P.A. Tyler

Phytoflagellates and their ecology in Tasmanian polyhumic lakes

Tasmania has many polyhumic lakes with a wealth of phytoflagellates, especially chromophytes. Dystrophic coastal lagoons, such as Lake Garcia, are rich habitats of the Chrysophyta and Dinophyta, containing a number of new or rare species. In meromictic Lake Fidler and Sulphide Pool flagellates and prokaryotes are permanently zoned in a finely structured array astride the redoxcline. In the mixolimnetic waters phytoflagellates are zoned and probably perform regular migrations. Chaoborus larvae migrate daily. In monomictic, polyhumic Lake Chisholm there is probably a permanent zonation of flagellates and prokaryotes about the long-lasting thermocline, with diel migrations of other species in the epilimnion. With its numerous new or rare species Tasmania is a phytoflagellate haven.

Mallomonas sabulosa (Chrysophyceae), a new species from Australia

A new member of the Chrysophyceae, Mallomonas plumosa, is described from two lakes in Tasmania, Australia. The distinctive feature of the organism is an array of plume-bristles which radiate from a whorl of apical scales.

Mallomonopsis tasmanica sp. nov. (Chrysophyceae) and Mallomonopsis elliptica Matvienko from Australia

A member of the Chrysophyceae, Mallomonopsis tasmanica, is described from a dystrophic, meromictic lake in Tasmania as a new species. It is recognized by possession of two flagella, scale morphology and bristle type. It is a strong swimmer and during the day apparently occupies a discrete stratum in the water column. The occurrence of Mallomonopsis elliptica Matvienko is reported from tropical Australia. In both species bristle morphology varies considerably.

On the nature of eclectic species—a tiered approach to genetic compatibility in the desmid Micrasterias thomasiana

The applicability of the concept of the biological species to the Desmidiaceae is investigated by interbreeding trials between sympatric and allopatric populations of the ubiquitous morphospecies Micrasterias thomasiana. A four-tiered system of testing is adopted, in which the degree of genetic relationship between strains is progressively adduced by the relative success in each of the series of tests, culminating in F1 interfertility and gene flow in backcrossing of F1 offspring to parental clones. The results indicate that sexual compatibility is more complex than simple heterothallism, and involves relative sexuality and probably a system akin to a gene complex with polygenic modifiers. The probable existence of syngens, or biological species, within the morphospecies is acknowledged, one of which has a considerable measure of intercontinental genetic compatibility within morphological boundaries consistent with the nomenclatural species but distinct from closely similar taxa. For an operational taxono...

Thecadiniopsis tasmanica gen. et sp. nov. (Dinophyta: Thecadiniaceae) from Tasmanian freshwaters

A new genus of planktonic peridinioid dinoflagellates is described from Tasmanian coastal lagoons and dystrophic freshwater lakes. In the possession of a single antapical, and two large lateral plates, its hypotheca resembles that of the bilaterally flattened, marine, sanddwelling genus Thecadinium Kofoid et Skogsberg. The new genus Thecadiniopsis is distinct in having an ovoid cell-shape, a left-handedly displaced girdle, and a prominent asymmetric epitheca with complex plate configuration. The plate tabulation of Thecadiniopsis tasmanica gen. et sp. nov. [P0, 4′, 1a. 4″, 5c, 5(?)s, 5‴, 1⁗] is illustrated by scanning electron micrographs of whole cells and of plates separated by hypochlorite treatment.

A family of pneumatically-operated thin layer samplers for replicate sampling of heterogeneous water columns

A series of inexpensive, pneumatic thin layer water samplers is described. They can be operated from small boats, and permit sampling at 2.5 cm intervals with little or no disturbance of stratified systems such as oxyclines or redoxclines of meromictic lakes, or microstratification of flagellates in sheltered epilimnia. Some models permit replicate sampling at closely-spaced intervals in a two-dimensional array. Their performance abilities are illustrated with examples of microstratification.

Mallomonas morrisonensis (Chrysophyceae) a new species from Australia

A new member of the Chrysophyceae, Mallomonas morrisonensis, is described from two lakes in Tasmania, Australia. The organism has scales of the tripartite type, and is distinctive in having twin finger-like projections on the most posterior scales. The species is named after Lake Morrison in which it was first discovered.

Taxonomy of Australian freshwater algae. I. The genus Micrasterias in South-Eastern Australia

A preliminary survey has been made of the desmid genus Micrasterias in Tasmania, as the first part of an intended series of detailed investigations of Tasmanian freshwater algae. For comparative purposes, samples from the south-eastern states of mainland Australia are included. Micrasterias hardyi West, apparently an Australian endemic, is discussed in detail and M. tropica var. indivisa (Nordst.) Eichl. et Racib., formerly known only from New Zealand, is figured from Tasmania. Some other Micrasterias forms are readily accommodated within the existing nomenclature. Others, however, have been uncertainly allied with existing taxa in keeping with a policy of not adding to the burden of nomenclature until a biological concept of species has been developed for the desmids. The taxonomy of Australian representatives of the genus Micrasterias is discussed against this background.

Tessellaria volvocina rediscovered

Tessellaria volvocina, a rare colonial chrysomonad, has been rediscovered in Australia after 70 years. It is much as originally described but modern microscopical methods have shown the putative mucilaginous colonial investment to be a multilayered covering of siliceous scales. This differs from the scale-case of Synura and other scaled colonial chrysophytes in that the entire colony, not individual cells, is clothed by the scales. Initial evidence points to a position within the Synurophyceae and possibly a relationship with Synura lapponica. It has a continental but disjunct distribution in Australia.

Primary productivity and trophic status of Lakes Sorell and Crescent, Tasmania

The primary productivity of two turbid, shallow lakes on the Tasmanian Central Plateau was determined by the C14 technique from half-light day incubations in situ. Graphical integration of depth-rate curves gave estimates of areal day rates of production and of annual rates.The 2 lakes are closely adjacent and very similar physically and chemically, but have very different phytoplankton populations. Lake Crescent has ten times the standing crop biomass of Lake Sorell but its greater turbidity restricts light penetration, and production per unit of surface per day and per year is only 2.6 times that of Sorell.With day rates of 25-(44)-93 mgCm−2 and annual production of 16.9 gCm−2 Lake Sorell could be regarded as oligotrophic. Consideration of standing crop biomass and morphometry however indicates oligo-mesotrophy. Lake Crescent with day rates of 35-(115)-250 mgCm−2 and annual production of 45 gCm−2 is moderately eutrophic.Incubations in constant light demonstrated considerable variation in production rates in different parts of Lake Crescent.