w8 Salt Individuals to Ecosystems

Question 1

salinity

Answer 1

refers to the total [ ] of dissolved inorganic ions in water or soil

Question 2

is salinity a major factor limiting the distribution of biota? what are aquatic biota grouped according to?

Answer 2

yes; Aquatic biota are grouped according to their salinity preferences; i.e. freshwater fauna, brackish-water fauna, and marine fauna

Question 3

how is salinity measured?

Answer 3

conductivity is routinely used to measure salinity

Question 4

what is conductivity + explain the pattern in relation to a graph

Answer 4

• conductivity is a measure of water’s capability to pass electrical flow
• conductivity increases with the [ ] of ions in the water which these conductive ions come from dissolved salts

note: water itself doesn’t get charged but can conduct more electricity

Question 5

when conductivity is used to measure salinity, the relationship depends on the ___ and ___

Answer 5

the relationship depends on the type of salt and temperature

Question 6

salts come from 2 sources; primary salinization is ___ and secondary salinization is ___

Answer 6

• primary salinization is NATURAL sources (eg. harvesting salt)
• secondary salinization is ANTHROPOGENIC sources (eg. road salt)

Question 7

what are the 3 types of primary salinization?

Answer 7

1. weathering
2. sea spray
3. evaporation of seawater

Question 8

primary salinization: weathering

Answer 8

Weathering is the decomposition of soils and their minerals and rocks through direct contact with the earth’s atmosphere. During the process of mineral weathering, salts [Na+ (Sodium), Ca2+ (Calcium), Mg2+ (Magnesium), K+ (Potassium), Cl-(Chloride), SO42- (Sulfate), CO2-3 (Carbonate), and HCO3 (Bicarbonate)] are gradually released and made soluble.

salts in the soil becomes available through weathering; through biotic processes (eg. plant root is good at pulling up good cations usually from rocks)

Question 9

primary salinization: sea spray

Answer 9

Sea Spray is seawater (35000 mg/L salts) in the form of mist and spray that makes its way into the terrestrial environment. This process is only important in coastal areas, where its influence on local salinity may be substantial

wave action and wind spread the salt into the shore through sea spray; edge of ocean where different species have to be adapted to high salt levels; this isn’t a source of salinization further away from the sea

Question 10

primary salinization: evaporation of seawater

Answer 10

Evaporation of seawater, as there are small amounts of salts dissolved in rainwater as a consequence of evaporation of seawater. This third source can be a significant source of salt in the terrestrial landscapes distant from the sea.

clouds moves around and dump that water in land. this is though a source of salinization further away from the sea.

Question 11

what are the 3 types of secondary salinization?

Answer 11

1. irrigation, even in freshwater
2. mining activity
3. salts as de-icing agents

Question 12

secondary salinization (anthropogenic sources): irrigation, even in freshwater

Answer 12

there is up to 500 mg/L dissolved salts. If freshwater is applied over time while irrigating crops, salt will concentrate. This is because water is uptaken more readily than salts by plants, and water also evaporates more readily. Further, plants absorb only a fraction of the
irrigation water, which may in turn cause the groundwater table to rise, bringing salty water to the surface

Question 13

secondary salinization (anthropogenic sources): what are the 2 mining activities + explain each

Answer 13

1. potash
   - a potassium-rich salt (K based salts) formed from evaporated sea beds millions of years ago
   - “potash” refers to a group of potassium (K) bearing minerals and chemicals
   - Potassium (K) is an essential element for all plant, animal and human life
   - Large quantities are mined/extracted from underground deposits for the manufacture of agricultural fertilizers
   - during the manufacturing process of crude salt (containing potash, NaCl and other salts) huge amounts of solid residues are stockpiled salts which are then dissolved during precipitation events and may enter the surface waters
2. coal:
   - the exposure of coal seams to weathering and percolation during coal mining provides many opportunities for the leashing of sulphate from coal wastes into surface waters (another type of salt that’s exposed

Question 14

secondary salinization (anthropogenic sources): salts as de-icing agents

Answer 14

salts have been used in areas that experience snow and ice since it lower the freezing point of water. as salt (NaCL) melt snow at temperatures below 0 (but generally above -12C).

