Environmental and biological drivers of feeding and spatial dynamics in the green sea urchin, Strongylocentrotus droebachiensis

Frey, Desta L. (2016) Environmental and biological drivers of feeding and spatial dynamics in the green sea urchin, Strongylocentrotus droebachiensis. Masters thesis, Memorial University of Newfoundland.

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In eastern Canada, the destruction of foundational kelp beds by dense aggregations (fronts) of the omnivorous green sea urchin, Strongylocentrotus droebachiensis, is a key determinant of the structure and dynamics of shallow reef communities. Current knowledge about factors affecting the ability of S. droebachiensis to exert top-down community control is based largely on observational studies of patterns in natural habitats, yielding fragmentary, and sometimes contradictory, results. The present research incorporated laboratory microcosm experiments and surveys of urchins in natural habitats to test the effects of abiotic (wave action, water temperature) and biotic (body size, population density) factors on: (1) individual and aggregative feeding on the winged kelp, Alaria esculenta; and (2) displacement, microhabitat use, distribution, and aggregation in food-depleted habitats. Wave action, water temperature, and body size strongly affected the ability of urchins to consume kelp: individual feeding increased with increasing body size and temperature, while aggregative feeding decreased with increasing wave action. Yet, feeding in large urchins dropped by two orders of magnitude between 12 and 18°C. Increasing wave action triggered shifts in urchin displacement, microhabitat use, distribution, and aggregation: urchins reduced displacement and abandoned flat surfaces in favour of crevices. They increasingly formed two-dimensional aggregations at densities ≥110 individuals m⁻². Collectively, results provide a foundational understanding of some of the drivers of feeding and spatial dynamics of S. droebachiensis and potential impacts on the formation of grazing fronts.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/12054
Item ID: 12054
Additional Information: Includes bibliographical references (pages 132-149).
Keywords: green sea urchin, feeding, spatial dynamics, wave action, sea temperature, habitat use, urchin-kelp bed dynamics, urchin barrens
Department(s): Science, Faculty of > Biology
Date: April 2016
Date Type: Submission
Geographic Location: Canada, Eastern
Library of Congress Subject Heading: Green sea urchin--Habitat--Canada, Eastern; Green sea urchin--Food--Canada, Eastern; Kelps--Effect of grazing on--Canada, Eastern; Green sea urchin--Geographical distribution

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