Dr. Otaiza-O'Ryan, Ricardo

Gelidium lingulatum is a frequent species at low intertidal levels of wave-exposed, rocky shores in central Chile. It is harvested from natural stands by artisanal fishermen and sold as raw material for the extraction of the valuable phycocolloid agar.Mass cultivation of this species has not been developed. In this study, we describe a device that allows seeding fragments of G. lingulatum to be used to increase biomass or to repopulate areas damaged by natural or anthropogenic disasters. The device consists of a nylon rivet and a mesh-washer that is pushed in perforations drilled on the rocky shore, holding the seaweed fragments appressed to the substratum favoring secondary attachment. Seeding was done on three sites in each of three localities within the Biobío Region (southern Chile), considering also the type of substratum (rock, calcareous crusts, and barnacles). The transplant units were installed in (austral) winter, 2016, and evaluated in spring and summer 2017. Results showed that, except for human intervention, most seeded fragments grew successfully as new patches and growth rates of up to 1.2% day−1 were recorded. Some significant differences were detected among sites and among substrata, but these can be interpreted as differences in the environmental conditions at the small spatial scale where the patch was growing. This device is simple and inexpensive and our results show that it is effective in producing new patches of G. lingulatum, such that it can be easily applied in repopulation or restoration programs.

Species of Gelidium are important sources of agar. Mass cultivation of Gelidium spp. has been elusive. Development of techniques to seed thalli in the natural environment could be used to increase in stocks and landings. Gelidium lingulatum is an important seaweed resource in central Chile, growing on the lower levels of exposed rocky intertidal shores. Experiments were done to evaluate fragmentation of the thalli and the effect of some factors on the production of secondary attachment structures (SAS). When experimentally exposed to high water flow, thalli became frequently fragmented, mainly at the level of the creeping axes. Comparisons among parts of the thallus indicated that creeping axes produced more SAS than blades and reproductive branchlets. Similar results were obtained on the three types of substrata tested (rock, barnacle shells, and mussel shells). After 7 days of incubation, more SAS were produced under low than high irradiance (8 and 80 μmol photons m−2 s−1, respectively). Also, a small increase in dissolved calcium (0.5 mM) in the medium enhanced SAS production, but higher levels (2.0 mM) had an inhibitory effect. Higher temperature (15 °C) tended to favor SAS formation when compared to lower temperature (9 °C). For these three factors, differences in the density of SAS were reduced or disappeared after 14 days of incubation. Different seasonal series of each experiment had consistent results. Recommendations are made for the application of these results to seeding of thalli of G. lingulatum on the rocky shore.