We investigated food supply mechanisms to a cold-water coral (CWC) reef at 260 m depth on the Norwegian continental shelf using data from a cabled ocean observatory equipped with Acoustic Doppler Current Profilers (ADCPs), an echosounder, and sensors for chlorophyll, turbidity and hydrography in the benthic boundary layer (BBL). Tidal currents of up to tens of cm s−1 dominated BBL hydrodynamics while residual currents were weak (∼10 cm s−1), emphasizing a supply and high retention of locally produced phytodetritus within the trough. A direct connection between the reefs and surface organic matter (OM) was established by turbulent mixing and passive particle settling, but relative contributions varied seasonally. Fresh OM from a spring-bloom was quickly mixed into the BBL, but temperature stratification in summer reduced the surface-to-bottom connectivity and reduced the phytodetritus supply. A qualitative comparison among acoustic backscatter in the ADCPs (600 kHz, 190 kHz) and echosounder (70 kHz) suggests that vertically migrating zooplankton may present an alternative food source in summer. Nocturnal feeding by zooplankton in the upper water column sustains downward OM transport independent from water column mixing and may dominate as food supply pathway over sedimentation of the phytodetritus, especially during stratified conditions. In addition, it could present a concentrating mechanism for nutritional components as compensation for the deteriorating phytodetritus quality. Overall, the observed patterns suggest seasonal changes in the food supply pathways to the reef communities. The moderating role of temperature stratification in phytodetritus transport suggests stronger dependence of the cold-water corals on zooplankton for their dietary requirements with increased stratification under future climate scenarios. This study demonstrates the added value of permanent ocean observatories to research based on dedicated campaigns and regular monitoring.

The present paper reports on the results of a long-term field study on the simultaneous influence of 2 environmental factors (temperature and food supply) on annual growth rates in the tellinid bivalve Macoma balthica. For >30y (1978–2009) we monitored twice-annually the weight changes of soft parts of individuals of known age at several permanent sampling stations located at Balgzand, an extensive (50km2) tidal flat area in the western Dutch Wadden Sea. Monthly data were available on mean water temperature and chlorophyll a (chl a) concentration from a nearby site in the main tidal inlet. Mean individual ash-free dry weights at ages of nearly 1 and of nearly 1.5y were assessed in February/March and in August, respectively. Such weights show a consistent annual pattern: they increase between late winter and early summer to decline for the remainder of the year. Annual multi-station means of the spring/summer individual weight gains were higher as chl a concentrations in the water had been higher and water temperatures had been lower for the growing season. These correlations proved to be stronger at sampling sites that were situated low in the intertidal zone close to the main tidal stream than at those high in the intertidal near the coast (where M. balthica obtain their food primarily by deposit feeding on benthic material). At the low off-shore sites, suspended algae are available for longer daily periods and their concentrations in flood water may be less depleted by grazers. The negative correlation between weight gain and water temperature may have been primarily based on the shortening of the M. balthica growing seasons in warm summers. We conclude that the present simultaneous trends of global warming and declining stocks of pelagic algae may affect M. balthica in the Wadden Sea in a similar, negative, way.

Although a strong connection between the environmental fluoride contamination and the fluorosis disease is nowadays worldwide well documented, the knowledge on the fluoride contamination levels of cultivated crops at the basis of the human food-chain is limited and fragmented. Adopting a systematic approach, this study reviews the available literature concerning the impacts of soil and water fluoride pollution on the safety and productivity of food and feed crops at a global scale, with the aim to provide a comprehensive overview of the current state of the art. The analyses of literature highlighted that food and feed crops exposed to soil and water fluoride pollution may reach concentrations of fluoride potentially harmful to human health. Nevertheless, despite the efforts already made to assess the crop fluoride accumulation in contaminated areas of India and China, the present study brings to light the lack of knowledge still existing on this issue for some regions strongly affected by environmental fluoride contamination such as the East African Rift Valley. Concerning the impacts of fluoride on cultivated crops, many authors observed that fluoride can produce toxic effects on plants leading to oxidative stress, reduction in chlorophyll content, alterations in the levels of proline, betaine, soluble sugars, nitrogen and macro and micronutrients. However, the appearance of symptoms such as visible injuries, reduced root and shoot length and yield decline was not always observed, also at high levels of fluoride exposure, and in some cases, the biomass production was even stimulated by increasing fluoride doses.

