Life history traits and population processes in marine bivalve molluscs
Citable URI
https://hdl.handle.net/1912/4785DOI
10.1575/1912/4785Abstract
In this thesis, I investigated the how the life history characteristics of the clam Mya
arenaria determine the population response to chronic contaminant exposure. To
predict the potential responses of a broadcast-spawning life history such as that of
M. arenaria, I surveyed the literature on a variety of bivalve species. By incorporating
information on growth, survival, and reproduction into matrix population models I
could evaluate the relative contributions of these factors to fitness. For broadcast-spawners,
long life is an important factor enabling them to gamble on rare, large
recruitment events. Another important aspect of the broadcast spawning strategy is
the possibility of high variation in larval settlement from year to year. I evaluated
the role that this variability plays using a stochastic matrix model, and showed that
it tends to increase population growth because of the larger size of rarer, successful
recruitment events.
With an understanding of how the life history traits of M. arenaria might control
its responses to change in the environment, I analyzed the vital rates of clams at
clean and contaminated sites. The effects of contaminants measured in the lab do
not necessarily predict population condition in the field. Since surviving with a long
life span contributes the most to fitness in broadcast-spawning bivalves, effects on
reproductive output and juvenile survival, which are strong in many lab studies, may
not necessarily playa large role in field populations. The life history of this clam, with
natural variation in recruitment from year to year, further reduces the population dependence on high reproductive output and larval survival. The combination of
little population-level relevance of the strongest contaminant effects, and potential
contaminant effects on very important clam predators, could explain why populations
at contaminated sites are observed to be growing the fastest. The interaction of
contaminant exposure and normal ecological processes determines the overall impact
on the population.
Description
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1998
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Suggested Citation
Thesis: Ripley, Bonnie J., "Life history traits and population processes in marine bivalve molluscs", 1998-02, DOI:10.1575/1912/4785, https://hdl.handle.net/1912/4785Related items
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