WAVE ATTENUATION AND CHEMICAL BUFFERING: DETERMINING ECOSYSTEM SERVICES OF GIANT KELP TO SOUTHERN CALIFORNIA

Coastal sectors of Southern California are a major economic engine for the State and house a substantial proportion of residents. These communities are experiencing environmental changes that create uncertainty and challenges for future adaptation. We focus on two growing problems that may have local solutions: 1) accelerating rates of shoreline erosion due to increased storminess and amplified wave heights associated with climate change; 2) disruption of coastal resources due to shifts in seawater chemistry tied to ocean acidification. While superficially distinct, these two problems are connected in nearshore habitats via kelp forests and their interaction with surrounding waters. Kelps and other aquatic vegetation have the capacity to attenuate ocean waves, and by means of their photosynthetic activities, can alter the carbonate chemistry of seawater. Although kelp forests may offer some level of protection against erosion and acidification, their efficacy in doing so is unproven. The overall goal of this project is to determine if there are potential benefits of restoring kelp forest habitats in terms of wave attenuation and alteration of seawater chemistry. The study will take place within the Palos Verde area at two sites undergoing restoration from an urchin barren state to a kelp forest state. Through this project we will: 1) Quantify the capacity of kelp forests to damp nearshore waves. Here we will measure wave amplitudes and periods across a range of incident wave conditions, and isolate how these properties change in the presence or absence of kelps. In these experiments, we will take advantage of the relatively unusual situation where Macrocystis is arriving into a previously denuded site even as other factors ? e.g., bathymetric profile, shoreline angle, bottom rugosity ? remain constant. 2) Determine the extent to which kelp forests locally buffer seawater chemistry. Here we will measure water column chemistry across a range of oceanographic conditions, and isolate how chemistry changes in the presence or absence of kelps. As in the above, our approach will offer an unprecedented opportunity to measure shifts in water column chemistry at a site where we can unambiguously isolate the influence of the presence of kelp by sampling sites as Macrocystis arrives and grows to full density.