| A major challenge facing ecology is to better understand how large-scale processes modify local scale processes to shape the assembly and organization of ecological communities. Previous work indicates that on New England rocky intertidal shores, consumers strongly control recovery from disturbance on sheltered shores, and high recruitment and competition for space dictate recovery on wave-exposed shores. However, experimental results indicate that exposure driven consumer control is not ubiquitous throughout the Gulf of Maine, and communities in the northern Gulf exhibit limited recruitment of sessile invertebrates with extended planktonic larval stages and rapid settlement and growth of macroalgae. Based upon prevailing oceanographic circulation patterns, including the flow of the Eastern and Western Maine Coastal Currents, and observed community dynamics, the coastal systems in the Gulf of Maine were divided into Northern, Penobscot, and Southern oceanographic regions.;Subsequent studies investigated changes in the role of the habitat-modifying alga, Ascophyllum nodosum and revealed that an intact canopy impeded Fucus vesiculosus recovery in the northern Gulf but had a neutral impact in the southern Gulf, because the longer canopies in the north restrict light penetration. In the north, naturally occurring densities of the primary herbivore on Gulf of Maine rocky shores, Littorina littorea are below the threshold needed to impact Fucus recovery. Recruitment limitation and possibly the harvesting of L. littorea , restrict densities in this region. These results indicate the need for a better understanding of the impacts of Ascophyllum and Littorina littorea harvesting in the northern Gulf of Maine.;Detailed analyses of bottom-up processes and ecological subsidies indicated that recruitment of barnacles, Semibalanus balanoides, is delayed in the north Gulf resulting in a temporal mismatch between larval settlement and nearshore phytoplankton concentrations. Lower resource availability in the northern Gulf may slow the growth of the small number S. balanoides that do successfully recruit in this region. However, the availability of inorganic nutrients in nearshore waters does not explain the algal dominance that occurs in the northern region. This work highlights the importance of linking oceanographic processes with ecological subsidies to onshore communities. |
