Extensive Variations in Diurnal Growth Patterns and Metabolism Among Ulva spp. Strains

Abstract

Green macroalgae of the genus Ulva play a key role in coastal ecosystems and are of increasing commercial importance. However, physiological differences between strains and species have yet to be described in detail. Furthermore, the strains of Ulva used in aquaculture usually originate from opportunistic collection in the wild without prior selection of best performing strains. Hence, efforts are required to detect the potential variability in growth and metabolic accumulation between Ulva strains and ultimately select the best performing strains under given environmental conditions. Here, the growth, physiological, and metabolic characteristics of 49 laminar Ulva spp. strains were investigated using a custom-made high-throughput phenotyping platform, enzymatic assays, and gas chromatography-mass spectrometry. We found large natural variation for a wide range of growth and metabolic characteristics, with growth rates varying from 0.09 to 0.37 mg.mg 21 .d 21 among strains. Ulva spp. possess a unique diurnal growth pattern and primary metabolism compared with land plants, with higher growth rates during the night than during the light period. Starch and sucrose only contributed on average 35% of the carbon required to sustain Ulva's night growth. Nitrates accumulated during the night in Ulva tissues, and nitrate accumulation and consumption was positively correlated with growth. In addition, we identified six amino acids as possible biomarkers for high growth in Ulva. The large variability in growth and metabolite accumulation recorded among morphologically similar Ulva strains justifies future efforts in strain selection for increasing biomass, metabolite yields, and nutrient removal in the growing aquaculture industry.

Foliose Ulva Species Show Considerable Inter‐Specific Genetic Diversity, Low Intra‐Specific Genetic Variation, and the Rare Occurrence of Inter‐Specific Hybrids in the Wild

“…Given the limited cytoplasmic genetic variation, we expect that the large growth and metabolic differences between Ulva individuals from the same species (Fort et al. 2019) is probably largely explained by variation in the nuclear genome. Our strategy did not allow for precise characterization of nuclear genome diversity due to limited coverage and high abundances of bacterial DNA.…”

“…High levels of genetic variation among foliose Ulva strains are associated with large differences in biomass production (Fort et al. 2019, 2020). Such genetic variation presents foliose Ulva as an attractive target for genomic improvement.…”

Site-Specific Lipidomic Signatures of Sea Lettuce (Ulva spp., Chlorophyta) Hold the Potential to Trace Their Geographic Origin

“…Today, most of the land-based aquaculture operations of Ulva spp. is done by clonal propagation of multiple strains, normally collected in the vicinity of farming sites [15]. Species and/or strains selection of Ulva spp.…”

Analysis of algal growth- and morphogenesis- promoting factors in an integrated multi-trophic aquaculture system for farming Ulva spp.

“…Although the favourable growth response to NH 4 + as the N source was shown in several studies, Fort et al (2019) recently reported that NO 3 − accumulation and consumption was positively correlated with Ulva spp. growth, with higher growth rates during the night than during light periods (Fort et al 2019). In the future, therefore, studies with a greater temporal resolution will be necessary to monitor the dynamics of N consumption in aquaculture.…”

“…Ale et al (2011) reported a favourable growth response to NH 4 + relative to other N sources by monitoring the growth kinetics of U. lactuca (Ale et al 2011). Although the favourable growth response to NH 4 + as the N source was shown in several studies, Fort et al (2019) recently reported that NO 3 − accumulation and consumption was positively correlated with Ulva spp. growth, with higher growth rates during the night than during light periods (Fort et al 2019).…”