The South East Asian Melanesian (SEAM) region contains the world's largest deposits of nickel lateritic ores. Environmental impacts may occur if mining operations are not adequately managed. Effects data for tropical ecosystems are required to assess risks of contaminant exposure and to derive water quality guidelines (WQG) to manage these risks. Currently, risk assessment tools and WQGs for the tropics are limited due to the sparse research on how contaminants impact tropical biota. As part of a larger project to develop appropriate risk assessment tools to ensure sustainable nickel production in SEAM, nickel effects data were required. The aim of this review was to compile data on the effects of nickel on tropical marine, estuarine, pelagic and benthic species, with a particular focus on SEAM.There were limited high quality chronic nickel toxicity data for tropical marine species, and even fewer for those relevant to SEAM. Of the data available, the most sensitive SEAM species to nickel were a sea urchin, copepod and anemone. There is a significant lack of high quality chronic data for several ecologically important taxonomic groups including cnidarians, molluscs, crustaceans, echinoderms, macroalgae and fish. No high quality chronic nickel toxicity data were available for estuarine waters or marine and estuarine sediments. The very sparse toxicity data for tropical species limits our ability to conduct robust ecological risk assessment and may require additional data generation or read-across from similar species in other databases (e.g. temperate) to fill data gaps. Recommendations on testing priorities to fill these data gaps are presented.

Nickel (Ni) and manganese (Mn) are well known for the production of steel and alloys and are commonly found co-occurring in Ni ores. They are metals of environmental concern and contamination in the marine environment is problematic single exposures and in combination. Several studies have documented the effects of single metal exposure on the model anemone E. pallida, but research on the effects of metal mixtures is far less common. This novel study assesses the accumulation and stress effects of Ni and Mn over a 12-d exposure period. E. pallida were exposed in two separate experiments; Ni alone and Ni in combination with Mn, to assess accumulation, along with any effect on the density of symbionts and anemone tentacle length. Anemones were transferred to ambient seawater to assess depuration and recovery over 6 d. Anemone tissue accumulated Ni at a magnitude of five times higher in a mixture of 0.5 mg Ni/L with 2.5 mg Mn/L compared to the same concentration in a single Ni exposure experiment. In both experiments, Ni and Mn preferentially accumulated in the Symbiodinium spp. compared to the anemone tissue, but Ni depuration was more rapid in the mixture than Ni alone exposure. This study reveals a significant reduction in anemone Symbiodinium spp. density after exposure to Ni and Mn mixtures, but not with Ni exposure alone. A significant dose-dependent reduction in tentacle length was observed in anemones after 12 d of the Ni exposure both with and without Mn. The estimated sublethal concentration that causes tentacle retraction in 50% of test anemones (EC50) by Ni was 0.51 (0.25–0.73) mg/L, while in combination with Mn the EC50 was 0.30 mg Ni/L (confidence limits not calculatable). The present data reveals the importance of testing metal effects in combination before establishing safe limits for marine invertebrates.

Plastic debris provides long-lasting substrates for benthic organisms, thus acting as a potential vector for their dispersion. Its interaction with these colonizers is, however, still poorly known. This study examines fouling communities on beached, buoyant and benthic plastic debris in the Catalan Sea (NW Mediterranean), and characterizes the plastic type. We found 14 specimens belonging to two phyla (Annelida and Foraminifera) on microplastics, and more than 400 specimens belonging to 26 species in 10 phyla (Annelida, Arthropoda, Brachiopoda, Bryozoa, Chordata, Cnidaria, Echinodermata, Mollusca, Porifera and Sipuncula) on macroplastics. With 15 species, bryozoans are the most diverse group on plastics. We also report 17 egg cases of the catshark Scyliorhinus sp., and highlight the implications for their dispersal. Our results suggest that plastic polymers may be relevant for distinct fouling communities, likely due to their chemical structure and/or surface properties. Our study provides evidence that biofouling may play a role in the sinking of plastic debris, as the most abundant fouled plastics had lower densities than seawater, and all bryozoan species were characteristic of shallower depths than those sampled. More studies at low taxonomic level are needed in order to detect new species introduction and potential invasive species associated with plastic debris.

