Lakes, Lake Winnipeg, Eutrophication and Aquatic Invasive Species

Question 1

What are the key differences between oligotrophic and eutrophic lakes?

Answer 1

Oligotrophic – low nutrients, clearer water, light penetrates deeper, often look blue.
Eutrophic – high nutrients, murkier water, light cannot penetrate as deep, often look green

Question 2

What is a watershed?

Answer 2

An area of land that drains water into a specific waterbody, such as a stream, river, lake, or ocean

Question 3

Do rivers and streams have more nutrients at their source or downstream? Why?

Answer 3

They’re nutrient poor at their source (glacial melt water), but can pick up more sediments and nutrients the further they flow.

Question 4

Are lakes affected by changes to their surrounding landscapes?

Answer 4

YES

Question 5

What happened to the lakes after the surrounding landscape was clearcut in the Hubbard Brook Experimental Forest?

Answer 5

Significantly more nutrients from the land washed into the lake. These nutrients often need to be replaced by fertilizer, which also runs off into the surrounding waters.

Question 6

What is the lifecycle of mineral nutrients (and the elements in them)?

Answer 6

They’re weathered from rocks into rivers to the ocean. Precipitate out into ocean sediments which are compressed by their own weight, become rocks and may become land again via geological upheavals (or volcanic activity).

Question 7

What is a dimictic lake?

Answer 7

di = 2, mictic = mixed.
A lake that overturns two times a year in the spring and fall when the water is 4°C (remember stratification from chapter 35?).

Question 8

What three things impact the nutrient status and trophic classification of a lake?

Answer 8

The surface catchment – its geology, terrestrial ecosystems, and land use.

Question 9

What is a lake’s morphometry?

Answer 9

The shape, depth, length, and width of the lake.

Question 10

Are lakes a permanent feature of the landscape?

Answer 10

Not really. Each has an origin, a history, and will eventually disappear.

Question 11

What is eutrophication?

Answer 11

The natural nutrient enrichment of lakes over time, mostly from runoff of plant nutrients. Lakes naturally become more eutrophic (nutrient rich) as they age.

Question 12

What is cultural eutrophication?

Answer 12

The acceleration of eutrophication by human activities that add plant nutrients to a lake.

Question 13

Do freshwater or marine ecosystems experience cultural eutrophication?

Answer 13

Both.

Question 14

What are some sources of nutrients that contribute to cultural eutrophication?

Answer 14

Treated and untreated sewage, pollution from cars and factories, fertilizer runoff, manure runoff, run off from streets and lawns, runoff from mining and construction, natural runoff, etc.

Question 15

What is the trophic status of a lake and how is it usually measured?

Answer 15

Trophic status describes the productivity (amount of biomass) in a lake. Usually based on total phosphorus, nitrogen or chlorophyll a concentrations.

Question 16

What is a limiting nutrient?

Answer 16

A nutrient that restricts potential growth. Something an organism cannot grow without.

Question 17

What does Liebig’s Law of the Minimum tell us about the growth of biological organisms?

Answer 17

Growth is usually limited by only one nutrient at a time. Growth is dictated not by total resources available, but by the scarcest resource.

Question 18

What is usually the most limiting nutrient in lakes?

Answer 18

Phosphorus

Question 19

Which nutrient tends to be most limiting for phytoplankton (algae) in freshwater aquatic ecosystems?

Answer 19

Phosphorus

Question 20

What is biogeochemical cycling?

Answer 20

The movement of nutrients/chemicals through abiotic and biotic compartments of the ecosystem (i.e. organisms, the atmosphere, the earth’s crust).

Question 21

Where is phosphorus naturally found in the phosphorus cycle? Where do humans contribute additional phosphorus?

Answer 21

In rocks, ocean sediments, dissolved in water, and in the bodies of organisms.
Mining waste, sewage and fertilizers.

Question 22

Lake Winnipeg is the ____th largest lake in the world but surface area and ____ largest by volume.

Answer 22

Lake Winnipeg is the 10th largest lake in the world by surface area and 21st largest by volume.

Question 23

What is a lake’s residence time? What is Lake Winnipeg’s residence time? What about Lake Superior’s?

Answer 23

How long it takes for one water drop to get out of the lake.
Lake Wpg. = 3.5 years
Lake Superior = 191 years

Question 24

Lake Winnipeg has the _____ largest watershed in Canada that is nearly _________ km2.

Answer 24

2nd largest.
Nearly 1 million km2.

Question 25

How many primary inflows does Lake Winnipeg have? How many outlets?

Answer 25

3 inflows: the Winnipeg River, Saskatchewan River and Red River (from biggest to smallest). 1 outlet: the Nelson River.

Question 26

The Red River contributes about ____% of the water flowing into Lake Winnipeg but it contributes approximately ___% of the phosphorus entering the system.

Answer 26

16% of inflowing water. 68% of the phosphorus.

Question 27

What are two unique features of Lake Winnipeg that may reduce the negative effects of nutrients on the system?

Answer 27

It's relatively shallow and very large (lot of waves/mixing which reduces dead zones due to a lack of oxygen). It has a relatively low residence time, just 3.5 years.

