Key takeaways
Selected breeding, production, and outplanting of chimeras improved survivorship and genetic diversity relative to homogeneous plants.
These methods could support local adaptation and a genetic rescue of populations, especially those with a high level of inbreeding.
Background
Along the Chilean coast, kelp harvesting is the main benthic fishery, reaching 280,000 tons/year 1, with 75% the harvest consisting of Lessonia spp. (L. berteroana, L. spicata & L. rabeculate). Chile provides 10% of the global raw material for seaweed chemical compounds 2 3. Given the enormous harvesting pressure, these resources have become overharvested and subject to high levels of illegal harvesting 4. This has affected kelp forest biodiversity and associated fisheries, and also other ecosystem services (e.g., nutrient cycling). Lower kelp forest biomass also causes declines in the kelp fishers’ economic income and quality of life.
The Chilean government has created sustainability strategies in management areas (i.e., territorial usage rights for fisheries, 5) and implemented harvesting bans, with the aim to encourage kelp recovery and cultivation (Law N°20.925). The scaled cultivation and restoration of L. berteroana and L. spicata is poorly understood, however, and there have only been unsuccessful attempts to cultivate or enhance settlement via spores or juveniles.
In this context, there was opportunity to combine a natural process with technological knowledge to generate protocols for the cultivation of high-growth multi-species chimeras of L. berteroana and L. spicata, as a method to improve the effectiveness of planting efforts and the restoration of local rocky coastal ecosystems 6 7 8 9.
The project
Here we selected strains of Lessonia spicata and L. berteroana for cultivation and to build chimeras to increase fitness, resilience capabilities, and aid efforts to restore kelp and ecosystem services. For each population, we selectively bred the kelp in laboratory conditions to identify individuals with high growth rates and to develop cultures to allow outplanting of the same populations to avoid translocations of native genotypes. For each population, we also selected sporophytes to build multi-species individuals or ‘chimeras’ using a patented methodology to obtain chimeric individuals (Patent #2017-1827, PCT/CL2018/050053) and improve survival, growth, and genetic diversity in kelp species 9 10 11 12. For ethical and biosecurity considerations, we combined only those genotypes native to each population/site.
These chimeric individuals are formed when two genetically distinct conspecific individuals fuse together to generate a single entity, while still retaining two complete sets of genetic material (this differs from a hybrid, where two individuals contribute only half their genetic material towards the creation of the single individual). Chimera production in the laboratory allows the production of juveniles with a combination of performance and character traits, including improved survival, growth, and genetic diversity (Patent WO2019010588). We therefore found that restoration using these chimeras is more successful than using juveniles that were monospecific. Chimera production also improves biomass yields in the laboratory, hatchery, and the field. The larger size and greater morphological complexity can increase the area available for invertebrate habitat, photosynthesis, and CO2 capture, and maximizes population sustainability and resilience. At the same time, the increased genetic diversity promotes more robust and resilient plants and helps overcome inbreeding depression due to monoculture, harvesting pressures, and ocean warming 13 14.
Transplanting of the kelp chimeras on the intertidal rocky habitat was successful with some techniques. The chimeras showed higher adherence and survival than previous restoration efforts. (Fig. 1) Of the survivors from the restored areas, at least half of them were chimeras. Once kelps were established in the field, chimeras increased the local populations’ genetic diversity (~5 times greater), together with increased survival rates (1–3 times greater), biomass (~1.5 times greater), and morphological complexity or number of stipes (7-10 times more), all relative to monospecific individuals. Chimeras also showed higher levels of photosynthetic pigments compared to monospecific individuals and higher richness and abundance of associated invertebrate communities.
The cost of the project was US $355,118, provided by FONDEF ID17I10080 (US$ 276,065); U. Chile & UCN (US$77,388); and a private company (US$1,665).
Lessons learned
Outplanting occurred during spring and summer, but the highest survival rates were observed from plantings in early spring. This likely aligns with natural patterns of recruitment, since spore production/release of Lessonia spp. in Chile peaks in autumn-winter.
Various planting substrates were trialed, including metal plate, Vexar netting, adhesive-back Velcro, AlgaeRibbon, and two-part resin-quartz natural substrate analogue. After two months, only the Vexar netting, AlgaeRibbon, and Velcro has surviving kelp, and after six months, survivors only remained on the AlgaeRibbon and Velcro (and at similar densities).
