Within wetlands, epiphytes and macrophytes play an important role in storage and transfer of metals, through the food web. However, there is a lack of information about spatial and temporal changes in their metal levels, including those of mercury (Hg), a key priority contaminant of aquatic systems. We assessed total mercury (THg) and methylmercury (MeHg) concentrations of epiphyte/macrophyte complexes in Lake St. Pierre, a large fluvial lake of the St. Lawrence River (Québec, Canada). THg and MeHg concentrations were ten fold higher in epiphytes than in macrophytes. THg concentrations in epiphytes linearly decreased as a function of the autotrophic index, suggesting a role of algae in epiphyte Hg accumulation, and % of MeHg in epiphytes reached values as high as 74%. Spatio-temporal variability in THg and MeHg concentrations in epiphytes and macrophytes were influenced by water temperature, available light, host species, water level, dissolved organic carbon and dissolved oxygen.

Endocrine disrupting compounds (EDCs) like bisphenol A (BPA), 4-tert-octylphenol (OP) and 4-nonylphenol (NP) are introduced to the trophic webs through among others phytoplankton. This paper describes BPA, OP and NP concentrations in phytoplankton in the Gulf of Gdansk (Southern Baltic Sea) in the years 2011–2012. The assays of BPA, OP and NP in samples were performed using HPLC with fluorescence detection. The concentrations of BPA, the most commonly used of the three compounds, were over ten times higher than OP and NP concentrations. The concentrations of the studied EDCs in phytoplankton from the Gulf of Gdansk depended on anthropogenic factors and on phytoplankton properties (species composition, biomass, volume). An increase in phytoplankton biomass did not always result in an increase of BPA, OP and NP concentrations. However, the load of the studied EDCs accumulated in phytoplankton biomass increase with a rise of biomass. An increase in BPA, OP and NP concentrations was effected by biomass growth and the proportions ofciliates, dinoflagellates, diatoms and green algae. A strong positive correlation between OP and NP concentrations and negative correlation between BPA concentrations and biomass of organisms with cells measuring <1000 μm3 in volume results from the differing properties of these compounds.

One way organic pollutants reach remote oceanic regions is by atmospheric transport. During the Malaspina-2010 expedition, across the Atlantic, Indian, and Pacific Oceans, we analyzed the polycyclic aromatic hydrocarbon (PAH) effects on oceanic microbial food webs. We performed perturbation experiments adding PAHs to classic dilution experiments. The phytoplankton growth rates were reduced by more than 5 times, being Prochlorococcus spp. the most affected. 62% of the experiments showed a reduction in the grazing rates due to the presence of PAHs. For the remaining experiments, grazing usually increased likely due to cascading effects. We identified changes in the slope of the relation between the growth rate and the dilution fraction induced by the pollutants, moving from no grazing to V-shape, or to negative slope, indicative of grazing increase by cascade effects and alterations of the grazers' activity structure. Our perturbation experiments indicate that PAHs could influence the structure oceanic food-webs structure.

Mercury (Hg) and selenium (Se) concentrations were evaluated in a planktivorous fish and four size classes of organisms (FSCO), collected at an oligotrophic bay in the Southeastern Brazilian coast. No significant spatial differences between Hg and Se were found in the FSCO within the five sampling points in the bay. Hg and Se concentrations increased with successive increases in the size class of the analyzed plankton, i.e. approximately 3-and 2-fold, respectively, from microplankton to macroplankton. Hg and Se biomagnified throughout the planktonic food web. The smallest size class of organism, seston, composed of both biotic and abiotic portions, and fish showed the highest Hg concentrations. This indicates that Hg is not biomagnifying in the base of the bay food web. Selenium concentrations in fish were approximately 5.9 times higher than those in seston. Hg and Se concentrations in fish were approximately 3.5 and 14.6 times higher than those found in the plankton, respectively.

