Finlay, J. C.. University of California, jfinlay@socrates.berkeley.edu
Power, M. C.. University of California, mepower@socrates.berkeley.edu
Cabana, G. University of California, gcabana@socrates.berkeley.edu

 
EFFECTS OF WATER VELOCITY ON ALGAL CARBON ISOTOPE RATIOS: IMPLICATIONS FOR RIVER FOOD WEB STUDIES
 
We used variation in algal del13C between river habitats to study predator and prey mobility, and the spatial scale of energy flow through river food webs. We found a strong negative relationship between herbivore del13C (which reflects algal del13C) and water velocity in three productive Northern California rivers but not in unproductive streams. The contrast between habitats suggests that water velocity affects algal del13C most strongly when CO2 availability is low relative to photosynthetic rates. Our results help explain the wide variation in published river biota del13C and show that past studies using carbon isotope analyses may have significantly underestimated the importance of algal-derived carbon to river food webs. While flow-related variation in del13C complicates this common application of carbon isotope analysis, we show that it provides a natural tracer of the flux of algal production derived from different habitats within rivers to higher trophic levels.
 
Day: Wednesday, Feb. 3
Time: 09:00 - 09:15am
Location: Eldorado Hotel
 
Code: SS32WE0900E