Sea Cows and Seagrasses: how methods recently developed by scientists can help us understand present and prehistoric feeding habits and what they tell us about the environment of those times

In modern ecosystems, sirenians (i.e. manatees and dugongs) are the dominant large-bodied consumers of seagrasses in coastal communities. This association has been presumed to extend into the past, and occurrences of sirenian remains in deposits have been interpreted as evidence of the presence of seagrasses in ancient marine ecosystems, thus helping scientists get a better picture of marine life at that time.

The diet of sirenians is reflected in the composition of the tooth enamel. By checking the carbon isotopes within the teeth of both modern and early sirenians it is possible to determine which aquatic vegetation types were consumed, as different plants carry different levels of this isotope. Like a marine detective story, it is possible to use the clues from this procedure to tease out answers about the food habits of early sirenians and also give an overview of the marine plants which were flourishing in earlier times, and from that gain a sense of what the marine ecosystem could have been like during Eocene times. Another interesting part of this study is that the Steller's Sea Cow formerly occurred in Monterey Bay.

This is a fascinating story of how modern science, using new and sophisticated methods, can answer questions which have previously been an enigma. Mark will also give us an overview of modern sirenian ecology.

ACS/MB helped support Mark's research with one of our grants and we are delighted to be able to have him come and speak to us.

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