Cultivation of Gongolaria barbata (Fucales, Phaeophyceae) with a seaweed-derived biostimulant in order to improve photophysiological fitness and promote fertility to advance the restoration of marine macroalgal forests

Abstract

As a result of several anthropogenic factors, Cystoseira sensu lato forests have declined or become regionally extinct in many coastal regions of the Mediterranean. Given the low natural recovery of lost populations, research efforts have been encouraged to develop sustainable and efficient restoration of macroalgal forests on a large scale. By promoting growth and fertility of collected thallus branches under controlled laboratory conditions, the availability of seedlings for restoration could be ensured without jeopardizing natural populations. Here we investigated the effect of a commercial algal biostimulant (AlgatronCifo®) on the photophysiology, growth and fertility of Gongolaria barbata (Stackhouse) Kuntze (Fucales, Phaeophyceae). In a factorial laboratory experiment, two different temperatures (10 ºC and 14 °C) and two culture media [i.e. seawater (SW) and Algatron (AT)] were tested. The photosynthetic performance of G. barbata doubled after three weeks of culture with AT, while it decreased by 25% when cultivated in SW. The highest photosynthetic performance and growth were achieved at 14ºC with AT, where fertile receptacles also developed, followed by seedling settlements. The thalli cultured in AT had similar or better photosynthetic performance than the initial control thalli. AT-cultured thalli had a greater ability to quench energy via photochemical pathways (qP) than those from the SW, which on the contrary, had higher levels of non-photochemical responses (qN, NPQmax). This limited photosynthetic performance was probably linked to the higher P-limitation experienced under that treatment. The algal biostimulant enhanced the physiological performance and induced fertility of G. barbata, demonstrating its valorization potential and setting a new path for improved restoration applications.

Too Hot to Handle: Effects of Water Temperature on the Early Life Stages of Gongolaria barbata (Fucales)

“…A recent study on the cultivation of G. barbata even reported that, for thalli collected in the Gulf of Trieste, the development of fertile receptacles followed by the zygote release occurred exclusively at 14 • C [91]. Our experiments have shown that a temperature of 18 • C is still suitable for normal germlings' development, but germlings at 15 • C developed faster and reached larger lengths than others (see Figures 3 and 4).…”

“…Gongolaria barbata is a geographically widespread species that belongs to the warmtemperate Mediterranean-Atlantic group [59,63] that requires temperatures of at least 10 °C for reproduction and development of germlings. It is a monoecious species, with oogonia and antheridia that are fertile in the conceptacles from the end of winter to the end of spring [91]. After the fertili ation, heavy and large ygotes exhibit highly restricted dispersal; therefore, they fall on the substrate a few centimeters to meters away from the The percentage of deformed germlings was highest at 24 and 28 • C, 1-2 days before the critical point at which all germlings died (Figures 3 and 5).…”