Use of photosynthetic pigments in sediments as a tracer for sources and fates of macrophyte organic matter

Abstract

Seaweed beds often cover slgnlflcant parts of intertidal and shallow subtidal soft bottoms Fleld and laboratory experiments have previously demonstrated that seaweed detritus can cause ropid populatlon and somatic growth of deposit-feedlnq invertebrates We assayed the photosvnthetlc plgments in sedlments of False Bay, Washington, US4 to identlfy means of detecting lateral transport of partlculate organlc matter (POM) from beds of green algae (Ulva and Enteroniorpha) Using a transect from open waters towards the head of the bay \\re tested the follo\uing hypotheses (1) net transport moves POhI throughout the whole bay towards sand flats In the ~n n e r palt of the bay (2) secttveed beds have onIy local spatial effects on the input of POM Only the second hypothesis proved consistent wlth the data Calculat~ons based on recovery of the plgment lutein lndlcate that the depos~tion of sea\*.ecd detritus is sufficient to stimulate deposit-feeder populatlon growth In all sediments both pr~llclpdl components dnalysis and srnlple correlation analys~s conslstenlly ~dentified 2 negatively corielated sets of photosynthetic plgments, which could be associated 1 ~1 t h diatoms and macrophytes respectively The multlvariate inverse relat~onship furthel stlengthens a c o n ~b l n a t ~o n of luteln and chlorophyll b as a marker for the source of macrophyte organic matter