Glossary
Algal Bloom
A rapid increase in the population of algae in an aquatic system, often caused by excess nutrients, which can block sunlight and deplete oxygen.
Example:
A vibrant green layer covering the surface of a lake after heavy rains indicates an algal bloom, signaling potential water quality issues.
Anthropogenic Causes
Environmental impacts or changes that are primarily caused or influenced by human activities, rather than natural processes.
Example:
The release of industrial wastewater and agricultural runoff are significant anthropogenic causes of water pollution.
Biodiversity Loss
The reduction in the variety of life forms within an ecosystem, often caused by environmental stressors like habitat degradation or oxygen depletion.
Example:
When eutrophication creates dead zones, the resulting biodiversity loss means fewer species of fish, crabs, and other organisms can inhabit that area.
Dead Zones
Areas in oceans or large lakes where oxygen levels are so low (hypoxic) that most aquatic organisms cannot survive, leading to a significant loss of marine life.
Example:
Fishermen often avoid the dead zones off the coast, as their nets come up empty due to the lack of oxygen supporting any fish or shellfish.
Dissolved Oxygen
The amount of oxygen gas that is physically dissolved in water, essential for the respiration of aquatic organisms like fish and invertebrates.
Example:
Healthy rivers typically have high levels of dissolved oxygen, allowing a wide variety of aquatic insects and fish to thrive.
Eutrophic
Describes a body of water characterized by high nutrient levels, abundant plant and algal growth, and often reduced water clarity and oxygen levels.
Example:
A shallow, warm pond filled with lily pads and green algae is typically a eutrophic ecosystem, rich in nutrients.
Eutrophication
The process where a body of water becomes excessively enriched with nutrients, primarily nitrogen and phosphorus, leading to an overgrowth of aquatic plants and algae.
Example:
The excessive use of lawn fertilizers in a suburban area can lead to eutrophication in a nearby pond, turning its clear water murky green.
Hypoxia
A condition in an aquatic environment where the dissolved oxygen levels are critically low, often below what is necessary to sustain most aquatic life.
Example:
The Gulf of Mexico experiences seasonal hypoxia due to nutrient runoff from the Mississippi River, creating a large area where marine life struggles to survive.
Mesotrophic
Describes a body of water with moderate nutrient levels, exhibiting some plant and algal growth, and representing an intermediate stage between oligotrophic and eutrophic conditions.
Example:
A lake that occasionally experiences small algal blooms but generally maintains good water clarity might be classified as mesotrophic.
Non-Point Sources
Diffuse and widespread sources of pollution that are difficult to identify and regulate, often originating from broad areas like agricultural fields or urban landscapes.
Example:
Rain washing fertilizers and pesticides from many different farms into a river constitutes non-point sources of agricultural runoff.
Nutrients (Nitrogen and Phosphorus)
Essential chemical elements that, when present in excess in aquatic ecosystems, act as fertilizers, stimulating rapid plant and algal growth.
Example:
Farmers often apply nitrogen and phosphorus to their crops to boost yields, but runoff can carry these vital elements into waterways, causing pollution.
Oligotrophic
Describes a body of water with low nutrient levels, clear water, and minimal plant and algal growth, typically supporting a limited but specialized aquatic community.
Example:
High-altitude mountain lakes fed by snowmelt are often oligotrophic, known for their crystal-clear water and sparse aquatic vegetation.
Oxygen Depletion
The reduction of dissolved oxygen levels in water, typically occurring when decomposers break down large amounts of dead organic matter, like decaying algae.
Example:
After a massive die-off of algae, bacteria rapidly consume oxygen during decomposition, leading to severe oxygen depletion that suffocates fish.
Point Sources
Specific, identifiable locations from which pollutants are discharged into the environment, making them relatively easy to monitor and regulate.
Example:
A pipe directly discharging treated wastewater from a municipal sewage plant into a river is a classic example of a point source of pollution.