Geology topics

Roann E. Ogawa

Publications and source records attributed to Roann E. Ogawa.

3 recordsLinked to original sources

USGS2003

The influence of nitrogen on heterocyst production in blue-green algae

A series of experiments on heterocyst production in Anabaena variabilis provides some strong indirect evidence for the role of heterocysts in nitrogen fixation. Of the algae tested ( Anabaena variabilis, A. inaequalis, A. cylindrica, A. flos-aquae, Tolypothrix distorta, Gloeotrichia echinulata, Aphanizomenon flos-aquae, Oscillatoria sp. , and Microcystis aeruginosa ), only those with heterocysts grew in a nitrate-free medium. Growth in the nitrate-free medium was accompanied by an increase in heterocysts. Heterocyst formation in A . variabilis was evident 24 hr after transfer from a nitrate-containing to a nitrate-free medium. The number of heterocysts was altered by changes in the nitrogen source. Numbers were lowest when NH 4 -N was used as a nitrogen source and highest when nitrogen (N 2 -N) was derived from the atmosphere. Heterocyst numbers could also be regulated by controlling the concentration of NO 3 -N in the medium. Heterocyst production depended on the absence of combined nitrogen and the presence of phosphate. Data are presented on the occurrence of blue-green algae (with heterocysts) in Lake Erie and the environmental conditions apparently necessary for them to become dominant.

Limnology and Oceanography↗

USGS1992

Trace elements in lake sediment, macrozoobenthos, and fish near a coal ash disposal basin

Samples of lake sediment, macrozoobenthos, and fish were collected during 1983 and 1984 near a coal ash disposal basin situated on the western shoreline of Lake Erie. Neutron activation analysis was used to determine if potentially toxic trace elements were present in higher concentrations at stations near the basin than at reference stations a few kilometers away. Of the 29 trace elements examined, arsenic and cobalt were significantly ( p <0.05) more concentrated in sediment nearest the coal ash basin except in spring, when little or no difference was detected. Arsenic and bromine were significantly higher in oligochaetes, and selenium was significantly higher in both oligochaetes and chironomids taken from proximal stations than in those taken from reference stations. Selenium, bromine, cobalt, nickel, and chromium were higher in young-of-the-year brown bullheads taken nearer the disposal basin in fall 1983. Selenium was higher in adult spottail shiners taken at the proximal station in spring 1984, and bromine was higher in yearling white bass from the proximal station in fall 1983 and 1984. None of the trace elements was higher in adult yellow perch or adult brown bullheads at any time. Fewer spottail shiners and yearling white bass were caught close to the disposal basin than far away, which may indicate avoidance by these fish of increased concentrations of trace elements contained within the ash effluent.

Journal of Freshwater Ecology↗

USGS1969

Lake Ontario phytoplankton, September 1964

Phytoplankton counts on samples collected in Lake Ontario on September 8-18, 1964, showed that green algae were the dominant plankters and diatoms were of secondary importance. The greatest abundance of phytoplankton was close to shore from Toronto, along the southern shore of the lake, and up the eastern shore to the North Channel. The open waters of Lake Ontario were characterized by low numbers of phytoplankton. The relationships among phytoplankton abundance, bottom fauna distribution, and enrichment are discussed.

Technical Report↗