DDeecceemmbbeerr,, 22001188

BBeeaarr LLaakkee 22001188 AAqquuaattiicc VVeeggeettaattiioonn,,

WWaatteerr QQuuaalliittyy,, aanndd 22001199 MMaannaaggeemmeenntt

RReeccoommmmeennddaattiioonnss AAnnnnuuaall RReeppoorrtt

BBeeaarr LLaakkee 22001188 AAqquuaattiicc VVeeggeettaattiioonn,,

WWaatteerr QQuuaalliittyy,, aanndd 22001199 MMaannaaggeemmeenntt

RReeccoommmmeennddaattiioonnss AAnnnnuuaall RReeppoorrtt

Restorative Lake Sciences 18406 Spring Lake Road

Spring Lake, Michigan 49456 Email: info@restorativelakesciences.com

Website: http://www.restorativelakesciences.com

Table of Contents

Section 1: Bear Lake Summary (2018) ................................................... 4

Section 2: Bear Lake Water Quality Data (2018) ................................... 5

Section 3: Bear Lake Aquatic Vegetation Data (2018) ........................ 18

Section 4: Bear Lake Sediment Core Petroleum Data (2018) ............. 25

Section 5: Management Recommendations for 2019 ......................... 28

4

BBeeaarr LLaakkee 22001188 AAqquuaattiicc VVeeggeettaattiioonn,,

WWaatteerr QQuuaalliittyy,, aanndd 22001199 MMaannaaggeemmeenntt

RReeccoommmmeennddaattiioonnss AAnnnnuuaall RReeppoorrtt

The overall condition of Bear Lake relative to invasive species management has been improving over the years due to rigorous aquatic vegetation surveys and selective spot-treatments to control invasive aquatic plant species such as hybrid Eurasian Watermilfoil (EWM), and Curly-leaf Pondweed (CLP). Both of these species are declining in Bear Lake and providing space for the 17 native aquatic plant species that are so important to the ecological balance of Bear Lake.

In 2018, RLS collected multiple water quality parameters from Bear Lake and the inlets (Fenner’s Ditch and Bear Creek) which include water temperature, dissolved oxygen, pH, conductivity, total suspended and dissolved solids, turbidity, total and ortho-phosphorus and total nitrogen, Secchi transparency, and chlorophyll-a and algal community were also measured and collected in the deep basins. In addition, RLS collected 30 sediment core samples from within Bear Lake to determine the sediment petroleum concentrations. There were 8 sites of the 30 that contained elevated levels of petroleum which were scattered around the lake bottom and indicate widespread occurrence. These sites will be re-visited for more intense sampling in 2019. Addition of microbes that digest petroleum on the lake bottom are recommended in the near future.

There is concern about the overabundance of the blue-green algae Microcystis and Oscillatoria rubescens that were found in abundance in 2018 and likely have been frequent in the lake for years. These algae are able to thrive in low oxygen conditions and thus are indicative of the need for whole-lake aeration, which is being planned. The low quality of sediment macroinvertebrates previously found also encourages the need for lake and sediment aeration.

RLS offers many improvement recommendations for the 2019 season and beyond relative to nutrient reduction, blue-green algal reduction, continued management of invasive aquatic plant species, reduction of Canada geese, and the education of Bear Lake riparians.

Section

1

5

Bear Lake Water Quality Data (2018)

Water Quality Parameters Measured

There are hundreds of water quality parameters one can measure on an inland lake but several are the most critical indicators of lake health. These parameters include water temperature (measured in °C), dissolved oxygen (measured in mg/L), pH (measured in standard units-SU), specific conductivity (measured in micro-Siemens per centimeter-µS/cm), total dissolved and suspended solids (mg/L), turbidity (NTU’s), secchi transparency (feet), total and ortho-phosphorus, and total Kjeldahl nitrogen (both in mg/L), chlorophyll-a (in µg/L), and algal species composition. Water quality was measured in two deep basins of Bear Lake in spring (May 31, 2018), summer (July 27, 2018), and late summer (September 7, 2018; Figure 1). Water quality measurements were recorded in 0.5 meter depth increments.

Additional water quality measurements were also collected from the two main inlets—Fenner’s Ditch and Bear Creek at the northeast region of the lake (Figure 2).

A total of 30 sediment cores (4-feet in length) were collected with a sediment coring instrument. Each core was sectioned into the upper, middle, and lower sections of sediment which were placed into sterile glass jars and placed in a cooler and taken to TRACE laboratories for analysis of diesel range organics (DRO), oro range organics (ORO), and percentage of organic matter.

Table 1 below demonstrates how lakes are classified based on key parameters. Bear Lake would be considered eutrophic (productive) since it does contain ample phosphorus, nitrogen, and aquatic vegetation and excessive blue-green algae growth. General water quality classification criteria are defined in Table 1. 2018 water quality data for Bear Lake are shown below in Tables 2-7.

Section

2

6

Figure 1. Deep Basin Water Quality Sampling Locations (n=2) in Bear Lake.

Figure 2. Inlet Water Quality Sampling Locations (n=2) in Bear Lake.

7

Table 1. Lake trophic classification (MDNR).

