Zeta potential of motile spores of the green alga Ulva linza and the influence of electrostatic interactions on spore settlement and adhesion strength

The zeta potential of the motile spores of the green alga (seaweed) Ulva linza was quantified by video microscopy in combination with optical tweezers and determined to be -19.3 +/- 1.1 mV. The electrostatic component involved in the settlement and adhesion of spores was studied using electret surfaces consisting of PTFE and bearing different net charges. As the surface chemistry remains the same for differently charged surfaces, the experimental results isolate the influence of surface charge and thus electrostatic interactions. Ulva spores were demonstrated to have a reduced tendency to settle on negatively charged surfaces and when they did settle the adhesion strength of settled spores was lower than with neutral or positively charged surfaces. These observations can be ascribed to electrostatic interactions.