Anthropogenic litter is present in all marine habitats, from beaches to the most remote points in the oceans. On the seafloor, marine litter, particularly plastic, can accumulate in high densities with deleterious consequences for its inhabitants. Yet, because of the high cost involved with sampling the seafloor, no large-scale assessment of distribution patterns was available to date. Here, we present data on litter distribution and density collected during 588 video and trawl surveys across 32 sites in European waters. We found litter to be present in the deepest areas and at locations as remote from land as the Charlie-Gibbs Fracture Zone across the Mid-Atlantic Ridge. The highest litter density occurs in submarine canyons, whilst the lowest density can be found on continental shelves and on ocean ridges. Plastic was the most prevalent litter item found on the seafloor. Litter from fishing activities (derelict fishing lines and nets) was particularly common on seamounts, banks, mounds and ocean ridges. Our results highlight the extent of the problem and the need for action to prevent increasing accumulation of litter in marine environments.

With increasing demand for mineral resources, extraction of polymetallic sulphides at hydrothermal vents, cobalt-rich ferromanganese crusts at seamounts, and polymetallic nodules on abyssal plains may be imminent. Here, we shortly introduce ecosystem characteristics of mining areas, report on recent mining developments, and identify potential stress and disturbances created by mining. We analyze species' potential resistance to future mining and perform meta-analyses on population density and diversity recovery after disturbances most similar to mining: volcanic eruptions at vents, fisheries on seamounts, and experiments that mimic nodule mining on abyssal plains. We report wide variation in recovery rates among taxa, size, and mobility of fauna. While densities and diversities of some taxa can recover to or even exceed pre-disturbance levels, community composition remains affected after decades. The loss of hard substrata or alteration of substrata composition may cause substantial community shifts that persist over geological timescales at mined sites.

Microplastics contaminate environments worldwide and are ingested by numerous species, whose health is affected in multiple ways. A key dimension of health that may be affected is the gut microbiome, but these effects are relatively unexplored. Here, we investigated if microplastics are associated with changes in proventricular and cloacal microbiomes in two seabird species that chronically ingest microplastics: northern fulmars and Cory’s shearwaters. The amount of microplastics in the gut was significantly correlated with gut microbial diversity and composition: microplastics were associated with decreases in commensal microbiota and increases in (zoonotic) pathogens and antibiotic-resistant and plastic-degrading microbes. These results illustrate that environmentally relevant microplastic concentrations and mixtures are associated with changes in gut microbiomes in wild seabirds.

The impact of bottom trawling on cold-water corals (CWC) has been thoroughly studied and shown to be long-lasting; however the effects of bottom longlining on CWC ecosystems have received little attention. The present paper identifies the principal CWC species landed by bottom longlining in Faial (Azores) from 150 to 600 m depth. Data were obtained from a survey of 297 landings during four months coupled with 16 interviews with fishermen. A distinction was made among corals brought on deck directly entangled in the fishing gear (primary by-catch) from corals brought up associated with other larger CWC species or rocks (secondary by-catch). Forty-five (15.2%) of 297 fishing trips surveyed landed coral specimens. The survey recorded 39 different CWC taxa in the by-catch, belonging to five different orders (Scleractinia, Alcyonacea, Antipatharia, Zoanthidea and Anthoathecata). Secondary by-catch included a larger number of species but the total number of corals was in the same order of magnitude for both groups. The taxa most frequently encountered wereLeiopathesspp., Errina dabneyiand Dendrophyllia sp. CWC taxa in the by-catch were mostly medium size (10–60 cm), 3-dimensional and branched colonies. Local ecological knowledge of fishermen confirmed that the corals recorded were representative of their past experience and also revealed a general agreement that there has been a decrease of CWC by-catch on traditional fishing grounds. Corals are common by-catch in bottom longline fisheries around the Azores and so conservation measures may be required.