¹³C/¹²C ratios in marine food webs of the Torres Strait, Queensland

Abstract

During a research cruise in 1979 to the area between New Guinea and northern Australia, 250 samples were collected for measurement of ¹³C/¹²C (δ¹³C) to analyse carbon flow in tropical marine food webs. Plants at the base of food webs could be divided into two groups on the basis of their mean δ¹³C values: benthic seagrasses (-8.8‰), macroalgae (-12.5‰) and epiphytic algae (-13.3‰) were enriched in ¹³C (had less-negative δ¹³C values) when compared to planktonic samples (-21.8‰). Animals collected offshore were enriched in ¹³C by up to 9.1‰ relative to planktonic samples and seemed to show an increasing ¹³C enrichment with increasing trophic level. Relative to these offshore specimens, animals collected in intertidal seagrass meadows were usually enriched in ¹³C by 2-8‰, indicating that ¹³C-enriched benthic plants are important food sources in grassflats. Unusual ¹³C- enriched values of -3 to -7‰ among benthic chitons, gastropods and holothurians at one grassbed site suggest that unsampled benthic microalgae are also important sources of food-web carbon in the Torres Strait.