Effects of trichlorobenzene on natural phytoplankton populations

Natural phytoplankton assemblages from an offshore station in Lake Michigan were exposed to individual isomers of trichlorobenzene (TCB) and incubated in situ for a 24 h period. One set of exposures was initiated with a lake assemblage collected at 0330 h from 30 m and the TCB isomers added at 0400 h. The second exposure experiment was initiated with an assemblage from 30 m collected at 1530 h and the TCB isomers added at 1600 h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44445/1/10646_2004_Article_BF00368534.pd

Morphometric analysis of phosphate and chromium interactions in Cyclotella meneghiniana

Quantitative electron microscopy was used to evaluate interactive effects of chromium additions and phosphate nutrient status on the diatom Cyclotella meneghiniana. Cells of differing phosphate status were exposed to hexavalent chromium for 7 days and morphological changes in both phosphate alone and phosphate and chromium treatments were observed. Changes in chloroplast relative volume and number/volume were observed in all treatments. Changes in mitochondrial and vacuolar volume and an increase in presumed autophagic activity were apparent in all chromium treatments. An increase in polyphosphate was also found in most chromium treated cells. These morphological modifications are discussed in relation to changes observed with exposure to other heavy metals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28696/1/0000516.pd

Accumulation and cellular effects of heavy metals in benthic and planktonic algae

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24541/1/0000821.pd

Polyphosphate body formation and degradation in Plectonema boryanum (cynophyceae)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24121/1/0000378.pd

REJUVENATION OF MELOSIRA GRANULATA (BACILLARIOPHYCEAE) RESTING CELLS FROM THE ANOXIC SEDIMENTS OF DOUGLAS LAKE, MICHIGAN. I. LIGHT MIGROSCOPY AND 14 C UPTAKE 1

Resting cells of Melosira granulate (Ehr.) Ralfs were collected from the anoxic sediments of Douglas Lake, Michigan. Sediment containing M. granulata was inoculated into distilled water and incubated in a growth chamber for one week during which observations were made on the cytological differentiation process. Cells classified as “condensed,” i.e. containing a dark brown cytoplasmic mass were identified as resting cells. The differentiation process consisted of a series of gradual cytological changes that included elongation of the cytoplasmic mass and recognition of definable organelles to the point where the cells were non-distinguishable from water column vegetative cells. Differentiating cells accumulated large polyphosphate and lipid granules. However, these granules disappeared just prior to cell division. The complete differentiation or rejuvenation sequence occurred in some cells in less than 24 h. However, not all dormant cells rejuvenated at the same time and it was observed that the lag period for rejuvenation increased with resting cell age (depth of burial in sediments). In the 14 C uptake studies, label was initially observed in condensed state cells. The label gradually progressed to the more differentiated forms. Total carbon uptake during the rejuvenation process was initially lower in the rejuvenating cells, but roughly equal to water column populations after 8 h, indicating a period of high metabolic activity in the rejuvenating cells between 1 and 8 h.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66031/1/j.1529-8817.1986.tb02510.x.pd

Estim ation of intracellular carbon and silica content of diatoms from natural assemblages using morphometric techniques

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109990/1/lno19842961170.pd

Paraformaldehyde-glutaraldehyde as a routine phytoplankton fixative

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23663/1/0000631.pd

Effects of chlorinated benzenes on diatom fatty acid composition and quantitative morphology. III. 1,2,3-Trichlorobenzene

Cells of the diatom Cyclotella meneghiniana were exposed in a closed system to 0.245 ppm 1,2,3-trichlorobenzene. Response of the diatom was measured by quantitative ultrastructure and fatty acid percent composition over a 5-day period. During that time, 35 significant morphological and 12 fatty acid percent composition changes occurred. The most pronounced morphological change that occurred was a significant increase in lipid volume. In addition, changes were observed in vacuolar relative volume, suggesting that the tonoplast became more permeable. Fewer significant changes were observed in fatty acid percent composition upon exposure to this isomer. However, there was a consistent increase in oleic acid (C18∶1). The observed changes in morphological and fatty acid percent composition were uniformly distributed with time after the first hour of exposure. Results support the hypothesis that increased lipid stores may alter the timing of response to lipophilic toxicants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48071/1/244_2005_Article_BF01225003.pd

Examination of the surface microlayer of lake michigan using scanning electron microscopy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24119/1/0000376.pd

A morphometric analysis of algal response to low dose, short-term heavy metal exposure

Three algae, Melosira granulata, Fragilaria capucina , and Anacystis cyanea , collected as part of a natural phytoplankton assemblage were found to differ in their cytological responses to low dose short-term exposure to copper and lead. In general, all were more sensitive to copper than to lead. Fragilaria was more sensitive to both metals than the other species examined. Most immediate changes in relative volume categories can be ascribed to changes in vacuole volume that are most likely the result of changes in membrane permeability. There was some degree of accommodation in all three species at 24 hours. These results are discussed in view of the natural environment of the algae, as well as in relationship to previous studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41729/1/709_2005_Article_BF01281533.pd