oa Direct Detection of Phycocyanin in Sediments by Hyperspectral Imaging

Cyanobacteria, ancient aquatic organisms, are crucial to ecosystems but also linked to harmful algal blooms. Understanding the history of these blooms is vital for ecosystem management, and lake sediment cores offer valuable historical records. Phycocyanin, a cyanobacteria-specific pigment, is a promising biomarker for reconstructing past blooms, but its extraction and measurement from sediment are challenging.

This study explores hyperspectral imaging (HSI) as a novel, non-destructive method for detecting and quantifying phycocyanin in lake sediments. Experiments demonstrated HSI’s ability to detect phycocyanin via a specific absorption trough at 620nm. We calibrated a spectral index (RABD620) using phycocyanin standards in different sediment types with varying water content, also accounting for potential interference from chlorophylla.

Results showed a strong correlation (R² 0.37-0.997) between the RABD620 index and phycocyanin levels in both organic-rich and mineral-rich sediments, indicating the potential for in-situ measurement of phycocyanin concentrations directly on sediment cores. While factors like water and chlorophyll a can influence the signal, HSI offers a rapid and non-destructive approach for studying past cyanobacterial blooms, with applications in ecosystem health assessment and environmental monitoring.