Dissolved Organic Matter Processing in Pristine Antarctic Streams

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Glacial meltwater significantly impacts downstream ecosystems by introducing dissolved organic matter (DOM).
• Understanding the composition and transformation of glacial DOM is crucial for predicting its fate and ecological impact in aquatic environments.
• Limited knowledge exists regarding the molecular characteristics of DOM in Antarctic glacial streams and its processing before ocean entry.

Purpose of the Study:

• To investigate the molecular composition of dissolved organic matter (DOM) in Antarctic glacial streams.
• To track the downstream transformation of glacial DOM using advanced analytical techniques.
• To identify factors influencing DOM processing and its implications for downstream ecosystems.

Main Methods:

• Utilized UV-vis absorption and fluorescence spectroscopy to analyze DOM optical properties.
• Employed 1H Nuclear Magnetic Resonance (NMR) spectroscopy to determine DOM molecular structure.
• Applied ultrahigh-resolution mass spectrometry for detailed DOM characterization.
• Conducted multivariate statistical analysis (compositional data analysis) on molecular data.

Main Results:

• Glacial DOM is primarily composed of small, microbial-derived biomolecules.
• Downstream processing converts these small molecules into larger, complex structures, with processing extent varying among streams.
• Identified distinct molecular groups within DOM that co-vary along glacial stream paths.
• In-stream lakes increase water residence time, promoting both DOM processing and production.

Conclusions:

• Substantial downstream processing of glacial dissolved organic matter (DOM) occurs in Antarctic glacial streams.
• This processing significantly alters the quantity and lability of DOM substrates entering the marine environment.
• The composition of glacial DOM undergoes significant transformation, influencing nutrient cycling and food web dynamics in receiving waters.