Research

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Temperature dependence in heterotrophic protist growth and grazing rates

Grazing is the single largest loss factor of marine primary production and thus affects a key transfer rate between global organic and inorganic matter pools. Remarkably, data for herbivorous protist growth and grazing rates at temperatures representative of the vast polar regions and during winter and spring periods are extremely sparse. By combining laboratory experiments Read More …

North Atlantic Plankton Dynamics – contributing to NAAMES

The Menden-Deuer Lab gets to participate in a large, collaborative study resolving key processes controlling the abundance and distribution of phytoplankton in the North Atlantic and of course the ramifications of plankton dynamics for the coupled ocean ecosystem and atmosphere. We were funded to contribute rate measurements on the dynamics of phytoplankton growth and mortality Read More …

The causes and ramifications of intra- and inter specific plankton diversity

As is commonly observed, biology is permeated by variability. In our laboratory and field work, we are consistently puzzled by the high intra!-specific variability observed amongst clones obtained from one population. One aspect of our work is to quantify the degree of intra-specific variability and to distinguish it from the well known variation amongst species. Read More …

Identifying regulatory mechanisms for Heterosigma akashiwo bloom formation: predation interactions with algal behavior and resource use

This project, in collaboration with Suzanne Strom (WWU) and her lab, investigates the regulation of Heterosigma akashiwo blooms by protistan predators. H. akashiwo causes fish kills yearly in coastal waters of the Pacific. Food web interactions involving H. akashiwo, a raphidophyte that may have multiple modes of toxicity, are poorly understood. Our study focuses on Read More …

Deciphering planktonic predator-prey interactions: a mechanistic approach

This research investigates planktonic predator-prey interactions by combining studies of microscopic cell-cell interactions and responses with measurement of population growth and consumption rates. We can then embed these empirical observations in a theoretically-motivated model that identifies the linkages between organismal behaviors and their population-level ramifications. The motivation for this study is that although heterotrophic protists Read More …

Quantifying biological drivers of plankton patch formation

Our field-work aims to determine how much growth and mortality of plankton contribute to the formation of plankton patches, their persistence, and decline. The experiments are mostly done in a shallow, coastal fjord (East Sound, Orcas Island, Washington), and supplemented with seasonal studies in Narragansett Bay, Rhode Island. Combining frequent small-boat surveys with laboratory measurements, Read More …

Effects of protistan herbivory on phytoplankton production

The goal of this research is to develop a mechanistic understanding and predictive capability of the relative importance of biological versus physical processes in driving the magnitude of predation pressure by heterotrophic protists (< 200 µm) on microphytoplankton. Recent work has focused on separating the relative role of temperature and potential prey species composition in Read More …

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 Read More …