Nutrients and Plant Biomass in Australian Estuaries, with Particular Reference to South-western Australia

Abstract

An estuary is defined as that part of a river system in which the level or salinity of the water may be affected by that of the sea. The productive fringing marshes may contain much of the plant biomass and nutrients. Submerged angiosperms and macroalgae are very productive in the shallows, and phytoplankton, of trivial biomass, are relatively highly productive. Benthic microalgae may make up a large proportion of the biomass of microscopic plants. Light is of critical importance in controlling growth rates of submerged plants, but elevated nutrient levels allows marked increases in plant biomass. Mild nutrient enrichment may increase the growth of aquatics, but further eutrophication may lead to high macroalgae biomass and the loss of seagrasses. High levels of enrichment may lead to cyanobacterial blooms. The sediments play an important role in the transfer of nutrients from water column to plant biomass.