8.2 - Human Impacts on Ecosystems

Range of tolerance

Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive, grow and develop normally. (ex:. pH or temperature range)

Physiological stress

Stress caused when an organism experiences conditions outside its tolerance range (ex: reduced reproductive rate, delayed development) Can lead to death

Coral reef

A structure of calcium carbonate skeletons built up by coral animals in warm, shallow ocean water. Live in a symbiotic relationship with algae that provide them with sugar as an energy source.

Chemical dispersant

Chemicals sprayed to disperse (break up) oil particles from a spill. These chemicals can spread oil out, but can also be toxic themselves.

Heavy metals

metallic elements with a high density that are toxic to organisms at low concentrations (lead, mercury, arsenic, chromium, cadmium)

Litter

Physical garbage (primarily paper and plastic) that is discarded on the ground or in a natural place instead of being placed in a trash can.

sediment pollution

Excessive amounts of soil particles that enter the water as a result of erosion. Increases turbidity, decreasing sunlight penetration & thus photosynthesis. Occurs primarily from urban storm water & agricultural runoff.

Mercury/Methylmercury

A , heavy metal released from the combustion of coal. Mercury is converted into the toxic compound methylmercury by bacteria in waters and soils, which can damage the nervous system and potentially kill organisms.

Dissolved Oxygen (DO)

the amount of free, oxygen gas (O2) in a water source. The more DO in a water source, the more organisms it can support, especially larger fish.

Biological Oxygen Demand (BOD)

The amount of oxygen used up by microorganisms to decompose biological wastes such as manure, plant matter, or human sewage. As BOD increases, DO decreases.

Hypoxia

Low oxygen levels in a body of water, due to increased BOD from biological waste pollution or eutrophication

Dead Zone

a body of water with extremely low oxygen concentration (hypoxia) and very little aquatic life

Oxygen Sag Curve

A graph that shows the relationship between DO level in a water source and the distance from organic waste pollution source. DO increases as distance from the pollution increases.