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.

Pharmaceuticals are common chemical contaminants in estuaries receiving effluent from wastewater and sewage treatment facilities. The purpose of this research was to examine benthic microalgal (BMA) community responses to sublethal exposures to tylosin, a common and environmentally persistent antibiotic. Bioassays, using concentrations of 0.011–218μmoltylosinl−1, were performed on intertidal muddy sediments from North Inlet Estuary, SC. Exposure to tylosin resulted in a reduction in total BMA biomass and primary productivity. Furthermore, exposure seemed to retard diatom growth while having a minimal effect on cyanobacteria biomass. Estuarine systems receiving chronic inputs of trace concentrations of tylosin, as well as other antibiotics, may experience significant reductions in BMA biomass and primary productivity. Given the well-documented role of BMA in the trophodynamics of estuaries, these impacts will likely be manifested in higher trophic levels with possible impairments of the structure and function of these sensitive systems.

Six cruises were conducted in a fish farm adjacent to the Ninghai Power Plant in Xiangshan Bay, East China Sea. Fish farming significantly increased NH4+, DIP, and TOC concentrations, while it significantly decreased the DO level. These increase/decrease trends were more pronounced in warmer seasons. Although culture practices did not significantly increase phytoplankton density, it drastically enhanced dinoflagellate abundance and domination. Significant differences in species diversity and community composition between the cages and the control area were also observed. Temperature elevation caused by thermal discharge associated with eutrophication resulted in a dominant species shift from diatoms alone to dinoflagellates and diatoms. This is the first report of stress-induced toxic dinoflagellate (Prorocentrum minimum) blooms in winter and the winter–spring transition in this bay. Therefore, the effects of aquaculture activity and power plant construction in such a eutrophic, semi-enclosed bay require further attention.

Metals and biogenic elements were analyzed from surface sediments collected from Zhelin Bay in the South China Sea in December 2008. The high concentrations of TOC, TN and BSi indicate the high nutrient level and diatom productivity in Zhelin Bay. The concentrations of metals were generally far lower than the effects-range-low (ERL) values that define pollutant levels. Enrichment factors (EF) and geoaccumulation indices (Igeo) suggest there are pollution levels of Cd, Cu and Zn at some stations. As, Cu, and Pb are potentially biotoxic in some stations. Correlation and principal component analyses indicate that most of the metals primarily originate from natural sources, and from maricultural activities as well. Mariculture contributes considerable Cd and Cu contamination. As and Pb comes primarily from combustion of gasoline and diesel fuel by ships.

Diatoms have been regularly used as bioindicators to assess water quality of surface waters. However, diatom-based indices developed for a specific geographic region may not be appropriate elsewhere. We sampled benthic diatom assemblages in the upper Han River, a subtropical river in China, to evaluate applicability of 14 diatom-based indices used worldwide for water quality assessment. A total of 194 taxa from 31 genera were identified in the dry season and 139 taxa from 23 genera in the wet season. During the dry season, significant relationships were found for all but one of the diatom-based indices (Index Diatom Artois–Picardie) with one or more physical and chemical variables including nutrients and ion concentrations in river waters. The Biological Diatom Index (IBD) and diatom-based eutrophication/pollution index (EPI-D) were strongly related to trophic status and ionic content, while Watanabe’s Index was related to organic pollution and conductivity. Yet, the diatom indices showed weak relationships with physical and chemical variables during the wet season. It suggests that diatom-based indices developed in Europe can be applied with confidence as bioindicators of water quality in subtropical rivers of China, at least during base-flow conditions.