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Ecology of Marine SedimentsFrom Science to Management$
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John S. Gray and Michael Elliott

Print publication date: 2009

Print ISBN-13: 9780198569015

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780198569015.001.0001

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Functional Diversity of Benthic Assemblages

Functional Diversity of Benthic Assemblages

(p.70) Chapter 5 Functional Diversity of Benthic Assemblages
Ecology of Marine Sediments

John S. Gray

Michael Elliott

Oxford University Press

Now that we have discussed how assemblages of marine soft sediments are structured, we need to consider functional aspects. There are a few main interrelationships that need to be discussed here— inter- and intraspecific competition, feeding and predator–prey interactions, the production of biomass, and the production and delivery of recruiting stages. Other functional aspects, such as the effects of pathogens and parasites and the benefits of association (mutualism, parasitism, symbiosis, etc.) are of less importance in the present discussion. By function we mean the rate processes (i.e. those involving time) that either affect (extrinsic processes) or are inside (intrinsic processes and responses) the organisms that live in sediments. Hence these include primary and secondary production and processes that are mitigated by the organisms that live in sediments, such as nutrient and contaminant fluxes into and out of the sediment. We begin with the historical development of the field since such aspects are often overlooked in these days of electronic searches for references. Functional studies of ecosystems really began with Lindeman´s classic paper (1942) on trophic dynamics. Rather than regarding food merely as particulate matter, Lindeman expressed it in terms of the energy it contained, thereby enabling comparisons to be made between different systems. For example, 1 g of the bivalve Ensis is not equivalent in food value to 1 g of the planktonic copepod Calanus, so the two animals cannot be compared in terms of weight, but they can be compared in terms of the energy units that each gram dry weight contains. The energy unit originally used was the calorie, but this has now been superseded by the joule (J), 1 calorie being equivalent to 4.2 joules. Ensis contains 14 654 J g-1 dry wt and Calanus 30 982 J g-1 dry wt. The basic trophic system is well understood and can be summarized as we showed earlier in Fig. I.8 which gives the links between various trophic levels and the role of competition, organic matter transport, and resource partitioning. In systems fuelled by photosynthesis (so excluding the chemosynthetic deep-sea vent systems), the primary source of energy for any community is sunlight, which is fixed and stored in plant material, which thus constitutes the first trophic level in the ecosystem.

Keywords:   aerobic metabolism, anaerobic metabolism, bivalves, brackish water, burrowing species, carbon, carbon isotopes, competition, echiurids, ecosystems, eutrophication, food webs, freshwater, functional guilds, gametes, gastropods, grain sizes, growth rates, larvae, molluscs, monitoring, mortality, nematodes, polar regions, production, sea urchins, shallow water, sunlight, temperature, tides, trophic systems, tube builders, waste, waves, weather patterns

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