Bio-optical properties and primary production of Lake Michigan: Insights from 13-years of SeaWiFS imagery

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Thirteen years of SeaWiFS data (1998-2010) from the early spring isothermal period (March-April) were used to determine trends of water attenuation coefficient (KdPAR), chlorophyll a (Chl a), Photosynthetic Available Radiation (PAR), and modeled primary production in southern Lake Michigan. Surface PAR values remained unchanged between 1998 and 2010, but there was an 18-22% drop in KdPAR during the March/April isothermal period as water clarity increased. This transparency increase was accompanied by a 41-53% decline in Chl a concentration (μg·L-1) and a 42-46% decline in modeled primary production (Great Lakes Primary Production Model). These changes were most pronounced in 2001-2003 which coincided with the period of initial colonization of the quagga mussels. Statistically significant spatial differences were noted in Chl a (μg·L-1) concentrations between mid-depth (z=30-90m deep), and offshore (z> 90m deep) waters. Chl a concentrations in the mid-depth region (30-90m) decreased at a higher rate compared to offshore waters (> 90m) likely as a result of filtration activities of quagga mussel. © 2014 Elsevier B.V.

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Journal of Great Lakes Research