Different attachment methods were also trialed using the Vexar netting. All stainless-steel anchor-bolts lasted throughout the six-month trial period at both exposed and sheltered locations. Underwater epoxy lasted for three months at both locations, but 60% were lost within the first month at the exposed location (c.f. 30% losses at the sheltered location). However, all substrates attached using cyanoacrylate Seachem Reef Glue were lost at both locations within one month.
Chimeras were more robust to pressure from herbivores and demonstrated increased survival while creating similar chemical cues and habitat for biodiversity.
We are further refining our methods to generate chimeric plants with greater resilience to changes in water temperature so that the restoration of intertidal forests also considers future conditions such as climate change.
References
15 Anuario SERNAPESCA. 2019. Anuario Estadístico de Pesca. Ministerio de Economía Fomento y Reconstrucción, República de Chile. www.sernapesca.cl
16 Araujo F. & Faugueron S. 2016. Higher reproductive success for chimeras than solitary individuals in the kelp Lessonia spicata but no benefit for individual genotypes. Evol Ecol DOI 10.1007/s10682-016-9849-0.
17 Buschmann, A.H., S. Prescott, P. Potin, S. Faugeron, J. A. Vásquez, C. Camus, J. Infante, M. C. Hernández-González, A. Gutiérrez and D. A. Varela. (2014). The status of kelp exploitation and marine agronomy, with emphasis on Macrocystis p*y*rifera, in Chile. Adv. Bot. Res. 71: 161–188.
18 FAO. (2012). The state of world fisheries and agriculture. Rome.
19 González AV, Beltrán J, Hiriart-Bertrand L, Flores V, de Reviers B, Correa JA & Santelices B. 2012. Identification of cryptic species in the Lessonia nigrescens complex (Phaeophyceae, Laminariales). J. Phycol. 48:1153–1165.
20 González A.V., Borras-Chávez R., Beltrán J., Flores V., Vásquez J.A. & Santelices B. 2014. Morphological, ultrastructural, and genetic characterization of coalescence in the intertidal and shallow subtidal kelps Lessonia spicata and L. berteroana (Laminariales, Heterokonthophyta). J of Appl Phycol 26: 1107-1113.
21 González A.V. & Santelices B. 2016. Frequency of chimerism in natural populations of the kelp Lessonia spicata in Central Chile. PLoS One. 12(2):e0169182.
22 González AV. Tala F. Vásquez J. & Santelices B. 2020. Chimeric kelp: A methods to improve survival, growth and genetic diversity of seaweed cultivation and habitat restoration. 9th International Seaweed Conference SEAGRICULTURE 2020 (online version).
23 González AV (). Tala F. Vásquez J. & Santelices B. 2021. Using chimeric kelp production as Nature-based Solutions (NbS) for ecosystemic services restoration. 12th International Phycological Congress, 22-26 marzo (online version). () George Papenfuss award to the best lighting talk in the 12th International Phycological Congress in the category of applied phycology.
24 Parada G, Tellier F & Martínez EA. 2016. Spore dispersal in the intertidal kelp Lessonia spicata: macrochallenges for the harvested Lessonia species complex at microscales of space and time. Bot Mar: 59(4): 283–289.
25 Rodríguez D.C., Oróstica M.H. & Vásquez J.A. 2014. Coalescence in wild organisms of the intertidal population of Lessonia berteroana in northern Chile: Management and sustainability effects. J. Appl. Phycol 26: 1115-1122.
26 Servicio Nacional de Pesca y Acuicultura. 2019. FISCALIZACIÓN EN PESCA Y ACUICULTURA: INFORME DE ACTIVIDADES DEL 2018. Ministerio de Economía, Fomento y Turismo.
27 Vásquez, J.A., Zuñiga S., Tala F., Piaget N., Rodriguez D.C., and J.M.A. Vega. 2014. Economic evaluation of kelp forest in northern Chile: values of good and service of the ecosystem. J. Appl. Phycol. 26, 1081–1088.
Chimeric individuals of Lessonia spicata in the laboratory and installed in the field for intertidal restoration trials. Photos provided by the authors.
Details of holdfast from chimera. Photos provided by the authors.
Substrate with chimeras, one month after installation. Juveniles reached between 10-15 cm long. Photos provided by the authors.
Five months after installation, chimera formed an intertidal belt of juveniles (data obtained from FONDEF IDeA ID17I10080). Photos provided by the authors.
