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.

Damming Tropical Island Streams: Problems, Solutions, and Alternatives.

MARCH,JAMES G.; BENSTEAD, JONATHAN P.; PRINGLE, CATHERINE M.; SCATENA, FREDERICK N. 2003. Damming Tropical Island Streams: Problems, Solutions, and Alternatives.. November 2003 / Vol. 53 No. 11 • BioScience.

The combination of human population growth, increased water usage, and limited groundwater resources often leads to extensive damming of rivers and streams on tropical islands. Ecological effects of dams on tropical islands can be dramatic, because the vast majority of native stream faunas (fishes, shrimps, and snails) migrate between freshwater and saltwater during their lives. Dams and associated water withdrawals have been shown to extirpate native faunas from upstream reaches and increase mortality of downstream-drifting larvae. A better understanding of the effects of dams and the behavior of tropical island stream faunas is providing insights into how managers can mitigate the negative effects of existing dams and develop alternatives to dam construction while still providing freshwater for human use.We review the ecological effects of dams on tropical island streams, explore means to mitigate some of these effects, describe alternatives to dam construction, and recommend research priorities.
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