Ocean-colour anomalies quantified by the human eye.

Area of Science:

• Oceanography
• Marine Optics
• Phytoplankton Ecology

Background:

• Phytoplankton blooms cause seawater to appear green, enabling ocean colour monitoring.
• Variations in phytoplankton spectral properties and co-occurring substances create ocean colour anomalies, leading to errors in abundance estimates.
• Accurate interpretation of ocean colour data requires understanding these anomalies, but specialized instrumentation is often inaccessible or costly.

Purpose of the Study:

• To demonstrate that low-cost, historical tools can quantify ocean colour anomalies.
• To validate the use of Secchi disk and Forel-Ule colour scale for anomaly detection.
• To highlight the potential of these methods for analyzing long-term oceanographic records.

Main Methods:

• Utilized a Secchi disk to measure water clarity.
• Employed the Forel-Ule colour scale to visually assess seawater colour.
• Applied these tools in the Weddell Sea to quantify a specific ocean colour anomaly.

Main Results:

• Successfully quantified an ocean colour anomaly using the Secchi disk and Forel-Ule colour scale.
• Demonstrated the practical application of these 19th-century tools for modern oceanographic challenges.
• Confirmed that affordable methods can identify complex optical phenomena in seawater.

Conclusions:

• Ocean colour anomalies can be effectively identified using simple, low-cost instruments.
• Historical ocean colour data, collected with such tools, may provide valuable insights into climate-driven changes in marine ecosystems.
• Accessible methods for ocean colour analysis can democratize scientific research and long-term monitoring.