How trawling is destroying our deep-sea coral gardens and the planet’s oldest living creatures

Date: August 24, 2017

Source: International Business Times
Author: Michelle TaylorChris Roterman

The mysterious habitats of the deep are being destroyed before we know anything about them.

Given its vastness and apparent remoteness from our everyday lives, the deep sea has been widely considered protected from the impacts of the human era, known as the Anthropocene. This, unfortunately, is not true.

For many decades, the deep sea has been an ‘out of sight, out of mind’ rubbish dump. Munitions, waste, lost ships and shipping containers, radioactive waste and sewage have all been disposed of in the deep sea.

Our knowledge of the full extent of deep-sea pollution is far from complete, although it accrues yearly. Recently microplastics have been found in deep-sea sediment samples – some of which are an extraordinary distance (2,800 km) from major pollution sources.

The impact of such pollution on deep-sea animals is unclear. In addition, over the last century humans have been increasing the harvest of biomass from the deep sea. The most damaging form of this harvesting – bottom trawl fishing – has expanded continually since the 1950s and now commonly occurs at depths approaching 2,000m.

To give an idea of the destructive potential of trawling, imagine flattening whole forests just to collect the birds that live in it. This is effectively what happens to deep-sea coral gardens, which are biodiversity hotspots. Wasteful doesn’t even begin to describe the effects of trawling on these habitats where corals can live for over 4,500 years, making them some of the oldest living creatures on the planet.

Unsurprisingly there is little evidence of coral forest recovery over decadal time scales. Bottom trawling is global and dwarfs other physical impacts at comparable depths. Nearly 2 million square kilometres of the seabed under signed exploration contracts. The potential of lucrative mineral extraction from the deep sea looms large. Manganese nodules, cobalt-rich crusts and massive polymetallic sulphide deposits could all be harvested, but we have no idea of what the impacts will be.

All the activities listed above are happening despite a relative dearth of fundamental knowledge about deep-sea organisms and the environment they inhabit. In effect, exploitation of deep-sea resources has outpaced scientific data-gathering and exploration.

Basic information about species and their habitats, such as the extent of migration or isolation, reproduction and development, are lacking beyond a few species. Yet this knowledge is vital if deep-sea habitats are to be conserved and resources managed responsibly.

In particular, a detailed understanding of species ranges, and how constituent populations or subpopulations are maintained through dispersal is critical to determining the size of conservation units, effective marine protected area design, and any future recovery from impacts.

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Posted on Categories Fisheries ScienceTags