The microfibre content of beach sediment samples was established at 175 sampling sites along over 2700 km of South Africa's coastline in 2016 and again in 2017. The average microfibre content was 80 ± 102 F/dm3 in Feb/March 2017 (n = 161), and 87 ± 84 F/dm3 in May/June 2016 (n = 128). These average values, and the observed ranges of 0 to 797 F/dm3 in 2017 and 4 to 772 F/dm3 in 2016, are consistent with global observations. The highest microfibre levels were observed at sampling sites close to large coastal waste water treatment work discharge points. Several instances of temporal variability are observed, only some of which can be associated with seasonal changes in river runoff. This baseline data set is a valuable reference point for identification of priority study sites for more detailed study of marine ecosystem response to microfibre pollution.

In this study, the bacterial and archaeal communities along with their functions of activated sludge from three wastewater treatment plants were investigated by Illumina MiSeq Platform. The treatment processes were modified A/A/O, DE oxidation ditch and pre-anaerobic carrousel oxidation ditch, respectively. The taxonomic analyses showed that Proteobacteria was the predominant bacterial phylum, and Nitrosospira was the dominant nitrification genus. Candidatus Accumulibacter was abundant in DE oxidation ditch process, and the main archaea communities were methanosaeta-like species which had the capability to anaerobic ammonia oxidation. The results illustrated that anaerobic ammonium oxidation played an important role in the nitrogen metabolism and there might be other unknown phosphate-accumulating organisms (PAOs) performing phosphorus removal in activated sludge. The predicted function analyses indicated that both bacteria and archaea were involved in nitrification, denitrification, ammonification and phosphorus removal processes, and their relative abundance varied metabolic modules differed from each other.

Carbon-capture and storage is considered to be a potential mitigation option for climate change. However, accidental leaks of CO2 can occur, resulting in changes in ocean chemistry such as acidification and metal mobilization. Laboratory experiments were performed to provide data on the effects of CO2-related acidification on the chemical fractionation of metal(loid)s in marine-contaminated sediments using sequential extraction procedures. The results showed that sediments from Huelva estuary registered concentrations of arsenic, copper, lead, and zinc that surpass the probable biological effect level established by international protocols. Zinc had the greatest proportion in the most mobile fraction of the sediment. Metals in this fraction represent an environmental risk because they are weakly bound to sediment, and therefore more likely to migrate to the water column. Indeed, the concentration of this metal was lower in the most acidified scenarios when compared to control pH, indicating probable zinc mobilization from the sediment to the seawater.

Chilean waters are often affected by Alexandrium catenella, one of the leading organisms behind Harmful Algae Blooms (HABs). Genetic variability for this species are commonly carried out from cultured samples, approach that may not accurately quantify genetic variability of this organism in the water column. In this study, genetic variability of A. catenella was determined by sequencing the rDNA region, in water samples from the Canal Puyuhuapi (South Austral Ecosystem of Chile). A. catenella was detected in 8,8% of samples analysed. All sequences obtained were A. catenella (Tamara complex group I), with three highly frequent haplotypes (34%), and twenty new haplotypes. These haplotypes increase the genetic variability from 2.8% to 3.14% in this area. Through this new method, genetic determination of A. catenella can accurately be monitored and ecological studies of this species can be implemented.

Though seagrass meadows are among the most productive habitats in the world, contributing substantially to long-term carbon storage, studies of the effects of critical disturbances on the fate of carbon sequestered in the sediment and biomass of these meadows are scarce. In a manipulative in situ experiment, we studied the effects of successive loss of seagrass biomass as a result of shading and simulated grazing at two intensity levels on sulphide (H2S) content and methane (CH4) emission in a tropical seagrass meadow in Zanzibar (Tanzania). In all disturbed treatments, we found a several-fold increase in both the sulphide concentration of the sediment pore-water and the methane emissions from the sediment surface (except for CH4 emissions in the low-shading treatment). This could be due to the ongoing degradation of belowground biomass shed by the seagrass plants, supporting the production of both sulphate-reducing bacteria and methanogens, possibly exacerbated by the loss of downwards oxygen transport via seagrass plants. The worldwide rapid loss of seagrass areas due to anthropogenic activities may therefore have significant effects on carbon sink-source relationships within coastal seas.

