Fresh Water, Oceans and Coasts Flashcards
1
Q
How much of the Earth’s water is ocean water/saltwater?
A
97.5%
2
Q
How much of the Earth’s water is fresh water?
A
2.5%
3
Q
What defines fresh water?
A
mostly pure with few dissolved salts; largely in glaciers, ice caps and underground aquifers
4
Q
How much fresh water is actually easily available for use?
A
1 part in 10,000
5
Q
Percentage of fresh water that is surface water
A
1%
6
Q
Percentage of fresh water locked up in ice caps and glaciers
A
79%
7
Q
Percentage of fresh water as groundwater
A
20%
8
Q
Percentage of surface water as lakes
A
52%
9
Q
Percentage of surface water as soil moisture
A
38%
10
Q
Percentage of surface water as atmospheric vapor
A
8%
11
Q
Percentage of surface water as water in organisms
A
1%
12
Q
Percentage of surface water as rivers
A
1%
13
Q
Water cycle
A
the natural processes that recycle water through interconnected aquatic systems that exchange or involve water itself + pollutants, sediments, organisms and dissolved substances
14
Q
How can the water cycle be affected by humans?
A
through the use of dams/levees, by withdrawing water for use and by introducing pollutants
15
Q
Groundwater
A
water found beneath the Earth’s surface in pores in soil and rock; flows slowly from high to low pressure; may be underground for thousands of years; held in aquifers
16
Q
Aquifer
A
porous rock, sand or gravel formation underground that holds water; has two distinct layers separated by a water table
17
Q
Zone of aeration
A
the upper zone of an aquifer where the pore spaces are partly filled with water
18
Q
Zone of saturation
A
the lower zone of an aquifer where the pore spaces are completely filled with water
19
Q
Recharge zone
A
an area where water infiltrates the Earth’s surface and enters an aquifer (that process = infiltration)
20
Q
Confined aquifer (AKA artesian aquifer)
A
trapped between layers of less permeable substrate (often clay), meaning water is under higher pressure; taps into confined aquifers
21
Q
Unconfined aquifer
A
has no upper layer confining its water
22
Q
Ways that groundwater can rise to the surface
A
wells, springs, wetlands
23
Q
Well
A
a human-made method of retrieving groundwater; pulls water out of pore spaces in rock and soil beneath the water table
24
Q
Runoff
A
water from rain, springs or melted snow/ice that runs over the Earth’s surface; downhill converges at the lowest spot to form streams, creeks and brooks that can merge into rivers that lead to a lake or the ocean
25
Tributary
a small river that flows into a larger one
26
Watershed/drainage basin
the area of land that is drained by a river system; allows a river's water to be traced back to where it fell as precipitation
27
River system
includes a river and its tributaries
28
Length of time for rivers to shape landscapes
thousands to millions of years (through erosion and deposition; can shift position)
29
Floodplain
the areas near a river's course that are subject to periodic flooding; very fertile due to the deposition of silt/eroded soil (for agriculture and riparian/riverside ecosystems)
30
What major factor influences the shape of a river's course?
flooding - scours new channels, so if dams/levees are constructed meandering decreases dramatically
31
Inland seas
very large lakes
32
Zones of lakes and ponds (+ standing water in general)
littoral, benthic, limnetic, profundal
33
Littoral zone
a shallow, nutrient-rich zone nearest to the edges of a water body where aquatic plants can grow and invertebrates that other animals can eat are abundant
34
Benthic zone
the zone of a water body running from the shore to the deepest point that is rich in nutrients and low in oxygen; contains many invertebrates that eat detritus or each other
35
Limnetic zone
the open, shallow part of a water body that is far from the shore but still penetrated by sunlight; photosynthesis supports phytoplankton (algae, protists, cyanobacteria) that support zooplankton (both eaten by other organisms)
36
Profundal zone
the deepest part of a water body that is also far from the shore; lower in dissolved oxygen and lacks photosynthetic life
37
How can streams and runoff alter lakes and ponds?
