Knowt
Note
Studied by 10 peopleNoteStudied by 20 peopleNoteStudied by 24 peopleNoteStudied by 13 peopleNoteStudied by 23 peopleNoteStudied by 3 people
Aquatic ecosystems
Aquatic Ecosystems
Estuaries: the transition zone between rivers (freshwater) and the ocean (salty/marine)
• Often characterized by brackish waters and sheltered habitats like marshes and
mangroves
• The Florida Everglades are the largest mangrove habitat in the world
The Hydrosphere
• One important concept to understand about aquatic ecosystems is that they are all
connected
• Watersheds: a land area that channels all snowmelt and rainfall to a singular point.
• Groundwater connects marine and freshwater systems
Information | |
Light | • Light is needed by photoautotrophs (the most common producer) for the Availability photosynthesis • Phytoplankton are the primary producers of the pelagic zone o Start off most oceanic food webs • Other producers include coral and kelp in shallow waters and emergent plants in wetlands • The productivity of producers is directly correlated with dissolved oxygen concentration |
Salinity | • Salinity is the measure of all the salts dissolved in water. • Rain (freshwater) → river (freshwater) → estuary (brackish) → Ocean (salty) • Salinity increases with depth • Like any other abiotic factor, there is a range of tolerance for all species |
pH | • pH is a measure of acidity • The more H+ ions in a concentration, the more acidic the solution • Rainwater is slightly acidic (6.2), pure water is neutral (7) and seawater is slightly basic (8.6) |
Temperature | • Temperature decreases as you move away from the equator • Temperature decreases as you increase depth • Seasonal turnover: during the fall, the warm surface water of a lake begins to cool, becomes more dense, and sinks. This dense water forces the water at the bottom to rise, "turning over" the layers and recycling nutrients |
Nutrients | • The most productive aquatic ecosystems have two qualities: 1. Exposure to light 2. Supply of nutrients • Nutrients are supplied by sediments being washed into estuaries from the land OR from upwellings of deep sea ocean currents • When phytoplankton have the light and nutrients they need, they reproduce, starting of many aquatic food chains and making marine life possible! |
Human Impact on Aquatic Ecosystems
1. Run-off of Sediments
• Construction, mining, & logging can increase sediment run-off
• Turbidity: a measure of dissolved/suspended solutes
• Happens because roots from vegetation stabilizing soil in place are removed • Light cannot penetrate, decreasing photosynthesis and overall productivity of the aquatic ecosystem
• Sediment can enter fish gills, causing suffocation and death
2. Saltwater Intrusion
• Aquifers are being drained faster than they can be recharged by
natural rain infiltration
o Mostly due to irrigation
• Saltwater Intrusion: the movement of saline water into freshwater
aquifers
• Plants watered with saltwater will die!
• Salt doesn’t evaporate, so it just accumulates on the surface
• Creates positive feedback loop (salt is dehydrating so the farmer pumps even more water)
3. Ocean Acidification
• Diffusion of CO2 into ocean is causing water to acidify
• CO2 reacts with water to produce carbonic acid
• Carbonic acid dissociates to form free hydrogen ions that readily bind carbonate
• Marine life needs carbonate to build shells, so it is “stolen” from them. o Their shells become weaker, leading to stress and more vulnerable
4. Climate Change – Warming of the Ocean
• Also (mostly) due to combustion of fossil fuels
• CO2 is a greenhouse gas, meaning it traps heat in the atmosphere →
climate change
• The ocean has absorbed much of this increased heat
• Coral reefs very sensitive to warmer water → becoming stressed and
causing “bleaching” → Loss of biodiversity
5. Run-off of Fertilizers Causing Eutrophication
• Fertilizer (mostly nitrogen and phosphorous) that we use to help
crops grow can run-off into local waters
• Algae “feeds” on the fertilizer and blooms
• Algae can be so thick, it blocks sunlight
• Algae dies as quickly as it blooms and must be decomposed by
bacteria
• Bacteria sucks up the oxygen for decompositions, leading to death of marine life
6. Dams
• Dams act as a sediment trap, decreasing downstream supply
o Can result in eroding coastlines
o Sediments contain nutrients vital to plankton (the start of most aquatic food chains!)
