There is growing global concern over the chemical, biological and ecological impact of plastics in the ocean. Remote sensing has the potential to provide long-term, global monitoring but for marine plastics it is still in its early stages. Some progress has been made in hyperspectral remote sensing of marine macroplastics in the visible (VIS) to short wave infrared (SWIR) spectrum. We present a reflectance model of sunlight interacting with a sea surface littered with macro plastics, based on geometrical optics and the spectral signatures of plastic and seawater. This is a first step towards the development of a remote sensing algorithm for marine plastic using light reflectance measurements in air. Our model takes the colour, transparency, reflectivity and shape of plastic litter into account. This concept model can aid the design of laboratory, field and Earth observation measurements in the VIS-SWIR spectrum and explain the results.

The eutrophication status of the German Bight (North Sea) has been assessed the third time since 1998 according to the OSPAR-Comprehensive Procedure between 2006 and 2014. Since the 1980s nutrient discharges and atmospheric nitrogen deposition had declined significantly but chlorophyll a and nutrient concentrations remained above assessment levels inshore and in inner coastal waters, reflecting continuing eutrophication. Recently local river discharges stagnated or increased again and total nitrogen remained above a reduction target of 200 μM. Most nutrients and conversion products were imported by a coastal current, passing the German Bight. Organic matter was trapped in offshore bottom waters in the ancient Elbe valley, causing repeated annual oxygen minima (<6 mg/L) and a classification as Problem Area. Effects of national reduction measures are limited in the transit area German Bight because improvements in open coastal waters require international efforts, based on comprehensive analyses.

Myriophyllum spicatum was cultivated in a low salinity area of Hangzhou Bay (salinity 5.8–6.5), from August to October in 2016, to evaluate the abilities of its nutrient bioextraction and microalgae growth inhibition. During the 72-day cultivation period, M. spicatum had a specific growth rate (SGR) of 6.23%day⁻¹ and increased 20-fold in biomass (wet weight). Tissue C, N and P assimilation quantities of M. spicatum were found to be 3279.39kg, 360.61kg and 26.97kg, respectively. The concentration of NH₄-N, NO₃-N, NO₂-N and PO₄-P after M. spicatum cultivation was decreased by 47.92%, 58.28%, 36.40% and 55.57%, respectively. The phytoplankton density was decreased from 1064.60×10⁴cellsL⁻¹ to 12.85×10⁴cellsL⁻¹. These results indicated that cultivation of M. spicatum can help in nutrient bioextraction and microalgae growth inhibition in low salinity marine water bodies.

Estuarine sediments can be a source of Phosphorus (P) to coastal waters, contributing to nutrient budgets and geochemical cycles. In this work, the concentration and speciation of P in 47 cores were examined from the inter-tidal mud flats of the tidal river Thames (~120km). Results of P concentration and speciation were combined with published data relating to known sediment dynamics and water chemistry (salinity) within the estuary to produce a conceptual model of sediment-P behaviour. Results demonstrated significant P desorption occurring after sediment passed through the Estuarine Turbidity Maximum and when the salinity of the river water exceeded ~6ppt. It was found that organic P was desorbed to a greater extent than inorganic P in the lower estuary. Models were used to identify those geochemical parameters that contributed to the Total P (R²=0.80), oxalate extractable P (R²=0.80) and inorganic P (R²=0.76) concentrations within the Thames estuary.

In order to reveal the spatio-temporal distribution of meiofaunal assemblages and its relationship with environmental factors in semi-enclosed bay habitats, meiofaunal and sediment samples were collected in February (winter), May (spring), August (summer) and November (autumn) 2014 in Jiaozhou Bay, China. A total of 20 meiofaunal taxa were identified. The most dominant group was free-living marine nematode, followed by benthic copepod. During the four sampling seasons, the values of meiofaunal average abundance were (912.3 ± 603.1), (1576.4 ± 659.5), (1074.6 ± 417.6), (2152.4 ± 1062.3) ind./10 cm2 while those of biomass were (575.0 ± 398.5), (874.3 ± 518.4), (617.9 ± 337.8), (1203.6 ± 719.6) μg dwt/10 cm2, respectively. In terms of vertical distribution, meiofauna were mainly found in the (0–2) cm sediment layer (59.92%), followed by (2–5) cm layer (28.25%) and (5–8) cm layer (11.82%). Results of correlation analysis showed that bottom water temperature was the main factor influencing meiofaunal distribution and food source (sediment organic matter content) was the main factor influencing meiofaunal assemblages.