can add sediment and nutrients
38
Oligotrophic
refers to a water body that is low in nutrients and high in oxygen; considered to have good water quality but to lack biological productivity
39
Eutrophic
refers to a water body that is high in nutrients and low in oxygen; considered to have poor water quality but to have abundant biological productivity
40
Aquatic succession/eutrophication
the natural process by which a water body transitions from oligotrophic to eutrophic; may also be induced or accelerated by humans (from nutrient pollution)
41
Wetland
a system where the soil is saturated with water; features shallow standing water and ample vegetation; rich and productive; includes freshwater marshes, swamps, bogs and vernal pools
42
Freshwater marsh
tends to have plentiful vegetation like cattails and bulrushes growing above (and thanks to) shallow water
43
Swamp
vegetation and shallow water within a forest
44
Bog
a pond covered with thick mats of vegetation; can represent a stage in aquatic succession
45
Vernal pool
a seasonal wetland that forms in the early spring from rain and snowmelt but dries up as temperatures increase
46
Benefits of wetlands
serve as valuable habitat, slow runoff, reduce flooding, recharge aquifers, filter pollutants
47
What actions can damage or destroy wetlands?
draining and filling them for agricultural purposes, withdrawing water, diverting water, channelizing rivers and building dams
48
Proportion of wetlands in the U.S. and Canada lost
> 50% (since European colonization)
49
Inland seas, not the oceans, receive the greatest input of water, sediment, organisms and pollutants.
false
50
Proportion of Earth's surface that the oceans take up
71%
51
Contents of the ocean
96.5% water, rest = ions from salts (final destination for runoff with salt)
52
Ocean salinity
33,000 - 37,000 ppm
53
Fresh water salinity
< 500 ppm
54
What makes the ocean's temperature decrease with depth?
amount of sunlight that can penetrate decreases with depth
55
Currents (horizontal)
vast riverlike flows of water in the upper 400 m of ocean water that move horizontally over great distances; long-lasting, predictable, interact with the climate, used for navigation; driven by the density of seawater, heating/cooling, wind and the Coriolis effect; increase with cooler or saltier water
56
Vertical currents
generated by surface winds and heating; involve upwelling and downwelling
57
Upwelling
the rise of deep, cold, dense water to the surface of the ocean; increases primary productivity since deeper water is richer in nutrients, which means fishing is more successful
58
Downwelling
the sinking of warm, oxygen-rich surface water to the bottom of the ocean; provides an influx of oxygen to organisms living there and "buries" carbon dioxide in sediment
59
Bathymetry
the depth of water in the ocean
60
Complexity of the ocean floor (about)
has underwater volcanoes/mountain ranges; underlain by continental sediment; vast areas of flat abyssal plains; seafloor spreading at ridges + crust subduction at trenches; continental shelves slope gently until the shelf-slope break (division between the continental shelf and slope)
61
Thermohaline circulation
the global current system wherein warm and low-salt water moves along the ocean's surface while cold and high-salt water moves deep below it; vertical and horizontal water movements affect climate everywhere; warm water eventually evaporates (leaves behind salt) and cools (sinks) but can travel long distances first; hypothesis that interrupting the system causes rapid climate change (ice melt = influx of fresh water = surface water less dense, so downwelling ceases + rapid cooling occurs + areas closer to the poles don't receive warm traveling water)
62
El Niño-Southern Oscillation (ENSO)
a systematic shift in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific; normally winds travel east to west (high to low pressure) along the equator so warm surface water "piles up" in the west (50 cm higher and 8 degrees C warmer in Indonesia vs. South America, higher risk of flooding, upwelling in South America) -- but every 2-8 years the winds weaken and warm water flows backward to South America (due to decreased air pressure in the east and increased in the west)
63
Effects of El Niño
lack of upwelling around South America means a lack of nutrients for surface sea life and fisheries; creates rainstorms/floods where typically dry and drought/fire where typically moist
64
La Niña
a systematic shift where cold ocean water rises and moves west in the equatorial Pacific with strengthened winds; has the opposite climatic effects as El Niño
65
What is the effect of global warming on the ENSO cycle?
