Animal abundance and food availability in coastal lagoons and intertidal marine sediments

Abstract

The relationships between the standing stocks of deposit-feeding benthic invertebrates and benthic chlorophyll-a, phaeopigment and total combustible organic matter were investigated at a series of coastal lagoons and in the type of intertidal soft-sediment sites from which the lagoons originated. Across all the sites, in Norfolk, UK, an inverse relationship occurred between (a) the amounts of chlorophyll-a and of other potential food materials and (b) the degree of coverage by water. The biomass of consumers also decreased with increased water coverage, so that the lagoons supported less biomass than the adjacent high-level intertidal sites. Further, the deposit-feeder biomass supported by unit food decreased with extent of water coverage.There was no evidence of any relationship between deposit-feeder and food biomass within any single site, in spite of the study period being selected to be that in which there was maximum likelihood of competition for microphytobenthic food. Whilst chlorophyll concentrations may set the maximum achievable level of consumer biomass at these sites, including in the deeper lagoons setting very low potential maximum population densities, the seasonal abundance patterns of the deposit feeders appear to be determined by other factor(s).

Interspecific competition and rarity in mudsnails: feeding interactions between and within Hydrobia acuta neglecta and sympatric Hydrobia species

“…It is clearly not the case that egestion rate in Hydrobia species is somehow insensitive to population density, because marked such effects have been shown in Hydrobia knysnaensis (Barnes, in press), H. ventrosa (Levinton, 1979, and above) and H. acuta (above). Why they are not manifest in tests on H. ulvae from Scolt Head Island is difficult to understand, unless it is a reflection of the high food status of their particular habitat (Barnes and de Villiers, 2000) and the consequent reduction in necessary foraging movements. Differences in food content of the test sediments may also explain the differences in the magnitude of intraspecific competition displayed by H. acuta in 2003 and 2004. In East Anglia, lagoonal habitats generally provide H. acuta with a spatial refuge from the superior competitor H. ulvae, but if the latter occurs to landwards of the enclosing barriers it can gain access to lagoons at times of coastal flooding, as has been the case in at least two East Anglian sites (Barnes, 1988b(Barnes, , 1994.…”

Regional and latitudinal variation in the diversity, dominance and abundance of microphagous microgastropods and other benthos in intertidal beds of dwarf eelgrass, Nanozostera spp.

“…Monospecific Nanozostera noltii (= nana) beds fronting saltmarsh within the shelter of the north Norfolk barrier-island chain on the cool-temperate coast of the southwestern North Sea, United Kingdom (see Bridges 1998), where the biology of microgastropods has been studied for a number of years in a system otherwise largely structured by the polychaete Arenicola marina (Serventy et al 1960; Barnes and de Villiers 2000;and see Philippart 1994 (Maree 2000;Bandeira and Gell 2003) and its flats are otherwise dominated by the decapods Callianassa kraussi and Upogebia africana (de Villiers et al 1999;Allanson et al 2000; and see Siebert and Branch 2006). 3.…”

“…NOAA Fisheries 2008) and other large species, but it is now known that macroscopic species are often the tip of the iceberg in intertidal and subtidal aquatic gastropod communities: epifaunal microgastropods (less than, and often much less than, 10 mm in shell height) may be much more abundant and much more diverse than their more obvious larger relatives (Bouchet et al 2002;Strong et al 2008;Hickman 2008;Geiger and Ruthensteiner 2008), and such largely mesograzer species can have an important ecological impact (Klumpp et al 1992;Philippart 1995;Fong et al 2000;Jaschinski and Sommer 2008). In the past, however, judging from their fauna lists, most ecological surveys of seagrass beds have completely ignored this size category, with the notable exception of the northern Atlantic and its associated semi-enclosed seas in which the seagrass beds and soft sediments are clearly dominated by relatively large hydrobiid microgastropods (Muus 1967;Asmus and Asmus 1985;Boström and Bonsdorff 1997; Barnes and de Villiers 2000).…”

Energy homeostasis as an integrative tool for assessing limits of environmental stress tolerance in aquatic invertebrates

“…Importantly for our subsequent discussion, the components of an organism's energy budget are functionally linked together, so that changes in any of the processes have consequences for one or more of the others. This functional linkage is provided by two major constraints that require allocation of available energy (in terms of calories) and metabolic power: 1) the limitation in energy input including the overall amount of available food and the rate of its assimilation (Barnes, 1974;Barnes and de Villiers, 2000;Beukema and Cadeé, 2001); 2) limitation of the maximum metabolic capacity (e.g. in oxygen supply capacities or mitochondrial efficiency) for conversion of the food and channeling it toward different physiological processes (Guderley and Pörtner, 2010).…”