Lecture 6: Organisms: Convergence in fresh water & marine systems Flashcards
the four types of freshwater aquatic systems
- flowing water - streams and rivers
- standing water - lakes and ponds
- wetlands
- estuaries
how do streams form
it forms whenever precipitation exceeds transpiration and evaporation
lotic systems
-rivers and streams
-very sensitive to changes in water flow
river continuum
The continuous combination and growth of streams, to rivers, to the river mouth, and the associated shifts in environments and ecosystems
Riparian zone
Distinct terrestrial vegetation that borders lotic systems and experiences seasonal flooding and an elevated water table
streams
- within streams, riffles and pools represent distinct environments, but they are both low productivity
- food webs are allochthonous
streams - what does it mean that food webs are allochthonous
-the organisms in streams depend on organic input at the base of the food web from outside the system to stay balanced
-this can include leaves and dead materials that fall into the stream
rivers
-becomes more autochthonous as it gets larger
-has a balanced food web, but silt and turbulent water currents can reduce productivity
-Downstream movement of nutrients and life must be balanced by upstream inputs and allochthonous material.
rivers - what does it mean for the river to be autochthonous
nutrients and sunlight support the algal growth from within the river
direct ecological consequences of dams
-Disruption to the nutrient flow to lower regions of the river.
-Habitat conversion/destruction of large upstream adjacent area (the reservoir)
-Nutrient buildup on the upstream side of the dam.
-Movement and dispersal disruption for aquatic life, especially fish migration and reproduction.
standing water - lakes and ponds
-found in glacier depressions, glacier melts and forms the standing water
-subdivided into 3 / 4 distinct ecological zones
lentic systems
-lakes and ponds
standing water - Littoral zone
shallow areas, with rooted vegetation
standing water - Limnetic zone
-open water with floating algae
standing water - Profundal zone
-very deep water with no light
-found only in deep lakes
standing water - Benthic zone
sediment with burrowing and microorganisms
Thermal zone and circulation in temperate lakes
-in most temperate lakes there is thermal stratification
-the surface layer and the deeper layers both have seasonally different temperatures
-a thermocline is present
-most production of biomass occurs in the surface layer where light can pass through for photosynthesis and oxygen levels are high
temperate lakes - what is thermal stratification
there are distinct temperature zones in the lakes
temperate lakes - thermocline
-forms between the warming and circulating surface layer and the more static deeper layer
-this region of rapid temperature change further limits mixing
spring in temperate lakes
winds drive a mixing of layers and distribution of nutrients
spring -> summer in temperate lakes
-thermocline forms
-high production in surface layer
-nutrients become limited and production declines
summer -> autumn in temperate lakes
-thermocline disappears with seasonal cooling
-nutrients mixed with by wind turbulence
autumn -> winter in temperate lakes
winter refuge for organisms in deep water
algal bloom and human impacts in temperate lakes
-summer water heating and fun-offs can lead to algal blooming
-as the algae keeps blooming, the water becomes more covered and vegetation dies
-the oxygen is then used off
-when those organisms die oxygen is released, but the decomposition process burns the oxygen down
-results in no oxygen left for that system
