Seminars

This Week: Large zooplankton and their predators in a warming Bering Sea: Ecosystem and life-history modeling approaches

Join us Thursday for Neil Banas‘s Seminar: Large zooplankton and their predators in a warming Bering Sea: Ecosystem and life-history modeling approaches

Image from a poster that Neil presented at the Center for Ocean Life workshop on Trait-Based Approaches to Marine Organisms, giving an overview of ecosystem and life-history models now under development.

Details:

UW School of Aquatic & Fishery Sciences
102 Fishery Sciences (Auditorium)
1122 NE Boat Street
Time: 4:00-5:00pm (social follows seminar)
More info: 206-543-4270; safsdesk@u.washington.edu
http://eagle.fish.washington.edu/seminar

Abstract 

The eastern Bering Sea yields nearly half of the total U.S. fisheries catch. Interannual variability in recruitment of pollock and other key pelagic fisheries has been linked to variability in the abundance of large crustacean zooplankton (LCZs). This talk describes results from three recent, linked model studies–1) a high-resolution projection of ice cover and circulation under future climate, 2) a new planktonic nutrient-cycling model built using rich datasets from the 2007-10 NSF BEST (Bering Ecosystem Study) program, and 3) a novel, trait-based representation of copepod life history–that are beginning to elucidate the mechanisms that link LCZs and their predators to climate on interannual and interdecadal scales.

The planktonic ecosystem model reproduces both micro and macro features of Bering Sea primary production dynamics: on the micro scale, the time evolution of community structure and flux ratios during an intense ice-edge bloom observed in April 2009, and on the macro scale, observed relationships between annual ice-retreat timing and spring bloom timing for the northern and southern middle-outer shelves, 1978-2012. This multidecadal hindcast suggests that total spring-summer primary production is higher in warm years, whereas large copepods have been observed to decline in warm years and increase in cold years: in other words, that observed interannual variability in LCZs occurs in spite of, not because of, spring-summer conditions.

To estimate the sensitivity of LCZs to temperature and prey variability at other times of year, simple, exploratory experiments were performed using a new optimal-life-history model of Calanus glacialis/marshallae, an abundant, large copepod. The model resolves not just biomass by life stage but also stored lipids, which are important to the copepods that store them as a dynamic life-history adaptation and important to fish, bird, and mammal predators as a determinant of prey quality. This model suggests that Calanus spp. success is extremely sensitive to low levels of prey availability in late winter (before the spring bloom), and therefore to the dynamics of ice-associated phytoplankton. The talk will conclude with speculations on the implications for arctic and subarctic food webs more generally, and new model strategies for making regional predictions in high-latitude seas.

Biography
Neil Banas is a biophysical oceanographer at the UW Joint Institute for the Study of the Atmosphere and Ocean (JISAO) and School of Oceanography. He has studied interactions among circulation, water quality, plankton ecology, and impacts on fisheries since 1998. His current research projects take place in the coastal Pacific Northwest and Salish Sea, Bering Sea, and Mathematical Funland. He teaches environmental humanities through the UW Honors Program and Program on the Comparative History of Ideas (CHID).