Descriptors of Posidonia oceanica meadows: Use and application

Abstract

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.

Modeling Posidonia oceanica growth data: from linear to generalized linear mixed models

“…These measures are based on the analysis of some persistent morphological features of reiterative modules characterizing seagrass growth (Guidetti, 2001), and allow the determination of seagrass shoots and rhizomes age (Pergent, 1990, Duarte et al, 1994. Currently, about 60% of Mediterranean marine laboratories, focusing their research on seagrass ecosystems, use back-dating measures to monitor P. oceanica meadows, because they provide information about: (a) temporal evolution of above and below ground production; (b) rate of sedimentation; (c) importance of sexual reproduction; (d) dynamics of the meadow, and (e) reaction to environmental factors (Pergent-Martini et al, 2005). Back-dating techniques have been applied to investigate the effect on P. oceanica rhizomes growth of climate change (Marbá and Duarte, 1997), deterioration of marine coastal environment (Guidetti and Fabiano, 2000;Balestri et al, 2004;Tomasello et al, 2007), sedimentation (Boudouresque et al, 1984), water transparency (Guidetti, 2001), water temperature and hydrodynamic regime (La Loggia et al, 2004), and sexual reproduction (Balestri and Vallerini, 2003;Calvo et al, 2006).…”

“…It exerts a multifunctional role within coastal systems offering substrate for settlement and food source, as well as maintaining the chemical and physical characteristics of water and sediments (Procaccini et al, 2003). Moreover, being sensitive to changes in the environment, P. oceanica is considered a crucial indicator of the quality of coastal marine waters (Pergent-Martini et al, 2005).…”

Setting an ecological baseline prior to the bottom-up establishment of a marine protected area in Santorini island, Aegean Sea

“…Each of these metrics provides useful information on the vitality of the P. oceanica meadows for a wide spectrum of anthropogenic disturbances (i.e. nutrient enrichment, sediment resuspension and turbidity, mechanical disturbance) (Pergent-Martini et al, 2005). With the exception of the meadow lower limit typology, all other metrics were sampled at a standard depth of 15 m to prevent the masking effects of depth variability (Alcoverro et al, 1995).…”

Indirect effects of fish cage aquaculture on shallow Posidonia oceanica seagrass patches in coastal Greek waters

“…This research (1) examined seagrass shoot morphometrics and productivity between control seagrass patches and those affected by fish farming (impacted) on 2 Greek islands, (2) quantified sea urchin density and herbivore feeding pressure, (3) quantified epiphyte load across all patches and (4) evaluated nitrogen and carbon concentrations in seagrass and epiphyte tissues. These parameters were selected as they are commonly used (Pergent-Martini et al 2005) and provide reliable means to evaluate the effects of aquaculture on the Mediterranean Sea.…”