o Migration/Reproduction of some fish (like salmon) impacted
7. Destruction of Mangroves
• Mangroves are one of the most biodiverse ecosystems, home to many bird and fish populations.
o Fish nurseries: many marine fish lay eggs here so baby
fish can grow up sheltered by the root systems to grow
big before swimming out to sea!
• Mangroves prevent coastal erosion with their enormous root
systems
• Mangroves have thick organic sediment layers that suck up
water like a sponge to reduce flooding
• All of these ecological services disappear when they are
destroyed for urban or agriculture land
8. Overfishing
• Loss of fish stocks caused by new fishing technologies that are too efficient and largely unregulated
• Tragedy of the Commons: no country has an incentive to protect fish stocks or replenish them because they do not belong to one
nation
• Results:
o Decline of a fish population by 90% or more since 1950
o Bycatch: unwanted catch that is often killed (ex. turtles, sharks, dolphins)
9. Loss of Keystone Species
• Species are being lost worldwide at alarming rates due to many things, such as habitat loss or hunting.
• Keystone Species have a disproportionately larger impact on the ecosystem then other species
• Loss of a keystone species will result in a trophic cascade of biodiversity loss • Ex. Otters were hunted in California for their fur, leading to a trophic cascade of the kelp forests
10. Invasive Species
• Non-native species that have been introduced by
HUMANS
• Tend to be generalists that can outcompete native
specialists
• Disrupt food webs and decrease biodiversity
• This will make the ecosystem more vulnerable to further
disturbances
• Ex. The lionfish in the Florida Keys (from the Indo
pacific) have few predators, each many different animals,
and fast reproduction rates
Aquatic ecosystems
Aquatic Ecosystems
Estuaries: the transition zone between rivers (freshwater) and the ocean (salty/marine)
• Often characterized by brackish waters and sheltered habitats like marshes and
mangroves
• The Florida Everglades are the largest mangrove habitat in the world
The Hydrosphere
• One important concept to understand about aquatic ecosystems is that they are all
connected
• Watersheds: a land area that channels all snowmelt and rainfall to a singular point.
• Groundwater connects marine and freshwater systems
Information | |
Light | • Light is needed by photoautotrophs (the most common producer) for the Availability photosynthesis • Phytoplankton are the primary producers of the pelagic zone o Start off most oceanic food webs • Other producers include coral and kelp in shallow waters and emergent plants in wetlands • The productivity of producers is directly correlated with dissolved oxygen concentration |
Salinity | • Salinity is the measure of all the salts dissolved in water. • Rain (freshwater) → river (freshwater) → estuary (brackish) → Ocean (salty) • Salinity increases with depth • Like any other abiotic factor, there is a range of tolerance for all species |
pH | • pH is a measure of acidity • The more H+ ions in a concentration, the more acidic the solution • Rainwater is slightly acidic (6.2), pure water is neutral (7) and seawater is slightly basic (8.6) |
Temperature | • Temperature decreases as you move away from the equator • Temperature decreases as you increase depth • Seasonal turnover: during the fall, the warm surface water of a lake begins to cool, becomes more dense, and sinks. This dense water forces the water at the bottom to rise, "turning over" the layers and recycling nutrients |
Nutrients | • The most productive aquatic ecosystems have two qualities: 1. Exposure to light 2. Supply of nutrients • Nutrients are supplied by sediments being washed into estuaries from the land OR from upwellings of deep sea ocean currents • When phytoplankton have the light and nutrients they need, they reproduce, starting of many aquatic food chains and making marine life possible! |
Human Impact on Aquatic Ecosystems
1. Run-off of Sediments
• Construction, mining, & logging can increase sediment run-off
• Turbidity: a measure of dissolved/suspended solutes
• Happens because roots from vegetation stabilizing soil in place are removed • Light cannot penetrate, decreasing photosynthesis and overall productivity of the aquatic ecosystem
• Sediment can enter fish gills, causing suffocation and death
2. Saltwater Intrusion
• Aquifers are being drained faster than they can be recharged by
natural rain infiltration
o Mostly due to irrigation
• Saltwater Intrusion: the movement of saline water into freshwater
aquifers
• Plants watered with saltwater will die!
