LED Lighting and High-Density Planting Enhance the Cost-Efficiency of Halimione Portulacoides Extraction Units for Integrated Aquaculture

Halophytes are salt-tolerant plants that can be used to extract dissolved inorganic nutrients from saline aquaculture effluents under a production framework commonly known as Integrated Multi-Trophic Aquaculture (IMTA). Halimione portulacoides (L.) Aellen (common name: sea purslane) is an edible saltmarsh halophyte traditionally consumed by humans living near coastal wetlands and is considered a promising extractive species for IMTA. To better understand its potential for IMTA applications, the present study investigates how artificial lighting and plant density affect its productivity and capacity to extract nitrogen and phosphorous in hydroponic conditions that mimic aquaculture effluents. Plant growth was unaffected by the type of artificial lighting employed—white fluorescent lights vs. blue-white LEDs—but LED systems were more energy-efficient, with a 17% reduction in light energy costs. Considering planting density, high-density units of 220 plants m−2 produced more biomass per unit of area (54.0–56.6 g m−2 day−1) than did low-density units (110 plants m−2; 34.4–37.1 g m−2 day−1) and extracted more dissolved inorganic nitrogen and phosphorus. Overall, H. portulacoides can be easily cultivated hydroponically using nutrient-rich saline effluents, where LEDs can be employed as an alternative to fluorescent lighting and high-density planting can promote higher yields and extraction efficienciesThe authors thank the Portuguese Foundation for Science and Technology (FCT) for the financial support to Marco Custódio (PD/BD/127990/2016), Paulo Cartaxana (CEECIND/01434/2018) and CESAM (UIDB/50017/2020+UIDP/50017/2020). This work was also supported by the Integrated Program of SR&TD “Smart Valorization of Endogenous Marine Biological Resources Under a Changing Climate” (reference Centro-01-0145-FEDER-000018), co-funded by Centro 2020 program, Portugal 2020 and European Union, through the European Regional Development Fund, and by the project “AquaMMIn—Development and validation of a modular integrated multitrophic aquaculture system for marine and brackish water species” (MAR-02.01.01-FEAMP-0038) co-funded by Portugal 2020 and the European Union through Mar 2020, the Operational Programme (OP) for the European Maritime and Fisheries Fund (EMFF) in PortugalS