GELIDIUM CULTIVATION IN THE SEA

Gelidium fronds were grown in the sea under a variety of experimental conditions: on rigid, damped and tensioned test farms of various designs, in calmer and more turbulent habitats, at various depths, with and without commercial fertilizer supply. Initially, the effectiveness of a given cultivation strategy was based on the survival and growth of the fronds, here termed 'bio-assay' mariculture. Ambient seawater temperature, nutrient availability, hydrodynamics and other environmental parameters were measured periodically. In-the-sea irrigation of test plants with commercial fertilizers was apparently effective, at least with some farm designs, and when ambient nutrient levels were low. Under optimal conditions, achieved through experimental manipulation of farm design, specific growth rates of over 2% per day were recorded. However, considerable variation in growth rates and in plant performances was observed. It was not always possible to correlate these variations with design modifications or other experimental parameters. In view of these findings, we have reviewed our initial 'bio-assay' approach, namely the assumptions about the design and operation of farm structures and their interactions with the water and the fronds. Methods were developed to quantify these interactions. We advocate a quantitative, 'hydrodynamic' approach in developing an effective cultivation strategy for gelidioid algae and are optimistic about progressing from test-to-commercial scale farms in the near future.