Presentation on theme: "Nuisance Cladophora Blooms in Lake Michigan: Possible Causes and Management Options Harvey Bootsma Erica Young John Berges."— Presentation transcript:
Nuisance Cladophora Blooms in Lake Michigan: Possible Causes and Management Options Harvey Bootsma Erica Young John Berges
HARD SUBSTRATE NUTRIENTS Phosphorus LIGHT 13 – 17 o C TEMPERATURE
The Role of Temperature
J J A S O N D J F M A M J J A S O Optimum for Cladophora growth
Temperature at the Linnwood Intake (15 m) Optimum for Cladophora growth No growth
The Role of Light
Jul-0431-Jul-0431-Aug-0430-Sep-0431-Oct-04 +ive growth Growth optimum at > 26 mol m -2 d -1 -ive growth July Aug Sep Oct PAR (mol photons m -2 d -1 ) Date Irradiance at 10 m, Atwater
Data provided by MMSD Mussel invasion
Jul-0431-Jul-0431-Aug-0430-Sep-0431-Oct-04 +ive growth -ive growth July Aug Sep Oct PAR (mol photons m -2 d -1 ) Date Irradiance at 10 m, Atwater
The Role of Phosphorus
Influence of P on Cladophora Growth Rate Net Specific Growth Rate (d -1 ) Stored Phosphorus (%P) 0.8
1 g mg Cladophora phosphorus content, September 2004
mg/L SRP TP Year Phosphorus Trend at River Junction
Is there enough phosphorus coming in from rivers to support the Cladophora growth that we observe?
10 km Milwaukee R. Kinnickinnic R. Menomonee R.
Milwaukee River = 250 kg/day P Sources in the nearshore zone (0 – 10 m) Mussel recycling = 1,700 kg/day gg Cladophora demand ~ 2,000 kg/day
June July Aug Sep Oct m 3 s -1 May June July Aug Sep Oct Milwaukee River discharge 3-Year Comparison of Cladophora phosphorus content Lake Michigan Cladophora P content g P mg P limited growth
8oC8oC River P P m
12 o C River P P m
Net Specific Growth Rate (d -1 ) Stored Phosphorus (%P) 0.8 Influence of P on Cladophora Growth Rate
Conclusions The recent increase in Cladophora growth is likely due to: - Increased water clarity (more light at lake bottom) - Warmer water temperatures in summer - increased phosphorus inputs Although P input from rivers has increased, there must also be an internal source of P in the lake that is promoting Cladophora growth. We suspect dreissenid mussels. Future work must focus on the fate of river-borne phosphorus, and the importance of mussels as a phosphorus source. An important question to answer: If we lower P input from rivers, will there be less Cladophora?