Our understanding of global seagrass ecosystems comes largely from regions characterized by human impacts with limited data from habitats defined as notionally pristine. Seagrass assessments also largely focus on shallow-water coastal habitats with comparatively few studies on offshore deep-water seagrasses. We satellite tracked green turtles (Chelonia mydas), which are known to forage on seagrasses, to a remote, pristine deep-water environment in the Western Indian Ocean, the Great Chagos Bank, which lies in the heart of one of the world's largest marine protected areas (MPAs). Subsequently we used in-situ SCUBA and baited video surveys to survey the day-time sites occupied by turtles and discovered extensive monospecific seagrass meadows of Thalassodendron ciliatum. At three sites that extended over 128 km, mean seagrass cover was 74% (mean range 67–88% across the 3 sites at depths to 29 m. The mean species richness of fish in seagrass meadows was 11 species per site (mean range 8–14 across the 3 sites). High fish abundance (e.g. Siganus sutor: mean MaxN.site−1 = 38.0, SD = 53.7, n = 5) and large predatory shark (Carcharhinus amblyrhynchos) (mean MaxN.site−1 = 1.5, SD = 0.4, n = 5) were recorded at all sites. Such observations of seagrass meadows with large top predators, are limited in the literature. Given that the Great Chagos Bank extends over approximately 12,500 km2 and many other large deep submerged banks exist across the world's oceans, our results suggest that deep-water seagrass may be far more abundant than previously suspected.

Two fuel oils and two crude oils were subjected to a 60-day weathering simulation experiment, and the effects of weathering on some common parameters for aromatics and aromatic δ¹³C values were studied. The results show that weathering of all oil samples affected little the DBT/P (dibenzothiophene/phenanthrene) ratio and methylphenanthrene distribution fraction. Four oil samples could be distinguished only by the DBT/P ratio. The effect of weathering on isotopes in polycyclic aromatic hydrocarbons was small. The results show that the types of four oil samples can be distinguished, while Kuwait and Russia crude oils cannot be discriminated from each other totally by double-coordinate two-dimensional maps for aromatic δ¹³C; all of the oil samples can be distinguished by principal component analysis of δ¹³C for aromatics, the relationship of DBT/P and PAHs δ¹³C values. Therefore, the δ¹³C value of aromatics can be used as an alternative index for the analysis of oil spills.

There is a substantial need for tools that effectively predict spatial and temporal fecal pollution patterns in estuarine waters. In this study, statistical models of exceedances of shellfish fecal coliform (FC) water quality criteria were developed using a 10-year dataset of FC levels and environmental data. Performance (sensitivity, specificity, and predictive capacity) of five different types of models was tested (MLR regression, Tobit (censored) regression, Firth's binary logistic regression (BLR), classification trees, and mixed-effects regression) for each of three conditionally managed shellfish-harvesting areas in Tillamook Bay, Oregon (USA). The most influential variables were related to precipitation and river stage height in the wet season and wind and tidal-stage in the dry season. Classification tree and Firth's BLR approaches better explained exceedances of shellfish water quality standards than the current closure thresholds. Findings demonstrate the utility of statistical modeling approaches for improved management of shellfish harvesting waters.

We determined the abundance and virulence of Vibrio parahaemolyticus in seawater and bivalves from the Gyeongnam coast in Korea, a major area for the seafood industry, during 2004–2016. V. parahaemolyticus is one of the most common pathogen causing seafood-borne illnesses in Korea, and increases during the summer. Its occurrence in seawater and bivalve samples was seasonally dependent, with high levels during the summer to early autumn. There were more strains in the area of sea continually exposed to inland wastewater. Only 5.1% and 3.5% of V. parahaemolyticus isolates from seawater and bivalves, respectively, had the trh gene, and only the bivalve isolates produced the tdh gene at levels below 2%. Continuous monitoring is clearly needed to reduce seafood-borne outbreaks of disease caused by V. parahaemolyticus, and to reveal the occurrence patterns and the presence of toxic genes of the strains in different marine environments.

The present work deals with assessment of baseline radionuclide concentration in marine organisms around selected coasts of Maharashtra, India. This baseline study highlights concentrations of natural and fallout radionuclides in finfish and shellfish species found in the surrounding seawater. Water and fish samples were collected, processed, and analyzed for 238U, 226Ra, 228Ra, 232Th, 40K, and 137Cs by high-resolution gamma spectrometry. 238U, 226Ra, 228Ra, 232Th, 40K, and 137Cs concentrations were found to be in the range of ≤1.5, ≤2.0, ≤0.4, ≤1.5, ≤8.0 to 258, and ≤0.2 Bq/kg, respectively. The seasonal study revealed the maximum concentration in premonsoon season. Activity concentrations were higher in pelagic fish than those in demersal fish. A higher concentration factor was reported in shellfish than in finfish.

