Chromophoric Dissolved Organic Matter Dynamics Research Articles

Evaluation of wireless sensor networks (WSNs) for remote wetland monitoring: design and initial results

Here, we describe and evaluate two low-power wireless sensor networks (WSNs) designed to remotely monitor wetland hydrochemical dynamics over time scales ranging from minutes to decades. Each WSN (one student-built and one commercial) has multiple nodes to monitor water level, precipitation, evapotranspiration, temperature, and major solutes at user-defined time intervals. Both WSNs can be configured to report data in near real time via the internet. Based on deployments in two isolated wetlands, we report highly resolved water budgets, transient reversals of flow path, rates of transpiration from peatlands and the dynamics of chromophoric-dissolved organic matter and bulk ionic solutes (specific conductivity)-all on daily or subdaily time scales. Initial results indicate that direct precipitation and evapotranspiration dominate the hydrologic budget of both study wetlands, despite their relatively flat geomorphology and proximity to elevated uplands. Rates of transpiration from peatland sites were typically greater than evaporation from open waters but were more challenging to integrate spatially. Due to the high specific yield of peat, the hydrologic gradient between peatland and open water varied with precipitation events and intervening periods of dry out. The resultant flow path reversals implied that the flux of solutes across the riparian boundary varied over daily time scales. We conclude that WSNs can be deployed in remote wetland-dominated ecosystems at relatively low cost to assess the hydrochemical impacts of weather, climate, and other perturbations.

Inversion of Chromophoric Dissolved Organic Matter From EO-1 Hyperion Imagery for Turbid Estuarine and Coastal Waters

The significant implication of chromophoric dissolved organic matter (CDOM) for water quality and biogeochemical cycle leads to an increasing need of CDOM monitoring in coastal regions. Current ocean-color algorithms are mostly limited to open-sea water and have high uncertainty when directly applied to turbid coastal waters. This paper presents a semianalytical algorithm, quasi-analytical CDOM algorithm (QAA-CDOM), to invert CDOM absorption from Earth Observing-1 (EO-1) Hyperion satellite images. This algorithm was developed from a widely used ocean-color algorithm QAA and our earlier extension of QAA. The main goal is to improve the algorithm performance for a wide range of water conditions, particularly turbid waters in estuarine and coastal regions. The algorithm development, calibration, and validation were based on our intensive high-resolution underwater measurements, International Ocean Color Coordinating Group synthetic data, and global National Aeronautics and Space Administration Bio-Optical Marine Algorithm Data Set data. The result shows that retrieved CDOM absorption achieved accuracy (root mean square error (RMSE) = 0.115 m-1andR2= 0.73) in the Atchafalaya River plume area. QAA-CDOM is also evaluated for scenarios in three additional study sites, namely, the Mississippi River, Amazon River, and Moreton Bay, whereag(440) was in the wide range of 0.01-15 m-1. It resulted in expected CDOM distribution patterns along the river salinity gradient. This study improves the high-resolution observation of CDOM dynamics in river-dominated coastal margins and other coastal environments for the study of land-ocean interactive processes.

The Global Distribution and Dynamics of Chromophoric Dissolved Organic Matter

Chromophoric dissolved organic matter (CDOM) is a ubiquitous component of the open ocean dissolved matter pool, and is important owing to its influence on the optical properties of the water column, its role in photochemistry and photobiology, and its utility as a tracer of deep ocean biogeochemical processes and circulation. In this review, we discuss the global distribution and dynamics of CDOM in the ocean, concentrating on developments in the past 10 years and restricting our discussion to open ocean and deep ocean (below the main thermocline) environments. CDOM has been demonstrated to exert primary control on ocean color by its absorption of light energy, which matches or exceeds that of phytoplankton pigments in most cases. This has important implications for assessing the ocean biosphere via ocean color-based remote sensing and the evaluation of ocean photochemical and photobiological processes. The general distribution of CDOM in the global ocean is controlled by a balance between production (primarily microbial remineralization of organic matter) and photolysis, with vertical ventilation circulation playing an important role in transporting CDOM to and from intermediate water masses. Significant decadal-scale fluctuations in the abundance of global surface ocean CDOM have been observed using remote sensing, indicating a potentially important role for CDOM in ocean-climate connections through its impact on photochemistry and photobiology.

