Derelict fishing nets pose hazards to marine systems as they travel through the ocean or become ensnared on coral reefs. Understanding of the movement of nets within shallow atolls can help to optimize operations to protect these shallow reefs. In 2018, six derelict fishing nets at Manawai (Pearl and Hermes Reef) in the Northwestern Hawaiian Islands were tagged with satellite-transmitting buoys and tracked for three years. This study reveals that nets that enter the atoll from the northeast travel southwest towards the center of the atoll, and nets in the center can remain ensnared on the same reef for at least three years. This study shows that satellite buoys are a successful approach to tracking derelict net movement, and can inform future debris removal missions.

Concentrations of eight metals, organic carbon (Corg), and eight oxides were measured in 33 river sediment samples from the Nandu River. Sediment quality guidelines (SQGs) showed no severe pollution at all stations. However, according to the geo-accumulation index (Igeo), enrichment factor (EF), and potential ecological risk index (EI and RI), As and Cd were the primary pollutants in the survey area and caused low to moderate potential ecological risk. The positive correlations between Al₂O₃, TFe₂O₃, Mn, Corg, and metals indicated that clay, FeMn oxides, and organic carbon content were the main factors for metal accumulation in the study area. From the results of correlation (CA) and principal component analysis (PCA), we inferred that Cr, Ni, Cu, and Zn were mainly from natural sources, while As, Cd, Hg, and Pb were from anthropogenic activities in the Nandu River basin. This was the first study of metal pollution in the surface sediments of the Nandu River, which will serve as a reference for future research.

In this study, we evaluated metal accumulation in different species and tissues of seagrasses and green macroalgae Halimeda and assessed metal pollution levels in Chuuk, Micronesia. In seagrass, the concentrations of Ni, Cu, Zn, Cd, Pb, and Hg were higher in leaves than in roots, whereas Cr and As concentrations were higher in roots. Halimeda had higher concentrations of Ni than of the other metals, and the mean Ni concentration was approximately 2.1 times higher in Halimeda than in seagrass leaves. The concentrations of Cr, As, Cu, Pb, and Hg in Halimeda were similar to those in seagrasses, whereas the Zn and Cd concentrations in Halimeda were very low. Significant correlations in metal concentrations between sediment and both seagrasses and Halimeda were observed for Cr, Ni, Cu, Zn, and Pb. This study suggests that seagrasses and Halimeda are useful indicators for monitoring metal pollution in coastal environments.

Sunscreens generate a potentially important source of environmental contamination across marine and aquatic systems. Oxybenzone (benzophenone-3; BP-3) is one of the most common organic filters in chemical sunscreen and has been detected in seawater at high concentrations. In this study, we asked whether BP-3 contamination affected the photosynthesis, respiration, and photophysiology of rhodoliths collected offshore from popular Gulf of Mexico beaches in North Florida. We found no evidence for negative effects of the common organic UV filter BP-3 on Gulf of Mexico rhodoliths. This result is promising for the fate of these important algae who act as habitat builders and foundational components of global reef ecosystems.

The concentrations, sources, and ecological risks of nine trace elements in nine rivers flowing into Laizhou Bay were investigated. The dissolved element concentrations were 1.85–74.4, 0.01–0.47, 0.15–3.46, 1.54–19.7, 2.92–45.1, 1.72–11.5, 1.02–8.35, 0.10–1.02, and 21.4–185 μg/L for As, Cd, Co, Cr, Cu, Ni, Sc, Pb, and Zn, respectively. Zinc was the most abundant element in the sediments, with an average concentration of 106 mg/kg, followed by Cr (64.5 mg/kg), Cu (25.5 mg/kg), Pb (24.3 mg/kg), Ni (23.4 mg/kg), Co (10.9 mg/kg), Sc (8.14 mg/kg), As (6.75 mg/kg), and Cd (0.16 mg/kg). Elements including Co, Cr, Ni, and Sc were mainly from natural sources and As, Cd, Cu, Pb, and Zn were largely influenced by anthropogenic activities such as agricultural practice, industrial production, river transportation, and urbanization. Overall, the rivers flowing into Laizhou Bay experienced slight pollution and ecological risk. However, the severe element contamination in Jie River deserves continuous attention.

To explore the pollution levels, sources and risks of heavy metals in sediments in Fuzhou reach of the Min River, the sediments involving in seven marsh types were sampled. Results showed that the concentrations of Pb, Zn and Cd in sediments declined from freshwater segment to estuarine segment. Higher levels of Cu, Cr and Ni in sediments generally occurred in estuarine segment. The highest levels of Pb and Cd were observed in bush swamp, while those of Cr, Ni, Zn and Cu occurred in mudflat. Cr, Cu, Zn and Ni probably shared common source, while Pb and Cd originated from another source. Pb and Cd were identified as heavy metals of primary concerns and the former showed high potential toxicity and high contributions to ΣTUs. Next step, the metal pollutions in sediments might be more serious if effective measures were not taken to control the loading of pollutants.

