Development of an economical, autonomous pHstat system for culturing phytoplankton under steady state or dynamic conditions.
Laboratory investigations of physiological processes in phytoplankton require precise control of experimental conditions. Chemostats customized to control and maintain stable pH levels (pHstats) are ideally suited for investigations of the effects of pH on phytoplankton physiology, for example in context of ocean acidification. Here we designed and constructed a simple, flexible pHstat system and demonstrated its operational capabilities under laboratory culture conditions. In particular, the system is useful for simulating natural cyclic pH variability within aquatic ecosystems, such as diel fluctuations that result from metabolic activity or tidal mixing in estuaries. The pHstat system operates in two modes: (1) static/set point pH, which maintains pH at a constant level, or (2) dynamic pH, which generates regular, sinusoidal pH fluctuations by systematically varying pH according to user-defined parameters. The pHstat is self-regulating through the use of interchangeable electronically controlled reagent or gas-mediated pH-modification manifolds, both of which feature flow regulation by solenoid valves. Although effective pH control was achieved using both liquid reagent additions and gas-mediated methods, the liquid manifold exhibited tighter control (±0.03pH units) of the desired pH than the gas manifold (±0.10pH units). The precise control provided by this pHstat system, as well as its operational flexibility will facilitate studies that examine responses by marine microbiota to fluctuations in pH in aquatic ecosystems.
Institute of Environmental Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States; Science and Technology Center for Coastal Margin Observation and Prediction, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States. Electronic address: goldar@ohsu.edu.
Rachel L
RL
Golda
SSI Consulting, P.O. Box 2155, Shelton, WA 98584, United States.
Mark D
MD
Golda
Science and Technology Center for Coastal Margin Observation and Prediction, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States.
Jacqueline A
JA
Hayes
Institute of Environmental Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States; Science and Technology Center for Coastal Margin Observation and Prediction, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States.
Tawnya D
TD
Peterson
Institute of Environmental Health, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States; Science and Technology Center for Coastal Margin Observation and Prediction, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, United States.
Joseph A
JA
Needoba
D002244:Carbon / Q000378:metabolism; D046508:Culture Techniques / Q000191:economics* / Q000295:instrumentation* / Q000379:methods*; D017753:Ecosystem; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D009792:Oceans and Seas; D010839:Phytoplankton / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D012623:Seawater / Q000737:chemistry; D012984:Software; D013997:Time Factors; D014871:Water Microbiology
D002244:Carbon
Continuous culture; Ocean acidification; Phytoplankton; pH; pHstat