Lennon, J. T. University of Kansas, email@example.com
Peterson, . T. Marine Biological Laboratory,
Wollheim, . Marine Biological Laboratory,
STORAGE AND TRANSPORT OF FINE PARTICULATE ORGANIC MATTER IN AN EXPERIMENTALLY ENRICHED RIVER
Autotrophic communities of the Kuparuk River have been drastically altered by longterm phosphorus enrichment. Cobbles previously colonized by epilithic algae are now dominated by a bryophyte community. Bryophytes increase the complexity and surface area of the river substrate and therefore have the potential to influence deposition and resuspension of organic matter. In this study, I investigated the impacts of phosphorus enrichment on the dynamics of fine particulate organic matter (FPOM). FPOM standing stocks were estimated for four sub-habitats in both pool and riffle environments: loose surface, surface biofilm, loose subsurface, and subsurface biofilm. Comparisons between enriched and reference reaches revealed that enriched riffle habitats had significantly more loose surface FPOM than the reference reach; 836.00 +/- 344.00g/m2 and 3.61 +/- 0.23g/m2 respectively. In addition, a comparatively high isotopic 15N signature for this sub-habitat suggests that FPOM turnover rates may be depressed.
Turnover experiments indicate that settling rates between pool and riffle habitats were not different, and that resuspension accounts for differences in standing stocks. Comparisons between settled FPOM and resuspended FPOM from tiles in pools revealed that 16% of settled material remained per day. In riffle habitats only 2% of settled FPOM remained on bare tiles, whereas moss tiles, simulating bryophyte covered cobbles, retained 80% more settled FPOM. The resuspension of FPOM significantly increases with local stream velocity, however, increased substrate complexity due to phosphorus enrichment retains FPOM from downstream transport.
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