Dynamics of Lake Michigan Phytoplankton: Recent Changes in Surface and Deep Communities

1987 ◽  
Vol 44 (3) ◽  
pp. 509-514 ◽  
Author(s):  
Gary L. Fahnenstiel ◽  
Donald Scavia
Keyword(s):  
Water Column ◽  
Green Algae ◽  
Thermal Stratification ◽  
Lake Michigan ◽  
Nutrient Supply ◽  
Grazing Pressure ◽  
Zooplankton Grazing ◽  
Phytoplankton Dynamics ◽  
Phytoplankton Composition ◽  
Isothermal Mixing

Lake Michigan phytoplankton dynamics were studied from the end of spring isothermal mixing (May) through midstratification (July–August) in 1982–84. Phytoplankton composition shifted from a diatom-dominated community (75% of phytoplankton carbon) during May to a phytoflagellate-dominated community (71% of phytoplankton carbon) during July–August. This summer phytoflagellate dominance in the 1980s is distinctly different from the summer blue-green and green algae dominance in the 1970s. Foodweb interactions caused by a changing zooplankton composition and nutrient supply changes were two possible causes. A deep chlorophyll layer (DCL) developed after the onset of thermal stratification. The DCL initially developed in the 15–30 m region and deepended to 25–50 m in July and the 40–70 m region in August. The DCL in 1982–84 was larger in size and located deeper in the water column than those reported from the 1970s. This difference was related to increases in light transparency found in the 1980s that were a result of increased zooplankton grazing pressure.

Vertical and Seasonal Distribution of Chlorophyll a in Lake Michigan

1977 ◽  
Vol 34 (12) ◽  
pp. 2280-2287 ◽  
Author(s):  
Arthur S. Brooks ◽  
Byron G. Torke
Keyword(s):  
Great Lakes ◽  
Chlorophyll A ◽  
Thermal Stratification ◽  
Lake Michigan ◽  
Seasonal Distribution ◽  
Laurentian Great Lakes ◽  
Deep Chlorophyll Maximum ◽  
Phytoplankton Dynamics ◽  
Chain Dynamics ◽  
Offshore Station

Vertical and seasonal distribution of chlorophyll a was observed for 2 yr at an offshore station in Lake Michigan. Chlorophyll a concentrations increased uniformly at all depths during spring reaching 3–4 mg/m3 by late May. Thermal stratification was followed by development of a subthermocline chlorophyll peak between 10 and 30 m that reached 8.5 mg/m3 by late July. The major subthermocline peak collapsed in mid-August but was followed by two lesser peaks at depths of 10 and 30 m. Autumn mixing dispersed these peaks in the mixed layer, increasing the chlorophyll content of the epilimnion at a time when integral chlorophyll levels were declining. At fall overturn chlorophyll concentrations were uniformly distributed at approximately 1 mg/m3, where they remained throughout the winter. The presence of a deep chlorophyll maximum in Lake Michigan adds a new dimension to limnological studies of the Great Lakes. The influence of this peak must be considered in future investigations of food chain dynamics and eutrophication processes in the Great Lakes system. Key words: Laurentian Great Lakes, limnology, chlorophyll a, spatial distribution, phytoplankton dynamics

Measurement of spring thermal stratification in Lake Michigan with the GLUCOS observing system

OCEANS 2009 ◽  
2009 ◽  
Author(s):  
T. R. Consi ◽  
G. Anderson ◽  
G. Barske ◽  
H. Bootsma ◽  
T. Hansen ◽  
...  
Keyword(s):  
Thermal Stratification ◽  
Lake Michigan

A New Thermal Categorization of Ice-covered Lakes

2021 ◽  
Author(s):  
Bernard Yang ◽  
Mathew Wells ◽  
Bailey McMeans ◽  
Hilary Dugan ◽  
James Rusak ◽  
...  
Keyword(s):  
Temperature Profile ◽  
Water Column ◽  
Wind Stress ◽  
Thermal Regime ◽  
Thermal Stratification ◽  
Trophic Status ◽  
Cold Water ◽  
Entire Water Column ◽  
Lake Type

<p>Lakes are traditionally classified based on their thermal regime and trophic status. While this classification adequately captures many lakes, it is not sufficient to understand seasonally ice-covered lakes, the most common lake type on Earth. We describe the inverse thermal stratification in 19 highly varying lakes and derive a model that predicts the temperature profile as a function of wind stress, area, and depth. The results suggest an additional subdivision of seasonally ice-covered lakes to differentiate under-ice stratification. When ice forms in smaller and deeper lakes, inverse stratification will form with a thin buoyant layer of cold water (near 0<sup>o</sup>C) below the ice, which remains above a deeper 4<sup>o</sup>C layer. In contrast, the entire water column can cool to ~0<sup>o</sup>C in larger and shallower lakes. We suggest these alternative conditions for dimictic lakes be termed “cryostratified” and “cryomictic.”</p>

Studies of the hydrobiology of a tropical lake in north-western Queensland. II. Seasonal changes in thermal and dissolved oxygen characteristics

