Managing the Impact of Multiple Stressors in Saginaw Bay

Project Updates

September 29, 2009

Field Sampling Highlights

Image of scuba divers Sampling was conducted monthly all summer for fish and water quality parameters at our monitoring stations. Our last sampling point for 2009 will be the week of 28 September.

Our graduate students from MSU, Kim Peters and Dianna Dziekan, were extremely busy this summer with characterizing the benthic algal composition and nutrient content along transects in the SW part of the inner bay. They observed Cladophora, Spirogyra and lots of Chara. Often the Cladophora was heavily epiphytized, especially the samples collected in late spring. In addition, PAM (pulse amplitude modulated) fluorometry measurements to assess photosynthetic health and a preliminary lab–based Spirogyra growth experiment were conducted to further understand growth dynamics. See data shown below.

A beach muck survey was conducted primarily by one of GLERL's summer fellows, Cory VonAchen.. Beaches along the inner Bay from Bay City to Linwood were sampled. While there was muck present, subjectively it seemed to be much less than last year. One hypothesis is this is related to high water levels this year.

In addition to benthic algae, there was also a substantial Microcystis bloom this summer in the inner bay. While concentrated near the mouth of the Saginaw River, during late August/early Sept it was observed through much of the SE portion of the inner bay.

Image of microcystis bloom An adaptive component of the project implemented this summer was the deployment of an ADCP (acoustic doppler current profiler) in the inner bay near the Saginaw River to provide field validation to the current and river plume nowcasts (http://www.glerl.noaa.gov/res/glcfs/sb/). Deployments at various depths for 2 week intervals gave a good picture of current patterns near the river mouth.

Of the fish eaten by age-1 and older walleye in the summer (July–Sept), (by number), 63% were perch, mostly age–0 and 23% were round goby and 9% were gizzard shad.

Experimental highlights

Donna Kashian and her group assessed the availability of N and P in surficial sediments in various regions of the Bay. Divers collected sediments cores from three regions of the Bay including near river mouth, near mussel beds and in the deep depositional basin of the bay. At each sampling site the carbon and nutrient content of the sediments was assessed as well as general porosity and bulk density. Secondly, direct sediment nutrient flux experiments were conducted under both aerobic and anaerobic conditions. Results indicated phosphorus release from bay sediments is highly correlated with oxygen levels. Oxic waters exhibited minimal levels of P release while anoxic/hypoxic waters showed significant P release back to overlying waters. This may indicate that P loading contributions from sediments in Saginaw Bay are controlled by episodic anoxic events. Therefore, models for the bay will need to take hypoxia/anoxia events into account when predicting nutrient loads and budgets. This may also represent a positive feedback in eutrophication; with blooms contributing to anoxia which in turn appears to greatly stimulate nutrient release from the sediments. Data is shown below.

Modeling

YoonKyung Cha, from Duke University, used Bayesian approaches to estimate TP loads through the Saginaw River. Results below.

PI Workshop

Our PI workshop this year will be December 14, 2009 at GLERL.

Data

Bayesian Approaches to TP Loads

Estimated annual TP loads from the Saginaw River using a Bayesian hierarchical (partial–pooling) model. Symbols indicate mean values with a 95% predictive interval. Prepared by YoonKyung Cha at Duke University.

SRP Flux from Sediments

A comparison of the Soluble Reactive Phosphorus (SRP) flux defined as µg/m² per day of SRP released from the sediments between hypoxic and oxic conditions calculated from sediment core samples collected at three sites in inner Saginaw Bay. Sediment cores from site five were located in quagga mussel beds, site ten is in the deep depositional basin and site 14 is on the SE ridge with a pebble substrate. (From Donna Kashian)

Benthic Algal Distribution and Composition

Location of study transects (9, 11, 13, 14, 15, and 18) in inner Saginaw Bay, Lake Huron, Michigan.

Biomass by Transect Location

Mean biomass (g/m²) of Chara, filamentous green algae, and macrophytes, averaged over all depths (0.5 – 5.0m) and survey dates (July – Sept. 2009), at each of the six transect locations.

Transect 11 Biomass over Time

Mean biomass (g/m²) of Chara, filamentous green algae, and macrophytes, at transect 11 averaged over all sampling depths (1.0, 2.0, 3.0, and 4.0 m), at each of the five sampling dates (July 9th, July 24th, August 12th, August 19th, and September 20th, 2009).

Transect 11 Biomass by Depth

Mean biomass (g/m²) of Chara, filamentous green algae, and macrophytes, at transect 11 averaged over all sampling dates (July 9th, July 24th, August 12th, August 19th, and September 20th, 2009), at 1.0, 2.0, 3.0, and 4.0 meters depth. (Graphs from Dianna Dziekan)

Thanks

Many thanks to all those who helped in the field and lab this summer: Dianna Dziekan, Kim Peters, Jess Kunke, Cory VonAchen, Nancy Morehead, Kamau Mbalia, YoonKyung Cha, Duane Gossiaux, Hunter Oates, Vijay Kannappan, Ashley Burtner, Eric Anderson, Lee Wyrobek, Charlie Roswell, Beth Coggins, Chris Henry, Sander Robinson, Charlie Herrington, Steve Francouer, Steve Bawks, Andrew Yagiela, Mike Taetsch, Beau, Tom Joyce, Steve Constant, Jack Workman