Seawater Research Articles

The Contribution of Siliceous Plankton to Vertical Export Flux in the Eastern Mediterranean: A Comparative Study of the North Aegean, Cretan, and Ionian Seas

This study investigates the intricate dynamics of siliceous plankton species within the open marine regions of the Greek Seas, focusing on their seasonal and spatial variability. For this purpose, vertical export fluxes of diatoms (DtF), silicoflagellates (SF), and radiolaria (RF) were analyzed in three sediment trap time series obtained from the North Aegean, Cretan, and Ionian Seas. Special attention was given to diatom assemblages, resulting in the estimation of the DtF community structure and diversity for each studied site. Diatom flux values reached 353.9 × 103 valves m−2 day−1, 77.7 × 103 valves m−2 day−1, and 42.4 × 103 valves m−2 day−1 in the North Aegean, Ionian, and Cretan Seas, respectively. SF maxima were 1309.8 × 103 skeletons m−2 day−1 in the North Aegean Sea, 35.2 × 103 skeletons m−2 day−1 in the Ionian Sea, and 11.9 × 103 skeletons m−2 day−1 in the Cretan Sea (South Aegean Sea). RF values reached 13.9 × 103 radiolaria m−2 day−1, 11.9 × 103 radiolaria m−2 day−1, and 5.4 × 103 radiolaria m−2 day−1 in the North Aegean, Ionian, and Cretan Seas, respectively. The North Aegean Sea exhibited significantly higher mean total fluxes, particularly for diatoms, driven by the north-to-south oligotrophy gradient, which was influenced by riverine inflows and the nutrient-rich Black Sea water. In the Cretan and Ionian Seas, convective mixing and atmospheric deposition, especially during increased rainfall (precipitation) events, were identified as primary drivers for the increased siliceous plankton fluxes recorded in the late winter–spring months. Diatom communities were dominated by Naviculales and Fragilariales; the prevalence of the former in the North Aegean Sea is likely linked to the higher nutrient levels in its upper photic zone, as Naviculales includes species with a high affiliation to nutrient enrichment.

A multi-scale integrative approach to study the impact of a common pesticide, the dimethoate, on a mangrove fiddler crab Tubuca urvillei.

At land-sea interface, mangroves are likely to be exposed to pesticides due to agricultural run-offs. In Mayotte Island (Comoros archipelago, Mozambique Channel), dimethoate (DMT) is found in high concentrations in tomatoes, but no data confirm its presence in mangroves. We aimed at screening the presence of DMT in three mangroves of Mayotte at different levels (highest point above crops, village, upstream mangrove, downstream mangrove) and assessing the impact of DMT coupled with reduced salinity on mangrove crab physiology. To do so, we performed 24-h exposures at sublethal concentrations (10 and 100µg L-1) corresponding to 100 × and 1000 × the environmental standard (no data exist on environmental concentrations), in seawater (SW) and diluted SW (dSW). We exposed male fiddler crab Tubuca urvillei, one of the most common fiddler crabs living in mangrove areas regularly flooded and exposed to agricultural run-offs. Different physiological endpoints were considered: behaviour, acetylcholinesterase (AChE) activity, muscle energy metabolism, DNA oxidative damage and osmoregulatory capacity using hemolymph samples, posterior gills and claw muscle. We confirmed the presence of DMT in one mangrove and the effect of pesticide exposure at the different endpoints. Changes in behavioural and physiological parameters highlighted in this study could warn us of recent pesticide use upstream and help us understand past or future community-level changes in mangrove ecosystems affected by pesticide inputs.

Morphodynamics drive the transport and accumulation of anthropogenic microparticles in tropical coastal depositional systems in southeastern Brazil.

