Comparing sea otter recovery in California (CA) and British Columbia (BC) reveals key ecosystem properties that shape top-down effects in seagrass communities. We review potential ecosystem drivers of sea otter foraging in CA and BC seagrass beds, including the role of coastline complexity and environmental stress on sea otter effects. In BC, we find greater species richness across seagrass trophic assemblages. Furthermore, Cancer spp. crabs, an important link in the seagrass trophic cascade observed in CA, are less common. Additionally, the more recent reintroduction of sea otters, more complex coastline, and reduced environmental stress in BC seagrass habitats supports the hypotheses that sea otter foraging pressure is currently reduced there. In order to manage the ecosystem features that lead to regional differences in top predator effects in seagrass communities, we review our findings, their spatial and temporal constraints, and present a social-ecological framework for future research.

As a consequence of industrialization, urbanization, and population growth in the past decades, high nutrient concentrations from point and non-point sources in aquatic systems have caused major problems to the water quality in rivers, estuaries, and coastal waters. Although the nutrient pollution due to land use change cannot be ignored, the combined sewer overflows and discharging sites have been important point sources of nutrient pollution. Integrated hydrodynamic, chemical, and biological models developed in recent years, which simulate the nutrient transportation from both point and non-point sources, are useful tools to assist in identifying the transport and fate of nutrients from both point and non-point sources. In this paper, water quality data from published literature were reviewed and analyzed to evaluate nutrient (N and P) pollution in aquatic systems. An integrated monitoring and management plan should be continuously developed in the future to monitor and regulate nutrient discharges from point and non-point sources.

High-risk contaminants, OCPs and PCBs, were investigated in marine fish from the Adriatic Sea, from which retail fish in Croatia is commonly sourced. The pollutant levels in sardine, horse and chub mackerel, anchovy and round sardinella were analysed based on a two-year sampling and the joint use of generally accepted statistics and advanced clustering methods − self-organizing maps (SOM) and decision tree analysis (DT). Both the SOM and DT suggested fish mass and length rather than fat along with α-HCH, p,p′-DDT, PCB-74 and PCB-189 to cause variable pollutant uptake among species. Main distinctions of sardines occur in coastal and off coast regions rather than in a particular fishing zone and they are associated with both fish characteristics, levels of γ-HCH and PCBs: −60, −105, −150, −170, and −189. The results, mutually compatible or in agreement, could be useful for the design and implementation of the abatement strategies of fish pollution.

Investigations of total petroleum hydrocarbons (TPHs) in water and polycyclic aromatic hydrocarbons (PAHs) in sediments were performed in the entrance and the exit of the Turkish Straits System (TSS) in autumn of 2016 and spring of 2017. TPH and PAH values ranged from 1.7 to 11.6 μg/l and 120 to 2912 ng/g (dw), respectively. On the basis of the given surface fluxes of the TSS, average petroleum flows were calculated as 1631 t/y from the Black Sea to the Marmara Sea and 8484 t/y from the Marmara Sea to the Aegean Sea. Pollution by PAHs ranged from relatively moderate to high. The most polluted sediments were collected from regions affected by shipping, such as Riva and Seddülbahir located at the entrance and the exit of the TSS, respectively. Moreover, origins of PAHs were determined using the ratios of PAH congeners. The main origins of PAHs were found as both pyrolytic and petrogenic at most stations.

This study provides a baseline assessment of cadmium, copper, iron, manganese, lead, and zinc concentrations in muscles, gills, and exoskeleton of the Lessepsian blue swimming crab Portunus segnis captured in the Gulf of Gabès (Southern Mediterranean Sea, Tunisia) in November 2015. Furthermore, the species' trophic position is estimated using CN stable isotope analysis. The exoskeleton showed the lowest metal contents; in soft tissues, the essential Cu, Fe, and Zn and the non-essential Cd, Mn, and Pb showed the highest and lowest concentrations, respectively. The crab was characterized by a trophic position of 3.32, confirming its carnivorous trophic habits. Compared with literature data on invertebrate and fish species from the same area, Cd and Pb resulted remarkably low in the crab's soft tissues, while a food web-scale dilution effect was indicated. The need of a comprehensive assessment of the ecological impact of Portunus segnis in invaded Mediterranean waters is discussed.

