Descriptors of Posidonia oceanica meadows: Use and application

The conservation of the coastal marine environment requires the possession of information that enables the global quality of the environment to be evaluated reliably and relatively quickly. The use of biological indicators is often an appropriate method. Seagrasses in general, and Posidonia oceanica meadows in particular, are considered to be appropriate for biomonitoring because of their wide distribution, reasonable size, sedentary habit, easy collection and abundance and sensitivity to modifications of littoral zone. Reasoned management, on the scale of the whole Mediterranean basin, requires standardized methods of study, to be applied by both researchers and administrators, enabling comparable results to be obtained. This paper synthesises the existing methods applied to monitor P. oceanica meadows, identifies the most suitable techniques and suggests future research directions. From the results of a questionnaire, distributed to all the identified laboratories working on this topic, a list of the most commonly used descriptors was drawn up, together with the related research techniques (e.g. standardization, interest and limits, valuation of the results). It seems that the techniques used to study meadows are rather similar, but rarely identical, even though the various teams often refer to previously published works. This paper shows the interest of a practical guide that describes, in a standardized way, the most useful techniques enabling P. oceanica meadows to be used as an environmental descriptor. Indeed, it constitutes the first stage in the process. (c) 2005 Elsevier Ltd. All rights reserved.Peer reviewe

Teledetection et variations du phytobenthos intertidal

Densitometric analyses and airborne infrared photographs obtained from year to year, together with field observations, were employed to quantify the extent of fluctuations in the previously identified algal populations on various sites. Besides, spectroradiometric records of similar algal populations were also obtained. This study confirms the possibility to collect automatic and repetitive data with SPOT, satellite that will permit a control and management of intertidal seaweeds at a very large scale

"PIX'ILES 90" : télédétection et milieux insulaires du Pacifique : approches intégrées = Remote sensing and insular environments in the Pacific : integrated approaches

Le rôle joué par les algues benthiques dans l'écosystème corallien est multiple : protection des récifs, maillon de chaînes alimentaires, structure d'accueil de la faune, production de substances diverses. A ce titre, toute fluctuation mesurée à partir d'un état de référence peut être bio-indicatrice. Le satellite SPOT permet, grâce à ses capteurs à haute résolution et à son enregistreur, de fournir la cartographie globale des végétaux marins ainsi que celle des principaux composants de l'écosystème lagonaire de l'île de Moorea (Polynésie française). Cette première approche écologique par satellite se devrait d'être confortée, du fait du développement de pollutions d'origines diverses, par un suivi multitemporel. (Résumé d'auteur

Experimental assessment of oyster transfers as a vector for macroalgal introductions

Introduction of non-indigenous species can alter marine communities and ecosystems. In shellfish farming, transfer of livestock, especially oysters, is a common practice and potentially constitutes a pathway for non-indigenous introductions. Many species of seaweeds are believed to have been accidentally introduced in association with these transfers, but there is little direct evidence. We experimentally simulated the transfer of oysters from the Thau Lagoon (France). These transfers involved increasing periods of aerial emersion and additional brine and hot water treatments. The brine and hot water treatments were evaluated as a means of reducing the probability of algal introductions with oyster transfers. Shells were cultured for 40 days in experimental tanks to identify the macroalgae likely to be introduced with any oyster transfer. A total of 57 macroalgal taxa, including 16 taxa not indigenous to the Thau Lagoon, were recorded across all treatments and experiments. The abundance of some species increased in several cases following aerial emersion. Elimination treatments (immersion in brine or hot water) significantly reduced algal diversity, with hot water treatments resulting in no species or only tubular Ulva spp. present. The results support the hypothesis that oyster transfers are effective as primary and secondary vectors of macroalgal introductions. Relatively simple changes to the transfer practice (particularly hot water treatments) are suggested as a means of reducing the risk of non-indigenous algal introductions

The Seascape as an Indicator of Environmental Interest and Quality of the Mediterranean Benthos: The in Situ Development of a Description Index: The LIMA

peer reviewedThe LIMA index conveys the environmental interest and quality of the landscape formed by the Mediterranean benthos, ranging from 0 to − 40 m, in numerical format. The LIMA index allows a comparison spatially and temporarily between sites. It is a comprehensive index which is easy to implement and is composed of two factors: a topographical description (classification of 15 typologies) and a biological description (the presence or absence of some thirty species or groups of structuring, remarkable and invasive species). The LIMA index has been validated in he Bay of Calvi (Corsica-France) where it varies between 0.31 and 0.79 on a scale of 0.00–1.00

Modelling of Oxygen and Nitrogen Cycling as a Function of Macrophyte Community in the Thau Lagoon.

Abstract not availableJRC.H-Institute for environment and sustainability (Ispra