Limnology 101 an Introduction to Lake Science

Limnology 101 An Introduction to Lake Science

10 August 2017 Prairie Lakes Conference

John C. Holz, PhD Senior Limnologist LIMNOLOGY DEFINED

• Limnology (from Greek limne, “lake” and logos, “knowledge”) is the study of inland waters.

• Covers geological, physical, chemical and biological attributes of land-bound freshwater and saline systems, including:

• Lakes • Ponds • Impoundments • Rivers • Streams • Wetlands

2 THE WATERSHED

penntwplanco.org USGS HUC8 Watershed Boundaries

• Section of land where all water runoff flows to a common basin

• Runoff carries nutrients, sediment and pollutants

• Runoff affected by slope, geology, soils and land use

3 THE TALE OF TWO WATERSHEDS

Lake Michell, SD Five Island Lake, IA WS:L = 524:1 WS:L = 9:1

4 LAKE FORMATION & BASIN TYPES

• Hutchinson identified 76 ways lakes may form

• Including: earthquakes, volcanos, oxbows, glaciers, faults in the Earth’s crust

• Lake formation affects lake size, shape, depth and watershed characteristics

NASA Crater Lake, OR

5 GLACIAL LAKES

6 GLACIAL LAKES

Most Midwestern Lakes were formed over 10,000 years ago

*D. Lusch, MSU 7 OXBOW LAKES

Carter Lake, IA Lake Manawa, IA

8 IMPOUNDMENTS

Lake Wanahoo, NE

9 IMPOUNDMENTS VS. NATURAL LAKES

Impoundments Natural Lakes Shoreline Astatic Stable Water Level Large fluctuations Natural Littoral Zone Irregular Stable Flushing Rate High Low Sedimentation Rate High Low Nutrient Loading High & variable Low & stable Turbidity High Low Stratification Irregular Natural

10 THERMAL STRATIFICATION

• Maximum density = 3.94 oC • Ice at 0 oC is 8.5% less dense that water at 0.1 oC • Water above 3.94 oC gets less dense as it warms • Surface water is warmer than deep water in the summer (thermal stratification)

11 THERMAL STRATIFICATION & MIXING

quia.com

• Dimictic vs. Polymictic Lakes

12 THERMAL STRATIFICATION & OXYGEN

quia.com • Photosynthesis

CO2 + H2O + nutrients + light glucose + O2

• Respiration

glucose + O2 CO2 + H2O + energy

13 NUTRIENTS

• Limiting Nutrient Concept: The nutrient in short supply relative to others will be exhausted first and limit cellular growth

• Phosphorus (P) is an essential element and is the most common limiting nutrient in lakes

• Excessive concentrations of P is a key driver of a variety of lake water quality problems

14 NUTRIENT SOURCES

External Loading

Internal Loading

15 EXTERNAL NUTRIENT SOURCES

Septic Systems Lawn Fertilizers Agriculture

COW

Stormwater Livestock

16 INTERNAL NUTRIENT SOURCES

Dissolved P Loading Sediment Coring: Five Island Lake, IA

17 INTERNAL NUTRIENT SOURCES

Jet Ski: Carter Lake, IA

Particulate P Loading

Common Carp

18 LAKE FOOD CHAIN

• Bass, pike, walleye

• Minnows, YOY sunfish, alewife

• Daphnia, copepods, rotifers

• Diatoms, green algae, cyanobacteria

• Phosphorus

• Common Carp, Buffalo

19 PHYTOPLANKTON (ALGAE)

• Microscopic plants • Base of food chain

• Produce O2 • Chlorophyll pigment gives green color • Groups often differentiated by color • Too many cause problems • Require phosphorus for production of adenosine triphosphate (ATP) • Transports chemical energy within cells for metabolism • Growth limited by phosphorus

Vollenweider (1968)

20 PHYTOPLANKTON (ALGAE)

Green Algae Diatoms

Cyanobacteria (aka Blue-green algae)

21 WATER QUALITY CHALLENGES

Algal Blooms Algal Toxins Low Clarity

Fish Kills Recreation/Property Value Declines

22 ZOOPLANKTON

• Tiny, free-floating invertebrate animals • Feed on algae and bacteria • Important food source for planktivores • Most are transparent (camouflage) • Can increase population size by 30% in a day • Lifespan of up to 30 days Copepod

Rotifer Daphnia

23 PLANKTIVOROUS FISH

• Feed on zooplankton • Different species feed on different sized zooplankton • Food source for piscivorous fish

24 LAKE FOOD CHAIN

• Bass, pike, walleye

• Minnows, YOY sunfish, alewife

• Daphnia, copepods, rotifers

• Diatoms, green algae, cyanobacteria

• Phosphorus

• Common Carp, Buffalo

25 TROPHIC CLASSIFICATION

26 SHALLOW LAKE ECOLOGY

Plant-Dominated State Algae-Dominated State

• Shallow lake water quality controlled by both nutrients and rough fish • Alternate Stable State theory predicts two lake conditions • A management approach is to control both phosphorus and rough fish density

27 QUESTIONS?

Dr. Ben Maas, BVU