Glossary
Anoxic
Referring to an environment or condition completely devoid of oxygen, which is lethal to most aerobic life forms.
Example:
Deep sediments in highly polluted lakes can become anoxic, allowing only anaerobic bacteria to survive and produce foul-smelling gases.
Biological Oxygen Demand (BOD)
A measure of the amount of dissolved oxygen consumed by microorganisms as they decompose organic matter in water.
Example:
A river receiving untreated sewage would likely show a very high Biological Oxygen Demand due to the large amount of organic waste present.
Chemical Dispersants
Substances used in oil spill cleanup that break down oil slicks into smaller droplets, allowing them to mix with water and potentially degrade more quickly.
Example:
During the Deepwater Horizon incident, Chemical Dispersants were applied to the oil plume, raising concerns about their own environmental toxicity.
Deepwater Horizon Oil Spill
A catastrophic oil spill in 2010 in the Gulf of Mexico, resulting from an explosion on an offshore drilling rig, releasing millions of gallons of crude oil.
Example:
The Deepwater Horizon Oil Spill caused extensive damage to marine life and coastal ecosystems, impacting fisheries and tourism for years.
Disease-Causing Organisms/Toxins
Pathogens (like bacteria or viruses) or harmful chemical substances present in water that can cause illness in humans or aquatic life.
Example:
Monitoring for E. coli, a common Disease-Causing Organism, in recreational waters helps ensure public safety and prevent outbreaks.
Dissolved Oxygen (DO)
The amount of gaseous oxygen dissolved in water, essential for the respiration of aquatic organisms like fish and invertebrates.
Example:
After a heavy rain washes organic matter into a pond, the decomposition process can significantly reduce the Dissolved Oxygen levels, stressing aquatic life.
Eutrophication
The process by which a body of water becomes overly enriched with nutrients, leading to excessive growth of algae and aquatic plants, and subsequent oxygen depletion.
Example:
Agricultural runoff containing fertilizers often causes eutrophication in nearby lakes, resulting in dense algal blooms that block sunlight and consume oxygen when they decompose.
Exxon Valdez Oil Spill
A major environmental disaster in 1989 when an oil tanker ran aground in Prince William Sound, Alaska, spilling millions of gallons of crude oil.
Example:
The remote location of the Exxon Valdez Oil Spill made cleanup efforts extremely challenging, leading to long-term ecological damage to the pristine Alaskan coastline.
Hypoxic
Referring to an environment or condition where oxygen levels are significantly reduced, often to a point that is detrimental to most aerobic organisms.
Example:
The 'dead zones' in the Gulf of Mexico are often hypoxic due to excessive nutrient runoff from the Mississippi River, leading to widespread aquatic mortality.
Indicator Species
Organisms that are highly sensitive to environmental changes and whose presence, absence, or abundance reflects the health or condition of an ecosystem.
Example:
The presence of certain types of macroinvertebrates, like stonefly nymphs, can indicate excellent water quality, making them valuable Indicator Species for stream health.
Nutrient Levels
The concentration of essential elements, primarily nitrates and phosphates, in water bodies, which can become pollutants when present in excessive amounts.
Example:
High Nutrient Levels from agricultural runoff can lead to algal blooms in lakes, disrupting the natural ecosystem balance.
Oxygen Sag Curve
A graphical representation showing the depletion of dissolved oxygen in a river or stream downstream from a pollution source, followed by its gradual recovery.
Example:
After a paper mill discharges organic waste, environmental scientists can plot an Oxygen Sag Curve to visualize how far downstream the aquatic ecosystem is impacted.
Zone of Tolerance
The specific range of environmental conditions, such as temperature or pH, within which an organism can survive and thrive. Outside this range, an organism experiences stress, reduced growth, or death.
Example:
A specific species of fish might have a Zone of Tolerance for water temperature between 15°C and 25°C; temperatures outside this range would cause it stress or even death.