The protozoa of a Western Australian hypersaline lagoon

Abstract

Hutt Lagoon, 28" 1 I'S, 1 14" 15'E, 600 km north of Perth, Western Australia and lying 5 m below sea level is the site of a pilot plant erected by Roche Algal Biotechnology for growing and harvesting the alga Dunaliella salina. The lagoon is filled to a depth of 50-75 cm by rainfall (18% w/v salinity or above) during the winter months and is desiccated to a 5 cm or more thick crust during the summer. Salt from the crust used to prepare a growth medium for D. salina introduced a number of protozoa to the cultures, some of which made great inroads on the algal population. Most of the protozoa in the crust are presumed to be in the form of cysts and originate from more or less permanent seeps and pools (>5% w/v salinity) resulting from the inflow of water from the Indian Ocean on the west and from continental ground water on the east. The salt of the crust is thus a mixture of athalassic and thalassic origin. Only the lower reaches of the seeps are inundated by the winter water rise.Fourteen ciliates, 10 zooflagellates and 4 sarcodines were observed frequently enough in brines of over 15% (w/v) salinity to identify. At least one parasite of D. salina is included in the flagellate group. Although no concerted effort with the phytoflagellates was made, the rarely seen species D. peircei, D. jacobae and Ochromonas cosmopolitus were noted, as well as a Gymnodinium sp. The ciliates include the bacteriophagous Trachelocerca conifer, Metacystis truncata, Chilophrya utahensis, Rhopalophrya salina, Uronema marinum, Condylostoma sp. and Palmarella salina. Those eating both bacteria and algae were Nassula sp., Fabrea salina, Blepharisma halophila, Cladotricha sigmoidea, and Euplotes sp. Ciliates feeding on other ciliates include Podophrya sp. and Trematosoma bocqueti. Among the zooflagellates were several species of Monosiga, Rhynchomonas nasuta, Phyllomitus sp., Tetramitus salinus, T. cosmopolitus, Bodo caudatus, B. edax and 3 other distinctive Bodo species, one being parasitic on D. salina. All of the sarcodina fed on both algae and bacteria, except for the smallest amoeba (4 pm diameter rounded) which did not feed on algae, and included Heteramoeba sp. with both flagellate and amoeboid phases, an orange amoeba, an orange filopodforming organism and a colorless filopod-forming organism, the last three of unknown genus.The relationship of these protozoa to the lagoon and to D. salina culturing is discussed.

Active flagellates grazing on prokaryotes in high salinity waters of a solar saltern

“…This disparity does not seem to be due to methodological problems because previous studies as well as ours used standard methods for measuring protozoan grazing rates. Considering that 4 species of prokaryotic feeding zooflagellates were also observed in a Western Australian hypersaline lagoon (Post et al 1983), in all likelihood species of HNF might be different between our study site and those in Spain. In support of our idea, eukaryal assemblages were recently reported to be more diverse in high salinity waters than previously thought (Casamayor et al 2002).…”

“…and Bodo sp. observed in a Western Australian hypersaline lagoon (Post et al 1983). To independently confirm the observation of active grazing in high salinity waters, total grazing experiments by observing disappearance of FLP were also subsequently carried out.…”

“…However, in high salinity waters in a Western Australian hypersaline lagoon, 4 zooflagellates were observed frequently enough to be identified and appeared to be prokaryotic feeders (Post et al 1983). Presumably, high salinity waters from geographically different areas would have different species compositions of HNF.…”

Distribution of phytoplankton and artemia in the solar salterns at Tuticorin

“…Phytoplankton samples were collected by filtering 100 litres of water through a plankton net having a mesh size of 10µm (Hecky and Kilham, 1973;post et al, 1983;Robert andPeter, 1973, Wongrat, 1986) The Phytoplanktons were analysed under a microscope and their identifications were noted. The planktons belonging to family Bacillariophyceae, Chlorophyceae, Cyanophyceae, Erythophyceae and Rhodophyceae were identified.…”

Assessing the potential of polyculture to accelerate algal biofuel production

“…State-of-the-art approaches include chemical interventions that either selectively kills grazers/pathogens or otherwise provides a selective advantage for the algal crop (i.e., pesticide application) [17,192,194]; periodic modulation of chemical conditions in the algal cultivation system filtration (e.g., pH reduction and NH 3 addition) [192,195]; early detection of grazers and other contaminants to time harvest cycles, thereby limiting grazer effects on productivity [128,196]; application of continuous strong selective conditions to limit the growth and viability of unwanted competitors (e.g., hypersaline conditions) [197]; and genetic modification of the algal cultivar to change protein expression, thereby altering palatability of the algal cell [198]. While each of these approaches can reduce the number and impact of grazers, they can also represent unique regulatory or economic hurdles and limit the diversity of the algal strains compatible with each control mechanism.…”