Journal of the Marine Biological Association of the United Kingdom

Research Article

Using historical data to detect temporal changes in the abundances of intertidal species on Irish shores

Christina  Simkanin a1a2p1c1, Anne Marie  Power a3, Alan  Myers a1, David  McGrath a2, Alan  Southward a4, Nova  Mieszkowska a4, Rebecca  Leaper a5 and Ruth  O'Riordan a1
a1 Department of Zoology, Ecology and Plant Science, National University of Ireland—Cork, Lee Maltings, Prospect Row, Cork City, Ireland
a2 Department of Life Sciences, Galway—Mayo Institute of Technology, Dublin Road, Galway, Ireland
a3 Room 226, Martin Ryan Institute, National University of Ireland—Galway, Ireland
a4 Marine Biological Association of the United Kingdom, Citadel Hill, Plymouth, PL1 2BP, UK
a5 Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia

Article author query
simkanin c   [PubMed][Google Scholar] 
power am   [PubMed][Google Scholar] 
myers a   [PubMed][Google Scholar] 
mcgrath d   [PubMed][Google Scholar] 
southward a   [PubMed][Google Scholar] 
mieszkowska n   [PubMed][Google Scholar] 
leaper r   [PubMed][Google Scholar] 
oriordan r   [PubMed][Google Scholar] 


An historical data set, collected in 1958 by Southward and Crisp, was used as a baseline for detecting change in the abundances of species in the rocky intertidal of Ireland. In 2003, the abundances of each of 27 species was assessed using the same methodologies (ACFOR [which stands for the categories: abundant, common, frequent, occasional and rare] abundance scales) at 63 shores examined in the historical study. Comparison of the ACFOR data over a 45-year period, between the historical survey and re-survey, showed statistically significant changes in the abundances of 12 of the 27 species examined. Two species (one classed as northern and one introduced) increased significantly in abundance while ten species (five classed as northern, one classed as southern and four broadly distributed) decreased in abundance. The possible reasons for the changes in species abundances were assessed not only in the context of anthropogenic effects, such as climate change and commercial exploitation, but also of operator error. The error or differences recorded among operators (i.e. research scientists) when assessing species abundance using ACFOR categories was quantified on four shores. Significant change detected in three of the 12 species fell within the margin of operator error. This effect of operator may have also contributed to the results of no change in the other 15 species between the two census periods. It was not possible to determine the effect of operator on our results, which can increase the occurrence of a false positive (Type 1) or of a false negative (Type 2) outcome.

(Received February 4 2005)
(Accepted September 12 2005)

c1 e-mail:
p1 Environmental Sciences and Resources, Portland State University, Portland, Oregon 97207-0751, USA