super-strong year-classes of this species.

The physical and biogeochemical parameters along the coastal waters of Saudi Arabia during field surveys in summer, 2021

Abstract. During the last decades, the coastal areas of the Kingdom of Saudi Arabia, on the Red Sea and the Arabian Gulf, have been subjected to intense economic and industrial growth. As a result, it may be expected that the overall environmental status of Saudi Arabian coastal marine waters has been affected by human activities. As a consequence, adequate management of the Saudi Arabian coastal zone requires an assessment of how the various pressures within this zone impact the quality of seawater and sediments. To this end, environmental surveys were conducted over 15 hotspot areas (areas subject to environmental pressures) in the Saudi Arabian coastal zone of the Red Sea and over three hotspot areas in the Saudi Arabian waters of the Arabian Gulf. The survey in the Red Sea, conducted in June/July 2021, acquired measurements from hotspot areas spanning most of the Saudi coastline, extending from near the Saudi–Jordanian border in the north to Al Shuqaiq and Jizan Economic City (close to the Saudi–Yemen border) in the south. The survey in the Arabian Gulf, carried out in September 2021, included the areas of Al Khobar, Dammam and Ras Al Khair. The main objective of both cruises was to record the physical and biogeochemical parameters along the coastal waters of the kingdom, tracing the dispersion of contaminants related to specific pressures. Taken together, these cruises constitute the first multidisciplinary and geographically comprehensive study of contaminants within the Saudi Arabian coastal waters and sediments. The measurements acquired revealed the influence of various anthropogenic pressures on the coastal marine environment of Saudi Arabia and also highlighted a strong influence of hydrographic conditions on the distribution of biochemical properties in the Red Sea and the Arabian Gulf. The data can be accessed at SEANOE https://doi.org/10.17882/96463 (Abualnaja et al., 2023), whereas the details of the sampling stations are available at https://mcep.kaust.edu.sa/cruise-postings (last access: 25 March 2024). The dataset includes the parameters shown in Tables 1a, b and 2a.

Attachment of Salmonella Typhimurium to Fish Surfaces from a Suspension in Seawater and the Effect of Subsequent Washing

ackground: Salmonella contamination of seafood is an important consumer health concern. Anthropogenic contamination of coastal-marine water is an important source of seafood contamination with Salmonella. In this study, we aimed to investigate the extent of Salmonella attachment when fish is exposed to contaminated seawater and also, the effect of washing on the removal of Salmonella attached to fish surface. Methods and Findings: Bombay duck (Harpadon nehereus) fish was dipped in seawater artificially contaminated with 5 log CFU/ ml Salmonella Typhimurium for 30, 45 and 60 seconds and the number of bacteria present on the fish surface was quantified by surface plating. Separately, the effect of rinsing Salmonella-contaminated fish for 30, 45 and 60 seconds on the removal of Salmonella from the fish surface was investigated. The results showed attachment of bacteria in significant numbers, in the range of 3.6 – 4.16 log CFU/g, within 60 seconds of exposure to Salmonella-contaminated seawater. However, no significant reduction in the Salmonella counts was observed after 30 to 60 seconds of rinsing of fish in freshwater. Conclusion: The results suggest that Salmonella Typhimurium can readily attach to the fish surface from a seawater medium and resist detachment by routine washing procedures.

Electromagnetic Fields (Including Microwaves) Can Lower the Immune Response and Even Change The DNA

Background: Salmonella contamination of seafood is an important consumer health concern. Anthropogenic contamination of coastal-marine water is an important source of seafood contamination with Salmonella. In this study, we aimed to investigate the extent of Salmonella attachment when fish is exposed to contaminated seawater and also, the effect of washing on the removal of Salmonella attached to fish surface. Methods and Findings: Bombay duck (Harpadon nehereus) fish was dipped in seawater artificially contaminated with 5 log CFU/ ml Salmonella Typhimurium for 30, 45 and 60 seconds and the number of bacteria present on the fish surface was quantified by surface plating. Separately, the effect of rinsing Salmonella-contaminated fish for 30, 45 and 60 seconds on the removal of Salmonella from the fish surface was investigated. The results showed attachment of bacteria in significant numbers, in the range of 3.6 – 4.16 log CFU/g, within 60 seconds of exposure to Salmonella-contaminated seawater. However, no significant reduction in the Salmonella counts was observed after 30 to 60 seconds of rinsing of fish in freshwater. Conclusion: The results suggest that Salmonella Typhimurium can readily attach to the fish surface from a seawater medium and resist detachment by routine washing procedures.

