Abstract
AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 2:105-115 (2012) - DOI: https://doi.org/10.3354/aei00037 Indirect effects of fish cage aquaculture on shallow Posidonia oceanica seagrass patches in coastal Greek waters Konstantine J. Rountos1,*, Bradley J. Peterson1, Ioannis Karakassis2 1School for Marine and Atmospheric Sciences (SoMAS), Stony Brook University, Stony Brook, New York 11794-5000, USA 2Marine Ecology Laboratory, Biology Department, University of Crete, PO Box 2208, 71409 Heraklion, Crete, Greece *Email: krountos@gmail.com ABSTRACT: Over the last 3 decades fish cage aquaculture has increased exponentially in the eastern Mediterranean Sea and has induced various levels of environmental change in coastal waters. The most apparent negative changes involve the degradation of the native seagrass Posidonia oceanica (L.) Delile. Our study examined the effects of fish cage aquaculture on seagrass health, sea urchin density and herbivore feeding pressure in shallow seagrass patches in the coastal waters of 2 Greek islands (Evia and Crete) between February and May of 2008. Evia and Crete represent a wide range of fish farming intensities, from small-scale (75 t yr−1) to large-scale (1000 t yr−1) fish production, respectively. On both islands, the seagrass variables, shoot productivity, standing crop and leaf morphometrics (length and width) were significantly lower (p < 0.0001) in impacted seagrass patches adjacent to fish farms compared with control patches. In addition, significantly higher sea urchin densities and herbivore feeding pressure (percentage of shoots with herbivore grazing scars) were found in impacted patches on both islands. Higher leaf tissue nitrogen and epiphyte loads were also found in impacted patches, but these increases could not be attributed to fish farming alone. Our results show that negative effects on seagrass patches can occur as a result of fish farming at both small-scale and large-scale intensities and that increased sea urchin densities and feeding pressures are important indirect effects of coastal aquaculture on these islands. KEY WORDS: Aquaculture · Seagrass · Posidonia oceanica · Paracentrotus lividus · Nitrogen · Herbivory · Indirect effects Full text in pdf format NextCite this article as: Rountos KJ, Peterson BJ, Karakassis I (2012) Indirect effects of fish cage aquaculture on shallow Posidonia oceanica seagrass patches in coastal Greek waters. Aquacult Environ Interact 2:105-115. https://doi.org/10.3354/aei00037 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 2, No. 2. Online publication date: January 31, 2012 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2012 Inter-Research.
Highlights
Seagrass ecosystems are among the most productive (Duarte & Chiscano 1999) and economically valuable (Costanza et al 1997) on Earth and are found along the coasts of every continent except Antarctica
Our study examined the effects of fish cage aquaculture on seagrass health, sea urchin density and herbivore feeding pressure in shallow seagrass patches in the coastal waters of 2 Greek islands (Evia and Crete) between February and May of 2008
While research to elucidate the full effects of these operations is still in its infancy, previous efforts have focused on elucidating effects on seagrass meadows at depths ≥5 m in the vicinity of fish farm cages
Summary
Seagrass ecosystems are among the most productive (Duarte & Chiscano 1999) and economically valuable (Costanza et al 1997) on Earth and are found along the coasts of every continent except Antarctica. In the Mediterranean Sea, Posidonia oceanica (L.) Delile is the dominant seagrass species and is commonly found at depths shallower than 40 m (Boudouresque & Meinesz 1982) This slow-growing monocot forms dense meadows or patches, which provide a myriad of ecosystem services (Duarte 2002). There is evidence of rapid declines in P. oceanica meadows at the regional scale (Marbà et al 1996, 2005, Delgado et al 1999, Duarte 2002). This loss has been largely a result of the cumulative effects of various anthropogenic influences, including increased aquaculture practices (Marbà et al 2005, Pergent-Martini et al 2006, Gonzalez-Correa et al 2007)
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