Lake Trophic Status

Total Phosphorus

(µg L-1)

Chlorophyll-a (µg L-1)

Secchi Transparency

(feet) Oligotrophic < 10.0 < 2.2 > 15.0

Mesotrophic 10.0 – 20.0 2.2 – 6.0 7.5 – 15.0

Eutrophic > 20.0 > 6.0 < 7.5

Bear Lake Deep Basin Water Quality Data Tables:

Table 2. Bear Lake water quality parameter data collected over deep basin #1 on May 31, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

25.3 25.3 25.1 24.9 22.2 22.0 21.0 20.0 18.9 17.3 16.4 16.3 16.1 16.1 16.1 16.0

8.2 8.2 8.2 8.3 6.4 5.9 4.8 3.8 2.3 1.2 0.7 0.5 0.3 0.1 0.1 0.0

8.3 8.3 8.3 8.3 7.9 7.7 7.7 7.6 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5

366 365 364 364 366 366 367 368 369 370 374 383 383 383 384 385

6.0 -- -- -- -- -- --

6.9 -- -- -- -- -- -- --

6.9

234 233 233 233 234 234 235 235 236 237 240 241 245 245 246 246

<10 -- -- -- -- -- --

<10 -- -- -- -- -- -- --

<10

0.030 -- -- -- -- -- --

0.041 -- -- -- -- -- -- --

0.064

<0.010 -- -- -- -- -- --

0.017 -- -- -- -- -- -- --

0.031

0.5 -- -- -- -- -- --

1.0 -- -- -- -- -- -- --

1.6

0.534

8

Table 3. Bear Lake water quality parameter data collected over deep basin #2 on May 31, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

25.4 25.4 25.3 25.3 25.1 24.6 22.1 19.7

8.6 8.8 8.9 9.0 9.0 9.0 6.8 5.7

8.5 8.5 8.5 8.5 8.4 8.3 7.8 7.7

364 364 363 363 363 363 370 372

5.6 -- -- --

5.4 -- --

5.9

233 233 233 233 232 232 236 238

<10 -- -- --

<10 -- -- 16

0.022 -- -- --

0.040 -- --

0.070

<0.010 -- -- --

0.014 -- --

0.013

0.7 -- -- --

1.0 -- --

1.1

0.890

Table 4. Bear Lake water quality parameter data collected over deep basin #1 on July 27, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

26.5 26.5 26.3 25.7 25.4 25.1 25.0 25.0 24.8 24.7 24.7 23.8 23.4 23.3 23.3 23.2

8.0 8.0 8.0 7.9 7.5 7.5 7.1 6.5 6.5 6.5 6.5 6.4 2.9 0.1 0.1 0.1

8.5 8.5 8.5 8.5 8.5 8.5 8.0 8.0 7.8 7.8 7.8 7.8 7.8 7.7 7.7 7.7

365 364 364 364 364 364 364 364 366 366 366 367 367 370 372 380

4.9 -- -- -- -- -- --

5.6 -- -- -- -- -- -- --

5.7

235 235 233 233 233 233 235 235 236 235 235 235 240 242 241 246

<10 -- -- -- -- -- --

<10 -- -- -- -- -- -- -- 20

0.030 -- -- -- -- -- --

0.045 -- -- -- -- -- -- --

0.050

0.015 -- -- -- -- -- --

0.010 -- -- -- -- -- -- --

0.020

<0.5 -- -- -- -- -- --

1.0 -- -- -- -- -- -- --

2.0

6.0

9

Table 5. Bear Lake water quality parameter data collected over deep basin #2 on July 27, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

26.7 26.7 26.5 26.1 26.0 25.1 25.0 25.0

8.6 8.8 8.9 9.0 9.0 9.0 6.8 5.7

8.5 8.5 8.5 8.5 8.4 8.3 7.9 7.9

364 364 363 363 363 363 370 372

5.6 -- -- --

5.4 -- --

5.9

233 233 233 233 232 232 236 238

<10 -- -- --

<10 -- --

<10

0.020 -- -- --

0.040 -- --

0.070

<0.010 -- -- --

0.011 -- --

0.030

0.7 -- -- --

1.0 -- --

1.1

10.0

Table 6. Bear Lake water quality parameter data collected over deep basin #1 on September 7, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0

27.1 27.1 27.1 27.0 27.0 27.0 26.5 26.5 26.1 26.0 26.0 26.0 25.7 25.4 24.9 24.9

8.1 8.0 7.8 7.8 7.4 7.4 7.2 6.4 6.1 6.0 5.1 4.0 2.7 0.6 0.1 0.0

8.6 8.6 8.6 8.6 8.5 8.5 8.4 8.1 7.9 7.9 7.9 7.9 7.6 7.6 7.6 7.6

372 370 370 371 370 370 370 370 373 373 375 374 378 378 383 389

4.3 -- -- -- -- -- --

5.0 -- -- -- -- -- -- --

5.2

239 239 239 239 239 239 239 239 241 241 243 243 250 250 258 258

<10 -- -- -- -- -- --

<10 -- -- -- -- -- -- --

<10

0.040 -- -- -- -- -- --

0.040 -- -- -- -- -- -- --

0.040

<0.010 -- -- -- -- -- --

0.020 -- -- -- -- -- -- --

0.015

0.5 -- -- -- -- -- --

1.0 -- -- -- -- -- -- --

1.5

6.0

10

Table 7. Bear Lake water quality parameter data collected over deep basin #2 on September 7, 2018.

