Field Ecology of the Brown Alga Phaeostrophion irregulare Setchell et Gardner

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Abstract
The distribution, seasonal growth and reproduction of in situ populations of P. irregulare were studied at Glacier Point, British Columbia [Canada] in relation to a variety of environmental factors. The plant is restricted to sandy areas where large fluctations of sand occur annually. Typically P. irregulare is buried 6-4 mo./yr and its growth and reproduction are limited to periods of sand subsidence. Competition with other plants probably accounts for the restriction of P. irregulare to sandy areas, as it will grow in rocky areas if other algae are eliminated. The period of maximum growth (Feb.-April) is associated with a corresponding increase in light intensity and water temperature. After April, growth in nontide pool populations decreases much more rapidly than growth of tide pool populations, because of increased desiccation during daylight hours. The morphology of laminate plants of Phaeostrophion irregulare is extremely variable and the range of variability at Glacier Point overlaps with that described for P. australe from California [USA]. The latter plant is considered to be a growth form and a taxonomic synonym of P. irregulare. Distributional evidence also supports this conclusion, as there is no marked geographical discontinuity between the 2 plants. P. irregulare exhibits a sporadic open-coastal distribution from Point Conception, California to Khantaak Island, Near Yakutat, Alaska [USA]. Temperature is probably the primary factor controlling its geographical distribution, with salinity being regionally significant. Local conditions (i.e., the presence or absence of sand) are of major significance in determining the regional distribution of the plant.