Bacterioplankton Density and Activity in Benthic Nepheloid Layers of Lake Michigan and Lake Superior

1991 ◽  
Vol 48 (5) ◽  
pp. 923-932 ◽  
Author(s):  
Randall E. Hicks ◽  
Christopher J. Owen
Keyword(s):  
Lake Michigan ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Lake Superior ◽  
Field Measurements ◽  
Depth Interval ◽  
Nepheloid Layer ◽  
Dividing Cells ◽  
Doubling Times ◽  
Benthic Nepheloid Layer

Benthic nepheloid layers were observed in Lake Michigan and Lake Superior during July 1988 using the Johnson-Sea-Link II submersible. A particularly well-defined benthic nepheloid layer was present in Whitefish Bay, Lake Superior, where particle concentrations increased 10 times over the bottom 30 m. Bacterial abundance, however, increased only 1.5 times in the same depth interval and a maximum of only 16% 1 m above the sediment in both lakes when the sediment boundary layer was deliberately resuspended. Bacterial abundance was greater in Lake Michigan than in Lake Superior. Bacterioplankton abundance and the frequency of dividing cells were both related to temperature and organic carbon concentrations. The range of individual cell volumes (0.024–0.042 μm3) was similar in both lakes, regardless of depth. Less than 5% of the heterotrophic bacteria were actively dividing and only 2.0–3.4% of the bacterioplankton in the epilimnion and hypolimnion were synthetically active in both lakes. Bacterioplankton doubling times, estimated from field measurements of the frequency of dividing cells, increased from 29 h at 5 m to > 230 h at 310 m in the Caribou Basin of Lake Superior. The abundance, cell size, and activity of heterotrophic bacterioplankton in the deep hypolimnia of Lake Michigan and Lake Superior were unaffected by the presence of a benthic nepheloid layer.

scholarly journals Carbon fluxes through bacterial communities on glacier surfaces

2010 ◽  
Vol 51 (56) ◽  
pp. 32-40 ◽  
Author(s):  
Alexandre M. Anesio ◽  
Birgit Sattler ◽  
Christine Foreman ◽  
Jon Telling ◽  
Andy Hodson ◽  
...  
Keyword(s):  
Bacterial Community ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Community Respiration ◽  
Organic C ◽  
C Cycle ◽  
Cryoconite Hole ◽  
Eukaryotic Organisms ◽  
Doubling Times

AbstractThere is very little information about the activity of microbial communities on the surface of glaciers, though there is an increasing body of evidence to show that they strongly influence the biogeochemistry of these habitats. We measured bacterial abundance and production in cryoconite holes on Arctic, Antarctic and Alpine glaciers in order to estimate the role of heterotrophic bacteria within the carbon budget of glacial ecosystems. Our results demonstrate an active bacterial community on the surface of glaciers with doubling times that vary from a few hours to hundreds of days depending on the glacier and position (water or sediments) within the cryoconite hole. However, bacterial production is only ∼2–3% of the published literature values of community respiration from similar habitats, indicating that other types of microbes (e.g. eukaryotic organisms) may also play a role in the C cycle of glaciers. We estimate that only up to 7% of the organic C in cryoconite sediments is utilized by the heterotrophic bacterial community annually, suggesting that the surface of glaciers can accumulate organic carbon, and that this C may be important for biogeochemical activity downstream to adjacent ecosystems.

Chlorinated hydrocarbon cycling in the benthic nepheloid layer of Lake Superior

1985 ◽  
Vol 19 (9) ◽  
pp. 854-861 ◽  
Author(s):  
Joel E. Qaker ◽  
Steven J. Eisenreich ◽  
Thomas C. Johnson ◽  
Barbara M. Halfman
Keyword(s):  
Lake Superior ◽  
Nepheloid Layer ◽  
Chlorinated Hydrocarbon ◽  
Benthic Nepheloid Layer

scholarly journals Fe and C co-limitation of heterotrophic bacteria in the naturally fertilized region off the Kerguelen Islands

2015 ◽  
Vol 12 (6) ◽  
pp. 1983-1992 ◽  
Author(s):  
I. Obernosterer ◽  
M. Fourquez ◽  
S. Blain
Keyword(s):  
Trace Metal ◽  
Bacterial Production ◽  
Bacterial Abundance ◽  
Heterotrophic Bacteria ◽  
Kerguelen Islands ◽  
High Nutrient ◽  
Limiting Nutrient ◽  
Heterotrophic Metabolism ◽  
Heterotrophic Production

Abstract. It has been univocally shown that iron (Fe) is the primary limiting nutrient for phytoplankton metabolism in high-nutrient, low-chlorophyll (HNLC) waters, yet the question of how this trace metal affects heterotrophic microbial activity is far less understood. We investigated the role of Fe for bacterial heterotrophic production and growth at three contrasting sites in the naturally Fe-fertilized region east of the Kerguelen Islands and at one site in HNLC waters during the KEOPS2 (Kerguelen Ocean and Plateau Compared Study 2) cruise in spring 2011. We performed dark incubations of natural microbial communities amended either with iron (Fe, as FeCl3) or carbon (C, as trace-metal clean glucose), or a combination of both, and followed bacterial abundance and heterotrophic production for up to 7 days. Our results show that single and combined additions of Fe and C stimulated bulk and cell-specific bacterial production at the Fe-fertilized sites, while in HNLC waters only combined additions resulted in significant increases in these parameters. Bacterial abundance was enhanced in two out of the three experiments performed in Fe-fertilized waters but did not respond to Fe or C additions in HNLC waters. Our results provide evidence that both Fe and C are present at limiting concentrations for bacterial heterotrophic activity in the naturally fertilized region off the Kerguelen Islands in spring, while bacteria were co-limited by these elements in HNLC waters. These results shed new light on the role of Fe in bacterial heterotrophic metabolism in regions of the Southern Ocean that receive variable Fe inputs.

Paleohydrology of the upper Laurentian Great Lakes from the late glacial to early Holocene

2009 ◽  
Vol 71 (3) ◽  
pp. 397-408 ◽  
Author(s):  
Andy Breckenridge ◽  
Thomas C. Johnson
Keyword(s):  
Great Lakes ◽  
Lake Michigan ◽  
Lake Superior ◽  
Late Glacial ◽  
Lake Huron ◽  
Michigan Basin ◽  
Great Lakes Basin ◽  
Lake Agassiz ◽  
Sharp Drop ◽  
Freshwater Fluxes

AbstractBetween 10,500 and 9000 cal yr BP, δ18O values of benthic ostracodes within glaciolacustrine varves from Lake Superior range from − 18 to − 22‰ PDB. In contrast, coeval ostracode and bivalve records from the Lake Huron and Lake Michigan basins are characterized by extreme δ18O variations, ranging from values that reflect a source that is primarily glacial (∼ − 20‰ PDB) to much higher values characteristic of a regional meteoric source (∼ − 5‰ PDB). Re-evaluated age models for the Huron and Michigan records yield a more consistent δ18O stratigraphy. The striking feature of these records is a sharp drop in δ18O values between 9400 and 9000 cal yr BP. In the Huron basin, this low δ18O excursion was ascribed to the late Stanley lowstand, and in the Lake Michigan basin to Lake Agassiz flooding. Catastrophic flooding from Lake Agassiz is likely, but a second possibility is that the low δ18O excursion records the switching of overflow from the Lake Superior basin from an undocumented northern outlet back into the Great Lakes basin. Quantifying freshwater fluxes for this system remains difficult because the benthic ostracodes in the glaciolacustrine varves of Lake Superior and Lake Agassiz may not record the average δ18O value of surface water.

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