The aim of the present research was to determine the impact of intense rains and flooding on mercury riverine input to the coastal zone. This study focused on four small rivers (Reda, Zagórska Struga, Płutnica, Gizdepka), typical of the Southern Baltic region, with no significant mercury sources. Samples were collected for 16months during average flow conditions and during selected meteorological events: floods, downpours, thaws and droughts. Results showed decreased retention of mercury during intense rainfalls, thus demonstrating mercury elution from the catchment. Floods and melting snow also have a tremendous impact on the outflow of mercury from the catchment. Development of urban infrastructure and farmlands increases the outflow of mercury from the catchment too, making such areas a significant source of mercury in the river. On the other hand, areas with natural character, predominated by forests, stimulate retention of mercury that reaches them through dry and wet atmospheric deposition.

Researches on the functional diversity of benthic ecosystems have mainly focused on macrofauna, and studies on functional structure of ciliate communities have been based only on trophic- or size-groups. Current research was carried out on the changing patterns of classical and functional diversity of benthic ciliates in response to environmental gradients at three sites in a wetland in Yangtze Estuary. The results showed that changes of environmental factors (e.g. salinity, sediment grain size and hydrodynamic conditions) in the Yangtze Estuary induce variability in species composition and functional trait distribution. Furthermore, increased species richness and diversity did not lead to significant changes in functional diversity due to functional redundancy. However, salt water intrusion of Yangtze Estuary during the dry season could cause reduced functional diversity of ciliate communities. Current study provides the first insight into the functional diversity of ciliate communities in response to environmental gradients.

Bivalves use anti-oxidative enzyme systems to defend themselves against excessive reactive oxygen species, which are often catalyzed by environmental pollution. As a key member of anti-oxidative enzyme family, catalase plays a crucial role in scavenging the high level of reactive oxygen species to protect organisms against various oxidative stresses. In this study, a catalase homologue was identified from Mytilus coruscus (named McCAT, KX957929). The open reading frame of McCAT was 1844bp with a 5′ untranslated region of 341bp and a 3′ untranslated region of 927bp. The deduced amino acid sequence was 512 residues in length with theoretical pI/MW 8.02/57.91kDa. BLASTn and phylogenetic analyses strongly suggested that it was a member of catalase, also known as CAT family for its conserved catalytic site motif and proximal heme-ligand signature motif. Real-time fluorescence quantitative PCR showed that constitutive expression of McCAT was occurred, with increasing order in mantle, adductor, gill, hemocyte, gonad and hepatopancreas. It was observed that bacterial infection and heavy metals stimulation up-regulated McCAT mRNA expression in hepatopancreas with time-dependent manners. The maximum expression appeared at 8h after pathogenic bacteria injecting, with 15-fold in Vibrio parahemolyticus and 60-fold in Aeromonas hydrophila than that of 0h. The highest point of McCAT mRNA appeared at different times for exposure to heavy metals with copper at day 5 (0.1mg/L 30-fold, 0.5mg/L 15-fold, 1.5mg/L 6-fold) and plumbum at day 3 (3.0mg/L 20-fold). The enzymatic activity analysis found that McCAT activity in the gill of M. coruscus was affected by heavy metals concentration. The results suggested that McCAT plays a significant role in antioxidation and the expression of McCAT can be used as a biomarker for detection of marine environmental pollution.

The marine auxiliary diesel engines installed in the large transoceanic ships are used in order to generate the electricity but at the same time these engines are able to produce a significant amount of the harmful exhaust gas emissions. Therefore the International Maritime Organisation (IMO) concluded an agreement, which has to control generating of gaseous emissions in maritime transport. From this reason started to be used some of the alternative fuels in this branch. There was performed a study, which investigated emissions of the auxiliary marine diesel engine during application of the experimental fuels. The different testing fuels were created using the ratios 0%, 50%, 80% and 100% between the biodiesel and the ULSDF (Ultra Low Sulphur Diesel Fuel). The experimental measurements were performed at the different engine loading levels and various engine speeds in order to investigate an influence of the mixed fuels on the engine operational characteristics.

Wastewater treatment plant effluent introduces a mixture of pollutants into marine environments; however, the impacts of chronic sublethal exposures on populations are often unclear. Presence of estrogenic agents in sediments and uptake of these compounds by demersal flatfishes has been reported at the Orange County Sanitation District (OCSD) wastewater outfall. Furthermore, estrogenic activity has been identified in male flatfish in the area, potentially contributing to observed population declines in the OCSD region. Rising ocean temperatures may further contribute to flatfish declines as relationships between temperature and abundance have been reported in the Southern California Bight. To investigate declines, sex ratios, condition factor, organ health indices, hormones, and vitellogenin were quantified in flatfish collected at OCSD outfall and reference sites. Additionally, historical temperature data was examined for trends with population abundances. Rather than being linked to estrogenic activity, results indicated that population declines were more correlated to increases in ocean temperature.