Update on Phosphorus and Cladophora in the Lake Michigan Nearshore - PDF document

Update on Phosphorus and Cladophora in the Lake Michigan Nearshore Zone Harvey Bootsma Nearshore TP and TDP Concentrations Since 1980, Near Milwaukee Harbor 30 Total Dissolved P Total P 25 19.4 20 [P] ( μ g L -1 ) 14.5 15 12.5 12.6 11.9 11.7 9.5 10 8.2 7.8 6.9 5 0 1980-84 1985-89 1990-94 1995-99 2000-05 1

Spring Total P (mean of all pelagic stations) 7 GLWQA Target for Lake Michigan: 7 μ g/L 6 Michigan 5 Total P ( μ g/L) 4 3 Huron 2 1 0 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 20-Year Phosphorus Trend at River Junction 0.3 0.25 0.2 TP mg/L 0.15 0.1 0.05 SRP 0 1 1 / / 8 2 1 1 / / 8 3 1 / 1 / 8 4 1 2 / 3 1 / 8 4 1 / 1 8 / 6 1 / 1 / 8 7 1 1 / 8 / 8 1 2 3 / 1 / 8 8 1 / 1 9 / 0 1 1 / / 9 1 1 1 / / 9 2 1 2 3 / 1 9 / 2 1 1 / / 9 4 1 / 1 / 9 5 1 / 1 9 / 6 1 2 / 3 1 / 9 6 1 / 1 9 / 8 1 / 1 / 9 9 1 / 1 0 0 / 1 2 / 3 1 / 0 0 1 / 1 / 0 2 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 Data Source: MMSD 2

In Milwaukee River, dissolved P is becoming a larger fraction of TP 0.8 0.7 Dissolved P : Total P Ratio 0.6 0.5 0.4 0.3 0.2 0.1 0 1980 1985 1990 1995 2000 2005 P in Wisconsin Cropland 60 Average [P] (ppm) 50 40 30 20 10 0 1968- 1974- 1978- 1982- 1986- 1991- 1995- 73 77 81 85 90 94 99 5 Soil P Storage Change 4 (kg ha -1 ) 3 2 1 0 1970 1975 1980 1985 1991 1994 1995 Bundy and Sturgul 2001 3

Milwaukee River Transect, April 2005 10 9 8 7 6 5 4 3 2 1 0 20 40 60 80 SRP ( μ g L -1 ) infotrek.er.usgs.gov/.../ milwaukeemap.gif 250 200 1982-87 Mean = 102 150 100 50 0 J F M A M J J A S O N D J F M A M J J A S O N D 250 Total P ( μ g L -1 ) 200 Milwaukee River TP 1988-95 150 Concentrations have Mean = 72 increased in late spring. 100 50 0 J F M A M J J A S O N D J F M A M J J A S O N D 250 1996-2001 200 Mean = 120 150 100 50 0 J F M A M J J A S O N D 4

Milwaukee River Discharge 40 35 1982-87 30 Avg. = 18.4 25 20 15 10 5 Annual Means 0 J F M A M J J A S O N D 25 35 20 30 1988-95 15 25 m 3 s -1 Avg. = 13.1 20 10 15 5 10 5 0 0 1981 1986 1991 1996 2001 J F M A M J J A S O N D 35 30 1996-2001 25 Avg. = 14.3 20 15 10 5 0 Data source: USGS J F M A M J J A S O N D 5

Milwaukee region Nearshore Phosphorus loads, May – July 2006 Milwaukee R. River load: 120 mg P m -2 Menomonee R. Kinnickinnic R. C l a d o p h Mussel Excretion: o r a 506 mg P m -2 z o n e 10 km 10 km 6

The Lake Michigan The Lake Michigan Phosphorus Cycle Phosphorus Cycle P Load Nearshore Loop Offshore Loop Outflow Phytoplankton DP DP Zooplankton Fish Burial Mussels have made nearshore water clear Mussel invasion Source: MMSD 7

November 2007 November 2008 8

Near-Bottom Total Dissolved Phosphorus Atwater, Lake Michigan 10 9 8 7 TDP ( μ g/L) TDP (mg/L) 6 5 2008 4 3 2006 2007 2 1 0 May June July Aug. Sep. Oct. Water Temperature at 9 m 25 2006 20 o C) Temperature ( 15 2008 10 5 0 Apr May Jun Jul Aug Sep Oct Nov 9

Lake Michigan Nearshore Summer Temperature Trend 14 Optimum for Cladophora growth 13 12 June - August Mean T ( o C) 11 10 9 8 7 6 5 no Cladophora growth 4 1970 1975 1980 1985 1990 1995 2000 2005 TEMPERATURE PHOSPHORUS Quagga Mussel Cladophora 10

Lab Experiments: Phosphorus Excretion by Quagga Mussels 0.02 0.018 22 o C 0.016 μ gP mgDW -1 hr -1 0.014 0.012 0.01 0.008 0.006 15 o C 0.004 10 o C 0.002 0 0 5 10 15 20 25 30 -1 ) Food Concentration (mg P ml 400 0.2 0.18 350 0.16 300 Biomass (gDW m -2 ) Growth Rate (day -1 ) 0.14 B 250 0.12 200 0.1 0.08 150 μ no mussels 0.06 100 mussels 0.04 50 0.02 0 0 0 5 10 15 20 25 30 35 Temperature ( o C) 11

LIGHT ? P Flux Between Mussels and Cladophora 0.2 0.15 μ g P mussel -1 hr -1 0.1 0.05 0 Clean Mussels Dirty Mussels Mussels + Cladophora -0.05 -0.1 12

Current Needs 3. What is the botulism mechanism? Photo: Alice Van Zoeren 13

4 minutes after dye injection 14

K = 0.1 cm 2 s -1 above mussels K = 0.01 cm 2 s -1 mussel bed Effect of benthic respiration on thickness of anoxic layer 1.2 Depth of anoxic zone in mussel bed 1 0.8 0.6 0.4 0.2 0 -1000 1000 3000 5000 7000 O 2 uptake rate (mg m -2 d -1 ) 15

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Benthic O 2 uptake by mussels 10 9.5 DO (% Sat.) 5,258 mg O 2 m -2 d -1 9 8.5 8 7.5 7 0 50 100 Time (minutes) Effect of benthic respiration on thickness of anoxic layer Depth of anoxic zone in mussel bed (cm) 1.2 1 0.8 0.6 0.4 0.2 0 -1000 1000 3000 5000 7000 O 2 uptake rate (mg m -2 d -1 ) 17

K = 0.1 cm 2 s -1 above mussels K = 0.01 cm 2 s -1 mussel bed Underwater Particle Image Velocimetry (PIV) System 18

PIV Image Analysis Results Qian and Bootsma, in press 19

Vertical Soluble Reactive Phosphorus Profile Over Mussel Bed 60 50 dc F = 40 D Height (mm) dz 30 20 10 0 0 10 20 30 40 50 [SRP] (nmol l -1 ) The Cladophora Solution 20

Bruce Mozert / University of Florida Press 21