DAYTON: EXPERIMENTAL STUDIES OF ALGAL CANOPY 



TESTS: 

 —Along effect 

 - Lominorio spp effect 



-Ability of L; lonqipes to regrow 

 in disturbed area, particularly in 

 relation to ability of Laminoria spp 



Figure l.-Drawing of the kelp canopies at three different depths. Laminaria spp. refers to the large and very similar stipitate L. 

 groenlandica, L. dentigera, and L. yezoensia which seem to occupy broadly overlapping depth profiles but form identical canopies 

 because the stipe lengths and frond sizes are very similar. Diagrams of the experimental design testing hypotheses about the 

 competitive effects between canopies is included for the two manipulated areas. 



about the competitive effects these canopies have 

 on each other, the role of physical disturbance in 

 canopy composition, and a gradient of herbivore 

 pressures in deeper waters, where the sea otter 

 foraging becomes less efficient. 



METHODS 



This research was done in July 1971 and April 

 1972 in a small bay between the remains of the old 

 Constantino jetty and Kirilof Point on the Bering^ 

 Sea. A total of 34 dives were made during the 

 study. There were two study sites, a nearshore 

 shallow (< 5 m) area beside an old quarry and a 

 deeper (>7 m) reef about 150 m offshore. 

 Immediately offshore in the shallow area there is a 

 very heavy summer canopy of Alaria mixed with a 

 dense growth of annual brown algae such as 

 Cymathere triplicata (P. et R.) J. Ag., Desmares- 

 tia intermedia P. et R., and numerous species of 

 red algae representing such genera as Ptilota, 

 Hypophyllum, etc. Offshore from this dense algal 

 band, but still in the shallow area, are distinct 

 patches of Alaria with thick canopies floating on 



the surface and patches of a very solid secondary 

 Laminaria canopy. There are two Laminaria 

 growth forms in the more shallow (< 5 m) area: L. 

 groenlandica, L. dentigera, and L. yezoensis are 

 solitary plants with one heavy 50-150 cm stipe per 

 plant; L. longipes has thin multiple 20-40 cm stipes 

 from a single rhizomelike holdfast (Markham 1968, 

 1972). The third prostrate canopy is represented in 

 shallow water by scattered individuals of the 

 heavy brown alga Thalassiophyllum clathrus 

 (Gmelin) P. et R. The deeper offshore reef has a 

 scattered and relatively thin (0-20%) canopy of 

 Alaria and in the more shallow (7-12 m) levels a 

 very thick canopy cover of Laminaria spp. With 

 increasing depth the Alaria density decreases and 

 the Laminaria is gradually replaced by Agarum 

 cribrosum which forms the third prostrate canopy. 

 The experimental sites were chosen on the basis 

 of distinct patches of the respective canopies to be 

 manipulated and on the ease of shore access and 

 relocation. Pruning shears were used to clear areas 

 by cutting the stipes just above the holdfasts. In 

 every case an immediately adjacent area was 

 monitored as a control. 



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