A Simple mass transport model for metal uptake by marine macroalgae growing at different rates

Abstract

A simple mass transport model was developed to describe metal uptake from sea water by marine macroalgae growing at different rates. Although algae growing at different rates may exhibit different concentrations of a given metal, such differences in algal chemistry may or may not reflect actual effects of environmental growth factors on the kinetics of metal uptake. The model was used to interpret published data on uptake of rubidium, cadmium, and manganese by the green seaweed Ulva fasciata Delile grown at different rates (by controlled variation of light and nutrient levels) in open-system sea water. Significant decreases in algal rubidium and cadmium concentrations with increasing specific growth rate μ were attributable entirely to differences in exposure time to sea water of relatively old (low μ) and relatively young (high μ) thalli; biomass-specific rates of uptake of these two metals did not vary with μ. Conversely, both algal concentrations and specific rates of uptake of manganese increase significantly with increasing μ, indicating a distinct link between the kinetics of manganese uptake and metabolic rate.