Seaweed cultivation due to the demand for its products is rapidly increasing worldwide . Ocean and coastal seaweed farming practices in Australia are limited by cost, potential environmental impact, and legislation. Land-based cultivation using Inland Saline Water (ISW) presents a pathway for the use of degraded land to yield commercially viable products in Western Australia. ISW is known to have significantly different ionic ratios than ocean water (OW), specifically Na:K and Mg:Ca, and its capacity to grow across a range of ionic profiles is not yet well understood.
This study tested growth of Chlorophyta Chaetomorpha linum cultured in different ionic profiles created by mixture of ISW with Ocean Water, over two experiments. In the first experiment, C. linum was grown across a broad range of ionic profile mixtures including OW100ISW0, OW66ISW33, OW33ISW66, OW0ISW100 (subscript represents the percentage of water mix). In the second experiment, C. linum was grown across a more specific range of ionic profile mixtures including OW33ISW 66, OW22ISW77, OW11ISW88, OW0ISW 100. Sixteen tanks with four replicates per ionic profile, were randomly organised outdoors under direct sunlight. Water salinity was maintained at 25 ppt for the duration of experiments by adding dechlorinated freshwater. A water bath was used to stabilise the water temperature in tanks, and moderate aeration was provided to all tanks . Agilent microwave plasma atomic emission spectrometry (MP-AES), Ion Chromatography (IC) and Total Organic Carbon (TOC) were conducted on all water profiles. Seaweed growth was recorded every three days by weighing st rained wet biomass on a scale.
C. linum specific growth rate (SGR) over 15 days in OW0ISW 100 ( 2.73 ± 0.35 % day-1) and OW33ISW66 (2.65 ± 0.49 day-1) was significantly higher (p < 0.05) than in OW66ISW33 (0.94 ± 0.49 % day-1) in EXP 1 . No significant difference in growth was observed in EXP 2 between treatments, however, SGR of OW33ISW66 , OW22ISW77 and OW11ISW88 water profiles was significantly higher on Day 15 than on Day 0 . The high initial growth rate (T1 – T2) in EXP 1 followed by a plateau and overall lower growth rates in EXP 2 was likely caused by a shortage of nitrogen-based nutrients. Further experiments should investigate the growth of C. linum in OW0ISW 100 supplemented with nutrients and with variable initial starting biomass. This study demonstrates the potential for the cultivation of C. linum in ISW, presenting a pathway for dryland affected salinity-affected farmers to diversify their income and utilise otherwise barren land through ISW aquaculture.