DORMANCY IN THE FORAMINIFERA: IMPLICATIONS FOR THE PAST, PRESENT AND FUTURE

The Foraminifera are a diverse class of protists whose ubiquity in marine environments, small, calcium carbonate shells, and ease of collection have made them critical tools in bioindicator, bioassay, paleoenvironmental, and paleoceanographic research. Despite the plethora of applications and accompanying literature on foraminifers, many aspects of their biology and ecology are unexplored. One of these aspects is dormancy, a life-history strategy involving suspension of active life, arrested development, and reduced or suspended metabolic activity, mediated either by internal physiological factors (known as diapause) or exogenous factors (known as quiescence). Despite anecdotal and circumstantial evidence, very little research has directly addressed this aspect of foraminiferal biology. The relatively recent discovery of cryptobiotic propagules has revealed a fundamental role for dormancy in the life cycles of foraminifers, most prominently for dispersal. Moreover, culture studies with environmental applications have shown that post-propagule quiescence (i.e., in juveniles, subadults and adults) may be a common response to environmental stressors, allowing rapid recovery of populations following disturbance or otherwise unfavorable conditions. Observations indicating the potential for dormancy have been recorded for at least six decades, and that this potential is well represented throughout the class in a variety of forms, suggesting that dormancy may be a basic adaptation in the Foraminifera. If dormancy is as widespread as the literature suggests, its role in structuring foraminiferal assemblages and determining global distributions is fundamental. Recognition that cryptobiotic propagules and post-propagule quiescence are basic adaptations provides new perspectives to understand range expansion under changing climate regimes in the geologic record, in modern environments (e.g., Lessepsian invasives that have literally altered coastal sedimentation in the Mediterranean Sea), and predictions of range expansion in the near future as global climate and water temperatures warm.