Marine ecosystems can be exposed to natural and anthropogenic disturbances
that can lead to ecological failures. Marine reserves have been lately suggested to
protect marine populations and communities that have been affected by habitat
destruction and harvest. This research evaluates the potential role of two marine
reserves established in Oregon in 1967 (Whale Cove) and 1993 (Gregory Point). The
red sea urchin (Strongylocentrotus franciscanus) was selected as indicator of
population recovery since it is the only species that is commercially harvested.
Changes in density, biomass, average size, size structure, growth and mortality rates
were evaluated through time to assess population recovery. These parameters were
also compared between reserves and adjacent exploited areas to evaluate the effect of
exploitation. Results from Whale Cove (old reserve) indicate that the population in
this area is fully recovered. On the contrary, the population in Gregory Point (new
reserve) showed signs of recovery after six years of being protected. The importance
of red urchins as source populations to provide larvae to adjacent areas was explored
by the analysis of drifter's trajectories. Both reserves might be connected in a network
where larvae produced in Whale Cove will provide recruits to Gregory Point and
adjacent exploited areas, as well as populations in northern California. Gregory Point
releases larvae that become recruits for Whale Cove only when spawning takes place
in winter, otherwise larvae travel to central California. No clear trends were found in
growth and mortality rates between reserves and non-reserves; differences were more
related with food availability, competitors, and age specific mortality.
We applied qualitative simulations to characterize and differentiate the
community network inside reserves and exploited areas. Results suggest that
communities from a particular site can be represented by a set of alternative models
with consistent species interactions. Differences in predator-prey interactions as well
as non-predatory relationships (interference competition, mutualism, amensalism)
were found among sites. Each set of models represents a hypothesis of community
organization that agreed with natural history information. Alternative models suggest
that kelp forest communities are dynamic and can shift from one network
configuration to another providing a buffer against a variable environment. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32477 |
| Date | 20 December 2001 |
| Creators | Moctezuma, Gabriela Monta��o |
| Contributors | Li, Hiram W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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