Iguana Media Project

Here's the media presentation to re-submit to Kiho since the last one was not up to snuff. Let me know what you think. I can always tinker with it some more if you don't love it.

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Article Summary

I just wrote this summary as I read the article. Beware of grammatical errors. We can take screen captures of most of the pictures (graphs) in the article for the powerpoint next week. I have also included a couple videos of marine iguanas swimming around and eating if we wanted to include it.

Severe Effects of Low-Level Oil Contamination on Wildlife Predicted by the Corticosterone-Stress Response: Preliminary Data and a Research Agenda

Scientists measured corticosterone as a way of quantifying stress levels in marine iguanas after the tanker “Jessica grounded”. Low amounts of oil in their main food source of marine algae killed off algae in the intestines of the marine iguanas leading to starvation, and ultimately death.

Corticosterone-Stress Response

Glucocorticoid is a steroid hormone released by all types of vertebrates when exposed to harmful or stressful stimuli. Corticosterone is the primary glucocorticoid in reptiles. In the short-term, glucocorticoids provide benefits allowing the animals to cope with various stressors. While these hormones are essential for survival, exposure to the glucocorticoid for an extended period of time can shut down the reproductive and immune systems.

Galapagos Marine Iguanas: A Case Study

Marine iguanas were chosen in this study to serve as a model species because so many of the island populations react differently to stressors but the iguanas see very sensitive. A single El Niño season can destroy 90% of their population from loss of algae due to warmer water temperatures for extended periods of time. Scientists measured levels of corticosterone immediately after capture and then again 15-30 minutes later. It takes a few minutes for corticosterone to be released so the first samples taken are assumed to be without the stress of capture.

The study did show increased corticosterone levels during El Niño seasons. Those with high levels were in poor body condition. The levels were different at each island because of how differently each island is affected by El Niño but the overall stress-induced corticosterone levels correlated with the predicted overall population health.

A Low-Level Oil Spill: High Wildlife Mortality Confirming the Stress Predictions

By coincidence, blood samples were taken 3 days before the oil tanker “Jessica” ran ashore. Samples were taken again 7 days after the spill to measure changes in corticosterone levels. Both baseline and post-capture levels of corticosterone were much higher than they were prior to “Jessica”. External oil patches on animals did not appear to correlate significantly in any way with corticosterone levels.

By using the mortality rates determined by corticosterone levels from the El Niño study, scientists predicted the mortality rates of iguanas after the oil spill. 40% mortality rate was expected but a year later, 62% had died. Due to the lack of immediate deaths, media reported that the spill was not that damaging, when in fact the damages were just taking longer to arise.

Further Research Needs

• “How are wildlife populations in diverse habitats affected by trace oil contaminations?”
• “What is the exact chain of causation that kills animals after low-level oil contamination, and is corticosterone playing a direct role?”
• “How good a predictor is the corticosterone stress response for survival in other animal populations?”

Summary and Conclusions

This study revealed the longer-term effects of oil spills. It also provided a functional corticosterone-to-survival relationship to help predict population health as well as the effects of human interference as a stressor.

Article for Monday's Assignment

Hey guys, the article that Ailey found for us to use can be accessed through Google. If you search:

"Severe Effects of Low-Level Oil Contamination on Wildlife Predicted by the Corticosterone-Stress Response: Preliminary Data and a Research Agenda"

you will be able to download the PDF. It is the 3rd or 4th link down.

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