A significant limitation in current coastal pollution research is that microplastics (<5 mm) comprise only a fraction of all anthropogenic microparticles (AMP, <5 mm) scale residues. Comprehensive AMP assessments, including those comprising semisynthetic, and modified natural compositions, are lacking. For instance, the accumulation of AMP in different coastal morphological features within a depositional system remains poorly known, fueling long-lasting debates about the distribution process of microparticles. Using a multi-proxy approach, we address mutual interactions between distinct surface morphologies (tidal flats, beaches, and foredunes) and transport and deposition dynamics of AMP. This issue was addressed by analyzing sediment and water samples collected at a marine protected area in the south coastal of São Paulo (Brazil). Here, we showed that AMP abundance in the tidal mudflat (18,500-20,500 particles/kg) was four times higher than in beach sands (4700-5900 particles/kg), while the lowest abundance was observed in foredune sands (4350 particles/kg). This can be attributed to the low-energy hydrodynamics of tidal flats associated with the cohesive behavior of muddy sediments, which consequently favor trapping and act as the main sink for AMP. Further, coastal processes (waves and currents) drive AMP onshore through sediment transport from the surfzone to the beach, from where the AMP becomes available for onshore eolian transport. Higher AMP abundance (85 particles/L) was observed in the marine water samples compared to the estuarine water samples (35 particles/L). Fibers <1 mm appeared as the predominant AMP in the sediment (99-100 %) and water (80-95 %) samples, primarily consisting of modified cellulose (73 %), dye signature only (16 %), and microplastics (11 %). Consequently, we argue that to fully comprehend the spatial distribution of AMP in coastal sediments and waters, it is crucial to analyze these microparticles from an integrated perspective, primarily considering the hydro-wind dynamics of different coastal morpho-sedimentary compartments combined with sediment grain size.

Killer whales in the Gulf of Mexico and North Atlantic off the Southeastern United States

Killer whales occur in the Gulf of Mexico (GoMex) and the North Atlantic, including off the southeastern United States (SEUS). Data from cetacean surveys during 1990 – 2021 and other sources were combined to assess killer whale biology, including spatial and temporal distribution, social structure, genetics, morphology, acoustics, and predatory behavior. GoMex records occurred predominantly in oceanic waters (&amp;gt;200 m) during spring and summer. SEUS records occurred primarily in winter and spring off the North Carolina region along the shelf-edge and deeper waters, and off the east coast of Florida. Photo-identification analysis of GoMex killer whales resulted in 49 individuals sighted up to seven times with sighting histories up to 26 years, and social analysis provided evidence of long-term relationships up to 16 years. The GoMex genetic samples revealed two mtDNA haplotypes, one of which does not match any outside the GoMex. Most GoMex whales had wide non-faint saddle patches and many had cookiecutter shark scars while no scars were noted on SEUS whales. Three groups recorded in the GoMex made few calls, but a group harassing sperm whales produced many. Cetaceans and tuna are known prey in the GoMex and SEUS, respectively. Directed studies of killer whales in the GoMex areas would be difficult to implement as this species is very rare. It is therefore important to pursue ongoing efforts to collect behavioral, acoustic and any biological samples that will contribute to improve our understanding of the biology and ecology of killer whales in tropical and subtropical regions.

An optimal transformation method for inferring ocean tracer sources and sinks

Abstract. The geography of changes in the fluxes of heat, carbon, freshwater and other tracers at the sea surface is highly uncertain and is critical to our understanding of climate change and its impacts. We present a state estimation framework wherein prior estimates of boundary fluxes can be adjusted to make them consistent with the evolving ocean state. In this framework, we define a discrete set of ocean water masses distinguished by their geographical, thermodynamic and chemical properties for specific time periods. Ocean circulation then moves these water masses in geographic space. In phase space, geographically adjacent water masses are able to mix together, representing a convergence, and air–sea property fluxes move the water masses over time. We define an optimisation problem whose solution is constrained by the physically permissible bounds of changes in ocean circulation, air–sea fluxes and mixing. As a proof-of-concept implementation, we use data from a historical numerical climate model simulation with a closed heat and salinity budget. An inverse model solution is found for the evolution of temperature and salinity that is consistent with “true” air–sea heat and freshwater fluxes which are introduced as model priors. When biases are introduced into the prior fluxes, the inverse model finds a solution closer to the true fluxes. This framework, which we call the optimal transformation method, represents a modular, relatively computationally cost-effective, open-source and transparent state estimation tool that complements existing approaches.

