Abstract
Excitation Emission Matrix (EEM) fluorescence spectra and hydrochemical parameters were measured monthly for a year in the western coastal waters of the Bay of Bengal in a shore normal transect up to the mid-shelf region. The parallel factor analysis of the EEM spectral data showed five fluorescent components, two protein (Tyrosine and Tryptophan protein-like, represented as B and T respectively) and three humic (UV humic, Marine humic and Visible humic-like represented as A, M and C respectively). The B fluorophore was more enriched attributed to bacterial decay of photosynthetically produced organic matter and acted as proxy of primary production. The humic like fluorophores showed significant conservative behavior up to salinity ~31. During the pre-monsoon season, photo bleaching caused significant loss of A and C fluorescence making them deviate from conservative behavior but not from the linear distribution against chlorophyll a. The vertical profiles revealed systematic maxima for the humic fluorophores at depths during pre-monsoon and it is inferred that they owe their origin to phytoplankton.
Highlights
In the aquatic environments, dissolved organic matter (DOM) which is a complex and heterogeneous mixture of components is predominantly contributed by the degradation of plants, bacteria and zooplankton and plays an important role in the global carbon cycle [1]
The excitation emission matrix fluorescence spectroscopy combined with parallel factor analysis can be used to characterization of Chromophoric dissolved organic matter (CDOM) and its quantitative significance in DOM dynamics [2,3,4]
Monthly time series observations were done as a part of the SATellite Coastal and Oceanographic REsearch (SATCORE) project of Indian National Centre for Ocean Information Services (INCOIS) for a year in the coastal waters of Bay of Bengal (BOB) from near shore (10m) to offshore (100m) isobaths
Summary
In the aquatic environments, dissolved organic matter (DOM) which is a complex and heterogeneous mixture of components is predominantly contributed by the degradation of plants, bacteria and zooplankton and plays an important role in the global carbon cycle [1]. The few studies that have been carried out on FDOM dynamics in the coastal waters which are having no direct fresh water inputs from major rivers and for the water column to understand the influence of short term processes e.g., photic [14], and biogeochemical [15] processes and of water masses [16] to the ecosystem. Studies of CDOM dynamics in the coastal waters which are having no direct fresh water inputs from major rivers are scanty. In those regions surface as well as vertical distribution of optical properties may have significant trends due to in situ changes of CDOM. Monthly time series observations were done as a part of the SATellite Coastal and Oceanographic REsearch (SATCORE) project of Indian National Centre for Ocean Information Services (INCOIS) for a year in the coastal waters of Bay of Bengal (BOB) from near shore (10m) to offshore (100m) isobaths
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