Seaweed

Below is and article on the cultivation of seaweed.

Offered by Steve.

Cultivation: Introduction

Seaweed cultivation takes many forms but there is a kind of evolutionary process through which it develops, the rate of which is market-driven. If demand is low and natural resources adequate, cultivation is unnecessary. As demand increases, natural populations frequently become inadequate and attempts are made to increase production by resource management techniques such as improving harvesting techniques, removing competing species, adding artificial habitats and seeding cleared areas. Such techniques are most highly developed in Japan, China and south-east Asia.

Should such management prove to be inadequate, the use of artificial structures to grow seaweeds becomes inevitable. Fragments of adult plants, juvenile plants, sporelings or spores are seeded onto ropes or other substrata and the plants grown to maturity in the sea. To do this, intimate knowledge of both the biology and life history of the plants is critical. For example, kelps cannot be grown from fragments as there is a high level of specialization and fragments of sporophytes do not regenerate. On the other hand, many red algae do not have this degree of specialization and can easily be grown from portions of the adult plant. Knowledge of the life history is critical in many cases and on-land cultivation of particular life history phases is often necessary for seeding. A considerable amount of technology has gone into the development of reliable methods for the cultivation of seed-stocks and their improvement.

The penultimate development in seaweed cultivation is the growing of plants in artificial impoundments on land. This involves the use of either tanks or ponds into which seawater is pumped and the seaweeds are grown detached and at very high densities. This necessitates the careful study of the growth parameters of the seaweeds involved and the development of special strains, preferably with high growth rates, but more importantly, adapted to the artificial conditions. In some instances, the cultivation of seaweeds in association with animals has been attempted, which is often referred to as "polyculture". The ultimate development of seaweed cultivation will probably be the growth of genetically-improved strains in fermenter-like reactors, in which all environmental factors will be controlled and artificially-compounded seawater-like growth media used. It is likely that such strains will be developed by means of biotechnological techniques.

The world's most successful seaweed cultivation industries are in Asia, where low labour costs married to simple and intelligent maricultural techniques have proved very successful. The labour intensiveness of seaweed mariculture and the absence of a ready market have been the main reasons why seaweed mariculture has not developed to any great extent in the west. If seaweed-based cultivation is to develop in Europe and north America, we must look at the market potential of seaweeds and the various ways in which seaweed mariculture can be improved so as to reduce the labour content.

Large-scale seaweed mariculture is carried out only in Asia, where there is a very high demand for seaweed products and burgeoning populations to create market growth. Most cultivated seaweeds are grown for the food market, although the Eucheuma co-operatives in the Philippines and Gracilaria cultivation in association with milkfish production in Taiwan are exceptions to this rule, the seaweeds being used for carrageenan and crude agar production, respectively. Cultivation of seaweeds in Asia is a relatively low-technology business in that the whole, attached plants are placed in the sea and there is a high labour content in the operation. Several attempts have been made in various western countries to introduce high technology to the cultivation of detached plants grown in tanks on land in order to reduce labour content but none of these has attained commercial viability to date.