Climate change effects such as ocean acidification (OA) are known to affect the trace metal distribution. This experimental study provides the first data on ²⁰⁹Po uptake rates and ²¹⁰Po concentration in five microalgae species under different pH scenarios. The experiment was conducted in replicates at three pH conditions 8.2, 8.0, and 7.5, representing the current and future climate change scenario as per IPCC RCP8.5. The ²⁰⁹Po uptake in the phytoplankton was highest in Thalassiosira weissflogi, i.e. 83% of the ²⁰⁹Po tracer was taken up at 8.2 pH whereas the lowest uptake was observed in Dunaliella salina equivalent to 20% at 7.5 pH. Similar behavior was observed in ²¹⁰Po concentrations in these microalgae, where ²¹⁰Po ranged between 3.16 ± 0.03 and 11.6 ± 0.04 Bq kg⁻¹ wet weight (ww), with the highest in the Thalassioria weissflogi at 8.2 pH, and the lowest in Dunaliella salina at 7.5 pH. The difference in ²⁰⁹Po uptake and ²¹⁰Po concentration was statistically significant (p < 0.001) both among species and the pH treatments in the order: Thalassiosira weissflogi > Tetraselmis suecica > Chaetoceros muelleri > Isochrysis galbana > Dunaliella salina and 8.2 > 8.0 > 7.5. A higher concentration of ²⁰⁹Po in seawater was measured at low pH condition in all the experimental tanks. Though the data clearly show the difference in concentration and uptake of polonium at different pH conditions, it is not known if lower pH is affecting the adsorbed or absorbed fraction. A detailed investigation will be required to understand the process as it can have a significant effect on biomagnification and marine food chain transfer under changing climatic scenarios.

Plastic litter in nearshore waters is an environmental pollutant with increasing impact on coastal environments. At present, knowledge on basic plastic particle dynamics and the interaction with complex hydrodynamics is lacking. The present laboratory study, performed under controlled wave and wind conditions, demonstrates the dispersion of plastics in shallow waters. The study presents a simple case looking solely at cross-shore particle transport. The results show that both wind and waves as well as plastic properties (shape and density) govern the behaviour of plastic litter in the nearshore zone. Heavy particles behave like natural sand with accumulation in the wave breaking zone. Light particles have varying accumulation along the coastal profile depending on the wind, waves and particle shapes. More extensive characterization remains to be done in future studies.

The extent and type of microplastic (MP) contamination in South African open ocean marine resources is unknown. This study aims to report on MP ingestion in seven commercially targeted fish species from the Agulhas Bank, south of South Africa. MPs were found in all seven species sampled (N = 105) (Trachurus capensis, Merluccius capensis, Merluccius paradoxus, Etrumeus whiteheadi, Scomber japonicus, Chelidonichthys capensis and Argyrozona argyrozona). MPs were recorded in 86.67% fish sampled, with abundances ranging from 2.8 to 4.6 items/fish. Most MPs were fibres (95.14%), black (38.11%) and ranged from 1000 to 500 μm (35.55%) in size. There was no difference in microplastic concentration in relation to distance from shore (p > .05). This is the first record of MPs in offshore fish from southern Africa and the results indicate that more research is required to assess the extent of MP contamination in the region.

To test the model that eco-engineering plant boxes on seawalls sustain water temperatures within thermal tolerance to maximize tropical marine biodiversity, we conducted acute thermal effects (AET) experiments using intertidal gastropods (Nerita albicilla and Littoraria articulata). The AET₅₀ (50th percentile) for N. albicilla (39.6 °C) was higher than L. articulata (32.8 °C). Loggers (Hobo) in boxes on a seawall positioned for full exposure to air temperature at mean sea level (<1.1 m) recorded temperature every 20 min during summer months. Temperature frequency distribution plots were generated for day and night, above and below 1.1 m (which is proximal to mean tide level for the region). Using the AET₅₀, N. albicilla would need to thermoregulate for a lower percentage of time compared to L. articulata regardless of day and night. It is likely that designing eco-engineering improvements to include microclimate refugia are particularly relevant in tropical areas, where extreme environmental conditions mean that scale-specific actions are important components for climate adaptation.