Characterizing chromophoric dissolved organic matter in Lake Tianmuhu and its catchment basin using excitation-emission matrix fluorescence and parallel factor analysis

Chromophoric dissolved organic matter (CDOM) is an important optically active substance that transports nutrients, heavy metals, and other pollutants from terrestrial to aquatic systems and is used as a measure of water quality. To investigate how the source and composition of CDOM changes in both space and time, we used chemical, spectroscopic, and fluorescence analyses to characterize CDOM in Lake Tianmuhu (a drinking water source) and its catchment in China. Parallel factor analysis (PARAFAC) identified three individual fluorophore moieties that were attributed to humic-like and protein-like materials in 224 water samples collected between December 2008 and September 2009. The upstream rivers contained significantly higher concentrations of CDOM than did the lake water ( a(350) of 4.27 ± 2.51 and 2.32 ± 0.59 m −1, respectively), indicating that the rivers carried a substantial load of organic matter to the lake. Of the three main rivers that flow into Lake Tianmuhu, the Pingqiao River brought in the most CDOM from the catchment to the lake. CDOM absorption and the microbial and terrestrial humic-like components, but not the protein-like component, were significantly higher in the wet season than in other seasons, indicating that the frequency of rainfall and runoff could significantly impact the quantity and quality of CDOM collected from the catchment. The different relationships between the maximum fluorescence intensities of the three PARAFAC components, CDOM absorption, and chemical oxygen demand (COD) concentration in riverine and lake water indicated the difference in the composition of CDOM between Lake Tianmuhu and the rivers that feed it. This study demonstrates the utility of combining excitation-emission matrix fluorescence and PARAFAC to study CDOM dynamics in inland waters.

Resolving the variability of CDOM fluorescence to differentiate the sources and fate of DOM in Lake Taihu and its tributaries

Taihu Basin is the most developed area in China, which economic development has resulted in pollutants being produced and discharged into rivers and the lake. Lake Taihu is located in the center of the basin, which is characterized by a complex network of rivers and channels. To assess the sources and fate of dissolved organic matter (DOM) in surface waters, we determined the components and abundance of chromophoric dissolved organic matter (CDOM) within Lake Taihu and 66 of its tributaries, and 22 sites along transects from two main rivers. In Lake Taihu, there was a relative less spatial variation in CDOM absorption a CDOM(355) with a mean of 2.46 ± 0.69 m −1compared to the mean of 3.36 ± 1.77 m −1 in the rivers. Two autochthonous tryptophan-like components (C1 and C5), two humic-like components (C2 and C3), and one autochthonous tyrosine-like component (C4) were identified using the parallel factor analysis (PARAFAC) model. The C2 and C3 had a direct relationship with a CDOM(355), dissolved organic carbon (DOC), and chemical oxygen demand (COD). The separation of lake samples from river samples, on both axes of the Principal Component Analysis (PCA), showed the difference in DOM fluorophores between these various environments. Components C1 and C5 concurrently showed positive factor 1 loadings, while C4 was close to the negative factor 1 axis. Components C2 and C3 showed positive second factor loadings. The major contribution of autochthonous tryptophan-like components to lake samples is due to the autochthonous production of CDOM in the lake ecosystems. The results also showed that the differences in geology and associated land use control CDOM dynamics, such as the high levels of CDOM with terrestrial characteristics in the northwestern upstream rivers and low levels of CDOM with increased microbial characteristics in the southwestern upstream rivers. Most of river samples from the downstream regions in the eastern and southeastern plains had a similar relative abundance of humic-like fluorescence, with less of the tryptophan-like and more of the tyrosine-like contributions than did samples from upstream regions.

Biogeneration of chromophoric dissolved organic matter by bacteria and krill in the Southern Ocean

Chromophoric dissolved organic matter (CDOM), the optically active fraction of dissolved organic matter, is primarily generated by pelagic organisms in the open ocean. In this study, we experimentally determined the quantity and spectral quality of CDOM generated by bacterioplankton using two different substrates (with and without photoproducts) and by Antarctic krill Euphausia superba and evaluated their potential contributions to CDOM dynamics in the peninsular region of the Southern Ocean. CDOM was generated by bacteria in all experiments, and the presence of photoproducts influenced both the quantity and the spectral quality of the resultant CDOM. We confirmed a direct link between bacterial production and CDOM generation, which yielded in situ CDOM duplication times from 31 to 33 d. Antarctic krill as a direct source of CDOM was also confirmed experimentally. We estimated that CDOM generation by krill would lead to CDOM duplication times from 0.48 to 0.80 d within krill swarms. Our findings highlight the potential significance of bacteria and Antarctic krill swarms in the generation of CDOM and underscore the dynamic nature of CDOM in this area.