Abstract 4138321: Marine Microplastic Levels and the Prevalence of Cardio-Metabolic Diseases in Coastline Counties: An Ecological Analysis

Background: Micro- and nanoplastics are an emerging risk factor for the development of cardiovascular diseases. The association of marine microplastic levels (MMLs) with the burden of cardiometabolic diseases at a population level remains unexplored. Aim: To investigate the association between the average microplastic concentration in the ocean water body within 200 nautical miles of US coastline surveyed between 2015 and 2020, assigned to its most adjacent coastline county, and the prevalence of type 2 diabetes (T2D), coronary artery disease (CAD), and stroke in those counties. Methods: Microplastic concentration data within 200 nautical miles of the US coastline was spatially analyzed in ArcGIS Online to calculate mean MMLs. The coastal counties were stratified into four categories based on MMLs in the adjacent ocean water body: low (0-0.005 pieces/m 3 ), medium (0.005-1 pieces/m 3 ), high (1-10 pieces/m 3 ), or very high (≥10 pieces/m 3 ). BRFSS 2019-2020 survey data was used to correlate with the prevalence of type 2 diabetes (T2D), coronary artery disease (CAD), and stroke in these counties. Univariate and population-weighted multivariate quasi-Poisson regression adjusted for median county age, sex, physician access, and baseline community vulnerability theme of the US climate vulnerability index (CVI) was used to evaluate unadjusted and adjusted associations between disease prevalence and MMLs. Results: The mean age of the population was 43 ± 6 years. The mean prevalence of T2D, CAD, and stroke was significantly higher in counties with very high MMLs (13.03%, 8.94%, and 4.17%, respectively) compared to low MMLs (11.23%, 7.43%, and 3.51%, respectively, p &lt; 0.001). The counties with very high MMLs exhibited an 18% higher adjusted prevalence of T2D (PR: 1.18 [1.13 – 1.23], p &lt; 0.001), 7% higher adjusted prevalence of CAD (PR: 1.07, [1.03 – 1.11], p &lt; 0.001), and 9% higher adjusted prevalence of stroke (PR: 1.09, 95% CI: 1.05 – 1.13, p &lt; 0.001) compared to those with low levels. Conclusion: Our study establishes a significant association between marine microplastic levels and cardiometabolic disease prevalence in coastal counties.

Assimilation of synthetic and real SWOT observations for the North Atlantic Ocean and Canadian east coast using the regional ice ocean prediction system

The Surface Water Ocean Topography (SWOT) mission significantly improves on the capabilities of current nadir altimeters by enabling two-dimensional mapping. Assimilating this advanced data into high-resolution models poses challenges. To address this, Observing System Simulation Experiments (OSSEs) were conducted to evaluate the effects of both simulated and actual SWOT data on the Regional Ice Ocean Prediction System (RIOPS). This study examines the OSSEs’ design, focusing on the simulated observations and assimilation systems used. The validity of the OSSE designs is confirmed by ensuring the deviations between the assimilation system and the Nature Run (NR) align with discrepancies observed between actual oceanic data and OSSE simulations. The study measures the impact of assimilating SWOT and two nadir altimeters by calculating root mean square forecast error for sea surface height (SSH), temperature, and velocities, along with performing wave-number spectra and coherence analyses of SSH errors. The inclusion of SWOT data is found to reduce RMS SSH errors by 16% and RMS velocity errors by 6% in OSSEs. The SSH error spectrum shows that the most notable improvements are for scales associated with the largest errors in the range of 200-400 km, with a 33% reduction compared to traditional data assimilation. Additionally, spectral coherence analysis shows that the limit of constrained scales is reduced from 280 km for conventional observations to 195 km when SWOT is assimilated as well. This study also represents our first attempt at assimilating early-release SWOT data. A set of Observing System (data denial) experiments using early-release SWOT measurements shows similar (but smaller) responses to OSSE experiments in a two nadir-altimeter context. In a six-altimeter constellation setup, a positive impact of SWOT is also noted, but of significantly diminished amplitude. These findings robustly advocate for the integration of SWOT observations into RIOPS and similar ocean analysis and forecasting frameworks.

Peculiarities of clay minerals formation in the Pleistocene sediments under specific tectonomagmatic and hydrothermal conditions of the Central Hill (Escanaba Trough, Gorda Ridge, Pacific Ocean). Communication 1. Hole ODP 1038B