road de-icing salts have an immense benefit to human safety for those traveling during dangerous winter conditions but are the LEADING CAUSE OF SECONDARY SALINIZATION IN NORTH TEMPERATE REGIONS (where we have freezing)
- road salts reduce accident rates of average 78%-87%

Question 15

explain the general idea of the long-term trends in salinization study and its takeaway

Answer 15

study examining long-term trends in salinization, focusing on chloride concentrations in 371 North American lakes. It finds that these levels are changing a lot, and it’s mainly because of things like roads and buildings near the lakes. Even a small amount of these things (1% increase in impervious land cover) increases the likelihood of long-term salinization (make the lakes saltier). This shows the impacts of anthropogenic activities.
- shows the base line stream moving
- can see us getting accustomed to something
- time allows us to see the change and where the salt started to be applied because taht salt ends up in our water ways and soils

Question 16

how much road salts is being applied in the US and in CAN annually?

Answer 16

roughly
- 24.5 million tonnes (US)
- 7 million tonnes (CAD)

For every person in Canada (38,000,000), we put 406 lbs of salt on the road each year

Question 17

what is the primary source of secondary salinization in north temperate regions? what about other regions?

Answer 17

• road salts runoff from road de-icing and anti-icing agents
• whereas in other regions it may be caused by mining, wastewater effluents, irrigation for agriculture

Question 18

which road salts are used? and what is the order in which each of these salts are most to least used in Canada?

hint: there are a couple but list 3

Answer 18

NaCl (sodium chloride) and MgCl2 (magnesium chloride) and CaCl2 (calcium chloride)

97% of road salt in the form of NaCl > 2.9% in the form of CaCl2 > 0.1% as MgCl2 and KCl

Question 19

which of the 2 road salts, NaCl (sodium chloride) and MgCl2 (magnesium chloride), is the more effective, more expensive deicer, more toxic? what about CaCl2 in comparison to NaCl?

Answer 19

• NaCl (sodium chloride): LEAST expensive deicer, less toxic, not the most effective (effective only up to -9C)
• MgCl2 (magnesium chloride): twice as expensive as NaCl, more toxic to aquatic life, but is also effective at low temps
• At low temperatures, CaCl2 (calcium chloride) is an effective deicer but is more than 5 times as expensive as NaCl

Question 20

why doesn’t NaCL and Cl- ions just go away?

Answer 20

compounds containing chloride (most salts) are highly soluble in water meaning they easily dissociate and tend to remain in their ionic forms (eg. Na+ Cl-) once dissolved in water.

THE CL- ION IS HIGHLY MOBILE AND [ ]s IN WATER ARE GENERALLY NOT AFFECTED BY CHEMICAL REACTIONS (they are taken up by chemical reactions so once in there, it’s hard to get them back out). HENCE CL DOES NOT BIODEGRADE, READILY PRECIPITATE, VOLATILIZE, OR BIOACCUMULATE (doesn’t get wrapped up through biotic interactions inside of different organisms so it tends to go back into the environment)

note: in terms of precipitation, we talked about salt evaporating from sea water and coming in land, it’s true but the amount of water that comes up is low relative to the amount of salt that’s actually in the sea water so we get a small input because in part it doesn’t readily precipitate and volatilize that easily

Question 21

order these contaminated sites (freshwater ecosystems) from highest to lowest for both:
- range of road salt contamination (mg Cl-/L)
- range due to natural sources (mg Cl-/L)

+ why?

freshwater ecosystems: river/stream, wetland/pond, lakes

Answer 21

range of road salt contamination (mg Cl-/L)
- wetland/pond > river/stream > lakes

range due to natural sources (mg Cl-/L)
- river/stream > wetland/pond > lakes

discussion: hypothesis why we see high ranges in wetland/ponds relative to river/stream and lakes?
* the movement of the water itself; rivers can flow into lakes then ocean and wetlands can also be part of that flow but the movement is much slower and thereby gets more accumulated into soil
* wetlands are often used as overflow areas and are natural filter

Question 22

why is NaCl AND Cl- harmful to freshwater organisms and what do they do to cope with it and what can it possibly lead to?