The contribution of phytoplankton degradation to chromophoric dissolved organic matter (CDOM) in eutrophic shallow lakes: Field and experimental evidence

Eight field campaigns in the eutrophic, shallow, Lake Taihu in the summers from 2005 to 2007, and a phytoplankton degradation experiment of 33 days, were carried out to determine the contribution of phytoplankton degradation to CDOM. Significant and positive correlations were found between the CDOM absorption coefficient at 355 nm [ a CDOM(355)], normalized fluorescence emission (QSU) at 450 nm from excitation at 355 nm [ F n(355)], and the chlorophyll a (Chl a) concentration for all eight field campaigns, which indicates that the decomposition and degradation of phytoplankton is an important source of CDOM. In the degradation experiment, the CDOM absorption coefficient increased as phytoplankton broke down during the first 12 days, showing the production of CDOM from phytoplankton. After 12 days, a CDOM(355) had increased from the initial value 0.41 ± 0.03 m −1 to 1.37 ± 0.03 m −1 (a 234% increase), and the Chl a concentration decreased from the initial value of 349.1 ± 11.2 μg/L to 30.4 ± 13.2 μg/L (a 91.3% decrease). The mean daily production rate of CDOM from phytoplankton was 0.08 m −1 for a CDOM(355). Parallel Factor Analysis (PARAFAC) was used to assess CDOM composition from EEM spectra, and four components were identified: a terrestrial-like humic component, two marine-like humic components, and a protein-like component. The rapid increase in marine-like humic fluorophores (C3 and C4) during the degradation experiment suggests that in situ production of CDOM plays an important role in the dynamics of CDOM. The field campaigns and experimental data in the present study show that phytoplankton can be one of the important CDOM producers in eutrophic shallow lakes.

Spectral characterization of chromophoric dissolved organic matter (CDOM) in a fjord (Doubtful Sound, New Zealand)

Doubtful Sound, Fiordland National Park, New Zealand has a stable low salinity layer (LSL) at the surface due to the high annual rainfall and an additional freshwater input from the discharge of a hydroelectric power plant. Chromophoric dissolved organic matter (CDOM) distribution dynamics in this LSL were analyzed using Excitation Emission Matrix (EEM) fluorescence and UV/Vis absorption measurements. The levels of CDOM in surface water in Doubtful Sound were much higher than previously reported for coastal zones. CDOM analyzed by UV/Vis absorbance and EEM fluorescence decreased by about 90% within the first 5 m depth. In the first 5 m, the salinity gradient was extreme (5 – 34 salinity), creating a vertical mixing gradient, which appeared to be stable over time. The spectral slope S and the fluorescence index increased during vertical mixing within the first 5 m depth indicating changes in the CDOM chromophores. Observations during a strong rain event revealed that CDOM in a freshwater stream initially increased, but decreased with additional rain (same flow rate), which is an indication that most CDOM was quickly exported within these catchments. Furthermore, the lower CDOM input after substantial rain diluted the surface CDOM level and created a subsurface CDOM maximum. However, shortly after the rain event (<24 h) the surface CDOM maximum with a steady decrease with depth was restored. The combination of extreme rainfall, pristine temperate rain forest and steep mountains with distinct watersheds creates a highly dynamic environment with very high terrestrial CDOM input. These CDOM dynamics and the high degree of scatter in the linear correlations between CDOM levels and salinity cannot be explained solely in terms of conservative mixing, but suggest that biophysical controls in the catchments and mixing with marine derived CDOM are involved in the dynamics of CDOM in this system.