• Salt doesn’t evaporate, so it just accumulates on the surface
• Creates positive feedback loop (salt is dehydrating so the farmer pumps even more water)
3. Ocean Acidification
• Diffusion of CO2 into ocean is causing water to acidify
• CO2 reacts with water to produce carbonic acid
• Carbonic acid dissociates to form free hydrogen ions that readily bind carbonate
• Marine life needs carbonate to build shells, so it is “stolen” from them. o Their shells become weaker, leading to stress and more vulnerable
4. Climate Change – Warming of the Ocean
• Also (mostly) due to combustion of fossil fuels
• CO2 is a greenhouse gas, meaning it traps heat in the atmosphere →
climate change
• The ocean has absorbed much of this increased heat
• Coral reefs very sensitive to warmer water → becoming stressed and
causing “bleaching” → Loss of biodiversity
5. Run-off of Fertilizers Causing Eutrophication
• Fertilizer (mostly nitrogen and phosphorous) that we use to help
crops grow can run-off into local waters
• Algae “feeds” on the fertilizer and blooms
• Algae can be so thick, it blocks sunlight
• Algae dies as quickly as it blooms and must be decomposed by
bacteria
• Bacteria sucks up the oxygen for decompositions, leading to death of marine life
6. Dams
• Dams act as a sediment trap, decreasing downstream supply
o Can result in eroding coastlines
o Sediments contain nutrients vital to plankton (the start of most aquatic food chains!)
o Migration/Reproduction of some fish (like salmon) impacted
7. Destruction of Mangroves
• Mangroves are one of the most biodiverse ecosystems, home to many bird and fish populations.
o Fish nurseries: many marine fish lay eggs here so baby
fish can grow up sheltered by the root systems to grow
big before swimming out to sea!
• Mangroves prevent coastal erosion with their enormous root
systems
• Mangroves have thick organic sediment layers that suck up
water like a sponge to reduce flooding
• All of these ecological services disappear when they are
destroyed for urban or agriculture land
8. Overfishing
• Loss of fish stocks caused by new fishing technologies that are too efficient and largely unregulated
• Tragedy of the Commons: no country has an incentive to protect fish stocks or replenish them because they do not belong to one
nation
• Results:
o Decline of a fish population by 90% or more since 1950
o Bycatch: unwanted catch that is often killed (ex. turtles, sharks, dolphins)
9. Loss of Keystone Species
• Species are being lost worldwide at alarming rates due to many things, such as habitat loss or hunting.
• Keystone Species have a disproportionately larger impact on the ecosystem then other species
• Loss of a keystone species will result in a trophic cascade of biodiversity loss • Ex. Otters were hunted in California for their fur, leading to a trophic cascade of the kelp forests
10. Invasive Species
• Non-native species that have been introduced by
HUMANS
• Tend to be generalists that can outcompete native
specialists
• Disrupt food webs and decrease biodiversity
• This will make the ecosystem more vulnerable to further
disturbances
• Ex. The lionfish in the Florida Keys (from the Indo
pacific) have few predators, each many different animals,
and fast reproduction rates
NoteStudied by 10 peopleNoteStudied by 20 peopleNoteStudied by 24 peopleNoteStudied by 13 peopleNoteStudied by 23 peopleNoteStudied by 3 people