Fluvial and epilithic organic matter dynamics in headwater streams of southwestern British Columbia, Canada

To characterize organic matter dynamics in headwater streams of southwester n British Columbia, Canada, we monitored epilithic biomass and fluvial tran sport of organic matter. Fluvial organic matter was collected once to twice monthly from 7 streams: samples were processed as coarse particulate organ ic matter (CPOM), fine particulate organic matter (FPOM), and dissolved org anic matter (DOM). Epilithon was collected monthly from unglazed, ceramic t iles in 12 stream reaches and measured for ash-free dry mass (AFDM) and chl orophyll-a. CPOM and FPOM concentrations were higher during the wet season (1 October-30 April) than the dry season (1 May-30 September). Averaged acr oss sites, CPOM and FPOM concentrations were positively related to mean dai ly discharge averaged over the 7 days before sample collection. In contrast , discharge and DOM concentration were inversely related. DOM concentration was positively correlated to chlorophyll-a accrual. Seasonal variation in epilithic chlorophyll-a and AFDM accumulation was high. AFDM accumulation r ates ranged from a low in January 1997 of 0.31 to a high of 3.6 mu g cm(-2) d(-1) in May 1997. As with organic matter in stream water, discharge influ enced the temporal dynamics of epilithic biomass accumulation; there was a negative correlation between discharge and epilithic AFDM.