Citizen science programs carried out by volunteers are fundamental for the collection of scientific data on a wide spatial scale. From 2011 to 2018, 468 survey dives were conducted in 172 coastal locations of the Mediterranean Sea through Project AWARE's citizen science program, Dive Against Debris®. During the dives, information was collected on quantity, typology and distribution of seafloor litter in shallow coastal waters. Overall, the observed average density was 43.55 items/100 m² and plastic was largely the dominant material (55% of the total collected items) on basin scale. The most abundant seafloor litter items were plastic fragments with 9.46%, followed by beverage cans (7.45%). Single-use plastic items constituted 33% of the total marine litter. The results of the study can be used to inform policymakers of the European Community towards specific management action to contrast the marine litter in relation to the distribution of the recorded litter category.

Marine litter levels were measured in the stomach contents, hepatopancreas, and gonad tissues of crustacea decapod (Callinectes sapidus Rathbun, 1896; n = 6), a widespread alien species affecting the Lesina lagoon. Results highlight a mean of 2.5 (SD = 1.6) items/animal and indicate the presence of metals fragments (13%) and plastics (13% PE; 6.7% PET) in the stomach contents of collected individuals. No microplastic particles were detected in the hepatopancreas or in muscle tissue, while microplastic fibres (nylon, rayon, polyester) were found present in female specimen gonads. The presence of synthetic fibres in the investigated species reflects the relative contamination level in this habitat type and suggests that the blue crab could be considered a model organism for evaluating the contamination status of the study area.

This article seeks to present a summary of knowledge and thus improve awareness of microplastic impacts on corals. Recent research suggests that microplastics have a variety of species-specific impacts. Among them, a reduced growth, a substantial decrease of detoxifying and immunity enzymes, an increase in antioxidant enzyme activity, high production of mucus, reduction of fitness, and negative effects on coral-Symbiodiniaceae relationships have been highlighted in recent papers. In addition to this, tissue necrosis, lower fertilization success, alteration of metabolite profiles, energetic costs, decreased skeletal growth and calcification, and coral bleaching have been observed under significant concentrations of microplastics. Furthermore, impairment of feeding performance and food intake, changes in photosynthetic performance and increased exposure to contaminants, pathogens and other harmful compounds have also been found. In conclusion, microplastics may cause a plethora of impacts on corals in shallow, mesophotic, and deep-sea zones at different latitudes; underlining an emerging threat globally.

Using simple models, coupled with parameters extracted from published studies, the annual inputs of macro and micro plastics to the Scottish Atlantic Coast and the Scottish North Sea Coast regions are estimated. Two estimates of land-based sources are used, scaled by catchment area population size. The oceanic supply of floating plastic is estimated for wind-driven and general circulation sources. Minimum, typical and maximum values are computed to examine the magnitude of uncertainties. Direct inputs from fishing and the flux of macroplastic onto the seabed are also included. The modelled estimates reveal the importance of local litter sources to Scottish coastal regions, and hence local management actions can be effective. Estimates provide a scale against which removal efforts may be compared, and provide input data for future more complex modelling. Recommendations for research to improve the preliminary estimates are provided. Methods presented here may be useful elsewhere.

Marine litter is recognized as one factor affecting coral health. It causes shading, bleaching, physical damage, necrosis, and mortality. This study provides the first evidence that direct contact by plastic and cotton affects coral health within 60 days. In a controlled aquarium experiment, two common Indo-Pacific scleractinian corals, Porites rus and Pavona cactus, were shaded for 60 days by transparent plastic (polypropylene, PP), dark plastic (PP) and cotton. Cotton disintegrated completely after 30 to 42 days, allowing the corals to recover. Transparent plastic became opaque over time due to microfouling, resulting in bleaching of the affected coral parts. Dark plastic had the strongest effect, including bleaching, necrosis and reduced growth within 60 days. Moreover, the two coral species responded differently to the treatments. This is the first report demonstrating that plastic and cotton litter can affect coral health and even cause partial mortality within 60 days.

A simple stochastic numerical model is applied to obtain the distribution of the terminal settling/rising velocity of a set of MPs particles whose size, shape, and density have their distributions in accordance with field observations and production trends. Results of the direct Monte Carlo simulation are shown to reproduce well the data of laboratory experiments. Distributions of MPs by size and density appear to be more valuable for the final terminal velocity distribution compared to the influence of the distribution by shape. The most “real” of the simulated distributions of the terminal velocity of MPs particles in the ocean has a multimodal shape, slightly different for fresh and saline waters. Multimodality arises from the fact that the terminal velocity depends on several physical parameters simultaneously and thus should be an expected feature of MPs terminal velocity distribution.