Effects of mussel (Perna canaliculus) biodeposit decomposition on benthic respiration and nutrient fluxes
Suspension-feeding bivalves increase the quantity and quality of sedimenting organic matter through the production of faeces and pseudofaeces that are remineralised in coastal sediments and thus increase sediment oxygen demand and nutrient regeneration. Bivalves are intensively cultivated worldwide; however, no bivalve biodeposit decay rates are available to parameterise models describing the environmental effects of bivalve culture. We examined sediment biogeochemical changes as bivalve biodeposits age by incubating coastal sediments to which we added fresh mussel (Perna canaliculus) biodeposits and measured O2 and nutrient fluxes as well as sediment characteristics over an 11-day period. Biodeposits elevated organic matter, chlorophyll a, phaeophytin a, organic carbon and nitrogen concentrations in the surface sediments. Sediment oxygen consumption (SOC) increased significantly (P=0.016) by ∼1.5 times to 1,010 μmol m−2 h−1 immediately after biodeposit addition and remained elevated compared to control cores without additions for the incubation period. This increase is in the range of observed in situ oxygen demand enhancements under mussel farms. To calculate a decay rate for biodeposits in sediments we fitted a first-order G model to the observed increase in SOC. The significant model fit (P=0.001, r2=0.72) generated a decay rate of 0.16 day−1 (P=0.033, SE=0.05) that corresponds to a half-life time of 4.3 day. This decay rate is 1–2 orders of magnitude higher than published decay rates of coastal sediments without organic enrichment but similar to rates of decaying zooplankton faecal pellets. NH 4 + release increased rapidly on the day of biodeposit addition (P=0.013) and reached a maximum of 144 μmol m−2 h−1 after 5 days which was 3.6 times higher compared to control cores. During this period NH 4 + release was significantly (P<0.001 to P=0.043) higher in the cores with biodeposit additions than in control cores.
KeywordsDecay Rate Faecal Pellet Nutrient Flux Coastal Sediment Sediment Oxygen Demand
We thank D. Bell for help in the field and D. and M. Aislabe for access to their mussel farm. We also thank K. Vopel for suggestions on an earlier version of this manuscript. A University of Waikato postgraduate scholarship funded the first author; this is gratefully acknowledged.
- Arar EJ, Collins GB (1997) In vitro determination of chlorophyll a and pheophytin a in marine and freshwater algae by fluorescence. National Exposure Research Laboratory, Office of Research and Development, U.S. Environmental Protection AgencyGoogle Scholar
- Hargrave BT (1976) The central role of invertebrate faeces in sediment decomposition. In: Anderson JM, Macfayden A (eds) The role of terrestrial and aquatic organisms in decomposition processes. Blackwell, Great Britain, pp 301–321Google Scholar
- Hawkins AJS, James MR, Hickman RW, Hatton S, Weatherhead M (1999) Modelling of suspension-feeding and growth in the green-lipped mussel Perna canaliculus exposed to natural and experimental variations of seston availability in the Marlborough Sounds, New Zealand. Mar Ecol Prog Ser 191:217–232CrossRefGoogle Scholar
- Jeffs AG, Holland RC, Hooker SH, Hayden BJ (1999) Overview and bibliography of research on the Greenshell mussel, Perna canaliculus, from New Zealand waters. J Shellfish Res 18:347–360Google Scholar
- Newell RIE (2004) Ecosystem influences of natural and cultivated populations of suspension-feeding bivalve molluscs: a review. J Shellfish Res 23:51–61Google Scholar
- Redfield AC (1934) On the proportions of organic derivatives in sea water and their relation to the composition of plankton. In: Daniel RJ (ed) James Johnstone Memorial Volume. University Press, Liverpool, pp 176–192Google Scholar
- Singer JK, Anderson JB, Ledbetter MT, McCave IN, Jones KPN, Wright R (1988) An assessment of analytical techniques for the size analysis of fine-grained sediments. J Sediment Petrol 58:534–543Google Scholar
- Tenore KR, Boyer LF, Cal RM, Corral J, Garcia-Fernandez C, Gonzalez N, Gonzalez-Gurriaran E, Hanson RB, Iglesias J, Krom M, Lopez-Jamar E, McClain J, Pamatmat MM, Perez A, Rhoads DC, de Santiago G, Tietjen J, Westrich J, Windom HL (1982) Coastal upwelling in the Rias Bajas, NW Spain: contrasting the benthic regimes of the Rias de Arosa and de Muros. J Mar Res 40:701–772Google Scholar