In order to investigate the current distribution of metal concentrations in surface marine sediments of the southern coast of Sfax (Tunisia), thirty-nine samples were collected in the vicinity of a mixed industrial and domestic wastewater effluent discharge. In comparison with the threshold effect level and probable effect level, the majority of metals had high ecological and biological risks. Enrichment factor and geoaccumulation Index showed that the majority of sediments are unpolluted by As, Ni and Pb, moderately polluted by Cr and Cu and moderately to strongly polluted by P, Y, Zn. Besides, all sites are extremely polluted by Cd. Principal component analysis indicates that As, Cu and Ni were mainly from lithogenic sources, whereas Cd, Cr, F, P, Pb, Y and Zn were mainly derived from anthropogenic source. Findings of this research can be used as suitable reference for future studies and environmental management plans in the region.

Bivalves are commonly used as biomonitors for heavy metal pollution in marine environments because they accumulate heavy metal ions quickly, are sessile, abundant, and widely dispersed, and adult mortality from contamination is rare. However, the breadth of experiments used to measure the effect of heavy metal contamination can obscure general trends. It is unclear which heavy metals cause the most severe effects, how severity varies with exposure concentration and duration, and whether effects vary with level of biological organization. I conducted a meta-analysis of 48 mesocosm studies on the effects of heavy metal ions – silver, cadmium, copper, mercury, lead, and zinc – on marine bivalves. The ordering of effect sizes was Pb > Hg > Cu > Zn > Cd > Ag. The significance and direction of concentration and duration as moderators depended on the metal and the biological level. Future studies should consider non-linear effects over time and concentration, and measure both bioaccumulation and effect of the metals being studies.

Accumulation and bioindication of trace elements were compared in three seagrasses growing in the Mediterranean Sea: Posidonia oceanica, Cymodocea nodosa and Halophila stipulacea. The levels of the elements As, Cd, Cr, Cu, Hg, Mn, Ni, Pb and Zn were investigated in water, sediments, and roots, rhizomes and leaves of seagrasses. Results showed that seagrasses can accumulate comparable levels of trace elements, but P. oceanica and C. nodosa showed higher mean values of element accumulation. Moreover, P. oceanica and C. nodosa may accumulate high element concentrations in their leaves, whereas in H. stipulacea restricted with the bulk of trace elements in roots and rhizomes. Seagrasses reflected to a different degree the levels of several trace elements in sediments, especially P. oceanica and C. nodosa, whose use as bioindicators is recommended. The future step for an effective use of seagrasses as bioindicators of marine pollution is to set up biomonitoring networks on a large scale.

Measurements of total organic carbon (TOC) for two years in Kuwaiti waters showed high TOC levels (101.0–318.4, mean 161.2 μM) with maximal concentrations occurring within the polluted Kuwait Bay and decreasing offshore, indicating substantial anthropogenic component. Analysis of winter-time data revealed a large increase in density over the past four decades due to decrease in Shatt Al-Arab runoff, implying that the dissolved/suspended organic matter in surface waters of the northern Gulf could be quickly injected into the Gulf Deep Water (GDW). Our measurements together with an analysis of previously collected/published data suggest that the recent summer-time declining trend in oxygen in the GDW might be related to eutrophication. Higher preformed TOC and lower preformed dissolved oxygen contents of the high-salinity water mass that flows out of the Gulf and ventilates the mesopelagic oxygen minimum zone (OMZ) of the Northwestern Indian Ocean may cause expansion/intensification of the regional OMZ.

Mercury (Hg) biotransformation and biomagnification are processes that affect Hg burdens in wildlife. To interpret variation in Hg in seabird eggs, used as Hg bioindicators in the Arctic, it is important to understand how Hg biomagnifies through the food web. We evaluated the use of δ34S, along with other commonly used stable isotope signatures (δ15N and δ13C), for the determination of possible sources of Hg in an Arctic food web (56 individuals of 15 species of fish and invertebrates). Hg correlated with δ34S (R2 = 0.72). When the combined effects of δ34S and δ15N were considered in mixed-effects models, both δ34S and δ15N together described Hg patterns in Arctic food webs better than either isotope alone. Our results demonstrate the usefulness of δ34S to account for variation in Hg among marine animals and to study the possible underlying effects that MeHg production may have on Hg pathways in Arctic ecosystems.