Characterising the sources and fate of dissolved organic matter in Shark Bay, Australia: a preliminary study using optical properties and stable carbon isotopes

Abstract

Low latitude, seagrass-dominated coastal bays, such as Shark Bay, Australia, are potential sources of chromophoric dissolved organic matter (CDOM) to coastal regions. Dissolved organic matter (DOM) is known to influence aquatic nutrient dynamics, microbial community structure, and depth of light penetration in estuarine systems. Shark Bay is a sub-tropical ecosystem with limited freshwater inputs and restricted tidal flushing. As such, much of the DOM is expected to be seagrass-derived. However, combining excitation/emission fluorescence spectroscopy and parallel factor analysis (EEM-PARFAC) with 13C stable isotope analysis of DOM, we found evidence for DOM inputs from terrestrial (riverine and possibly groundwater), autochthonous plankton, macroalgae, and seagrass sources. Isotopic analysis of 13C in DOM supports the idea that seagrass inputs contribute substantially to the DOM pool in Shark Bay, whereas, EEM-PARAFAC data suggests that much of this input is derived from decomposing seagrass detritus and to a lesser extent due to exudation during primary production. We also report increases in DOM concentrations and changes in DOM characteristics with increasing salinity in surface water samples, indicating that evaporation is an important control on DOM concentration and photo-degradation may play a critical role in transforming DOM within the system.

Black Sea dissolved organic matter dynamics: Insights from optical analyses

“…Component C1 agreed best (TCC = 0.988) with a component from the Congo River, associated with low molecular weight (LMW) aliphatic molecules (Lambert et al ). The C1 component is also similar to samples collected from the Baltic and North Seas (Stedmon et al ; Osburn and Stedmon ), fjords, estuaries, streams, and treated water (Stedmon and Markager 2005 a ; Williams et al ; Murphy et al 2011 a ; Cawley et al ; Graeber et al ; Osburn et al ; Shutova et al ), among other samples listed in Table . Component C3 agreed (TCC = 0.959) with a protein‐like component from Antarctic sea ice brines (Stedmon et al ), while C5 agreed well (TCC = 0.972) with a component identified in samples from the Baltic Sea, associated with coastal marine sources (Stedmon et al ).…”

Electrochemical and spectroscopic characteristics of dissolved organic matter in a forest soil profile

“…Peaks in the range of Ex/Em 250-280 nm/320-360 nm were related to soluble microbial by product-like materials and simple phenolic compounds with the conjugated electronic system limited to one aromatic ring (Chen et al, 2003). Peaks in the range of Ex/Em 240-260 nm/380-480 nm as well as of Ex/Em 320-350 nm/400-480 nm were associated with humic-and fulvic-like substances (Cory and Mcknight, 2005;Cawley et al, 2012). As presented in Fig.…”

Microbially-Mediated Fluorescent Organic Matter Transformations in the Deep Ocean. Do the Chemical Precursors Matter?

“…FIC1 has recently been reported as a constituent of terrestrial and aquatic fulvic acids. Different studies devoted to track the origin of the organic compounds using their optical properties have found it in coastal areas around the globe, from Florida (Yamashita et al, 2010b;Brym et al, 2014) to Australia (Cawley et al, 2012), including Arctic rivers estuaries (Walker et al, 2013), the Bay of Liverpool (Yamashita et al, 2011), and even the ballast water of different commercial ships (Murphy et al, 2006). The fluorescent intensity of FIC2 is very similar to the traditional peak-A (Coble, 1996) a humic-like material found in rivers and sensitive to photodegradation (Søndergaard et al, 2003;Stedmon et al, 2007;Walker et al, 2009;Lapierre and del Giorgio, 2014).…”