| This dissertation details field and laboratory work that investigated processes for exchange between a Macrocystis pyrifera (Giant Kelp) forest and the surrounding coastal ocean, including modification of currents, internal waves, surface waves and turbulence by a kelp forest. Field measurements included vertical profiles of current and temperature, and wave measurements, in and around a kelp forest at Santa Cruz, California. Within the kelp forest, currents were reduced by a factor that correlated with surface canopy coverage, high frequency internal waves were damped, and time-averaged across-shore transport due to waves (Stokes drift) was similar in magnitude to that due to currents. Richardson numbers within the kelp forest were higher than those outside and indicate that the water column within the kelp forest was usually stable to turbulence generation by mean velocity shear. A new method is derived in this dissertation for calculating Reynolds stresses from acoustic Doppler current profiler (ADCP) measurements in the presence of waves, and is applied to the kelp forest data set.; A small-scale laboratory model of a Macrocystis forest was constructed, and velocities were measured using Particle Image Velocimetry (PIV) and Laser Doppler Anemometry (LDA). A two-layer model of momentum budget within a kelp forest is developed in the dissertation and applied to the problem of one-dimensional flow through the small-scale kelp forest. Results of the two-layer model agree well with laboratory measurements and allowed estimation of drag coefficients and prediction of flow development within kelp forests with different structures. Terms of the spatially averaged turbulent kinetic energy (TKE) equation were computed from PIV measurements. A region of very large shear production beneath the surface canopy resembles a classical plane mixing layer. Wake production due to local variations in mean shear and Reynolds stresses around individual kelp is the main source of turbulence throughout the mid-water column. Because transport terms are important in the TKE budget, gradient transport models are unlikely to be adequate for modeling kelp forest turbulence. Instead, higher order closure schemes, such as those used to model flow with and above terrestrial canopies, are recommended. |
