One drawback to clam ring research is that because clams don't live long, only brief growth chronologies can be compiled. UA scientists have been working since 1992 with species of clams in the Chione genus, a genus that lives for no more than 20 years, Schoene estimates. Currently, one of Schoene's main goals is to combine individual annual growth increment chronologies to establish longer master chronologies. Schoene does see one major benefit to sclerochronology lacking in other environmental records. One of the main advantages of bivalve mollusks is that they occur worldwide in the aquatic ecosystems.
Corals grow mostly in tropical seas, and trees only on land.
Scientists plan future studies of Arctica islandica, shells from the North Sea. This species of bivalve mollusks can live for more than 250 years. That life span is long enough to build bivalve mollusk master chronologies needed to reconstruct a few centuries of environmental history, Schoene said.