Abstract
A computer model in FORTRAN for the growth of the giant kelp, Macrocystis, which inhabits the coastal waters of southern California, has been developed. The present model considers only physical factors, water temperature and submarine light, as the factors that control the growth of single fronds in large kelp beds.
The model has been used to examine two aspects of kelp growth in water of 20 meters depth. The opti mum time of the year for the start of new growth of fronds arising from the bottom in an established kelp bed was found to be early June. The optimum time of the year for regrowth of harvested canopy was found to be early July. In each case, the optimum time is interpreted as providing the shortest time for the frond to reach "maturity" (a length of 40 meters).
The penetration of sunlight into the hydrosphere is adversely affected by particulate matter in the water such as results from the introduction of sewage ef fluent. The simulation identifies the critical values for turbidity which will prevent new growth from occurring. At a depth of 20 meters, light absorbency of 18% per meter reduces the possible growing time by only 20%. But when absorbency is increased to only 24%, the growing time becomes zero. Simulation runs for other kelp-bed water depths revealed similar critical values of absorbency resulting in the restric tion of growth to shallower waters. This type of analysis to resource-management efforts is obvious.
The paper concludes with suggestions for modifying the integration techniques used and for incorporating additional quantifiable values to refine the model.
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