Distribution, structure, and function of marine ecological communities in the northern California Current upwelling ecosystem

Within systems characterized by substantial spatial and temporal variability, abundances of organisms tend to be higher in localized areas. Within the northern California Current system, the identification of such marine, biological hotspots would be of great importance to resource managers, conservationists, and research planners, and is consequently a growing area of research. Furthermore, in order to understand howecosystems function and persist, it is necessary to know how ecological communities are distributed. The overall goal of this study is to provide further understanding regarding the functioning of marine ecosystems in such highly variable environments and to provide information about the distribution and structure of marine communities. Sampling was conducted during June and August of 2000 and 2002 as part of the U.S. GLOBEC mesoscale surveys from Newport, Oregon in the north to Crescent City, California in the south. A geostatistical approach was used to create surfaces used in a GIS to determine the distribution of various community characteristics. Two biological hotspots were identified and determined to persist in space and time, yet differed with respect to biological and physical features and in the amount of area covered. Various community analyses, including nonmetric multidimensional scaling, indicator speciesanalysis, and cluster analysis were used to determine various community propertiesassociated with the hotspots and non-hotspot regions. Results indicate that nektonbiological hotspots in the northern California Current persist across differingenvironmental and biological conditions, although upwelling-based hotspots may be more susceptible to climatic conditions than retention-based hotspots. Analyses of thedistribution of the functional groups within the region indicate that the predominantbiological activity is spatially nonrandom and occurs within persistent, localized areas. Analyses of species associations suggest a moderate degree of redundancy. The presence of such complementary species within functional groups may confer the stabilityobserved within these systems. The finding that large regional areas are composed ofsmaller, localized hotspots where a predominant amount of biological activity isoccurring, suggests that the evaluation of large marine ecosystems may lead to erroneousor misleading results if they do not consider the more persistent, localized biologicalhotspots.

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