Monitoring intertidal community change in a warming world

Abstract

If the earth’s climate is warming as predicted, the effects of this environmental change may begin to appear along a range of biological scales, including ecosystems, communities, populations and individual species. The intertidal rocky shore is a useful system for monitoring changes due to its accessibility, readily sampled organisms and well-documented ecology. Using the rocky intertidal as a model system, historical work and a modem day survey were used to detect changes in the abundance and distribution of invertebrate and algal species around the Irish coastline. Firstly, the major contributions to Irish rocky shore community ecology in the literature throughout the past 50 years were identified and assessed. One of these historical studies was then used as a baseline with which a modem day survey could be compared. Throughout the summer of 2003, a re-survey was carried out using the same semi-quantitative (i.e. abundance scales) methodologies as the historical survey. Results showed that after a 50-year time interval, 12 intertidal species out of the 27 re-surveyed changed significantly in abundance. These changes are discussed within the context of the species effects of climate change on the Irish coast. The methodologies used throughout the historical survey and the modem day resurvey were critically assessed with particular reference to the results obtained by different operators and the sensitivity of the methods to detecting change. During the re-survey, quantitative data were collected for two trochid species Osilinus lineatus and Gibbula umbilicalis. A detailed description and analysis of their population structure (i. e. size and age) and density around the Irish coastline was conducted. In particular, the population characteristics of shores at the ‘edge’ and ‘centre’ of both species distributions in Ireland were examined. The 2003 resurvey and the in-depth look at the populations of two trochid species may be used throughout future monitoring at the community and population level.