Detailed Study Guide on Nutrient Pollution and Aquatic Systems

Campus Closure and Class Logistics

  • Campus will close at 03:15 due to dangerous weather conditions (iced roads).
  • Remaining classes for the day have been canceled.
  • Topics will be lumped together due to previous snow days.
  • Focus for today: Slides on nutrient pollution and its effects in aquatic systems.
  • Upcoming Thursday activity: Students to bring a food item or its wrapper for class discussion.
    • Examples: Any food item, recyclable wrapper; do not overthink this task.
    • Reminders will be posted on Husky CT system.

Biodiversity and Pollution

Overview

  • Previous class discussed biodiversity and extinction forces, focusing on habitat loss and fragmentation.
  • Today’s discussion: Pollution as a significant disruptor of biodiversity.
  • Emphasis on nutrient pollution, its definition, sources, and ecological effects.

Nutrient Pollution

  • Nutrient pollution occurs when excess nutrients are introduced into ecosystems.
  • Key nutrient cycles include:
    • Nitrogen Cycle
    • Phosphorus Cycle
    • Carbon Cycle
    • Water Cycle
Nitrogen Cycle and Pollution
  • Nitrogen is primarily found as nitrogen gas ($N_2$), comprising approximately 78% of the earth's atmosphere.
    • Inert Nature: Nitrogen gas exists in a triple covalent bond, making it relatively inactive until processed by organisms.
    • Key Role: Essential component of proteins; critical for the formation of nucleic acids like DNA and RNA.
Forms of Nitrogen for Plant Uptake
  • Plants must absorb nitrogen in forms other than $N_2$:
    • Ammonium (NH₄⁺)
    • Nitrate (NO₃⁻)
  • Animals acquire nitrogen primarily by consuming plants and other animals.
  • The nitrogen cycle involves several processes:
    1. Nitrogen Fixation: Conversion of nitrogen gas into biologically available forms by nitrogen-fixing bacteria.
    • Example: Cyanobacteria in root systems of plants form a symbiotic relationship, converting $N_2$ into ammonia.
    1. Nitrification: Bacterial conversion of ammonia into nitrite and then into nitrate, which plants can absorb.
    2. Ammonification: Decomposition of organic matter by bacteria and fungi returning ammonium to the soil.
    3. Denitrification: Process in which nitrates are converted back into nitrogen gas, returning it to the atmosphere.
Implications of Nitrogen Cycling
  • Primary Productivity Limitation: The availability of nitrogen directly limits the productivity of primary producers (plants and algae) which in turn affects higher trophic levels.
  • Agricultural Implications: The Green Revolution (1950s-60s) saw an 800% increase in nitrogen fertilizer use, enhancing crop yields by 30-50% but also contributing to environmental damage.
  • Environmental Impact: Incorporating synthetic nitrogen fertilizers results in excess nitrogen leaching into aquatic systems, leading to eutrophication.

Eutrophication and Its Consequences

  • Eutrophication is the process by which water bodies become overly enriched with nutrients, leading to excessive growth of algae (algal blooms).
  • Consequences of Eutrophication:
    • Clouding of water due to dense algae growth.
    • Depletion of dissolved oxygen, leading to hypoxia or anoxia in aquatic systems, causing fish kills and biodiversity loss.
  • Harmful Algal Blooms (HABs): Result from nutrient runoff, leading to toxic algae that can be harmful to both aquatic and terrestrial life. Environmental impacts include decreased water quality and die-offs of aquatic organisms.

Phosphorus Cycle and Pollution

  • Phosphorus (P) is primarily found in rocks (apatite) and does not have a gaseous form like nitrogen.
  • Essential Functions: Key component of DNA, cell membranes, and ATP.
  • Acquisition by Plants: Plants absorb phosphorus primarily as phosphate ($PO_4^{3-}$).
  • Consequences of Phosphorus Pollution: Like nitrogen, excess phosphorus contributes to eutrophication, affecting both freshwater and marine ecosystems.
Current Mining and Erosion Issues
  • Increased human activity through mining and agriculture accelerates phosphorus erosion and runoff, impacting aquatic ecosystems.
  • Finite Resource: If phosphorus continues to be mined at current rates, it may run out in approximately 350 years, with no viable substitutes available.

Specific Human Impact on Aquatic Systems

  • Cultural Eutrophication: Human-driven nutrient loading leading to algal blooms, hypoxia, and overall water quality degradation.
  • Monitoring and Mitigation: Agencies like Connecticut DEEP monitor water quality amidst ongoing eutrophication challenges.
  • Recent Improvements: Upgrades to city wastewater treatment facilities aim to reduce nutrient loading.

Conclusion

  • Understanding the effects of nutrient pollution and its complex processes is essential for addressing the biodiversity crisis and maintaining healthy ecosystems.
  • Personal Responsibility: Reducing fertilizer use, planting native species, and practicing responsible water management can help mitigate nutrient pollution impacts.

Next Topics

  • Discussion of ongoing pollution issues, including plastic pollution and its implications for aquatic systems.
  • The need for continued advocacy for clean water protections, especially concerning wetlands.