Plankton species biology and ecology in an Earth System Science context


***Monday June 4, 2012
Redfield Auditorium - 12:00 Noon
Dr. Phillip Assmy
Norwegian Polar Institute

Marine phytoplankton accounts for about half of global primary production, constitutes the base of marine food webs and drives biogenic elemental cycles. The major branches of this evolutionarily highly diverse trophic level are represented by comparatively few dominant species, responsible for most of the action in elemental cycling, while the vast majority of species stays at background levels. Yet, we know relatively little about the biology and ecology of these key species. Phytoplankton species cover a size range similar to that of land plants (from mosses to trees), come in a vast array of shapes and life cycle strategies and exhibit shifting annual patterns of species succession. Clearly, we need to examine the species level and not just the functional levels in order to understand the relationships between ecology and biogeochemistry. Unfortunately, little is known about the differences in traits which distinguish the dominant species from each other because lab experiments cannot adequately reproduce the mortality environment and do not reveal performance under natural conditions. I have derived traits of phytoplankton species from quantitative visual observation of the species population behavior over periods of weeks during targeted in situ experiments and from life cycle studies of dominant species in culture. This includes the enumeration of empty and broken diatom frustules that provide unprecedented insights into diatom mortality at the species level and illustrate the important role of pathogens, parasitoids and predators in phytoplankton seasonal dynamics apart from competition for limiting resources. I will conclude the talk with a brief outlook on possible future projects in plankton biology and ecology of polar oceans at WHOI which I will further detail during a subsequent seminar the following day.