Global warming, through increasing temperatures, may facilitate the spread and proliferation of outbreak-forming species which may find favourable substrate conditions on artificial aquaculture structures. The presence of stinging organisms (cnidarian hydroids) in the facilities fouling community are a source of pollution that can cause critical problems when in-situ underwater cleaning processes are performed. Multiple stressor experiments were carried out to investigate the cumulative effect on farmed mussels' functional traits when exposed to realistic stressful conditions, including presence of harmful cnidarian cells and environmental conditions of increasing temperature and short-term hypoxia. Exposure to combined stressors significantly altered mussels' performance, causing metabolic depression and low filtering activity, potentially delaying, or inhibiting their recovery ability and ultimately jeopardizing organisms' fitness. Further research on the stressors properties and occurrence is needed to obtain more realistic responses from organisms to minimize climate change impacts and increase ecosystem and marine economic activities resilience to multiple stressors.

We extensively reviewed the macrozoobenthos around Dokdo, Korea, by analyzing metadata collected over the past 50years. The Dokdo macrozoobenthos was represented by 578 species belonging to 243 families from 12 phyla, where four major phyla (or classes) collectively accounted for 86% to total. Mollusks, arthropods, and cnidarians were semi-equally occurred in intertidal and subtidal areas, while polychetes dominated the subtidal zone. The northern most region of Dokdo had the greatest biodiversity (173 species). The taxonomic distinctness analysis (delta+) indicated a close association between species by region, although the number of species varied greatly. About half of the species did not occur cross the locations (n=20), indicating strong habitat preferences of Dokdo macrofaunal assemblages. Overall, the diversity of Dokdo was greater than that of Ulleung Island (east coast), but comparable to that of the well-developed tidal flats in the western Korean waters, highlighting its status as a biodiversity hotspot.

Mercury (Hg) has a complex biogeochemical cycle in aquatic environments. Its most toxic form, methylmercury (MeHg), is produced by microorganisms. This study investigated how the sea anemone Bunodosoma caissarum affects Hg distribution, methylation and volatilization in laboratory model systems. 203Hg was added to microcosms and its distribution in seawater, specimens and air was periodically measured by gamma spectrometry. MeHg was measured by liquid scintillation. After the uptake period, specimens had a bioconcentration factor of 70 and in microcosms with and without B. caissarum, respectively 0.05% and 0.32% of the initial spike was found as MeHg. After depuration, MeHg in specimens ranged from 0.2% to 2.4% of total Hg. Microcosms with B. caissarum had higher Hg volatilization (58%) than controls (17%), possibly due to Hg2+ reduction mediated by microorganisms associated with its tissues and mucus secretions. Marine organisms and their associated microbiota may play a role in Hg and MeHg cycling.

The Abrolhos Bank is an area of high ecological, socio-economic importance and harbour the richest and most-extensive coral reefs in the South Atlantic. Here we report the discovery of shallow (12–25m depth) reef complex with ten large biogenic structures, intermediate between the typical mushroom-shaped pinnacles of the northern Abrolhos Bank (17°–18° S) and the small patch reefs found on the central/southern coast of the Espírito Santo State (19°–20° S). The newly discovered reefs harbour a relatively rich and abundant reef community, with 73 fish and 14 benthic cnidarian species, including endangered and commercially important ones. We discuss on urgent needs of properly mapping and understanding the ecological functioning of this reef system. Information provided here is a baseline for future impact evaluations, particularly considering the recent worst environmental disaster of Brazil from a dam collapse in Doce river that affected the region.

Coral skeletons record historical trace metal levels in the environment, however, the use of coral skeletal records for biomonitoring studies mostly fail to consider the influence of metal regulation by the living components of coral and subsequent incorporation into the skeleton. This study presents Exaiptasia pallida as a representative of the living components of coral and shows metal partitioning between the tissue and zooxanthellae after chronic exposure to Zn. A strong tendency for preferential accumulation in the zooxanthellae occurred after 32days exposure and Zn concentrations in tissue and zooxanthellae were 123.3±0.7mgkg−1 and 294.9±8.5 respectively. This study shows zooxanthellae density plays an important role in controlling Zn loading in whole anemones and must be considered when investigating metal uptake and loading in zooxanthellate organisms. Further studies that investigate links between aragonite deposition rates and zooxanthellae density and incorporation pathways of metals into skeleton are warranted.