The genome of the rayed Mediterranean limpet Patella caerulea (Linnaeus, 1758).

Patella caerulea (Linnaeus, 1758) is a mollusc limpet species of the class Gastropoda. Endemic to the Mediterranean Sea, it is considered a keystone species due to its primary role in structuring and regulating the ecological balance of tidal and subtidal habitats. It is currently being used as a bioindicator to assess the environmental quality of coastal marine waters and as a model species to understand adaptation to ocean acidification. Here, we provide a high-quality reference genome assembly and annotation for P. caerulea. We generated ∼30 Gb of Pacific Biosciences high-fidelity data from a single individual and provide a final 749.8 Mb assembly containing 62 contigs, including the mitochondrial genome (14,938 bp). With an N50 of 48.8 Mb and 98% of the assembly contained in the 18 largest contigs, this assembly is near chromosome-scale. Benchmarking Universal Single-Copy Orthologs scores were high (Mollusca, 87.8% complete; Metazoa, 97.2% complete) and similar to metrics observed for other chromosome-level Patella genomes, highlighting a possible bias in the Mollusca database for Patellids. We generated transcriptomic Illumina data from a second individual collected at the same locality and used it together with protein evidence to annotate the genome. A total of 23,938 protein-coding gene models were found. By comparing this annotation with other published Patella annotations, we found that the distribution and median values of exon and gene lengths was comparable with other Patella species despite different annotation approaches. The present high-quality P. caerulea reference genome, available on GenBank (BioProject: PRJNA1045377; assembly: GCA_036850965.1), is an important resource for future ecological and evolutionary studies.

First record of the genus Togula (Gymnodiniales, Dinophyceae) and of the species T. jolla for the South-West Atlantic coastal waters

In the framework of a phytoplankton and biotoxin monitoring program implemented since 2008 in marine coastal waters of the Buenos Aires Province (Argentina), a gymnodinioid, photosynthetic dinoflagellate was isolated from a sample collected in Santa Teresita, establishing the strain LPCc007. The strain was identified as belonging to the psammophilic genus Togula by light microscopy based on the following distinctive characters: morphology of the cell dorso-ventrally flattened, and course of the cingulum, highly asymmetric, descending, with its ends displaced by about one to two thirds of the total length of the cell and joined by an oblique intercingular groove. The comparative morphological analysis between the motile vegetative cells of the isolated strain and the three species of the genus described to date, did not reveal significant differences that would allow it to be determined at a specific level. Instead, the pattern of development of longitudinal grooves on the hypocone of cells about to undergo mitosis observed in strain LPCc007, perfectly agrees with that described for T. jolla as a differential character. The morphological identification was consistent with LSU rDNA (D1-D2) based phylogeny that showed the sequence aggregation in the T. jolla clade. This is the first report of the genus Togula and the species T. jolla from Argentina and the South-West Atlantic Ocean coastal waters.

Ecomorphology of Selected Penaeid Shrimp in the Coastal Marine Waters of Tamil Nadu (Southern India)

Ecomorphology of Selected Penaeid Shrimp in the Coastal Marine Waters of Tamil Nadu (Southern India)

Taxonomic and functional stability overrules seasonality in polar benthic microbiomes.

Coastal shelf sediments are hot spots of organic matter mineralization. They receive up to 50% of primary production, which, in higher latitudes, is strongly seasonal. Polar and temperate benthic bacterial communities, however, show a stable composition based on comparative 16S rRNA gene sequencing despite different microbial activity levels. Here, we aimed to resolve this contradiction by identifying seasonal changes at the functional level, in particular with respect to algal polysaccharide degradation genes, by combining metagenomics, metatranscriptomics, and glycan analysis in sandy surface sediments from Isfjorden, Svalbard. Gene expressions of diverse carbohydrate-active enzymes changed between winter and spring. For example, β-1,3-glucosidases (e.g. GH30, GH17, GH16) degrading laminarin, an energy storage molecule of algae, were elevated in spring, while enzymes related to α-glucan degradation were expressed in both seasons with maxima in winter (e.g. GH63, GH13_18, and GH15). Also, the expression of GH23 involved in peptidoglycan degradation was prevalent, which is in line with recycling of bacterial biomass. Sugar extractions from bulk sediments were low in concentrations during winter but higher in spring samples, with glucose constituting the largest fraction of measured monosaccharides (84% ± 14%). In porewater, glycan concentrations were ~18-fold higher than in overlying seawater (1107 ± 484 vs. 62 ± 101μg C l-1) and were depleted in glucose. Our data indicate that microbial communities in sandy sediments digest and transform labile parts of photosynthesis-derived particulate organic matter and likely release more stable, glucose-depleted residual glycans of unknown structures, quantities, and residence times into the ocean, thus modulating the glycan composition of marine coastal waters.

