Anatomy of the recurrent coastal sediment plume in Lake Michigan and its impacts on light climate, nutrients, and plankton

Abstract

[1] As part of the Episodic Events Great Lakes Experiment, we sampled total suspended matter (TSM), light climate, nutrients, and plankton along cross-margin transects in southern Lake Michigan during February, March, and April 1998-2000 to capture conditions before, during, and after the occurrence of storm-driven recurrent coastal sediment plumes to define the anatomy of the resuspension events and get insights into their interactions with nutrients and plankton. Variability in timing and strength of winter storms among years led to different timing, intensity, and extent of plumes among years. TSM concentrations in the core of plumes varied between 15 and 30 mg L À1 , and photic depth was reduced to $1 to 2 m, thus potentially seriously limiting phytoplankton growth in plume areas. Total P concentration was highly correlated with TSM and river influence. Chlorophyll concentrations were lower in plume regions than in adjacent areas, in contrast to the relatively constant chlorophyll concentration across the plume predicted by a coupled hydrodynamic and nutrient-phytoplankton-zooplankton model. Contrary to expectation, protozoan microzooplankton (MZ) biomass was not more abundant in the plume than adjacent waters, but was highest in nearshore areas receiving river inflow. Storms affected horizontal distribution of zooplankton. Because of the lower concentrations of phytoplankton in the plume, the plume over the short term had a negative impact on zooplankton during this food-limiting season. Our results combined with those of other EEGLE studies lead us to conclude that storms and storm-driven plumes had a negative effect on the planktonic food web. Citation: Vanderploeg, H. A., et al. (2007), Anatomy of the recurrent coastal sediment plume in Lake Michigan and its impacts on light climate, nutrients, and plankton,

Coastal Sediment Dynamics and River Discharge as Key Factors Influencing Coastal Ecosystem Productivity in Southeastern Lake Michigan

“…Projected changes in climate may lead to reduced ice cover in the Great Lakes (e.g., Magnuson et al, 1997) and increased frequency and intensity of extratropical storms (Trenberth et al, 2007). Such a scenario could lead to more intense and extensive RCP events, with profound consequences for ecosystem productivity.…”

“…latitude (Trenberth et al, 2007), which would presumably lead to increases in river discharge and delivery of terrestrial materials into the coastal regions. We observed that river discharge exhibited a more localized influence on optical conditions, and presumably biogeochemical conditions, apparently resulting in an enhancement of phytoplankton primary production during periods of high discharge and moderate RCP intensity.…”

Dreissena and the disappearance of the spring phytoplankton bloom in Lake Michigan

“…Strong support for a well-mixed water column is given by a number of recent studies, particularly those associated with the Episodic Events Great Lakes Experiment (EEGLE), that clearly demonstrated that properties like chlorophyll concentrations are constant from top to bottom and that currents have the same direction and speed from top to bottom, thus implying a mixed condition (e.g. Fahnenstiel et al, 2000;Beletsky et al, 2003;Rao et al, 2004;Vanderploeg et al, 2007;Kerfoot et al, 2008Kerfoot et al, , 2010.…”

Seasonal zooplankton dynamics in Lake Michigan: Disentangling impacts of resource limitation, ecosystem engineering, and predation during a critical ecosystem transition

“…That is, the protozoans (primarily ciliates), a favored prey of mussels (Lavrentyev et al, 1995), suffered a double blow: direct mortality and reduction of food supply from quagga mussels. Protozoan microzooplankton-primarily ciliateswere identified as a major component of the winter-spring zooplankton community, having a biomass of about the same as the mesozooplankton during 1998-2000 with L. sicilis obtaining 22-74% of its ingested C from the protozoans and the balance from phytoplankton (Bundy et al, 2005;Vanderploeg et al, 2007). As such, they are an important food resource to both diaptomids and Diacyclops.…”

“…Sample collection and analysis followed methods described by Vanderploeg et al (2007). In brief, samples were collected using duplicate vertical tows of a 50-cm diameter, 2.5-m long, 153-μm mesh, conical net equipped with an internal calibrated flow meter from 1 to 2 m above the bottom to the surface.…”