Lipids as indicators of the origin of organic matter in fine marine particulate matter

The lipid compositions of fine particulate matter (<35 �m diameter) have been analysed from two temperate sites (Western Port Bay, WPB, and Corner Inlet, CI, Victoria) and two tropical sites (Bowling Green Bay, BGB, and Lizard Island Lagoon, LIL, North Queensland) in the Australian coastal zone. Identification of lipid biomarker molecules (especially fatty acids, fatty alcohols and sterols) has, in conjunction with microscopy, enabled identification and, in some instances, quantification of a range of biological inputs. Estimated contributions of biomass to total particulate mass in the temperate samples were: seagrass detritus (~10-15%) > bacteria (~34%) > live diatoms (≤ 1%). Similar estimations for the tropical samples were: BGB, bacteria (- 1%) > live diatoms (< 1%); and LIL, bacteria (~20-30%) > copepod detritus (≥ 1%) > live diatoms (< 1 %). Biomarkers also indicated the presence of coral mucus and a distinctive bacterial chemotype, possessing branched chain alcohols, in the LIL sample.