Marine environmental research最新文献

Current projections of rising sea surface temperatures (SST) pose a threat to marine macroalgae, particularly those living in shallow coastal areas. The giant Irish moss, a unique strain of the common red alga Chondrus crispus, is found solely in a coastal lagoon in Prince Edward Island, Atlantic Canada, and has undergone a two-decade population decline. Despite protection efforts, this alga has not recovered to its pre-decline abundance, which may be due to, among other factors, warming ocean temperatures. This study used laboratory experiments to examine the effects of a range of temperatures, either as steady or discrete temperature spikes, on algal fronds' weight and surface area. The results from both types of experiments were congruent and supported the notion that temperatures in the upper range of those currently occurring or predicted to occur, cause the worst losses in weight and surface area. Forecasted increases in SSTs leave the giant Irish moss vulnerable to further population declines and represent a concern for the long-term sustainability of this unique strain of Irish moss.

Mixotrophic dinoflagellates frequently cause harmful algal blooms (HABs) in eutrophic waters that contain diverse dissolved organic matter (DOM), especially intensive mariculture areas. Compared to the extensive investigation of phagotrophy and single organic molecule uptake by causative species, we have limited knowledge about the capability of mixotrophic dinoflagellates to utilize in-situ DOM in mariculture waters and its contribution to HABs. Here we use filtered in-situ mariculture water as the sole medium to examine the physiological response of Prorocentrum donghaiense to the natural mariculture DOM. Our results showed an 87.2% increase in the cell growth rate, as well as photosynthesis (16.8%-29.2%) and cellular chlorophyll a (32.4%-70.7%) when cultured with DOM compared to those grown in the inorganic medium. Meanwhile, cellular stoichiometry varied greatly among the groups supplied with mariculture DOM of different seasons, and the ecological implications were then discussed. Additionally, parallel cultures revealed the phycosphere bacterioplankton community compete with the algae cell regarding the nutrient utilization. This study quantifies the efficient utilization of in-situ mariculture DOM by P. donghaiense and indicates its vital role in sustaining HAB events and great effects on the biogeochemical cycle.

The recent decline in the health status of deep-sea habitats around the world has pushed the need to document and map their distribution to preserve them in their marine ecosystems. This work describes deep-water coral habitats (133-729 m) and their associated communities, based on nine ROV video transects. These transects cover a 171 km sub-seafloor profile within a predefined 5560 km² area along the North Atlantic coast of Morocco, surveyed in 2020 as part of a coral habitat mapping study under the FAO-NANSEN programme. The nine sites were initially explored using multibeam echosounder, to generate a detailed bathymetry map allowing for the positioning of video transects. Megafauna and sediment composition was recorded along transects, and in total 1854 individuals were annotated, and 59 taxa were identified. To identify coral communities and related species assemblages, we used a cluster analysis for classification and the ordination analysis Detrended Correspondence Analysis (DCA) to identify the environmental drivers behind the community patterns. Eight environmental variables were compared with the DCA ordination results, and the important variables were bedrock, mud and depth. The results revealed six megabenthic communities. Three groups were associated with soft sediments, mainly mud. Group I, at depths of 605-726 m, was characterized by Ceriantharia and Synaphobranchus kaupii. Group V, at 133 m depth, was dominated by Ceriantharia. Group VI, consisting of Centrostephanus sp. and a fish community (Scorpaenidae, Capros aper, and Macroramphosus sp.), was found at 201 m depth. In mixed bottoms, where mud is the dominant substrate, Group II was characterized by Crinoidea and sea pens (Funiculina quadrangularis and Virgularia mirabilis) at a depth range of 207-369 m, while Group III, found at depths of 465-602 m, was characterized by sea pens (Pennatula phosphorea and Funiculina quadrangularis), Crinoidea, and the key species Isidella elongata. Group IV, at 207 m depth, was represented by Sertularella sp. and Ellisella paraplexauroides as the dominant species. This first study about mapping deep sea coral habitats in the North Atlantic coast of Morocco reveals the identification of different habitats and new species. It contributes to Strengthen Science for Conservation and Sustainable Management of Deep-Water Corals in Morocco.

