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Physical and biogeochemical mechanisms of internal carbon cycling in L ake M ichigan
Author(s) -
Pilcher Darren J.,
McKinley Galen A.,
Bootsma Harvey A.,
Bennington Val
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2014jc010594
Subject(s) - environmental science , carbon cycle , biogeochemistry , spring bloom , phytoplankton , oceanography , biogeochemical cycle , hypolimnion , dissolved organic carbon , eutrophication , upwelling , bloom , nutrient , ecosystem , ecology , environmental chemistry , geology , chemistry , biology
The lakewide seasonal carbon cycle of Lake Michigan is poorly quantified and lacks the mechanistic links necessary to determine impacts upon it from eutrophication, invasive species, and climate change. A first step toward a full appreciation of Lake Michigan's carbon cycle is to quantify the dominant mechanisms of its internal carbon cycle. To achieve this, we use the MIT general circulation model configured to the bathymetry of Lake Michigan and coupled to an ecosystem model to simulate the seasonal cycle of productivity, temperature, circulation, and the partial pressure of CO 2 in water ( p CO 2 ). This biogeochemistry is designed to be appropriate for the prequagga mussel state of the lake. The primary mechanism behind the seasonal cycle of primary productivity is lake physics. The offshore spring phytoplankton bloom begins following a reduction in deep vertical mixing and ends with the depletion of nutrients via thermal stratification. The exception is the western shoreline, where summer winds drive coastal upwelling, providing hypolimnetic nutrients and generating significant productivity. Surface p CO 2 is controlled by the net effect from temperature on solubility, and is modulated by biological uptake of dissolved inorganic carbon (DIC) and isothermal mixing of DIC‐rich water in winter. Temperature tends to have the greatest seasonal impact in nearshore regions, while local DIC has the greatest impact in offshore regions. Lakewide, the model suggests that carbon is absorbed from the atmosphere during the spring bloom and released to the atmosphere during winter mixing and when summer surface temperatures are at their maximum.