increases the frequency and strength (due to warmer air and sea temperatures)
66
Intertidal (littoral) ecosystem
the collection of biotic and abiotic factors located where the ocean meets land between the uppermost part of high tide and the lowest limit of low tide; organisms within are lashed with waves, exposed to air/sun and submerged at different parts of the day
67
Tides
the periodic rising and falling of the ocean's height at a given location caused by the gravitational pull of the Moon and Sun
68
Supratidal/splash zone and subtidal zone
zones beyond the edges of the intertidal zone; former is splashed by waves but not fully submerged, latter is always submerged
69
Tide pools
shallow pools of water created at low tide when seawater is trapped in rocky crevices; serve as shelter for some organisms
70
What makes the intertidal ecosystem so biologically diverse?
temperature, salinity, moisture and other conditions change a lot from the highest to lowest reaches
71
North American Drought Atlas (NADA)
a climate reconstruction for North America based on tree ring samples (since trees grow at different rates depending on climatic conditions); allows a view of climate history as well as climate predictions
72
Palmer Drought Severity Index (PDSI)
a measure of the difference between soil moisture supply (precipitation) and moisture demand (evaporation + root uptake); a negative value represents drought and a positive value represents wet conditions
73
What did studies using the North American Drought Atlas, drought indicators, and greenhouse gas simulations find?
drying soil is currently driven not by less precipitation (natural climate variation) but by increased evaporation pressure, temperature and water uptake (human-caused); predicted unprecedented drought through 2100 (worse than the Medieval megadrought period); doubled chance of decade-long drought and 70% higher chance of multi-decade drought since the 20th century (with little change in a low-emissions scenario); water conservation should continue in dry areas but also take place in wet areas
74
Estuaries
shallow water bodies where rivers flow into the oceans and mix fresh water with salt water; biologically productive; provide habitat and food for shorebirds and shellfish + nurture sea grass beds; experience fluctuations in salinity with daily and season changes in tides/runoff; affected by coastal development, water pollution, habitat alteration and overfishing
75
What proportion of people lives within 160 km of the ocean?
2/3
76
Salt marshes
areas along coasts at temperate latitudes where the tides wash over gently sloping sand/silt; have tidal creeks/channels (where the tides flow in and out), marsh flats (elevated spots where water enters at high tide) and benches (the flat areas between creeks); have high primary productivity, provide habitat for shorebirds + waterfowl + fish + shellfish, filter pollution and stabilize shorelines during storms
77
Mangrove forests
forests of trees at tropical and subtropical latitudes with trees that have unique, salt-tolerant roots (curve upwards to receive more oxygen or downwards to support the tree when water levels are fluctuating); provide habitat for fish + shellfish + crabs + snakes + birds, stabilize shorelines during storms, filter pollutants, capture eroded soil and protect offshore coral reefs; half of all globally have been destroyed by development (often for tourist resorts and shrimp farms)
78
Kelp
large brown algae that grow along temperate coasts from continental shelf floors; can be up to 60 m tall and grow up to 45 cm/day; form "forests" that provide shelter and food for invertebrates/fish and in turn support predators; absorb wave energy and protect shores from erosion; can be consumed by humans and contain compounds that work as thickening agents (in cosmetics, paint, ice cream)
79
Coral reefs
a mass of calcium carbonate at shallow subtropical and tropical latitudes from the shells of corals; may occur as an extension of shoreline, along a barrier island that is parallel to the shore, or as an atoll (a ring around a submerged island); absorb wave energy and provide lots of biodiversity
80
Reef
any underwater outcrop of rock, sand, etc.