Question 28

What are some big problem that Lake Winnipeg is facing (5)?

Answer 28

Large and toxic algal blooms, invasive zebra mussels and spiny water flea, potential for overfishing, climate change and contaminants.

Question 29

What is Lake Winnipeg Regulation (LWR) and what does it do?

Answer 29

A dam and channels that regulate outflow to reduce shoreline flooding and erosion, and reduce peak/minimal water levels within the lake. Also manages water for power generation on the Nelson River.

Question 30

What is the Experimental Lakes Area?

Answer 30

A designated area of Ontario containing dozens of lakes set aside for research on water pollution.

Question 31

What experiment was done in lake 226?

Answer 31

Lake 226 was divided by a curtain. Carbon and nitrogen were added to both sides. Phosphorus was only added to one side. The P side had an algal bloom.

Question 32

What experiment was done in lake 227?

Answer 32

They added phosphorus and nitrogen to the lake which caused an algal bloom. They experimented with P and N ratios before only adding P. It's been years and the algae is still there.

Question 33

Why can’t removing nitrogen solve the algal bloom problem?

Answer 33

Cyanobacteria (that cause algae) can fix atmospheric nitrogen (pull it out of the air and make it bioavailable). So if they don't get N in the water they'll just get it out of the air.

Question 34

What can certain species of cyanobacteria do that most other phytoplanktonic organisms cannot?

Answer 34

They can fix atmospheric nitrogen (pull it out of the air and make it bioavailable).

Question 35

Name 5 (or more) factors that contribute to the cultural eutrophication of Lake Winnipeg.

Answer 35

Increased city runoff, increased levels of inflow (especially from the Red R.), poor sewage treatment in Wpg., runoff from fields in spring, fertilizers, manure, tile drainage systems, draining wetlands, poor health of Netley Libau Marsh, climate change causing "flashier" precipitation and exacerbating algal blooms, internal cycling of nutrients keeps P in the lake even when its not being added.

Question 36

According to recent research by the Lake Winnipeg Foundation, when does most of the phosphorus enter the lake?

Answer 36

In the spring during the spring thaw and after major rains

Question 37

Some evidence shows that about ___% of phosphorus loading to the Lake Winnipeg system occurs in the ________ (season).

Answer 37

98% in the spring.

Question 38

List 5 effects of algal blooms on lakes.

Answer 38

Unsightly and produce toxins; reduce water usability; reduce property values; cause anoxic conditions and potentially fish kills; change phytoplankton biomass and species composition (more toxic, cyanobacteria species).

Question 39

How can algae lead to oxygen depletion?

Answer 39

Algae gets overgrown, the algae die, and sink to the bottom. They are decomposed by bacteria, which can remove oxygen from the water.

Question 40

Name 3 reasons for the poor condition of the Netley Libau Marsh at the south end of Lake Winnipeg.

Answer 40

The Netley Cut (tried to drain the marsh, flooded it instead); introduction of common carp (dig up plants and sediments), and higher water levels preventing the marsh from reseeding.

Question 41

List a few steps we could take to help reduce the eutrophication problem in Lake Winnipeg? Try naming 4.

Answer 41

Keep water on the land, protect and rebuild wetlands. Conserve the boreal forest. Better wastewater treatment. Better monitoring. Managing shorelines, restore shoreline habitats. Better agricultural practices. Investing in a clean water economy, encourage regulations and innovate technologies. Taking responsibility, spread awareness, demanding better from govs.

Question 42

What makes a species invasive?

Answer 42

Any animals, plants, parasites, and diseases that are not native to an area. Out-compete native species for resources and tend to have zero or few natural predators.

Question 43

What is the primary way that aquatic invasive species are spread to new waterways?

Answer 43

Movement of recreational watercraft and water-based equipment from affected to non-infected water bodies.

Question 44

Name 4 aquatic invasive species in Manitoba.

Answer 44

Common carp, spiny waterfleas, rusty crayfish, and zebra mussels.

Question 45

Zebra mussels are different from all of our native mussels because they attach to hard surfaces using _______ _______.

Answer 45

Byssal threads.

Question 46

One female zebra mussel can produce up to _______ eggs per year.

Answer 46

1 million

Question 47

What form do zebra mussels take have hatching out of eggs? How long do they stay in this form?

Answer 47

Free-floating veligers (microscopic larvae) for 2-3 weeks before forming a shell and attaching to a substrate.

Question 48

What are 6 impacts that zebra mussels have had on infested lakes?

Answer 48

Increased water clarity, aquatic vegetation growth and toxic algal blooms. Altered food webs. Decrease in fish and native mussel populations. Reduced recreational potential. Clogged structures. Increased drag on watercraft. Cost millions to deal with every year.

Question 49

When and where in Canada (which lake) were zebra mussels first discovered?

Answer 49

1986 in Lake Erie, brought in ballast water of ships from Europe.

Question 50

What do you have to do with a boat, watercraft or water toys to prevent transfer of zebra mussels from one location to another?

Answer 50

**CLEAN** (remove plants, invasive species, mud and rinse with very hot water), **DRAIN** all water, **DRY** all water related equipment and **DISPOSE** of unused bait.