The composition of marine mammal blubber is influenced by factors such as diet and environmental conditions. Here, we investigate the thermal influence on fatty acid composition and degree of unsaturation in the blubber of 151 South American sea lions (Otaria byronia). Samples were collected at ten locations along the Chilean coast and spanned a latitudinal range of approximately 2500 km, an arc of 23°. We found a significant latitudinal gradient in the biochemical composition of sea lion blubber. At higher colder latitudes the endogenous fatty acids in the blubber were more unsaturated, as indicated by the desaturation index. In cold conditions the modification of fatty acids from saturated to unsaturated improves fluidity of cell membranes, which is important for thermal insulation. Thus, the higher degree of unsaturated endogenous fatty acids at higher latitudes may help sea lions maintain thermal balance in colder environments. For the dietary-sourced fatty acids however, we found the opposite latitudinal pattern, here the overall degree of unsaturation decreases with latitude. The lower proportion of polyunsaturated fatty acids in blubber at higher latitudes may be influenced by the sea lion's dietary choices. Additionally, the presence of extremely high levels of 18:2n-6 in some sea lions south of 40°S, values more typical of terrestrial origin, suggests they consumed farmed salmon. The observed variation in fatty acid profiles across the latitudinal gradient implies that differences in fatty acid composition are not solely attributed to dietary variation, but potentially also to endogenous metabolism in response to environmental conditions.

Upwelling, as a large oceanographic phenomenon, increases coastal productivity and influences all levels of biological complexity. Despite decades of research on it, much remains to be understood about the impact of upwelling on the feeding behavior and thermal tolerance of important groups such as fish. Hence, our aim was to investigate how upwelling conditions modify the feeding behavior and thermal tolerance of a prominent intertidal fish, Girella laevifrons. We collected purple mussels (Perumytilus purpuratus) from upwelling (U) and downwelling sites (DU) in central Chile, and used them as prey in feeding trials and measuring the concentration of organic matter and proteins in their tissues. We assessed fish consumption rates and growth in fish collected from the same U and DU sites, feeding on either U or DU mussels. Lastly, we assessed the thermal tolerance of U and DU fish fed with the aforementioned U vs DU mussels. We found that U mussels held higher concentrations of organic matter and proteins compared to their DU counterparts. U mussels were also selected and consumed in larger amounts than DU mussels, although the origin of the fish also influenced consumption rates. Thermal tolerance assays revealed that U fish exhibited higher maximum performance (Max.pf) and critical thermal maxima (Ct_max) and lower sensitivity to temperature changes (as measured by Q₁₀), compared to DU fish. Altogether, these results point to a strong influence of upwelling on the quality of organisms' tissues, indirectly altering key aspects of fish feeding behavior and thermal tolerance. These findings also contribute to understanding the physiological adjustments organisms make in productive upwelling systems, and how they may change in the future with ongoing climate events.

Shellfish and seaweed, the primary mariculture species in China, generate significant amounts of dissolved organic matter (DOM) during growth. This production significantly influences the carbon cycle in the marine environment. In the present study, we evaluated the DOM changes during growth in both seawater and sediments in Nan'ao, Guangdong Province, southern China. The results showed that both shellfish and seaweed growth increased organic carbon content in seawater and sediments. DOM and water-extractable organic matter in the seaweed cultivation area exhibited greater aromaticity and hydrophobicity, indicating that seaweed-produced organic matter is more difficult to decompose and resistant to consumption. This implies a potential to expand the refractory dissolved organic carbon (RDOC) pool in the marine environment. We also estimated carbon removal and carbon sequestration by shellfish and seaweed culture in Guangdong Province from 2012 to 2021. Average carbon removal by shellfish cultivation is at 227.81 Gg C yr^-1, and the release of carbon is at 205.71 Gg C yr^-1. Carbon removal by seaweed cultivation is at 22.95 Gg C yr^-1 with carbon sequestration of 11.89 Gg C yr^-1. Compared with shellfish, seaweed has a large carbon sequestration potential. The integrated aquaculture of shellfish and seaweed in adjacent areas, given the environmental and socioeconomic benefits of absorbing nitrogen and phosphorus nutrients, mitigating eutrophication, and ocean acidification, is advisable for coastal developing countries to promote shellfish-seaweed farming.