Using a complex of analytical methods, clay minerals were studied in Pleistocene sediments from Hole ODP 1038B, 120.50 m deep, drilled on the northwestern edge of the Central Hill, located in the Escanaba Trough (Gorda Ridge) near a hydrothermal source with a temperature of 108°C, as well as in Pleistocene background terrigenous sediments from reference Hole ODP 1037B, drilled in the Escanaba Trough, 5 km south of Central Hill. The association of terrigenous clay minerals in sediments from Hole 1037B consists of mixed-layer smectite-illites, smectite, chlorite, illite, and kaolinite. In sediments from Hole 1038B in the interval from the bottom surface to a depth of 5–7 m, clay minerals are terrigenous. In the rest of the sedimentary section, clay minerals are represented by newly formed biotite, chlorite, and dioctahedral smectite. Their formation occurred under the conditions that arose during the intrusion of basaltic melt into the Escanaba trough with the formation of a laccolith and the subsequent rapid cooling of its flank; the intrusion was accompanied by the ascent of high-temperature hydrothermal fluid in the central discharge channel, interacting with the adjacent sediments. As a result, at the high-temperature stage of this interaction, finely dispersed biotite was formed in the sediments due to the original terrigenous clay minerals, K-feldspar and amphiboles. Then, at the rapid cooling of the hydrothermal fluid to a temperature presumably 270–330°C, partial replacement of biotite by chlorite. With further rapid cooling of the hydrothermal fluid to a temperature of 200°C and below and its mixing with sea water seeping into the sediments of the Central Hill, smectite was formed.

Sorption-desorption of rare earth metal cations by ferromanganese crusts of Govorov’s guyote of the Magellanic Mountains of the Pacific Ocean

The article presents the results of experimental studies on the sorption and desorption of rare earth metal (REM) cations by cobalt-rich ferromanganese crusts (CMC) of Govorov’s guyot. It has been established that the sorption of REM cations occurs on the ore minerals KMK – Fe-vernadite, vernadite, Mn-feroxygite, goethite. The crusts are characterized by a high exchange capacity – 1.78–3.57 mg-eq/g, which increases in a series: (Dy Gd Lu Sm Nd Y, La Eu) Ce. The sorption of REM cations proceeds by an ion exchange equivalent irreversible mechanism. The exchange complex of ore minerals consists of Na+, K+, Ca2+, Mg2+ cations, which contribute 97‒98% to their total capacity. The crusts are characterized by the group sorption of REM cations from multicomponent aqueous solutions of metal salts. The selectivity of ore manganese and ferruginous minerals of crusts to REM cations is significantly higher than to the main cations of ocean water. From experimental data on the desorption of sorbed REM cations with NaCl solution, their irreversible absorption by ore minerals follows, and the strengthening of the chemical bond of sorbed REM cations with the main structural elements of these minerals over time. An important property of ore minerals, primarily manganese minerals, is their chemical and structural stability in aqueous solutions of electrolytes. This suggests the repeated use of ferromanganese crusts as sorbents of REM cations.

An Efficient LC–HRMS-Based Approach to Evaluate Pesticide Contamination in Water Bodies with Measurement Uncertainty Considerations

Over recent decades, the global occurrence of pesticide residues in aquatic environments has been a pivotal issue; however, their trace-level concentrations necessitate the establishment of ultra-sensitive and reliable analytical approaches. To this end, the present study describes the optimization and validation of an LC-HRMS-based method for the accurate determination of 18 pesticides in river and sea water, accompanied by a measurement uncertainty estimation. This method was applied to analyze 17 real samples from agriculture and aquaculture-impacted areas in Greece and Albania. Different solid-phase extraction (SPE) protocols were tested. For the analysis, cutting-edge Orbitrap MS technology and MS/MS fragmentation, along with the use of matrix-matched calibration curves, provided unprecedented accuracy (&lt;5 ppm) and sensitivity for the confirmation of positive detections. Regarding method performance, exceptional linearity was obtained; the limits of quantification ranged from 1.7 ng L−1 to 90 ng L−1, recoveries varied from 61% to 96% in river water, while slightly higher recoveries (60–111%) were observed in seawater. In all cases, repeatability and intra-laboratory reproducibility were below 15%. The measurement expanded uncertainty (U′, k = 2) was estimated considering precision and bias. MU% values were lower than 50% in all cases, as recommended in SANTE guidelines and applied to the quantified results. The matrix effect study exhibited negative values (&lt;20%) for all compounds. Application to real samples showed a low pesticide contamination load that should not be underestimated.

