Nanoflagellates of southern Tasmanian waters : taxonomy, toxicology and distribution
Creators: name: LeRoi, JM
Publisher: name: University Of Tasmania
Year: 2023

description: A taxonomic survey of scale-bearing nanoflagellate algae from southern Tasmanian coastal waters was undertaken. Observations were made on 52 samples collected from 21 different sites (June 1994 - 1995) and resulting enrichment cultures. Scale morphology was examined using transmission electron microscopy. Over 70 species of scale-bearing nanoflagellates from four classes and 17 genera were illustrated, namely: Chrysophyceae - Apedinella, Chrysolepidomonas, Meringosphaera, Paraphysomonas (8 spp); Prymnesiophyceae - Chrysochromulina (32 spp), Corymbellus, Imantonia, Pavlova, Phaeocystis (2 spp), Prymnesium (2 spp); Prasinophyceae - Dolichomastix (2 spp), Mamiella, Mantomiella, Pyramimonas (7 spp); Dinophyceae - Heterocapsa; and, of uncertain taxonomic affinities, Petasaria and Thaumatomastix (3 spp). Seventeen of the nanoflagellate species found were new records for Australian waters, specifically: Chrysochromulina acantha, C. ahrengotii, C. aff. brachycylindra, C. aff. camella, C. mactra, C. aff. scutellum, Pavlova pin guis, Chrysolepidomonas cf. marina, Paraphysomonas antarctica, P. bandaiensis, P. foraminfera, P. cf. takahashii, Dolichomastix nummulifera, D. aff. tenuilepis, Mamiella gilva, Petasaria heterolepsis and Thaumatomastix cf. thomseni. All species, except one (Chrysochromulina novae-zelandiae), are also known from the northern hemisphere. Two known toxic species, Chysochromulina polylepsis and C. leadbeateri, responsible for massive fish kills in Scandinavia, were found in this survey, as well as the known fish-killing species, Prymnesium patellife rum, observed from two important Tasmanian oyster-growing area, and subsequently cultured. The biodiversity of scale-bearing nanoflagellates in Tasmanian waters was highlighted by the large number of previously unreported scale types seen, including over 17 Chrysochromulina-like scale types, five prasinophyte box scale types and five Thaumatomastix-like scale types, but lack of complete cells prevented new species decriptions. However, sufficient material was available to fully characterise two new Chrysochromulina species. Full species descriptions will be prepared in the primary literature in the near future. The biodiversity of scale-bearing nanoflagellates in Tasmanian waters was highlighted by the large number of previously unreported scale types seen, including over 17 Chrysochromulina-like scale types, five prasinophyte box scale types and five Thaumatomastix-like scale types, but lack of complete cells prevented new species decriptions. However, sufficient material was available to fully characterise two new Chrysochromulina species. Full species descriptions will be prepared in the primary literature in the near future. Over 20 unialgal strains, with representatives from each observed class, were isolated from enrichment cultures and maintained; these included Chrysochromulina (8 strains), Pavlova (4 strains), Prymnesium (6 strains), Phaeocystis globosa, Pyramimonas grossii, Heterocapsa rotundata and Chrysolepidomonas cf. marina. Toxicity testing of 26 scale-bearing nanoflagellate strains was undertaken, using larval brine shrimp (Artemia) bioassays. Prymnesium patelliferum, was found to be toxic, with 100% mortality of Artemia nauplii after 24 hours exposure to stationary phase cultures, and toxicity of this species was enhanced when grown in phosphate-deplete media. Heterocapsa rotundata caused low percentage mortality (12.5%) of Artemia nauplii under the same bioassay conditions. This is a novel record of toxicity for this widespread dinoflagellate, and agrees with recent confirmation of toxicity to bivalves by the related species, H. circularisquama. None of the other nanoflagellate strains tested were found to be toxic. A potential new live food species for aquaculture, Pavlova pin guis, was identified using a combination of ultrastructural and morphological features. This species is now used in commercial Tasmanian oyster hatcheries as a valuable algal diet.