81
Coral
tiny marine animals that remain attached to rock or other reefs and capture food with stinging tentacles; mostly colonial so millions may be found in a given reef; shells remain after death so more may grow on top of them
82
Zooxanthellae
an algae that is symbiotic with coral; provides food and gives reefs color while living within coral
83
Human impacts on coral reefs
coral bleaching (when zooxanthellae leave/die and deprive of nutrients) + coral death (also exposes species that hide around them to predators), especially from rising temperatures and pollution; nutrient pollution causes algae to smother; use of cyanide by divers to stun and catch fish causes damage
84
Deep-sea coral does exist within cold water at 200-500 m depths.
true
85
Photic zone
the upper part of a water body with the most primary productivity and diversity due to sunlight exposure (the first 10 m of depth absorb 80% incoming solar energy)
86
Pelagic zone
the part of a water body between the surface and the floor; diversity varies as it tends to concentrate where nutrient upwelling occurs
87
Benthic zone
the very bottom of a water body/the region closest to the floor; not very well-known when it comes to the ocean but organisms must tolerate extreme pressure, no light and no food from autotrophs (feed on detritus and dead organisms from above, act as predators or receive food from mutualistic bacteria)
88
Hydrothermal vents
spots on the seafloor where hot water rises and carries minerals that eventually precipitate to form rock; host to animals that use symbiotic bacteria to get their energy from the chemicals released + survive in very narrow zones between very hot and very cold temperatures
89
Proportion of people on Earth affected by water shortages (due to unsustainable withdrawals)
1/3
90
Examples of manmade waterway engineering
dams, levees, diversion canals
91
Benefits of waterway engineering
helps to satisfy demands for water supplies, transportation and flood control
92
Drawbacks of waterway engineering
altering one part of a waterway can alter many others (60% of the largest 200+ rivers are moderately to strongly affected by it now); can keep sediment trapped in a waterway such that natural floods wash away soil without being offset
93
Factors that influence water access
population, climate, season (ex. monsoons give large % of annual rain in a short time), changing river flow with precipitation, waterway engineering (dams store water from wet months into dry months)
94
How can climate change influence water access?
by altering precipitation patterns, melting glaciers, causing early runoff + more intense droughts and floods
95
Proportion of major rivers with decreased flow between 1948 and 2004
1/3
96
Uses of water
for mining + industrial + manufacturing processes, homes, crops and livestock; globally 70% for agriculture, 20% for industry and 10% for residential/municipal purposes
97
Consumptive use
the removal of water from an aquifer or water body without returning it to its source (ex. irrigation)
98
Nonconsumptive use
the temporary removal or nonremoval of water from its source during use (ex. hydroelectric dams)
99
Why is so much water used for agriculture?
rapid population growth - 70% more is withdrawn for irrigation than 50 years ago and twice as much land is irrigated (+ 15-35% withdrawals unsustainable, worsened when seasonal shortages occur)
100
Case study of the Aral Sea
once the 4th largest lake but lost most of its volume in 45 years due to poor irrigation practices where the USSR flooded dry land for cotton farming using the rivers that supplied it; restoration efforts are being made but 60,000 fishing jobs were lost and little cotton grows there since the soil was waterlogged and salty
101
Amount of groundwater withdrawn per year that exceeds the amount that returns to the ground
160 km^3; easier to deplete since aquifers may recharge slowly
102
Proportion of the population relying on groundwater
1/3 (includes 99% of the rural population)
103
Consequences of mining aquifers
water tables drop --> freshwater wetlands dry up, extraction is more difficult/costly, land above may not be as well supported (sinkholes and pipe ruptures can occur), harder to recharge (soil and rock are compacted with less pore space), saltwater can intrude near coastal areas
104
Largest aquifer
Ogallala (in the Great Plains)
105
Liters of bottled water drunk per year by the average American
