Variety in the Benthos

A few weeks ago, I showed a picture identifying some differences between the marine lab sediments and the Panama City Beach sediments, specifically differences in oxygenation and material retained on the large sieve. There are multiple ways to assess differences between sediments, including sediment grain size, pore water chemistry (dissolved oxygen, nitrogenous compounds, phosphorus, etc.), and the fauna that live in and on the sediment. Like all comparative methods in the sciences, identifying differences requires data and statistics, but visual cues can help scientists learn about the systems that they are studying.

This week as I was processing more samples from the marine lab, I noticed that there were a lot of small organisms retained on the large sieve. Any fauna retained on the larger sieve are macrofauna or megafauna, two of the four size classes assigned to marine organisms. Macrofauna are generally classified as organisms smaller than 1 cm and larger than 250 micrometers, whereas megafauna are organisms larger than 1 cm. Some scientists classify megafauna as any animal that can be seen without a microscope (in case you can't easily visualize how small 1 cm is). Although I am not interested in the types of mega- and macrofauna in the sediment samples I collect, finding interesting remnants from larger marine organisms is always a treat. In my work so far I have found shark teeth, bivalve shells, and seagrass and algal fragments. Today, however, I found the newest--and maybe coolest--item to date in my samples.

The animal in the bottom left corner of the image is a brittle star, potentially a mini brittle star--though I would need to look at it closer to make a better judgment. For scale purposes, the body of the brittle star shown, not counting its arms, is approximately 3 cm across. Brittle stars are related to sea stars and are important marine invertebrates, especially in Florida. Brittle stars can be found wrapped around coral branches where they may brush away sediment or harmful particulates while feeding. Brittle stars are also seen in aquariums where they form a component of the aquarium clean up crew, feeding on small particulate matter and are relatively uninterested in other aquaria species. It is unfortunate that this little brittle star was caught in our sediment core, but it provides me with a great opportunity to share about this fascinating marine organism. 

I hope that by showing some of the marine fauna that don't get screen time in films like Finding Nemo and ocean documentaries that people will realize that there's so much out there that we should be learning about and that our actions are affecting more than just dolphins, seals, whales, sharks, and corals; we cause changes that start at the bottom of the ecosystem in the sediments and work their way up to the large animals that we know and love.

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