Particulate organic matter dynamics in tropical headwater streams: A comparison of biotic and abiotic factors

TitleParticulate organic matter dynamics in tropical headwater streams: A comparison of biotic and abiotic factors
Publication TypeJournal Article
Year of Publication2002
AuthorsCrowl, AT, Covich, A, Scantena, FN, Phillips, R, Townsend, AR, Vinson, DK
JournalVerhandlungen der Internationale Vereinigung fur Theorestische und Angewandte Limnologie
Accession NumberLUQ.122
Keywordstropical streams

Particulate organic matter often constitutes a large proportion of the energy fueling stream food webs (Wallace et al. 1982, Western & Meyer 1997). As a consequence, stream ecologists have expended considerable effort in understanding the linkages between organic matter inputs, storage and transport. Detrital dynamics are strongly related to discharge (Cuffney & Wallace 1989, Webster & Meyer 1997, Larned 200) and more loosely associated with biotic assemblages. During periods of high discharge, detrital processing is often highly controlled by physical processes, showing little correlation with the biota (Webster et al. 1994, Radcliffe et al. 1995). However, during periods of prolonged base flow conditions, detritus is often regulated by macro-shredders and consumers (Crowl et al. 2001). Tropical mountain streams are often characterized by steep gradients and highly variable rainfall, which results in torrential flows. These conditions typically lead to low retention of organic matter, high transport and minimal biotic processing. However, few studies have compared to detrital storage, processing and transport across streams of various discharge regimes and biotic community assemblages to determine the relative strengths of physical and biotic processing (Spain 1984, Parson et al. 1989, Smock 1990, Jones & Smock 1991, Richardson 1992). In this study, detrital storage, transport and size fractionation in four first-order, headwater streams that compromise part of the long-term ecological research at the Luquillo Experimental Forest, Puerto Rico are described. These streams are located across the forest landscape, resulting in differing elevations, gradients and discharge regimes while having very similar riparian input rates and composition. Moreover, each of these streams has a different macro-benthic community resulting in a range of physical and biotic gradients. These streams have been sampled bioannually (during the dry and wet seasons) since 1998. In this paper, hydrologic and biotic features of each sampling site are linked with the amount of detrital material stored, transported and processed. Biotic interaction represent important drivers to the detrital web, even during periods of high and variable flows. During prolonged periods of base flow conditions, the biota represent the main indicator of detrital dynamics.