Ecology- Ch 2/3 Part 2 LO's

Aquatic ecosystems

Explain how latitudinal variation in temperature drives both major patterns in oceanic currents.

• The equator gets more sunlight, so ocean water is warmer and less dense, staying near the surface.

• This temperature-driven density difference between warm equatorial water and cold polar water helps set up vertical circulation patterns.

• atmospheric cric cells which produce trade winds that push surface waters producing ocean currents)

Explain the importance of vertical circulation in the oceans.

• vertical circulation (including upwelling and downwelling) is important because it redistributes heat. Moves warm surface water to the poles and cold deep water toward the equator. 

• Upwelling brings nutrient rich deep water to the surface

  • provides food for phytoplankton and their consumers→ supports marine food web 

• Downwelling carries O2 rich surface water to deeper layers, this is important for deep-sea organisms that rely on this O2

Describe the processes that cause upwelling and the outcome of these processes. 

• When winds blow parallel to a coastline they push surface water away from the shore

• Also due to earth’s rotation, surface water is moved away from the coast at an angle allowing cold deep water to rise and replace it 

• Outcomes 

  • Brings nutrient rich water to the surface from deep ocean layers

  • Boosts phytoplankton growth 

  • Supports rich marine food webs 

  • helps regulate climate bc cold water at the surface can cool local temps

Define the following and explain how it varies in terrestrial and aquatic environments:

a) Salinity

Salinity

• [ dissolved salts in water] 

• Terrestrial: soils near oceans can have high salinity salt marches and tidal esturaries. Soils in arid regions can become saline bc constantly adding water with dissolved salts, the water evaporates but salt builds up in land. This can make arable land unusable bc too salty for plants. 

• Aquatic: High in oceans ~35 ppt, lower in estuaries, and very low in freshwater (lakes, rivers). varies with rainfall, evaporation, and mixing of freshwater and seawater.

Define the following and explain how it varies in terrestrial and aquatic environments:

b) Acidity

• Ability of a solution to act as an acid (give up H+) 

• Terrestrial: soil pH varies affected by rainfall, pollution (acid rain)

• Aquatic: Oceans slightly basic but ocean acidifcation from Co2 absorption due to increased atmospheric [CO2] is lowering pH. This can harm organisms that make shells because CaCo3 decreases as pH decreases which means they cant build their shells. 

Define the following and explain how it varies in terrestrial and aquatic environments:

c) Oxygen concentration

• pp of dissolved O2 

• Terrestrial: O2 diffuses quickly in the air only changes with altitude. The availibity of atmospheric O2 decreases with elevation above sea level, as the density of air molecules decreases, =21% O2 content at any altitude 

• Aquatic: O2 diffuses slowly in water, and conc varies with temperature (cold water holds more), and depth. In water conc is 1%. 

  • O2 lost by uptake of organisns, warm temp decreases O2 in water 

Explain how variation in the following can impact the distribution and survival of organisms:

a) Salinity

b) Acidity

c) Oxygen concentration

Salinity 

• Only some organisms adapted to live in salty enviornments (mangroves). High/low salinity limits where organisms can survive. 

• Changes in salinity can cause dehydration or water overload in cells stressing and killing organisms not adapted to those changes

Acidity 

• Some plants and animals can only grow in certain pH ranges. Acidic and alkaline envts limit where they can live.

• Too much acidity can cause problems with enzyme function, and harm eggs/larvae in water. 

• ex: ocean acidification caused by CO2 absorption in water decreases the avaiblity of CaCO3, making it harder for marine organisms to build shells 

O2 Conc 

• Organisms that need lots of O2 won’t be found in low O2 areas (high altitudes) 

• Low O2 makes it harder for organisms to breathe, slowing growth, reproduction, or cause death 

• ex: fish die in ponds with little O2 from algae overgrowth

What is ocean acidification? What is causing it and why is it a concern

• It is the decrease in pH of oceans caused by the absorption of CO2 from the atmosphere. 

