Ulva is a green seaweed genus (Chlorophyta) widely distributed in intertidal and shallow
subtidal environments and has gained attention for its aquaculture potential as a source of
food and high-value bioproducts. In particular, ulvan, a sulfated polysaccharide of the
Ulvophyceae cell wall, has been extensively investigated for its biochemical properties and
applications in biotechnology and pharmaceuticals. Although several studies have
examined how abiotic factors modulate ulvan production, little is known about the effects
of tidal exposure on its content.
This study aims to investigate differences in ulvan content in Ulva exposed to different
degrees of simulated tidal exposure. Given the high plasticity of Ulva morphology and
chemical composition under varying environmental conditions and the role of ulvan in
maintaining thallus moisture during low tide, we hypothesize that desiccation stress
promotes resource allocation to ulvan production rather than growth, resulting in increased
ulvan content with longer aerial exposure.
Thalli of a high-performing Ulva strain selected for regenerative aquaculture applications
will be cultivated in 2-L aquaria (2.5 g L⁻¹; n = 3) containing enriched filtered seawater (36
PSU; 0.5 mL L⁻¹ Guillard solution), under constant aeration, an irradiance of 150 μmol
photons m⁻² s⁻¹, and a 14-h photoperiod. Thalli will be exposed daily to simulated low tides
of 0.5, 1, and 1.5 h, and a control (0 h), for 15 days. Seawater pH will be monitored daily,
while photosynthetic performance and rapid light curves will be assessed every three days
using a Diving-PAM II. Every seven days, fresh biomass and ulvan content will be
determined.
This study will provide new insights into the effects of tidal exposure on ulvan production
and contribute to optimizing Ulva cultivation and its sustainable exploitation.