136+
106
Costs of bottled water
$160 billion/year worldwide; energy costs 1000-2000x that of tap water mainly due to transportation; 1.5 million tons of plastic bottles/year thrown out and not recycled (at least 3/4 all bottles); no safety/health/taste benefits compared to safe tap water
107
Benefits of living in floodplains
flat land, fertile soil and water access (but come with floods)
108
Flooding
a natural process whereby rain/snowmelt swells a river's volume and causes it to spill over its banks; long-term builds and enriches soil with sediment, short-term damages manmade structures
109
Levee (AKA dike)
a construction on the banks of a river to constrain/prevent floods; may worsen flood events since the accumulation of water means it holds more energy
110
Aqueduct
an artificial river/canal used to divert water from rivers/lakes; largest in China (sends water to the dried up portion of a major river that resulted from climate change and unsustainable withdrawal - believed to not be enough + to have environmental impacts + displace hundreds of thousands)
111
Dam
an obstruction placed in a river/stream to block its flow; creates reservoirs
112
Reservoir
an artificial lake created by a dam that stores water for later use
113
Benefits of dams
prevent floods (especially by storing seasonal surges), provide drinking water if the local watershed is protected, allow irrigation, can be used to generate renewable electricity (and replace other forms of energy), creates recreational opportunities, may make transportation on the water easier
114
Drawbacks of dams
can displace a large number of people, prevent sediment from nourishing floodplains downstream by trapping it, have a small risk of catastrophic failure, alters habitat and ecosystems on both sides of the affected river, takes away from recreation on the river + fisheries (thermal pollution and migration blockage), disrupts natural flooding, can cause erosion at the river mouth as water slows upon entering the reservoir, can trap pollutants and ruin drinking water supplies
115
Largest dam project
Three Gorges Dam in China (Yangtze River)
116
Solutions to water depletion
an increase in supply or a decrease in demand
117
Options for a supply-based approach to water depletion
limited; can increase the number of dams but most suitable locations already have them, can use desalination/desalinization (heat saltwater and condense the vapor to distill it) but costly + needs lots of fossil fuel energy + kills aquatic life + generates salt waste (so mostly occurs in wealthy, oil-rich and water-poor areas)
118
Benefits and drawbacks of a demand-based approach to water depletion
involves conservation and increased efficiency of water use; politically difficult since changes in behavior are necessary; results in better economic returns + less social/ecological damage; effective even with population increases
119
Ways to make irrigation more efficient
not using "flood and furrow" irrigation that encompasses 90% of global irrigation and 60% of which evaporates or sinks below plant roots; no government subsidies for crops with high water needs in arid locations; encouraging low-pressure spray irrigation or drip irrigation (latter = as little as 10% water wasted + use cut in half + higher crop yields + extra income); using biotechnology to produce crops that need less water (with genetic modification and selective breeding)
120
Ways to make households decrease water use
installing low-flow faucets, showerheads, washing machines and toilets; using dishwashers rather than handwashing (if full); harvesting rainwater to decrease hose use; growing native plants adapted to the local climate as opposed to nonnative ones (xeriscaping)
121
Ways to decrease water use in industrial and municipal contexts
choosing processes that use less water (and thereby decrease cost); using treated wastewater; finding and patching pipe leaks; auditing industry
122
Why did fresh water use double from 1960-2000?
population growth, increased irrigation and increased industrial development
123
Regional conflict is expected to increase over time due to water shortages and subsequent shortages of other resources/necessities.
true; the population continues to grow and climate change continues to alter precipitation patterns
124
A large number of major rivers and their watersheds (encompassing almost half of all land) cross national borders.
