Indicators of Phosphorus Deficiency in Lake Erie

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Indicators of Phosphorus Deficiency in Lake Erie.
Presented at the Ohio Academy of Sciences, 2012.

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Indicators of Phosphorus Deficiency in Lake Erie

  1. 1. Indicators of Phosphorus Deficiency in Lake Erie Leigh Martin Dr. Darren Bade April 14, 2012
  2. 2. Pre-Dreissenid Invasion Nearshore OffshoreP Input Algae Algae Benthos
  3. 3. Pre-Dreissenid Invasion Nearshore OffshoreP Input Algae Algae Benthos Post-Dreissenid Invasion Nearshore Offshore P Input Algae Algae Benthos
  4. 4. Hypothesis• Based on the Nearshore Phosphorus Shunt hypothesis, we expect to find greater instances of P deficiency at offshore sites compared to nearshore sites
  5. 5. Experimental Design Cattaraugus Cr. Westfield Erie Ashtabula R. Sterling State Park Grand R. Turtle Cr. Turtle Creek Huron R.8 Transects in June and August 2011◦ 2 Western Basin, 3 Central Basin, 3 Eastern BasinDepths ranging nearshore to offshore – 2, 5, 10,and 20 meters
  6. 6. Experimental Design• Phosphorus Turnover Time < 60 minutes is P deficient• Phosphorus Debt – Amount of P taken up in 24 hours relative to the amount of Chl a. >0.075 µmole P/µgram Chl a. is P deficient
  7. 7. Phosphorus Turnover – Western Basin Sterling State Park Turtle Creek 1327.8 1489.6 1000June No Deficiency 100 Turnover Time (min) 10 Deficiency 1 2 5 8 2 5 10 100August 10 1 2 5 8 2 5 10 Depth (m)
  8. 8. Phosphorus Turnover – Central Basin Huron River Grand River Ashtabula RiverJune 13970.5 21055.4 1000 100 Turnover Time (min) 10 1 2 5 10 20 2 5 10 20 2 5 10 20August 1121.4 100 10 1 2 5 10 20 2 5 10 20 2 5 10 20 Depth (m)
  9. 9. Phosphorus Turnover – Eastern BasinJune Erie, PA Westfield, NY Cattaraugus Creek 2084.4 1000 100 Turnover Time (min) 10 1 2 5 10 20 2 5 10 20 2 5 10 20August 362.5 264.5 100 10 1 2 5 10 20 2 5 10 20 2 5 10 20 Depth (m)
  10. 10. Chl. a TrendsChl. a• Seasonal increases from June to August in all basins• Lower Chl. a levels at offshore depths Average Chl a Values 60 50 40 ug Chl a/L 30 June August 20 10 0 Western Central Eastern
  11. 11. SRP Trends • Average SRP showed a seasonal decline in Western and Central basins • Higher SRP values were found more often at nearshore sites than at offshore sites 0.05 0.05 Average June SRP Average August SRP 0.04 0.04 0.03 0.03mg P/L 0.02 0.02 0.01 0.01 0 0
  12. 12. Summary & Conclusions• Seasonal versus Spatial P Limitation – Seasonal declines in SRP = Increased P deficiency overall – Spatially, there was no clear trend of increasing P deficiency from nearshore to offshore – Declines in offshore Chl. a may not be due to declines in SRP • Potential Limitation by N or Co-Limitation by N and P in offshore areas
  13. 13. AcknowledgmentsKent State University Curtis Clevinger Heather Kirkpatrick Smith Shunya YagiDr. Chris Pennuto, University of BuffaloDr. Jack Kramer, Heidelberg UniversityScott Winkler, EPA
  14. 14. P Turnover PO43-(µg/L)___ = Turnover Time (min) Uptake (µg/L/min) PO43-(µg/L)___ PO43-(µg/L)___ OR = Slower Turnover TimeUptake (µg/L/min) Uptake (µg/L/min) PO43-(µg/L)___ OR PO43-(µg/L)___Uptake (µg/L/min) Uptake (µg/L/min) = Faster Turnover Time

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