Carbon budget for a coastal inlet in relation to intensive cultivation of suspension-feeding bivalve mollusks

Abstract

W a r y Harbour, a fjordic inlet on the west coast of Ireland, is the site of intensive suspended cultivation of mussels. Data on biornass and production of the macrobenthic infauna and zooplankton in the system are combined with literature data on primary production and wild and cultured mussel production in Kdlary Harbour to produce a balanced carbon budget. Total particulate carbon input to the system is 1907 tonnes C yr-'. Carbon production by phytoplankton is partitioned between zooplankton, cultured mussels, wild mussels, phytoplankton respiration and the detritus pool. The detritus pool also receives inputs from river carbon, macroalgae, zooplankton faeces, mussel faeces and phytoplankton. There is a carbon deficit which is probably accounted for by DOC input in freshwater, or import of marine POC, which were not measured. The data are used to estimate the maximum potential yield of cultured mussels from the system. This is in the order of 2000 to 3000 tonnes live weight per year. At this level of production, changes in the ecosystem are predicted. These are expected to arise from competition between mussels and zooplankton for food resources, increased sebmentation in localized areas, and disruption of the nitrogen cycle. However, nitrogen should not limit mussel production. Mussel culture, unlike fish culture in sea cages, re-routes the flow of energy and materials in coastal marine ecosystems but does not cause eutrophication by nutnent input. This is discussed in relation to red tides.

Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study

“…If bottom currents are below the critical erosional velocity, the biodeposits undergo a dewatering process and gradually become incorporated into the sediments (Haven andMorales-Alamo 1966, 1968;Dame 1987;Jaramillo et al 1992) leading to an increase in sediment N content (Kaspar et al 1985;Kautsky and Evans 1987;Deslous-Paoli et al 1992;Hatcher et al 1994). High abundances of bivalves can overenrich sediments with biodeposits, thereby generating high microbial respiration leading to sediment anoxia that both inhibits nitrification and kills bioturbating benthic infauna (Tenore et al 1982;Rodhouse and Roden 1987). Such local adverse effects can be ameliorated by moderate water currents or wave action that allows biodeposits to be spread across a larger bottom area (Haven and Morales-Alamo 1968;Dame 1987;Dame et al 1991).…”

Effects of body size on suspension feeding and energy budgets of the pearl oysters Pinctada margaritifera and P. maxima

“…Further studies are needed to model the carrying capacities of pearl farming sites, as has been undertaken for mussel farming (e.g. Rodhouse & Roden 1987, Grant 1996.…”

Feeding adaptations of the pearl oysters Pinctada margaritifera and P. maxima to variations in natural particulates

“…Before launching pearl farming i n a n a r e a , it would b e wise to conduct trophic modelling a n d environmental impact assessm e n t a t t h e appropriate stocking densities of cultured pearl oysters, a s has b e e n u n d e r t a k e n for mussel farming (e.g. Rodhouse & Roden 1987, G r a n t 1996).…”