COS 23-4
Oceanographic and ecological drivers of community structure in a rocky intertidal meta-ecosystem

Tuesday, August 12, 2014: 9:00 AM
311/312, Sacramento Convention Center
Bruce A. Menge, Integrative Biology, Oregon State University, Corvallis, OR
Tarik C. Gouhier, Marine Science Center, Northeastern University, Nahant, MA
Sally D. Hacker, Integrative Biology, Oregon State University, Corvallis, OR
Francis Chan, Integrative Biology, Oregon State University, Corvallis, OR
Karina J. Nielsen, Department of Biology, Sonoma State University, Rohnert Park, CA

Multi-scale meta-ecosystem theory recognizes that systems are interconnected by “ecological subsidies.” This theory suggests that contrary to approaches focusing primarily on local-scale dynamics for understanding of local community structure (LCS), cross-scale feedbacks between local and regional processes can be crucially important for understanding LCS. We evaluate these two perspectives using a hierarchical meta-ecosystem model. The model predicts responses of LCS to inputs over macro- (100s km), meso- (10s km) and local- (0.1s km) oceanographic scales.  The model assumes that local communities occur in distinct regions and that connectivity effects are strongest among local sites.  Predictions are: if macro-scale processes dominate, then regardless of regional differences, (1) local communities will be similar, and (2) even more so with increased connectivity. When mesoscale processes dominate, (3) LCS will be similar within but distinct between regions, and (4) similar both within and among regions with increased connectivity. When local-scale processes dominate, (5) LCS will differ both within and among regions, and (6) be similar within but not between regions with increased connectivity.  We tested the model by quantifying LCS at 13 sites spanning 725 km of the northern California Current System, and relating it to cross-scale patterns of ecological subsidies and environmental conditions.


Our results indicate that LCS variability is dependent on oceanographic variation. Oceanographic conditions, ecological subsidies, and region (cape) had strong effects across scales, explaining a total of 54% of the variance in LCS, while variation attributable to local scales explained only 7.2% of the variance.  Differences in continental shelf width at a scale of ~80km was an important factor underlying oceanographic variation.  At the regional/cape scale, sessile invertebrate and predator dominance were associated with weaker upwelling, higher phytoplankton abundance and higher recruitment of sessile invertebrates, while macrophyte dominance was associated with stronger upwelling, lower phytoplankton abundance and lower recruitment. Overall, our results support the theory that meta-ecosystems are organized hierarchically, with variation in environmental processes (currents, temperature) and ecological subsidies (nutrients, larval inputs) at mesoscales having the greatest effect on community structure, and local-scale ecological processes (interactions, disturbance) having a smaller impact on local community structure.  LCS varies within capes, but sites within capes generally cluster more closely with one another than with sites within other capes. Our results suggest that the greatest understanding of variability in LCS is likely to be illuminated using a meta-ecosystem theoretical framework.