Depth (m)

Water Temp

ºC

DO mg L-1

pH S.U.

Cond. µS cm-1

Turb. NTU

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

Chl-a µg L-1

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

27.0 27.0 27.0 27.0 27.0 26.9 26.9 26.8

8.0 8.0 7.2 7.0 6.5 6.5 5.8 5.2

8.6 8.6 8.5 8.5 8.5 8.3 8.3 8.2

370 370 370 370 370 372 372 372

4.8 -- -- --

4.8 -- --

5.0

238 238 238 240 240 240 240 241

<10 -- -- --

<10 -- --

<10

0.030 -- -- --

0.040 -- --

0.050

<0.010 -- -- --

<0.010 -- --

0.020

0.5 -- -- --

0.5 -- --

1.0

6.0

Table 8. Fenner’s Ditch water quality parameter data collected in 2018.

Date Water Temp (°C)

DO mg L-1

pH (S.U.)

Cond µS cm-1

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

May 31, 2018 July 27, 2018

23.7 24.5

7.7 7.1

8.1 8.1

450 453

288 289

<10 <10

0.046 0.040

<0.010 <0.010

0.5 0.5

September 7, 2018 25.6 6.8 8.1 448 285 <10 0.040 <0.010 0.5

Table 9. Bear Creek water quality parameter data collected in 2018.

Date Water Temp (°C)

DO mg L-1

pH (S.U.)

Cond µS cm-1

TDS mg L-1

TSS mg L-1

TP mg L-1

SRP mg L-1

TKN mg L-1

May 31, 2018 July 27, 2018

21.1 22.0

9.0 8.5

7.9 7.9

361 352

231 230

<10 <10

0.044 0.040

0.012 <0.010

0.5 0.5

September 7, 2018 22.6 8.5 8.0 359 231 <10 0.030 0.010 0.5

Dissolved Oxygen

Dissolved oxygen is a measure of the amount of oxygen that exists in the water column. In general, dissolved oxygen levels should be greater than 5 mg L-1 to sustain a healthy warm-water fishery. Dissolved oxygen concentrations may decline if there is a high biochemical oxygen demand (BOD) where organismal consumption of oxygen is high due to respiration. Dissolved oxygen is generally higher in colder waters.

Dissolved oxygen was measured in milligrams per liter (mg L-1) with the use of a calibrated Eureka Manta II® dissolved oxygen meter and multi-probe. During the summer months, dissolved oxygen at the surface is generally higher due to the exchange of oxygen from the

11

atmosphere with the lake surface, whereas dissolved oxygen is lower at the lake bottom due to decreased contact with the atmosphere and increased biochemical oxygen demand (BOD) from microbial activity. Dissolved oxygen concentrations during the May 31, 2018 sampling event ranged from a high of 8.6 mg L-1 to a low of 0.0 mg L-1. Dissolved oxygen declined rapidly beyond a depth of 3.5 meters. On the July 27, 2018 sampling date, the dissolved oxygen concentration ranged from a high of 8.6 mg L-1 among the deep basins to a low of 0.1 mg L-1 which was observed at the bottom of the deepest basin. On the September 7, 2018 sampling date, dissolved oxygen concentrations ranged from 8.1-0.0 mg L-1. The dissolved oxygen concentrations in the inlets were higher than those in the lake.

Water Temperature

A lake’s water temperature varies within and among seasons, and is nearly uniform with depth under the winter ice cover because lake mixing is reduced when waters are not exposed to the wind. When the upper layers of water begin to warm in the spring after ice-off, the colder, dense layers remain at the bottom. This process results in a “thermocline” that acts as a transition layer between warmer and colder water layers. During the fall season, the upper layers begin to cool and become denser than the warmer layers, causing an inversion known as “fall turnover”. In general, shallow lakes will not stratify and deeper lakes may experience single or multiple turnover cycles. Water temperature was measured in degrees Celsius (ºC) with the use of a calibrated Eureka Manta II® thermometer electrode multi-probe. The May 31, 2018 water temperatures of Bear Lake demonstrated a weak thermocline with a temperature difference of 9.3°C in the deepest basin and 5.7°C in the shallower basin. During the July 27, 2018 sampling event, Bear Lake demonstrated a weak thermocline with a temperature difference of 3.3°C in the deepest basin and 1.7°C in the shallower basin. During the September 7, 2018 sampling event, Bear Lake demonstrated a weak thermocline with a temperature difference of 2.2°C in the deepest basin and 0.2°C in the shallower basin. As the water temperatures get warmer throughout the season, the temperatures become less variable from the surface to the lake bottom. Water temperatures in the inlets were slightly lower than in the lake.

