Andrew J. Davies, J. Murray Roberts, Jason Hall-Spencer

Published in Biological Conservation (2007)

Human activity in the deep sea is extending ever deeper, with recent research showing that this environment is more sensitive to human and natural impacts than previously thought. Some deep-water fish stocks have collapsed and fishing methods such as bottom trawling have raised international concern over the habitat damage they cause. It is likely that in its current form, deep-sea fishing is unsustainable. Diminishing reserves of hydrocarbons in shallow water are pushing exploration and production into deeper waters, which may cause damage to little known deep-sea habitats. The deep sea is also proposed as an environment where anthropogenic carbon dioxide could be stored to minimise the effect of its release into the atmosphere. At the same time, rising atmospheric carbon dioxide levels may be altering the chemical equilibrium of the global ocean by lowering pH. Many countries are now beginning to designate some deep-sea habitats as marine protected areas in measures to reduce the damage caused by fishing and other anthropogenic activities. This review examines these current and emerging issues in deep-sea conservation and discusses conservation status and the designation of protected areas. The enforcement of protected areas using satellite tracking of vessels is discussed and applied to an internationally agreed deep-water conservation area, which aims to protect cold-water coral habitats on the Darwin Mounds in the north east Atlantic Ocean.

Full citation

Davies, A.J., Roberts, J.M. & Hall-Spencer, J. (2007) “Preserving deep-sea natural heritage: Emerging issues in offshore conservation and management” Biological Conservation 138: 299-312.

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Andrew J. Davies, Mark P. Johnson, Christine A. Maggs

Published in Marine Ecology-Progress Series (2007)

The role of limpet grazing in preventing the development of algal canopies is a recurrent theme in intertidal ecology. Less is known about interactions of limpets with the long-term dynamics of established canopies. Aerial photographs indicate that intertidal canopy cover has declined over the past 44 yr in Strangford Lough, Northern Ireland. There has been a loss of the previously continuous cover of Ascophyllum nodosum (L.) Le Jolis in the mid-shore. A barnacle dominated assemblage now fills gaps in the A. nodosum canopy. The rates at which barnacle patches become established and grow have increased since 1990. Changes in canopy cover have been accompanied by increases in limpet densities since the 1980s. Measurements between 2003 and 2004 showed no increase in length of A. nodosum fronds when limpets Patella vulgata had access to the algal holdfasts. In contrast, when limpets were experimentally excluded from the holdfasts, there was net frond growth. In the Isle of Man, which is climatically similar to Strangford Lough but has fewer limpets, growth occurred regardless of limpet grazing. The breaking force for A. nodosum declined with increasing local densities of limpets. A. nodosum is a sheltered shore species, potentially vulnerable to changes in wave exposure. There is no evidence, however, that Strangford Lough has become windier over the past 3 decades. Variation in wave exposure among locations within the lough was not related to rates of barnacle patch creation or expansion. Limpet population density has increased following a series of mild winters. Climate change may have a role in causing canopy loss, not by direct effects on the growth of fucoids, but by increasing the severity of grazing through changes to limpet populations.

Full citation

Davies, A.J., Johnson, M.P. & Maggs, C.A. (2007) “Unexpected loss of Ascophyllum nodosum caused by limpet grazing” Marine Ecology-Progress Series 339: 131-141.

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