Posted by: Doc Bruce | February 20, 2008

What’s That Blob on the Beach? My Long-lost Aunt Sally?

For the past few weeks at Sanibel Sea School, we have been seeing a lot of blobs on the beach. They range in color from pink to grey to black. They are sometimes flat as a pancake, or globular or round. Most have a firm, rubbery consistency. They are very common in deeper waters (20-30 feet) offshore and in seagrass beds of San Carlos Bay.

They are a type of invertebrate animal – those without a backbone. Strangely enough, they are among the most sophisticated of invertebrate animals; and as such those most closely related to humans. Yes, that blob may just be your long lost Aunt Sally! They belong to the phlum Chordata and the subphylum Urochordata; collectively these groups of fascinating animals are commonly called tunicates or ascisdians by biologists or just sea squirts by just normal people.
The species we are most commonly seeing are called sea ham or sea pork and most belong to the genus Amaroucium . They are called sea ham because of their resemblance to salted pork common in the diets of early sailors. Which is perhaps another reason to just be happy in our world of fast-paced, crazy technology – at least our main staple doesn’t resemble the blobs washing up on our shores!

For those of you more familiar with our back-bay environments, it is closely related to a white encrusting tunicate commonly wrapped around the tips of seagrass blades.
These tunicates in all likelyhood play an important role in our ecosystem. Their rich abundance is associated with eutrophication – the nutrient enrichment of natural waters. For local residents, we are all too familiar with the saga of eutrophication; but fear not, this is not another tale of doom and gloom. Our tunicate abundance is probably a logical next-step in our enrichment process. They are filter feeders and do well in areas that have seen extensive enrichment. In short, we are moving up the food chain – we started with plant proliferation (can you recall red drift algae) and have now shifted to animals that can capitalize on the perpetual flow of energy through the sea.

In fact, tunicates are such efficient filter feeders, that their high abundance is probably contributing significantly to our very clear waters. Combined with a lack of rainfall bringing more nutrients into our marine ecosystems, these creatures are filtering out the bacteria and microscopic plants that make our waters less clear.

The wonders of the ocean are endless. The ripples of change are intricate and not often easily predictable, but almost always fascinating to observe.

Join us at Sanibel Sea School to help conserve our ocean legacy for our future. Or at least, take a few moments to get out and discover the wonders of nature – the computer will wait, the sea will change.


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