Secondary production of the benthos in an estuarine environment

Abstract

Several projects relating directly or indirectly to energy flow through the benthic community on a mud-flat in the Lynher estuary, Cornwall, U.K. have been integrated by using two methods, firstly a steady-state energy-flow diagram and secondly a dynamic simulation model, in order to provide a better understanding of ecosystem function and as an aid to research planning. For each macrofauna species and meiofauna group an energy budget has been constructed in the form C = P + R + F + U (IBP terminology). This information, together with values for primary inputs of carbon, has enabled us to construct a quantitative diagram representing the flow of carbon between the faunal components of 1 m2 of mud over 1 year. The net annual production of macrofauna is 5.46 g C m-2, and of meiofauna 20•17 g C m-2. Of the meiofauna production, 3•34 g is utilized within the system, so that 16•83 g remains available to mobile carnivores. The macrofauna ingest 55•74 g of primary carbon annually, and the meiofauna 107•09 g. However, the meiofauna standing crop is only 0•49 times that of the macrofauna. Nematodes and copepods are energetically the most important meiofauna groups. Having achieved realistic simulations of secondary production of deposit-feeders, filter-feeders, Nephtys and meiofauna, it has been possible to investigate the effect on the system as a whole of a variety of hypothetical trophic relationships which are poorly understood, particularly the interactions between meiofauna and macrofauna. The growth of Nephtys on different diets is given as an example