[Ecolunch] Ecolunch Thurs 9/14

[Allen Hurlbert]

Please join us for this week's Ecolunch seminar on Thursday, September 14th at 12:15 p.m. Our speaker will be Dr. Anne Solomon, a new postdoc at the Marine Science Institute at UCSB. The title of her talk is "Top down control leads to the alteration of a coastal ecosystem in Alaska". The abstract is pasted below.

Allen


ABSTRACT
On the Kenai Peninsula, Alaska, I investigated the relative roles of natural factors and shoreline harvest leading to recent declines of the black leather chiton (Katharina tunicata), a local subsistence food source and recognized keystone grazer. I took two approaches to determine the causes of decline: a space-for-time substitution examining the significant predictors of Katharina density and biomass across 11 sites; and a survey of traditional ecological knowledge, calibrated by archeological, historical and quantitative fisheries landing data. Strong evidence suggests that current spatial variation in Katharina density is significantly related to human exploitation and sea otter (Enhydra lutris) predation. Traditional knowledge & historical data further revealed that a historical concentration in shoreline collection pressure, increased harvest efficiency and the serial depletion of alternative prey (sea urchin, crab, clams, and cockles) have likely led to intensified per capita predator impacts on Katharina and thus its recent localized decline.  Potential consequences of this decline were tested with experimental removals of Katharina at 5 sites varying in ambient grazer density and wave exposure. These manipulations demonstrated that Katharina can reduce benthic primary production by 98%, and intertidal species richness by 38%. However, under extreme top-down control, where Katharina densities had been severely depleted, this consumer became functionally unimportant. Stronger population-level impacts of Katharina at higher densities arise because its per capita interaction strength was constant as a function of ambient grazer densities. Consequently, to predict the collective impact of Katharina depletion, it is possible to scale up from per capita to population-level effects based on grazer density if wave exposure remains relatively constant. Across-site comparisons showed that biomass of the dominant intertidal kelp, Alaria marginata, was 6.1 times greater at exploited versus unexploited sites and that intertidal community differed significantly. These results provide evidence of a trophic cascade and reveal the extent to which fishing and natural predation, via the reduction of a shared keystone resource, indirectly alter a temperate coastal ecosystem.



GENERAL INFORMATION 
Ecolunches are Thursdays, at 12:15 pm (Brown Bag Lunch) National Center for Ecological Analysis and Synthesis, 735 State St., Suite 300, Santa Barbara, CA 93101 Phone: (805) 892-2500

A schedule of upcoming Ecolunch seminars is available on the web at:
http://www.nceas.ucsb.edu/fmt/doc?/nceas-web/center/local/ecolunch.html

DIRECTIONS FROM UCSB BY BUS: You can get to NCEAS by taking the 11:40 a.m. bus (# 24x) from campus. From the transit center, walk one block east to State Street and two blocks south to the Balboa Building at 735 State Street. To return to campus, you can take the 1:30 p.m. bus (#24x) from the transit station and be back on campus by 1:49 p.m. Or you can take the 2:20 p.m. bus and arrive on campus at 2:39.

BY CAR: take Highway 101 South. Once in Santa Barbara, exit on Carrillo Street. Turn left onto Carrillo. Drive 5 blocks and turn right on State Street. NCEAS is located on the right side at 735 State St., Suite 300. To Park: Drive past NCEAS on State Street and make your first right on Ortega Street. Drive 1 block and turn right on Chapala Street. Park in the underground Mall parking lot on your right. (First 75 minutes free). Once you are at the Balboa Building: We are on the third floor in the lounge area.