Aquatic Botany, 46 (1993) 49-66 49 0304-3770/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved Seasonal dynamics ofbiomass and nutrient content in the intertidal seagrass Zostera noltii Hornem. from Palmones River estuary, Spain J.L. Prrez-Llorrns *'a, F.X. Niell b aDepartamento de Biologia, Facultad de Ciencias del Mar, Universidad de Cddiz, 11510 Puerto Real. Cddiz, Spain bDepartamento de Ecologia, Facultad de Ciencias, Universidad de Mddaga, Campus de Teatinos, 29071 Mrlaga, Spain (Accepted 12 February 1993 ) Abs~a~ The seasonal dynamics of above- and belowground biomass of Zostera noltii Hornem. were studied in a permanent quadrat in the Palmones River estuary, southern Spain (36 ° 11' N, 5°27 ' W) from February 1988 to February 1990. Temporal changes in nitrogen, carbon, different phosphorus frac- tions (soluble reactive phosphorus, total soluble phosphorus, particulate phosphorus and total phos- phorus) and nutrient ratios (C/N, N/P and C/P), were also investigated in the same population from January 1989 to January 1990. Biomass of above- and belowground structures showed a unimodal seasonal pattern with maxima in summer ( 180-200 g DW (dry weight) ) m -2 and 70-75 g DW m -2 respectively) and minima in winter (30-50 g DW m -2 and 25-30 g DW m -2). Internal concentrations of carbon, nitrogen and phosphorus showed seasonal changes, with minima for nitrogen (3.0% for shoots and 1.2% for under- ground parts) and total phosphorus (0.45% for underground pans) in summer. Shoots and under- ground parts of Z. noltii contained maximum amounts of nitrogen ( 5.9 g m- 2 and 2.1 g m- 2, respec- tively), phosphorus ( 1.7 g m -2 and 0.6 g m -2) and carbon (66.9 g m -2 and 27.8 g m -2 ) in August. The annual flux of nutrients from Z. noltii to the detritus compartment has been estimated to be about 14.6 g N, 4.1 g P and 155.3 g C m -2 of sediment surface. Introduction Seagrass meadows have become recognised as one of the richest and most productive ecosystems, reaching large biomass and being relatively long-lived components of coastal and estuarine ecosystems (Thayer et al., 1977; Zieman and Wetzel, 1980). Their role in the cycling of essential elements (i.e. nitro- gen and phosphorus ) is important owing to their ability to accumulate these elements, affecting the nutrient turnover in these systems. Zostera spp. are able to take up nutrients through their roots and shoots *Corresponding author.