Regulation of Water Quality in Lake Michigan: Report of the Food Web Workshop

doi:10.1016/S0380-1330(88)71538-5

Journal of Great Lakes Research

Volume 14, Issue 1, 1988, Pages 109-114

https://doi.org/10.1016/S0380-1330(88)71538-5 Get rights and content

Abstract

During the past 20 years, Lake Michigan has experienced substantial reduction in nutrient inputs, major changes in the biological community, and re-configuration of the pelagic food web. Alewife, the previously dominant zooplanktivore, has decreased to 10–20% of its former abundance, a new assemblage of zooplankton has become dominant, and summer water clarity has increased nearly three-fold in that time. This report summarizes an International Joint Commission (IJC)-sponsored Workshop on Food Web Interactions convened in Ann Arbor during 4–6 December 1985. In general, physical-chemical conditions are the major regulators of water quality during spring and fall periods. Food web effects are most manifest in offshore waters during the period of summer stratification. Discussion during the workshop led to insights regarding the causes of recent changes, their association with nutrient controls and/or food web interactions, and the likely dimensions for future effects.

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Recent changes in primary production and phytoplankton in the offshore region of southeastern Lake Michigan
2010, Journal of Great Lakes Research
Phytoplankton abundance, composition, and productivity were monitored on a bi-weekly basis from March/April through November/December at two offshore stations in southeastern Lake Michigan in 1983–1987, 1995–1998 and 2007–2008 (exception 1983–1984 which were sampled from May to August). During the spring isothermal mixing period, surface-mixed layer (SML) chlorophyll a and phytoplankton biomass (carbon) and water column primary productivity decreased substantially in 2007–2008 as compared to 1995–1998 (66%, 87%, and 70% decrease, respectively). Smaller or no decreases were noted between 1983–1987 and 1995–1998 (chlorophyll a 23% decrease, phytoplankton biomass 5% increase, and production 22% decrease). Phytoplankton composition also changed during the spring isothermal mixing period in 2007–2008 as compared to 1983–1987 and 1995–1998; all phytoplankton groups with the exception of cyanobacteria and chlorophytes exhibited dramatic reductions in 2007–2008. The pronounced changes in phytoplankton properties during spring mixing in 2007–2008 were attributed to the filtering activities of the quagga mussel (Dreissena rostriformis bugensis). During mid- and late thermal stratification periods, SML phytoplankton chlorophyll a and phytoplankton carbon and water column primary production exhibited only one significant change across all decades (mid-stratification production in 2007–2008 as compared to 1995–1998 and 1983–1987). Phytoplankton compositional changes in the SML also were limited during thermal stratification. The size of the deep chlorophyll layer (DCL) in 2007–2008 was similar to or smaller than those in 1983–1987 and 1995–1998. However, phytoplankton composition in the DCL changed as net diatoms constituted < 5% of total phytoplankton in the 2007–2008 DCL but over 50% in 1983–1987 and 1995–1998.
The structure of the planktonic food-web in the St. Lawrence Great Lakes
1998, Journal of Great Lakes Research
The structure of the planktonic food-web was studied during the spring (April/May) and summer (August) periods in 1993 to 1995 at twelve stations located in the offshore region of all five Great Lakes. All components of the planktonic food-web were collected from the same water sample (with the exception of crustaceans), counted microscopically, converted to carbon units, and averaged over the euphotic zone. Due to phosphorus load reductions and the impact of non-indigenous mussels in the lower lakes, physical/chemical characteristics of the lower lakes are becoming similar to those in the upper lakes. Spring total phosphorus and euphotic zone depth were relatively similar among all the stations (except western Lake Erie), ranging from 3 to 7 μg/L and 21 to 26 m, respectively. During the summer, total phosphorus concentrations were more variable, but ranged between 4 to10 μg/L at all stations except western Lake Erie. Planktonic biomass was correlated with total phosphorus concentration. Within a season, the structure of the planktonic food-web was remarkably similar among all stations across all the lakes. Of the seventeen food-web structure parameters examined, only two exhibited significant differences among stations during the spring isothermal period; only four parameters exhibited significant differences among stations during the summer. Small plankton were very abundant in all the lakes. Picoplankton (0.2 to 2.0 μm) biomass was approximately equal to the combined biomass of nanno-and microplankton (2 to 200 μm). For microorganisms (all organisms except crustaceans) autotrophic: heterotrophic ratios averaged 1.3 (spring = 1.1, summer = 1.5). The heterotrophic microorganism community was comprised of bacteria (mean = 65%), protozoans (mean = 32%), and rotifers (3%). Even though zebra mussel veligers were found in all the lakes except Lake Superior, their contribution to microorganism biomass never exceeded 1%. Due to seasonal variation in crustacean abundance, the mean contribution of major functional groups varied by season; producers (autotrophs), decomposers (bacteria), micrograzers (protozoans and rotifers), and mesograzers (crustaceans) constituted 40%, 30%, 11%, and 19% of total planktonic carbon, respectively, during the spring, and 32%, 15%, 9%, and 43%, respectively, during the summer. The overall similarity in the structure of the planktonic food-web across all stations in the Great Lakes was attributed to the strong influence of abiotic factors.
Effects of cultural eutrophication on coastal marine fisheries: A comparative approach
1992, Science of the Total Environment
Several generalities are common to the effects of cultural eutrophication on fisheries in a variety of marine and freshwater ecosystems. Foremost is the absence of definitive diagnostic features to permit discrimination between direct eutrophication effects, and those engendered by other factors, often associated with anthropogenic change. It is also clear that eutrophication may profoundly modify the structure, function and species composition of fish production systems, with attendant consequences for both ecosystem function and the economic value of the yield. Eutrophication and its associated effects fall into one of four categories: direct effects on essential environmental factors; diminished suitability of the habitat factors necessary to sustain fisheries yield; transmission of effects accelerated by the rapid transfer of inimical biota among affected ecosystems; potential for elaboration of fisheries yield in terms of products that are not acceptable for human consumption. Taken together, the patterns of change accompanying cultural eutrophication of fish production systems are generally recognizable, but are not always amenable to differentiation from the effects of associated factors, or to precise quantification.
Bythotrephes Cederstroemi: its New Appearance in Lake Michigan
1988, Journal of Great Lakes Research
Bythotrephes cederstroemi was newly found in Lake Michigan in September 1986. This predaceous cladoceran was previously detected in Lake Huron (December 1984) and subsequently dispersed into Lakes Ontario and Erie (autumn 1985). It was previously known only from Europe. Entry into Lake Michigan may have occurred through the exchange of Lakes Huron and Michigan water masses in the Straits of Mackinac. Bythotrephes cederstroemi was consumed by Lake Michigan deepwater sculpins in October 1986. Since Bythotrephes is believed to be a surface-dwelling species, the most probable route by which it entered the sculpin diet was through the rapid sinking of dying (and dead) animals and their subsequent ingestion by sculpins at the sediment-water interface. Bythotrephes cederstroemi exhibited allometric and cyclomorphic growth. The caudal process was relatively straight in immature specimens and became progressively more kinked in larger (older) animals. Furthermore, the kink was more strongly developed in autumn (October) than summer. (July) B. cederstroemi populations.
Relative comparison and perspective on invasive species in the Laurentian and Swedish Great Lakes
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Trends in spring crustacean zooplankton communities of lake superior: Evidence of planktivory by lake herring
2009, State of Lake Superior

