Skip to content

Case Study on Coastal Wetland Eutrophication: Gordon Pass, The Gulf Coast

December 14, 2020

Objective

To examine how coastal wetlands versus urban coastlines impact eutrophication, particularly harmful algal blooms (HABs), using remote sensing techniques off the southwestern coast of Florida.

Key Concepts

  • Eutrophication: Nutrient enrichment in water bodies, leading to excessive algae growth.
  • Harmful Algal Blooms (HABs): Especially Karenia brevis (red tide), producing toxins harmful to humans and marine ecosystems.
  • Remote Sensing: Tools like MODIS-Aqua and Landsat 8 used to track chlorophyll concentrations (a proxy for eutrophication).

Study Area

  • Location: Gordon Pass between:
    • Naples (urban coast)
    • Everglades (wetlands)
  • Regions Analyzed (4km x 4km):
    • Region A: Offshore Urban (North)
    • Region B: Gordon Pass (Middle / Control)
    • Region C: Offshore Wetlands (South)

Methods

  • MODIS-Aqua: 8-day chlorophyll-a data (2005–2020).
  • Landsat 8: High-resolution (30m) imagery from 2014 & 2019, processed via Acolite and SeaDAS.
  • Anomaly Analysis: Compared seasonal chlorophyll values to a 15-year baseline.
  • Ocean Currents: Used to interpret HAB movement patterns.

Key Findings

  • Seasonality: Fall chlorophyll peaks observed consistently.
  • Bloom Year 2019:
    • Region A (urban): Highest chlorophyll levels.
    • Region C (wetlands): Lowest levels.
    • 2014 was a lower bloom year.
  • Wetland Effectiveness:
    • Region C had ~14% less chlorophyll than Region B.
    • Region A had ~16% more than Region B.
    • Wetlands likely help buffer nutrients and reduce HAB impact during extreme bloom events.

Conclusions

  • Coastal wetlands may act as nutrient sinks, reducing the intensity of harmful algal blooms.
  • Urbanized coasts may contribute more nutrients, exacerbating eutrophication.
  • Highlights the importance of Everglades restoration efforts, particularly around water quality management and wetland expansion.

Reflections

  • Remote Sensing Tools: Crucial for analyzing large-scale coastal changes. Landsat 8 was especially helpful for high-resolution analysis.
  • Biggest Challenge: Defining spatial boundaries offshore that reflect true impacts without overlap or distortion.
  • What Could Be Improved: Including more high-bloom and low-bloom years for a stronger statistical case.
  • Key Learning: Accessing and applying remote sensing data (NASA, USGS) to develop and test scientific hypotheses confidently.

Full report available here.