Food Web Structure and Basal Resource Utilization along a Tropical Island Stream Continuum, Puerto Rico

March, JG, and CM Pringle. 2003. Food web structure and basal resource utilization along a tropical island stream continuum, puerto rico. Biotropica 35 (1) (MAR): 84-93.

Tropicals treamf ood webs are thought to be based primarilyo n terrestriarl esources( leaf litter) in small forested headwatesrt reamsa nd algalr esourceisn largerw, iders treamsI. n tropicali slands treamst, he dominantc onsumeras re often omnivorousfr eshwatesrh rimpst hat consumea lgae,l eaf litter,i nsects,a nd others hrimpsW. e useds tablei sotope analysist o examine( 1) the relativei mportanceo f terrestriaal nd algal-basedfo od resourcest o shrimpsa nd other consumersa nd determine( 2) if the relativeim portanceo f thesef ood resourcecs hangeda longt he streamc ontinuum. We examined8 15N and 813Cs ignatureos f leaves,a lgae,m acrophytesb, iofilm,i nsects,s nails,f ishes,a nd shrimpsa t threes ites (300, 90, and 10 m elev.)a longt he Rio EspirituS anto,w hichd rainst he CaribbeanN ationalF orestP, uerto Rico. Isotopes ignatureos f basalr esourcews ered istincta t all sites.R esultso f two-source6 13Cm ixingm odelss uggest that shrimpsr eliedm oreo n algal-basedca rbonr esourcetsh an terrestrialldye rivedr esourceas t all threes itesa longt he continuum.T his studys upportso therr ecentf indingsi n tropicals treamsd, emonstratintgh ata lgal-basedre sourceas re very importantt o streamc onsumers,e ven in small forestedh eadwaters treams.T his study also demonstratetsh e importanceo f doing assimilation-baseadn alysis( i.e., stablei sotope or trophicb asis of production)w hen studying food webs.