Meeting Abstract

63.3  Sunday, Jan. 6  Rising sea level and changes in intertidal zonation: Professor Snadrock 60 years later. PEARSE, J.S.; PEARSE, D.E.; PEARSE, V.B.*; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz; Univ. of California, Santa Cruz pearse@biology.ucsc.edu

Global warming has led to sea level rise in many parts of the world over the past century. Since the 1940s, sea level has risen about 15 cm in central California. In July 1947, three students surveyed the abundance and position of six taxa of invertebrates (limpets: Lottia austrodigitalis/digitalis, Lottia scabra, snails: Littorina keenae, Littorina plena/scutulata, barnacles: Chthamalus dalli/fissus, Balanus glandula) along four vertical transects differing in wave exposure in the high rocky intertidal zone at Stanford University�s Hopkins Marine Station in Pacific Grove. We resurveyed those transects in July 2007. The same pattern was seen in both 1947 and 2007 with respect to wave exposure: for all six taxa, the median height of their distribution was higher along the more exposed transects. On the other hand, differences in the results of the two studies demonstrated a striking shift in the vertical distribution of all the animals. Median height along the transects was higher for all six taxa in 2007, in some cases much higher, and the increase in median height was greatest at the more wave-exposed transects. In addition, incidental taxa characteristic of tidal zones lying mostly below the transects (mussels, owl limpets, chitons) are now more abundant within the lower portions of the more wave-exposed transects. In all the transects, the abundance of the six taxa was lower in 2007 than in 1947, in some cases, much lower, but these differences in abundance may reflect interannual variation rather than long-term trends. In contrast, the increase in the median height of the distribution of species almost certainly is a response to rising sea level.