Prvi opis proizvodnje piva pomoću morskih kvasaca

Most of the yeast species we encounter daily are terrestrial, but they are also found in the marine environment. Marine yeasts occur in estuaries, coastal and open marine waters, sediments, and as epi- and endobionts of various marine organisms. This study focuses on the fermentation capabilities of marine yeasts isolated from the central Adriatic Sea for use in the brewing process. Sampling was performed at a sea temperature of 12°C to avoid collecting yeasts introduced into the marine environment by human activities. Four nutrient media designed for yeast isolation and growth were used to isolate yeasts from the marine samples: Yeast Malt Agar (YM), Yeast Malt Agar with antibiotics, acidified Yeast Malt Agar, and Sabouraud Dextrose Agar. Sixteen yeast colonies were successfully isolated, and only three were positive in the fermentationtest and were further determined to species level. Of the three species identified as capable of fermentation, Candida famata completely fermented the wort and produced a beer. Candida pelliculosa fermented slowly over an extended period and did not produce a usable beer, while Candida sake did not ferment the wort at all. To our knowledge, this is the first time that marine yeast isolates have been used experimentally for beer fermentation, indicating potential for use as nonconventionalyeasts in brewing and beer production. Further investigations should include professional standard fermentation, aroma and genetic studies.

Assessment of pollutants in coastal waters, sediments, and biota of marine ecosystems in Algeria, North Africa

This study aims to assess the chemical and ecological quality of the marine ecosystem in Algerian central coastal zone (Bay of Algiers (AB) and Bou-Ismail Bay (BIB)) by examining several quality indicators of the marine ecosystem: water, sediment, and biota. Except for stations near the mouths of wadis and industrial and urban discharges released without prior treatment, the study of the physicochemical water quality in the different sampling stations revealed a more or less normal variation in temperature and salinity. According to nutrient salt analysis, all studied stations (in AB and BIB) have high nitrogen levels, such as ammonium and nitrate. However, low levels of phosphate were detected, indicating that this element is scarce in the Algerian coastal marine waters. Three trace metals were also analyzed in the sediments of both bays. Pb ranged from 21.15 to 52.69 μg g–1 dry weight (dw), Zn from 19.32 to 175.1 μg g–1 dw and Cd between 0.87 and 2.031 μg g–1 dw. Contamination factors ranged from 0.62 to 1.55 for Pb, 0.2 to 1.85 for Zn and 1.74 to 4.04 for Cd. Analysis of these three metals in sediment samples reveals their presence at most stations studied. The contamination index calculation shows a moderate anthropogenic intake that requires continuous monitoring to protect the study area’s ecosystem. Crucially, the analysis of fish products revealed a lack of chemical risk concerning trace metals, known for their detrimental health effects. However, this conclusion does not dismiss the potential for subtle contamination, warranting persistent environmental surveillance. Consequently, sustained efforts in environmental monitoring are imperative to ensure the preservation of the marine ecosystem amidst escalating anthropogenic pressures.

Use of Sentinel-3 OLCI Images and Machine Learning to Assess the Ecological Quality of Italian Coastal Waters.

Understanding and monitoring the ecological quality of coastal waters is crucial for preserving marine ecosystems. Eutrophication is one of the major problems affecting the ecological state of coastal marine waters. For this reason, the control of the trophic conditions of aquatic ecosystems is needed for the evaluation of their ecological quality. This study leverages space-based Sentinel-3 Ocean and Land Color Instrument imagery (OLCI) to assess the ecological quality of Mediterranean coastal waters using the Trophic Index (TRIX) key indicator. In particular, we explore the feasibility of coupling remote sensing and machine learning techniques to estimate the TRIX levels in the Ligurian, Tyrrhenian, and Ionian coastal regions of Italy. Our research reveals distinct geographical patterns in TRIX values across the study area, with some regions exhibiting eutrophic conditions near estuaries and others showing oligotrophic characteristics. We employ the Random Forest Regression algorithm, optimizing calibration parameters to predict TRIX levels. Feature importance analysis highlights the significance of latitude, longitude, and specific spectral bands in TRIX prediction. A final statistical assessment validates our model's performance, demonstrating a moderate level of error (MAE of 0.51) and explanatory power (R2 of 0.37). These results highlight the potential of Sentinel-3 OLCI imagery in assessing ecological quality, contributing to our understanding of coastal water ecology. They also underscore the importance of merging remote sensing and machine learning in environmental monitoring and management. Future research should refine methodologies and expand datasets to enhance TRIX monitoring capabilities from space.