• Caused by increase in atmospheric [Co2] which is taken in by the ocean, dissolved CO2 +H20→ increases [H+]

• Concern because it is harming coral reefs, and shell building organisms. This is bc as pH dcreases, CaCo3 decreases which makes it harder for shelled organisms to build their shells/skeletons 

Types of freshwater ecosystens. List the major abiotic factors that determine the characteristics of freshwater ecosystems

Rivers(defined by river continuum concept), lakes and still waters (divided into zones by depth), wetlands (still waters with emergent veg, bridge terr and aquatic)

1. temperature 

2. depth

3. Light availibilty (photosynthesis) 

4. O2 conc 

5. pH

6. Nutrient levels

7. Water flow/current 

Describe the river continuum concept. Explain how abiotic conditions change, and how that affects the major consumer groups present.

Concept: biological communites change with stream order and channel size 

	Small streams	Large streams
Flow rate	fast	slow
Temp	cold	warmer
O2	high	low
Food source	Detritus	Fine organic matter, algae, macrophytes
Feeding styles	shredders	Collectors/filter feeders

Define the major zones of lakes (littoral, limnetic, profundal and benthic), describe their abiotic conditions and dominant organisms

• Benthic: bottom of water

  • crustaceans, microorganisms(bacteria fungi), mollusks

• Photic: surface with light

  • aquatic plants, phytoplankton

• Profundal: anywhere dark

  • Decomposers, crustaceans

• littoral: where photic and benthic meet(edge of lake)

  • Plants, algae

• Limnetic: open, well lit surface layer, away from shore (part of pelagic zone)

  • phytoplankton, small fish, zooplankton

Describe the major impacts that humans have on freshwater ecosystems

• Pollution→ sewage and waste

• habitat destruction- deforestation, urban development

• Dams

• introduced invasive species which outcompete or prey on native species

• Climate change

Define major oceanic zones (det. by ocean depth, light availability, stability of bottom substrate).

a) deep pelagic zone

• zones vary by depth

• light and O2 availibilty key

• pressure is a key stressor at depths 

Deep pelagic zone 

• Below the photic zone, temp decreases, pressure increases

  • deep ocean- no light 

  • thermal vents: hidden hotspots of productivity 

• Sparsely populated. Find detritivores, predators like crustacenans, cephalopds. Sea stars and sea cucumbers graze ocean floor/filter food from water. 

Define major oceanic zones (det. by ocean depth, light availability, stability of bottom substrate).

b) Shallow ocean

• Plenty of light, not too deep

• Warm, nutrient rich waters 

• High biodiversity- find phytoplankton, coral reefs, zooplankton

Define the major oceanic zones as defined by depth and light availability 

c) Benthic zone (ocean floor)

• no light

• Habitats for benthic fish, crabs, sea cucumbers 

• less productive than near-shore zones bc less light and nutrient availbiilty 

Define the major oceanic zones as defined by depth and light availability

d) Photic zone 

• Top parts of ocean where sun can penetrate

• High light (supports photosynthesis)

• Supports highest conc of life, like coral reefs, zooplankton, and fish

Discuss the general characteristics (light availability, substrate, important organisms) of the following oceanic zones/ecosystems:

a) estuaries

• Physical characteristics: have sunlight, occur where rivers flow→ oceans, salinity varies due to mixing of fresh and salt water, highly productive due to sediments and nutrients from terr envts

• Organisms: many juvenile fish spend time here, shellfish, invertebrates

• Substrates: mud and sand

• Threats: pollution carries in rivers (agricultural runoff), development

Discuss the general characteristics (light availability, substrate, important organisms) of the following oceanic zones/ecosystems:

b) Rocky intertidal 

• stable rocky substrate, high light at low tide but can decrease at high tide

• alternating wet and dry conditions, but tidal pools can provide refuge. wave motion challenging. 

• Organisms: algae, and animals that can anchor,

Discuss the general characteristics (light availability, substrate, important organisms)

c) mangroves

• High light in shallow waters, but can be decreased by thick mangrove canopies

• Substrate- muddy and low in oxygen due to tidal fluctuation and fine sediment deposition

• Organisms: Mangrove trees, crabs, snails, shrimp, fish, birds

Discuss the general characteristics (light availability, substrate, important organisms) of

d) coral reefs

• High light (sunlight goes through clear shallow waters)

• Substrate- CaCo3 based reefs

• Organisms- coral species, fish (clownfish, sea urchins, octopus, plankton

Discuss the general characteristics (light availability, substrate, important organisms) of

e) kelp forests

• High light in shallow waters but light availibilty decreases with depth 

• Substrate- rocky where kelp can anchor 

• Organisms: kelp, fish, sea urchins, snails