Environmentally informed ecophysiology around the globe As biologists, we are interested in the variability of the physical environment where our organisms reside. By understanding current oxygen, pH, and temperature dynamics, we strive to understand the current local adaptation in our study sites, potentially elucidating the fate of these organisms to the impending effects of global change. Here, our operational goal is to co-locate oceanographic sensors with "biology" in order to explore the scope for adaptation, acclimatization capacity, and physiological response of marine organisms as a function of natural variation in pH, the ocean acidification seascape.
Collecting water samples around a dense eelgrass bed at Prisoner's Harbor, Santa Cruz Island in the Channel Islands National Park and Channel Islands National Marine Sancuary.
Understanding pH exposure in the field allows us to generate ecologically relevant future ocean acidification scenarios for laboratory experiments. We select our research sites based on oceanographic features and the spatial mosaic of natural pH variability ranging from near-shore Antarctic waters to tropical coral reefs and temperate kelp forests. Currently, all physiology research in the lab, from California to Antarctica, is nested within one of these sensor networks.
Durafet-based pH Sensors Specifically, The Hofmann Lab currently operates SeaFET and SeapHOx sensors for pH measurements, which were initially fabricated by the Martz Lab at Scripps Institute of Oceanography and later commercialized by Satlantic. Six intertidal ipHat sensors are also operated by the lab, fabricated by MBARI and deployed in collaboration with the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO).These sensors all utilize a Honeywell Durafet, which has a solid-state design that delivers significant improvements in durability and stability over longer timeseries.
Laboratory-based Experimental CO2 system In our lab, we seek to use our sensor data to develop informed laboratory experiments that use the sensor data to account the natural history of the organism. By understanding the environment that organisms may be locally adapted to, we can create experiments that assess whether current conditions stress the physiological limits of organisms and use predictions of future conditions to shed light on the fate of marine coastal communities to global change.
Our laboratory system for manipulating the pCO2 (partial pressure of carbon dioxide) in seawater has undergone refinement since it was initially conceived (Fangue 2010). We create air of a certain pCO2 by combining precise amounts of carbon dioxide to CO2-scrubbed air. then equilibrate the seawater via venturi injection. This CO2-treated water can be used in both open and closed-flow sytems.
Our current setup allows us to equilibrate 3 pCO2 treatments at 2 temperatures, for a maximum of 6 experimental treatments in a full-factorial design. This system can also be used in conjunction with an electronically-controlled switching system in order to subject organisms to periodic changes in pCO2 to mimic diurnal cycles of pH or upwelling events.