This laboratory study measured the direct effects of three polycyclic aromatic hydrocarbon (PAH) compounds (naphthalene, pyrene, and benzo(a)pyrene) upon cell growth, membrane integrity, and BODIPY-stained lipid fluorescence intensity of the benthic diatom Nitzschia brevirostris using flow cytometry as an analysis tool. Previous field and laboratory studies have reported reductions in algal populations following PAH exposure, but specific, functional responses of the microalgae to these pollutants could not be revealed by cell numbers alone. Using flow-cytometric measurements, we confirmed that maximal cell densities in PAH-exposed diatom cultures were significantly lower compared to controls; however, we also discovered increases in lipids and cells with compromised membranes in PAH-exposed cultures. These results highlight new tools for measuring the direct effects of organic pollutants upon the physiology of taxa comprising microphytobenthic communities important in estuarine food webs.

Pacific angel sharks (Squatina californica) are a benthic elasmobranch that occupy intermediate trophic level positions in coastal food webs. Angel sharks’ life history characteristics make them susceptible to accumulating high amounts of contaminants. Four angel sharks were opportunistically captured in southern California and their liver and uterine contents were analyzed for PCBs, DDTs and other pesticides. High DDT:PCB ratios were found in the sharks indicating direct or indirect foraging near a local EPA Superfund Site. Organic contaminants were measured in ovulated eggs, indicating that females are able to maternally offload contaminants. Despite the potential mismatch between ovarian and uterine fecundity, we estimated females to offload approximately 13±5% of their total body load, which represents the upper limit of this capability. Although low in sample size, the initial findings from this study suggest that habitat use might play an important role in contaminant accumulation in this species.

This baseline study highlights the 210Po and 210Pb concentration in two species of the benthic macroalgae Sargassum from northern Gulf, also known as the ROPME Sea Area (RSA). Within the marine environment, 210Po is initially absorbed from water and concentrated by phytoplankton and macroalgae, and this concentrated 210Po can then readily be passed along to the higher trophic level of the marine food web. The 210Po concentration measured in Sargassum boveanum (22.5–25.6Bqkg−1) was higher than that in Sargassum oligocystum (20.2–22.5Bqkg−1), but is not statistically significant (p>0.064), where as the difference between 210Pb concentrations in Sargassum boveanum (15.3–16.8Bqkg−1) and Sargassum oligocystum (18.4–22.0Bqkg−1) was statistically significant (p>0.019). The measured concentration factor for 210Po in Sargassum in the northern Gulf varied between 0.55 and 1.2×104, values higher to the IAEA recommended value of 1×103. The 210Po enrichment is observed in both the species of Sargassum,210Po/210Pb ratio was >1 at all the stations for all the samples.

Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14μM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1–72μgchl-aL−1), production (PP=10–2657μgCL−1h−1) and photosynthetic efficiency (PB=0.5–45μgCμgchl-a−1), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system’s trophic web.

Intertidal benthic ecosystems in estuaries are productive sites where microbial processes play critical roles in nutrients mineralization, primary production and trophic web. In this groundwork study we analyzed the bacterial community of intertidal biofilms from Río de la Plata beaches with different anthropogenic impacts. Several environmental parameters were measured and bacterial assemblages were analyzed by 16S-rDNA pyrosequencing. The average OTU found per sample was 527.3±122.5, showing similar richness and diversity among them. However, sites having the highest and lowest salinity displayed higher bacterial diversity. Assemblages from a site nearby an oil refinery, showing the lowest salinity and oxygen concentration, were clearly distinct from the rest. The weight of this splitting relied on OTUs belonging to Thauera, known by its ability to metabolize aromatic compounds. Our results suggest that intertidal bacterial assemblages would be structured by major estuarine variables such as salinity, and that anthropogenic-induced environmental parameters might also be relevant.

Facing a generalized increase in water degradation, several programmes have been implemented for protecting and enhancing the water quality and associated wildlife, which rely on ecological indicators to assess the degree of deviation from a pristine state. Here, single (species number, Shannon–Wiener H’, Pielou J’) and multi-metric (Estuarine Fish Assessment Index, EFAI) community-based ecological quality measures were evaluated in a temperate estuary over an 8-year period (2005–2012), and established their relationships with an anthropogenic pressure index (API). Single metric indices were highly variable and neither concordant amongst themselves nor with the EFAI. The EFAI was the only index significantly correlated with the API, indicating that higher ecological quality was associated with lower anthropogenic pressure. Pressure scenarios were related with specific fish community composition, as a result of distinct food web complexity and nursery functioning of the estuary. Results were discussed in the scope of the implementation of water protection programmes.