Recent Invasion of a Red Alga (Bangia atropurpurea) in Lake Michigan

Abstract

Bangia atropurpurea was first found on the southwestern shore of Lake Michigan in 1968; by 1976 it had covered suitable substrates on the southern two thirds of the lakeshore. Optimal vegetative growth occurred above the low waterline during the spring and fall, especially near harbor areas. Vegetative growth is initiated from either perennating basal cells or monospores. Bangia contained extraordinarily high concentrations of bromine and zinc, suggesting it requires relatively high levels of halogens and trace metals, which are present in runoff waters and contaminated harbors. Key words: Bangia, invasion, Lake Michigan, halogens, trace metals, algal zonation