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What animals can be found in the sediment at Canaveral Harbor, and what can they tell us about the age of the sediment?

canaveral sed photo 1

Although harbor sediment is often subjected to physical, chemical, toxicological, and bioaccumulation analyses, the biological properties often go unnoticed and unappreciated during such testing.  What can the biological properties—the critters inhabiting the sediment—tell us about the age and history of the sediment?  An ANAMAR biologist set out to learn just that, by sieving extra material from a recent sediment sampling event at Canaveral Harbor, Florida.

About 12 gallons of extra sediment sampled from Canaveral Harbor, Florida, was wet sieved with a 2-mm screen to uncover modern and fossil animal remains.  The sample matrix was mostly gray-green colored clay which was washed away during the sieving process.  The remaining shell hash component left in the sieve showed that it contained at least the remains of mollusks.  The shells and other hard objects were left to dry over a few week’s time.  The remains were then identified and photographed.

 

So what was found?

The sample contained:

  • Crustacean (crab and shrimp) claws including the purse crab genus Persephona
  • Barnacle shells
  • Echinoid (sea urchin) spines and other remains
  • Mollusk shells
    • Ark shells of the order Arcoida
    • Tusk shells including the genus Dentalium
    • Wentletraps including Epitonium cf. rupicola
    • The limpet Diodora cf. floridana
    • The land snail Polygyra septemvolva (Florida flatcoil)
  • Fish remains
    • A tooth from Carcharhinus isodon (finetooth shark)
    • Vertebrae from teleost (bony) fishes
    • A pectoral spine from the sea catfish family Ariidae

canaveral sed photo2

Are any of these remains fossilized? 

It is not always easy to differentiate a fossil from the remains of modern animals, especially when considering the remains of mollusks having calcium carbonate shells.  However, we can say with certainty that the limpet shell is a fossil because the species Diodora floridana lived only during the Pleistocene (it has been extinct for thousands of years [Peterson and Peterson 2008]).  The Florida flatcoil shells may also represent fossils as they appeared to contain consolidated mineralized material filling the internal voids, and were a much darker than modern shells of this species.  The finetooth shark tooth also represents a fossil although this species still occurs around Florida today.  Most shark teeth found in sediment or on the ground are fossils because, although sharks are abundant in today’s oceans and they continually lose and replace teeth throughout their lives, it takes a build-up of teeth over thousands or millions of years for them to be numerous enough to be easily found. 

Most of the remaining shells are Holocene in age (modern).  Overall, the shells within the sediment range in age from Holocene (recent) to the Pleistocene (12,000 to 2.6 million years ago), based on the taxonomy of the animal remains.  The presence of the land snail Polygyra septemvolva among the remains of the marine animals suggests that the sediment had been mixed with other deposits originating from terrestrial sources.

canaveral sed photo3

Source Cited:

Peterson, C. and B. Peterson.  2008.  Southern Florida’s Fossil Seashells.  Blue Note Publications, Inc., Cocoa Beach, FL.

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