Methods for sampling, analysis and interpretation of fresh and saltwater microplastics and anthropogenic microfibers have improved since 2004, but techniques for reducing and monitoring procedural contamination are still limited. Quantifying the amount of procedural contamination introduced to samples improves the robustness of counts of microplastics and anthropogenic microfibers in the environment. This pilot study investigates procedural contamination introduced into water samples when rigorous QA/QC anti-contamination protocols are used and removed. Procedural contamination accounted for 33.8% of the total microfibers and microplastics found in samples when protocols were used (n = 81), but 70.7% when they were not (n = 8). With the use of extensive control sampling and full characterization of samples (morphological, optical and chemical) it was possible to identify the predominant sources of contamination (crew clothing) and make recommendations for anti-contamination and procedural contamination identification/reduction protocols for shoreline and small/medium sized vessel sampling for microplastics and anthropogenic microfibers.

Water quality of the Great Barrier Reef (GBR) is determined by a range of natural and anthropogenic drivers that are resolved in the eReefs coupled hydrodynamic - biogeochemical marine model forced by a process-based catchment model, GBR Dynamic SedNet. Model simulations presented here quantify the impact of anthropogenic catchment loads of sediments and nutrients on a range of marine water quality variables. Simulations of 2011–2018 show that reduction of anthropogenic catchment loads results in improved water quality, especially within river plumes. Within the 16 resolved river plumes, anthropogenic loads increased chlorophyll concentration by 0.10 (0.02–0.25) mg Chl m⁻³. Reductions of anthropogenic loads following proposed Reef 2050 Water Quality Improvement Plan targets reduced chlorophyll concentration in the plumes by 0.04 (0.01–0.10) mg Chl m⁻³. Our simulations demonstrate the impact of anthropogenic loads on GBR water quality and quantify the benefits of improved catchment management.

Perfluorinated alkyl substances (PFASs) were determined in marine plastic litter (MPL) on six beaches of central Chile. MPL was characterized physically and chemically, showing an abundance of macroplastic (size >2.5 cm). The polypropylene (PP) (47%) was the predominant polymer found. The Desembocadura beach, located at the mouth of the Biobio River, recorded the highest abundance of MPL (3.7 items m⁻²). PFAS detected (n = 15/21) ranged from 279 to 1211 pg g⁻¹ and accounted for MeFOSE (46%) > PFHxS (14%) > PFPA (11%) > PFBS (6%) > PFOA (4%) and > PFOS (4%). Long-chain PFAS were prevalent, which can be metabolically degraded into PFOS (new POPs). This study i) highlights the need to further investigate the occurrence of chemicals in the MPL to reduce their impact on the environment; and ii) points out the need to improve future coastal management strategies for the elimination of solid waste along the coast of the country.

Chlorophyll a fluorescence is increasingly being used as a rapid, non-invasive, sensitive and convenient indicator of photosynthetic performance in marine autotrophs. This review presents the methodology, applications and limitations of chlorophyll fluorescence in marine studies. The various chlorophyll fluorescence tools such as Pulse-Amplitude-Modulated (PAM) and Fast Repetition Rate (FRR) fluorometry used in marine scientific studies are discussed. Various commonly employed chlorophyll fluorescence parameters are elaborated. The application of chlorophyll fluorescence in measuring natural variations, stress, stress tolerance and acclimation/adaptation to changing environment in primary producers such as microalgae, macroalgae, seagrasses and mangroves, and marine symbiotic invertebrates, namely symbiotic sponges, hard corals and sea anemones, kleptoplastic sea slugs and giant clams is critically assessed. Stressors include environmental, biological, physical and chemical ones. The strengths, limitations and future perspectives of the use of chlorophyll fluorescence technique as an assessment tool in symbiotic marine organisms and seaplants are discussed.

The present study documents, for the first time, the ingestion of microplastics (MPs) by Longnose stingrays in the Western Atlantic Ocean. We examined 23 specimens of Hypanus guttatus from the Brazilian Amazon coast and found microplastic particles in the stomach contents of almost a third of the individuals. Fibers were the most frequent item (82%), blue was the most frequent color (47%) and Polyethylene Terephthalate (PET) was the most frequent polymer recorded (35%), as identified by 2D imaging - Fourier Transform Infrared (FTIR). The ingestion of microplastics by Longnose stingray has not been previously recorded. The findings of the present study thus provide an important baseline for future studies of microplastic ingestion by dasyatid rays and other batoid species in the Atlantic Ocean, and contribute to the broader understanding of the spatial and temporal dimensions of the growing problem of plastic pollution in aquatic ecosystems and organisms.

