Sediment cores were analyzed from the continental shelf of the northwestern South China Sea aiming to understand the change history of primary productivity and provide insights into key changes of environmental conditions in this region over the past ~100 years. Multiple proxies including stable carbon isotopic composition (δ¹³C) of sedimentary organic matter, diatom abundance and biogenic silica burial flux were applied along with ²¹⁰Pb chronology. Notably, these independent evidences consistently point to a steady increase of primary production in this region only after ~1960s. We propose that increasing atmospheric deposition due to dramatically enhanced human activities especially from China supplies essential nitrogen nutrients to the N-poor region and probably acts a major reason for the observed enhancement of marine primary production. Our study provides insights into better understanding how human perturbation may have profoundly impacted biogeochemical cycling in marginal seas in the last decades.

Tributyltin (TBT) was a commonly used biocide in anti-fouling paints for marine vessels, however, it had negative impacts on non-target species, including causing imposex in dogwhelks (Nucella lapillus). Since the 1980s, legislation has been introduced to curtail its usage, culminating in a ban by the International Maritime Organisation (IMO) in 2008. In 2004 a national imposex monitoring network was established in Northern Ireland to determine the level and extent of TBT pollution. The level of imposex in N. lapillus was assessed according to the degree of male sexual development in the female using three measures: percentage of imposex-affected females (%I), the relative penis size index (RPSI), and the vas deferens sequence index (VDSI). All sites showed improvement since the initial survey with a reduction in imposex and an improvement in ecological quality under the classification of the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR).

Seagrass longevity up to 47 years in well-restored, well-sited seagrass restorations are demonstrated from 253 trials at 83 regional sites in tropical and subtropical portions of three oceans (Atlantic, Pacific, Indian Oceans). These trials include over 3.04 million planted units into 306.3 ha. Approximately 12% of the total global tropical restored seagrass by Van Katwijk, Thorhaug et al. (2016) calculations from 1786 trials are included. Almost all projects herein reviewed persisted since date of planting except several cases with harsh anthropogenic impact or forceful natural events in first post-planting months. The oldest tropical/subtropical restoration continually observed is 47 yrs, many are 35 yrs. An array of observed and/or measured restored services accompanied these. This review may provide informational background for government resource managers, legislators, scientists, and citizens concerning tropical/subtropical seagrass longevity. This data from these trials may substantiate future seagrass restoration investments. Public outreach, national & regional government training,and outreach occurred, needing continuation.

Capping represents an efficient and well-established remediation practice to contain pollutants in sediments. Coupling capping amendments with biodegradation is an emerging technology with great potential to promote simultaneous sequestration and oxidation of contaminants in situ. Capping materials alter the native sediment environment and affect the biodegradation potential of benthic microbial communities. The placement of materials specifically influences (i) porewater pH and composition, (ii) nutrient fluxes, (iii) electron accepting processes, (iv) bioavailability of contaminants, and (v) biofilm formation. This review summarizes current literature documenting the impact of these alterations on microbial ecology and biodegradation activity, describes recent advances in bioactive sediment caps, and identifies areas where additional research is warranted.

This study evaluated for the first time, the distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in sediments collected along the northern Patagonian shelf in the Argentine Sea –included in a Marine Protected Area (MPA). Total concentration of the PAHs varied from 19.47 to 183.17 ng/g dry weight and low molecular weight compounds, such as Anthracene and Naphthalene were the dominants. The selected PAHs ratios suggested a predominance of petrogenic sources and ecotoxicological risk evaluation based on the sediment quality guidelines model, indicated that some PAHs might cause occasional adverse biological effects in the study area.

To assess potential dispersion of pollutants around Honiara, Solomon Islands, and Port Vila, Vanuatu, 3D ocean circulation models were developed using Telemac-3D. A series of scenarios then explore the vulnerability of the system and test potential control measures. Results show that high coastal concentrations are most likely during the wet season, with increased volumes of discharge as well as favourable wind speed and direction. Buoyant plumes flow along the coastline, and high concentrations build up in enclosed bays. Control measures tested focus on consolidating existing outflows at depth off-shore. This results in an overall reduction of surface concentrations along the coastline. However, the reduction is dependent on the depth, off-shore positioning, and volume of outflow. With increased concentrations then found at depth, the subsequent impact on off-shore and benthic ecosystems would also need to be considered.

