DIET OF THE INTERTIDAL CALLIANASSID SHRIMPS BIFFARIUS-ARENOSUS AND TRYPEA-AUSTRALIENSIS (DECAPODA, THALASSINIDEA) IN WESTERN PORT (SOUTHERNAUSTRALIA), DETERMINED WITH MULTIPLE STABLE-ISOTOPE ANALYSES

Biffarius arenosus had a mean delta(13)C of -15.4 +/- 0.2 parts per th ousand and a mean delta(15)N of 5.9 +/- 0.1 parts per thousand (n = 38 ), and Trypea australiensis had a mean delta(13)C of -16.3 +/- 0.3 par ts per thousand and a mean delta(15)N of 7.6 +/- 0.1 parts per thousan d (n = 20). The delta(13)C signatures of the only mangrove species pre sent (Avicennia marina) and the most abundant saltmarsh plant (Sarcoco rnia quinqueflola) indicated that they were not major food sources. Se agrasses, predominantly Heterozostera tasmanica, had mean delta(13)C a nd delta(15)N values of -11.7 +/- 0.2 parts per thousand (n = 65) and 3.9 +/- 0.2 parts per thousand (n = 62), respectively. Seagrass epiphy tes had mean delta(13)C and delta(15)N values of -17.9 +/- 0.4 parts p er thousand and 4.6 +/- 0.3 parts per thousand (n = 27), respectively. A mixture of seagrasses and their epiphytes was the most likely sourc e of organic carbon for B. arenosus. Benthic microalgae, such as diato ms, were a possible food source, but phospholipid biomarkers indicated a meagre abundance of diatoms in the sediments, and microscopy of shr imp guts revealed few or no diatom frustules. For T. australiensis, fo od sources were less easily distinguished than for B. arenosus, but th ey could include seagrass epiphytes plus the green macroalgae Enteromo rpha spp, and/or the brown alga Chordaria cladisiphon.