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Latitudinal and depth gradients in marine predation pressure

Harper, Elizabeth M.; Peck, Lloyd S.. 2016 Latitudinal and depth gradients in marine predation pressure. Global Ecology and Biogeography, 25 (6). 670-678. 10.1111/geb.12444

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Abstract/Summary

Aim There is a general paradigm that marine predation pressure increases towards the tropics and decreases with depth. However, data demonstrating global trends are generally lacking. Rhynchonelliform brachiopods inhabit all the oceans and often survive shell-crushing predator attacks. We investigate shell repair in brachiopods across a range of Southern Hemisphere and tropical Northern Hemisphere latitudes and depths. Location The Southern Hemisphere and tropical Northern Hemisphere. Methods We analysed the frequency of shell repair in 112 bulk samples, over 70% of which showed traces of shell damage and repair. Results The pattern of shell repair frequency (RF) was more complicated than the anticipated increase with decreasing latitude, with low levels at both polar and tropical sites but high levels at temperate latitudes. This pattern is only evident, however, in shallow water assemblages; and there is no latitudinal trend in water depths greater than 200 m, where shell RF is systematically low. There was a significant logarithmic relationship between RF and depth. Low polar repair rates reflect reduced predation pressure, directly supporting the global paradigm. Low rates in the tropics appears counter to the paradigm. However, tropical brachiopods are generally very small (micromorphic) in shallow water and below the minimum size at which damage is recorded anywhere. Main conclusions Predation pressure decreased logarithmically with depth. At shallow depths (< 200 m) RF showed its highest levels in the mid temperate latitudes with decreasing frequency towards both the tropics and the poles. Low levels of shell repair at high latitudes are likely to be due to a lack of crushing predators, but in the tropics it is suggested that the low frequency is a result of the small size of tropical brachiopods. We hypothesize that micromorphy in this region may be an outcome of high predation pressure.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1111/geb.12444
Programmes: BAS Programmes > BAS Programmes 2015 > Biodiversity, Evolution and Adaptation
ISSN: 1466-8238
Additional Keywords: Durophagous predation, latitudinal gradient, rhynchonelliform brachiopods, shell damage, shell repair, tropical, polar
Date made live: 03 May 2016 08:34 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/512087

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