Answer 22

freshwater organisms have evolved to regulate their internal salt [ ]s in response to the osmotic challenges posed by their aquatic environment. so body fluids of freshwater organisms are hyper-osmotic (they have higher salt [ ]s in their bodies than in the external water).

these salts are necessary for cellular process, but osmotic pressure is such that electrolytes (including Cl-) want to ‘escape’ and water wants to enter. ORGANISMS USE ENERGY TO MAINTAIN appropriate ION levels IN THEIR BODY AND KEEP WATER OUT to prevent excessive water influx.

However, if salinity levels outside the organism rise beyond a certain threshold (higher than inside)
–> option a: organisms must cope with additional internal salinity, or spend additional energy to expel ions and keep water – this may affect growth and reproduction
–> option b: if salt [ ]s become sufficiently high, it disrupts these osmoregulatory mechanisms interfering with cellular process possibly causing death.

Question 23

what was the study done in Alberta with benthic invertebrate main focus? how was the experiment conducted and what was the result of it? What does the NPP graph in this experiment represents and what was the results it showed?

Answer 23

what was the study done in Alberta with benthic invertebrate main focus?

1. looking at salts [ ] and looking at benthic invertebrates in stream to see how their oxygen changed due to salt stress. to observe that salt stress leads to a metabolic collapse.

how was the experiment conducted and what was the result of it?

1. benthic invertebrates were collected and placed in a respirometer at various (4) salt [ ]s including: low salt, low-medium salt, high-medium salt, high salt
2. response was immediate with increasing O2 consumption up to a critical [ ] followed by low O2 consumption. more in depth:
   - increased metabolic activity leads to higher respiration rates (higher O2 consumption) — b/c to maintain the metabolic activity, it needs more food and oxygen
   - from low salt to high-medium salt we get a higher O2 consumption meaning metabolic rate increases to compensate this additional stress
   - however, in high salt the O2 intake or metabolic rate drops back down
   - this means that by adding stress you need more and more energy to cope to this stress but adding even more stress the body shuts down all together

What does the NPP graph in this experiment represents and what was the results it showed?

• NPP (treatment - control) for same treatments shows a lower peak than O2 demand; S1↑ → S2↑ → S3↓ → S4↓ (into -ve value) dropping lower than what we see un control
• NPP is being one of the basis of the food source for the invertebrates suggesting that with small amount of salts both the primary producers and secondary and tertiary consumers are responding in similar way but then there’s a de-cupeling in the response

Question 24

what is bioassays and why was this method utilized in green frogs (what was it trying to prove us)?

Answer 24

Bioassays are methods that utilize living materials to detect substances and/or determine the potential toxicity of chemicals or contaminated matrices. They are widely used to screen for potential hazardous chemicals in contaminated soils, potable and wastewater, foods, and other materials.

This was seen in green frogs analyzing the relationship between survival of embryos exposed to increasing [ ] of NaCl and road deicing salt of similar Cl- [ ]s.
- bioassays are used to develop dose-response curves to assess the hazard or risk posed by a given contaminant. so from the curve in the graph given, we can determine the LC50 (the [ ] lethal to 50% of the test population within a defined time period)

Question 25

how does IC50 (inhibitory [ ]) defer from LC50? explain how the IC50 of Cl- sublethal effect graph works.

Answer 25

a measure used to determine the potency of a substance measuring the amount of [ ] needed to inhibit/stop a specific biological or biochemical function (eg. growth or reproduction) by 50%

at IC50 the lower [ ] means higher potency (stronger substance), meaning a lower [ ] of the substance is needed to inhibit 50% of the biological or biochemical function = worst
- better to have more [ ] required to affect 50% rather than only a slight [ ] to affect 50%

the y-axis (% inhibition) is the IC50 while x-axis is the [ ]; depending on the targeted inhibition % such as IC25, the point on the curve will be found by identifying the 25% inhibition down to the x-axis [ ] value.

Question 26

topic: the impacts of salt depends on the environment
- causes of environmental variability: hard vs soft water

1. what is hard and soft water?
2. which are common in southern ON and on the Canadian Shield?
3. how does hard water occur?
4. why is __ water common on the Canadian Shield? (4)
5. based on the [ ], which elements classify the hardness of drinking water?

