Feeding Rate Variation in Purple Urchins

— Written by William Dejesus

My results showed feeding rate variation between trials with and without a 24-hour starvation period. A decrease in consumption rate was consistently observed in trials without the prior starvation period in the warm treatment. The ambient treatment did not show a significant pattern, which could have resulted from a less intense environmental constraint than what the warm treatment experienced.

It appears that consistent food availability could lead to decreased feeding rates. This can be applied to the kelp forest community in that a healthy abundance of giant kelp will prevent large spikes in feeding rate over time. The kelp forest community, like all ecological communities, requires a stable balance of trophic level interaction in order to function properly.

My investigation of the purple urchin’s feeding behavior has lead to the conclusion that the kelp forest community will need more urchin predators, such as the California sheephead in order to maintain the high abundance of biodiversity that it is famous for. Without these key predators, it is likely that urchins will consume kelp at a faster rate, inevitably leading to monoculture urchin barrens. These barrens are unsustainable for almost all species that call the kelp forest home, as well as the purple urchins, who will have eaten themselves out of house and home. Although urchins can survive for long periods of time without abundant food, previous studies have found that urchin health in barrens is extremely low with high potential for widespread disease.

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