Scientists from CCMAR (University of the Algarve) and Oceana have found an abundance of litter in the São Vicente submarine canyon, located in the south west of Portugal. The article[i] outlines how the authors analysed three immersions and highlighted the existence of 115 samples of litter, the majority fishing gear. This type of waste does not decompose easily in deep areas and is expected to continue growing.
"Fishing is a very important socio-economic activity in this region. Sadly, what has been observed in the St. Vincent canyon is similar to many other parts of the world where fishing is the main activity: the methods of control and minimization of losing fishing gear are currently ineffective. The long-term effects of lost fishing gear and other forms of marine debris on benthic communities are still poorly understood, particularly in the deeper parts of the ocean. These deep sea habitats, many of them still little studied, are home to sensitive, slow growth species of that can be quite vulnerable to environmental disturbances," said Frederico Oliveira, CCMAR scientist.
The São Vicente submarine canyon can be found 12 kilometres off the Portuguese coast, in front of Sagres, and is 120 kilometres long. The study published in Marine Pollution Bulletin is based on three ROV (remote underwater vehicle) immersions carried out in 2011, to depths between 93 and 553 metres. In total, the scientists analysed over nine hours of recorded material.
“Practically 9 out of every 10 waste samples discovered in the São Vicente submarine canyon are abandoned lines and nets. This is very worrying because they are manufactured from resistant synthetic materials and the processes of decomposition are very slow at such depths. That’s why, either measures are adopted to avoid the loss of fishing gear or the quantity of litter will continue to increase in the coming years,” asserts Ricardo Aguilar, research director at Oceana in Europe.
Almost a third of all waste documented covered part of the sea bed or directly affected the fauna, with numerous cases of coral, gorgonians, sea urchins and crinoids caught up in lost fishing equipment. Moreover, it stressed how 80.8% of the finds were made in rocky areas; waste gets caught more easily in these habitats, which house greater diversity because they act as a substratum to which organisms such as coral and sponges get attached.
Oceana and CCMAR have collaborated on previous occasions. In 2012, scientists from this organisation set out on an Oceana Ranger expedition, contributing to the discovery of a field of crinoids in front of the Algarve, a type of habitat in which diverse fish species normally reproduce. They have also worked together to document sea beds in the Gorringe Ridge and communities of coral in the south of the Iberian Peninsula.
[i] Oliveira, F., et al. Marine litter in the upper São Vicente submarine canyon (SW Portugal): Abundance, distribution, composition and fauna interactions. Mar. Pollut. Bull. (2015), http://dx.doi.org/10.1016/j.marpolbul.2015.05.060