3/7/2016
Investigating golden brown
benthic algae in Torch Lake
Presented to Leelanau Clean Water group
Dean Branson, Becky Norris, Trish Narwold February 18, 2016
Torch. Clam, & Bellaire Lakes www.3lakes.com
Collaborative Investigation with internationally recognized diatom experts
• Dr. R. Jan Stevenson, MSU‐Zoology Dept.
• Dr. Rex Lowe, U of M‐Biological Res. Station
• Dr. Pat Kociolek, U of M‐Biological Res. Station
• Three Lakes Association grant funds and volunteers to collect samples of groundwater and benthic algae; some funds from TLPA
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What is it? What’s causing it?
What can be done to prevent it?
Patterns of golden brown benthic algae, changing the
aesthetic appearance of the lake from beautiful
turquoise to plain brown! Patterns of areas with and without golden brown benthic algae, west side of Torch Lake
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Underwater photo of golden brown benthic algae in Torch Lake
Initial Research Strategy
Compare two sites: Low density land use High density land use
, .
. . Camp Hayo‐Went‐Ha
Petty property, August 2015
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Petty
50.000
μg/L
μg/L
100.000
PO4‐P
NO3‐N
NH4‐N
0.000
SW
100
80
60
40
20
0
PO4‐P
SW
Well
water
Clam Dockside
100
μg/L
East Port DNR
GW
50
Sand Point
0
50
0
SW
GW
PO4‐P NO3‐N NH4‐N
Clam River SW
Lake Ave.
100
80
60
40
20
0
Alden Harbor
GW
NH4‐N
NO3‐N
μg/L
100
PO4‐P
SF
NH4‐N
PO4‐P
100
50
0
NO3‐N
μg/L
SW
GW with band
GW w/out band
μg/L
μg/L
100
50
0
SW
GW
Concentrations of phosphorus
Surface water vs Interstitial water
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Nutrient‐enriched agar in cylinders in Torch Lake for 20 days to determine the nutrient‐limitations of diatoms associated with golden brown benthic algae; July 2015
…. In summary
• Torch Lake P+ limited
• Blooms most likely caused by P input • P source from ground water influx
• Different communities on treatments
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Results of Nutrient Diffusing Substrate Experiment
Cell Densities
N+P
pseudoanab
aena
1%
Ulnaria
1%
P+
Large Diatoms 1%
Achnanthidiu
m
25%
Others 26%
pseudoanaba
ena
2%
Ulnaria
1%
Large Diatoms
1%
Achnanthidi
um
27%
Others 27%
Centric
7%
Other algae
2%
Other algae
11%
Centric
19%
Nitzschia 13%
Naviculoid
3%
Nitzschia 20%
Naviculoid
13%
Cell Density (Cells/cm2) of All Benthic Algae
• Averaging about 500,000 cells/cm2
• Mostly diatoms
• Density in sand more than rock
• Density in sparse sand same as dense sand
• What causes diatoms to move from the top centimeter to the surface of the sand?
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Aerial photos of Gourley beach during 2015 summer season
Paul, Trish, Art, and Fred assembling a piezometer; well point, perforated ¼‐
inch tubing and fine‐
mesh screen.
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Driving a piezometer into the lake bottom
Shayna, Grandpa Dean, & Becky collecting a groundwater sample from a piezometer using a Topsider multipurpose vacuum pump connected to a sample‐collection jug.
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Piezometers
Near‐shore groundwater wells
Professor R. Jan Stevenson and Becky Norris
examining a “peeper” prior to installation 9
3/7/2016
Driving a “peeper” into the lake bottom
An installed “peeper”
…..sampling groundwater (two depths) and surface water using passive diffuser bags in perforated PVC pipes
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Diatom Findings
• 140 Diatom species associated with golden brown benthic algae assemblages; 8 species new to science
• Naturally occurring in most lakes, rather than invasive species
• Epithemia, most abundant diatom taxa, capable of housing blue‐green algae, and endosymbiotic nitrogen fixation
Microscopic image of Epithemia smithii
identified in a sample collected at Camp Hayo‐Went‐Ha.
Intriguing research questions, not yet investigated
• Are groundwater nutrients inducing golden brown algae?
• Are the patterns of groundwater entering the lake similar to the patterns of golden brown algae, infrared images of surface water temp ~40 deg F with rising warmer groundwater ~50 deg F ?
• Do other lakes have similar diatom assemblages and groundwater profiles as the golden brown benthic algae assemblages in Torch Lake?
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Questions ?
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