EA EcolDur | International audience

An annual investigation on the seasonal changes of benthic community structure associated with Amphioxus Sand was conducted at two sites in the eastern waters of subtropical Hong Kong, where three species of amphioxus, Branchiostoma belcheri, B. japonicum and B. malayanum coexist. A total of 84 species and 4169 individuals were recorded at Tai Long Wan, whereas a total of 87 species and 3915 individuals were recorded at Pak Lap Wan. Benthic polychaetes were dominant, including high abundance of Onuphis eremita and Prionospio malmgreni. Results of cluster analysis showed significant community structures between the two areas because of difference in sediment granulometry. However, temporal changes within these Amphioxus Sand communities were minimal. In general, the Amphioxus Sand communities in Hong Kong showed higher species richness of Polychaeta as compared with similar studies elsewhere, possibly implying an increased level of organic pollution in Hong Kong waters.

Plastic marine debris is presently widely recognised as an important environmental pollutant. Such debris is reported in every habitat of the oceans, from urban tourist beaches to remote islands and from the ocean surface to submarine canyons, and is found buried and deposited on sandy and cobble beaches. Plastic marine debris varies from micrometres to several metres in length and is potentially ingested by animals of every level of the marine food web. Here, we show that synthetic polymers are present in subsurface plankton samples around Saint Peter and Saint Paul Archipelago in the Equatorial Atlantic Ocean. To explain the distribution of microplastics around the Archipelago, we proposed a generalised linear model (GLM) that suggests the existence of an outward gradient of mean plastic-particle densities. Plastic items can be autochthonous or transported over large oceanic distances. One probable source is the small but persistent fishing fleet using the area.

The exponential decay of the amount of new litter on Wadahama Beach, Nii-jima Island, Japan revealed by 20-month mark-recapture experiments demonstrates a linear response of the beach to the input of target items. Here we show the amplitude and phase characteristics of the beach as a time-invariant linear input/output system and discuss the hydrodynamic and geomorphological factors that would determine the characteristics with the aid of a diffusion equation. The characteristics are fully determined by the residence time of the items (τr=209days) and can be described as functions of the ratio of τr to the period of input variability. The decay is reproduced well by the analytical solution of the equation with a constant diffusion coefficient (D), whose order was estimated by τr and the backshore width. Generally, D would depend on hydrodynamical statistics and beach geomorphology as well as the dimensions and density of the items.

Thirty-five surface sediment samples collected from Beibu Gulf and its tributary rivers, China were analyzed for DDTs, HCHs and chlordanes. Total concentrations of DDTs, HCHs and chlordanes in sediments ranged from 0.59 to 126ngg−1, ND to 2.65ngg−1 and 0.27 to 3.41ngg−1 based on dry weight (dw), respectively. Concentrations of DDTs were higher than those reported in the sediments from other regions of the world, while concentrations of HCHs and chlordanes were relatively low. High concentrations of DDTs were observed in the harbor region and aquaculture bases and high concentrations of HCHs were found in the Qin River Estuary. The ratios of (DDE+DDD)/DDTs reflected a mixed input of weathered and fresh DDTs. The predominant β-HCH indicated that HCHs in the study area mainly originated from the historical usage of technical HCH. The residues of DDTs would pose adverse biological effects on the study area.

Eggs from egrets (Egretta thula) were collected from Cartagena Bay and Totumo Marsh, two sites at the north of Colombia with different pollution background, and measured their morphometric parameters as well as total mercury (T-Hg) and calcium levels in eggshell. Statistically significant differences were observed for egg weight and size between the two sampling locations. T-Hg and calcium concentrations in eggshell were greater in eggs from Cartagena Bay, the industrial site, compared to Totumo Marsh, a non-industrial location. The opposite was observed for eggshell thickness (3.6% less in the bay). Pearson correlation analysis showed eggshell T-Hg negatively correlated with eggshell weight in eggs from the marsh (R=−0.795, P<0.006), but not from the bay (R=0.387, P=0.269), probably suggesting greater susceptibility to Hg in birds from the non-polluted site. In short, results suggest eggs from E. thula at Cartagena Bay have greater T-Hg concentrations and less eggshell thickness than those from Totumo Marsh.

Plastic marine debris affects species on most trophic levels, including pelagic fish. While plastic debris ingestion has been investigated in planktivorous fish in the North Pacific Ocean, little knowledge exists on piscivorous fish. The objectives of this study were to determine the frequency of occurrence and the composition of ingested plastic marine debris in longnose lancetfish (Alepisaurus ferox), a piscivorous fish species captured in the Hawaii-based pelagic longline fishery. Nearly a quarter (47 of 192) of A. ferox sampled contained plastic marine debris, primarily in the form of plastic fragments (51.9%). No relationship existed between size (silhouette area) or amount of plastic marine debris ingested and morphometrics of A. ferox. Although A. ferox are not consumed by humans, they are common prey for fish commercially harvested for human consumption. Further research is needed to determine residence time of ingested plastic marine debris and behavior of toxins associated with plastic debris.

A three dimensional rectangular grid model is applied to resolve the temperature–salinity dynamics of Ruwais, a segment of the UAE coast which is well known as dense water formation zone. The model employs a heat flux module and a turbulence closure scheme that facilitate realistic calculation of temperature–salinity dynamics. A field survey campaign is carried out to support the modeling study, involving measurements of tide, currents, temperature, and salinity. Investigation is done for two meteorologically extreme conditions, i.e. summer and winter. The model study showed that the western flux develops an anticlockwise circulation in the study area. The water industrial discharges elevated the temperature and salinity of the water near the southeastern shoreline. This water mass propagated towards north under the influence of gravity.

The distribution of Ruppia cirrhosa meadow density and its epiphytic organisms in relation with environmental factors were studied in summer 2011 at five stations in the Ghar El Melh lagoon (GML; southern Mediterranean Sea). Eleven epiphytic groups were recognised among which diatoms and dinoflagellates were the dominant groups and greatest contributors to temporal dissimilarity. An overwhelming concentrations of harmful microalgae was recorded, mainly represented by the toxic dinoflagellate Prorocentrum lima with maximal concentrations attaining 6×105cells 100g−1 of Ruppia fresh weight. The epifauna community accounted for only 1.4% of total epiphyte abundance and was comprised predominantly of nematodes (47.51%), ciliates (32.59%), fish eggs (7.2%) and larvae (4.95%). PERMANOVA analyses revealed a significant spatio-temporal variation of all epiphytic groups (p<0.01). In this study, R. cirrhosa and its epiphytes were studied as potential early warning indicators of the health status of GML waters.

Surface sediments from marine reserves of the Tuscan Archipelago National Park (Italy), including remote islands not directly affected by anthropogenic influences, were analyzed for two dominant perfluorinated compounds (PFCs), namely perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), using LC–ESI-MS/MS. The concentrations of PFOS were low, with medians ranging from 0.25 to 1.50ng/g dry wt, whereas PFOA was always below the detection limit of 0.1ng/g dry wt. The present paper can be considered a baseline study useful in future environmental monitoring programs.