Where have the mollusks gone?

Part of the research I do in Placencia Lagoon involves monitoring seagrass distributions. One of the ways we do that is to photograph the substrate in the lagoon. The other is to drop an anchor onto the substrate and pull it up to see if bits of seagrass leaf or root are stuck to it. During that process, we also look for other animals that might come up in the muck stuck to the anchor. Those often include bivalve and gastropod mollusks.









This February, we surveyed the lower lagoon, south of Seine Bight and north of Placenia between the airstrip and Mango Creek. Two photographs of the types of mollusks we found. The top photo is of types of dead mollusks we found. The other is of live mollusks.


Two species vs twenty.


To be sure, it is easier to find dead mollusks than live ones. The shells of dead mollusks can stay in the substrate for thousands of years and barely change appearance. But if the live mollusks are still there, where are they??? After 160 anchor drops, you begin to realize that they're not living there anymore. Over the past four years, we've only found about 5 species of mollusks alive in this area.


It's this kind of pattern that leads you to realize how much Placencia Lagoon has changed in recent times. Conditions that allowed for a wide diversity of mollusks have been altered to the point that only a few can live there now.


What else has been lost? What else will we lose?