Lake Ecology Flashcards
1
Q
What are some of the factors that contribute to the chemical and biological condition of a lake?
A
How it was formed, size and shape of the basin, size and topography of its watershed, regional climate, local biological communities, and activities of humans in the past century.
2
Q
What is a watershed?
A
An area of land containing a particular river or lake and all the tributaries that flow into it.
3
Q
What are the three major areas of the United States with lakes?
A
Limestone sinkholes in Florida, mountain lakes of the Pacific Northwest, and glaciated landscapes of the Great Lakes region.
4
Q
How many lakes are there in Minnesota?
A
12,034
5
Q
What do scientists use to study a lake’s physical, chemical, and biological history?
A
The sediment
6
Q
How do scientists date lake sediment?
A
Radioisotopes: They examine how much the isotope has decayed.
7
Q
What can a large increase in pollen within the sediment of a lake signify?
A
Changes in the plant life, especially increases or decreases.
8
Q
True or false, lakes are mostly the same throughout their space.
A
False.
9
Q
How do lakes vary physically?
A
Light levels, temperatures, and water currents.
10
Q
How do lakes vary chemically?
A
Nutrients, major ions, and contaminants.
11
Q
How do lakes vary biologically?
A
Structure, function, biomass, population numbers, and growth rates.
12
Q
Why is light so important in a lake ecosystem?
A
It allows plants to photosynthesize, which provides food and regulation for the entire ecosystem. It also determines the temperature of the lake
13
Q
What affects how deep light can penetrate in a lake?
A
The amount of light-absorbing dissolved substances in the water.
14
Q
When is the temperature of a lake most constant?
A
Right after the spring melt.
15
Q
True or false, water is more dense as a solid.
A
False.
16
Q
Water quality of a lake decreases as its watershed area gets larger, why is this?
A
There is a greater chance that precipitation and runoff will leach more minerals and contaminants into the lake.
17
Q
What are lakes that have very small watersheds and rely mostly on groundwater called?
A
Seepage lakes.
18
Q
What are lakes that are fed primarily by inflowing rivers called?
A
Drainage lakes.
19
Q
Do seepage or drainage lakes have better water quality?
A
Seepage.
20
Q
Why are seepage lakes more vulnerable to acidification?
A
They have a low buffering capacity.
21
Q
What is buffering capacity?
A
The ability of a solution to resist changes in PH.
22
Q
Why are there so many contaminants in urban lakes?
A
Impenetrable surfaces keep water from going into the soil and they instead flow over and into the lake. Also, the high flushing rate cases large particles from the watershed to be moved into the lake.
23
Q
What is a flushing rate?
A
The amount of time water spends in a lake.
24
Q
What causes lakes to separate into three different layers?
A
Temperature.
25
Where do most ions and molecules come from in a lake?
The weathering of the soils in the watershed, the lake bottom, and the atmosphere.
26
The chemical composition of a lake is a function of it's what?
Climate and basin geology.
27
How does excessive landscape development effect lake and watershed ecology?
It removes vegetative cover, exposes soil, and increases water runoff velocity.
28
What are micronutrients?
Nutrients required by microorganisms.
29
Why is mercury so dangerous in aquatic ecosystems?
It bioaccumultes across the food web, poisoning organisms and making them unsafe to eat.
30
What is acid rain?
Rain with a pH value of lower than 5.2
31
What does acid rain generally contain?
Sulfur and nitrogen acids.
32
What causes acid rain?
Industrial and other human emissions.
33
What is a hardwater lake?
A lake with a high buffering capacity.
34
What ions do hardwater lakes have high concentrations of?
Calcium and magnesium.
35
what is a softwater lake?
A lake with a low buffering capacity.
36
What influences a lakes ability to assimilate pollutants and maintain nutrients?
Ionic concentrations.
37
What is the TDS and what does it stand for?
It is the total amount of ions in the water and stands for Total Dissolved Salt.
38
What does the TDS dictate?
The chemical reactions that occur in the lake and the species that can survive there.
