Production and growth dynamics of eelgrass (Zostera marina) in brackish lake grevelingen (The Netherlands)

Abstract

Biomass changes of overground eelgrass ( Zostera marinaL.) parts in a permanent sample plot in brackish Lake Grevelingen showed a unimodal seasonal pattern over the years 1974–1976, with maxima of 75 to 94 g ash-free dry weight ś dm −2 in July–August and minima between 0 and 5 g ash-free dry weight·m −2 in December–April. Biomass changes of living underground parts showed a faint peak in the period July–October (35 to 50 g ash-free dry weight · m −2) and a minimum in the period December–April (about 10 g ash-free dry weight·m −2. Concerning the vertical biomass distribution, eelgrass reached maxima in July–August of about 130 g ash-free dry weight·m −2 (over- and underground parts) at 1 to 1.5 m water depth, and approached zero at 4 m water depth. Biomass increase of overground and underground parts was estimated at 39.4 g C.m · −2 and 12.2 g. C.m ·m −2 respectively in 1976. With a leaf-marking technique net leaf production and rhizome production were estimated at 207.5 g C.·m −2·a −1 and 27.4 g C·m -2. a −1 respectively in 1976. Production of stems and inflorescences was estimated at 45.2 g C·m −2 ·a −1. The P/B ratio of overground parts was estimated at 6.4, of underground parts at 2.2, and of both together at 5.4. The data from Lake Grevelingen show good agreement with Danish results. Considering the standing stock of eelgrass in Lake Grevelingen in 1973, and 1975, an annual production of 200 to 300 g C·m −2 within the Zostera beds seems a realistic estimate.