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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.

The impact of fish farming facilities on Posidonia oceanica meadows was assessed from studies of intensive facilities carried out over the last few years. The disturbances caused by these fish farms were measured by means of both abiotic (light, sediment, interstitial water) and biotic variables (meadow density, leaf biometry, lepidochronology, primary production, epiphytes, reserve carbohydrates in the rhizomes), in function of increasing distance from cages and/or inside a geographically close reference site. The results showed significant degradation of these seagrass meadows in all the sectors investigated. When fish farming cages were placed above a P. oceanica bed, the meadow was severely degraded or disappeared and the sediment showed a strong increase in organic matter that could lead to anoxia phenomena. The irreversible impact of fish farming projects on P. oceanica meadows requires the application of the precautionary principle. Several recommendations (site selection, preliminary studies and monitoring over time) are suggested in order to enable piscicultural activities to be incorporated in a global process of Integrated Coastal Zone Management.

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ABSTRACT1. Excessive nutrient discharge, linked to human activities, is one of the main causes of the decline of seagrass meadows since it modifies two essential parameters controlling their primary production: the nutrient concentrations (especially nitrogen and phosphorus) and the irradiance.2. To investigate the behaviour of seagrass under varied conditions of light and/or nutrient concentrations, it is necessary to experimentally manipulate nutrient enrichment and light, either in situ or in artificial ecosystems. The available experimental information concerning the influences of light reduction and nutrient enrichments (N and P) on seagrass meadows are summarized.3. The protocols for experimentally reducing light vary considerably but all light reduction experiments show a decrease in seagrass vitality and physiological changes (e.g. promotes an increase in chlorophyll and tissue nitrogen), depending on the species-specific tolerance (light optima).4. A wide range of protocols for experimentally increasing nutrient levels have been applied, including varying the nutrient species quantities and ratios, as well as the sources and frequency of additions. Responses to N and/or P enrichment range from stimulation to direct or indirect inhibition, varying depending upon the species, the protocol implemented, the nutrient source (water column versus sediments), and other environmental conditions (e.g. interactions with factors such as temperature, grazing and light).5. Both light reduction and nutrient enrichment, can cause seagrass decline, through similar internal mechanisms, promoting an imbalance of internal nutrient supply ratios. Similar physiological responses can thus be observed (e.g. increase of N, P and chlorophyll contents of leaves).6. This study shows the close link between the physiology and morphology of seagrasses, with regard to environmental modifications. It also highlights their ability to provide information on environmental conditions by means of their responses.

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Foliar phenol concentrations (total and simple phenols) were determined in Aleppo pine (Pinus halepensis Mill.) needles collected in June 2000, from 6 sites affected by various forms of atmospheric pollutants (NO, NO 2 , NO x , O 3 and SO 2 ) monitored during two months. Results show an increase in total phenol content with exposure to sulphur dioxide and a reduction with exposure to nitrogen oxide pollution. p-Coumaric acid, syringic acid and 4-hydroxybenzoic acid concentrations increase with exposure to nitrogen oxide pollution, whereas gallic acid and vanillin decrease in the presence respectively of sulphur dioxide and ozone. This in situ work confirms the major interest of using total and simple phenolic compounds of P. halepensis as biological indicators of air quality.

The aim of the present study is to assess whether certain ecophysiological responses (contents of total phenols, total proanthocyanidins, and total and simple flavonols), in the needles of Aleppo pines (Pinus halepensis Mill.) may be valid bioindicators for the assessment of the air quality. Samples were taken at five natural sites polluted by various pollutants (NO, NO2, other NOx, SO2, and O3). The results show a decrease in total phenol concentrations with levels of nitrogen oxide pollutions (significant negative correlations between the total phenol concentrations and concentrations of NO, NO2, and other NOx). Total flavonoids (total flavonols and proanthocyanidins) are useful bioindicators for ozone pollution (significant negative correlations between total proanthocyanidins and the concentrations of ozone and significant positive correlations between total flavonols and the ozone pollution). Sulfur dioxide pollution is distinguished by low concentrations in quercetin, isorhamnetin, and kaempferol (significant negative correlations between these simple flavonols and the concentrations of SO2). This work confirms the strong interest of using the phenolic compounds of Pinus halepensis as biological indicators of air quality.