In New Caledonia, shrimp ponds are built not on cleared mangroves but on salt flats behind the mangroves. The objectives of this study were to determine the variability of CO2 fluxes from a semi-intensive shrimp pond during active and non-active periods of the farm and to determine the carbon dynamics from the upstream tidal creek to the downstream creek, which receives the farm's effluents. CO2 emissions from the active pond were estimated at 11.1 ± 5.26 mmol CO2 m−2 d−1. By modifying the hydrodynamics of the creeks, farm practices also influenced CO2 emissions from both the upstream and downstream creeks. After tillage, all the organic carbon deposited at the pond bottom during the active period was mineralized, resulting in CO2 emissions to the atmosphere estimated at 7.9 TCO2 ha−1. Therefore, shrimp farming is an anthropogenic source of CO2 to the atmosphere, but suitable and optimized rearing practices limit these emissions.

Reconstructing heavy metal historical trends are essential for better understanding anthropogenic impact on marine ecosystems. In this work, the ecological risk and sources of Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb in Jiaozhou Bay were studied and the anthropogenic metal emissions was also quantified. The ecological risk was mainly caused by Cd, As and Cu, which presented an increasing trend with increased anthropogenic activities since the 1950s. The statistical analysis show that Cr, Mn, Ni, Cu and Zn were primarily from natural sources. Cadmium and Mn might originate from both natural and anthropogenic sources. Arsenic and Pb were sourced from agricultural activities and atmospheric precipitation, respectively. The anthropogenic flux of Cr, Mn, Ni, Cu, Zn, As, Cd and Pb were 138, 586, 63, 66, 161, 35, 0.31 and 44 mg/m2/a since the 1950s. Over 40.0% of Cu and As were quantified from anthropogenic emissions since the 1950s.

Subsea blowouts have the potential to spread oil across large geographical areas, and subsea dispersant injection (SSDI) is a response option targeted at reducing the impact of a blowout, especially reducing persistent surface oil slicks. Modified Weber scaling was used to predict oil droplet sizes with the OSCAR oil spill model, and to evaluate the surface oil volume and area when using SSDI under different conditions. Generally, SSDI reduces the amount of oil on the surface, and creates wider and thinner surface oil slicks. It was found that the reduction of surface oil area and volume with SSDI was enhanced for higher wind speeds. Overall, given the effect of SSDI on oil volume and weathering, it may be suggested that tar ball formation, requiring thick and weathered oil, could possibly be reduced when SSDI is used.

Polycyclic aromatic hydrocarbons (PAHs) have been widely studied in sediments due to their ubiquity and persistence in aquatic environments and potential for impairment to biota. Small craft harbour (SCH) sediments in Nova Scotia (NS), Canada, have yet to be studied comprehensively. SCHs are essential to the fishing industry, which is important for the Canadian economy. This spatiotemporal characterization study evaluated thirty-one SCHs across NS between 2001 and 2017 by analyzing sediment reports (secondary data). Sediment PAH concentrations varied widely across all SCHs. Few SCHs exhibited sediment PAH concentrations likely to impair biota based on comparison to sediment quality guidelines. Sediments in the Gulf region of NS were least impacted by PAHs, while the Southwest region was most impacted. Distribution of individual PAHs in sediments follows global trends, with high molecular weight PAHs dominating samples.

This study is the first to systematically quantify, categorize, and map marine macro-debris across the main Hawaiian Islands (MHI), including remote areas (e.g., Niihau, Kahoolawe, and northern Molokai). Aerial surveys were conducted over each island to collect high resolution photos, which were processed into orthorectified imagery and visually analyzed in GIS. The technique provided precise measurements of the quantity, location, type, and size of macro-debris (>0.05m²), identifying 20,658 total debris items. Northeastern (windward) shorelines had the highest density of debris. Plastics, including nets, lines, buoys, floats, and foam, comprised 83% of the total count. In addition, the study located six vessels from the 2011 Tōhoku tsunami. These results created a baseline of the location, distribution, and composition of marine macro-debris across the MHI. Resource managers and communities may target high priority areas, particularly along remote coastlines where macro-debris counts were largely undocumented.