Nutrient enrichment and marine algae: the effects of pinniped excreta on the marine benthic algae of A{tilde}no Nuevo Point, California

The present study- concerned the quantitative and qualitative comparison of two intertidal benthic algal floras. Data were collected from the experimental area, Ano Nuevo Point, and Pigeon Point the control area, both in San Mateo County California (Figure 1). Ano Nuevo Point is located 6^4- km south of San Francisco, California and .5 km north-east of Ano Nuevo Island. The substrate of the intertidal sampling areas was composed of Miocene cherty shale slabs, Intermixed with mudstone (Brabb, 1970). At a -1.2 ft tide, 250 m of intertidal area were exposed as measured from + 3.4 ft (in relation to mean lower low water, 0.0 ft). The point is partially protected from direct surf action by Ano Nuevo Island. The control site for the study was located approximately 300 m south of the lighthouse at Pigeon Point and 6.5 km north of Ano Nuevo Point. The substrate was composed of Cretaceous siltstone and conglomerate (Touring, 1959)° The composition of this substrate is quite similar to that at Ano Nuevo Point, but differs considerably in age. At a -1.2 ft tide, A-7 m of intertidal area were exposed, as measured from +3.9 ft. The study area was protected from direct wave shock by a 30 a by 15 m rock outcropping on the northern boundary of the sampling area and by Pigeon Point itself. The lack of pinniped hauling-out grounds in the vicinity of Pigeon Point was the only substantial difference between the environments of the experimental and control study sites.