Coastal water clarity varies at high temporal and spatial scales due to weather, climate, and human activity along coastlines. Systematic observations are crucial to assessing the impact of water clarity change on aquatic habitats. In this study, Secchi disk depths (ZSD) from Boston Harbor, Buzzards Bay, Cape Cod Bay, and Narragansett Bay water quality monitoring organizations were compiled to validate ZSD derived from Landsat 8 (L8) imagery, and to generate high spatial resolution ZSD maps. From 58 L8 images, acceptable agreement was found between in situ and L8 ZSD in Buzzards Bay (N = 42, RMSE = 0.96 m, MAPD = 28%), Cape Cod Bay (N = 11, RMSE = 0.62 m, MAPD = 10%), and Narragansett Bay (N = 8, RMSE = 0.59 m, MAPD = 26%). This work demonstrates the value of merging in situ ZSD with high spatial resolution remote sensing estimates for improved coastal water quality monitoring.

This baseline study highlights the ²¹⁰Po and ²¹⁰Pb concentration in seven macroalgae species from the northern Gulf that are frequently washed ashore during the bloom season from February to April. The highest concentrations of ²¹⁰Po and ²¹⁰Pb were 2.947 ± 0.032 and 1.057 ± 0.145 Bq kg⁻¹ wwt, respectively, in brown algae Sargassum boveanum, and the lowest in green algae Ulva prolifera with 1.533 ± 0.058 and 0.170 ± 0.069 Bq kg⁻¹ wwt, respectively. A ²¹⁰Po enrichment was observed in both brown and green algae species, with the ²¹⁰Po/²¹⁰Pb ratio being >1 for all the samples. The mean concentration of ²¹⁰Po in all species was an order of magnitude higher than ²¹⁰Pb, and the difference in mean concentration is statistically significant (p < 0.001). At the same time, the mean concentration of dissolved ²¹⁰Po and ²¹⁰Pb in seawater was 0.28 ± 0.01 and 0.52 ± 0.01Bq m⁻³ with a ²¹⁰Po/²¹⁰Pb ratio of 0.54 ± 0.02 indicating that ²¹⁰Po was absorbed from water and more concentrated by macroalgae. The measured concentration factor (CF) for ²¹⁰Po in these macroalgae for the northern Gulf varied between 5 × 10³–1 × 10⁴, higher than the IAEA recommended value of 1 × 10³ which suggests that a revision of that value may be needed. The field derived CFs for ²¹⁰Pb vary between 3 × 10²–1.8 × 10³, comparable to the ICRP recommended value of 2 × 10³.

Global aquaculture discharges are typical anthropogenic carbon and nutrient sources to nearby mangrove forests. In this study, we quantified total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) stocks (0–50 cm) in soils from three sites of Kandelia obovata forests with different shrimp-pond discharge histories of 0, 8 and 14 years (i.e. 0DK, 8DK and 14DK, respectively). Results showed that shrimp pond effluents increased soil TOC densities at 8DK. TP densities gradually increased with discharge histories, whereas TN densities were similar between 8DK and 14DK. Besides, IsoSource analyses demonstrated that the high δ¹³C values of shrimp pond effluents contributed 30.00%–33.60% of mangrove soil TOC at 0–10 cm depth. These results suggested that shrimp pond effluents altered soil TOC, TN and TP stocks and added carbon source to mangrove soils, which was related to discharge histories and soil depth. Moreover, the discharge changed carbon and nutrient patterns, which warrant attention.

Often, beach litter monitoring strategies focus only on macro-litter (>25 mm) and do not distinguish between litter left at beaches and litter washed up onshore. We tested inexpensive and user-friendly methods to examine meso-litter (5–25 mm) and large micro-litter (2–5 mm) washed up on German sandy beaches and evaluated our methods regarding the requirements of the Marine Strategy Framework Directive. With a sieve accumulation zone monitoring method, tested 41 times, we found 0.2–21.2 litter pieces/m² (⌀ 5.3 pieces/m² ± 8.9). With a bare eye accumulation zone monitoring method, tested 10 times, at other beaches, 9.1–65.6 litter pieces/m² (⌀ 31.8 pieces/m² ± 15.7) were found. Both methods are inexpensive, useful for volunteers, and can be carried out quickly, but are also limited, as they cannot be used regularly. A tested webcam and a modified Braun-Blanquet method turned out to be less suitable.

Heavy metal pollution is a serious environmental problem. Up to date, research regarding distribution, accumulation and potential risk assessment of metals in aquatic organisms in Laizhou Bay, China is scarce. This study aims to investigate metals in aquatic organisms in this region. The results demonstrated that great variability of metals content occurred among species and sampling locations. Fe was the most abundant metal, followed by Zn, Mn, Cu, Ni, Cr, Cd and Pb. Overall, shellfish and crab displayed high enrichment ability compared with fish and shrimp. There was no significant correlation between metals and samples weight, δ13C and δ15N values. Principal component analysis (PCA) indicated that metals in samples were mainly derived from anthropogenic activities. Health risk of metals was evaluated on the basis of estimated daily intake (EDI) and target hazard quotient (THQ) values. The results indicated that metals in studied seafood had no significant risks for ordinary consumers.

