Aquaculture Europe 2017

October 17 - 20, 2017

Dubrovnik, Croatia

HALOPHYTES FOR A SUSTAINABLE AQUACULTURE AND THE POTENTIAL OF THE SEA PURSLANE Halimione portulacoides

M. Custódio*1, S. Villasante2, R. Calado1 and A. Lillebø1
 
1Department of Biology & CESAM, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
2Faculty of Political Sciences, University of Santiago de Compostela, 15782 Santiago de Compostela, A Coruña, Spain
*E-mail: mfc@ua.pt

Introduction

Integrated Multi-Trophic Aquaculture (IMTA) systems have been endorsed by scientists as a sustainable solution to reduce the ecological impact of fish-farms (Troell et al. 2009; Granada et al. 2016). As EU aquaculture is mostly marine and coastal water-based, the implementation of IMTA requires salt-tolerant extractive species. While the use of seaweeds to remove dissolved inorganic nutrients is already well documented, the potential use of halophytes for the same purpose remains to be fully understood (Buhmann and Papenbrock 2013; Shpigel et al. 2013; Turcios and Papenbrock 2014; Buhmann et al. 2015). The present work contextualizes the importance of these salt-tolerant plants within an IMTA framework following a critical survey of peer-reviewed literature published to date; additionally, it elaborates on the particular potential of Halimione portulacoides as a bioremediator and valuable co-product, supported by its biological and ecological traits.

Material and Methods

Available scientific literature reporting the use of halophytes for remediation of marine aquaculture effluents was revised, with the potential use of H. portulacoides being highlighted through its biological, ecological and biochemical features (Figure 1).

Results

A total of 22 halophyte species (17 genera) were highlighted from the literature survey regarding their growth performance and nutrient (N and P) removal efficiency from aquaculture effluents. Plants-growth modules were either hydroponic-based or substrate-based, being supplied with effluents from either fin-fish or shrimp production, as well as solutions mimicking the nutrient load of such effluents. Trials were performed in desert, temperate and subtropical climates. Produced plant biomass can be valued for human consumption, as forage, as oil or extracts for pharmaceutical applications. Regarding nutrients removal, average N removal was 71(±26)% and average P removal was 63(±36)%. Concerning the use of H. portulacoides in IMTA, published studies addressed its physiology, phytoremediation, productivity, secondary metabolites production. Figure 2 synthesizes the main features supporting the potential use of this halophyte for IMTA.

Discussion and Conclusion

A growing number of halophytes are being investigated to be integrated in IMTA. Nonetheless, available results display a significant range of variability due to species-specific traits, systems design and lack of standardized research methods. To select the best halophytes for IMTA, variables such as salinity, macro- and micronutrients concentrations, light and hydraulic regimens and density must be tested and economic valuation studies performed. H. portulacoides is a potential candidate species that can cope with high levels of NaCl and multiple stress-inducing factors. It is widely distributed geographically, displays good productivity and N, P retentions. The presence of high levels of sulfated flavonoids and other bioactive molecules highlight its pharmaceutical potential, while its edible characteristics can diversify the sea vegetables market. However, little information is available relatively to its direct use as an aquaculture biofilter and future research is paramount. With the growing implementation of land-based marine IMTA, which presents a number of advantages over off-shore settings (Gunning et al. 2016), halophytes can be gradually introduced within this framework as an extractive species contributing to the greening of the Blue Revolution.

References

Buhmann A. and J. Papenbrock. 2013. Biofiltering of aquaculture effluents by halophytic plants: Basic principles, current uses and future perspectives. Environmental and Experimental Botany 92: 122-133.

Buhmann A., U. Waller, B. Wecker and J. Papenbrock. 2015. Optimization of culturing conditions and selection of species for the use of halophytes as biofilter for nutrient-rich saline water. Agriculture Water Management 149: 102-114.

Granada L., N. Sousa, S. Lopes and M.F.L. Lemos. 2016. Is integrated multitrophic aquaculture the solution to the sectors' major challenges? - a review. Reviews in Aquaculture 8: 283-300.

Gunning D., J. Maguire and G. Burnell. 2016. The development of sustainable saltwater-based food production systems:  a review of established and novel concepts. Water 8: 598.

Shpigel M., D. Ben-Ezra, L. Shauli, M. Sagi, V. Ventura, T.T. Samocha and J.J. Lee. 2013. Constructed wetland with Salicornia as a biofilter for mariculture effluents. Aquaculture 412-413: 52-63.

Troell M., A. Joyce, T. Chopin, A. Neori, A.H. Buschmann and J.G. Fang. 2009. Ecological engineering in aquaculture - Potential for integrated multi-trophic aquaculture (IMTA) in marine offshore systems. Aquaculture 297(1): 1-9.

Turcios A.E. and J. Papenbrock. 2014. Sustainable treatment of aquaculture effluents - What can we learn from the past for the future? Sustainability 6(2): 836-856.