Seasonal variability in chromophoric dissolved organic matter in the Sakawa River and Sagami Bay, Japan

We investigated the chromophoric dissolved organic matter (CDOM) of river water in the Sakawa River and of surface water in the vicinity of the river’s mouth in Sagami Bay, Japan, during the period from July 2003 to July 2004. Absorption by CDOM was modeled as a logarithmic function. As a qualitative index of CDOM, the slope (S) of this function was estimated for a wavelength range from 280 to 500 nm. As a quantitative index of CDOM, the integration of absorption was determined between 280 and 500 nm (Σ280500aCDOM). High seasonal variability of S values was observed at the marine station. The S values at the upstream stations were related to chlorophyll a concentrations but not to bacterial abundance, whereas the integrated values at upstream stations were correlated with precipitation. Seasonal variability in the integrated values was low at the downstream stations, where the effect of effluent from nonpoint sources and sewage treatment plants was strong. Anthropogenic CDOM at the downstream stations appeared to be degraded by microbial utilization and photodegradation, whereas terrestrially derived CDOM at the upstream stations was less degraded. These qualitative differences in CDOM and the marked effect of dilution by seawater near the Sakawa River mouth suggest that the dynamics of CDOM in riverine and coastal environments should be studied with careful consideration of both spatial and temporal variations, particularly in small estuaries.

Spatial, geomorphological, and seasonal variability of CDOM in estuaries of the Florida Coastal Everglades

This paper demonstrates the usefulness of fluorescence techniques for long-term monitoring and assessment of the dynamics (sources, transport and fate) of chromophoric dissolved organic matter (CDOM) in highly compartmentalized estuarine regions with non-point water sources. Water samples were collected monthly from a total of 73 sampling stations in the Florida Coastal Everglades (FCE) estuaries during 2001 and 2002. Spatial and seasonal variability of CDOM characteristics were investigated for geomorphologically distinct sub-regions within Florida Bay (FB), the Ten Thousand Islands (TTI), and Whitewater Bay (WWB). These variations were observed in both quantity and quality of CDOM. TOC concentrations in the FCE estuaries were generally higher during the wet season (June–October), reflecting high freshwater loadings from the Everglades in TTI, and a high primary productivity of marine biomass in FB. Fluorescence parameters suggested that the CDOM in FB is mainly of marine/microbial origin, while for TTI and WWB a terrestrial origin from Everglades marsh plants and mangroves was evident. Variations in CDOM quality seemed mainly controlled by tidal exchange/mixing of Everglades freshwater with Florida Shelf waters, tidally controlled releases of CDOM from fringe mangroves, primary productivity of marine vegetation in FB and diagenetic processes such as photodegradation (particularly for WWB). The source and dynamics of CDOM in these subtropical estuaries is complex and found to be influenced by many factors including hydrology, geomorphology, vegetation cover, landuse and biogeochemical processes. Simple, easy to measure, high sample throughput fluorescence parameters for surface waters can add valuable information on CDOM dynamics to long-term water quality studies which can not be obtained from quantitative determinations alone.

In situ production of chromophoric dissolved organic matter in coastal environments

The horizontal and vertical distribution of marine humic‐like fluorophore, namely, chromophoric dissolved organic matter (CDOM) fluorescence, was surveyed in Ise Bay, Japan. The distribution patterns of salinity and marine humic‐like fluorescence intensity suggested that riverine humic‐like fluorophore conservatively distributed along with fresh‐sea water mixing in surface water at Ise Bay. However, analysis of mixing behavior of riverine CDOM implied that the 25.1 ± 10.6% in average of bulk marine humic‐like fluorescence intensity of Ise Bay surface waters was derived not from a terrestrial origin but an in situ production. A degradation experiment using natural plankton demonstrated the rapid production of marine humic‐like fluorophore within a day. The results consistently suggested that in situ production of marine humic‐like fluorophore plays an important role in the dynamics of CDOM in coastal environments.

Production of chromophoric dissolved organic matter by Sargasso Sea microbes

Time series of chromophoric dissolved organic matter (CDOM) light absorption coefficients indicate a local origin for a large fraction of the CDOM in the upper water column of the Sargasso Sea. In the present study, we demonstrate that CDOM is produced in bacterial culture experiments using Sargasso Sea water and naturally occurring microbial assemblages. Seawater cultures were prepared and grown at in situ temperatures in the dark for periods of weeks. Selected cultures were treated with amendments including inorganic nutrients, glucose, phytoplankton exudates, and zooplankton excretia. In all experiments, when bacterial biomass increased, CDOM increased during the first week of the experiment, followed by a decrease over a longer period of time. Cultures amended with both glucose and inorganic nitrogen and phosphorus produced more CDOM than controls or cultures amended with glucose or inorganic nutrients alone. However, when complex DOM substrates (derived from phytoplankton or zooplankton cultures) were added to seawater cultures, there was a net accumulation of CDOM over the course of the experiments. These data suggest that, in addition to microbial growth, the quality of the substrate plays an important role in net CDOM production. ‘New’ CDOM produced in culture was spectroscopically similar to CDOM appearing below the surface during summer stratification. The results of the present study support a new paradigm for CDOM in the open ocean, which allows for local origin and significant dynamics. Appreciation of CDOM dynamics will, in turn, add to our understanding of microbial productivity, photochemical rate processes, and ultraviolet radiation availability in the global ocean.

