THE PROPAGULE BANK AS AN EXPERIMENTAL TOOL IN FORAMINIFERAL ECOLOGY (Invited Presentation)

Earl Myers reported in 1940 that the occurrence of small flagellated gametes in foraminifera is important not only in understanding why the proloculus of the microspheric generation is so small, but also in that the release of gametes into the water column might “provide a brief pelagic phase” thus assuring wide dispersal. More recently, we have shown that juveniles from both the asexual and sexual generations of the life cycle may undergo dispersal, but that sexually produced juveniles appear to disperse more widely. These small juveniles, or propagules, settle to the ocean floor and form a “bank” in marine sediments. This propagule bank, broadly analogous to a seed bank, may include juveniles derived from local populations as well as those originating from distant sites. Further, propagules of some species may remain in a cryptic or dormant state for months or even years under conditions that are suboptimal for their growth. The foraminiferal propagule bank can be separated from adult foraminifera and other larger members of the benthos by sieving, thus providing a novel tool that can be experimentally manipulated in the lab to address a range of ecological questions. By growing assemblages of benthic foraminifera from propagule banks under controlled environmental conditions, we can ascertain the responses of select species to a specific range of conditions such as temperature, salinity, pH, or the type of food resources. We can also examine the responses to individual pollutants or contaminants at known concentrations. By focusing on the responses of juveniles as they grow to adults, this approach is consistent with studies that use invertebrate larvae to assess responses to contaminants or perturbations. This experimental approach provides a tool for assessing the distance over which different taxa disperse by identifying allochthonous taxa that grow from propagules at a given site. It further provides insight into the identity and characteristics of opportunistic taxa. Supported by US NSF grants 0850505 to STG and 0850494 to JMB.