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Feast or famine for intertidal grazing molluscs: a mis-match between seasonal variations in grazing intensity and the abundance of microbial resources

Feast or famine for intertidal grazing molluscs: a mis-match between seasonal variations in grazing intensity and the abundance of microbial resources
Feast or famine for intertidal grazing molluscs: a mis-match between seasonal variations in grazing intensity and the abundance of microbial resources
Distinct seasonal variations in the abundance of photosynthetic microbiota and limpet grazing intensity were recorded at Port St Mary, Isle of Man between January 1994 and June 1996. Microbial abundance was negatively correlated with insolation stress, while grazing intensity was positively correlated with sea and air temperature. These patterns result in a mis-match between the supply of and the demand for microbial resources with maximal grazing intensity during the summer and autumn, but maximal microbial standing stock during the winter and early spring. The importance of top-down control of microbial assemblages by grazing was demonstrated by experimental exclusion of limpets during autumn 1993. This resulted in a four-fold increase in the abundance of cyanobacteria within 6 days, followed by a more gradual proliferation of ephemeral algae during the next 4 weeks. The abundance of diatoms remained relatively constant and was not influenced by the removal of grazers at this time of year. The influence of microbial resource availability on the growth and mortality of limpets was examined using experimental enclosures of differing densities of either Patella vulgata or P. depressa. After 6 months, there were significant relationships between grazer density and both mortality and growth with increased mortality and reduced growth for P. vulgata at increased densities, and reduced growth for P. depressa at increased densities. Hence, the availability of microbial resources may also influence the biomass of grazers on rocky shores from the bottom upwards. A conceptual model is presented which describes seasonal and annual variations in microbial resources and grazing intensity and their potential consequences for other shore dwellers.
top-down, bottom-up, biofilm, microphytobenthos, density dependence. intra-specific competition
0018-8158
357-367
Thompson, R.C.
d632e905-6f51-49a0-9426-13c42c3d0a18
Roberts, M.F.
75f102c2-5f20-4426-9bef-a6ebf2ec1fc0
Norton, T.A.
464d9a03-46f4-48ef-9cba-f3662000cbfb
Hawkins, S.J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa
Thompson, R.C.
d632e905-6f51-49a0-9426-13c42c3d0a18
Roberts, M.F.
75f102c2-5f20-4426-9bef-a6ebf2ec1fc0
Norton, T.A.
464d9a03-46f4-48ef-9cba-f3662000cbfb
Hawkins, S.J.
758fe1c1-30cd-4ed1-bb65-2471dc7c11fa

Thompson, R.C., Roberts, M.F., Norton, T.A. and Hawkins, S.J. (2000) Feast or famine for intertidal grazing molluscs: a mis-match between seasonal variations in grazing intensity and the abundance of microbial resources. Hydrobiologia, 440 (1-3), 357-367. (doi:10.1023/A:1004116505004).

Record type: Article

Abstract

Distinct seasonal variations in the abundance of photosynthetic microbiota and limpet grazing intensity were recorded at Port St Mary, Isle of Man between January 1994 and June 1996. Microbial abundance was negatively correlated with insolation stress, while grazing intensity was positively correlated with sea and air temperature. These patterns result in a mis-match between the supply of and the demand for microbial resources with maximal grazing intensity during the summer and autumn, but maximal microbial standing stock during the winter and early spring. The importance of top-down control of microbial assemblages by grazing was demonstrated by experimental exclusion of limpets during autumn 1993. This resulted in a four-fold increase in the abundance of cyanobacteria within 6 days, followed by a more gradual proliferation of ephemeral algae during the next 4 weeks. The abundance of diatoms remained relatively constant and was not influenced by the removal of grazers at this time of year. The influence of microbial resource availability on the growth and mortality of limpets was examined using experimental enclosures of differing densities of either Patella vulgata or P. depressa. After 6 months, there were significant relationships between grazer density and both mortality and growth with increased mortality and reduced growth for P. vulgata at increased densities, and reduced growth for P. depressa at increased densities. Hence, the availability of microbial resources may also influence the biomass of grazers on rocky shores from the bottom upwards. A conceptual model is presented which describes seasonal and annual variations in microbial resources and grazing intensity and their potential consequences for other shore dwellers.

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More information

Published date: 2000
Keywords: top-down, bottom-up, biofilm, microphytobenthos, density dependence. intra-specific competition

Identifiers

Local EPrints ID: 188539
URI: https://eprints.soton.ac.uk/id/eprint/188539
ISSN: 0018-8158
PURE UUID: 20dbd072-023f-4f96-8364-f812f3c47de0

Catalogue record

Date deposited: 25 May 2011 12:35
Last modified: 16 Jul 2019 23:32

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