Our primary field site, at Explorers Cove, Antarctica, is essentially a very conveniently-placed piece of the deep ocean floor. Because the area is bypassed by ocean currents and has a permanent ice cover, it is always still, cold, and dark, even though it's only about 60 feet down to the bottom.
The resemblance does not stop there. Deep-sea environments have relatively few species of the more famous hard-shelled, "calcareous" foraminifera; rather, they are dominated by single-chambered, soft-walled forams called "allogromiids*". In our studies of Explorers Cove forams, we have found that this pattern holds there as well. Further, our research has shown that some forams are a lot harder to find than others.Some foraminifera in Explorers Cove, such as this Astrammina rara cell (arrow), are easy to spot. (This cell is about the size of a BB, not including the "arms", which are called stolons.) Less conspicuous species are more difficult to detect.
Initial studies by Ward et al. (1987) and Bernhard (1987) revealed
a low diversity foram assemblage dominated by small
calcareous taxa; no soft-bodied allogromiids appear in their reports,
and only a few species of single-chambered forams of any kind. They
studied the forams in the Cove by placing the sediment in carbon tetrachloride;
lighter objects, like foram shells, float to the top. We think allogromiids
may not be as buoyant in this system, causing them to be undercounted.
The new field of "molecular ecology" has provided a powerful new way of looking at living communities. Essentially, organisms are identified by their DNA rather than by their morphology. Previous studies (such as this one) screened all of the DNA purified from a volume of water or sediment. While known species were identified, most of the signal was from previously unknown organisms.
Foraminifera are large and well-studied protists, so we were not sure how important this "cryptic diversity" problem would be for us. We modified the environmental-DNA screening technique to detect only foraminiferans, and analyzed sediment samples from Explorers Cove and from the jetty near McMurdo Station. Much to our surprise, we found that at least 75% of the allogromiid diversity at Explorers Cove remains uncharacterized (Habura et al. 2003).