1980 ◽  
Vol 31 (5) ◽  
pp. 589 ◽  
Author(s):  
CM Finlayson ◽  
TP Farrell ◽  
DJ Griffiths
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Environmental Conditions ◽  
Seasonal Changes ◽  
Thermal Stratification ◽  
Oxygen Depletion ◽  
Tropical Lake ◽  
North Western

The stratification characteristics of Lake Moondarra (24�34'S.,139�35'E.), a man-made lake in north- western Queensland, have been studied. Evidence is presented that the lake approximates the warm polymictic type in which no persistent thermal stratification ever develops. During the cooler months, thermal stratification breaks down during the night; in the warmer months, the intense rainstorms prevent the establishment of a persistently stratified water column. The shallowness of the lake relative to its surface areaand the prevailing environmental conditions ensure that extensive periods of oxygen depletion do not develop in the water column. It is concluded that a strong and prolonged period of thermal stratification, with subsequent serious effects of the availability of dissolved oxygen in the deeper layers, would only arise if, in a particular year. there were no significant rainstorms.

Modelling water column processes in the North Sea

1993 ◽  
Vol 343 (1669) ◽  
pp. 509-517 ◽  
Keyword(s):  
Water Column ◽  
North Sea ◽  
Process Water ◽  
Phytoplankton Dynamics ◽  
Annual Cycles ◽  
The North ◽  
Field Investigations ◽  
Southern Central ◽  
The North Sea ◽  
Northern North Sea

In the North Sea advective transports are not negligible. Nevertheless, physical properties like sea surface temperature (SST) can be hindcasted with sufficient precision by vertical process water column models. Annual cycles of SST in the southern, central, and northern North Sea can be simulated using physical upper layer models with relatively small RMS errors. For the Fladenground Experiment (FLEX’76) in the northern North Sea the RMS error is less 0.3 °C for the 2 months of the experiment. This justifies the initial use, at least, of vertical process water column models in simulations for investigating transfer processes in the planktonic ecosystem. Experiments have shown that the simulated entrainment velocities at the bottom of the mixed layer during summer are critically dependent on the resolution of the forcing variables. The effects of this resolution on the annual phytoplankton dynamics will be discussed. Phytoplankton dynamics are strongly influenced by those of the zooplankton, and vice versa. Several field investigations have shown that, seemingly, phytoplankton cannot sustain the observed stock of zooplankton in the northern North Sea: there exists a gap between the abundance of phytoplankton and the need for it to maintain the zooplankton. Revisiting FLEX’76, the simulations with water column models of increasing complexity concerning detritus suggest that pelagic detritus can fill the gap in food availability for the zooplankton. If it is assumed that the zooplankton feeds also on detritus, the zooplankton experiences no food shortage.

scholarly journals Seasonal dynamics of Daphnia laevisBirge, 1878 ephippia in a tropical lake with a description of a new methodology for in situ evaluation

2014 ◽  
Vol 74 (3) ◽  
pp. 642-648 ◽  
Author(s):  
LPM Brandão ◽  
DGF Pujoni ◽  
PM Maia-Barbosa
Keyword(s):  
Water Column ◽  
Seasonal Dynamics ◽  
Thermal Stratification ◽  
Core Sample ◽  
Hatching Rate ◽  
The Core ◽  
Significant Difference ◽  
Chi Squared ◽  
Hatching Rates

The effect of dormancy in zooplankton populations is still unknown, largely because of the lack of methods to estimate hatching and production of the dormant stages. This study aimed to compare the production and hatching rates of ephippia of Daphnia laevis between thermal stratification and mixing periods in Jacaré Lake (Middle Rio Doce, Minas Gerais, Brazil). For this, we collected ephippia on the sediment with core sampler and we created a device called the “Ephippial Collector”. There was a significant difference in ephippia hatching in situ between stratification and mixing periods (Pearson's Chi-squared test p <0.001), being higher in the second one. Significant differences in the hatching rates between periods was observed in the laboratory only for ephippia collected with Ephippial Collectors (Pearson's Chi-squared test p <0.001), being higher during the mixing period (∼8%). The core sample allows the collection of a certain fraction of the sediment that may contain a mixture of ephippia produced in different periods, i.e., may contain old and not viable ephippia, which masks the hatching rate. Thus, seasonality in hatching rates of ephippia was reported only by Ephippial Collectors. The higher hatching rate observed during the mixing period in the lake suggests that individuals hatched from ephippia may contribute to the increase in the population of D. laevis in the water column at this time.

Water column nutrient processing rates in rivermouths of Green Bay (Lake Michigan)

2018 ◽  
Vol 142 (1) ◽  
pp. 73-93 ◽  
Author(s):  
James H. Larson ◽  
Mary Anne Evans ◽  
Faith A. Fitzpatrick ◽  
Paul C. Frost ◽  
Sean Bailey ◽  
...  
Keyword(s):  
Water Column ◽  
Lake Michigan ◽  
Green Bay ◽  
Nutrient Processing ◽  
Water Column Nutrient
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