39
Why is lake superior safe from the infestation of exotic zebra mussels (which are drastically changing the ecosystem of lake Erie)?
Because it has a low calcium concentration and the zebra mussel requires higher calcium concentrations.
40
When does biological activity peak in a lake and why?
It peaks during the spring and summer because that is when photosynthetic activity is at its highest.
41
What is the winter kill and why does it happen?
The winter kill is when many fish die during the winter. It happens when ice covers the lake for a long time and little to no photosynthesis occurs.
42
What do aquatic organisms influence (and are influenced by)?
The chemistry of the surrounding environment.
43
When do nutrients such as phosphorous increase in a lake ecosystem?
In the spring (due to snowmelt runoff).
44
What can a new nutrient added during the spring months result in?
An algal bloom.
45
Where can nitrogen and phosphorous come from?
Dust, soil particles, and fertilizer runoff.
46
What created most of the lakes in Minnesota and how long ago were they formed?
Glaciers formed the lakes 12,000 years ago.
47
How do glaciers form lakes?
They gouge holes in soft soil and bedrock or deposit ice that melts and becomes lake basins.
48
How does sediment get into a lake?
They wash in from tributaries or are created by decomposing organic material.
49
What is the study of lake sediments?
Paleolimnology.
50
What three things can be deduced by analyzing diatom abundance and composition?
Lake acidity, water clarity, and algal productivity.
51
What tool is used to estimate water clarity?
A Secchi disk.
52
What does the most fundamental properties of lakes relate to?
The interactions of light, temperature, and wind mixing.
53
What is the role of photosynthesis in a lake?
It provides the food that supports most of the food web. It also is responsible for much of the dissolved oxygen in the water.
54
How does solar radiation affect a lake?
It warms the water column and is a major factor in deciding wind patterns and water movements.
55
What does a lake's K value denote?
How deep light can penetrate.
56
What determines the maximum depth at which algae and macrophytes can grow?
Light levels.
57
What is a macrophyte?
An aquatic plant that grows in or near water.
58
What is the euphotic zone?
The layer of a lake where light is sufficient enough for photosynthesis to occur.
59
What kinds of effects will changes in light penetration in a lake cause?
Direct and indirect biological and chemical effects.
60
What most often causes changes in lake transparency?
Landuse activities.
61
Does a higher or lower K value mean a lake is clearer?
Lower.
62
At what temperature is water most dense?
4 degrees Celsius.
63
What is turnover?
Fall cooling and spring warming of surface water act to make density uniform throughout the water column.
64
What does turnover help to accomplish?
It allows wind and wave action to mix the entire lake.
65
What are the three layers of deep lakes?
The epilimnion, the metalimnion, and the hypolimnion.
66
What is a polymictic lake?
Lakes that stratify and destratify multiple times over a summer.
67
What is the stagnant fourth layer of a meromictic lake?
The monimolimnion.
68
What are some traits of the monimolimnion?
It is anaerobic and has a high concentration of dissolved solids.
69
What is a meromictic lake?
A lake that never mixes completely.
70
What can cause a lake to become meromictic?
Being sheltered from the wind and being very deep for their size.
71
What is another name for the watershed?
The drainage basin.
72
What does a lake reflect in regards to its watershed?
The size, topography, geology, landuse, soil feritility, soil erodibility, and vegetation.
73
What can finer particles and steeper slopes mean?
Higher export rates of a certain nutrient or contaminant.
74
Will a forest or urban area put more phosphorous into a lake?
Urban.
75
What does ion balance in a lake mean?
The sum of the positive cations equals the sum of the negative anions.
76
What will highways and parking lots leach into the water of a lake?
Oils and heavy metals.
77
What layer of a lake has the most dissolved oxygen?
The epilimnion.
78
What is the difference between oligotrophic and eutrophic lakes?
Eutrophic lakes are productive, oligotrophic lakes are not.
79
What is anoxia?
The lack of oxygen.
