Macro-invertebrate populations and production on a salt-marsh in east England dominated by Spartina anglica

The populations and production of the macroinvertebrates of a Spartina anglica salt-marsh in eastern England were studied over two years. A total of fifteen species were recorded in the sediments, of which twelve species were of regular occurrence, and the total population density recorded ranged from 3,481 m^-2 to 11,444m^-2 over the twenty-four sampling occasions.The four most abundant species were Nereis diversicolor, Tubifex costatus, Corophium volutator and Hydrobia ulvae. Thirteen further taxa were associated with the canopy of Spartina, with a total population density ranging from 0 to 1,149 m^-2. Total monthly standing crop ranged from 1.8 to 8.5 g C m^-2 with peaks in July/August in both years. Nereis diversicolor contributed 55% to 86% of total biomass in each month.Production and respiration for each species was determined and annual assimilation calculated. The total annual production was ∼16 g C m^-2 a^-1 in both 1979 and 1980, with a corresponding assimilation of ∼60 g C m^-2 a^-1 Nereis diversicolar accounted for >80% of production and assimilation in both years, and the species is clearly of considerable potential importance in the dissipation of Spartina material. The canopy dwelling species accounted for about 1% of the total annual production and assimilation.