title: Systematically variable planktonic carbon metabolism along a land-to-lake gradient in a Great Lakes coastal zone.
abstract: During the summers of 2002-2013, we measured rates of carbon metabolism in surface waters of six sites across a land-to-lake gradient from the upstream end of drowned river-mouth Muskegon Lake (ML) (freshwater estuary) to 19 km offshore in Lake Michigan (LM) (a Great Lake). Despite considerable inter-year variability, the average rates of gross production (GP), respiration (R) and net production (NP) across ML (604 ± 58, 222 ± 22 and 381 ± 52 µg C L-1day-1, respectively) decreased steeply in the furthest offshore LM site (22 ± 3, 55 ± 17 and -33 ± 15 µg C L-1day-1, respectively). Along this land-to-lake gradient, GP decreased by 96 ± 1%, whereas R only decreased by 75 ± 9%, variably influencing the carbon balance along this coastal zone. All ML sites were consistently net autotrophic (mean GP:R = 2.7), while the furthest offshore LM site was net heterotrophic (mean GP:R = 0.4). Our study suggests that pelagic waters of this Great Lakes coastal estuary are net carbon sinks that transition into net carbon sources offshore. Reactive and dynamic estuarine coastal zones everywhere may contribute similarly to regional and global carbon cycles.
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Weinke
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Scott T
authors.initials: ST
authors.lastname: Kendall
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA ; Munson Medical Center , 1105 6th Street, Traverse City, MI 49684 , USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Kroll
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA ; Salish Sea Expeditions , 647 Horizon View Pl Nw, Bainbridge Isle, WA 98110 , USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Strickler
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Maggie E
authors.initials: ME
authors.lastname: Weinert
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA ; Herman Miller , 855 East Main Street, Mail Stop 0156, Zeeland, MI 49464 , USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Holcomb
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA ; USC Baruch Marine Field Lab , U. South Carolina , Po Box 1630, Georgetown, SC 29442 , USA.
authors.forename: Angela A
authors.initials: AA
authors.lastname: Defore
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA ; School of Freshwater Sciences , U. Wisconsin-Milwaukee , 600 E. Greenfield Ave, Milwaukee, WI 53204 , USA.
authors.forename: Deborah K
authors.initials: DK
authors.lastname: Dila
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Snider
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Leon C
authors.initials: LC
authors.lastname: Gereaux
authors.affiliation: Annis Water Resources Institute, Grand Valley State University , 740 West Shoreline Drive, Muskegon, MI 49441 , USA.
authors.forename: Bopaiah A
authors.initials: BA
authors.lastname: Biddanda
keywords: coastal; gradient; pelagic; production; respiration