Remote sensing is a valuable tool for surveying submerged aquatic vegetation (SAV) distribution patterns at extensive spatial and temporal scales. Only regular mapping over successive time periods (e.g., months, years) allows for a quantitative assessment of SAV loss or recolonization extent. Still, there are only a limited number of studies assessing temporal changes in SAV patterns. ESA Sentinel-2 (S2) has a high revisiting frequency permitting the multi-temporal assessment of SAV dynamics both seasonally and inter-annually. In the current study, a physics-based IDA (Image Data Analysis) model was used for the reconstruction of past SAV percent cover (%cover) patterns in the Baltic Sea coastal waters based on S2 archived images. First, we aimed at capturing and quantifying intra-annual spatiotemporal SAV dynamics happening during a growing season. Modeling results showed that significant changes took place in SAV %cover: the extent of low-cover (0–30% coverage) and intermediate-cover (30–70% coverage) areas decreased, while high-cover (70–100% coverage) areas increased during the growing period. Secondly, we also aimed at detecting SAV %cover spatiotemporal variations inter-annually (over the years 2016–2022). Inter-annual variability in %cover patterns was greater in the beginning of the vegetation period (May). The peak of the growing period (July/August) showed greater stability in the areal extent of the %cover classes.

Coastal ecosystems such as salt marshes, seagrass meadows, and kelp forests contribute to climate regulation as carbon sinks. However, coastal ecosystems may act as carbon sources as beach wrack accumulations may release greenhouse gases (GHG) during decomposition. The magnitude of GHG emissions of beach wrack accumulations under natural conditions are poorly understood, hampering accurate blue carbon accountings. In this study, we assessed the spatio-temporal variability and environmental factors driving CO2, CH4 and N2O emissions from beach wrack accumulations on a temperate sandy beach. Beach wrack accumulations, dominated by Zostera marina and opportunistic brown macroalgae, presented variable spatio-temporal dynamics. Annual beach wrack GHG emissions achieved up to 77,915 mg m-2 d-1 CO2e (CO2 equivalents) and varied largely throughout the study period due to interactive effects of temperature, wave exposure, beach wrack biomass moisture, abundance, and species composition. Our findings showed that methane emissions in new, freshly deposited, and in drifting wrack in the water reached up to 100 mg m-2 d-1, representing up to 57 % of annual CO2e emissions occurring throughout the year. Nitrous oxide emissions were highly variable and comprised a minor extent (i.e., up to 4 %) of annual CO2e emissions. Together, wrack CH4 and N2O emissions provided 13.69 g CO2 m-2 per year to the atmosphere. Our findings indicate that excessive opportunistic macroalgae biomass driven by eutrophication may explain increased CO2 and N2O emissions. We conclude that whilst beach wrack depositions are a natural and essential part of coastal ecosystems, they may provide an extra source of GHG to the atmosphere, potentially counteracting the role of vegetated coastal ecosystems as carbon sinks.

The distribution data of 11 soft substrate charophyte and angiosperm species were analyzed. Our study aimed to elucidate the co-occurrence patterns among these sympatric macrophyte species and quantify their distribution areas. The central hypothesis of this study proposed that the observed co-occurrence patterns among the studied species deviate from what would be expected by random chance. Macrophyte occurrence data was derived from an extensive field sampling database. Environmental variables available as georeferenced raster layers including topographical, hydrodynamic, geological, physical, chemical, and biological variables were used as predictor variables in the random forest models to predict the spatial distribution of the species. Permutation tests revealed statistically significant deviations from random co-occurrence patterns. The analysis demonstrated that species tended to co-occur more frequently within their taxonomic groups (i.e., within charophytes and within angiosperms) than between these groups. The most extensive distribution overlap was observed between Chara aspera Willd. and Chara canescens Loisel., while Zostera marina L. exhibited the least overlap with the other species. The mean number of co-occurring species was the highest in Chara baltica (Hartman) Bruzelius while Z. marina had the largest share of single-species occurrences. Based on the distribution models, Stuckenia pectinata (L.) Börner had the largest distribution area.

Modifications in submerged aquatic vegetation (SAV) spatial and temporal abundance patterns indicate changes in marine environmental conditions or physical disturbances and need to be monitored. Vegetation percent cover (%cover) is recognized as one of the key parameters in SAV monitoring. Coastal waters of the Baltic Sea are often turbid and contain high amount of colored dissolved organic matter. These factors significantly reduce the water depth, where benthic parameters can be detected by remote sensing. Field campaigns were carried out in a low-transparency P & auml;rnu Bay area to assess to what extent multispectral Sentinel-2 (S2) satellite can be used for SAV %cover mapping in such waters. An average depth restriction for S2 benthic vegetation detection remained near 1.5 to 2.0 m. Empirical and physics-based methods were applied to S2 imagery to compare their performance for SAV %cover retrieval. Both methods identified similar %cover patterns. Model validation results showed that R-2 of the best-performing models remained between 0.56 and 0.66 and root-mean-square error between 22.11 and 28.06. As physics-based inversion models do not require extensive set of training data for model calibration, those can be used for retrospective time series analysis across multitemporal images.(c) 2023 Society of Photo-Optical Instrumentation Engineers (SPIE

increasing trend of littering of coastal areas and marine environment is recognized globally.in the european union, 80-85% of marine litter is plastic, among which single-use plastic (sup) products represent 50%. the study confirmed that the primary source of sup items on urban beaches of tallinn, estonia, is direct littering by beach visitors.the level of littering is highly dependent on the intensity of beach use. in total, 1492 macrolitter items per 100 m of beach length were registered at urban beach russalka, while remarkably lower values were registered at semi-urban beach Kakumäe. the most frequently found sup items at urban beach were cigarette butts, followed by various packages and sweet wrappers.to assess how quickly the fragmentation of selected sup products takes place in the natural environment, field experiments were carried out.the degradation of disposable paper plates, biodegradable plates and biodegradable waste bags was studied in two terrestrial (open-air vs. buried in soil) and two marine (submerged in seawater above sediment vs. buried in sediment) treatments.the experiment showed that the degradation of biodegradable sup items is limited in natural environment and varied depending on the character of the material of the product and the environment it was exposed to. the studied biodegradable plates had the fastest degradation rate (4 months) and the loss of material was the highest during the first months.in open-air conditions, the degradation process was the slowest.for the biodegradable plastic bags, noticeable decomposition took place only in the seawater above sediment; in other environments, the degradation was slower.therefore, to decrease the impact of plastic, instead of using biodegradable material, the guidance of consumers toward reducing, reusing and recycling of plastic should be promoted.