Tracking polycyclic aromatic hydrocarbons in lichens: It's all about the algae.

Area of Science:

• Environmental Science
• Mycology
• Phycology
• Biomonitoring

Background:

• Lichens, symbiotic organisms of fungi and algae/cyanobacteria, can absorb semivolatile organic compounds (SVOCs) from the atmosphere.
• Polycyclic aromatic hydrocarbons (PAHs) are common atmospheric SVOCs of concern.
• The precise mechanism of PAH accumulation in lichens is not well understood, hindering their standardization as bioindicators.

Purpose of the Study:

• To elucidate the accumulation mechanism of gas-phase polycyclic aromatic hydrocarbons (PAHs) in lichens.
• To determine the specific location of PAH accumulation within lichen tissues.
• To validate the suitability of lichens for standardized air monitoring.

Main Methods:

• Experimental exposure of lichens to gas-phase PAHs.
• Microscopic analysis to identify the localization of accumulated PAHs within lichen structures.
• Washing experiments to assess the persistence of PAHs in lichen tissues.

Main Results:

• Gas-phase PAHs readily penetrate the lichen surface and accumulate within the photosynthetic algal layer.
• PAHs are retained in the algal layer, not in fungal hyphae or on the lichen surface.
• Accumulated PAHs remain in the algal layer even after washing the lichen.

Conclusions:

• The accumulation of PAHs occurs specifically within the algal component of lichens.
• This localized accumulation mechanism supports the use of lichens as reliable bioindicators for gas-phase PAHs.
• The findings address current limitations in air monitoring by providing a standardized approach using lichens.