1916 Muenscherj on Shaxv Island Algae 201 



The five algal associations as they have been worked out on San Juan 

 Island are also easil}^ distinguished on Shaw Island. The structure of 

 the associations may differ somewhat in some places; certain species may 

 be more or less abundant, or sometimes some species drop out entireW, or 

 different species may come in. However the zones are so similar to those 

 described (loc. cit.) for San Juan Island that only a list of the six most 

 common algae in each association will be given here: 



1. Endocladia association 



1. Endocladia muricata 4. Enteromorpha linza 



2. Porphyra perforata 5. Enteromorpha intestinalis 



3. Gloiopeltis furcata 6. Ecbellocystis sp. 



2. Fucus association 



1. Fucus evanescens 4. Cladophora arcta 



2. Gigartina mamillosa 5. Microcladia borealis 



3. Gloiopeltis furcata 6. Rhodomela larix 



3. Ulva association 



1. Ulva lactuca 4. Hormiscia tetraciliata 



2. Iridaea laminarioides 5. Polysiplionia californica 



3. Enteromorpha linza 6. Corallina officinalis 



4. Laminariaceae association 



1. Xereocystis luetkeana 4. Costaria costata 



2. Laminaria bullata 5. Alaria tenuifolia 



3. Laminaria saccliarina 6. Agarum fimbriatum 



5. Zostera association 



1. Porpliyra naiadum 4. Ag'ardhiella tenera 



2. Ulva lactuca 5. Laminaria saccharina 



3. Enteromorpha linza 6. Iridaea laminarioides 



While it is true that the above associations form rather distinct ver- 

 tical zones in many places, this does not necessarily mean that they form 

 distinct layers all around the island. On the contrary, these associations 

 may be so modified in certain places that they are hardly distinguishable. 

 The character of the shore line, and the presence of strong currents and 

 exposure to sun, wind and waves, are responsible for many of the differ- 

 ences in algal A'egetation in areas of relative vertical positions. 



Where the shore is rock and the current is swift Lamimiria bullata, 

 Alaria tenuifolia, ^Igarum fmhriatum and Desmarcstia ligulata herhacea 

 abound in large numbers just below the low-tide mark, while farther out 

 on the submerged rocks Nereocystis luetkeana is found. Rigg' charts beds 

 of Nereocystis on the south and northwest ends of Shaw Island. Xei-eocys- 

 tis beds on this island are mostly verj'^ narrow and close to the shore due 

 to the abruptness of the shore in most places. The water soon becomes 

 too deep for Nereocystis even near the shore, sometimes reaching a depth 

 of 10 to 60 meters less than 100 meters from the shore^. The largest 



2Rigg-, Geo. B. Ecological and Economic Notes on Puget Sound Kelps: U. 

 S. Senate Document No. 190. Washington, D. C. 1912. 



sCoast and Geodetic Survey: Washington Sound. Washington, D. C. Jan., 

 1912. 



