The Azores
Morton, B.; Britton, J.C. (2000). The Azores, in: Sheppard, C.R.C. (Ed.) Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. pp. 201-219
In: Sheppard, C.R.C. (Ed.) (2000). Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. Pergamon: Amsterdam. ISBN 0-08-043207-7. XXI, 934 pp., meer
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| Beschikbaar in | Auteurs |
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Documenttype: Revisie
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| Abstract |
The nine islands of the Azores, with a total land area of 2233 km², command a marine Exclusive Economic Zone of more than one million km². With a total population of only ~249,000, these remote islands, rising steeply from oceanic depths >4000 m on both sides of the mid-Atlantic Ridge, should be models of marine environmental health. Climatic changes and the prevailing pattern of ocean circulation around the islands, however, bring trace levels of emission gasses and water-borne contaminants. With little industry and a sparse population, inshore pollution levels are low. Recreational beaches are classified as either good or satisfactory and most significant contaminant levels are restricted to major boat harbours. TBT-induced imposex in the predatory dogwhelk Stramonita haemastoma was, for example, only detectable at the popular trans-Atlantic yacht harbour at Horta, Faial. Similarly, heavy metal levels were generally higher in the harbour of the most populous city (65,000) of Ponta Delgada on São Miguel. Most heavy-metal research has focused on seabirds, it being demonstrated, for example, that there has been a three-fold increase in mercury contamination over the last 100 years in the North Atlantic. High levels of mercury have also been recorded from cephalopods and mesopelagic fishes. Metal levels have also been examined in intertidal amphipods and barnacles and shown to be high near the harbour at Ponta Delgada and in some remote areas, as for example, near a coastal thermal spring. Cadmium levels of 167 µg g-1 in Chthamalus stellatus are the highest ever recorded, worldwide, for a barnacle but this represents natural bioavailability from the native lava rock. Elsewhere, such Cd levels have been shown to influence gastropod growth adversely. It seems clear that in the Azores natural leaching is more important than pollution in defining the health of local marine communities. However attractive the concept, therefore, it is unlikely that the Azores can serve as a 'clean', 'control' site for pollution studies elsewhere. The greatest human threats to native marine communities are the introduction of exotic species and excessive exploitation of some fisheries resources. Regarding the former, the Azores have fared much better than other island groups, but with increasing interactions with world markets, the potential for detrimental exotic invasions remains high. Rats and feral cats have had profound adverse effects on seabird populations and Monteiro et al. (1996) have documented the decline in seabird numbers in the Azores. Over-exploitation of certain inshore fisheries, especially limpets and, perhaps, octopus, produces equally severe impacts on community ecology. |
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