Nutrients are critical in assessing water quality, so understanding their distribution and variability is essential for effective marine environmental protection. This study focuses on the Yangtze River estuary and surrounding waters, where suspended solids show a strong correlation with active phosphates and silicates. Using GOCI imagery and measured nutrient concentrations, such as active phosphate and silicate, remote sensing models were developed to investigate the seasonal and daily changes in surface water nutrients. The results showed the following key findings: Temporally, active phosphate (PO₄-P) and silicate (SiO₃-Si) concentrations exhibited distinct seasonal patterns, with the highest values observed in winter (1.692 μmol/L and 16.386 μmol/L, respectively) and the lowest in summer (0.503 μmol/L and 10.645 μmol/L, respectively). Little difference was found between spring and autumn. Spatially, elevated phosphate and silicate concentrations were found near the northern Jiangsu Shoal, the Yangtze River estuary, and Hangzhou Bay, and decreased towards the outer coastal waters. This suggests that the freshwater inflow from the Yangtze River is an important driver of the observed nutrient patterns. Diurnal variations in phosphate and silicate concentrations were observed in the surface waters of the Yangtze River estuary and adjacent areas. Significant diurnal variations in nutrient concentrations were observed in Hangzhou Bay, the northern part of the Yangtze River estuary and the southern part of the Yangtze River estuary. Slight diurnal variations were observed in the inland channels of the estuary. These results help to facilitate the study of the complex process of spatial and temporal dynamics of nutrients in the coastal waters of eastern China.

The impacts of glacial retreat on diets of ascidians, one of the filter feeders and a major component of the benthic-pelagic energy pathway, remain unclear. We analyzed carbon and nitrogen stable isotopes of four dominant ascidian species and five potential food sources in Marian Cove, a deglaciating fjord in West Antarctica. Microphytobenthos was a major food source for ascidians regardless of proximity to the glacier, but phytoplankton contribution decreased closer to the glacier. Particularly near the glacier, microphytobenthos formed visible bushes on the surface of ascidians providing an easily accessible potential food source. The diet of Molgula pedunculata changed with spatial variations in food sources influenced by glaciers, whereas Cnemidocarpa verrucosa, which exhibits a squirting behavior, showed a consistent diet primarily contributed by microphytobenthos regardless of glacial impact. These results provide necessary information for understanding the impact of climate change-induced glacial retreat on the diet of ascidians, a dominant taxon in the Antarctic coast.

Research on the occurrence and seasonal monitoring of pharmaceutically active compounds (PhACs) in estuarine and coastal waters has intensified recently. However, few studies have been conducted with PhACs flowing into the marine waters of South America (such as Brazil). Against this backdrop, the aims of this study were: (i) evaluate, for the first time, the seasonal occurrence throughout a year and the potential ecological risks of ten selected PhACs in marine bathing waters from Santos Bay, São Paulo, Brazil (a tropical low-wave energy semi-closed bay); and (ii) develop a list of high-priority PhACs for the monitoring based on "occurrence, persistence, bioaccumulation, and toxicity" criteria (OPBT). Four water sampling campaigns were carried out throughout the four seasons of the year. The results showed that: (i) ten PhACs (namely, caffeine/CAF (87.20-567.23 ng/L); carbamazepine/CAR [below the limit of quantification ( ACE > DIC and CAR to algae, crustaceans, and fishes; (iv) Finally, regarding the OPBT ranking, the DIC was the highest-priority PhAC in Santos Bay, followed by: ORP > LOS > CIT > CAR > FUR > ATE > CAF > ACE > ENA.