Diurnal and seasonal variation in physico-chemical conditions within intertidal rock pools

Abstract

A study of the diurnal and seasonal variation in the physico-chemical conditions within intertidal rock pools on the West coast of Scotland was undertaken to provide data on the environmental conditions experienced by animals inhabiting these pools. The temperature, pH, partial pressure of oxygen ( P O 2) and salinity were measured every hour for 24 h and the total alkalinity, partial pressure of carbon dioxide ( P CO 2) and carbon dioxide content ( C CO 2) calculated. This sampling regime was carried out once a month for 12 months to determine the extent of seasonal variation in conditions within temperate pools. Large diurnal variations were recorded in nearly all the physico-chemical parameters measured. The greatest variation was recorded in the temperature and P O 2 of the water but significant changes in pH and P CO 2 were also recorded. Total alkalinity varied little during any 24 h period but carbonate alkalinity, which was always lower than total alkalinity, showed slightly greater variation. There was also considerable variation in the magnitude of these diurnal changes between pools at different heights on the shore. Diurnal variation in the physico-chemical conditions within the pools were observed throughout the year although the magnitude of these changes varied seasonally. Detailed studies on individual pools demonstrated that appreciable local variation existed in the physico-chemical conditions within each pool.