Freshwater Ecology Flashcards
What is limnology?
Study of inland water
Characteristics of upland rivers
- Fast flowing
- Incised course
- High O2 levels
- Cooler water temp.
- Bedrock and coarse sediments
- Clear
- Nutrient poor
- Fauna with limited temp. tolerances, high O2 needs
- Strong swimming ability and specialized strategies to prevent being swept away.
Characteristics of lowland rivers
- Slower flowing
- Meandering course
- Lower O2 levels.
- Higher water temp.
- Fine sediments, organic matter
- Turbid
- Nutrient rich
- Fauna with broad temp. tolerances and greater tolerances to low O2 levels.
- Ecologies revolving around fine sediments or alternative habitats such as submerged woody debris or macrophytes.
Define littoral zone and limnetic zone
Litteral zone - shallow light reaches the bottom.
Limnetic zone- open water habitat for free swimming organisms.
Behaviour of thermoclines in summer
During summer, warm (less dense) water will sit on top of colder, denser water with a thermocline seperating them. The warm layer is called the epilimnion and the cold layer is called the hypolimnion.
Very little mixing of cold and warm water occurs as a stable system exists, particularly in calm weather.
Behaviour of thermoclines in winter
As temp. of surface water drops during winter, a point is reached where the density of the cooling surface water becomes greater than the density of the deep water, and overturning begins as the dense surface water moves down under the influence of gravity. This process is aided by wind or any other process (e.g. currents) that agitates the water.
Oligotrophic environments
- Low nutrient levels (upland rivers)
- Deeper
- Summer O2 in hypolimnion present
- High species diversity in algae, low density and productivity.
- Algal blooms are rare
- Animal produuction is low
- Salmonids (trout and char) often present
Eutrophic environments
- High nutrient levels
- Shallower
- Summer O2 in hypolimnion is low, sometimes absent.
- Low species diversity with high density and productivity
- Algal blooms are frequent
- Animal production is high
- Coarse fish (perch, roach, bream) often dominant.
Emergent vs submergent plants
Emergent plants are rooted in the ground with their stems, flowers and leaves rising above the water
Submergent plants grow with all or most of their leaves and stems below the water surface. They may be rooted in the lake bottom or free floating in the water.
Phytoplankton and periphyton
Phytoplankton - live in water column, produces O2 during photosynthesis. At the base of foodweb within water ecosystems.
Periphyton- A mixture of algae, cyanobacteria, heterotrophic microbes, and detritus attached to submerged surfaces in most aquatic ecosystems.
Main groups of algae found in freshwater?
1) Green algae
2) Red algae - uses different part of light spectrum. It is able to grow in places where other algae can’t, so tends to be found in shaded places such as under rocks or banks
3) Cyanobacteria- Chlorophyll in cyanobacteria isnt in chloroplast but rather diffused throughout the cell. Pigments, other than chlorophyll contribute to their colouration, so cyanobacteria are not usually bright green.
4) Diatoms- mats of brown growth, fluffy masses or slimy layers on rocks are some of the ways diatoms appear to the naked eye.
Define point source pollution
Can be traced back to a single origin or source such as a sewage treatment plant discharge. May also result from spills and deliberate dumping of pollutants into water sources.
Diffuse pollution
1) Agriculture - increases in nutrient levles can result in toxic algal blooms
2) Urban environments - Run-off from impermeable surfaces can be highly polluting. Run off may carry toxic metals, pesticides, oils and HCs, sediments, and O2 depleting substances.
Unlike point-source pollution, it is not as easy to control diffuse pollution by issuing licenses or permits.
Define eutrophication and artifical eutrophication.
Eutrophication- enrichment of waters by inorganic plant nutrients, especially nitrogen and phosphorous which results in an increase of primary production.
Artifical eutrophication- increase in nutrients from human activities.
Effects and problems of eutrophication?
1) Species diversity often decreases and dominant biota change
2) Plant and animal biomass increases
3) Turbidity increases
4) Rate of sedimentation increases, shortening lifespan of the lake
5) Anoxic conditions develop
Problems:
1) The water my be injurious to health
2) Amenity value of water may decline
3) Increased vegetation may impede water flow and navigation
4) Commercially important species of fish may disappear
5) Treatment of drinking water may be difficult