true; leads to transboundary disagreements + cooperation/co-management
125
Reports by the World Commission on Water and the EPA on rivers
more than half of the most major rivers are seriously depleted and polluted + 55% of U.S. rivers and streams are in poor condition; groundwater pollution is a "covert crisis"
126
Prevention vs. treatment for water quality/resource issues
prevention is easier and more effective
127
Water pollution
changes in the chemical, physical or biological properties of waters caused by human activities; most are not conspicuous
128
Examples of water properties measured for quality
chemical = pH, plant nutrient concentration and dissolved oxygen; physical = temperature and turbidity (density of suspended particles); biological = harmful microorganisms and species diversity
129
Point source
a source of pollution from a discrete location (e.g., a specific factory, sewer pipe, animal feedlot, sewage treatment plant, disposal site, abandoned mine or oil tanker); easier to determine and address
130
Non-point source
a source of pollution that, together with many other inputs over large areas, results in a cumulative issue (e.g., farms, city streets, golf courses, construction sites, animal feedlots or residential neighborhoods in general); harder to determine and address
131
U.S. Clean Water Act
addressed point-source pollution by targeting industry
132
Prevention of drinking water pollution
mainly done by limiting development on watershed land near reservoirs
133
Types of water pollution
toxic manmade substances, pathogens and waterborne diseases, excessive nutrients, biodegradable wastes, sediments, oil, nets and plastic debris, thermal pollution
134
About toxic manmade substances as a form of water pollution
includes pesticides, petroleum products, toxic metals, acids from mining sites or precipitation, etc.; poisons or affects the health of animals and plants (including humans) and alters ecosystems; industry regulation and modifying processes/purchases to reduce use can help
135
About pathogens as a form of water pollution
enter the water through inadequate sewage treatment or animal waste from feedlots and farms; cause more health problems than any other kind of water pollution (20 million in U.S. alone per year get sick from it); prevented by properly disinfecting drinking water and treating wastewater, increased public education and increased regulations for food processing + production + distribution
136
About excessive nutrients as a form of water pollution
results in dead zones from an increase in the rate of natural eutrophication or hypoxia (low-oxygen conditions, defined as < 2 mg/L) as excess nitrogen or phosphorus can fertilize algae and aquatic plants and cause them to grow rapidly, but thriving life means more frequent death and bacteria use oxygen to decompose them; may also cause algae that produce toxins to thrive which harms other organisms and decreases fishing and tourism (especially important for communities that rely on them); mainly comes from wastewater and farms; prevented by treating wastewater to remove nutrients, decreasing fertilizer use, using phosphate-free detergents, and planting vegetation or protecting areas around streams and rivers to lower input
137
About biodegradable wastes as a form of water pollution
large amounts cause low oxygen levels; can include human/animal waste, paper pulp from mills, and yard waste, all of which provide organic material for bacteria to decompose (which requires oxygen); has been helped by wastewater treatment in developed nations (less common in developing ones)
138
Harmful algal blooms
exploding populations of marine algae that produce toxins; observed as "red tides" when the algae produce a red pigment
139
Wastewater
all water affected by human activity, including water from toilets, sinks, showers, dishwashers and washing machines + water used in industrial cleaning, water used in manufacturing, and stormwater runoff
140
About sediments as a form of water pollution
travel long distances and are carried by runoff to rivers; worsened issue when clear-cutting, mining, and field cultivation increase erosion; worse effects for rivers that are naturally clearer and less sediment-rich as species are adapted to those conditions; improved with better management of farms/forests and avoiding large-scale disturbances of vegetation
141
Sediment
eroded rock/soil
142
About oil as a form of water pollution
large spills are infrequent but have major impacts on fisheries, economies and ecosystems; currents can spread it widely and cause it to affect large areas of water, sediment and shoreline; can keep populations low and cause beaching of marine mammals for years after the fact; also has many widespread and small nonpoint sources (e.g., leaking from shipping vessels/recreational boats and vehicle motor oil in runoff); spills from tankers cause 12% of such pollution per year and 3% comes from leakage during extraction on offshore rigs; lessened with increased prevention and response efforts + regulations on shipping
143
Examples of major oil spills
1989 Exxon Valdez (Alaskan coast), 2010 Deepwater Horizon (Gulf of Mexico)
144
About nets and plastic debris as a form of water pollution
aquatic animals can mistake it for food or get caught in it, leading to death; the chemicals within it can be toxic and it cannot be digested; can serve as rafts on which invasive species can travel; takes 500-1000 years to degrade at sea and no viable way exists to collect the tiniest particles (so improved by prevention and regulation, e.g., 2006 U.S. Marine Debris Research, Prevention and Reduction Act + 2015 ban on the sale of products containing plastic microbeads)
145
Gyre
a region where currents converge; plastic trash easily accumulates there (e.g., the Great Pacific Garbage Patch where plastic-to-organism ratio is 6:1)
146
About thermal water pollution
oxygen-holding capability of water decreases as temperature increases so aquatic life suffers; can also favor invasive species that prefer different temperatures than native ones; may result from withdrawing water, using it to cool a facility and transferring that heat back into a river OR removing vegetation that shades water OR releasing deeper and colder water from a dam's reservoir
147
What makes pollution in groundwater trickier to manage?
