Dr. Otaiza-O'Ryan, Ricardo

Several seaweed species are commercialized worldwide both due to high demand for food and feed and as a raw material for the extraction of phycocolloids such as agar, carrageenan, and alginates that are used broadly in the food, cosmetic, and pharmaceutical industries. Chile is the world’s leading marine seaweed biomass producer when it comes to the exploitation of natural kelp beds. This extraction pressure has persisted for decades and has resulted in a reduction in natural stocks along the benthic ecosystems of the Chilean coast. Over the last three decades, several strategies aimed at restoring seaweed stocks have been implemented (i.e., sexual and asexual reproduction, the use of spore-type propagules or fragments of thalli, and entire thallus transplants). Success rates have varied, but the biological feasibility of such strategies has been demonstrated for several species. However, technological improvements must be achieved to move from small-scale, pilot experiments to cost-effective restocking strategies that are easy to transfer to fisher communities and another end-user, scalable to marine field conditions, and socio-ecologically sustainable. Researchers in other geographic areas have explored similar pathways for developing kelp restocking strategies and have tackled the research gaps regarding its massification. This work summarizes the research activities carried out in recent decades in the search for sustainable strategies to restore algal stocks in Chile.

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.

Variability in thallus morphology is common in red seaweeds. Two co-occurring forms have been described for Chondracanthus chamissoi based mainly on blade width. To determine whether two distinct forms or a range of intermediate morphologies occur in C. chamissoi, thalli were collected from three localities in southern Chile in autumn–winter, repeating the sampling in one locality in spring and in summer. In each occasion, individual sporophytic and male and female gametophytic clumps were collected, and the longest blade with intact apex from each clump was evaluated. Blade length, width, density of spines, axis curvature and thickness, and pinnule length and width were evaluated in each blade. Principal components analyses separated two groups of thalli, one group with narrow, thick, and curved (concavo-convex) blades, with few spines consistent with f. lessonii, and another with broad, thin, and flat blades, with many spines consistent with f. chauvinii. These variables also had bimodal frequency distributions. Pinnule measurements were mainly associated with differences among sporophytes and gametophytes. Age (length), phase of the life cycle, and sex were not related to the forms. Furthermore, thalli of both forms were collected side by side in the study sites and throughout the year so the occurrence of the two forms was not attributable to local environmental conditions. In this species, secondary basal disks are produced after attachment of apexes to the substratum. These disks may produce blades with a modified morphology in a way similar to proliferations and regenerations described for Schottera nicaeensis.

The red seaweed Chondracanthus chamissoi shows high morphological variability. Initially, three species were identified based on the width of the main axis of their blades. Later, all of them were included in a single species with two morphological groups. Recently, quantitative studies demonstrated the existence of two forms in C. chamissoi: f. lessonii and f. chauvinii. It was also shown that these two forms occur in sympatry, growing side by side. These forms were not associated with either a life cycle phase or the sex of the blades. This study aimed to determine whether the two forms could represent different species. We evaluated the forms' taxonomic position using COI and rbcL markers, including samples from three localities in southern Chile. All specimens shared a single rbcL haplotype, whereas the two COI haplotypes differed by four base pairs and were present in blades of both forms and life cycle phases. The two morphological types correspond to intraspecific forms. This species is of commercial importance, and its main market is aimed at human consumption with a marked preference for f. lessonii.

Morphological variability is common among macroalgae. In central Chile, Mazzaella laminarioides extends throughout the intertidal rocky zones, where blades are reported to grow up to 20 cm in length. Nevertheless, in low rocky intertidal zones with sand-influence, blades are noticeably larger than in other shores without sand effect. The aim of this study was to compare the morphology of M. laminarioides blades from two different conditions. Blades collected from four sites with, and four without, sand-influence were evaluated with traditional morphometry. Results showed that blades were longer and wider in sand-influenced sites. Sand abrasion was not directly evaluated, but indirect effects such as the abundance of bare rock and of sand tolerant species were higher in areas with sand-influence. Also, long blades were restricted to sand-influenced sites, supporting the relation between these two variables. Molecular analyses using the COI marker confirmed large-bladed individuals as M. laminarioides. Results indicated that life cycle phase, seasonality and vertical height were not related to large blades. We suggest that restriction of large blades to sand-influenced sites may be related to the healing processes of basal holdfasts after suffering sand abrasion.

Fragments of Chondracanthus chamissoi have the capacity of secondary attachment. In the laboratory, apexes of upright branches of C. chamissoi placed 1–2 mm and parallel to horizontal substrata underwent morphological transformation prior to becoming attached, changing from thick and blunt to elongated and cylindrical and from straight to curved towards the substratum, where they eventually produced secondary attachment discs. When transformation occurred, signs could already be observed after 3 days of incubation. Several factors that could affect transformation and attachment were tested. The vertical or horizontal orientation of the fragments, the angle of incidence of light, and the phase of the life cycle had no effect on transformation, whereas the presence of reproductive structures had a negative effect compared to vegetative fragments. Low light intensity and low water flow favored the transformation response. Calcareous substrata (bivalve shells and coralline crusts) produced the highest frequency of transformation and other solid substrata (glass slides, rock, and sea-squirt tunic) followed in the ranking, but fleshy seaweeds (Ulva sp., Sarcothalia crispata, and C. chamissoi) failed to produce any response. Thus, the experimental upright branches developed features and reactivity similar to basal branches when the former were placed in conditions similar to those where the latter occur in the natural environment. Vegetative reproduction has been incorporated in cultivation techniques of C. chamissoi, but it could also be used in repopulation or restoration programs of this species.

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.