A Diverse World in the Northern Gulf of Mexico: Louisiana vs. Alabama

Post by Adam Limoges (Colgate '24).

The difference in the diversity of living organisms between our Louisiana and Alabama sampling sites in the Gulf of Mexico was quite stark. In Louisiana, after sieving through mounds and mounds of silt and clay, you finally got your assemblage of live and dead organisms but found only a few common species of living bivalves. In Alabama however, the sandy seafloor sediment passed through the sieve in a flash, and the samples yielded a much wider variety of bivalves, with the species found in Louisiana present, but no longer dominant.

Looking at the other living organisms that surfaced with the box cores, you can again see this difference in diversity. In Louisiana, we would pull up mainly polychaete worms and maybe an occasional brittle star or sea cucumber. In Alabama, we were pulling up all sorts of crabs and sea stars, as well as polychaete worms, brachiopods, and more. The array of sea creatures we saw offshore Dauphin Island was exciting and provided welcome breaks to check out something cool.

Along with the living creatures we found in our samples, we were visited by many other organisms on land and at sea. In Louisiana, we saw many dolphins jumping and playing around the boat in Terrebonne Bay. We were also tailed by many terns and a few other birds. There were also many birds, like rails, around LUMCON and plenty of little crabs scuttling around the lab. In Alabama, there were many of the same birds as in Louisiana and we also saw dolphins out in the Gulf, but we also got to see sea turtles, many different fishes, and even a small shark caught on the beach.

After visiting these two locales along the northern Gulf of Mexico, the differences in the diversity of living creatures–whether bivalves, other sea life, or birds–stuck out to me. Seeing the abundance of different organisms and species in Alabama following the more limited number seen in Louisiana was fascinating and fun while we worked our way through the day's samples. In Florida, we expect the trend of increasing diversity to continue in the living bivalves as well as in the other living sea creatures we find. As we move further from the Mississippi River delta the sediment is likely to remain sandy, similar to Alabama.