Characterization of Chromophoric Dissolved Organic Matter in the Littoral Zones of Eutrophic Lakes Taihu and Hongze during the Algal Bloom Season

Abstract

Chromophoric dissolved organic matter (CDOM) is a key component with a critical role in the littoral zones of eutrophic shallow lakes; yet the characteristics of CDOM in these zones remain seldom systematically reported. In this study, the differences in sources, biogeochemical characteristics, and fates of CDOM between the littoral zones of eutrophic lakes Taihu (LLT; frequently occurring algal blooms and longer lake residence time) and Hongze (LLH; no obvious algal blooms and shorter residence time) were compared during the algal bloom season using ultraviolet-visible spectra and excitation and emission matrix spectroscopy combined with parallel factor analysis. Three humic-like fluorescent dissolved organic matter (FDOM) components (C1, C3, and C4) and one protein-like component (C2) were identified. Results showed that FDOM components were dominated by protein-like fluorescent substances in LLT, and humic-like materials in LLH, respectively. The CDOM in LLT had a lower relative aromaticity and molecular weight, humification degree and a higher autotrophic productivity because of algal blooms. Furthermore, CDOM depletion rates in LLT were higher than those in LLH due to a longer lake residence time in LLT. In addition, CDOM shifted from high molecular weight to low molecular weight as the humification degree decreased during the CDOM depletion process. This comparative study showed that algal blooms and lake residence time were the significant factors for distinguishing characteristics of CDOM between littoral zones of shallow lakes on a similar trophic level. This study provides field-based knowledge for remote sensing CDOM measurement and serves as a reference for lakeshore aquatic environmental management.

CDOM Absorption Properties of Natural Water Bodies along Extreme Environmental Gradients

“…The tendency of an inverse relationship between CDOM absorption and salinity can be seen at our near shore stations (SF, LF, and BS), which are strongly influenced by freshwater outlets, and this tendency is in accordance with Aksnes et al [63], who concluded that Norwegian coastal water has "darkened" due to freshening during the period 1935-2007. Comparison of our mean value for a CDOM (355) (1.27 m −1 ) in the eutrophic LV with mean values for a CDOM (350) in Chinese eutrophic lakes, which varies between 2.75 and 4.57 m −1 [64,65], shows that CDOM concentrations in LV are lower, even though the Chl-a concentrations are at the same level. The trophic state of an aquatic system can be described in terms of concentrations of the dissolved nutrients nitrogen and phosphorus.…”

“…The trophic state of an aquatic system can be described in terms of concentrations of the dissolved nutrients nitrogen and phosphorus. When the concentrations of these nutrients are low (oligotrophic), they limit algal growth, and when they are high (eutrophic), they trigger algal growth, resulting in respectively low and high concentrations of total phosphorus (TP) and Chl-a, and large and small Secchi depths, respectively [65]. For lakes in China, typical a CDOM (355) mean values for oligotrophic, mesotrophic (medium level of nutrients), and eutrophic water bodies are 1.47, 2.75, and 4.21 m −1 , respectively [15].…”

Optical Properties of Dissolved Organic Matter and Controlling Factors in Dianchi Lake Waters

“…Dissolved organic carbon in water could be produced from the disruption or the disintegration of organomineral complexes and could decrease binding of humic acid (HA) or fulvic acid (FA) by metal oxides, osmotic shock, and lysis of microbial cells [3,11,41]. Therefore, part of DOC resulted from bedrock mineralization and erosion along with the degradation of OM by microbial cells, and this kind of collapse effect was most evident at inlets.…”

“…Dissolved organic matter (DOM) plays an important role in carbon biogeochemical cycling and the evolution of water quality in the aquatic system [1][2][3]. DOM generally derives from allochthonous (anthropogenic and terrestrial inputs) and autochthonal sources (microbial and phytoplankton) in the aquatic ecosystem [4][5][6][7][8].…”

“…A better understanding of the structural and the functional properties of DOM may greatly assist our further understanding of the underlying mechanisms responsible for the evolution of water environment quality, complexation, reduction, bioavailability, and mobilization/immobilization of elements with DOM [3,20,21]. Nutrients play an important role in the organic matter cycle, but which moiety in DOM is influenced has scarcely been investigated, as well as which fraction predominates or effectively changes bulk properties and structures [6,[19][20][21].…”