Analysis of Stylasterid Corals
By Robin Cobb
University of Alabama
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A colony of Stylaster erubescens.
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The skeletons of marine organisms often contain information about their life history and surrounding environment. Decoding this information relies upon chemical and physical clues within a skeleton. Examples of these skeletons include fish ear structures (otoliths), clam shells, and some plankton (like foraminifera). The data in these skeletons can be used to determine migration patterns, growth rate, water temperature, and other information. These skeletons can be viewed as data recorders, much like “black boxes” used in airplanes, constantly adding new data as time passes. The key to using these skeletal archives is to first understand the chemical and physical “language” each uses.
To do this scientists perform detailed studies of how the animals make skeletons (biomineralization), how skeletons grow over time (sclerochronology), and how their different chemical properties form (biogeochemistry). We will be performing this type of work on deep water Stylasteridae corals. Since there are so many mysteries about the deep ocean, it would be useful to understand the records contained in the corals that live there. However, the chemical properties of most of deep water corals are complex and don’t contain clear records of environmental conditions. For example, variations in oxygen isotopes (oxygen atoms of slightly different mass) are useful recorders of water temperature in many calcium carbonate skeletons, one example is coral skeletons, but they do not record temperature data in the types of deep ocean corals studied so far. However, oxygen isotopes in deep ocean Stylasteridae corals have not yet been thoroughly examined and preliminary data indicate they may be useful as environmental data proxies.
Similarly, Stylasterids do not have simple growth lines and their skeletal structures do not resemble other corals. Imaging we have performed via scanning electron microscope (SEM) shows that the family Stylasteridae does not always have clear growth bands that one would expect to see. In some other corals these growth bands resemble tree rings, but this is not always true in Stylasterid corals.. The lack of growth bands may make it more difficult to determine growth rate. SEM imaging has also shown that the internal crystal structure of the calcium carbonate skeleton are not as well organized as some other deep water coral species.
On this cruise we hoped to gather samples and data that will permit us to analyze these corals and ultimately use their data to answer questions about how long they live, how fast they grow, and perhaps measure past environmental variation using fossil samples. We were not able to collect any live samples on this cruise although water samples collected may give us insight into samples collected on a previous cruise.
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SEM image of a longitudinal section of Stylaster erubescens.
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