The agrochemicals and nutrient losses from farming areas such as paddy farming significantly dictate quality and eutrophication of the freshwater resource. However, how farming and land use pattern affect water qualities and eutrophication remain poorly understood in most African agro-ecosystems. The present study characterized how paddy farming influences water qualities and eutrophication in 10 irrigation schemes in Usangu agro-ecosystem (UA). About 42 water samples were sampled from intakes, channels, paddy fields, and drainages and analyzed for EC, Cl, P, NH₄-N, NO₃-N, TN, Zn, Cu, Ca, and Mg. We observed water pH ranging from 4.89 to 6.76, which was generally below the acceptable range (6.5–8.4) for irrigation water. NH₄-N concentration was in a range of 10.6–70.0 mg/L, NO₃-N (8.4–33.9 mg/L), and TN (19.1–21,104 mg/L). NH₄-N increased along sampling transect (sampling points) from intakes (5.7–29.1 mg/L), channels (19–20 mg/L), fields (12.9–35.8 mg/L), and outflow (10.6–70.0 mg/L), the same trend were found for NO₃-N and TN. The TP determined in water samples were in the range of 0.01 to 1.65 mg/L; where some sites had P > 0.1 mg/L exceeding the allowable P concentration in freshwater resource, thus indicating P enrichment and eutrophication status. The P concentration was observed to increase from intake through paddy fields to drainages, where high P was determined in drainages (0.02–1.65 mg/L) and fields (0.0–0.54 mg/L) compared to channels (0.01–0.13 mg/L) and intakes (0.01–0.04 mg/L). Furthermore, we determined appreciable amount of potentially toxic elements (PTEs) such as Cu, Pb, Cd and Cr in studied water samples. The high N, P, and PTEs in drainages indicate enrichment from agricultural fields leading to water quality degradation and contaminations (eutrophication). The study demonstrates that water quality in UA is degrading potentially due to paddy rice farming and other associated activities in the landscape. Thus, the current study recommends starting initiatives to monitor irrigation water quality in UA for better crop productivity, and improved quality of drainage re-entering downstream through the introduction of mandatory riparian buffer, revising irrigation practices, to include good agronomic practices (GAP) to ensure water quality and sustainability.

Rivers are the key conduits for land-to-sea debris transport. We present in situ monitoring data of macro debris and microplastic along the supercritical Citarum River in Indonesia We identified the dams as concentrated areas of microplastic. Plastics accounted for 85% of the riverine debris (5369 ± 2320 items or 0.92 ± 0.40 tons daily). We estimated macrodebris releases of 6043 ± 567 items or 1.01 ± 0.19 tons daily with a microplastic concentration of 3.35 ± 0.54 particles per m³ from Citarum River to sea. It has been suggested that population density and urbanization rate are major factors determining the spatiotemporal variability of macrodebris and microplastic abundances in the Citarum River. Our research highlights the importance of long-term monitoring to estimate debris and microplastics inflows along the Indonesian river to the world ocean as a benchmark for the reduction of macro and microdebris into the environment.

In order to evaluate suitable remediation strategies for Cu-polluted soils, the growth, tolerance, and Cu accumulation of Sarcocornia perennis and Limonium brasiliense were studied in hydroponic culture using different Cu concentrations, with and without Undaria pinnatifida compost. Most measured variables (e.g., water content, aboveground dry weight, malondialdehyde, pigments concentrations, tolerance index) showed a negative effect of high Cu levels in plants without compost but not in plants with compost. Plants accumulated high Cu levels in belowground tissues (bioaccumulation factor > 1) showing low translocation to aboveground parts. Based on the results, we suggest two remediation strategies: a short-term strategy: root absorption of Cu by halophytes, and a long-term strategy: using halophytes and U. pinnatifida compost, involving absorption of Cu by the plants together with metal immobilization in the substrate. This last strategy offers an additional advantage: it provides a use for seaweed waste, considered a problem for several coastal cities.

The Mediterranean Sea water bodies are ones of the most polluted, especially with microplastics. As the seafloor is the ultimate sink for litter, it is considered a hotspot for microplastic pollution. We provide an original analytical development based on the coupling of tandem mass spectrometry to pyrolysis-gas chromatography to improve the detection of plastic contamination in marine organisms. Due to the high selectivity of the mass spectrometer, a straightforward sample preparation consists uniquely of potassium hydroxide digestion. The quantification of six common polymers is possible in one run. The method was applied to analyze the plastic content from 500 μm down to 0.7 μm in the whole body of seven benthic species with variable feeding modes. Plastic was detected in all samples, with an almost systematic detection of polypropylene and polyethylene. Our method presents a major development in determining the levels of plastic contaminations in samples with rich organic matter content.