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Coastal and Estuarine Waters: Light Behavior
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Coastal waters get their color primarily due to the presence of CDOM (which is also known in scientific literature as yellow substance and gilvin), which imparts a brown to yellow-brown color to these waters. CDOM is the dissolved product of the decomposition of plant and animal matter from both terrestrial and marine sources that is composed of humic and fulvic acids. These acids form a water-soluble and chemically complex group of compounds termed “humic substances.” As rainfall runoff and melting snow percolate through soils in coastal watersheds, humic substances are extracted and flow into rivers and streams and ultimately to estuaries and nearshore coastal waters.[4,7] Another likely origin for CDOM is from the decomposition of phytoplankton.
Optical Properties of Colored Dissolved Organic Matter (CDOM): Poyang Lake
Published in Yeqiao Wang, Fresh Water and Watersheds, 2020
Chromophoric dissolved organic matter (CDOM), an important component in natural waters, plays a number of key roles in biogeochemical cycle [1–3]. CDOM derived from water environment represents an essential link between aquatic and terrestrial ecosystems. Phytoplankton and macrophytes released by biological degradations are the main autochthonous sources of CDOM in inland aquatic ecosystems [4]. CDOM also plays an important role in the carbon cycle because of its relationship with dissolved organic carbon (DOC), which is the largest organic carbon component in water systems [5]. CDOM strongly absorbs ultraviolet (UV) spectrum [6] and, therefore, protects aquatic ecosystems by blocking harmful UV radiation. On the other hand, CDOM absorbs visible spectrum, especially blue light, which influences the primary production in deep water owing to light limitation. As a consequence, CDOM has a direct impact on water color remote sensing by controlling water optical properties [7]. Absorption spectral analysis has been used for tracing CDOM sources and chemical composition [8]. In recent years, optical properties of CDOM in inland waters have gained attention [9–12]. However, the characteristics of CDOM vary in diverse aquatic ecosystems because of various sources, especially for inland rivers and lakes.
The Fate and Transport of Allochthonous Blue Carbon in Divergent Coastal Systems
Published in Lisamarie Windham-Myers, Stephen Crooks, Tiffany G. Troxler, A Blue Carbon Primer, 2018
Thomas S. Bianchi, Elise Morrison, Savanna Barry, Ana R. Arellano, Rusty A. Feagin, Audra Hinson, Marian Eriksson, Mead Allison, Christopher L. Osburn, Diana Oviedo-Vargas
Aside from microbial degradation previously described, photochemical degradation by sunlight is an important removal process because much of the DOC generated in BCEs is colored. Despite the moniker, blue carbon exported from BCEs to coastal waters is brown. This colored organic matter is termed CDOM and is detected by light absorption and fluorescence (Stedmon and Nelson, 2015). The brown color is derived from humic-like substances, which absorb strongly in the blue region of the electromagnetic spectrum and deep into the ultraviolet (typically measured from 250 to 750 nm). Compounds such as lignin, which have been noted above to be enriched in marsh, mangrove, and seagrass vegetation, and polyphenols (e.g., tannins) give rise to these optical properties. These compounds are also abundant in the HMW fraction of DOM.
Mapping the coloured dissolved organic matter absorption coefficient in a eutrophic reservoir using remotely sensed images
Published in Inland Waters, 2018
Sarah Martins, Karem Chokmani, Enner Alcântara, Igor Ogashawara, Anas El-Alem
CDOM is not directly produced from Chl-a, but both can be correlated in algal bloom situations. CDOM is a by-product of phytoplankton degradation by cyanobacteria, with DOM generation as a consequence of DOC consumption. In this situation, CDOM starts to increase at the approximate middle of the bloom period and decreases a few days after the end of the bloom (Kirchman et al. 1991, Rochelle-Newall and Fisher 2002, Sasaki et al. 2005, Zhang et al. 2009, Matsuoka et al. 2015, Danhiez et al. 2017). This process leads to the weak correlation (R2 = 0.001) between measured and observed field DOC, which is common for complex inland waters because the relationship between them varies in space and time and is strongly dependent on the concentration of the other optically active compounds (Zhu and Yu 2013, Brezonik et al. 2015). This finding could also be justified because water samples were collected during an algal bloom, so the value of should be more related to fulvic acids (Chl-a) than humic acids (DOC; Xue et al. 2017).
