Dissolved organic matter signatures vary between naturally acidic, circumneutral and groundwater-fed freshwaters in Australia

Authors

Aleicia Holland, La Trobe University, CSIRO Land and Water, University of WollongongFollow
Jenny Stauber, CSIRO Land and WaterFollow
Chris M. Wood, University of British Columbia
Melanie Trenfield, Environmental Research Institute of the Supervising Scientist
Dianne F. Jolley, University of WollongongFollow

RIS ID

124496

Publication Details

Holland, A., Stauber, J., Wood, C. M., Trenfield, M. & Jolley, D. F. (2018). Dissolved organic matter signatures vary between naturally acidic, circumneutral and groundwater-fed freshwaters in Australia. Water Research, 137 184-192.

Abstract

Dissolved organic matter (DOM) plays important roles in both abiotic and biotic processes within aquatic ecosystems, and these in turn depend on the quality of the DOM. We collected and characterized chromophoric DOM (CDOM) from different Australian freshwater types (circumneutral, naturally acidic and groundwater-fed waterways), climatic regions and seasons. CDOM quality was characterized using absorbance and fluorescence spectroscopy. Excitation emission scans followed by parallel factor (PARAFAC) analysis showed that CDOM was characterized by three main components: protein-like, fulvic-like and humic-like components commonly associated with various waters globally in the Openfluor database. Principal component analysis showed that CDOM quality varied between naturally acidic, circumneutral and groundwater-fed waters, with unique CDOM quality signatures shown for each freshwater type. CDOM quality also differed significantly within some sites between seasons. Clear differences in dominant CDOM components were shown between freshwater types. Naturally acidic waters were dominated by highly aromatic (as indicated by the specific absorbance co-efficient (SAC₃₄₀) and the specific UV absorbance (SUVA₂₅₄) values which ranged between 31 and 50 cm² mg^-1 and 3.9 -5.7 mg C^-1 m^-1 respectively), humic-like CDOM of high molecular weight (as indicated by abs_254/365 which ranged from 3.8 to 4.3). In contrast, circumneutral waters were dominated by fulvic-like CDOM of lower aromaticity (SAC₃₄₀: 7-21 cm² mg^-1 and SUVA₂₅₄: 1.5-3.0 mg C^-1 m^-1) and lower molecular weight (abs_254/365 5.1-9.3). The groundwater-fed site had a higher abundance of protein-like CDOM, which was the least aromatic (SAC₃₄₀: 2-5 cm² mg^-1 and SUVA₂₅₄: 0.58-1.1 mg C^-1 m^-1). CDOM was generally less aromatic, of a lower molecular weight and more autochthonous in nature during the summer/autumn sampling compared to winter/spring. Significant relationships were shown between various CDOM quality parameters and pH. This is the first study to show that different freshwater types (circumneutral, naturally acidic and groundwater-fed) contain distinct CDOM quality signatures in Australia, a continent with unique flora and geology.

Grant Number

ARC/DE160100628