harder to detect and often lasts longer (slower decomposition without sunlight and with fewer microbes, fewer minerals, less oxygen and less organic matter); can easily occur as surface pollutants leach in; some chemicals that are toxic at high concentrations (e.g., aluminum, fluorine, nitrates, sulfates) occur naturally in aquifers but pollution can raise their concentrations to dangerous levels
148
Underground hazardous leaks
include carcinogenic (chlorinated solvents, gasoline, industrial chemicals) and radioactive pollution from tanks; national cleanup program by the EPA has unearthed and repaired many but plenty remain; Hanford Nuclear Reservation is the most radioactively contaminated area in the U.S. and is not to be completely cleaned until 2047
149
Federal Water Pollution Control Act of 1972 (AKA Clean Water Act)
resulted from citizen activism in the 60s and 70s; made it illegal to discharge pollution from a point source without a permit, created standards for contaminant levels + wastewater and funded the construction of sewage treatment plants
150
Efficacy of environmental laws in recent decades
enforcement has grown weaker especially with underfunded and understaffed state/federal regulatory agencies; more than 100,000 violations of the Clean Water Act may occur in a year and the EPA/states act on few of them + 1/10 Americans are exposed to unsafe drinking water (and are often unaware as the hazard isn't apparent)
151
Case study of the 1970s Great Lakes pollution issue
constitute 18% of the world's fresh water; algal blooms occurred on beaches and Lake Erie was considered "dead" thanks to wastewater, fertilizer and chemicals entering the water; decreased pollution and lowered levels of the most major pollutants substantially so recovery was possible but some issues persist (high sediment pollution, algal blooms in Erie + the fish within aren't always safe to consume)
152
Water treatment regulation and process
most successful in developed nations; treat with chemicals to remove particulate matter, pass through sand/gravel/charcoal filters and use small amounts of chlorine (or other chemicals) to disinfect it; local governments and water suppliers must meet EPA standards for a range of contaminants
153
Natural processes can process moderate amounts of wastewater, but the large and concentrated amounts generated by densely populated areas can harm the ecosystem and the health of humans without treatment.
true
154
Septic systems
the most common disposal method for wastewater in rural areas; runs from a house to an underground tank where solids and oils are separated from water; water then runs downhill to a drain field of perforated pipes placed horizontally in gravel-filled trenches below ground where microbes can decompose any pollution; waste is periodically pumped from the septic tank to a landfill
155
Use of natural wetlands in water treatment
can filter and purify water, so have been restored, manipulated and constructed for this purpose; water transferred there after primary/secondary treatment at a facility so microbes can decompose the rest of the pollutants; then passed into waterways or runs underground; simultaneously serves as a spot for wildlife and recreation
156
Sewer systems
used in more densely populated areas; carry water from houses and businesses to a centralized treatment location where pollution is removed by physical, chemical and biological means
157
Sewer water treatment process
includes primary treatment, a physical removal of suspended solids (60%) in settling tanks or clarifiers, and secondary treatment, where water is stirred and aerated (oxygenated) so aerobic bacteria can degrade organic pollution (90% suspended solids removed); then use chlorine and sometimes UV light to kill bacteria
158
Effluent
treated water; often piped to rivers/oceans but also to wetlands and aquifers or recycled immediately for lawns, golf courses, irrigation and industry
159
Byproducts of wastewater treatment
digesters/digesting vats contain anaerobic microorganisms that decompose solids (sludge) removed from water and leave behind a wet solution of biosolids (then dried and sent to a landfill, incinerated, or used on farms as fertilizer); digestion process generates methane-rich gas that can be burned for electricity which offsets the treatment cost
160
Overexploitation of marine fish populations
affects how ecosystems function and has caused 28% of all marine populations to be heading towards extinction + more than 50% of all populations are fully exploited (so more cannot be harvested without depletion), leaving only 1/5 able to yield more fish without declining; current trends project that all populations will collapse by 2048; results in a loss of ecosystem services, lowered biological productivity, more sensitive ecosystems, and a decrease in water filtration by vegetation and organisms like oysters (--> algal blooms, dead zones, losses of fish and beach closures)
