Colored dissolved organic matter in coastal waters influenced by the Atchafalaya River, USA: effects of an algal bloom

2008 ◽  
Vol 2 (1) ◽  
pp. 023502 ◽  
Author(s):  
Eurico D'Sa
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Coastal Waters ◽  
Algal Bloom ◽  
Colored Dissolved Organic Matter ◽  
Atchafalaya River

scholarly journals Dynamics of Nutrients and Colored Dissolved Organic Matter Absorption in a Wetland-Influenced Subarctic Coastal Region of Northeastern Japan: Contributions From Mariculture and Eelgrass Meadows

2021 ◽  
Vol 8 ◽  
Author(s):  
Tomonori Isada ◽  
Hiroya Abe ◽  
Hiromi Kasai ◽  
Masahiro Nakaoka
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Coastal Waters ◽  
Light Distribution ◽  
Nutrient Concentrations ◽  
Colored Dissolved Organic Matter ◽  
Absorption Properties ◽  
Study Region ◽  
Seagrass Ecosystem ◽  
Relative Absorption

Coastal oceans interacting with terrestrial ecosystems play an important role in biogeochemical cycles. It is therefore essential to research land–ocean interactions for further understanding of the processes influencing nutrients dynamics in coastal areas. We investigated the seasonal and spatial distribution of nutrient concentrations and light absorption coefficients of colored dissolved organic matter (CDOM), non-algal particles (NAP), and phytoplankton in a wetland-influenced river–eelgrass meadows–coastal waters continuum in the protected and semi-enclosed coastal sea of Akkeshi-ko estuary (AKE) and Akkeshi Bay (AB), Japan from April 2014 to February 2015. The mixing dilution lines of the CDOM absorption coefficient at 355 nm [aCDOM(355)] relative to salinity predicted by two end-members between freshwater and coastal water showed conservative mixing in AB. Silicate concentrations were significantly correlated with salinity and aCDOM(355) in AB in each month except for December 2014. These results suggest that silicate and CDOM in AB primarily originates from wetland-influenced river discharge. However, samples collected from the eelgrass meadows of AKE, where mariculture is developed, showed non-conservative mixing of silicate concentrations and aCDOM(355) with salinity except for June 2014. Elevated phosphate concentrations, probably released from sediments, were also found in the eelgrass meadows of AKE, especially during summer. These results suggest that the metabolic activities of mariculture and seagrass ecosystem significantly contribute to the nutrient cycles and CDOM absorption in AKE and to the distinct water-mass systems inside and outside AKE. The relative absorption properties of NAP [aNAP(443)], phytoplankton [aph(443)], and aCDOM(443) showed that CDOM is the main factor affecting the light distribution in AKE. However, the relative absorption properties varied seasonally in AB because of spring and autumn phytoplankton blooms and ice cover during winter. Significant relationships were observed between the Secchi disk depth (ZSD), aNAP(443), and aCDOM(443). Chl a concentration and aph(443) were not good indicators for predicting ZSD in our study region. These results suggest that incorporating inherent optical properties and CDOM from mariculture and seagrass ecosystem into ecosystem models could improve predictions of light distribution along the freshwater–eelgrass–coastal waters continuum in optically complex coastal waters.

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