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Sub-surface hotspots in shallow seas: fine-scale limited locations of top predator foraging habitat indicated by tidal mixing and sub-surface chlorophyll

Scott, B. E.; Sharples, J.; Ross, O. N.; Wang, J.; Pierce, G. J.; Camphuysen, C. J.. 2010 Sub-surface hotspots in shallow seas: fine-scale limited locations of top predator foraging habitat indicated by tidal mixing and sub-surface chlorophyll. Marine Ecology Progress Series, 408. 207-226. 10.3354/meps08552

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Abstract/Summary

The foraging habitats of 7 species of marine apex predators were observed simultaneously in a shallow sea, with continuous measurements taken of the detailed bio-physical water column characteristics to determine habitat preferences. We found the occurrence of small-scale 'hotspots', where 50% of all animals were actively foraging in less than 5% of the 1000 km of transects surveyed. By investigating a contrasting range of foraging strategies across a variety of fish-eating seabirds and marine mammals, we determined which habitat characteristics were consistently important across species. A static habitat variable, tidal stratification, log(10)(h/U-3) (h = water depth, U = tidal current amplitude), was found to be the best indicator of the probability of presence and abundance of individual species. All 7 mobile top-predators preferentially foraged within habitats with small-scale (2 to 10 km) patches having (1) high concentrations of chlorophyll in the sub-surface chlorophyll maximum (CHLmax) and (2) high variance in bottom topography, with different species preferring to forage in different locations within these habitats. Patchiness of CHLmax was not associated with the locations of strong horizontal temperature gradients (fronts) or high surface chlorophyll values, but instead may be related to areas of high sub-surface primary production due to locally increased vertical mixing. These small-scale areas represent a newly identified class of spatially important location that may play a critical role within the trophic coupling of shallow seas. Such subsurface hotspots may represent the limited locations where the majority of predator-prey interactions occur, despite making up only a small percentage of the marine environment.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.3354/meps08552
ISSN: 0171-8630
Additional Information. Not used in RCUK Gateway to Research.: Scott, B. E. Sharples, J. Ross, O. N. Wang, J. Pierce, G. J. Camphuysen, C. J. Eu [q5rs 2000-30864, mexc-ct-2006-042337]; nerc [ne/f001983/1] Funding for original fieldwork was via EU Q5RS 2000-30864, IMPRESS (Interactions between the Marine Environment, Predators and prey: implications for Sustainable Sandeel fisheries). Funding for extended work was provided by NERC Sustainable Marine Bioresources programme NE/F001983/1; G.J.P. was funded under the EU Marie Curie programme (MEXC-CT-2006-042337). Special thanks to the crew of the 'Pelagia', especially Martin Laan and Santiago Gonsalez. Bird/sea mammal observers: Suzan van Lieshout, Luc Meeuwisse, Phillip Schwemmer and Nicole Sonntag. Volunteers for oceanography: Jackie Smith, Damion Nixon and Dr. Patrick Holligan (University of Southampton) for the analysis of the chlorophyll samples. Very special thanks for great efforts from FRS Marine Lab, Aberdeen: John Dunn and Eric Armstrong. We thank Dr. Lisa Ballance and 2 anonymous reviewers whose suggestions enhanced the work. We also acknowledge C. D. Macleod for extracting and configuring the BGS data and Proudman Oceanographic Laboratories for the use of POLPRED. Inter-research Oldendorf luhe
Additional Keywords: BIOLOGICAL HOTSPOTS; FORAGING HABITATS; MARINE TOP PREDATORS; PREDATOR PREY INTERACTIONS; SHALLOW SEAS; SUB SURFACE CHLOROPHYLL MAXIMUM; TIDAL MIXING; TOPOGRAPHY; EASTERN TROPICAL PACIFIC; BOTTLE NOSED DOLPHINS; HARBOR PORPOISES; GEORGES BANK; FISH LARVAE; NORTH SEA; IRISH SEA; FRONTS; SEABIRDS
NORA Subject Terms: Marine Sciences
Date made live: 26 May 2011 15:07
URI: http://nora.nerc.ac.uk/id/eprint/13950

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