Production of seaweeds in Northwestern Mediterranean marine communities: Its relation with environmental factors

Abstract

A synthesis of production data in 12 algal-dominated littoral communities from Tossa de Mar (Spain) is presented. Estimates of production values come from several studies of the biomass cycle of dominant species and/or different methods for identifying the growth of marked individuals. Sampled communities are representative of the different bionomic zones described in the Mediterranean. Because of their different locations (calm waters vs. turbulent waters) and bathymetric distribution, these communities are subject in different degree to the main factors controlling primary production in benthic communities (water availability, light, nutrients and hydrodynamism). Production estimates range between 77 g afdwt m-2 year-1 (Halimeda tuna community, circalittoral zone) and 2175 g afdwt m-2 y-1 (Cystoseira mediterranea community, infralittoral zone), which corresponds to a daily primary production between 0.1 and 2.4 g C m-2 day-1. Immersion seems to be the limiting factor in the upper part of the mediolittoral zone. Nutrient availability (nutrient concentration X hydrodynamism) is probably the limiting factor for production in the infralittoral zone, while light seems to limit the growth in the circalittoral zone. A temporal lag has been observed in the production maxima in the different communities placed along a bathymetric transect. Mediolittoral communities have their periods of maximum growth in winter while circalittoral communities have their production maxima in summer. This can be interpreted as an adaptation of the different species and communities to the seasonal cycle of the factor or factors mainly limiting their growth.