Only a combination of nutrient load abatement and food-web management proved efficient for the management of water quality in the deep stratifying Wupper Reservoir. Reduction of nutrient loading, was completed in winter 1992/1993, but resulted only in reduced winter/spring mixing of phosphorus concentrations. Since the capacity of the diatom spring bloom to remove nutrients from the trophogenic layer of this slightly eutrophic water-body was never exhausted, the surplus of total phosphorus available to support summer algal growth remained unchanged. Thus, nutrient reduction alone did not improve the water quality, as expected. Subsequent replacement of the smaller Daphnia cucullata by the larger Daphnia galeata-hyalina complex that was attributable to successful food-web management did, however, result in a shift from a turbid to a clear water regime in 1999. Clearly, the zooplankton community, and therefore food-web structure, played an integral role in nutrient recycling and in the repartitioning of the phosphorus pool. As diatom settling and grazing became much more tightly linked with the appearance of the larger-bodied Daphnia galeata-hyalina complex, which exploits lower-level food resources as early as May, daphnids increasingly acted as a sink for phosphorus. This increased export fluxes out of the pelagic zone and leaves a smaller surplus of total phosphorus to support the accumulation of summer algae. Consequently, water transparency and total chlorophyll concentrations in summer improved with food-web restructuring, indicating real oligotrophication of Wupper Reservoir driven by internal feedbacks.

Estuaries are dynamic ecosystems which vary widely in loading of the contaminant methylmercury (MeHg), and in environmental factors which control MeHg exposure to the estuarine foodweb. Inputs of organic carbon and rates of primary production are important influences on MeHg loading and bioaccumulation, and are predicted to increase with changes in climate and land use pressures. To further understand these influences on MeHg levels in estuarine biota, we used a field study approach in sites across different temperature regions, and with varying organic carbon levels. In paired comparisons of sites with high vs. low organic carbon, fish had lower MeHg bioaccumulation factors (normalized to water concentrations) in high carbon sites, particularly subsites with large coastal wetlands and large variability in dissolved organic carbon levels in the water column. Across sites, MeHg level in the water column was strongly tied to dissolved organic carbon, and was the major driver of MeHg concentrations in fish and invertebrates. Higher primary productivity (chlorophyll-a) was associated with increased MeHg partitioning to suspended particulates, but not to the biota. These findings suggest that increased inputs of MeHg and loss of wetlands associated with climate change and anthropogenic land use pressure will increase MeHg concentrations in estuarine food webs.

The objectives of this study were to 1) determine the influence of environmental factors (water temperature, food availability [chlorophyll-a], salinity) on nacre deposition rate and tablet thickness at different positions in shells of two strains of pearl oyster, Pinctada fucata (Gould, 1850)—one from Japan, and one a Hybrid between this Japanese strain and another from China; 2) compare nacre deposition rates and tablet thickness in different shell positions within and between these two pearl oyster strains; and 3) determine relationships between shell nacre deposition rate and tablet thickness in host oysters of these two strains with those of their pearls. Nacre and tablet thickness were measured at three positions along the mantle pallial line (anterior, middle, and posterior), and one position close to the hinge, on the left valve of each oyster. Water temperature and chlorophyll-a were positively correlated (p < .001, Spearman's rho >0.75) and salinity was negatively correlated (p < .001, Spearman's rho < −0.7) with nacre deposition rate at all shell positions in both pearl oyster strains. Only water temperature below 13 °C influenced nacre tablet thinning. Significant differences in total nacre deposition occurred between the four sampling positions on the shell in both strains (p < .001), with deposition at the hinge area the slowest for both Hybrid (373.212 μm) and Japanese (569.248 μm) oysters. Nacre tablet thickness in the middle position on the shell increased most steadily over time, and was thinnest in the coolest months (0.151 μm and 0.167 μm for Hybrid and Japanese oysters, respectively). No significant difference (p > .05) in nacre tablet thickness was apparent between strains. Correlation analysis of nacre deposition rate between the shell and pearls showed that all shell positions were highly correlated with their respective pearls (p < .001, Spearman's Rho >0.75). Environmental factors influence shell nacre deposition and thickness, and because shell nacre deposition is related to pearl nacre, pearl growth also. This influence varies in different shell positions, with nacre deposition in the posterior position on the shell the fastest, and the middle position showing the most stable and thin nacre tablet. Japanese pearl oysters exhibit better nacre deposition than Hybrid oysters and would be more appropriate as host oysters in Ago Bay, Japan, should culture occur in environmental conditions comparable to those in this study.