Meeting Abstract

S1-5.6  Jan. 6  Flow, temperature and the speed of life ELLERS, O; Bowdoin College, Maine oellers@gwi.net

On page one of his seminal work “Life in Moving Fluids” Steven Vogel describes a biologist who “goes forth, thermometer in hand, and measures the effects of temperature on every parameter of life”, perhaps with “Arrhenius abused” in the process. “Temperature,” notes Vogel, “is, after time, our favorite abscissa.” But “few of us measure the rate at which fluids flow, however potent the effects of winds and currents on our experimental systems.” Vogel, of course, introduced a paradigm shift that started a significant expansion in the consideration of flow. In my presentation I come full circle and consider how flow and temperature alter the speed of life, abusing Arrhenius in the process. Flow alters the speed of life because it affects transport of oxygen to animals and thereby alters the scaling exponent of metabolic rate with mass. Thus, for example, lower rates of transport of oxygen to small benthic animals low in a boundary layer may cause a slowdown in growth. Generally, changes in the metabolic scaling exponent will change the time to grow to 2/3 maximum size and thus change the pace or speed of life. Temperature alters physical parameters such as viscosity, enzyme kinetics and the anabolic von Bertalanffy transport coefficient in ways that change maximum size and fractional maintenance costs. These latter two variables are, of mathematical necessity, negatively correlated in the von Bertalanffy description of growth. I present data from sea urchins confirming this negative correlation; indeed, this negative correlation has been generally found for a wide range of organisms. The Arrhenius equation can be used to minimize scatter in this negative correlation, 30% of which is due to temperature. Thus, both flow and temperature alter the pace of life for marine ectotherms.