Based on concentrations and distributions of heavy metals, grain size and loss on ignition (LOI) in the seafloor sediments acquired during three surveys in winter and in summer (before and after typhoon Morakot) in the mud deposition center off the Fujian-Zhejiang coast, East China Sea, the seasonal and typhoon-induced variations of heavy metals in seafloor sediments are discussed. It is found that different concentrations of heavy metals occurred in seafloor sediments, but their distribution patterns were similar, gradually decreasing from near-shore to offshore. The distribution of heavy metals was correlated with grain size and LOI in seafloor sediments, which showed significant seasonal variations and typhoon's impact. Based on these results, a conceptual evolution model was built about the seasonal and typhoon's impact on the deposition environment of heavy metals, which has implications for understanding the migration, settling, and burial processes of heavy metals in the sea.

Prorocentrum donghaiense is an important dinoflagellate as it frequently forms harmful algal blooms that cause serious damage to marine ecosystems and fisheries in the coast of East China Sea. Previous studies showed that phosphorus acquisition (especially inorganic phosphorus) was the limiting factor for P. donghaiense growth. However, the responsive mechanism of this microalga under dissolved inorganic phosphorus (DIP) limitation is poorly understood. In this work, the physiological parameters and differentially expressed genes in P. donghaiense response to DIP limitation were comparatively analyzed. DIP-depleted P. donghaiense displayed decreased growth rate, enlarged cell size, decreased cellular phosphorus content, and high AP activities. A forward suppression subtractive hybridization (SSH) library representing differentially upregulated genes in P. donghaiense under DIP-depleted conditions was constructed, and 134 ESTs were finally identified, with a significant identity (E values<1×10−4) to the deposited genes (proteins) in the corresponding databases. Five representative genes, namely, NAD-dependent deacetylase, phosphoglycolate phosphatase, heat shock protein (HSP) 90, rhodopsin, and HSP40 were investigated through real-time quantitative PCR to verify the effectiveness of the established SSH library. Results showed that all the selected genes were differentially expressed and thus indicated that the established SSH library generally represented differentially expressed genes. These genes were classified into 11 categories according to their gene ontology annotations of biological processes. The members involved in functional responses such as cell defense/homeostasis, phosphorus metabolism, and cellular cycles were specially discussed. This study is the first to perform a global analysis of differentially expressed functional genes in P. donghaiense under DIP-depleted condition. It provided new insights into the molecular adaptive mechanisms of dinoflagellate in response to phosphorous limitation and elucidating the formation mechanism of algal blooms.

Plastic is produced today in large quantities and used for many purposes. At the end of use, a large part of it gets into the environment, often into the sea and there it is fragmented into the smallest fragments, so-called microplastic (MP). MPs pose a serious challenge to the marine environment such as the sources and properties of MP particles, their impact on marine organisms, and the challenges of environmental pollution. This work, carried out in the fourteen sites in the area, is the first reference to the detection of MP distribution at surface waters in the Sea of Marmara, Turkey. As a result of this study, the average level of MP in the surface was determined to be 1.263 item/m2. The results were higher compared of the most other adjacent regions and show that the Sea of Marmara started to face that problem.

Chemical pollution of the marine environment from anthropogenic sources is a global concern due to the potential for long term effects on the ecosystem. Chemical monitoring schemes can detect harmful substances in water, sediment or biota. However, the presence of specific determinants gives no information on how individual species or the ecosystem are impacted. Biological effects techniques are therefore used in environmental monitoring schemes to provide a clearer picture of whether the chemicals present are causing deleterious effects on the species sampled, or whether organisms have been exposed to certain classes of organic contaminants that they may be able to metabolise. Using these techniques, we can provide an assessment of the health of our marine environment (Thain et al., 2008).

Seagrass meadows suffered large-scale declines in the past century. The ‘wasting disease’, pathognomonically associated with Labyrinthula zosterae, reduced populations of Zostera marina on both sides of the North Atlantic in, and since, the 1930s, coinciding with intensive agricultural use of artificial fertilizers and herbicides. This study tests the long-standing hypothesis that nutrient enrichment and a herbicide increases vulnerability to pathogens.Z. marina shoots from the Thames Estuary grown in elevated nitrate concentrations had significantly higher rates of infection by L. zosterae than controls, but not by Aplanochytrium sp., another slime-mould like protist. Z. marina shoots grown in 2μg·l−1 Diuron solutions and infected separately by L. zosterae and Aplanochytrium sp. had significantly higher wasting indices than controls. The results identified Aplanochytrium sp. as another opportunistic pathogen causing a seagrass wasting-type disease and support the hypothesis that pollution by herbicides and nitrate increases the susceptibility of Z. marina to infections.