Resolving the identity of commercially cultivated Ulva (Ulvaceae, Chlorophyta) in integrated seaweed‐abalone aquaculture farms in South Africa

Abstract

Species of Ulva have a wide range of commercial applications and are increasingly being recognized as promising candidates for integrated aquaculture. In South Africa, Ulva has been commercially cultivated in integrated seaweed‐abalone aquaculture farms since 2002, with more than 2000 tonnes of biomass cultivated per annum in land‐based paddle raceways. However, the identity of the species of Ulva grown on these farms remains uncertain. We therefore characterized samples of Ulva cultivated in five integrated multi‐trophic aquaculture farms (IMTA) across a wide geographical range and compared them with foliose Ulva specimens from neighboring seashores. The molecular markers employed for this study were the chloroplast‐encoded Ribulose‐1,5‐bisphosphate carboxylase oxygenase (rbcL), the Internal Transcribed Spacer (ITS) of the nuclear, and the chloroplast elongation factor tufA. All currently cultivated specimens of Ulva were molecularly resolved as a single species, U. lacinulata. The same species has been cultivated for over a decade, although a few specimens of two other species were also present in early South African IMTA systems. The name Ulva uncialis is adopted for the Ulva “Species A” by Fort et al. (2021), Molecular Ecology Resources, 22, 86) significantly extending the distribution range for this species. A comparison with wild Ulva on seashores close to the farms resulted in five new distribution records for South Africa (U. lacinulata, U. ohnoi, U. australis, U. stenophylloides, and U. aragoënsis), the first report of a foliose form of U. compressa in the region, and one new distribution record for Namibia (U. australis). This study reiterates the need for DNA confirmation, especially when identifying morphologically simple macroalgae with potential commercial applications.

Morphological and Molecular Identification of Ulva spp. (Ulvophyceae; Chlorophyta) from Algarrobo Bay, Chile: Understanding the Composition of Green Tides

“…The authors postulate that the material identified as "U. rigida" in GenBank from other seas, including those of Chile, is erroneously classified and would instead belong to U. lacinulata (Kutzing) Wittrock. On the other hand, Ulva stenophylloides has been previously described and reported for Victoria, Australia [32]; New Zealand [68]; and South Africa [48]. Hence, our contribution would be the first record of U. stenophylloides in Chile, as well as in the case of U. uncialis and U. aragoensis.…”

“…This species has only been previously recorded from Australia, New Zealand, and South Africa [27,48]; therefore, this is the first record for Chile.…”

“…Sequences referred to as Ulva sp. A in [36] were considered as U. uncialis [48]. Species names and associated sequences that are synonyms were not included in the analysis even when blast searches closely matched them.…”