Growth and production of the green alga Cladophora montagneana in a eutrophic australian estuary and its interpretation using a computer program

Abstract

The shallow, eutrophic Peel-Harvey estuary developed massive populations of a green alga, Cladophora montagneana, forming extensive free-living mats on the floor of this estuary. Growth rates of confined populations were measured in the field for 2 successive years. Experimentally-derived relationships describing growth and photosynthesis as a function of light, temperature and inorganic nutrients were used to develop a computer program to interpret the performance of this alga in the field. Growth was strongly seasonal, with a maximum in summer (up to 1.3% d-1), and ceased in winter. Net production in the mat was low, up to 3.4 g (dry wt) m-2d-1, with only the surface layer photosynthetically active because of self-shading. Similar seasonal trends, but faster growth rates (maximum 2.7% d-1) were obtained with algae transferred to shallower waters in Peel Inlet, where light intensity was greater. Cladophora transferred from Peel Inlet to Harvey Estuary grew little or not at all, consistent with its absence in this part of the estuary. Computer simulations of growth using real environmental data emphasise the importance of light, and self-shading in particular, in controlling productivity. Show more