Recent Findings on the Pollution Levels in the Romanian Black Sea Ecosystem: Implications for Achieving Good Environmental Status (GES) Under the Marine Strategy Framework Directive (Directive 2008/56/EC)

This study provides a comprehensive evaluation of contamination levels in the Romanian Black Sea within the framework of the Marine Strategy Framework Directive (MSFD). Over the course of five oceanographic expeditions between 2020 and 2022, data were gathered from 70 stations in transitional, coastal, shelf, and offshore waters of the Black Sea. Analyses were conducted on water, sediment, and biota samples for key contaminants: heavy metals (HMs), polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) such as organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs). The assessment identified contamination hotspots near riverine inputs, urban runoff, harbor activities, and industrial discharges. Offshore waters also showed measurable pollutant levels, likely from diffuse sources and atmospheric deposition. The key findings reveal the widespread contamination of HMs, PAHs, and POPs across the Romanian Black Sea, with concentrations in certain areas exceeding acceptable environmental thresholds, highlighting ongoing challenges for regional pollution management. PAHs were prevalent in both nearshore and offshore regions, while OCPs and PCBs were detected across various matrices, with significant concentrations observed in water and biota samples. The study emphasizes the importance of integrated assessments within the MSFD framework, suggesting that future evaluations should complement the “one out-all out” (OOAO) approach with multi-metric tools, to enhance the robustness of pollution status reporting. Despite improvements in some areas, contamination remains a critical challenge, requiring strengthened regulations, improved waste management, and increased regional cooperation to mitigate the ongoing risks to marine ecosystems. The findings provide valuable data for the upcoming national MSFD assessment cycle (2018–2023) and highlight the need for sustained monitoring and coordinated efforts to ensure long-term marine sustainability.

Description and In-Flight Assessment of the POSEIDON-3C Altimeter of the SWOT Mission

The Surface Water and Ocean Topography (SWOT) mission was launched on 16 December 2022 to measure water levels over both open ocean and inland waters. To achieve these objectives, the SWOT Payload contains an innovative Ka-band radar interferometer, called KaRIn, completed with a nadir altimeter called POSEIDON-3C that was switched on a month after launch and a few days before KaRIn. POSEIDON-3C measurements provide a link between large-scale phenomena and high resolution. The POSEIDON-3C design is based on POSEIDON-3B, its predecessor on board JASON-3. It is also a dual-frequency radar altimeter operating in C- and Ku-bands, but with some improvements to enhance its performance. Even though it is a Low Resolution Mode altimeter, its performance over open ocean, inland waters and coastal zones are indeed excellent. This paper first describes the POSEIDON-3C design and its modes with a focus on its new features and the Digital Elevation Model that drives its open-loop tracking mode. Then, we assess the in-flight performances of the altimeter from an instrumental point of view. For that purpose, special and routine calibrations have been realized. They show the good performance and stability of the radar. In-flight assessments thus provide confidence when it comes to ensuring excellent altimeter measurement stability throughout the mission duration.

Evidence of 2024 Summer as the Warmest During the Last Four Decades in the Aegean, Ionian, and Cretan Seas

The summer of 2024 witnessed record-high sea surface temperatures (SST) across the Aegean, Ionian, and Cretan Seas (AICS), following unprecedented air heatwaves over the sea under a long-term warming trend of 0.46 °C/decade for the mean atmospheric temperature (1982–2024). The respective mean SST trend for the same period is even steeper, increasing by 0.59 °C/decade. With mean summer surface waters surpassing 28 °C, particularly in the Ionian Sea, the southern Cretan, and northern Aegean basins, this summer marked the warmest ocean conditions over the past four decades. Despite a relatively lower number of marine heatwaves (MHWs) compared to previous warm years, the duration and cumulative intensity of these events in 2024 were the highest on record, reaching nearly twice the levels seen in 2018, which was the warmest until now. Intense MHWs were recorded, especially in the northern Aegean, with extensive biological consequences to ecosystems like the Thermaikos Gulf, a recognized MHW hotspot. The strong downward atmospheric heat fluxes in the summer of 2024, following an interannual increasing four-decade trend, contributed to the extreme warming of the water masses together with other met-ocean conditions such as lateral exchanges and vertical processes. The high temperatures were not limited to the surface but extended to depths of 50 m in some regions, indicating a deep and widespread warming of the upper ocean. Mechanisms typically mitigating SST rises, such as the Black Sea water (BSW) inflow and coastal upwelling over the eastern Aegean Sea, were weaker in 2024. Cooler water influx from the BSW decreased, as indicated by satellite-derived chlorophyll-a concentrations, while upwelled waters from depths of 40 to 80 m at certain areas showed elevated temperatures, likely limiting their cooling effects on the surface. Prolonged warming of ocean waters in a semi-enclosed basin such as the Mediterranean and its marginal sea sub-basins can have substantial physical, biological, and socioeconomic impacts on the AICS. This research highlights the urgent need for targeted monitoring and mitigation strategies to address the growing impact of MHWs in the region.