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Journal of Great Lakes Research

Abstract

References (21)

Dynamics of Lake Michigan's phytoplankton: mechanisms controlling epilimnetic communities

J. Great Lakes Res.

Long-term phyto-plankton changes in Lake Michigan: Cultural eutrophication or biotic shifts

Verh. Internal. Verein. Limnol.

Cascading trophic interactions and lake ecosystem productivity

BioScience

Recent shifts in Daphnia community structure in southeastern Lake Michigan: a comparison of the inshore and offshore regions

Limnol. Oceanogr.

Size and condition of trout and salmon from the Wisconsin waters of Lake Michigan, 1969–1984

Changes in the forage fish of Lake Michigan

Can. J. Fish. Aquat. Sci.

Piscivores, planktivores, fossils and phorbins

Predator-prey interactions in Lake Michigan: model predictions and recent dynamics

Env. Biol. Fish.

Cited by (9)

Recent changes in primary production and phytoplankton in the offshore region of southeastern Lake Michigan

The structure of the planktonic food-web in the St. Lawrence Great Lakes

Effects of cultural eutrophication on coastal marine fisheries: A comparative approach

Bythotrephes Cederstroemi: its New Appearance in Lake Michigan

Relative comparison and perspective on invasive species in the Laurentian and Swedish Great Lakes

Trends in spring crustacean zooplankton communities of lake superior: Evidence of planktivory by lake herring