Total Phosphorus and Ortho-Phosphorus (SRP)

Total phosphorus (TP) is a measure of the amount of phosphorus (P) present in the water column. Phosphorus is the primary nutrient necessary for abundant algae and aquatic plant growth. TP concentrations are usually higher at increased depths due to higher release rates of P from lake sediments under low oxygen (anoxic) conditions. Phosphorus may also be released from sediments as pH increases. The TP levels in Bear Lake are moderate; however, the dissolved oxygen levels are low enough at the bottom to possibly cause release of phosphorus from the bottom. The TP concentrations on May 31, 2018 ranged from 0.030-0.070 mg L-1, which is above the eutrophic threshold (≤ 0.025 mg L-1). The TP concentrations on July 27, 2018 ranged from 0.030-0.070 mg L-1. The TP concentrations on September 7, 2018 ranged from 0.040-0.050 mg L-1. These concentrations were higher than those measured in the 2017 study and may have been attributed to increased nutrient loading from intense rainfall events noted in 2018. The TP from the inlets ranged from 0.030-0.050 mg L-1 which is

12

similar to concentrations observed in the lake. TP was measured in the laboratory with analytical method EPA 200.7 (Rev 4.4).

Ortho-phosphorus also known as soluble reactive phosphorus (SRP) is the faction of TP that is bioavailable to aquatic biota such as algae. The higher the SRP concentration, the more TP can be used by algae for growth. SRP ranged from <0.010-0.031 mg L-1 which means that there is enough SRP in the water column to support rigorous algal blooms. The SRP concentrations from the inlets ranged from <0.010-0.012 mg L-1 which is favorable. TP was measured in the laboratory with analytical method SM 4500-P (E-11).

Total Kjeldahl Nitrogen

Total Kjeldahl Nitrogen (TKN) is the sum of nitrate (NO3-), nitrite (NO2

-), ammonia (NH4+), and

organic nitrogen forms in freshwater systems. Much nitrogen (amino acids and proteins) also comprises the bulk of living organisms in an aquatic ecosystem. Nitrogen originates from atmospheric inputs (i.e. burning of fossil fuels), wastewater sources from developed areas (i.e. runoff from fertilized lawns), agricultural lands, septic systems, and from waterfowl droppings. It also enters lakes through ground or surface drainage, drainage from marshes and wetlands, or from precipitation (Wetzel, 2001). In lakes with an abundance of nitrogen (N: P > 15), phosphorus may be the limiting nutrient for phytoplankton and aquatic macrophyte growth. Lakes with a mean TKN value of 0.66 mg L-1 may be classified as oligotrophic, those with a mean TKN value of 0.75 mg L-1 may be classified as mesotrophic, and those with a mean TKN value greater than 1.88 mg L-1 may be classified as eutrophic. The TKN concentrations in Bear Lake on May 31, 2018 ranged from 0.5-1.6 mg L-1, which is moderate for an inland lake. The TKN concentrations in Bear Lake on July 27, 2018 ranged from <0.5-2.0 mg L-1. The TKN concentrations in Bear Lake on September 7, 2018 ranged from 0.5-1.0 mg L-1. The TKN of the inlets were all around 0.5 mg L-1, which is favorable. TKN was measured in the laboratory using Method EPA 351.2 (Rev 2.0).

Turbidity and Total Dissolved Solids

Turbidity is a measure of the loss of water transparency due to the presence of suspended particles. The turbidity of water increases as the number of total suspended particles increases. Turbidity may be caused by erosion inputs, phytoplankton blooms, storm water discharge, urban runoff, re-suspension of bottom sediments, and by large bottom-feeding fish such as carp in shallow areas. Particles suspended in the water column absorb heat from the sun and raise water temperatures. Since higher water temperatures generally hold less oxygen, shallow turbid waters are usually lower in dissolved oxygen. Turbidity was measured in Nephelometric Turbidity Units (NTU’s) with the use of a calibrated Lutron® turbidimeter. The World Health Organization (WHO) requires that drinking water be less than 5 NTU’s; however, recreational waters may be significantly higher than that.

The turbidity of Bear Lake was moderate to high and ranged from 4.3-6.9 NTU’s during the sampling events. Spring values would likely be higher due to increased watershed inputs from spring runoff and/or from increased algal blooms in the water column from resultant runoff contributions.

13

Total dissolved solids (TDS) is a measure of the amount of dissolved organic and inorganic particles in the water column. Particles dissolved in the water column absorb heat from the sun and raise the water temperature and increase conductivity. TDS was measured with the use of a calibrated Eureka Manta II® TDS probe in mg L-1. Spring values are usually higher due to increased watershed inputs from spring runoff and/or increased planktonic algal communities. The TDS in Bear Lake ranged from 233-258 mg L-1 for the deep basins during the sampling events, which is moderately high for an inland lake. The preferred range for TDS in surface waters is between 0-1,000 mg L-1 but the lower values are most favorable. The TDS in the inlets ranged from 230-289 mg L-1 which is only slightly higher than lake concentrations.

pH

Most Michigan lakes have pH values that range from 6.5 to 9.5. Acidic lakes (pH < 7) are rare in Michigan and are most sensitive to inputs of acidic substances due to a low acid neutralizing capacity (ANC). pH was measured with a calibrated Eureka Manta II® pH probe. Bear Lake is considered “slightly basic” on the pH scale. The pH of Bear Lake and channel ranged from 7.5-8.6 S.U. during the sampling events which is ideal for an inland lake. Lower pH values were recorded at the lake bottom due to increased microbial activity and respiration which can result in a drop in pH relative to surface waters. All of these values are normal and favorable for aquatic environments. The pH values in the inlets ranged from 7.9-8.1 S.U.

