THE EFFECT OF WATER MOTION ON ALGAL SPORE ADHESION1,2

Abstract

The effects of water motion on the attachment of algal germ cells to benthic substrates were studied. Water motion was measured in the field and the forces on a germ cell attached to a substrate surface computed. Laboratory apparatus for simulating wave surge was developed, calibrated, and used for experiments on the spore attachment process. A“waterbroom,” producing water motion over the surface of a submerged substrate in a laboratory aquarium, closely simulates wave surge; it was calibrated by measuring static and dynamic pressures in the substrate’s boundary layer and determining whether the layer was laminar or turbulent.Preliminary tests with the waterbroom indicate that the adhesion of carpospores of Agardhiella tenera to a clean glass surface increases wih residence time, while that of Cryptopleura violacea decreases. Improved experimental data on Gracilariopsis sjoestedtii showed an increase in adhesiveness with residence time, from 10 hr to an asymptotic limit at 20. Once attached, the Gracilariopsis spores adhere firmly, resisting removal by shear forces nearly 100 times their weight.