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Categorization of seagrass meadows of Posidonia oceanica along the Catalan coast (NW Mediterranean)

Jordi Sanchez1* and Manel Gazo1
  • 1 SUBMON, Spain

Posidonia oceanica (L.) Delile is the most abundant marine phanerogam in the Mediterranean Sea (Lipkin et al. 2003; Procaccini et al. 2003; Scardi et al. 2006). It is distributed from shallow waters to 40 meters deep, forming vast meadows that cover more than 40,000 km2 in the Mediterranean (Mayot et al. 2006; Scardi et al. 2006). Its surface has decreased by 5-20% over the last century due to coastal development, pollution and trawling (Boudouresque et al. 2009). One of the most commonly used descriptors for the characterization and monitoring of Posidonia oceanica is shoot density/m2 (Mayot et al. 2006; Pergent-Martini et al. 2005). Shoot density is related to depth (Mayot et al. 2006), this meant that, historically, the categorization of P. oceanica meadows was based on the observed density at a given depth (Pergent at al. 1995; Pergent -Martini and Pergent; 1996). The relation of shoot density and depth can be adjusted to a type of negative exponential curve (d = doe-kp) where d is density, p is depth and do p and k are two constants that can be calculated (Romero, 1985). Shoot density/m2 of 36 P. oceanica meadows was studied along the Catalan coast between 2008 and 2015. Negative exponential curve was estimated relating the maximum shoot density values/m2 observed at each depth and values of do = 710,552 and k = 0.066 (R = 0.72, P-value <0.01) were obtained. The resulting density was called optimal density (dopt). To categorize P.oceanica meadows it was defined an index (IO) relating the observed density (dob) with the optimum density (dopt): {IO = [(dob - dopt) / dopt] * 100} that was calculated for each meadow’s depth. Results showed that only 14% of the P.oceanica meadows studied presented values above optimum density. At 14% of the meadows a deviation ranging from 1 to 25% was observed. At 53% of the meadows a deviation from 25 to 50% was observed and at the remaining 19% of the meadows the deviation observed was above 50%. The periodic calculation of the exponential curve and the index (IO) can be a good tool to evaluate the evolution of shoot density/m2 of P.oceanica meadows at a given area.

References

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Keywords: Categorization, Posidonia oceanica, density, Mediterranean Sea, Spain

Conference: XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.

Presentation Type: Poster Presentation

Topic: 1. ECOLOGY, BIODIVERSITY AND VULNERABLE ECOSYSTEMS

Citation: Sanchez J and Gazo M (2016). Categorization of seagrass meadows of Posidonia oceanica along the Catalan coast (NW Mediterranean). Front. Mar. Sci. Conference Abstract: XIX Iberian Symposium on Marine Biology Studies. doi: 10.3389/conf.FMARS.2016.05.00135

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Received: 29 Apr 2016; Published Online: 03 Sep 2016.

* Correspondence: Mr. Jordi Sanchez, SUBMON, Barcelona, Barcelona, 08024, Spain, jordisanchez@submon.org