Oceanographic Instrumentation in a Biological Context
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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.
As part of an effort to characterize the marine environment, the Hofmann Lab is equipped with an arsenal of oceanographic sensors to collect data with high spatiotemporal resolution. By developing quality control standards for prototype sensors, we have developed long-term pH time series within our own Santa Barbara Channel in a partnership with the NSF Santa Barbara Coastal Long-Term Ecological Research Project and the Channel Islands National Park , and established time series in more remote sites such as McMurdo Station and Cape Evans, Antarctica. |
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Durafet-based pH Sensors
The Hofmann Lab currently operates xxx SeaFET sensors and two SeapHOx sensors, 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).
The lab has been an early adopter of the SeaFET, deploying them from the tropics to the poles in an attempt to classify different global regimes of pH variation in remote site that benefit from autonomous collection. This has provided us with critical information that allows for environmentally relevant organismal experiments.
These sensors all utilize a Honeywell Durafet, which has a solid-state design that delivers significant improvements in durability and stability over longer timeseries. By eschewing the traditional glass pH electrode in favor of an ion-selective field transistor (ISFET), a unipolar junction FET with an ion-sensitive gate, the Durafet has provided an in-lab stability of .005 pH over weeks to months in seawater.
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. This addition, called the OASiS, can be used to mimic diurnal cycles of pH or upwelling events.
The Hofmann Lab currently operates xxx SeaFET sensors and two SeapHOx sensors, 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).
The lab has been an early adopter of the SeaFET, deploying them from the tropics to the poles in an attempt to classify different global regimes of pH variation in remote site that benefit from autonomous collection. This has provided us with critical information that allows for environmentally relevant organismal experiments.
These sensors all utilize a Honeywell Durafet, which has a solid-state design that delivers significant improvements in durability and stability over longer timeseries. By eschewing the traditional glass pH electrode in favor of an ion-selective field transistor (ISFET), a unipolar junction FET with an ion-sensitive gate, the Durafet has provided an in-lab stability of .005 pH over weeks to months in seawater.
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. This addition, called the OASiS, can be used to mimic diurnal cycles of pH or upwelling events.
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Hypoxia-Acidification Multistressor System
The lab is currently working with the SBC-LTER to devise a Hypoxia-Acidification Multistressor (HAM) System. The HAM will be able to independently manipulate both CO2 and O2 in experimental treatments to mimic future ocean acidification and hypoxia conditions. By combining sensor data with these experiments, we hope to gain a better understanding of the underpinnings of the effect of these pending multistressors on marine communities.
The lab is currently working with the SBC-LTER to devise a Hypoxia-Acidification Multistressor (HAM) System. The HAM will be able to independently manipulate both CO2 and O2 in experimental treatments to mimic future ocean acidification and hypoxia conditions. By combining sensor data with these experiments, we hope to gain a better understanding of the underpinnings of the effect of these pending multistressors on marine communities.
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Optical Oxygen Sensors
The Hofmann Lab also utilizes several oxygen sensors to inform lab experiments involving the HAM. The miniDOTs, manufactured by PME in San Diego, are small field-deployable oxygen sensors we use to create time series that profile oxygen variability in a fine spatiotemporal scale. |
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Relevant publications:
Kapsenberg, L., A.L. Kelley, E. C. Shaw, T.R. Martz and G.E. Hofmann (2015) Seasonal pH variability in near-shore Antarctica in the present and future. Scientific Reports 5, Article number: 9638.
Matson, P.G., L. Washburn, T.R. Martz and G.E. Hofmann (2014) Abiotic versus biotic drivers of ocean pH variation under fast sea ice in McMurdo Sound, Antarctica. PLoS ONE 9(9): e107239. doi:10.1371/journal.pone.0107239.
Hofmann GE, Evans TG, Kelly MW, Padilla-Gamino JL, Blanchette CA, Washburn L, Chan F, McManus MA, Menge BA, Gaylord B et al.. 2013. Exploring local adaptation and the ocean acidification seascape–studies in the California Current Large Marine Ecosystem. Biogeosciences Discussions. 10:11825–11856.
Fangue NA, O'Donnell MJ, Sewell MA, Matson PG, MacPherson AC, Hofmann GE. 2010. A laboratory-based, experimental system for the study of ocean acidification effects on marine invertebrate larvae. Limnology and Oceanography: Methods. 8:441–452.