Understanding how large-scale processes (>100 kms) influence ecological
communities is currently a major focus in ecology. In marine systems, coastal
upwelling, a large-scale oceanographic process in which surface water pushed
offshore by winds is replaced by cold, nutrient-rich water from depth, appears to
cause variation in rocky intertidal communities. Along the central Oregon coast
upwelling occurs intermittently during the summer while on the southern coast it
begins earlier in the spring and is less variable throughout the summer.
Coastal upwelling can affect rocky intertidal communities by altering the
delivery of nutrients, larvae, and phytoplankton. I conducted three studies on both
the southern and central Oregon coast to understand how differences in upwelling
affect rocky intertidal community structure and dynamics. In the first study, I
examined the recruitment and growth rates of sessile invertebrates (mussels and
barnacles). Recruitment of both mussels and barnacles, and growth of mussels were
consistently higher on the central Oregon coast than the southern coast.
Upwelled water is nutrient-rich, so differences in upwelling are likely to
affect growth rates of macroalgae. In the second study, I tested this hypothesis by
monitoring the growth of two species of intertidal kelp at both central and southern
coast sites. During El Ni��o years, when upwelling is sharply reduced on the central
Oregon coast, algae may fare better at sites on the southern coast where upwelling
is less affected. However, during years when upwelling is strong all along the
coast, nutrient limitation does not appear to differentially affect macroalgal growth
rates.
Finally, in the third study, I examined the influence of upwelling on the
interactions between microalgal primary producers and herbivorous limpets. I
conclude that this interaction is complex and varies both within and between
upwelling regions.
My research suggests that a transition in upwelling from weak and sporadic
on the central Oregon coast to stronger and more persistent on the southern Oregon
coast drives the striking differences in rocky intertidal community structure and
dynamics between these areas. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31529 |
| Date | 24 May 2002 |
| Creators | Freidenburg, Tess L. |
| Contributors | Menge, Bruce A., Lubchenco, Jane |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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