Aquatic ecosystems are populated by thousands of species of microorganisms that interact in complex microbial food webs. These minute species comprise much of the base of pelagic food webs in marine and freshwater ecosystems. In addition, many microorganisms are important predators in the first few trophic links within food webs, and thereby contribute to the trophic transfer of energy to larger organisms, and to decompositional processes that remove waste and return nutrients for continued growth of photosynthetic organisms. Thus, a thorough understanding of the biology and ecology of microbial species is essential because of their fundamental role in aquatic ecosystems.
What are protists?
Most of the research in our laboratory focuses on the biology and ecology of Protists. This term refers to eukaryotic organisms that are capable of existence as single cells, and therefore are structurally more complex than bacteria and archaea. Although they have much in common with the cells of multicellular species, protists are separated functionally (although not necessarily evolutionarily) from large organisms by their ability to exist as single cells. The older terms ‘microalgae’ and ‘protozoa’ are often still used to refer to these species.
Basic biology, ecology and nutrition
Most protists are microscopic, ranging in size from approximately 1 micrometer (1 µm ~ 0.00004 inch) to a few hundred micrometers (~0.008 inch), although a few species attain sizes of a few centimeters (~1 inch). Some species participate with other micro- or macroorganisms in mutualistic relationships (in which both partners benefit), commensal relationships (in which one partner benefits and the other is neither benefited nor harmed) or parasitic relationships (in which one partner benefits and the other is harmed). Protistan parasites constitute some of the most debilitating and deadly diseases known to humans (e.g. malaria, African sleeping sickness). Nevertheless, the vast majority of protists are free-living species occurring not only in marine and freshwater ecosystems but also in soils and sediments throughout the world. Collectively, protists constitute an enormously abundant and diverse group of species.
Protistan species obtain their nutrition via photosynthesis, heterotrophy (utilization of preformed organic material, usually by engulfing prey), and mixtures of both types of nutrition. The older terms ‘microalgae’ and ‘protozoa’ are often still used to refer to species that have plant-like or animal-like nutrition, respectively, while those that are able to conduct both processes in a single cell are referred to as mixotrophic species.
Reproductive potential for protists is very high (relative to other eukaryotic organisms). The primary of reproduction in most protistan species is binary fission, although sexual reproduction also occurs in most species. In binary fission, an individual cell increases in size as it incorporates new cellular material (via photosynthesis or the consumption of food). Eventually the cell undergoes replication of the genetic material by mitosis (and other essential cellular components), and then splits into two independent cells. This process can occur several times per day in smaller protists. This ability to grow and reproduce rapidly under favorable conditions allows some species to reach high abundances in some ecosystems. For example, some microalgae form ‘blooms’ of very high abundance in some aquatic ecosystems when nutrient and light conditions are conducive to growth.
What We Do
Our lab conducts a variety of research programs that involve specific aspects of aquatic microbial ecology that focus on the role of protists. These projects often entail extensive field work as well as laboratory-based experiments. Whether conducted on ships, from land-based research stations or in the lab, these investigations are focused on measurements of biodiversity (numbers of species and their relative abundances within ecosystems), biogeography (the distribution of species in time and space), life history (strategies of species for survival) and physiology (rates of feeding, respiration, growth and excretion) of protists in nature. Ultimately, our goal is to provide an accurate description of the roles that these populations play in the production and utilization of energy, and the cycling of elements in oceanic and freshwater environments.
The study of aquatic microorganisms
Most protists are microscopic, ranging in size from approximately 1 micrometer (1 µm ~ 0.00004 inch) to a few hundred micrometers (~0.008 inch), although a few species attain sizes of a few centimeters (~1 inch). Some species participate with other micro- or macroorganisms in mutualistic relationships (in which both partners benefit), commensal relationships (in which one partner benefits and the other is neither benefited nor harmed) or parasitic relationships (in which one partner benefits and the other is harmed). Protistan parasites constitute some of the most debilitating and deadly diseases known to humans (e.g. malaria, African sleeping sickness). Nevertheless, the vast majority of protists are free-living species occurring not only in marine and freshwater ecosystems but also in soils and sediments throughout the world. Collectively, protists constitute an enormously abundant and diverse group of species.
Reproductive potential for protists is very high (relative to other eukaryotic organisms). The primary of reproduction in most protistan species is binary fission, although sexual reproduction also occurs in most species. In binary fission, an individual cell increases in size as it incorporates new cellular material (via photosynthesis or the consumption of food). Eventually the cell undergoes replication of the genetic material by mitosis (and other essential cellular components), and then splits into two independent cells. This process can occur several times per day in smaller protists. This ability to grow and reproduce rapidly under favorable conditions allows some species to reach high abundances in some ecosystems. For example, some microalgae form ‘blooms’ of very high abundance in some aquatic ecosystems when nutrient and light conditions are conducive to growth.
Our lab conducts a variety of research programs that involve specific aspects of aquatic microbial ecology that focus on the role of protists. These projects often entail extensive field work as well as laboratory-based experiments. Whether conducted on ships, from land-based research stations or in the lab, these investigations are focused on measurements of biodiversity (numbers of species and their relative abundances within ecosystems), biogeography (the distribution of species in time and space), life history (strategies of species for survival) and physiology (rates of feeding, respiration, growth and excretion) of protists in nature. Ultimately, our goal is to provide an accurate description of the roles that these populations play in the production and utilization of energy, and the cycling of elements in oceanic and freshwater environments.