Anchoring damage on Posidonia oceanica meadow cover: A case study in Prelo cove (Ligurian Sea, NW Mediterranean)

Among the various types of human activities, the mechanical damages resulting from uncontrolled pleasure boats anchoring in shallow coastal waters would appear to be responsible for localized regressions of Posidonia oceanica meadows. This paper aims to describe and quantify the impacts of a large anchoring chains system on the structure of the P. oceanica meadow of Prelo cove (Ligurian Sea, NW Mediterranean). In this study, we provide evidence that this chains system had a negative effect on the meadow cover, generating dead ‘matte’ areas within the meadow. Meadow structure mapping, combined with the use of an environmental index (Conservation Index), which is linked to the proportional abundance of dead matte relative to living P. oceanica, underpins significant differences in the cover and in the conservation status of the meadow between areas characterized by the presence of the chains and areas without the chains. We also show that the chains affected the meadow in different ways according to P. oceanica cover. The approach proposed here, based on thematic mapping and a simple environmental index, provides relevant information for management actions on the conservation of Posidonia oceanica meadows.

[1]  P. Sanchez‐Jerez,et al.  Recovery of deep Posidonia oceanica meadows degraded by trawling , 2005 .

[2]  A. Mccomb,et al.  Effect of boat moorings on seagrass beds near Perth, Western Australia , 1989 .

[3]  A. Leriche,et al.  A one-century suite of seagrass bed maps: can we trust ancient maps? , 2004 .

[4]  C. Duarte,et al.  How long time does it take to recolonize seagrass beds , 2004 .

[5]  R. Laurent,et al.  Cartographie et état de la limite inferieure de l’herbier de Posidonia oceanica dans les Alpes-maritimes (France) – Campagne Poseïdon 1976 — , 1978 .

[6]  J. Pérês,et al.  Causes de la raréfaction et de la disparition des herbiers de Posidonia oceanica sur les côtes françaises de la Méditerranée , 1975 .

[7]  C. Bianchi,et al.  Effects of climate, invasive species and anthropogenic impacts on the growth of the seagrass Posidonia oceanica (L.) Delile in Liguria (NW Mediterranean Sea). , 2005, Marine pollution bulletin.

[8]  Vanina Pasqualini,et al.  Mapping ofPosidonia oceanicausing Aerial Photographs and Side Scan Sonar: Application off the Island of Corsica (France) , 1998 .

[9]  Núria Marbà,et al.  Growth and population dynamics of Posidonia oceanica on the Spanish Mediterranean coast:elucidating seagrass decline , 1996 .

[10]  Patrice Francour,et al.  Fish assemblages of Posidonia oceanica beds at port-cros (France, NW Mediterranean) : Assessment of composition and long-term fluctuations by visual census , 1997 .

[11]  M. Mateo,et al.  Primary production, stocks and fluxes in the Mediterranean seagrass Posidonia oceanica , 1994 .

[12]  H. Kirkman.  Community structure in seagrasses in southern western Australia , 1985 .

[13]  H. Castro,et al.  Assessment of the conservation status of seagrass (Posidonia oceanica) meadows: implications for monitoring strategy and the decision-making process , 2001 .

[14]  M. Mariani,et al.  A new synthetic index and a protocol for monitoring the status of Posidonia oceanica meadows: a case study at Sanremo (Ligurian Sea, NW Mediterranean) , 2006 .

[15]  R. Koschel,et al.  Primary Production , 2021, Tropical Marine Ecology.

[16]  Vanina Pasqualini,et al.  Contribution of side scan sonar to the management of Mediterranean littoral ecosystems , 2000 .

[17]  V. Pasqualini,et al.  Environmental impact identification along the Corsican coast (Mediterranean sea) using image processing , 1999 .

[18]  G. Kendrick,et al.  Seagrass loss associated with boat moorings at Rottnest Island, Western Australia , 1995 .

[19]  A. Meinesz,et al.  Impact of coastal development on the infralittoral zone along the southeastern Mediterranean shore of continental France , 1991 .

[20]  A. Ganteaume,et al.  Effects of boat anchoring in Posidonia oceanica seagrass beds in the Port‐Cros National Park (north‐western Mediterranean Sea) , 1999 .