GIS‐based gap analysis of an existing marine reserve network around Santa Catalina island

Abstract

This study utilized a geographic information system (GIS) to evaluate an existing network of marine reserves around an island off the southern California coast. The investigation focused on the effectiveness of the reserve network relative to the regional ecology, the disturbance regime, and meta‐population biology of giant kelp (Macrocystis pyrifera), perhaps the most important single taxon in this nearshore marine ecosystem. Macrocystis serves as both structural habitat and food for a wide range of marine invertebrates and fishes. Santa Catalina Island's highly dissected, 87‐km leeward and windward coastline offers a wide range of microhabitats with respect to storm exposure, temperature, the nearshore light regime, and other factors. GIS data layers used to address these issues included a digital terrain model, digital bathymetric model, submarine slope, submarine aspect, bottom relief, significant wave height, and kelp distribution maps from several survey years. GIS overlay methods applied to the multitemporal kelp distribution maps generated a model representing the spatial persistence of kelp. Correlations between the observed distributions, kelp persistence, the disturbance regime, and the physical variables that permit kelp to resist or recover from it were drawn. Definite geographic patterns were observed relative to several of these variables. The results in this study are discussed in light of previous research using GIS data layers of sea surface temperature (SST) and a series of solar insolation models. This gap analysis identified large regions of persistent kelp, under disturbance regimes markedly different from those in the existing reserves, that were relatively unprotected. This suggests that the designation of additional reserves may be necessary in these currently unprotected areas.