L7 - Threats and Solutions (freshwater system) Flashcards
What is eutrophication
the nutrient enrichment of water systems caused by fertiliser runoff, erosion of nutrient-rich sediments, or sewage discharge, leading to shifts in species composition in the food chain
what are common sources of organic pollution in freshwater systems
- domestic sewage (raw or treated)
- Farm waste like slurry
- Combined sewage overflows (CSOs)
How does organic pollution affect freshwater ecosystems?
- increase nutrient levels (N and P)
- depletes oxygen levels, harming aquatic life
- leads to decomposition by anaerobic bacteria, producing foul-smelling gases like H2S, NH3 and CH4
- increases biochemical oxygen demand (BOD)
what happens to fish in oxygen depleted water
fish like trout and salmon die when oxygen levels drop below 3mg/L
what is biochemical oxygen demand (BOD)?
BOD is the amount of oxygen required by decomposer bacteria to break down organic material in water, used as a measure of organic pollution
What are combined sewage overflows (CSOs)
systems where storm water, untreated sewage and industrial wastewater are combined and occasionally overflow into water bodies during heavy rains, introducing pollution and bacteria
what is the impact of CSOs on water quality
- increase in nutrients and BOD
- introduction of bacteria
- increase in conductivity in urban streams
- decline in water quality variables like dissolved oxygen (DO)
how do pollutants affect the downstream river ecology
- initial spike in suspended solids, BOD, and salts at the point of discharge
- Gradual decline as self-purification occurs downstream
- Transition from ammonia (NH₄) peaks to nitrate (NO₃) peaks through nitrification
- Algal blooms and increased bacterial populations initially, followed by nutrient depletion and recovery of aquatic life
what is the urban stream syndrome
a concept describing how urbanisation alters stream ecosystems, including channelised rivers, increased runoff from concrete areas, and dominance by pollution-tolerant organisms
what is stewardship in water management
stewardship involved taking responsibility for sustainable water management and ensuring the availability of clean water for current and future generations
what are the sustainable development goals related to water management
- goal 6 = ensure availability and sustainable management of water and sanitation for all
- goal 14 = conserve and sustainably use life below water
what processes are necessary for freshwater protection
- Diagnosis: Identify pollution sources and stressors.
- Treatment: Reduce nutrient concentrations
- Prevention: Improve wastewater treatment, raise awareness, and enforce policies
- Integrated Management: Use catchment-based approaches and partnerships
- Communication: Share research and involve diverse stakeholders
what is the role of environmental regulators
they implement environmental policies, monitor compliance with quality standards, and manage ecosystems based on assessments of environmental state, pressure and management options
why is long-term water quality monitoring important
- To protect freshwater and biodiversity.
- To comply with environmental standards and achieve “good ecological status.”
- To assess trends in variables like ammonia, nitrate, and phosphate levels
what are some biological indices used to monitor water quality
- Biological Monitoring Working Party (BMWP): Assesses organic pollution; operates at the family level.
- WHPT (revision of BMWP): Includes abundance data for more accuracy.
- Shannon-Weaver Diversity Index: Measures diversity across taxa but doesn’t consider ecological needs
