Seminar - Johanna Rosman - From wetsuits and salt spray to lab coats and lasers: Studying the effects of Giant Kelp on nearshore currents

Johanna Rosman
Postdoctoral Scholar
Environmental Fluid Mechanics Laboratory
Stanford University


Wednesday 2 April 2008, 1.10 - 1.55 pm
Civil Engineering Lecture Theatre 3

Abstract:

Macrocystis pyrifera (Giant Kelp) forests are an important component of temperate coastal ecosystems, providing food and shelter to a diverse array of organisms. Within a kelp forest, hydrodynamics can control the transport of nutrients, food particles, larvae and spores at scales ranging from boundary layers around individual kelp blades (millimeters) to entire kelp forests (kilometers). In addition, kelp forests present regions of high drag to incident flows, and thus have the potential to alter the flow environment. This talk will describe field and laboratory experiments that investigated the effects of kelp forests on nearshore hydrodynamics. Instruments were deployed in and around kelp forests near Santa Cruz and Santa Barbara, California, to look at modification of currents, internal waves and surface waves by kelp forests. A 1/25-scale model of a kelp forest was developed to investigate the effects of kelp forest physical structure on currents and turbulent mixing in a controlled laboratory setting. Collectively, these studies show that kelp forests significantly modify both mean flows and turbulent mixing, and that these effects vary with both the time scales of the flow, and with seasonal and interannual changes in kelp forest structure.