Clermont, Chantelle R. (2025) Factors affecting covering behaviour in green sea urchin, Strongylocentrotus droebachiensis. Masters thesis, Memorial University of Newfoundland.
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Abstract
Green sea urchin, Strongylocentrotus droebachiensis, is a major herbivore in the northwestern North Atlantic. It exhibits a poorly understood behaviour coined covering, where it picks up and holds material on its aboral surface. This behaviour is presumed to involve an energetic trade-off with movement and, therefore, must provide some benefit to the sea urchin. Past studies on this species found positive effects of ultraviolet radiation (UVR), wave action, and algal whiplash, and an inverse relationship with size, although there is a lack of consensus on these factors and mostly lab work alone to support these findings. The present study sought to further investigate the factors affecting this behaviour and possible interactions between them as well as to identify spatio-temporal patterns of the behaviour in the field. Two experiments were performed in an oscillatory wave tank to quantify the trade-off between movement and covering and to further investigate the effects of UVR, wave action, and sea urchin size on covering behaviour. Two field surveys were also conducted over time and depth to identify trends in the behaviour and see how storms may alter these trends. There was an inverse relationship between size and covering, but no effect of UVR on covering. Low to moderate wave velocities (0.1 and 0.2 ms⁻¹) induced covering in small sea urchins (1 to 2 cm test diameter), while only moderate velocities induced covering in large urchins (4 to 5 cm test diameter). The inverse relationship between covering and movement was also quantified in one experiment, with sea urchin movement decreasing by ~9 cm for every 10% increase in percent cover. The field surveys showed peak covering in July and August. Increased covering was observed at the sea urchin grazing front in summer months, followed by decreased covering at the front in the fall, corresponding to the formation and de-aggregation of the sea urchin grazing front. Overall, the present study can be used to establish a baseline of covering in relation to these factors (urchin size, wave velocity, and spatiotemporal variations) and could be used to evaluate how covering changes in the future with a changing ocean climate.
| Item Type: | Thesis (Masters) |
|---|---|
| URI: | http://research.library.mun.ca/id/eprint/16966 |
| Item ID: | 16966 |
| Additional Information: | Includes bibliographical references (pages 93-107) -- Restricted until April 24, 2026 |
| Keywords: | covering behaviour, echinoderm, benthic ecology, Newfoundland |
| Department(s): | Science, Faculty of > Ocean Sciences |
| Date: | May 2025 |
| Date Type: | Submission |
| Library of Congress Subject Heading: | Green sea urchin--Behavior--Newfoundland and Labrador; Benthic ecology--Newfoundland and Labrador; Marine ecology--North Atlantic Ocean |
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