80
What is the zone in a lake near the shore where sunlight penetrates all the way to the sediment and allows macrophytes to grow?
The littoral zone.
81
What is the euphotic zone?
It is the area where light is sufficient for photosynthesis to take place, but in the middle of the lake.
82
What layer of a lake contains the euphotic zone?
The epilimnion.
83
True or false, in some special cases where the water is especially clear, sunlight can penetrate the hypolimnion.
True.
84
What does the littoral zone provide a habitat for besides the plants that photosynthesize there?
Fish, algae, and invertebrates.
85
Why aren't algae considered plants?
Algae are not considered plants because they lack roots, leaves, or stems.
86
What is the zone of the lake that contains the sediment and a variety of organisms that feed on the bottom?
The benthic zone.
87
What kind of organisms are most abundant in the benthic zone?
Invertebrates.
88
What does the productivity of the benthic zone rely on?
The organic content of the sediment, the amount of physical structure, and the rate of fish predation.
89
Why is sand a bad thing to have at the bottom of a lake?
It is nutrient deficient and unstable.
90
Why are rocky bottoms generally best for invertebrates?
They allow invertebrates to hide and better protect themselves from predators.
91
What is detritus?
Dead or decaying organic matter.
92
What is periphyton?
Algae that has attached itself to things.
93
Are plants and algae producers or consumers?
Producers.
94
True or false, animals do not change their diets throughout their life cycle.
False.
95
What do food chains and food webs help us to understand?
How the ecosystem functions.
96
What is a producer?
An organism that gets energy by absorbing sunlight.
97
What is a decomposer?
An organism that obtains energy by breaking down others into nutrients.
98
What is the ecological pyramid?
A pyramid depicting the organization of organisms within an ecosystem.
99
What are the two life-sustaining processes?
Respiration and photosynthesis.
100
What is the waste product of photosynthesis?
Oxygen.
101
How do plants grow?
They use energy obtained from sunlight to convert nonliving substances like water and carbon dioxide into living plant tissue.
102
Where does carbon dioxide come from in a lake?
The weathering of rocks, diffusion from the atmosphere, and from the respiration of consumers.
103
True or false, a clean lake does not have very much nitrogen or phosphorous in it.
True.
104
What are some minerals that are necessary to life?
Iron, calcium, magnesium, cobalt, sulfur, sodium, potassium, boron, copper, and zinc.
105
What special mineral is required by diatoms and some algae?
Silicon.
106
What is the group of animals that eat the herbivores called?
Secondary consumers.
107
What is another name for an herbivore?
A primary consumer.
108
What is respiration?
The oxidation of organic material.
109
What are the two forms of detritus?
Pieces of plants and animals or dissolved organic matter.
110
What is primary productivity?
The productivity of producers within an ecosystem.
111
What is the single greatest threat to lake ecosystems?
The increase of nutrients, which results in overpopulation of primary producers.
112
Why do plants need oxygen?
They respire at night.
113
How do plants produce energy when there is no sunlight?
They burn sugars, but create more than they burn due to photosynthesis.
114
Why are algal blooms harmful?
They block sunlight, deplete oxygen, and can sometimes release harmful chemicals.
115
What, besides lack of sunlight, can result in a lack of macrophytes in a body of water?
Bottom is too rocky or sandy, wave action is too severe, water is too deep.
116
True or false, there are only a few kinds of algae and they are not very adaptable.
False.
117
True or false, algae make up most of the phytoplankton.
True.
118
What plant pigment transforms light energy into chemical energy for photosynthesis?
Chlorophyll.
119
What type/color of algae is most closely related to plants?
Green algae.
120
What pigment is found in all colors/types of algae?
Chlorophyll.
121
What are diatoms?
Algae with silica cell walls.
122
Where are diatoms usually found?
They are usually stuck to things.
123
What color/group of algae do diatoms and dinoflagellates belong to?
Brown algae.
124
How do dinoflagellates move?
They have flagella.
125
What kinds of algae contain special pigments that allow them to photosynthesize in very low light?
