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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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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 27 October 2021

Spatial Variations in Sediment Systems

Spatial Variations in Sediment Systems

(p.89) Chapter 6 Spatial Variations in Sediment Systems
Ecology of Marine Sediments

John S. Gray

Michael Elliott

Oxford University Press

In this chapter the primary emphasis is on spatial scales of disturbances, and we will follow on from our earlier discussions on the mechanisms of competition and predation and the controversy over their importance in controlling species richness. Huston (1994) realized that the effects of competition, predation, and general physical disturbance were similar in that individuals were removed from the assemblage. We now show that there is a need to link these aspects with the tolerances of individual species, for example to determine in which of these cases the organisms are absent because the conditions now fall outside the optimal tolerance ranges. Thus we discuss disturbance as a general phenomenon which includes the effects of any processes that lead to a reduction in numbers of individuals and/or biomass. Disturbance includes physical disturbance as well as biological processes such as the effects of competition and predation on assemblages. The spatial scales covered range from micrometres to many hundreds of kilometres for the effects of bottom trawling, which is now considered to be one of the most serious and damaging threats to sediment habitats and assemblages. Disturbance effects caused by trawling and by pollution are considered in the following chapters. First, it is necessary to consider scale since many new insights have developed in the past few years of research. In the past couple of decades a new branch of ecology, landscape ecology, has developed, devoted to considering patterns over large areas, and a terminology of spatial scales has been defined. Grain is the first level of spatial resolution; it relates to the individual data unit and can be described as fine-grained to coarse-grained. Extent refers to the overall size of the study area. A map of 100 km2 and one of 100 000 km2 differ in extent by a factor of 1000. Grain and extent are illustrated in Fig. 6.1. A third component is lag, which is the betweensample distance. Figure 6.2 summarizes temporal and spatial scales of disturbances (modified from Zajac et al. 1998). The figure shows the main types of disturbances affecting soft-sediment systems, and separates them into natural and anthropogenic effects (see also Chapter 11, which indicates some of the management responses to these effects).

Keywords:   adaptative strategies, cephalocarids, character displacement, chemicals, crustaceans, cryptomonads, detritus, diatoms, divers, echinoderms, ecosystems, estuaries, growth rates, habitats, holothurians, hydroblid snails, hydrographics, hydrography, icebergs, infauna, intertidal sediments, invertebrates, nereids, niche theory, opportunist species, organisms, oscillation patterns, polar regions, predation, redox potential, reproduction, resources, rocky shores

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