The Amazon Flashcards
Weathering of minerals over time
Minerals easiest to weather are removed first (ex: by rain)
Rate of weathering decreases over time
Freshwater vs ocean saltwater foundational concept
lower salinity, low density river water flows over the top of the higher-salinity water
either saltwater will flow inland or freshwater will push it back beyond the edge of the landmass
Freshwater Niches
differences in abiotic factors create niches in freshwater systems including light, water depth, bed quality, nutrient and oxygen availability
freshwater systems with highest biodiversity have these 4:
varying areas of depth
availabilitly of light
high oxygen levels
high nutrient levels (not too high)
solid rock beds
Drainage basin
high Andes basin has fast flow
but majority of Amazon river flows over a gradual slope
Amazon River facts (5)
exceptionally wide and deep
mainly sand river bed
slow muddy water
low oxygen, few nutrients bc so large
near the equator, high rates of rain
Biodiversity in Amazon
~2500 freshwater fish species found in the Amazon (that’s a lot)
high concentration of mammals, reptile predators
Flood Pulse Effect
the flood cycle of a river interacting with existing abiotic and biotic processes in that river system
regular part of the ecosystem
flood becomes the main driver of what are “Seasons”
Floodplains
largest on Earth
river banks extend 20km, floating meadows
flood cycle can last 6 months
different parts of the basin receive elevated rainfall levels at different times of the year
Floodplain Rocks
much of the rock underlying the Amazon is from before the Cambrian
extremely weathered, few nutrients to erode
However, weathering of young Andes mountain range
Floating Meadows
prolific aquatic plant growth extends over the surface of the water (can’t see water)
plants can grow 20 - 30 cm a day as flood waters rise
many aqautic plants only grow well when the region is fully flooded, mammals rely on flood cycle to eat
Floodplain Forest Ecosystem
species diversity of trees within forest constantly shifting
differ species prefer different depths of water during flooding
changes in sediment deposition rates along different parts of the river
Fish Biodiversity
adapted to use floodwater
ex: accessing terrestrial food, habitat, part of their lifecycle
migratory species can go to lakes that are normally isolated when the river floods
Cons of high nutrients
high productivity leads to eutrophication, low levels of dissolved oxygen, fish die
produces dead zones
however, freshwater fish have evolved traits to mitigate this problem (behavoioral and physical)
Adaptations to survive in low oxygen
air-breathing from the atmosphere - for a long time
migrate between areas of high oxygen
eat fish that can’t breathe
Interspecies Interactions
plants use fish as seed disperses
terrestrial insects into the tree canopy
food resources from terrestrial environments
environmental heterogeneity: different species groups befit at different parts of the cycle
Other processes increasing biodiversity
Diverse origins of water in the Amazon River create niche diversity along the river
Changes to the topography of the drainage basin over time
Parent Rock
orignal rock type, can be transformed to create daughter materials
type of soil characterized by the size and type of rock that make up the rock component
Parent Rock, Sediment, Plants
Young Andes Mountains
old continental crust before the Cambrian
Clearwater, Blackwater, Whitewater
Clear water - common to a freshwater system
Black - high in plant tannins (decaying leaf matter, acidic, low nutrients)
White - Silt and nutrient rich, flows over Precambrian rock, weathered from the Andes
support the riches forests, extends from Andean slopes
Bottom-up effect
Nutrient supply determines how many other species can survive in the ecosystem
*Many species of small fishes migrate between blackwater and whitewater
Andes Uplift
Amazon Rainforest existed way before Andes
completely changed the drainage basin that fed the Amazon river
before Pangea breakup: Amazon basin drained towards Pacific,
Post: raise in elevation in the Andean gradually cut off drainage into Pacific
now flows towards the Atlantic ocean
can tell because some species connected with Pacific, highest species diversity found in Western region of the Amazon
Quaternary Period
repeated cycles of glacier growth and retreat
during drier glacial periods: forests vastly restricted, increased niche heterogeneity
forest refugia: can support forest growth even when harsh climate eliminate forest in other regions
fall in sea level …
fall in sea level will affect the end of the river first
fall in sea level means lower river bed means greater slope for water to flow down means faster flow of freshwater
fall in sea level will speed up flow
Rise in sea level…
will slow down water velocity
slowed water velocity will deposit sediment earlier along the river, raises river bed, shallower slope for water to flow down
River terrace
a fall in river level in a meandering river system will create multiple river terraces as the river meanders
