A Study of the Solitary Sea Anemone Anthopleura sola as an Indicator of Global Warming in the Northern California Rocky Intertidal

This site describes on-going results and data from a research project that is tracking both intertidal temperature and abundance of A. sola over a five-year period (2004-2009) in order to study the effect of global warming on the intertidal.

It is important to study organisms in intertidal habitats, because these organisms can act as early warning indicators of long-term ecological change that may occur as a result of global warming or other human activity disruptive to intertidal communities. Studies show that populations of many intertidal species are migrating northward due to global warming [1],[2]. These migrations are important to document because they can serve as indicators of wider ecological changes occurring as a result of climate change. Because solitary sea anemones such as Anthopleura sola are very long-lived, individuals can be identified and tracked over extended periods. It may thus be possible to understand changes in both macro- and microhabitats in the intertidal by observation of A. sola.

A. sola is a southern species currently found between Punta Banda, Baja California and Bodega Bay in Northern California [3]. Long considered an individual of Anthopleura elegantissima, Anthopleura sola has only recently been identified as a separate species [3],[4]. As a result, there is little data available on this anemone. It is thus important to create baseline inventories of this species at different points along the coast. The baseline can then be used in future comparisons to test the hypothesis that the species is migrating northward due to climate change.

In the first phase of the study, a baseline survey has been performed at three coastal sites in Northern California: Duxbury Reef, the Fitzgerald Marine Reserve, and Davenport Landing. The baseline shows that, as expected, the abundance of A. sola drops significantly at the more northern sites. At both Davenport Landing and the Fitzgerald Marine Reserve, the abundance of A. sola appears to be exponentially distributed, with higher density patches occurring less frequently. In both cases, results indicate that the abundance of A. sola increases closer to the low intertidal zone. The sizes of A. sola appear to be normally distributed, with larger individuals found at the more northern site, Fitzgerald Marine Reserve, where there is less competition.

Temperature data are currently being collected to establish correlations between population and climate change. At the three study sites, the measured intertidal temperatures do not necessarily follow ocean and air temperature trends: In fact, the measured intertidal temperatures have an opposite trend to the ocean and air temperatures obtained from nearby bouys. It is thus premature to attribute changes in intertidal ecology to changes in ocean or atmospheric temperatures, and more research is required to understand the effect of global warming on intertidal organisms.

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References

1. Barry J.P., Baxter C.H., Sagrin R.D., & Gilman S.E. (1995). Climate-related long-term faunal changes in a California rocky intertidal community, Science 267 (5198): 672-675.
2. Sagarin R.D., Barry J.P., Gilman S.E., & Baxter C.H. (1999). Climate-related changes in an intertidal community over short and long time scales. Ecological Monographs 64 (4): 465-490.
3. Pearse V. & Francis L. (2000). Anthopleura sola, a new species, solitary sibling species to the aggregating anemone, A. elegantissima (Cnidaria: Anthozoa: Actiniaria: Actiniidae). Proceedings of the Biological Society of Washington 113 (3): 596-608.
4. McFadden C.S., Grosberg R.K., Cameron B.B., Karlton D.P., & Secord D. (1997), Genetic relationships within and between clonal and solitary forms of the sea anemone Anthopleura elegantissima revisited: Evidence for the existence of two species. Marine Biology 128 (1): 127-139.