Production dynamics in a macrophyte-dominated ecosystem: the Mar Menor coastal lagoon (SE Spain)

Abstract

The greater part of the bottom of the Mar Menor, a hypersaline coastal lagoon in the south-east of the Iberian Peninsula, is covered by meadows of Caulerpa prolifera and Cymodocea nodosa. Both species show marked seasonality in their biomass cycles, reaching their highest annual values in summer-autumn and their lowest in winter-spring. The annual production of the C. prolifera mud-based meadows is estimated at 630-707 g dw m-2 y-1. Leaf production of the C. nodosa varies between 162 and 427 g dw m-2 y-1, while rhizome production varies between 45 and 78 g dw m-2 y-1. C. prolifera growth seems to be limited by the availability of nitrogen in the water column, while C. nodosa growth is limited by the availability of nitrogen and phosphorus. Both species show adaptation in their photosynthetic characteristics (Ic, Ik, Pmax) to seasonal variation in the water temperature of the lagoon. The values of these parameters for C. prolifera suggest that this species is adapted to life in habitats of less irradiance than C. nodosa. The distribution of C. nodosa meadows in the lagoon is controlled by the availability of light at the bottom. Overall primary production of the Mar Menor can be estimated at roughly 41270 Tm C y-1 (some 300 g C m-2 y-1); 64% of the lagoon's primary production is produced by the macrophytebenthos, 11% by the microphytebenthos and 25% by the phytoplankton.