Conductivity

Conductivity is a measure of the amount of mineral ions present in the water, especially those of salts and other dissolved inorganic substances. Conductivity generally increases as the amount of dissolved minerals and salts in a lake increases, and also increases as water temperature increases. Conductivity was measured with a calibrated Eureka Manta II® probe. The conductivity in Bear Lake ranged from 364-385 µS/cm on May 31, 2018 and from 364-380 µS/cm on July 27, 2018 and from 370-389 µS/cm on September 7, 2018. These values are moderate for an inland lake. Severe water quality impairments do not occur until values exceed 800 µS/cm and are toxic to aquatic life around 1,000 µS/cm. The conductivity values for the inlets were slightly higher and ranged from 352-450 µS/cm.

Secchi Transparency

Secchi transparency is a measure of the clarity or transparency of lake water, and is measured with the use of an 8-inch diameter standardized Secchi disk (Figure 3). Secchi disk transparency was measured by lowering the disk over the shaded side of the boat around noon and taking the mean of the measurements of disappearance and reappearance of the disk. Elevated Secchi transparency readings are usually correlated with increased aquatic plant and algae growth. Eutrophic systems generally have Secchi disk transparency measurements less than 7.5 feet due to turbidity caused by excessive planktonic algae growth. Further, elevated phytoplankton and turbidity, also are associated with decreased Secchi transparency. The Secchi transparency of Bear Lake ranged from 2.5-5.2 feet during the 2018 sampling events. This transparency is very poor and may be inadequate to allow abundant growth of aquatic

14

plants in the majority of the littoral (shallow) zone of the lake. Overgrowth of algae may then occur since aquatic plants may not receive enough light for growth and the algae that are abundant in the water column can utilize the nutrients and low light conditions for growth. Secchi transparency is variable and depends on the amount of suspended particles in the water (often due to windy conditions of lake water mixing) and the amount of sunlight present at the time of measurement.

Figure 3. A Secchi disk.

Chlorophyll-a and Algal Species Composition

Chlorophyll-a is a measure of the amount of green plant pigment present in the water, often in the form of planktonic algae. High chlorophyll-a concentrations are indicative of nutrient-enriched lakes. Chlorophyll-a concentrations greater than 6 µg L-1 are found in eutrophic or nutrient-enriched aquatic systems, whereas chlorophyll-a concentrations less than 2.2 µg/L are found in nutrient-poor or oligotrophic lakes. The chlorophyll-a concentrations on May 31, 2018 ranged from 0.534-0.890 µg L-1 and the chlorophyll-a concentrations on July 27, 2018 ranged from 6.0-10.0 µg L-1. The chlorophyll-a concentrations on September 7, 2018 were both 6.0 µg L-1. The late summer concentrations are all quite high and correlate with the observed blue-green algal blooms along with other planktonic green algae in the water column.

The algal genera were determined from composite water samples collected over the deep basins of Bear Lake in 2018 were analyzed with a compound bright field microscope. The genera present included the Chlorophyta (green algae): Cladophora sp., Rhizoclonium sp., Scenedesmus sp., Mougeotia sp., Spirogyra sp., Chlorella sp., Haematococcus sp., Radiococcus sp., Pandorina sp., and Chloromonas sp. The Cyanophyta (blue-green algae): Microcystis sp., and Oscillatoria sp., the Bascillariophyta (diatoms): Synedra sp., Navicula sp., and Synedra sp., and Fragillaria sp. The aforementioned species indicate a somewhat diverse algal flora and represent a good diversity of alga; however, the most dominant algae in the water samples were the blue-green algae Microcystis aueroginosa

15

(Figure 4) and Oscillatoria rubsecens (Figure 5), which are problematic for dense algal blooms that may form toxins and present a risk for public health and the overall health of the Bear Lake ecosystem. Detailed microscopic images were developed from water samples collected on September 13, 2018 which consisted primarily of the blue green algae mentioned above. These blooms were very dense and created mats on the surface of Fenner’s Ditch and near the lake shore in some areas. Microcystis sp. colonies are a few micrometers in diameter and are evenly distributed throughout a gelatinous matrix. Younger colonies are spherical and older ones are more irregularly shaped. There are numerous gas vesicles and the algae can thrive at the surface with minimal photo-degradation (breaking down) by the sun. When the sunlight is excessive, the algae can break down and release toxins and lower the dissolved oxygen in the water column. The algae are the only type known to fix nitrogen gas into ammonia for growth. Microcystis has also been shown to overwinter in lake sediments (Fallon et al., 1981). In addition, it may thrive in a mucilage layer with sediment bacteria that can release phosphorus under anaerobic conditions (Brunberg, 1995). They assume a high volume in the water column (Reynolds, 1984) compared to diatoms and other single-celled green algae. The blue-green algae have been on the planet nearly 2.15 billion years and have assumed strong adaptation mechanisms for survival. In general, calm surface conditions will facilitate enhanced growth of this type of algae since downward transport is reduced. Microcystis may also be toxic to zooplankton such as Daphnia which was a zooplankton present in Bear Lake (along with Bosmina sp.) and in most lakes (Nizan et al., 1986). Without adequate grazers to reduce algae, especially blue-greens, the blue-green population will continue to increase and create negative impacts to water bodies.