Sea Water Turbidity Variability and Relation to Tides and Environmental Factors in the Korean Coastal Region of the Yellow Sea

Sea Water Turbidity Variability and Relation to Tides and Environmental Factors in the Korean Coastal Region of the Yellow Sea

Microzooplankton grazing on the coccolithophore Emiliania huxleyi and its role in the global calcium carbonate cycle.

Identifying mechanisms driving the substantial dissolution of biogenic CaCO3 (60 to 80%) in surface and mesopelagic waters of the global ocean is critical for constraining the surface ocean's alkalinity and inorganic carbon budgets. We examine microzooplankton grazing on coccolithophores, photosynthetic calcifying algae responsible for a majority of open-ocean CaCO3 production, as a mechanism driving shallow dissolution. We show that microzooplankton grazing dissolves 92 ± 7% of ingested coccolith calcite, which may explain 50 to 100% of the observed CaCO3 dissolution in supersaturated surface waters. Microzooplankton grazing on coccolithophores is thus a substantial, previously unrecognized biological mechanism affecting the ballasting of organic carbon to deeper waters, the ecology and fitness of microzooplankton themselves due to buffering of food vacuole pH, and ultimately the continued ability of the surface ocean to take up atmospheric carbon dioxide.

Ross Ice Shelf frontal zone subjected to increasing melting by ocean surface waters.

Solar-warmed surface waters subduct beneath Antarctica's ice shelves as a result of wind forcing, but this process is poorly observed and its interannual variability is yet to be assessed. We observe a 50-meter-thick intrusion of warm surface water immediately beneath the Ross Ice Shelf. Temperature in the uppermost 5 meters decreases toward the ice base in near-perfect agreement with an exponential fit, consistent with the loss of heat to the overlying ice. Ekman forcing drives a heat transport into the cavity sufficient to contribute considerably to near-front melting; this transport has increased over the past four decades, driven by the increasing heat content of the ice-front polynya. Interannual variability of the heat transport is driven by zonal wind stress. These results provide a benchmark against which model performance may be assessed as we seek to reduce uncertainty around the contribution of basal melting to sea level rise.

Increase of Reliability of Anomalies Detection on Images at Formation of Their Feature Vectors in Wavelet Bases

The method of detection of life rafts and lifeboats in the water area of seas and oceans after shipwrecks based on the recognition of anomalies in the processed images, which increases the probability of recognition of monitoring objects, is proposed. The approach to solving such a problem is substantiated. The formulation of the problem of object recognition from the perspective of binary classification in the detection of anomalies is presented. The analytical expression for the decision-making algorithm is obtained. The possibility of formalization of image matrices in the form of histograms of color (brightness) intensity distributions is considered. The contrast of the feature space on their basis is estimated. It is suggested that the contrast of feature spaces be increased due to the secondary processing of histograms of distributions in the basis of multiple-scale wavelet decomposition. The possibility of realization of wavelet transformations on the basis of Haar functions and Gauss wavelets of the 1st and 2nd orders is considered. The mechanism of formation of secondary feature vectors from three-dimensional wavelet transforms by averaging their coefficients along the time shift axis is substantiated. It is shown that at the same dimensionality of histograms of brightness distribution with newly formed feature vectors, the latter provide higher contrast of feature spaces. It is recommended to use a Gaussian wavelet of the 2nd order for the formalization of images in jpeg format, which provides, other things being equal, a greater magnitude of differences for images containing anomalies. An approach to probabilistic evaluation of the algorithm for automatic image recognition is developed. The analytical expression is obtained and its constituent elements are justified. Graphical dependences of the probability of correct detection (recognition) of anomalies, depending on the size in relation to the total area of the frame and the dispersion of the underlying background are given. The results of the experiment on image recognition with a lifeboat in the ocean water area are presented. The directions of further research are defined.