Cryptomonads.
126
Why are blue-green algae sometimes called cyanobacteria?
Barring their ability to photosynthesize, they are bacteria.
127
What kind of algae are the most common nuisance bloomers?
Blue-green.
128
Can blue-green algae regulate their buoyancy?
Yes. They can move up and down the water column at will.
129
Why are blue-green algae so dominant?
They have a special ability to use molecular nitrogen (nitrogen fixation) which depletes nitrogen from the surrounding atmosphere and allows them to overwhelm other species. They also taste bad and are hard for grazers to eat. Their ability to regulate their buoyancy also allows them to rise above other forms of algae.
130
What are the three types/colors of algae?
Green, blue green, and brown.
131
Due to the fact that most experts cannot identify every species of algae, what are many algae called if their identity is not necessary?
LRGTs. (Little round green things)
132
How are concentrations of chlorophyll-a measured in a lake?
Water is siphoned through a fine glass filter and then chlorophyll particles are extracted using a solvent like acetone or alcohol.
133
True or false, secchi depth is the harder and more expensive way of finding algal concentrations within a lake.
False.
134
Why must care be taken when using a secchi disk to determine algal data?
It can be influenced by non-algal particulate material.
135
Why is it important to sometimes study the lake's algal communities on a microscopic level?
Because the mix of species can influence lake management decisions.
136
What determines a lake's biological characteristics?
The physical characteristics of the water column.
137
Why do the types of algae go through different seasons of succession?
Changing conditions can allow for some species to die off while others bloom.
138
Are larger plants and animals affected by changing seasons like algae are?
No.
139
What and how do clams eat?
They filter small bits of organic material as it floats by.
140
What is the main job of most benthic organisms?
They are recyclers of nutrients trapped in the sediment and decomposers.
141
What are the tertiary consumers?
The consumers that eat the smaller fish like humans, ospreys, pikes, and loons.
142
What do smaller fish primarily eat?
Zooplankton.
143
What habitats are suited for bass and pike?
Lake beds that have macrophytes that are suitable for spawning.
144
Where do lake trout live?
Clear lakes with cold, well-oxygenated, deep water.
145
What kinds of nutrients result from the work of decomposers?
Phospohrous, nitrogen, and carbon dioxide.
146
How does the release of carbon dioxide by the decomposers help the deep-water ecosystem?
It acts to lower the pH of bottom waters.
147
What is carbon released as in anoxic zones?
Methane.
148
Where are decomposers the dominant life forms and why?
They are dominant in the lower hypolimnion because there is an abundance of dead matter.
149
Why is the hypolimnion often anoxic?
The decomposition done by the decomposers depletes oxygen and there are no plants to create oxygen or ways for atmospheric oxygen to mix into the hypolimnion (due to stratification).
150
What are the two most common decomposers?
Bacteria and fungi.
151
What have lakes been classified by since the early 20th century?
Their trophic state.
152
What is a mesotrophic lake?
A lake that falls in between eutrophic and oligotrophic.
153
What three factors contribute to the trophic state of a lake?
Rate of nutrient supply, climate, and shape of lake basin.
154
What affects the rate of nutrient supply in a lake?
Bedrock geology of the watershed, soils, vegetation, and landuse activities.
155
What affects the climate of a lake?
Temperature, amount of sunlight, precipitation, and turnover time.
156
What kinds of soils do oligotrophic and mesotrophic lakes have?
Infertile soil with little nitrogen and phosphorous.
157
What kinds of soils do eutrophic lakes have?
Enriched soils filled with many nutrients.
158
What is eutrophication?
The progress of a lake toward a eutrophic condition.
159
True or false, a young lake is often eutrophic.
False. Older lakes are generally more eutrophic.
160
Why do geological events often create oligotrophic lakes?
The landscapes surrounding lakes are often infertile.
161
How did oligotrophic lakes begin becoming fertile?
The dead denizens of shoreline colonies decomposed and helped to create fertile sediment. then active colonies began to establish themselves in the lake and make it shallower and more eutrophic as more organic matter accumulated at the bottom.
