Fast screening method to identify salinity tolerant strains of foliose Ulva species. Low salinity leads to increased organic matter of the biomass.

Sea lettuce (Ulva) is recognised for its potential in food, pharmaceutical, nutraceutical, biorefinery and bioremediation industries and is increasingly being cultivated. The requirements of those industries vary widely in terms of biomass composition. Ulva biomass composition and growth is known to be directly influenced by environmental factors, e.g., temperature, light, salinity, nutrient availability as well as by genetic factors and likely by microbiome composition. In order to select for the highest yielding strains in a given environment, we tested the suitability of common-garden experiments, i.e., the co-cultivation of different strains grown under shared conditions. Fifteen strains from six different foliose Ulva species were grown together under two different salinities, 35 ppt and 15 ppt. After 32 days, only U. australis strains remained at both salinities. If selection at low salinity was mostly based on survival, the selection process at seawater salinity was driven by competition, largely based on growth performance. Growth rates after a month were very similar at both salinities, suggesting the U. australis strains cope equally well in either condition. However, the composition of the biomass produced in both environments varied, with the content of all organic compounds being higher at low salinity, and the ash content being reduced in average by 66%. To summarize, this study provides an established bulk-selection protocol for efficiently screening large numbers of locally-sourced strains and highlights the potential of low salinity treatments for increased organic matter content, particularly in carbohydrates. Supplementary Information: The online version contains supplementary material available at 10.1007/s10811-024-03222-0.

Selenite (IV) and selenate (VI) uptake and accumulation capacity of Lemna minor L. from an aquatic medium.

The uptake of sodium selenite (Se(IV)) and sodium selenate (Se(VI)) from aqueous medium by Lemna minor L. and the influence of different Se concentrations on its growth, morphological and ultrastructural characteristics were studied. L. minor was grown at different concentrations (1, 3, 5 and 10 mg L-1) of Se(IV) and Se(IV). The Se(IV) concentration in the plant tissue ranged between 77.7 (± 4.3) to 453 (± 0) mg kg-1 DW. The Se(VI) concentration in plant tissues ranged between 117 (± 11) to 417 (± 2) mg kg-1 DW. The highest bioconcentration factor for Se(VI) was 127 (± 7) at 3 mg/L, with a Se removal efficiency of 44%. For Se(IV), the highest bioconcentration factor was 77.7 (± 4.3) at 1 mg L-1, which had a Se removal efficiency of 23%. Growth of L. minor was suppressed at 10 mg L-1 Se in both forms. The addition of Se promoted the formation of starch granules in L. minor which occupied a chloroplast area of 74% for Se(IV) and 77% for Se(VI). The efficient uptake of both Se forms by L. minor indicates the potential application of this species for phytoremediation of Se laden wastewaters and its use as an alternative feedstock in biofuel production.