The reduction in benthic light from natural sediment resuspension events, dredging activities and clouds was quantified over multiple time periods (days to weeks) from a 3-year in-situ field study in the inshore turbid-zone coral communities of the Great Barrier Reef. The results were then used to examine the tolerance levels of three coral species and a sponge to light reduction and associated changes in spectral light quality (in conjunction with elevated sediment concentrations) in a 28-day laboratory-based study. All species survived the exposures but sub-lethal responses involving changes in pigmentation, lipids and lipid ratios were observed. A pocilloporid coral was the most sensitive taxon, with a 28-d EC10 value for bleaching (dissociation of the symbiosis) of 2.7 mol photons m² d⁻¹. The possibility of such light reduction levels occurring naturally and/or during maintenance dredging activities was then examined using the 3-year in-situ field study as part of a risk assessment.

The development of toxic compounds in sediment and macrobenthos species in Hangzhou bay (2003–2015) was evaluated. Concentrations were compared to Chinese sediment quality guidelines (CN-SQG) and risk assessed by the ecological risk index (ERI) and t-Distributed Stochastic Neighbour Embedding (t-SNE). To study seafood contamination, sediment and swimming crabs were collected. Chromium, copper, and arsenic exceeded CN-SQG. Organic contaminants did not exceed CN-SQG; however, t-SNE revealed a negative relationship with benthic species numbers. Since 2003, half of the benthic species have disappeared. Species sensitive to contamination were not observed after 2003–2007, while crustacea species are more tolerant: cadmium levels in crabs were 5–17 times those in the sediment, demonstrating strong bioaccumulation. These results suggest that metals and organic pollutants pose ecological and seafood risks. For good environmental management in HZB, it is important to analyze sediment, benthic biota, and seafood species for compounds known to pose toxic risks.

Oil-sediment aggregation is an important transport and transformation process of spilled oil, which has been considered as a pathway of spill remediation. This work focused on the individual performance of dispersed oil and sediment during the aggregation process. Dispersion of three oils was first tested and validated in a water tank. An approach of estimating the mass variation of the sediment that has participated in forming the oil-sediment aggregates (OSAs) has been developed by density analysis. Results indicated that the density of the formed OSAs increases during the aggregation. In the context of remediation, it takes longer for sediment to reach equilibrium than for dispersed oil, especially under high mixing energy at a large sediment concentration, which results in the formation of dense OSAs, as well as high aggregation degree and rate. Roncador oil possesses a relatively high capability of capturing sediment to form dense OSAs, especially at an initial sediment concentration of over 150 mg/L. Oil sinking efficiency and the characteristic change rate of aggregated oil mass seem to be proportional to oil dispersion efficiency, and decrease with the mean size of dispersed oil droplets. The process of aggregation can further promote the dispersion of oil into water column. This study also provides fundamental data for the formation kinetics of OSAs.

Investigation of nutrients in the water column and phytoplankton pigments in recently formed modern sediments (0–5 cm) was carried out in Cochin estuary. The anthropogenic impacts were assessed using nutrients, nitrate, and phosphate in combination with phytopigments in sediments. The nitrate and phosphate concentration during the study ranged from 0.81 to 42.53 μmol/L and from 0.1 to 5.81 μmol/L, respectively. The mean values of the pigment showed the following order: zeaxanthin (791.53 ng/g) > lutein (347.57 ng/g) > fucoxanthin (335.30 ng/g) > pheophytin (308.84 ng/g) > pheophorbide (172.06 ng/g) > chlorophyll a (161.63 ng/g). The increase in the concentration of zeaxanthin indicated the presence of cyanobacteria, associated with eutrophication. Correlation analysis revealed that water column nutrients have a strong relationship between fucoxanthin and lutein, indicating the coexistence of diatoms and prasinophytes in the sampling sites. The principal component analysis showed positive loading of nutrients concomitant with pigment fucoxanthin and lutein, thus establishing that nutrient input controls the phytoplankton biomass of this estuary.