Ecotypic differentiation of Laminaria longicruris in relation to seawater nitrate concentration

Abstract

Genetic differentiation of Laminaria longicruris populations has been demonstrated in nitrate-poor (St. Margaret's Bay) and nitrate-rich (Bay of Fundy) regions of Nova Scotia, Canada. At 9°C half-saturation constants for growth (Ks) were smaller (1.1 μM NO 3 - ) for St. Margaret's Bay plants than for plants from the Bay of Fundy (2.3 μM NO 3 - ). Maximum specific growth rate (μmax) and maximum uptake rate (Vmax) were higher for St. Margaret's Bay than for Fundy plants. However half-saturation constants for nitrate uptake (Km) were similar for plants from the two populations. The capacity to accumulate nitrate in an internal tissue pool was larger in St. Margaret's Bay plants than in Fundy plants. The differences among the populations are thought to be adaptive responses to the local nitrate environments.