Production of chromophoric dissolved organic matter (CDOM) in the open ocean by zooplankton and the colonial cyanobacterium Trichodesmium spp.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 267:45-56 (2004) - doi:10.3354/meps267045 Production of chromophoric dissolved organic matter (CDOM) in the open ocean by zooplankton and the colonial cyanobacterium Trichodesmium spp. Deborah K. Steinberg1,*, Norman B. Nelson2, Craig A. Carlson3, Anne Prusak4 1Department of Biological Sciences, Virginia Institute of Marine Science, PO Box 1346, Gloucester Point, Virginia 23062, USA 2Institute for Computational Earth System Science, University of California Santa Barbara, Santa Barbara, California 93106, USA 3Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, California 93106, USA 4School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA *Email: debbies@vims.edu ABSTRACT: Chromophoric (or colored) dissolved organic matter (CDOM) has been identified as a major determinant of the optical properties of oligotrophic oceans. The factors controlling distribution of CDOM far from the direct influence of land are not well known, as CDOM abundance and distribution does not directly correlate with phytoplankton productivity or biomass, or with dissolved organic matter (DOM) concentration. As part of a larger study of the dynamics of CDOM in the open ocean, we investigated direct release from plankton as a factor contributing to distribution patterns of CDOM. We measured the production of CDOM by zooplankton (copepods, euphausiids, amphipods, salps, polychaetes), protozoans (colonial radiolaria), and by the colonial cyanobacterium Trichodesmium spp. in the North Atlantic subtropical gyre. Groups of individual species of plankton were incubated and absorption spectra were obtained for their release products. CDOM was produced by all organisms examined, and absorption spectra varied by taxa, with major taxa exhibiting characteristic absorption peaks. Plankton-produced DOM is a source of labile carbon facilitating microbial activity, and CDOM may also serve as photoprotection for near-surface-living organisms. Zooplankton likely play an important role in the CDOM cycle in the Sargasso Sea, directly through release/excretion of CDOM and indirectly by providing a labile substrate (excretia) for microbial-mediated production of CDOM. KEY WORDS: Zooplankton · Trichodesmium · Chromophoric dissolved organic matter · (CDOM) Excretion · Sargasso Sea · North Atlantic Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 267. Online publication date: February 19, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Hydrologic control and diurnal photobleaching of CDOM in a subarctic lake

Changes in the concentration of chromophoric dissolved organic matter (CDOM) were determined over short (hours to days) and medium (weeks) time scales during summer in a shallow, polymictic lake in subarctic Quebec, Canada. CDOM fluorescence (F CDOM ) decreased linearly from mid-June until early August, consistent with the zero-order kinetics expected for photodegradation of organic matter in a regularly mixed lake in which most of the photochemically-active radiation is absorbed by CDOM. A major rainfall event then resulted in a sharp increase in F CDOM back to levels recorded at the start of the study. These changes showed that CDOM concentrations were controlled by the balance between catchment inputs and subsequent photodegradation processes within the lake. Shorter term changes in CDOM concentration were monitored by measuring the penetration of ultraviolet radiation (UVR) using a Satlantic TACCS system moored near the center of the lake and set to monitor down-welling 380 nm irradiance at 10 min intervals. The diffuse attenuation coefficient K d (380) decreased by 12 % during the deployment indicating increased penetration of UVR and the change paralleled the drop in F CDOM over the same period. Many of the daily records showed a significant decline in K d (380) in the near-surface waters over the course of the morning and early afternoon indicating diurnal photobleaching of CDOM, and an increase later in the day consistent with the breakdown of the diurnal thermocline and entrainment of deeper waters. The results illustrate the short and medium term dynamics of CDOM, the importance of diurnal stratification and mixing for photochemical processes, and the variability that aquatic organisms must experience in UV exposure in their natural environment.