Dataset Information

A direct CO₂ control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

ABSTRACT: Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO₂. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO₂. Here we describe a system in which the target pCO₂ is controlled via direct analysis of pCO₂ in seawater. This direct type of control accommodates potential temperature and salinity shifts, as the target variable is directly measured instead of being estimated. Water in a header tank is permanently re-circulated through an air-water equilibrator. The equilibrated air is then routed to an infrared gas analyzer (IRGA) that measures pCO₂ and conveys this value to a Proportional-Integral-Derivative (PID) controller. The controller commands a solenoid valve that opens and closes the CO₂ flush that is bubbled into the header tank. This low-cost control system allows the maintenance of stabilized levels of pCO₂ for extended periods of time ensuring accurate experimental conditions. This system was used to study the long term effect of OA on the coralline red algae Phymatolithon lusitanicum. We found that after 11 months of high CO₂ exposure, photosynthesis increased with CO₂ as opposed to respiration, which was positively affected by temperature. Results showed that this system is adequate to run long-term OA experiments and can be easily adapted to test other relevant variables simultaneously with CO₂, such as temperature, irradiance and nutrients.

SUBMITTER: Sordo L

PROVIDER: S-EPMC5045892 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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A direct CO2 control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

Sordo Laura L Santos Rui R Reis Joao J Shulika Alona A Silva Joao J

PeerJ 20160927

Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However, accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. This direct type of control accommodates potential temperature and salinity shifts, as t ...[more]

PMID: 27703853

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Project description:BackgroundRed coralline algae are critical components of tropical reef systems, and their success and development is, at least in part, dependent on photosynthesis. However, natural variability in the photosynthetic characteristics of red coralline algae is poorly understood. This study investigated diurnal variability in encrusting Porolithon sp. and free-living Lithophyllum kotschyanum. Measured parameters included: photosynthetic characteristics, pigment composition, thallus reflectance and intracellular concentrations of dimethylsulphoniopropionate (DMSP), an algal antioxidant that is derived from methionine, an indirect product of photosynthesis. L. kotschyanum thalli were characterised by a bleached topside and a pigmented underside.ResultsMinimum saturation intensity and intracellular DMSP concentrations in Porolithon sp. were characterised by significant diurnal patterns in response to the high-light regime. A smaller diurnal pattern in minimum saturation intensity in the topside of L. kotschyanum was also evident. The overall reflectance of the topside of L. kotschyanum also exhibited a diurnal pattern, becoming increasingly reflective with increasing ambient irradiance. The underside of L. kotschyanum, which is shaded from ambient light exposure, exhibited a much smaller diurnal variability.ConclusionsThis study highlights a number of dynamic photoinhibition strategies adopted by coralline algae, enabling them to tolerate, rather than be inhibited by, the naturally high irradiance of tropical reef systems; a factor that may become more important in the future under global change projections. In this context, this research has significant implications for tropical reef management planning and conservation monitoring, which, if natural variability is not taken into account, may become flawed. The information provided by this research may be used to inform future investigations into the contribution of coralline algae to reef accretion, ecosystem service provision and palaeoenvironmental reconstruction.

Dataset Information

A direct CO₂ control system for ocean acidification experiments: testing effects on the coralline red algae Phymatolithon lusitanicum.

Publications

A direct CO<sub>2</sub> control system for ocean acidification experiments: testing effects on the coralline red algae <i>Phymatolithon lusitanicum</i>.

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