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Environmental change, interspecific interactions, and shifting algal distributions on rocky shores
Author(s) -
Harley C. D. G.
Publication year - 2003
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.0022-3646.2003.03906001_63.x
Subject(s) - intertidal zone , rocky shore , interspecific competition , abiotic component , ecology , range (aeronautics) , climate change , biology , environmental change , shore , intertidal ecology , spatial ecology , fishery , materials science , composite material
Because intertidal organisms live close to their environmental tolerances, intertidal species are considered early harbingers of the effects of global change. Using a combination of spatial environmental gradients and long‐term datasets, I examine the likely consequences of global warming on the distribution of Mazzaella parksii (formerly Mazzaella cornucopiae ), a turf‐forming red alga. On Tatoosh Island, WA, M. parksii is restricted almost entirely to north‐facing surfaces. On south‐facing slopes, the upper limit of M. parksii , which is set by abiotic stress, occurs much lower on the shore. However, its lower limit, which is set by herbivores, does not vary with aspect. Because its upper and lower limits are independent across the aspect gradient, M. parksii is effectively “squeezed out” of the system as one moves from a north‐facing to a south‐facing slope. This general pattern is observed at several spatial scales across gradients of wave exposure and air temperature. The vertical distributional patterns of M. parksii also shift across temporal gradients. Over the past 25 years, the upper limit of M. parksii on Tatoosh Island has shifted downshore by approximately 25 cm. Most of this change was driven by three consecutive harsh summers in the mid 1990's. These temporal patterns, combined with the insight gained from spatial patterns, suggest that M. parksii may go locally extinct in many parts of its range as its upper and lower limits converge. Furthermore, because vertical distributional shifts are linked to stochastic climatic effects, temporal change in marine algal populations may be rapid and unexpected.