162
Why do shallow lakes tend to be more productive?
They do not stratify, which allows nutrients to remain in circulation and become accessible by plants. Nutrient loading from the watershed also has a greater effect.
163
What can cause some exceptions to the rule that lakes begin oligotrophic and become eutrophic?
Geology, topography, and lake morphology.
164
True or false, some lakes have remained oligotrophic for millions of years.
True. (Lake Tahoe is an example)
165
Will lakes always follow the ideal pattern where they become more and more eutrophic with age?
No. Studies of sediments of the Minnesota lakes suggests that productivity has fluctuated many times over the past 12 - 14,000 years.
166
What is glaciation?
The process of being covered by glaciers or ice sheets. It can also refer to a period where an area is covered by glaciers.
167
How long ago was the last glaciation in the Great Lakes region?
12 - 14,000 years
168
What is thought to have changed the productivity of the Great lakes so much?
Constant changing of the tributaries and stream flow, glacial retreat, and decreases in nutrient supply.
169
What was the most famous "dead" lake in the 60s?
Lake Erie.
170
How was Lake Erie resurrected?
Advanced wastewater treatment plants were built.
171
Why is hyper-eutrophication a problem?
Species diversity decreases, plant and animal biomass decreases, turbidity increases, rate of sedimentation increases, and anoxic conditions develop.
172
What is turbidity?
A measure of the clarity of a lake.
173
What is the major source of water pollutants in the US today?
NPS (non-point sources)
174
What are non-point sources of pollution?
Anything that is not discharged from a pipe. (Stormwater runoff, agricultural drainage, faulty sewage systems)
175
Why is NPS pollution difficult to address?
It is not attributable to a small amount of polluters, and associated with fundamental changes in the landscape like urbanization and agricultural development.
176
What is an ecoregion?
An environmental area characterized by specific land uses, soil types, surface form, and potential natural vegetation.
177
What is the EPA?
The enviornmental protection agency.
178
Why do the glaciated mountain lakes of Minnesota have less phosphorous and chlorophyll than the corn belt lakes?
Fertilizer runoff from the farms.
179
What do ecoregions hope to clarify?
Patterns in ecosystems and the goals and methods used to protect lakes.
180
Why is the water clearer in oligotrophic lakes?
Because the concentrations of algae are far lower.
181
Why does the oxygen in the hypolimnion of an oligotrophic lake never fully deplete?
There isn't a huge amount of organic matter that goes to the bottom.
182
What is the study of lakes?
Limnology.
183
True or false, lack of oxygen restricts animals from living in the hypolimnion of oligotrophic lakes.
False.
184
What is the most common fish found in the hypolimnion of oligotrophic lakes?
Lake trout.
185
What is the first nutrient that most plants deplete?
Phosphorous.
186
How can a winter kill be a good thing?
Fish that survive have reduced competition, and smaller fish die off which means more zooplankton to eat the algae.
187
How are they attempting to reduce algae populations in some lakes?
They are removing the planktivores (small fish that eat plankton) so that they can eat the algae.
188
What is Eurasian watermilfoil?
An invasive macrophyte.
189
How many states has Eurasian watermilfoil invaded?
45.
190
What are some problems Eurasian watermilfoil causes?
It interferes with recreational water activities, crowds out native plants, decreases diversity, depresses real-estate values, decreases levels of dissolved oxygen, creates a better breeding ground for mosquitoes, and reduces the number of fish/invertebrates.
191
What is the best way to avoid spreading Eurasian watermilfoil?
Makes sure you remove all plants from beneath your boat.
192
Why is Eurasian watermilfoil so dominant over other native plants and so intrusive to water activities?
It forms thick mats of vegetation and floats on or just below the surface.
193
What is the riparian zone?
The area surrounding the lake.
194
How come some researchers believe the increasing populations of Canada geese is harming lakes?
