Bioindicators are useful for determining nutrient regimes in marine environments, but their ability to evaluate corals reefs in different ecological states is poorly understood. The precision, availability and congruency of eight potential bioindicators (brown macroalgae, green macroalgae, turf algae, cyanobacteria, soft corals, zoanthids, sponges, and sediment) and their stable isotopic and elemental signatures (δ¹⁵N, δ¹³C, %N, %C, and C:N Ratio) were assessed across 21 reefs in the Inner Seychelles. The coefficient of variation (CoV) for δ¹⁵N showed that green and brown macroalgae were highly precise (2.47 ± 0.95, n = 11; 4.68 ± 1.33, n = 16, respectively), though were less common on coral-mortality reefs relative to macroalgal-dominated ones. Zoanthids were also highly precise for δ¹⁵N (2.98 ± 1.20), but were more readily available regardless of reef state (n = 18). Congruency was low among these indicators, suggesting that different physiological mechanisms for nutrient processing have a stronger influence on a bioindicator's effectiveness than reef state.

This study investigated the accumulation of debris at four sites, namely, Gebeng, Batu Hitam, Cherok Paloh, and Air Leleh, along the Pahang coastline, Peninsular Malaysia from March 2019 to February 2020. Plastic was the dominant debris (86.1%) and followed by cloth/fabric-based debris (6.0%), processed lumber debris (3.3%), rubber (2.7%), glass (1.5%), and metal (0.4%). The land-based debris (82.0%) was the major source of the deposition of marine waste. A statistically significant relationship was found between the seasonal variation and marine debris density in tidal and seasonal current along the Pahang coastline. In general, the Northeast Monsoon season had a higher amount of debris than the Southwest Monsoon season.

The present study reports a dense bloom of the marine-diatom Hemidiscus hardmanianus observed off the Tuticorin coast in the Gulf of Mannar (GoM), India. The surface water discoloration (pale green) was observed during a coastal survey conducted in the initial period of the northeast monsoon (October 2018). The bloom extended over an area of approximately 5 km² around the Tuticorin harbor. Distribution and relative abundance of the phytoplankton and zooplankton species together with the water quality and Chlorophyll-a were studied in the area of bloom. H. hardmanianus density was maximum (10.57 × 10⁴ cells L⁻¹) in the bloom site, which was almost 97% of the total phytoplankton population. The present report is the first record of H. hardmanianus bloom in the Gulf of Mannar. The chain-forming diatom Biddulphia biddulphiana was also observed in strong numbers (802 and 432 cells L⁻¹), which has been rarely reported from the Indian coastal waters.

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.

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.

The persistence and transformation of water soluble chemical constituents derived from surface oil from the 2015 Refugio Oil Spill and from a nearby natural seep were evaluated under simulated sunlight conditions. Photoirradiation resulted in enhanced oil slick dissolution, which was more pronounced in spill oil compared to seep oil. Nontargeted analysis based on GC × GC/TOF-MS revealed that photoirradiation promoted oil slick dissolution, and more water soluble compounds were released from spill oil (500 compounds) than from seep oil (180 compounds), most of them (488 in spill oil and 150 in seep oil) still persisting in solution after 67 days of photoirradiation. First-order degradation rate coefficients of humic-like water soluble constituents were found to be 0.26 day⁻¹ and 0.29 day⁻¹ for irradiated spill and seep samples, respectively. The decreases in humic-like fluorescence, specific UV absorbance, and aromatic compounds without corresponding decreases in DOC concentration support indirect photochemical transformation in addition to complete photomineralization.

Coastal pollution levels in Todos Santos Bay (TSB) recreational beaches have increased in recent years due to the uncontrolled disposal of wastewater and pollutants to the coast by human activities (urbanization and tourism). In this work, the concentration of water quality parameters along the coast of TSB was evaluated from February 2012 to January 2013. Sampling was carried out at monthly intervals on 29 beach locations. Results showed that the maximum values of all parameters were always found close to the treated wastewater discharge area at Arroyo El Gallo station. Temporally, both nutrients and biochemical oxygen demand reached notably high levels in winter-spring and close to wastewater discharges. During summer, maximum counts of total coliforms and parasite eggs were detected close to wastewater discharges. Overall, our study provides a diagnostic approach on the spatiotemporal variability of water quality parameters for future studies along the coastal waters of TSB.

Clinus superciliosus was collected for element analysis from six localities along the South African west and south coasts. Concentrations in muscle and liver were determined, considering size and sex. No significant positive correlation between size and concentrations were detected, except for Mn and Sn in liver from Simons Town marina, while no significant differences in sex were detected. The majority of element concentrations were significantly higher in fish from Tsitsikamma in the Garden Route and the small town Chintsa, while some concentrations were significantly higher in muscle at Simons Town marina. Land-use activities had a limited role in element bioaccumulation in klipfish. Element concentrations were influenced by large scale oceanographic processes (currents; upwelling) and localised seasonal geogenic derived run-off. Limited data on element accumulation patterns of intertidal fish species in South Africa, highlights the need for long-term monitoring and further studies on different resident and transient intertidal fish species.