Retrieval of water quality parameters of South Andaman coral Islands using remotely operated underwater vehicle
Published in Water Science, 2019
Shanmuga Priyaa S, Ramesh S, Ramadass G A
The CDOM includes naturally occurring water-soluble biogenic and heterogeneous organic substances that are yellow to brown in color. The absorbance spectra often overlap with the spectra of chlorophyll (Aiken, McKnight, Wershaw, & MacCarthy, 1985). However, Strömbeck and Pierson (2001) reported that the absorbance of red light spectrum can be significant. CDOM can be used as an indirect measure of the dissolved organic carbon (DOC) and salinity. In this study, the relation between Kd, TSS, and CDOM provided by Devlin et al. (2009) shown in Equation (14) has been used to derive the CDOM values as S.Fl.U. – standardized fluorescence units.
Limnological characteristics of Lake of the Ozarks (Missouri, USA): long-term assessment following formation of a reservoir series
Published in Lake and Reservoir Management, 2022
John R. Jones, Daniel V. Obrecht, Anthony P. Thorpe
Data were collected at the 6 sites on LOTO identified by Jones and Novak (1981) and the additional 2 sites established in 1984 (Jones and Kaiser 1988) to better describe the longitudinal gradient along the former Osage River channel (the mainstem) below the riverine and transition sites (Fig. 1, sites 6 and 5, respectively). Methods are detailed in previous publications (Jones and Novak 1981, Jones and Kaiser 1988, Jones et al. 2008a, Watanabe et al. 2009) and include total phosphorus (TP, µg/L), total nitrogen (TN, µg/L, initiated in 1983), algal chlorophyll (Chl, µg/L, uncorrected), nephalemetric turbidity (NTU), nonvolatile suspended solids (NVSS, mg/L), volatile suspended solids (VSS, mg/L), total suspended solids (TSS, mg/L, sum of NVSS and VSS), filterable suspended solids (fTSS, mg/L, particles passing through TSS filters measured in 1999 and continuously after 2004; Knowlton and Jones 2000), and nonalgal suspended solids (NAS, mg/L, sum of NVSS and fTSS). Net separation of algal Chl was done using mesh screens into ultraplankton (<11 µm, starting in 1994), nanoplankton (<35 µm, starting in 1999), and >35 µm (by subtraction from total Chl; Graham and Jones 2007, Jones et al. 2008a). These proportions of total Chl were expressed as ultraChl, nanoChl, and Chl > 35 in the text. Colored dissolved organic matter (CDOM) was estimated by the absorption coefficient at 440 nm of water filtered through the TSS filter (starting in 2004; Watanabe et al. 2009). Nonchlorophyll light attenuation (NCLA, 1/m) was calculated using empirical equations from Jones and Hubbart (2011) and Secchi transparency (m). Water residence time was calculated using discharge data gauged below Bagnell Dam (USGS Gauge 06926000, on the Osage River) and the total volume released during the summer months of each year was divided by the average lake volume to arrive at monthly volume-equivalent discharge during the 1980 to 2014 period of study. Monthly totals were used individually combined across the summer months to assess the influence of hydrology on reservoir water quality. Water levels in LOTO are nearly stable during summer, to accommodate recreational activities. A seasonal hydrologic analysis was conducted by Perkins and Jones (2000) and referenced in this summary. Weather data were compiled from the National Weather Service location at Kaiser, MO, Lee C. Fine Memorial Airport, near Bagnell Dam. The Palmer Drought Severity Index (PDSI; NOAA 2019) from region 3 in Missouri was used to characterize dry (negative values) and wet conditions (positive values) over the study period. Values were averaged (arithmetic) over June, July, and August of each year and ranged from −11.4 to +13.4, with a median of 3.4 (n = 35).