The large amount of goose droppings is over-fertilizing the soil and providing too many nutrients in lakes, possibly resulting in algal blooms.
195
Why are Canada geese exploding in populations?
Our urban development around bodies of water is creating ideal goose habitat, short grass parks near bodies of water.
196
What is the Migratory Bird Treaty Act of 1918?
It states that you cannot trap or kill any migratory birds without special permits.
197
True or false, manure can cause algal blooms and extremely high decreases in water quality.
True.
198
What disease can agricultural runoff pollution cause?
Cryptosporidium.
199
Why do invasive species often thrive so much?
They outcompete natives by reproducing faster, getting food and habitat more efficiently, or have no natural predators.
200
What event caused the spread of more invasive species?
The establishment of international trade.
201
What are the big three invasive plants in lake ecosystems?
Eurasian watermilfoil, purple loosestrife, and curly-leaf pondweed.
202
What are the most common ways invasive species reach a lake?
Boaters carrying invasive plants on propellers, people releasing pets, or people failing to keep aquatic gardens under control.
203
True or false, most point source pollution occurs in lakes.
False, most of it occurs in rivers or oceans.
204
True or false, everyoe lives in a watershed.
True.
205
What are some sources of NPS?
Roads, parking lots, fields, lawns and golf courses, and faulty septic systems.
206
What are some of the most common pollutants in lakes?
Pollutants can be sediment, fertilizer, pesticides, pet wastes, heavy metals and petroleum products.
207
What has made everyone's house a lakeshore property?
The storm sewer system.
208
How can people help to stop pollution in lakes?
Sweep up fertilizer rather than washing it away, do not apply fertilizer to frozen ground, do not waste water, use lawn clippings as fertilizer, leave vegetation along the shoreline, remove pet waste from your lawn, and dispose of chemicals properly.
209
True or false, reducing vegetation decreases erosion.
False.
210
Why is erosion a problem?
It can damage structures and increase the speed of harmful runoff.
211
How does pet waste harm lakes?
It introduces harmful microorganisms and excessive nutrients.
212
How do road salts harm lakes?
They change water chemistry and kill fish.
213
What do pollutants interfere with (in regards to organisms) in a lake ecosystem?
Respiration, photosynthesis, growth, and reproduction.
214
What is a wetland?
A generic term for all the different kinds of wet habitats where the land is wet for some period of time each year but not necessarily permanently wet.
215
Where do wetlands occur?
Many wetlands occur in areas where surface water collects or where underground water discharges to the surface, making the area wet for extended periods of time.
216
How do wetlands maintain and improve the water quality of rivers and lakes?
They intercept runoff and remove or transform pollutants. They also trap sediment and nutrients.
217
True or false, wetlands have no economical benefit.
False. they can save communities millions that would otherwise be spent on water treatment plants.
218
How much of the nitrogen and phosphorous is captured when water runs through wetlands?
Phosphorous: 45%
Nitrogen: 90%
219
How do wetlands decrease the demand for oxygen in lakes?
They trap a lot of the decaying organic matter, removing the need for oxygen to do the decomposition in the lake.
220
How do wetlands remove bacteria from wastewater?
The wetlands trap the protozoans and bacteria and they soon die from exposure to sunlight, the low pH of wetlands, or from toxins excreted by wetland plants.
221
What are two harmful natural events that wetlands help to prevent?
Flooding and erosion.
222
What percentage of threatened species from the U.S. use wetlands at some point in their life?
55%
223
What percentage of the U.S. is wetlands?
3.5%
224
True or false, as wetland area goes down, bird populations go down.
True. Many species of birds nest or feed in wetlands.
225
What are the three categories of aquatic plants?
Emergent, floating leaf, and open-water submergent.
226
The role of aquatic plants in a lake is similar to the role of what in a forest?
Trees.
227
What do macrophytes do in a lake ecosystem?
Provide structure and food, stabilize the lake bed, minimize erosion, and absorb nutrients that would otherwise be used by algae.
228
Why do smaller fish need plants?
To hide from predators.