161
Aquaculture vs. wild-caught
booming in comparison so less pressure is placed on wild populations, but it has its own environmental impacts; rivals traditional fishing in total seafood production (global catch leveled off after the late 1980s despite population growth and more fishing effort); conceals the ongoing issue of population decline as more remote areas, smaller fish and once less-desirable fish are now targeted + with greater intensity
162
Purse seining
commercial fishing method where large nets are used at the surface to capture schools of fish and then pulled shut with a purse line (like a drawstring)
163
Long driftnets
nets used in commercial fishing that span a lot of water and are composed of chains of transparent nylon mesh arrayed to drift with the current and catch passing fish; have weights and floats to stay vertical
164
Longline fishing
commercial fishing method using very long fishing lines with up to thousands of baited hooks
165
Trawling
commercial fishing method where large cone-shaped nets are dragged through open water with floats and weights attached
166
Bottom-trawling
commercial fishing method where weighted nets are dragged on the continental shelf floor to catch benthic organisms
167
Bycatch
a term for the animals at sea that are caught in excess or unintentionally; accounts for millions of deaths of organisms per year, including by drowning/suffocation of those nontarget organisms during the process; led to a ban on driftnetting in international waters (tends to cause a lot of bycatch), + bottom-trawling is akin to clear-cutting especially on complex structures such as reefs; 17% of commercial catches are unintentional (NOAA)
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Examples of some of the marine populations most affected by industry fishing
large-bodied fish and sharks (now only 1/10 as many as before), groundfish/benthic fish (slow recovery with fishing bans in certain areas but decline with fishery collapse)
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Percentage of U.S.-sold seafood that is imported
80%
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Responsible purchase of seafood
hard to know the source of fish when much is imported but guides and apps exist to help identify those that are overfished or that are ecologically harmful to harvest
171
"Fishing down the food chain"
refers to catching the smaller fish consumed by fish that have historically been more commercially available (i.e., lower trophic levels); keeps fishery catches high
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Fisheries manager
conducts surveys, studies population biology and monitors catches in order to find the numbers of different species that can be caught without reducing future catches and maximize sustainable yield (although declines still clearly exist)
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Marine protected areas (MPAs)
areas of the ocean with internationally secured restrictions on fishing and human interference, created from an ecosystem-based resource management perspective (which recognizes that all marine resources are part of a larger system that needs protection); most are located on the coasts of developed countries and unfortunately still often allow fishing or other extractive activities
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Marine reserves
areas of the ocean more completely preserved than MPAs as they do not allow any fishing whatsoever in order to protect ecosystems and restore fisheries; can act as sources for fish in surrounding areas since the fish produced there will disperse out; result in increases in species diversity, population density, total biomass and average organism size; fishers still frequently oppose them
175
Ocean acidification
a form of pollution caused by an increase in carbon dioxide in the atmosphere (especially from fossil fuel use), as the ocean absorbs 1/3 of the excess and slows climate change but has altered chemical properties as a result; surface waters eventually become saturated regardless of the benefits of absorption and more acidic water means that shell-forming organisms lack the carbonate ions necessary to make and keep building their shells (+ coral reefs cannot exist in certain areas and density/diversity decreases)
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Findings on survival of coral reefs against climate change
some are more resilient to temperature and pH changes than others; certain corals may still be able to grow by increasing their feeding rate (if food is abundant)