References: Brunberg, A.K. 2995. Microbial activity and phosphorus dynamics in eutrophic lake

sediments enriched with Microcystis colonies. Freshwater Biology 33: 541-555. Fallon, R.D., and T.D. Brock. 1981. Overwintering of Microcystis in Lake Mendota.

Freshwater Biology 11:217-226. Nizan, S., C. Dimentman, and M. Shilo. 1986. Acute toxic effects of the Cyanobacterium

Microcystis aeruginosa on Daphnia magna. Limnology and Oceanography 31(3):497-502.

Reynolds, C.S. 1984. The Ecology of Freshwater Phytoplankton. Cambridge University Press, Cambridge, UK.

16

Figure 4. A blue-green algae (Microcystis) bloom on Bear Lake (May, 2018).

Figure 5. A blue-green algae (Microcystis and Oscillatoria rubescens) bloom on Bear Lake (September, 2018).

17

Figure 6. Microscopic image of the blue-green algae (Microcystis) In Bear Lake (September, 2018).

Figure 7. Microscopic image of the blue-green algae (Oscillatoria rubescens) in Bear Lake (September, 2018).

18

Bear Lake Aquatic Vegetation Data (2018)

Status of Native Aquatic Vegetation in Bear Lake

The native aquatic vegetation present in Bear Lake is essential for the overall health of the lake and the support of the lake fishery. A point-intercept aquatic vegetation survey was conducted on Bear Lake on May 31, 2018 and utilized 476 sampling points (Figure 8). A second type of survey was a whole-lake benthic scan which generated an updated lake depth contour map and aquatic vegetation biovolume map.

The whole-lake aquatic plant survey using the GPS Point-Intercept survey method as in Figure 8 below determined that there were a total of 17 native aquatic plant species in the lake. These included 10 submersed species, 4 floating-leaved species, and 3 emergent species. This indicated a good biodiversity of aquatic vegetation in Bear Lake in 2018. The overall % cover of the lake by native aquatic plants is low relative to the lake size due to the great mean depth and thus these plants should be protected unless growing near swim areas at nuisance levels. A list of all current native aquatic plant species and their frequency is shown below in Table 10. Aquatic vegetation biovolume is displayed in Figure 9 below. The blue color represents a lack of aquatic vegetation whereas the green color represents low-growing aquatic vegetation. A red color represents aquatic plants that grow high into the water column such as milfoil or pondweeds. This figure demonstrates that a lot of area in the lake lacks aquatic vegetation.

The most dominant aquatic plant species on May 31, 2018 included: 1) Coontail, which is a rootless aquatic plant that has a brittle feel and reticulated leaves in whorls around a central stem. This plant generally lies on the bottom of the lake but can also be seen floating on the surface after heavy boating activity; 2) Bladderwort, which is a rootless, bright green aquatic plant with clear bladders that are used to trap zooplankton in the water column for food; and 3) Water Stargrass which is a rooted aquatic plant that has multiple shoots off of a horizontal stem. All three species form dense stands but also compete with algae for lake water column nutrients which is why they should not be over-managed.

Section

3

19

Figure 8. Aquatic vegetation sampling points in Bear Lake (May 31, 2018).

20

Table 10. Bear Lake Native Aquatic Plant Species (May 31, 2018).

Native Aquatic Plant Species Name

Aquatic Plant Common Name

Frequency (%)

Aquatic Plant Growth Habit

Chara vulgaris Muskgrass 16.0 Submersed, Rooted

Potamogeton pectinatus Thin-leaf Pondweed 6.3 Submersed, Rooted

Potamogeton zosteriformis Flat-stem Pondweed 0.2 Submersed, Rooted

Potamogeton praelongus White-stem Pondweed 8.3 Submersed, Rooted

Potamogeton richardsonii Clasping-leaf Pondweed 1.0 Submersed, Rooted

Zosterella dubia Water Stargrass 12.0 Submersed, Rooted

Elodea canadensis Common Waterweed 1.0 Submersed, Rooted

Ceratophyllum demersum Coontail 31.0 Submersed, Non-Rooted

Utricularia vulgaris Bladderwort 18.0 Submersed, Non-Rooted

Najas minor Brittle Naiad 6.9 Submersed, Rooted

Nymphaea odorata Whitewater Lily 2.1 Floating-leaved, Rooted

Nuphar variegata Yellow Waterlily 9.0 Floating-leaved, Rooted

Lemna minor Duckweed 2.1 Floating-leaved, Non-Rooted

Wolffia sp. Watermeal 1.4 Floating-leaved, Non-Rooted

Typha latifolia Cattails 6.3 Emergent

Scirpus acutus Bulrushes 5.6 Emergent

Decodon verticillatus Swamp Loosestrife 2.8 Emergent

21

Figure 9. Aquatic vegetation biovolume scan and map of Bear Lake on May 31, 2018 (RLS). NOTE: The blue color represents no vegetation present; Red color represents tall, high-growing aquatic plants; Green color represents low-growing vegetation on the lake bottom such as Chara.