ВЛИЯНИЕ ПРИЛИВА НА ВОДООБМЕН ЧЕРЕЗ ПРОЛИВ ЛАПЕРУЗА

Based on the analysis of oceanographic survey materials on the standard section S1 and satellite information, important features of the influence of tidal currents on the formation of hydrological conditions in the La Perouse Strait and adjacent waters have been identified. It was revealed that in the warm season, when the seasonal flow is directed from the Sea of Japan to the Sea of Okhotsk (Soya Warm Current), at the high tide in the northern part of S1 section the cold water with low salinity is observed in the surface layer (the temperature may differ from the southern stations by 3 times, and the salinity by 2 psu). At low tide in the northern part of S1 the water is also cold, but with high salinity, which indicates the inflow of water from the West Sakhalin current into the Sea of Okhotsk. The temperature contrasts between the northern and southern parts of the Strait are also confirmed by satellite observations. During the cold season in the northern part of the strait, there is a flow of colder and less salty Okhotsk Sea water into the southeastern part of the Tatar Strait. It is wider and more developed in depth compared to the summer season. At low tide, when the tidal current is directed to the east, this flow narrows noticeably.

Multivariate Environmental Factors and Seasonal Spatial Dynamics Affecting the Phytoplankton Community in Yazhou Bay, South China Sea

This study investigated phytoplankton and water environmental factors in Yazhou Bay, South China Sea, during the winter, spring, and summer of 2023. It examined phytoplankton community structure, subgroup heterogeneity, and key environmental drivers. Phytoplankton abundance ranged from 0.08 to 14.30 × 10⁴ cells·L−1, with high concentrations in estuary and nearshore zones. In summer, currents carry phytoplankton offshore, with stratification leading to high sedimentation in southern offshore waters. RDA results indicated that in winter and spring, inorganic nitrogen mainly influences phytoplankton distribution, while silicate is the primary factor in summer. Although seasonal differences in total phytoplankton abundance are minimal, significant horizontal and vertical distribution variations exist. Diverse preferences of different phytoplankton species for temperature, salinity, nitrogen, and phosphorus result in high species diversity. The Shannon–Wiener diversity index (H′) averages 3.96 ± 0.09, and the Pielou evenness index (J) averages 0.82 ± 0.01. Dominant species include Pseudo-nitzschia pungens, Skeletonema costatum, and Rhizosolenia sinica. Influenced by external oceanic water masses, estuary input, and islands, phytoplankton subgroups show regional and seasonal variations. Despite recorded harmful algal blooms (HABs) in adjacent waters, Yazhou Bay’s high biodiversity and low cell density suggest a low HAB risk, though future risks due to climate change and human activities remain.

Tolerance of free-living larval stage of a parasite from coastal mining areas in northern Humboldt Current to copper pollution at low and high temperatures.

Metal pollution is a worldwide problem and one of the greatest threats to ecosystem integrity due to its toxicity, persistence, and bioaccumulation in biological systems. Anthropogenic pollution impacts marine organisms and host-parasite dynamics, with the northern Chilean coast experiencing elevated copper levels in marine waters and sediments due to mining activities. In this study, we assessed the effects of exposure to copper concentrations at low and high-water temperatures on the survival and longevity of the marine parasite Himasthla sp. cercariae (Trematoda: Digenea) using the snail Echinolittorina peruviana as its first intermediate host. Snails were collected from intertidal rocky pools in northern Chile (23°S). To assess parasite survival and longevity, cercariae were collected from a pool of infected snails, and their mortality was recorded every 6 hours until all cercariae were dead. In a preliminary experiment conducted at 19°C, cercariae were exposed to different copper concentrations (0.2, 1.5, 3.0, and 6.0 mg/L) for 78 hours. Cercariae showed tolerance to copper. However, at the higher copper concentration (6 mg/L), survival was negatively impacted (50%) at 54 hours. In contrast, at the lower concentration (0.2 mg/L) and in the control group, cercariae sustained a 73-90% survival rate even after 54 hours. Based on these findings, we conducted subsequent experiments involving two copper treatments (0.2 and 3.0 mg/L) and two temperatures (14 and 22°C). Survival and longevity were significantly higher at lower temperature and copper concentration (14°C and 0.2 mg/L). Conversely, at higher temperature and copper concentration (22°C and 3 mg/L), survival and longevity decreased to only 66 hours. Our results show that Himasthla sp. cercariae tolerated most copper concentrations, with vulnerability observed primarily in high water temperatures, indicating an adverse effect on cercariae performance. This study contributes valuable insights into how parasites respond to environmental pollution, in marine ecosystems influenced by anthropogenic activities.