scholarly journals Effects of food concentration and diet on chromophoric dissolved organic matter accumulation and fluorescent composition during grazing experiments with the copepod Calanus finmarchicus

2004 ◽  
Vol 61 (4) ◽  
pp. 542-551 ◽  
Author(s):  
Juanita Urban-Rich ◽  
James T McCarty ◽  
Mark Shailer
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Exponential Growth ◽  
Life Stage ◽  
Food Concentration ◽  
Prorocentrum Minimum ◽  
Calanus Finmarchicus ◽  
Food Type ◽  
Chromophoric Dissolved Organic Matter ◽  
Effects Of Food Concentration

AbstractLaboratory experiments were conducted with Calanus finmarchicus copepodites IV–V to examine the effects of food concentration, food type, and life stage on chromophoric dissolved organic matter (CDOM) release from copepods. Changes in CDOM absorption and fluorescence were monitored by incubating copepods in rotating bottles for 24 h in the dark with controlled diets. Copepods were fed a range of food concentrations from 800 to 15 000 cells l−1 of either Thalassiosira weissflogii and Skeletonema costatum or Prorocentrum minimum in stationary and exponential growth phases. Results from these studies indicate that diet does have an effect on the amount and type of CDOM released by C. finmarchicus. A diet of either diatoms or dinoflagellates in exponential growth will result in a release of humic-like material, while feeding on senescent cells leads to a net input of protein-like material. Only at very high senescent cell concentrations (>5000 cells l−1) can humic-like material accumulate. This could lead to seasonal cycles in the amount and type of CDOM released by copepods, such that humic-like material will be released in the spring and at the height of phytoplankton blooms, while protein-like material will be added to the water as the bloom dies. The humic-like material found in these studies is blue-shifted compared to the standard humic material (Peaks A, M, and C) measured in seawater. The role of this humic-like material in the environment is currently unknown, but it could be important in absorbing UV radiation.

scholarly journals Net Production and Consumption of Fluorescent Colored Dissolved Organic Matter by Natural Bacterial Assemblages Growing on Marine Phytoplankton Exudates

2011 ◽  
Vol 77 (21) ◽  
pp. 7490-7498 ◽  
Author(s):  
Cristina Romera-Castillo ◽  
Hugo Sarmento ◽  
Xosé Antón Álvarez-Salgado ◽  
Josep M. Gasol ◽  
Celia Marrasé
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Growth Phase ◽  
Exponential Growth ◽  
Prorocentrum Minimum ◽  
Marine Phytoplankton ◽  
Exponential Growth Phase ◽  
Phytoplankton Species ◽  
Colored Dissolved Organic Matter ◽  
Content Type

ABSTRACTAn understanding of the distribution of colored dissolved organic matter (CDOM) in the oceans and its role in the global carbon cycle requires a better knowledge of the colored materials produced and consumed by marine phytoplankton and bacteria. In this work, we examined the net uptake and release of CDOM by a natural bacterial community growing on DOM derived from four phytoplankton species cultured under axenic conditions. Fluorescent humic-like substances exuded by phytoplankton (excitation/emission [Ex/Em] wavelength, 310 nm/392 nm; Coble's peak M) were utilized by bacteria in different proportions depending on the phytoplankton species of origin. Furthermore, bacteria produced humic-like substances that fluoresce at an Ex/Em wavelength of 340 nm/440 nm (Coble's peak C). Differences were also observed in the Ex/Em wavelengths of the protein-like materials (Coble's peak T) produced by phytoplankton and bacteria. The induced fluorescent emission of CDOM produced by prokaryotes was an order of magnitude higher than that of CDOM produced by eukaryotes. We have also examined the final compositions of the bacterial communities growing on the exudates, which differed markedly depending on the phytoplankton species of origin.AlteromonasandRoseobacterwere dominant during all the incubations onChaetocerossp. andProrocentrum minimumexudates, respectively.Alteromonaswas the dominant group growing onSkeletonema costatumexudates during the exponential growth phase, but it was replaced byRoseobacterafterwards. OnMicromonas pusillaexudates,Roseobacterwas replaced byBacteroidetesafter the exponential growth phase. Our work shows that fluorescence excitation-emission matrices of CDOM can be a helpful tool for the identification of microbial sources of DOM in the marine environment, but further studies are necessary to explore the association of particular bacterial groups with specific fluorophores.

scholarly journals Posidonia oceanica as a Source of Chromophoric Dissolved Organic Matter for the Oligotrophic NW Mediterranean Coast

2020 ◽  
Vol 8 (11) ◽  
pp. 911
Author(s):  
Francesca Iuculano ◽  
Carlos M. Duarte ◽  
Jaime Otero ◽  
Xosé Antón Álvarez-Salgado ◽  
Susana Agustí
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Rocky Shore ◽  
Posidonia Oceanica ◽  
Mediterranean Coast ◽  
Balearic Islands ◽  
Chromophoric Dissolved Organic Matter ◽  
Absorption Increase ◽  
Seagrass Meadows ◽  
Nw Mediterranean

Posidonia oceanica is a well-recognized source of dissolved organic matter (DOM) derived from exudation and leaching of seagrass leaves, but little is known about its impact on the chromophoric fraction of DOM (CDOM). In this study, we monitored for two years the optical properties of CDOM in two contrasting sites in the Mallorca Coast (Balearic Islands). One site was a rocky shore free of seagrass meadows, and the second site was characterized by the accumulation of non-living seagrass material in the form of banquettes. On average, the integrated color over the 250–600 nm range was almost 6-fold higher in the beach compared with the rocky shore. Furthermore, the shapes of the CDOM spectra in the two sites were also different. A short incubation experiment suggested that the spectral differences were due to leaching from P. oceanica leaf decomposition. Furthermore, occasionally the spectra of P. oceanica was distorted by a marked absorption increase at wavelength < 265 nm, presumably related to the release of hydrogen sulfide (HS−) associated with the anaerobic decomposition of seagrass leaves within the banquettes. Our results provide the first evidence that P. oceanica is a source of CDOM to the surrounding waters.

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