CORRELATION BETWEEN NEMATODE ABUNDANCE AND DECOMPOSITION RATE OF SPARTINA-ANGLICA LEAVES

Dead Spartina anglica leaves which are not washed away by the tides either decompose in the canopy as standing dead crop or decompose on the sediment surface. In the sediment, many nematode species are present which may colonize the Spartina litter. Some of these species may affect the decomposition of Spartina detritus. A field experiment was carried out to identify these nematode species. Small mesh containers were filled with green or aged Spartina leaves to obtain different decomposition rates. The containers were placed in the Stroodorpepolder salt marsh (The Netherlands), in the Oosterschelde, a tidal inlet of the southern North Sea. After 3 mo the containers were collected and nematodes were counted and identified. The experiment was repeated in 4 subsequent seasons. Sixty nematode species were found in the containers; most species were found in all treatments. Total numbers of nematodes did not differ among treatments. Using multivariate analysis (RDA), however, we found differences of nematode community structure among treatments. Bacterivorous nematodes, particularly monhysterid species, prevailed in the containers with the highest decomposition rates. A positive correlation was found between decomposition rate and the numbers of Diplolaimella dievengatensis in spring, summer and autumn. The numbers of Diplolaimelloides bruciei, Monhystera parva, Desmolaimus zeelandicus and Theristus acer showed positive correlations with decomposition rates in 1 or 2 of these seasons. In winter no significant correlations were found. Thus, of the 60 nematode species present in the litter the abundances of only 5 species seemed to be affected by decomposition rate of the litter. It is suggested that these nematode species react primarily to the increased microbial activity coinciding with higher decomposition rates. In addition, these species may further enhance microbial decomposition activity.