Quantifying effects of plankton behaviors on population dynamics
Organism movement is fundamental to many ecological processes and often dictates relevant biotic and abiotic encounter rates, particularly for planktonic organisms inhabiting a highly dynamic and heterogeneous habitat. Through the development of new methods, my lab is able to observe the cm-scale population distributions of planktonic organisms in the size range of 5-100 µm and simultaneously quantify the three dimensional movement behaviors of dozens of individual cells (Menden-Deuer & Grünbaum 2006). These observations are collected in defined and stable environmental conditions that allow the creation of gradients and patches of external stimuli (e.g. light intensity, resources) and measurement of population growth rates and predation rates in those defined conditions. Therefore, our observations encompass both the causes (e.g. stimulus) and ramifications (e.g. population dynamics) of predator prey interactions. This type of result not only describes the specific predator prey interaction, but also their implication and mechanistic underpinnings. The latter are essential to deciphering the immensely complex marine microbial food webs and ultimately, ecosystem dynamics.
Plankton sensitivity: Our laboratory work has shown that both predator and prey respond very specifically and in a quantifiable manner, to the chemical stimuli released by their respective predators and prey (Harvey et al. 2013), that predator movement behaviors can significantly alter the encounter rates, and ultimately predation rates of protistan predators feeding on phytoplankton (Harvey & Menden-Deuer, 2011). Protistan responses to prey stimuli have been known for over a century of course, our work however quantifies the effects on population dynamics and provides a predictive framework.
Plankton on the run: The motility research also allowed us the exciting discovery that phytoplankton are capable of effectively fleeing from their protistan predators (Harvey & Menden-Deuer 2012). In collaboration with Dr. Suzanne Strom (Western Washington University), we have been able to decipher the interplay between predation pressure and salinity tolerance in driving the abundance and distribution of some coastal phytoplankton species (Strom et al. 2013).
Plankton keep going: Empirical plankton motility data we collected for a wide range of phototrophic and heterotrophic species have provided the foundation to show that plankton movements are highly correlated (Menden-Deuer 2010) and that these correlations are vertically biased (Schuech & Menden-Deuer, 2014). These results allow us for to demonstrate the mechanistic basis for empirically observed diel vertical migrations, and to provide time and space scales over which organism movements can impact ocean biogeochemistry. The latter estimates are essential to integrating the diversity of plankton ecology in large-scale biogeochemical models.
1. Menden-Deuer & Grünbaum 2006
2. Harvey et al. 2013
3. Harvey & Menden-Deuer, 2011
4. Harvey & Menden-Deuer 2012
5. Strom et al. 2013
6. Menden-Deuer 2010
7. Schuech & Menden-Deuer, 2014
Harvey & Menden-Deuer 2012