22

Status of Invasive (Exotic) Aquatic Plant Species

The amount of Eurasian Watermilfoil (Figure 10) and Curly-leaf Pondweed (Figure 11) present in Bear Lake varies each year and is dependent upon climatic conditions, especially runoff-associated nutrients. There were intense rainfall events in 2018 that resulted in increased runoff and many lakes experienced nuisance milfoil and algal outbreaks. The May 31, 2018 survey revealed that approximately 20.5 acres of dense milfoil were found throughout the entire lake and were treated by PLM with a granular aquatic herbicide for root-killing control. In addition to the EWM, approximately 3.7 acres of Curly-leaf Pondweed were present and were treated with a contact herbicide since there are no systemics that work on pondweeds. Treatment maps for each of these invasive species are shown in the maps below (Figures 12 and 13). The invasive emergent Phragmites were treated on October 9, 2018 by PLM (Figures 14 and 15).

.

Figure 10. Eurasian Watermilfoil Figure 11. Curly-leaf Pondweed

23

Figure 12. Dense EWM in Bear Lake (May 31, 2018).

Figure 13. Dense Curly-leaf Pondweed in Bear Lake (May 31, 2018).

24

Figure 14. Invasive emergent Phragmites and Purple Loosestrife around the shoreline of Bear Lake (May 31, 2018).

Figure 15. Invasive emergent Phragmites around the shoreline of Bear Lake (May 31, 2018).

25

Bear Lake Sediment Data: Bottom Cores for Petroleum Analysis

RLS scientists collected sediment core samples (Figure 16) in 30 locations (Figure 17) in Bear Lake on July 27, 2018 with the use of a steel sediment coring instrument to determine the distribution and concentrations of petroleum in the lake sediments. Sediment cores were 4 feet in length and the top, middle, and bottom sections of each core were placed into sterile glass collection jars and placed on ice in a cooler prior to being taken to the laboratory for analysis. Samples were analyzed for diesel range organics (DRO), oil range organics (ORO), and sediment organic matter percentage. DRO and ORO were analyzed with analytical method EPA 8015B and the organic matter was analyzed with analytical method ASTM D2974-87. Figure 18 shows core sites that had elevated levels of petroleum in 2018.

Figure 16. A sediment core collected from Bear Lake (July 26, 2018).

Section

4

26

Figure 17. Sediment core sampling sites in Bear Lake (July 26, 2018).

Figure 18. Sediment core sampling sites in Bear Lake that had elevated Concentrations of petroleum (July 26, 2018).

2

1

3

4

5

6

7

8

9

10

1

27

Table 11. Bear Lake sediment core petroleum and organic matter data (July 27, 2018).

28

Management Recommendations for 2019

1. Aquatic Vegetation Surveys: Continuous aquatic vegetation surveys are needed to determine the precise locations of Eurasian Watermilfoil (EWM) Curly-leaf Pondweed (CLP), or other problematic invasives in or around Bear Lake. These surveys should include a whole lake inventory in early to mid-June and again later in the season. In addition, partial surveys post-treatment as needed in 2019. Scientists from RLS will be present to oversee all aquatic herbicide treatments in 2019 as in 2018. 2. Aquatic Herbicide Treatments: Due to the relative scarcity of native aquatic vegetation in Bear Lake, the treatment of these species with aquatic herbicides is not recommended and re-colonization of the lake by these species is a major goal for the health of Bear Lake. Reduction in blue-green algae throughout the lake should also assist with this re-colonization as the plants will have more access to light for continued growth. The plan for 2019 includes the use of high doses of systemic aquatic herbicides (such as triclopyr nearshore and 2, 4-D offshore) for the hybrid milfoil that may be present. Doses will be dependent upon the MDEQ permit requirements as well as the size and density of the weed beds. If Curly-leaf is found at a nuisance level, it could be treated with the contact herbicide Aquathol-K® with great efficacy. If Starry Stonewort is found, then it may be treated with flumioxazin and hydrothol. 3. Lake Water Quality Monitoring: Water quality parameters will be monitored in Bear Lake for 2019 and will include similar identical water quality parameters and also zooplankton that may be required to apply for an MDEQ laminar flow aeration permit. Fenner’s Ditch and Bear Creek will also be sampled for the same water quality parameters. In addition, water quality from the in-flow areas may also be sampled if running and an independent sample can be collected. RLS will use that data to make any necessary recommendations for additional BMPs (best management practices) if needed.

Section

5

29

4. Goose Control:

Throughout the 2018 season, RLS noted that there are an abundance of geese around the parks on Bear Lake (Figure 19). A study by Manny et al. (1994) found that the annual contribution of carbon, nitrogen, and phosphorus from migratory waterfowl including Canada geese (Branta canadensis) can exceed the external loading contributions on some inland lakes. Thus, an overabundance of geese can lead to increased nutrient loads to Bear Lake. Fortunately, there are some strategies for reducing geese populations which include but are not limited to the following: 1. Encourage riparians to grow waterfront grass to ≥ 3 inches tall as geese prefer short

grass. 2. Plant tall native plants near the shore to encourage a soft shoreline that geese may avoid

due to the potential of predators hiding in the tall weeds. 3. Avoid mowing to the water’s edge. 4. Do not feed geese or waterfowl as this encourages their presence. 5. Egg replacement, goose round-up, and nest destruction methods are effective to a

degree but require an MDNR permit and training. 6. Coyote or other intimidating effigies can scare geese away from lawns. 7. The Audubon Society recommends placement of string 6 inches above the ground

followed by another row of string an additional 6 inches above the water. 8. Visit the following website for more methods:

http://icwdm.org/handbook/Birds/CanadadGeese/Default.aspx

Reference: Manny B.A., Johnson W.C., Wetzel R.G. (1994) Nutrient additions by waterfowl to lakes and reservoirs: predicting their effects on productivity and water quality. In: Kerekes J.J. (eds) Aquatic Birds in the Trophic Web of Lakes. Developments in Hydrobiology, vol 96. Springer, Dordrecht. Reference: Canada Goose Management Website. University of Nebraska-Lincoln, NRES 348 Wildlife Damage Management class, Spring Semester, 2010. Scott Hygnstrom, Instructor; Stephen Vantassel, Webmaster.

