Measuring tissue water potential in marine macroalgae via an updated Chardakov method.

Area of Science:

• Marine biology
• Physiological ecology
• Phycology

Background:

• Macroalgal osmotic responses are vital in dynamic coastal environments.
• Measuring macroalgal tissue water potential is challenging due to limitations of existing methods like leaf psychrometers.
• Knowledge gaps persist regarding macroalgal physiological adaptations to varying salinity.

Purpose of the Study:

• To present an updated Chardakov method for measuring macroalgal tissue water potential.
• To investigate the osmotic responses of two distinct macroalgal species to simulated estuarine conditions.
• To assess macroalgal plasticity in response to gradients from oceanic to brackish submarine groundwater discharge.

Main Methods:

• An updated Chardakov method was employed to measure tissue water potential.
• Two species, Ulva lactuca and Hypnea musciformis, were subjected to controlled salinity and nutrient treatments at varying temperatures.
• Treatments simulated conditions from full coastal ocean to brackish submarine groundwater discharge.

Main Results:

• Both Ulva lactuca and Hypnea musciformis exhibited significant osmotic plasticity.
• Tissue water potential positively correlated with the proportion of submarine groundwater discharge in treatments.
• This study provides the first description of macroalgal tissue water potential responses.

Conclusions:

• The revised Chardakov method is a valuable tool for studying macroalgal osmotic responses.
• Understanding tissue water potential is key to macroalgal physiological ecology in complex coastal systems.
• This method can enhance studies in other tidal systems and across different life stages.