SEASONAL-VARIATIONS OF HIGHLY BRANCHED ISOPRENOID HYDROCARBONS AND PIGMENT BIOMARKERS IN INTERTIDAL SEDIMENTS OF THE TAMAR ESTUARY, UK

After preliminary experiments to ensure the reliability of the extract ion and sampling methods, the concentrations and distributions of high ly branched isoprenoid (HBI) alkenes, n-henicosahexaene (HE), caroteno ids and chlorophylls in surficial sediments of intertidal mudflats in the Tamar estuary, UK, were examined, at least monthly and often fortn ightly, during the period September 1993 to August 1994. The alkenes a nd the carotenoid fucoxanthin were present all year round, each exhibi ting a trimodal sinuosity and suggesting the same or similar sources, most likely diatoms. Non-coincidence of the HBI, HE and fucoxanthin ma xima, each offset from one another by 2-4 weeks, suggested that the HB I distributions offer a means of distinguishing the contribution of di atomaceous HBI producers, such as Haslea spp. from the total diatom po pulations. Reasons for the lack of reports of Haslea spp. in sediments from microscopy studies are discussed. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.