Answer 26

Hard water is water with large amounts/ [ ] of dissolved mineral (specially calcium and magnesium carbonates)
- common in southern Ontario
- occurs when water percolates/filters through porous material in the ground making the water ‘hard’

soft water is water with lower amounts/ [ ] of dissolved minerals (like calcium, magnesium carbonates, bicarbonates, and sulfates)
- common on the Canadian Shield
1. the Shield is primarily composed of granite, which is resistant to weathering and erosion, meaning fewer minerals are leached into the water
2. intense glaciation during the Pleistocene Epoch scraped away much of the overlying rock, further reducing mineral content.
3. The rocky hills and basins filled with lakes or swamps allows for minimal mineral runoff into the water sources
4. the acidic soil there contributes to softening the water, while groundwater sources are naturally filtered

hardness of drinking water can be classified in terms of its calcium carbonate (CaCO3) [ ]
- the more mg/L [ ] the harder the water

Question 27

why is Cl- toxicity lower in hard water considering they have a high [ ] of minerals?

Answer 27

we don’t know.
When we talk about Cl- toxicity being lower in hard water, it means that chloride ions (Cl-) are less harmful in water that contains high levels of minerals, like calcium and magnesium. However, the exact reason for this is not fully understood yet. One idea is that the cells of organisms living in hard water might have stronger barriers, called cell junctions, which selectively block harmful substances from entering. In simpler terms, it’s like having a stronger gate that only allows certain things to pass through. So, organisms in hard water might have adapted to keep chloride ions out of their cells more effectively. If this is true, then organisms accustomed to living in hard water might handle chloride stress better than those from soft water.

Question 28

topic: salt alters the membership and composition of communities

species richness, community, and diversity

Answer 28

species richness is the abundance of species in a community

community is an interacting group of various species in a common location

diversity is the number of species that are in a community (how diverse of different species in a region is it?)

Question 29

responses to Cl- are different among related species and how Cl- affect community composition. explain the case study with daphnia and the cladoceran community in the Muskoka area in relation to this matter.

Answer 29

• case study: two lakes where one has not been heavily salinized and the other has, the Daphnia PARTHENOGENETIC CYCLE and the COMPOSITION of the Cladoceran COMMUNITY in the Muskoka area
• Daphnia species (including D. catawba, D. mendotae, D. minnehaha, D. pulicaria, and D. pulex) exhibit varying responses to Cl- levels, which influence community composition.
• In the lake with minimal salinization, Daphnia undergo parthenogenetic reproduction, contributing to stable population dynamics.
• However, in salinized lakes, stressors like climate or increased Cl- [ ]s can trigger the production of resting eggs, altering the life cycle dynamics.
• These resting eggs serve as a reservoir, allowing Daphnia populations to persist or re-emerge after local extinctions, contributing to the resilience of the Cladoceran community.

mortality species can vary where one is higher than other species within a community in response to a stress like Cl- (can go back to how species have different tolerance level thereby a variation in Cl- response across species)

Question 30

1. what is the long-term community response to Cl- in the case study of the Cladoceran community with daphnia species?
   - hint: compare the 2 lakes - the one with and without Cl- exposure
2. the two graphs representing the 2 different lakes is graphed as an ordination plot in PCA. what exactly is an ordination plot in PCA? what does the graph represent considering the PCA scores to be in the y-axis? and what does it say based on this study case?
3. conclusion of all this

Answer 30

in a lake with no Cl- exposure, the Cladoceran community is similar over time.

In a lake with Cl- exposure since in 1950, the Cladoceran community has changed over time with a drastic decrease trend changing the community composition a lot more than the lake with no exposure.

2. An ordination plot, plots the objects (sites) in the reduced dimensional space. That is, it displays the objects in one, two or three dimensions so that the major patterns amongst objects can be visualized.
   - “dimensions” refer to the # of variables eg. if your dataset has 5 measurements (such as height, weight, age, etc.), it has 5 dimensions.