Development of standards for assessing water quality in marine coastal waters of Bahrain

Marine coastal waters of Bahrain are under pressure due to human activities and climate change. We used marine monitoring data (2005–2020) from 27 sites to establish baseline conditions and develop standards for assessments of water quality. Five hydrodynamic regions were identified: Oyster Beds, North, West, East, East (Coastal). Data from Oyster Beds sites, likely to be less impacted by human activities, were used to determine baseline conditions. For most parameters, candidate thresholds were based on 50 % and 100 % variation from baseline and 95th percentiles. Comparisons of data against different thresholds showed different outcomes. Overall, results indicate good water quality, with potential concerns in East (Coastal). Trend analyses showed some significant trends in all regions: downward (favourable) for some parameters (e.g. turbidity: North) and upward for others (e.g. nitrate: Oyster Beds, East and East (Coastal)). Future work requires greater understanding around optimum guidelines that protect and mitigate any adverse ecological impacts.

Exploring the Structure of Static Net Fisheries in a Highly Invaded Region: The Case of Rhodes Island (Eastern Mediterranean)

Experimental fishing was conducted in three different locations along the coastal marine waters of eastern Rhodes Island, Levantine Sea, Hellas, from April 2021 to March 2022 on a monthly basis. Twelve samplings with gill nets and 12 with trammel nets at each of three selected locations resulted in a total of 72 samplings. The numbers of indigenous and non-indigenous species, as well as their abundances, biomasses and frequencies of occurrence, were recorded. Overall, the samplings yielded 71 species, of which 14 were non-indigenous. The total abundance was 1879 individuals, corresponding to a fish biomass of 433.57 kg. Fistularia commersonii, Sparisoma cretense and Pterois miles exhibited the highest numbers of individuals, whereas three of the invasive alien species in the Hellenic seas, namely, F. commersonii, Lagocephalus sceleratus and P. miles had the highest biomasses. The results exhibited a strong presence of P. miles in the Rhodian fisheries as the dominant invasive species based on the examined indicators (i.e., abundance, catches and frequency of occurrence). Comparisons in regard to the collected biomass between the locations, seasons, species origins and types of fishing gear were performed. All three locations were characterized by a good ecological status based on the relationship between abundance and biomass. The results of this study contribute valuable information on the ongoing changes in small-scale fisheries in the marine waters of Rhodes Island, which is one of the Eastern Mediterranean regions most affected by biological invasions.

Cardiac Activity of <i>Pontastacus leptodactylus</i> Esch. (Decapoda) under Prolonged Exposure to High Salinity: on the Possibility of Using Freshwater Crayfish in Testing of Brackish Waters

In this study, we analyzed the characteristics of the cardiac activity of crayfish during long-term keeping of animals in an environment with high salinity (6.5‰) in order to find out the fundamental possibility of using them as bioindicators in bioelectronic systems for monitoring the quality of marine coastal waters under high anthropogenic load. Similar salinity values were noted for many bays of the Baltic Sea sub-regions, for example, the Tallinn and Bothnian bays, which are characterized by intense anthropogenic load. It was found that an increase in water salinity from 0 to 6.5‰ caused an initial short-term increase in heart rate (HR) by 30%. It has been shown that crayfish can not only successfully survive for 1 month in high salinity water, but also change the characteristics of cardiac activity to a small extent. Some features were revealed in crayfish in water with altered salinity. During exposure to saline solution, crayfish showed a clear diurnal rhythm of cardiac activity. The rhythmicity of the heart rate disappeared a few days before the molt in both fresh and salt water. The study made it possible to draw a conclusion about the possibility of using freshwater crayfish in bioelectronic systems for continuous monitoring of the functional state of representatives of the local biota and for identifying the biological effects of pollutants in both fresh and brackish water.