Algal Bioremediation of Waste Waters from Land-Based Aquaculture Using Ulva: Selecting Target Species and Strains

Abstract

The optimised reduction of dissolved nutrient loads in aquaculture effluents through bioremediation requires selection of appropriate algal species and strains. The objective of the current study was to identify target species and strains from the macroalgal genus Ulva for bioremediation of land-based aquaculture facilities in Eastern Australia. We surveyed land-based aquaculture facilities and natural coastal environments across three geographic locations in Eastern Australia to determine which species of Ulva occur naturally in this region and conducted growth trials at three temperature treatments on a subset of samples from each location to determine whether local strains had superior performance under local environmental conditions. DNA barcoding using the markers ITS and tufA identified six species of Ulva, with U. ohnoi being the most common blade species and U. sp. 3 the most common filamentous species. Both species occurred at multiple land-based aquaculture facilities in Townsville and Brisbane and multiple strains of each species grew well in culture. Specific growth rates of U. ohnoi and U. sp. 3 were high (over 9% and 15% day−1 respectively) across temperature treatments. Within species, strains of U. ohnoi had higher growth in temperatures corresponding to local conditions, suggesting that strains may be locally adapted. However, across all temperature treatments Townsville strains had the highest growth rates (11.2–20.4% day−1) and Sydney strains had the lowest growth rates (2.5–8.3% day−1). We also found significant differences in growth between strains of U. ohnoi collected from the same geographic location, highlighting the potential to isolate and cultivate fast growing strains. In contrast, there was no clearly identifiable competitive strain of filamentous Ulva, with multiple species and strains having variable performance. The fast growth rates and broad geographical distribution of U. ohnoi make this an ideal species to target for bioremediation activities at land-based aquaculture facilities in Eastern Australia.

Environmental effects on growth and fatty acids in three isolates of Derbesia tenuissima (Bryopsidales, Chlorophyta)

“…Since the isolates were previously kept under identical culture conditions, it is likely that the observed variation in growth is due to genotypic differences between the isolates. Similar variation in growth between different isolates has been reported for the green seaweed Ulva ohnoi and the possibility of genotypic variation as the driver for this variation in growth was suggested for strains from different locations [30]. Further, natural selection for high growth and its heritability has been experimentally demonstrated in the brown seaweed Fucus vesiculosus [48].…”

“…While strain selection in species and subsequent crop improvements are common in terrestrial plants [25,26], and more recently in microalgae with substantial improvements in growth and the quantity and quality of fatty acids [17,22,27], this process is still in its infancy in seaweeds [24]. Strain selection and subsequent improvements in growth, temperature tolerance and the yield of iodine in the Chinese kelp industries have progressed since the 1960s [28], and there is strong support for a genetic component of basic morphological features [29] and growth rates [30] in seaweeds. A limited number of studies have also confirmed the genotypic variation and heritability of the natural products furanones [31] and phlorotannins [32] and the selective breeding of the brown seaweed Macrocystis has resulted in increases in total lipids and protein compared to natural populations [33].…”

Reproductive output and productivity of filamentous tropical Ulva over time

“…DNA barcoding was used to assign species names to samples from F 2 and F 3 of each collection (Lawton et al 2013;Carl et al 2014b) (see Supplementary Material; Online Resource 5). All samples were identified as Ulva sp.…”

“…The filamentous tropical species Ulva sp. 3, the focus of this study, meets these with a salinity tolerance ranging from freshwater (Shimada et al 2008) to saline (Lawton et al 2013) and high growth rates of up to 65 % day −1 across a wide range of temperatures (Lawton et al 2013;Carl et al 2014a). In addition, the life cycle of Ulva sp.…”

“…In these environments, green macroalgae, in particular filamentous species of the genus Ulva (formerly Enteromorpha; Hayden et al 2003), have desirable characteristics for year-round large-scale cultivation, including a broad tolerance of salinity and temperature with high growth rates (Moll and Deikman 1995;Luo and Liu 2011;Luo et al 2012;Lawton et al 2013;Carl et al 2014a). The filamentous tropical species Ulva sp.…”