• PCA scores in the Y-axis it means the community composition has changed and the larger the difference b/t those the larger the change of community composition; doesn’t tell us which community is doing better or worse, just that it has changed

3. as we change the environment through salinization we expect larger shift in community salinization
   - variation in Cl- tolerance is pervasive even just within the zooplankton (in pic0
   - as such, we expect Cl- effects on communities to be the norm rather than the exception

Question 31

trophic cascade

Answer 31

powerful indirect interactions that can control entire ecosystems. occur when predators limit the density and/or behavior of their prey and thereby enhance survival of the next lower trophic level.

an ecological phenomenon that can be triggered by the addition or removal of (top) predators, and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling.

with the removal of one of the two predators causes a larger shift in community composition

Question 32

topic: impacts of salt ‘scale up’ to change entire ecosystems

populations to ecosystems: within an ecosystem with zooplankton and phytoplankton species, what is the response to the addition of NaCl?
hint: y-axis is the total abundance of zooplankton/phytoplankton. x-axis is the NaCl levels

1. compare both results if plotted in a graph
2. compare the 2 trends within the zooplankton graph (zooplankton: day 9 and day 22)
3. relate the resulting comparison plotted graph to trophic cascade

Answer 32

zooplankton abundance decrease with the addition of NaCl. Phytoplankton abundance increase with the addition of NaCl.

zooplankton:
- at low [NaCl] day 9 abundance is greater than day 22 abundance meaning that there’s a weak affect at day 9 and a stronger affect at day 22 with the same [ ] level resulting in a much greater decrease in the abundance with day 22
- at high [NaCl] (780), both trends result in almost identical abundance value which that [ ] has an immediate affect at those abundances

phytoplankton:
- with phytoplankton abundance through time we see the affect of trophic cascade that’s driven by the NaCl [ ]
- the phytoplankton prefers high salt environment isn’t exactly a sure reason; we see an indirect affect of salt on phytoplankton and the indirect affect is through the herbivore zooplankton

trophic cascade graph comparison:
- zooplanktons are primary consumers that eat algae and phytoplanktons which are primary producers.
- Cl- suppresses grazers and causes algae to flourish, potentially leading to algal blooms and other phenomena in certain ponds which they tend to cause problems for other reasons like eutrophication and might arise in part due to toxicity of salt to the grazer of the phytoplankton
- due to the decrease in zooplankton abundance cause of the toxicity results of the NaCl addition, phytoplankton aren’t being consumed as much creating an indirect positive affect due to high salinization

Question 33

what is the chemical consequence for ecosystem in terms of thermal stratification density when salt is added? (remember stratifications changes seasonally due to the temperature altering its density)

hint: chemocline layer is created below the hypolimnion layer throughout the process

Answer 33

(reminder: higher density = cooler temperature = less layer mixing)

so large inputs of Cl- ions to lakes can interfere with normal seasonal mixing of lake waters, causing a chemical form of stratification. as chloride accumulates in the deepest part of the lake (hypolimnion), hypolimnion (lowest layer) becomes denser than normal resisting to mixing. higher salt [ ] leads to higher water density which can create a chemocline layer (high density zone where there isn’t mixing at all) below the hypolimnion layer.

Question 34

is there life below the chemocline layer and what type of layer is that?

Answer 34

below that chemocline life itself drops off all together, no photosynthesis due to the condition of water.

SO: Low levels of dissolved oxygen in the monoliminion can stress or kill aquatic life, giving rise to a “dead zone” within the lake

Question 35

in thermal stratification along with the addition of chloride, what is:
- turnover vs overturn
- meromictic lakes vs monomictic
- monimolimnion
- mixolimnion
- chemocline
- hypolimnion

Answer 35

Turnover refers to layers mixing where thermal stratification is broken down by seasonal temperature changes, and the lake begins to uniform temperature/density, while overturn describes the process where the surface layer sinks and the bottom layer rises, leading to a homogenization of the water column

A lake may become monomictic, mixing layers once instead of twice, or meromictic, having no mixing.
- meromictic lakes: can usually be divided into three sections or layers: top layer (mixolimnion) -> middle layer (chemocline) -> bottom layer (monimolimnion)

mixolimnion: top layer which behaves like a holomictic lake (undergoing a complete circulation that extends to the deepest parts during overturn)

chemocline: middle layer with high density zone where there isn’t mixing at all

monimolimnion is the bottom portion where the water circulate minimally and are generally hypoxic and saltier than the rest of the lake.

hypolimnion: lowest layer in the deepest part of the lake. salty hypolimnion can be resistant to mixing.