Illegal trawling and induced invasive algal spread as collaborative factors in a Posidonia oceanica meadow degradation

Posidonia oceanica, a key seagrass species of the Mediterranean Sea, shows clear signs of regression throughout the Mediterranean and illegal trawling is recognized as one of the main causes. We examined the condition of a P. oceanica meadow in Alykes Bay (Zakynthos Island, western Greece), a typica...

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Bibliographic Details
Published in:Biological invasions 2011-03, Vol.13 (3), p.669-678
Main Authors: Kiparissis, Sotiris, Fakiris, Elias, Papatheodorou, George, Geraga, Maria, Kornaros, Michael, Kapareliotis, Apostolos, Ferentinos, George
Format: Article
Language:English
Subjects:
Algae
Biological sampling
Biomedical and Life Sciences
Caulerpa racemosa
Commercial fishing
degradation
Developmental Biology
Ecology
fisheries
Freshwater & Marine Ecology
image analysis
invasive species
islands
Life Sciences
Marine
Meadows
Nonnative species
Ocean floor
Original Paper
Plant populations
Plant Sciences
Population density
Posidonia oceanica
Posidoniaceae
Recolonization
Sabella pavonina
sediments
surveys
Trawling
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Summary:Posidonia oceanica, a key seagrass species of the Mediterranean Sea, shows clear signs of regression throughout the Mediterranean and illegal trawling is recognized as one of the main causes. We examined the condition of a P. oceanica meadow in Alykes Bay (Zakynthos Island, western Greece), a typical Mediterranean littoral area where illegal trawling is common practice, in respect to the total area affected, and in terms of possible ecological substitution. A side scan sonar (SSS) survey of the seafloor provided an image of the condition of the meadow and biological sampling evaluated the ecological status in affected meadow areas. SSS images revealed that trawling has a serious effect on the meadow, with 11% of the vegetated area being abraded, and the affected areas were also found to be fully colonized by the invasive alga Caulerpa racemosa. Moreover, unusually high densities of the polychaete Sabella pavonina were detected in the affected areas among C. racemosa fronds. Recolonization by P. oceanica of the affected meadow areas that have been colonized by C. racemosa seems improbable considering the allelopathic interactions between the species, with the alga displaying phytotoxic properties through caulerpenyne production and deterioration of the sediment quality.
ISSN:1387-3547
1573-1464
DOI:10.1007/s10530-010-9858-9