October 31 2013

5:00 pm BSRB 154

EcoEvoPub Series

Graduate Student Presentations


Sarah Joy Bittick
Department of Ecology and Evolutionary Biology

"Development of a Macroalgal Assessment Framework to Diagnose Seagrass Bed Health"

Seagrass beds worldwide are experiencing major declines due to harmful algal blooms associated with nutrient-rich runoff and recent evidence suggests macroalgae may play a key role. Therefore, it is important to document benchmarks in the response of seagrasses to bloom-forming macroalgae and how levels of adverse effect change as a function of type of macroalgae. We investigated the impact of varying abundances of two common macroalgal genera in California estuaries, Ulva spp. and Gracilariopsis spp., on the health of the eelgrass Zostera marina. We conducted a caging experiment in 1 m2 plots of a Z. marina bed in Bodega Bay where we maintained five densities of Ulva (0, 1.0, 1.5, 2.0, 3.0, and 4.0kg/m2) and Gracilariopsis (0, 0.75, 1.0, 1.5, 1.75, and 2.0kg/m2) and uncaged controls over a 10 week summer growing season. Every two weeks algal samples were collected and Zostera growth, epiphyte load, and shoot density measured; the two algal species were also added or removed from plots to reset treatment levels. The abundance of Ulva in plots grew or remained consistent in each 2 week interval while there was a consistent decrease in Gracilariopsis. There was a negative relationship between Ulva abundance and Zostera shoot density with an approximately 50% decrease in shoot density over the course of 10 weeks in the three highest Ulva treatments. Ulva treatments > 2.0kg/m2 also experienced a three-fold decrease in epiphyte abundance and slower overall Zostera growth. There was no measurable effect of Gracilariopsis except for a trend of decreased epiphyte abundance at 1.75 and 2.0kg/m2. Thus, we found species-specific benchmarks, perhaps due to biomass persistence, direct negative effects on seagrass itself, and potential impacts on grazing food chains with loss of epiphytes.

Zachary Schakner
Department of Ecology and Evolutionary Biology

"Startling Sea Lions: A Possible Solution for Southern California Fishermen"

Pinniped depredation, or removal of fish from actively fished gear, from commercial and recreational fishing vessels has been observed for decades. Over time, these interactions have become more acute because sea lion and harbor seal populations have increased dramatically. Interactions are a concern from a scientific, management, and conservation perspective. I am presenting initial results of a novel acoustic startle device for eliciting sea lion avoidance of the fishing vessels. Preliminary results suggest that the startle device reduces the impacts on fishermen due to sea lions by reducing the number of individuals and the time spent at the stern foraging. I will discuss how Pavlovian fear conditioning may increase effectiveness of deterrents based upon initial results from conditioning trials taking place on bait docks.















































































































































































































































































































































































































































































































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