PROFESSOR LISA LEVIN
UC San Diego
Sept. 25 @ 12 PM
AHF Torrey Webb Room
Persistent hypoxia (low oxygen) alters both structural and functional aspects of benthic communities, with major consequences for ecosystems services at shallow and bathyal depths. Continental margins subject to upwelling exhibit strong gradients in oxygen, CO2 and temperature, and can serve as ideal natural laboratories for the study of environmental stressors. Several decades of study of open ocean oxygen minimum zones (OMZs) reveal massive influence of oxygen on benthic abundance, biomass, body size, species composition, species distributions, lifestyles and biodiversity. Differing low-oxygen sensitivities exist among taxa as a function of phylogeny, body size and exposure history, leading to very different oxygen thresholds and responses. Functional consequences of the structural changes include shifts in trophic pathways and efficiency, enhanced roles for chemosynthesis, altered predator and prey encounter dynamics, changing pathways of carbon processing and burial, reduced ecosystem resilience, connectivity and a host of other emergent properties.
As a result of rising CO2 in the atmosphere, upwelling margins are experiencing increased coastal hypoxia and hypercapnia (high CO2). The strong natural variability of O2 and CO2 on multiple time scales poses a challenge for understanding population and ecosystem responses to OMZ expansion. Approaches for resolving the effects of declining oxygen and pH on margin ecosystems and their services include the use of natural environmental gradients, laboratory manipulations, geochemical proxies and time series data. Scientists today are faced with a need to integrate the influence of natural variability, climate-driven change and direct human activities in management of continental margin ecosystems and resources. The US West coast is increasingly becoming a testbed for ways to address this challenge.