Site selection and carrying capacity in Mediterranean ... - FAO Sipam

52 GFCM:XXXV/2011/Dma.9
Index (PCI) is a recently proposed method (Tett et al. 2008) that could be used for monitoring of the
water column in enclosed bays that support high production. To our knowledge, this index has not
been evaluated in the Mediterranean.
4.5 Seagrass (Posidonia oceanica) meadows
One of the most important documented effects of aquaculture on biodiversity in the Mediterranean are
those on Posidonia oceanica meadows. It has been documented that sedimentation is the main driver
of the negative environmental changes in P. oceanica meadows and is a strong indicator of fish
farming impacts; the threshold value is 50 mg P m -2 d -1 or 1.5 g organic matter m -2 d -1 (Diaz-Almela et
al 2008). Through coupling measurements of sedimentation rates with distance and sediment quality,
it has been possible to identify a threshold of 400 m as the minimum distance required between the
edge of the farm and P. oceanica meadows (Holmer et al 2008); this should be accompanied by a
monitoring programme to ensure that there is no regression of the meadow.
A European Integrated Project titled ’Thresholds of Environmental Sustainability’
(http://www.thresholds-eu.org/) has addressed the issue of thresholds in relation to coastal processes,
and includes inter alia a case study for thresholds related to fish farming. In this project, some of the
most discussed thresholds were those pertaining to effects on seagrass meadows.
Finally, in the UK Marine SACs Project (2001), as well as in Henderson & Davies (2000), there are
numerous regulatory thresholds and EQSs concerning the accumulation of metals and organic
pollutants in the tissues of farmed fish and in waters and sediments. Most of these, however, have
been designed in the context of public health rather that in an ecosystem perspective, and they have
little relevance to site selection and carrying capacity other than the general requirement for avoidance
of highly polluted zones.
References
Apostolaki E, Tsagaraki T, Tsapakis M, Karakassis I (2007) Fish farming impact on sediments and
macrofauna associated with seagrass meadows in the Mediterranean. Estuarine coastal shelf
Science 75:408-416.
CSTT (1997) Comprehensive Studies for the Purposes of Article 6 of Directive 91/271 EEC. The
Urban Waste Water Treatment Directive. Edinburgh: Scottish Environment Protection Agency
(East Region)
Dalsgaard T, Krause-Jensen D (2006) Monitoring nutrient release from fish farms with macroalgal
and phytoplankton bioassays. Aquaculture, 256 : 302-310
Dean RJ, Shimmield TM, Black KD(2007) Copper, zinc and cadmium in marine cage fish farm
sediments: an extensive survey, Environmental . Pollution 145: 84–95.
Diaz-Almela E, Marba N, Alvarez E, Santiago R, Holmer M, Grau A, Danovaro R, Argyrou M,
Karakassis I, Duarte CM (2008) Rapid seagrass (Posidonia oceanica) decline linked to
Mediterranean fish farm inputs. Marine Pollution Bulletin 56:1332-1342.
Gowen RJ, Bradbury NB (1987). The ecological impact of salmonid farming in coastal waters: A
review. Oceanogr. Mar. Biol. Annu. Rev., 25:563-575.
Gray JS, Wu RS-s, Or YY (2002). Effects of hypoxia and organic enrichment on the coastal marine
environment. Marine Ecology Progress Series, 238: 249-279
Groffman P, Baron J, Blett T, Gold A, Goodman I, Gunderson L, Levinson B, Palmer M, Paerl H,
Peterson G, LeRoy Poff N, Rejeski D, Reynolds J, Turner M, Weathers K, Wiens J (2006)
Ecological thresholds: the key to successful environmental management or an important
concept with no practical application? Ecosystems 9:1–13.
Hansen PK, Ervik A, Schaanning M, Johannessen P, Aure J, Jahnsen T, Stigebrandt A (2001)
Regulating the local environmental impact of intensive, marine fish farming - II. The
52