We model three-dimensional motion of plastic pollution in Lake Erie due to advection, density-driven sinking, and turbulent mixing using a Lagrangian transport model to explore the distribution of plastic in the water column and sediment. Nine polymer types that make up over 75% of predicted worldwide plastic waste were modeled, and the model keeps track of particles that hit the bottom to represent deposition. Modeled spatial distributions are compared with samples from the surface to calibrate the model and derive estimates for the mass of plastic in the lake volume and the flux of plastic into the sediment. The mass estimate of 381 ± 204 metric tons is two orders of magnitude larger than previous surface estimates, though still a fraction of predicted yearly input. The results are a step towards closing the plastic mass balance in Lake Erie as well as understanding the transport of plastic into the sediment.

We examined the spatial distribution and local characteristics of microplastics (0.33–5 mm) in surface water from six semi-enclosed bays and two coastal waters in Korea. Surveys were conducted in July from 2015 to 2017 using a Manta trawl. The mean abundance of total microplastics ranged from 1.12–4.74 particles/m³ among sites; the microplastics were mostly expanded polystyrene (EPS), paint particles, fragments and fibers. The mean microplastic abundance (2.85 particles/m³) in urban areas was about 1.5 times higher than in rural areas (1.86 particles/m³) (p < 0.05). EPS dominated at rural sites, while fragments, paint particles, and fibers were relatively more dominant in urban areas. The different types and quantities of microplastic particles indicated that the region-specific occurrence of microplastics is likely to be related to differences in human activities between urban and rural areas, even though fibers were distributed throughout the study area.

French Polynesia exhibits a wide diversity of islands and coral-reef habitats, from urbanized high islands to remote atolls. Here, we present a geographically extensive baseline survey that examine the concentrations of nine metals (Ag, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) and one metalloid (As) in superficial sediments from 28 sites spread over three islands of French Polynesia. We used Principal Component Analysis, Pearson's correlation, hierarchical cluster analysis and generalized linear mixed-effect models on Pollution Load Index to investigate site contamination and metal(loid) associations. At most sites, metal(loid) concentrations were below commonly applied sediment quality guidelines. However, a few sites located near farming activities, river discharges and urbanized areas showed concentrations above these guidelines. This study provides critical baseline values for metal(loid) contaminants in this region and in coral-reef areas in general, and spur decreased discharge of metal(loid) contaminants in the anthropogenised areas of French Polynesia.

The objective of this study was to evaluate the bioavailability of the metals cadmium, copper, lead, nickel, and zinc from sediment samples collected in the Paraguaçu river between the cities of Cachoeira and São Félix in the state of Bahia in Brazil. The method used was the acid extraction of volatile sulfides and metals extracted simultaneously (AVS-SEM) as described in the literature. For the extraction of sulfide, an argon drag system was used after acidification of the samples with HCl, releasing the volatile sulfides collected in the basic solution. Its determination was made by molecular absorption spectrophotometry using the methylene blue method. For quantification of the metals, the sediment with acid was filtered and the residual solution was analyzed by inductively coupled plasma mass spectrometry (ICP MS) in which the elements that were associated with the sulfide were released in solution. The bioavailability evaluation was done by the relation between the sum of the concentrations of the metals in solution (SEM) and the concentration of sulfide in each sample (AVS). When the ∑SEM/AVS ratio is >1, the medium is considered contaminated by the high bioavailability of the metals to other environmental compartments. In the samples collected in the Paraguaçu river in two campaigns, with an ∑SEM/AVS ratio of 0.007 to 1.082, the last value being the only critical>1, while the other quantities in the metallic phase were not available for a biota. By comparing the metal concentration data with the internationally established tolerance limits, all the values found were below the critical values, presenting no toxic risks to the surrounding ecosystem.