#benthic litter

A plastic bag found by Victor Vescovo, when he descended nearly 10,927m (nearly 6.8 miles) to a point in the Pacific Ocean's Mariana Trench, one of the deepest part of the ocean.  He also found a sweet wrappers. 

HUGE DUMP FOUND AT THE BOTTOM OF THE MEDITERRANEAN

Images obtained by an underwater exploration robot at the seafloor of the Strait of Messina in Italy, have revealed the largest concentration of garbage ever recorded in deep waters anywhere in the world.  

The photos extracted from ROV video footage show examples of benthic litter accumulations observed within channels in the Messina Strait, including: bricks, tires, clothes and large metallic objects, small  and large mounds, sometimes formed around large items such as a buried car and a sunken boat.

Litter is patchy but pervasive on all surveyed channels, reaching densities up to 200 items in 10 meters of observation. Such impressive amount of litter can be explained by submarine canyons acting as carrier of marine litter from shallow water to the deep sea and a strong urbanization of the coastal area. 

Fishes swiming near plastic debris at the Samandag Cevlik Akcay dive site off the coast of Samandag, in Hatay province, Turkey.

Using an Ocean Infinity AUV (Autonomous Underwater Vehicles), Argentina found the submarine ARA San Juan, the Argentine Navy submarine which was lost on 15 November 2017.  The ARA San Juan had been found at 907 m depth, 500 km off Comodoro Rivadavia, in Southern Argentina.

Source:  Argentine navy @Armada_Arg

A plastic ice bag, likely blown overboard from a fishing vessel found at a depth of ~3,700 m in Enigma Seamount, near the Mariana Trench

Examples of litter observed on the seafloor in the Nordic Seas

A. rubber glove, B. gill net, C. trawl wire, D. Drinking cartons, E: soft plastic, F: Plastic straps, G: Plastic bag.

Marine litter has been found in all marine environments in the Nordic Seas. These ecosystems are under pressure from climatic change and fisheries while the human population is small. According to submarine video transects most of the litter is originated from the fishing industry and plastic is the second most common litter. Background levels are comparable to European records and areas with most littering had higher densities than in Europe.

Photo curtesy of Mareano-IMR

Litter is present in all marine waters around the globe. It consists of several compound classes of which plastic is of special interest because of its high abundance and possible threat to marine organisms. 

Distribution, composition and abundance of large litter items at the sea floor of the North Sea and the Baltic Sea was investigated based on 175 bottom trawls between 2013 and 2015. In the North Sea and in the Baltic Sea plastic represented 80% of the litter items.

Pelagic plastic items are commonly colonized by a diversity of encrusting and fouling animals. Most of these are sessile, hard-shelled or crustose organisms and dominated by moss animals (bryozoans). Also included are barnacles, tube worms, foraminifera, coralline algae, hydroids and bivalve molluscs. 

Aggregations of marine debris can provide habitats suiting the larval and juvenile stages of numerous marine organisms. They may also attract free-living, ocean-roaming predators that often gather under fish aggregating devices, and where others simply sought a protective haven.

Example of colonization and encrustation on plastic debris from the New Zealand coastline: 

(a) Heavy and varied colonization of a plastic slab recovered (note the hard bodied encrustations and soft fleshy epibionts.

(b) Cuttings from a tangled mass of synthetic rope, carrying a cargo of the warm-water Indo-Pacific oyster, Lopha cristagalli, a species that is alien to New Zealand waters. 

(c) Plastic pellet (raw material for manufacture of plastic products) encrusted by the bryozoan Membranipora taberculata.

(d) Small bryozoan colony (Galeopsis mimicus) attached to a frayed plastic flake (arrowed) recovered from a depth of 393 m off the east coast shelf off the South Island. scale bar 0,2 mm.