Publication Date

Spring 2024

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Thomas Connolly; Michael Graham; Diana Steller

Abstract

Nutrient distribution and propagule dispersal within Giant kelp (Macrocystis pyrifera) forests are significantly influenced by turbulence. In-situ measurements of turbulence within giant kelp forests are limited and driving mechanisms are primarily informed by controlled-flume experiments. This study investigates relationships between currents, surface gravity waves, and turbulence within a kelp forest through deployment of moored instrumentation and kelp surveys in Stillwater Cove, California during summer of 2022. Oceanographic conditions were primarily driven by coastal upwelling and a semi-diurnal internal tide, which was associated with cooling events and enhanced onshore velocity within the kelp forest during rising tides. Estimates of gradient Richardson numbers and kelp Reynolds numbers indicate that shear-instabilities are rare, while enhanced bottom velocities could consistently generate turbulent kelp wake. Turbulent kinetic energy dissipation rate (ε) spans a range of 1.9 x 10-8 to 8.0 x 10-7 m2/s3 and is positively correlated with onshore velocities, but uncorrelated with offshore velocities. This asymmetrical pattern may be triggered by cooling events that generate turbulence through interactions with dense kelp and rough bottom substrate. Models of submerged vegetation wake production and bottom boundary layer turbulent kinetic energy were compared to observed values of ε to assess hypothetical kelp and bed drag coefficients. Study results indicate that kelp density is important for future studies of nutrient distribution and propagule dispersal.

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