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.

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The recent revision on the taxonomic status of Lepadogaster lepadogaster resulted in the division of this species into L. lepadogaster and L. purpurea, the clarification of each species' distribution ranges and the elimination of L. zebrina (now in synonymy with L. lepadogaster). This new taxonomic status led to the need of clarifying the early development of the two species. Embryonic development lasted 21 days in L. purpurea at a mean temperature of 14.2°C, and 16 days in L. lepadogaster at a mean temperature of 16.5°C. Newly hatched larvae of both species measured 5.2 mm, had the mouth and anus opened, pigmented eyes and almost no yolk. At hatching and throughout development the two species can be distinguished by the ventral pigmentation which is absent in L. purpurea. The change to a benthic mode of life was gradual in both species, with larvae increasingly spending more time close to the bottom until definitely settling. Larval development lasted 33 days in L. purpurea at a mean temperature of 14.6°C and 18 days in L. lepadogaster at a mean temperature of 16.5°C. Locomotion and foraging behaviours are described for both species. L. lepadogaster showed a higher frequency of swimming and foraging behaviour when compared with L. purpurea.

Hexactinellids or glass sponges constitute a predominantly deep-sea sponge group typically occurring at bathyal and abyssal depths. Some species form dense populations along the European and African continental slope but the distribution and extent of these populations remains ill known and the driving factors behind their occurrence poorly understood. Here we report an aggregation of the hexactinellid sponge Poliopogon amadou Thomson, 1878 at 2700 m depth on the Great Meteor seamount, a large seamount located southern of the Azores archipelago. A description of the species, along with scanning electron microscopy of its spicules, is provided.