To investigate the effects of the water-sediment regulation on the spatial variations of metals in the surface sediments of the Yellow River Estuary (YRE), sampling sites were set in 2015 (51 sites in June and 33 in October). The content of Cu, Pb, Cd, Cr, Zn, Ni and Mn was determined using inductively coupled plasma spectrometry and of Hg and As atomic fluorescence spectrometry. The results showed that the concentrations of metals in the sediments of YRE were lower after the regulation, while that of most metals increased in the tidal areas of the current estuary with fine particles. Environmental pollution and ecological risk of metals were mainly from Hg and Cd. Metals carried with the silt of the river should be focused. The findings were expected to update the current status of metal pollution of YRE and be helpful for the delicacy management of the regime and silt-laden rivers.

Historically solid waste was commonly landfilled in the coastal zone in sites with limited engineering to isolate waste from adjacent coastal environments. Climate change is increasing the likelihood that these historic coastal landfills will erode releasing solid waste to the coastal zone. Historic coastal landfills are frequently located near designated ecological sites; yet, there is little understanding of the environmental risk posed by released waste. This research investigated inorganic and organic contaminant concentrations in a range of solid waste materials excavated from two historic coastal landfills, and the potential ecological impact should eroded waste be released to the coastal environment. Contaminant concentrations in the analysed waste materials exceeded sediment quality guidelines, indicating erosion of historic coastal landfills may pose a significant environmental threat. Paper and textile wastes were found to make a significant contribution to the total contaminant load, suggesting risk assessments should consider a wide range of solid waste materials.

We analyze Pb content and Pb isotope ratios in 29 surface sediments and one sediment core from the eastern Beibu Gulf, Southern China. The results indicate that obvious Pb enrichment was limited to the oil and gas exploration area in the central gulf and the mud deposit in the northern gulf. The enrichment of Pb in sediment core A97 started in the 1860s, but a notable drop of Pb content occurred in the 1970s, suggesting variations in human activity. The Pb isotope ratios in sediments were very similar to those in natural sources, except for the sediments near the oil platform, which may be polluted by anthropogenic input. Sediments with relatively high radiogenic Pb isotope compositions may be mainly sourced from northern coast of Beibu Gulf, sediment flux through Qiongzhou Strait, or the Red River, while the coastal zone of western Hainan Island and nearby bottom erosion area produce as minor provenances.

Artificial reefs are widely deployed for fishery enhancement and marine conservation. A comprehensive assessment on the effects of artificial reefs could minimize the negative consequence of blindly developing artificial reefs. We examined the meiofaunal community and benthic environment adjacent to and <5 m from artificial reefs in Xiangyun Bay, Bohai Sea, China. We found the highest total meiofaunal abundance beside the artificial reef. Shannon-Wiener and Pielou indexes had no significant difference among different distances from the artificial reefs. The presence of artificial reefs impeded the surrounding flow and provided additional substrate for bivalves and kelps, which could cause finer sediment and organic enrichment around it. Sediment grain size and total organic matter were the most important parameters influencing the meiofauna. We suggest that the shape, material, configuration and location of artificial reefs should be related with a specific goal to avoid mindless proliferation.

Microplastics (MPs) contamination has been recognized as one of major threats to coastal marine environments. Although studies evidenced severe MPs contaminations to the Pacific Ocean, environmental implications of MPs concentrations, distributions, and characteristics have not been evaluated in sufficient detail. Here, we report on the distribution, abundance, and characteristics of MPs at the surface of the Northwestern Pacific Ocean, from which environmental implications are assessed. A manta trawl with a mesh size of ~330 μm and a rectangular net opening of 0.45 × 1 m was used to collect MPs samples on May 11–June 3, 2018. The MPs samples were sequentially isolated, digested, filtered, and characterized using an optical microscope, micro-Raman spectroscopy, and scanning electron microscopy. The results indicate the heterogeneity in abundance, shapes, color, and sizes of MPs. The study provides strong environmental implications such as sources, environmental degradation, residence time, transportation routes, and biological interactions.

Estimates of marine debris are often based on beach surveys. Few studies have documented the veracity of these observations and the factors that may affect accuracy. Our laboratory-scale experiment identified potential sources of error associated with visual identification of marine debris (1–2 cm long) during shoreline surveys of sand beaches. Characteristics of the survey site (beach characteristics), observer (personal characteristics), and debris (color and size) may be important factors to consider when analyzing data from shoreline surveys. The results of this study show that the ability of individuals to accurately identify plastic fragments depends on the plastic and sand color, and density of shell fragments. Most suggestively, the high accuracy of blue plastic counts (95%) and the under-counting of white (50%) and clear plastic counts (55%) confirmed the hypothesis that a significant amount of clear and white plastic fragments may be missed during shoreline surveys. These results highlight the need for further research and possible modifications of visual shoreline survey methodologies in order to optimize this cost-effective method of marine debris monitoring.

There is a reasonably extensive body of literature recording mass loss of polyhydroxyalkanoates (PHAs) (a class of biodegradable plastics) in the natural marine environment. However, to date, this research has been very disparate. Thus, it remains unclear what the timeframe for the biodegradation of such marine biodegradable plastics actually is. The aim of this work was to determine the rate of biodegradation of PHA in the marine environment and apply this to the lifetime estimation of PHA products. This provides the clarification required as to what ‘marine biodegradation of PHA’ means in practicality and allows the risks and benefits of using PHA to be transparently discussed. It was determined that the mean rate of biodegradation of PHA in the marine environment is 0.04–0.09 mg·day⁻¹·cm⁻² (p = 0.05) and that, for example, a PHA water bottle could be expected to take between 1.5 and 3.5 years to completely biodegrade.

Active acoustic sensors are widely used in oceanographic and environmental studies. Although many have nominal operating frequencies above the range of marine mammal hearing, they can produce out-of-band sound that may be audible to marine mammals. Acoustic emissions from four active acoustic transducers were characterized and compared to marine mammal hearing thresholds. All four transducers had nominal operating frequencies above the reported upper limit of marine mammal hearing, but produced measurable sound below 160 kHz. A spatial map of the acoustic emissions of each sonar is used to evaluate potential effects on marine mammal hearing when the transducer is continuously operated from a stationary platform. Based on the cumulative sound exposure level metric, the acoustic emissions from the transducers are unlikely to cause temporary threshold shifts in marine mammals, but could affect animal behavior. The extent of audibility is estimated to be, at most, on the order of 100 m.

To investigate bioavailability of dissolved organic nitrogen (DON) and its contribution to nitrogen demand for Ulva prolifera, a cruise was conducted during a bloom of U. prolifera in Qingdao coastal waters, China, dissolved inorganic nitrogen (DIN) and DON components were investigated. Uptakes of both DIN and DON by U. prolifera were synchronously measured onboard using stable isotope techniques. The contribution of DON to total dissolved N (TDN) was >50% and that of labile components (urea and to amino acids, AA) to DON exceeded 30%. Both DIN and DON were utilized by U. prolifera, which uptake NH4-N preferentially, then urea, NO3-N and AA in turn; whereas the ranking of turnover times from short to long was AA, NH4-N, urea and NO3-N. The high uptake rates and short turnover time of AA and urea indicated that DON may play an important role in the nutrition of U. prolifera.