| Hydrodynamics strongly influences the role of benthic filter feeders in benthic-pelagic trophic coupling in large lakes. In this dissertation I investigate the interactions of vertical turbulent mixing, light and particulate and dissolved constituents in a large lake, Lake Erie. Diel average eddy diffusivity estimates varied from 10−5 to 10−4 m2s−1 at the sample site location. The simulations indicate that eddy diffusivities of this order of magnitude can result in extremely low algal biomass near the benthos, while the upper water column remains relatively unaffected. Discounting inputs from algal reproduction, I estimate that between 8 and 67% of the algal biomass is consumed each day at the sample site, depending on the shape and magnitude of the diffusivity profile. Measured vertical biomass profiles have a zone of algal depletion near the benthos, but little evidence of depletion near the surface. I found the daily flow of algal biomass into the benthos was strongly coupled with the magnitude of turbulent mixing, suggesting the flux of algal biomass into the benthos was small compared with previously published estimates that ignored the paucity of turbulent mixing occurring.; Vertical mixing can also cause changes in exposure to incident radiation. The depth of the wind-mixed layer and diel thermoclines often determine the light climate of individual plankters, which, due to the random nature of turbulence can be different for plankters at the same depth. I develop a method to estimate primary productivity, considering the effects of vertical turbulent mixing. Photosynthesis may be underestimated by as much as 45%. However, diel thermocline formation reduces this effect, trapping algae near the surface and causing near surface declines in production. Separated from the source of mixing, the surface wind-shear, the lower water column primary production is still increased by more than 15% relative to the static model.; The trophic status of the lake has undergone profound changes due to the changing phosphorus loading and introduction of the exotic zebra mussel into the lake. I therefore test the importance of hypolimnion thickness on oxygen depletion, a measure of the total loss of oxygen in the hypolimnion over time (expressed per unit area). (Abstract shortened by UMI.)... |
