Jennifer C. Prairie

Biophysical interactions in the plankton: A cross‐scale review

In plankton ecology, biological and physical dynamics are coupled, structuring how plankton interact with their environment and other organisms. This interdisciplinary field has progressed considerably over the recent past, due in large part to advances in technology that have improved our ability to observe plankton and their fluid environment simultaneously across multiple scales. Recent research has demonstrated that fluid flow interacting with plankton behavior can drive many planktonic processes and spatial patterns. Moreover, evidence now suggests that plankton behavior can significantly affect ocean physics. Biophysical processes relevant to plankton ecology span a range of scales; for example, microscale turbulence influences planktonic growth and grazing at millimeter scales, whereas features such as fronts and eddies can shape larger-scale plankton distributions. Most research in this field focuses on specific processes and thus is limited to a narrow range of spatial scales. However, biophysical interactions are intimately connected across scales, since processes at a given scale can have implications at much larger and smaller scales; thus, a cross-scale perspective on how biological and physical dynamics interact is essential for a comprehensive understanding of the field. Here, we present a review of biophysical interactions in the plankton across multiple scales, emphasizing new findings over recent decades and highlighting opportunities for cross-scale comparisons. By investigating feedbacks and interactions between processes at different scales, we aim to build cross-scale intuition about biophysical planktonic processes and provide insights for future directions in the field.

Physical and biological controls of vertical gradients in phytoplankton

Small-scale vertical heterogeneity in phytoplankton distributions is common in coastal waters and may be a critical feature influencing trophic coupling in planktonic systems. Here we develop a model to investigate the biological and physical dynamics that control vertical gradients in phytoplankton abundance. The model includes phytoplankton layer formation and layer destruction through mixing and predicts that the local maximum scaled phytoplankton gradient is controlled by the relative strengths of these dynamics. We compare the predictions of this model to highly resolved profiles of phytoplankton concentration and fluorescence collected using a free-falling planar laser imaging fluorometer (FIDO-F) and turbulence microstructure profiler data (TurboMAP-L). From these profiles, we estimate the model parameters: the maximum rate of layer formation and minimum possible layer thickness. The maximum rate of layer formation ranged from 0.46 to 0.94d 21 , which is comparable to maximum reported growth rates of the most common phytoplankton taxa found in our samples. The minimum layer thickness estimated from our data suggests that persistent phytoplankton layers thinner than approximately 0.5m may be rare in coastal waters. This study provides a mechanistic explanation for some of the underlying dynamics governing phytoplankton layer formation, maintenance, and destruction and will allow us to better predict the magnitude and occurrence of these ecologically important structures in the field.

Retention and entrainment effects: Experiments and theory for porous spheres settling in sharply stratified fluids

We present an experimental study of single porous spheres settling in a near two-layer ambient density fluid. Data are compared with a first-principle model based on diffusive processes. The model correctly predicts accelerations of the sphere but does not capture the retention time at the density transition quantitatively. Entrainment of lighter fluid through a shell encapsulating the sphere is included in this model empirically. With this parametrization, which exhibits a power law dependence on Reynolds numbers, retention times are accurately captured. Extrapolating from our experimental data, model predictions are presented.

Trophic and Tropic Dynamics: An Ecological Perspective of Tropes

Keeling, a rhetorical scholar, and Prairie, a marine ecologist, investigate the entanglement of two foundational concepts of their requisite fields that share etymological features: trope (τροπη), to turn, and trophe (τροφη), to nourish. They discuss the ways that trophic dynamics in ecology, including symbiotic relationships, demonstrate troping’s interactive and polymorphic qualities. They engage troping as a social, biological, and physical activity that composes ecosystems with and without humans. This project historicizes the interdisciplinary emergence of rhetoric and ecology—and trope and trophe—in the mythopoeic tradition of archaic Greece, while also encouraging interdisciplinary collaboration to address problematic distillations of tropes in academic research and public decision making. An ecological perspective of rhetoric contends that tropes are dynamic and polymorphic modes of environmental expression.