Spatial and temporal variability of "Cymodocea Nodosa" meadows on Gran Canaria island

Abstract

Seagrasses worldwide constitute a key habitat on shallow soft bottoms, but they are experiencing a rapid decline. In order to describe the anatomical, morphological and demographic variations of Cymodocea nodosa over time, samples were taken during two years at three meadows on the island of Gran Canaria; one meadow is affected by the action of humans (Arinaga) and two outside the influences of relevant human actions (Gando and Castillo del Romeral). The anatomical changes were evaluated through the above ground biomass and below ground biomass, the morphometric study through the measurement of the leaf length, leaf width and number of leaves per shoot and, finally, the number of shoots were counted as a demographic descriptor. The three morphometric descriptors (leaf length, leaf width and number of leaves per shoot), the density of shoots and above ground biomass showed a seasonal pattern at the three meadows, with maximum in summer and minimum in winter. In contrast, below ground biomass showed a seasonality with maximums in winter and minimums in summer. The study showed that decreased genotype and genetic diversity of the seagrass meadow at Arinaga was directly related with a greater interannual variability of the demographic-anatomical descriptors of seagrass, relative to the other two meadows. On the other hand, this relationship was insignificant for the morphometric descriptors, which are more influenced by other ecological processes at the local scale.