In this study, 16 polycyclic aromatic hydrocarbons (PAHs) were detected in surface sediments of the Subei Shoal. Eleven of the 16 PAHs were detected, namely, Nap, Fl, Phe, Flu, Pyr, BaAnt, Chr, BaFlu, BaPyr, Ind-1,2,3-cdPyr, and BghiPer, and the remaining five (Acy, Ace, Ant, BkFlu, and DBahAnt) were not detected. Total PAH concentrations ranged from <DL to 25.24 ng/g dw, with an average of 5.88 ng/g dw. The highest concentrations were found in the intermediate sections (stations 6–1), followed by those in the northernmost regions (stations 9–5). The lowest concentrations were found in the south of section 2. High-molecular-weight PAHs (4 and 5 rings) were found to be dominant, constituting 70% of the PAHs tested. Principal component analysis showed that PAHs in sediments came mainly from coal combustion, transportation (oil combustion), coke processing, and petroleum sources. Both effect range low/effect range median values and mean effects range–median quotient showed that PAHs were present at a low toxicity risk level in the Subei Shoal.

Heavy metal elements, including Zn, Cd, As, Ni, Cu, Pb and Cr, were detected in soils (no deeper than 75 m) from newly reclaimed zones of Shanghai, China. The Zn concentration exceeded soil quality limits. The Zn contamination was tested in both dredger fills and sedimentary layers (①₃–₃, ②₃, ④ and ⑤₁–₁). However, it was not detected in layer ⑤₁–₂–⑨. PCA and HCA analysis show that exogenous Zn probably was the contaminant source of dredger fills before the fills were dredged from the neighboring waters. Stochastic heterogeneity of the dredger fills affects the Zn-depollution remarkably. Numerical simulations show both acid precipitation and widespread drainage channels in the zones contributed to Zn-decrease in the dredger fills no deeper than 1.2 m. Acid rainstorms work better than acid constant precipitation in Zn-remediation for layers below 0.4 m. To remove Zn contamination in deep dredger fills, un-consolidation of the fills should be utilized.

This study provides new insight towards the effects of heavy metal contamination on sulfate-reducing bacteria (SRB) in mangrove ecosystem. We investigated SRB communities in mangrove sediments (0–30 cm depth) from Futian, Xixiang and Shajing mangrove wetlands in Shenzhen, China, with different heavy metal contamination levels. The results showed that SRB community abundance (1.71 × 107–3.04 × 108 dsrB gene copies g−1 wet weight sediment) was depth-related and significantly correlated with Cd and Ni concentrations. The α-diversity indices of SRB community (Chao1 = 21.25–84.50, Shannon = 2.31–2.96) were significantly correlated with Cd level in mangrove sediments. Desulfobacteraceae, Desulfobulbaceae and Syntrophobacteraceae acted as major SRB groups in mangrove sediments, and Syntrophobacteraceae was most sensitive to metal contamination. UniFrace clustering analysis revealed that SRB community structure was influenced by the heavy metal concentrations. Moreover, redundancy analysis indicated that Cd and total phosphorus were the major environmental factors affecting the SRB structure in mangrove sediments.

The present study intends to assess the metal pollution of a eutrophic coastal lagoon, analyzing the long-term and actual metal content in surface sediments, suspended particles, aquatic macrophyte and fish species, and the loads emitted from natural processes and anthropogenic sources, including the relative emission of domestic untreated sewage. Distribution indicated contamination of suspended particles with Cd and the predominance of Pb in the bioavailable form in surface sediments which may explain Cd and Pb contamination in fish. Domestic untreated sewage was an important source of Cu and due to the lagoon's management, this source may be increasing the metal content in the lagoon's surface sediments. Soil loss, atmospheric deposition and solid waste disposal also contributed to metal inputs to the lagoon. Extensive contamination has been prevented by the lagoon's management such as sandbar opening. Metal retention within the watershed soils reduce the effective metal transference and lagoon pollution.

Previous studies on PCDD/Fs and PCBs in dugong (Dugong dugon) blubber reported unexpectedly elevated TEQ levels. This study analysed archived blubber, muscle, liver and faeces obtained from dugongs from two areas along the Queensland coast. All samples showed detectable levels of PCDDs and PCBs, while PCDFs were consistently near or below LOQ. PCDD levels in dugongs contributed to a large proportion (<95%) of sum TEQ levels in all tissues (blubber: 6.7–38 pg g−1 lw, muscle: 5.7–96 pg g−1 lw, liver: 3.3–42 pg g−1 lw, faeces: 203 pg g−1 lw). Liver/blubber tissue ratios show that PCDDs are preferentially accumulated in the liver with higher degree of chlorination. The same trend was not so obvious with PCBs, which occasionally showed higher hepatic sequestration of lower chlorinated PCBs such as PCBs 28 and 77. PCDD congeners were dominated by OCDD which is similar to the profiles from the dugongs' food source, namely sediment and seagrass.