CHES BAY TEST Flashcards
Resilience
an ecosystem’s natural ability to resist big changes, including both fast improvements or worsening water quality
homeostasis (as related to resilience)
ability to maintain consistent and predictable conditions
Threshold
a tipping point in which an ecosystem suddenly shifts from one state to another e.g., healthy vs. eutrophic
Pre 1970s Bay
Bay was in a static condition but we were continuing to put pollutants in
1970s and beyond Bay
Degradation and declining resilience
Shift one state to a different one - normal productivity to Cultural Eutrophication
Impact of thresholds on Bay future restoration
May take more to get there than to stay there
pushing the ball up the hill
Hurricane Agnes in 1972
big decrease in water quality (more N, P, sediment) and wiped out much of the Bay’s underwater grass populations, and they have not recovered much since
High Resilience
Population has mechanisms to withstand environmental stress (euryhaline) and continue to grow
Low Resilience
Already near “tipping point”
Population has limited tolerance to environmental stress (stenohaline)
Healthy Bay characteristics
- Submerged aquatic vegetation provides oxygen, food, shelter for animals in Bay
- Clear water
Degraded Bay characteristics
- Nutrients from runoff feed algal blooms and decrease water clarity
- Dying phytoplankton are eaten by bacteria, which uses up a lot of oxygen that marine life can’t use to survive
why resilience and thresholds can work to both disadvantage and advantage
- can slow cleanup efforts, because once the ecosystem passes a tipping point, it’s difficult to push the ecosystem back to its previous state
- when ecosystems are healthy, e.g., thick underwater grasses, they can withstand severe storm and improve surrounding water quality
How many segments in the Bay
92
Why we need to control N & P
- too much phytoplankton + algal blooms
- algae die off and sink to bottom, where consumed by bacteria (consumes oxygen) –> anoxic conditions
- sunlight can’t get through to bottom waters
- submerged vegetation don’t get sunlight and die –> less spawning/nursery grounds
point source
any single identifiable, confined and discrete source from which pollutants are discharged, such as a pipe. Requires NPDES permit to operate
what is excluded from point source
agricultural stormwater discharges and return flows from irrigated agriculture
nonpoint source
diffuse pollution – e.g., urban stormwater. a city street during a thunderstorm. As rainwater flows over asphalt, it washes away drops of oil that leaked from car engines, particles of tire rubber, dog waste, and trash. The runoff goes into a storm sewer and ends up in a nearby river.
point source examples
sewage treatment plants
oil refineries
car manufacturers
nonpoint examples
Developed Lands/Urban Stormwater
Atmospheric Deposition
Agriculture
sources of N&P
Atmospheric Deposition of N Urban & Septic Ag. Crop (fertilizer) Ag. Animal (manure) Urban SW
the largest growing sector for N&P
urban and suburban stormwater from impervious surfaces
Atmospheric deposition contributes ___% nitrogen to Bay. ___% of that is from industry (cars, utilities)
33, 19
Ag fertilizer and Ag manure contribute ___% and ___% nitrogen to Bay
15, 17
Municipal/industrial wastewater contributes ___% nitrogen to Bay
19
Ag fertilizer and Ag manure contribute ___% and ___% phosphorous to Bay
19, 26
Municipal/industrial wastewater contributes ___% phosphorous to Bay
21
Urban/suburban runoff contributes ___% phosphorous to Bay
31
Most (60%) sediment comes from
Ag
Nitrogen contribution by sector
Ag - 38%
Point source - 19%
Urban/Surburban runoff - 29%
Phosphorous contribution by sector
Ag - 45%
Point source - 21%
Urban/Surburban runoff - 31%