30

Figure 19. An over-abundance of Canada geese near the shore of an inland lake.

5. Bear Lake Sediment Cores:

RLS will sample additional sediment cores and parameters near the areas previously identified to have elevated petroleum concentrations. Additional analyses that include specific petroleum compound analysis will help determine where the source of petroleum is emanating and the levels that are toxic to Bear Lake aquatic biota. 6. Bear Lake Community Education:

Bear Lake riparians are encouraged to attend regular Bear Lake Board (BLLB) meetings that may held to discuss data trends and evaluate lake improvement progress. Once mitigation strategies are executed in future years, then there will be a need to incorporate different educational strategies into this lake restoration program. RLS proposes to develop an annual lake workshop where new data is presented to the public and new research information is disseminated. Riparian BMP’s and lake protection methods would be openly discussed with attendants. There would be handouts at the workshop with modernized lake maps, water quality graphs, and other updated lake information. Lastly, there would be water quality sampling demonstrations along with key Bear Lake biota present in the lake available for learning.

31

7. Laminar flow aeration and bioaugmentation

Laminar flow aeration systems (Figure 20) are retrofitted to a particular lake or water body and account for variables such as water depth and volume, bottom contours, water flow rates, and thickness and composition of lake sediment. The systems are designed to completely mix the surrounding waters and evenly distribute dissolved oxygen throughout the lake sediments for efficient microbial utilization. A laminar flow aeration system utilizes diffusers which are powered by onshore air compressors. The diffusers are connected via extensive self-sinking airlines which help to purge the lake sediment pore water of gases such as hydrogen sulfide (H2S) which gives lake sediments a “rotten egg” odor. In addition to the placement of the diffuser units, the concomitant use of bacteria and enzymatic treatments to facilitate the microbial breakdown of organic sedimentary constituents is also used as a component of the treatment. Beutel (2006) found that lake oxygenation eliminates release of NH3+ from sediments through oxygenation of the sediment-water interface. Allen (2009) demonstrated that NH3+ oxidation in aerated sediments was significantly higher than that of control mesocosms with a relative mean of 2.6 ± 0.80 mg N g dry wt. day-1 for aerated mesocosms and 0.48 ± 0.20 mg N g dry wt. day-1 in controls. Although this is a relatively new application to inland lakes, recent case studies have shown promise on the positive impacts of laminar flow aeration systems on aquatic ecosystem management with respect to organic matter degradation and resultant increase in water depth, and increase in water clarity and decrease in blue-green algae and excessive filamentous green algae in eutrophic ecosystems (Jermalowicz-Jones, 2010-2018, various restoration case studies). Toetz (1981) found evidence of a decline in Microcystis algae (a toxin-producing blue-green algae) in Arbuckle Lake in Oklahoma. Other studies (Weiss and Breedlove, 1973; Malueg et al., 1973) have also shown declines in overall algal biomass. The philosophy and science behind the laminar flow aeration system is to reduce the organic matter layer in the sediment so that a significant amount of organic nutrient is removed from the sediments and excessive sediments are reduced to yield a greater water depth. Nutrients in the water column are also reduced which decreases algae. Limitations of Laminar Flow Aeration The laminar flow aeration system has some limitations including the inability to break down mineral sediments and the requirement of a constant Phase I electrical energy source to power the units. Regular equipment maintenance is also required.

32

Design of the Laminar Flow Aeration System The design of a laminar flow system would be retrofitted to Bear Lake. The system has several components which consists of in-water components such as micro-porous ceramic diffusers, self-sinking airline, and bacteria and enzyme treatments. Once the system has been installed, the MDEQ requires a robust sampling protocol to monitor the efficacy of the system for the intended purposes as determined by stakeholders and to assure that no harm is caused by the system on lake health. Recommendations for Laminar Flow Aeration Implementation Due to the high quantity of blue-green algae and low bottom dissolved oxygen concentrations in Bear Lake, the use of aeration with bioaugmentation (addition of microbes) is recommended. The addition of microbes may also aid in the reduction of sediment petroleum which may be limiting the sediment macroinvertebrate community and overall lake health. The aeration technology has demonstrated significant reductions in sediment ammonia and ammonia nitrogen (Jermalowicz-Jones and Horne, 2018; manuscript in progress). This nutrient is an excellent food source for submersed aquatic plants and is also produced by blue-green algae that can fix nitrogen gas.

Figure 20. A diagram showing the laminar flow aeration mechanisms. ©Restorative Lake Sciences, LLC