Partitioning of the diffuse attenuation coefficient for photosynthetically available irradiance in a deep dendritic tropical lake

Abstract

We studied the effects of particulate and dissolved optically active components on the attenuation of photosynthetic active radiation (PAR) in a tropical lake. The temporal and spatial distribution of tripton, Chl-a and a CDOM (440) and their relative contribution to the diffuse PAR attenuation coefficient (Kd) was investigated at 21 sites (dry and wet seasons and two intermediate periods) and at monthly interval at 1 pelagic site. Higher values of Kd were observed during the mixing period, characterized by a higher concentration of tripton and Chl-a compared to the stratified rainy season. In the spatial sampling PAR attenuation was dominated by tripton absorption/scattering (average relative contribution of 79%), followed by Chl-a (average 11.6%). In the monthly sampling tripton and Chl-a accounted for most of the Kd with relative contributions of 47.8% and 35.6%, respectively. Multiple linear regression analysis showed that Chl-a and tripton in combination explained 97% of the monthly variation in Kd (p<0.001), but Chl-a had more influence (higher regression coefficient). Thus, although most of light attenuation was due to tripton, seasonal variations in phytoplankton abundance were responsible for most of the temporal fluctuations in Kd.

River Metabolism along a Latitudinal Gradient across Japan and in a global scale

“…In addition, with increasing stream order, rivers tend to receive more suspended particles and organic matter that increase the attenuation coefficient of light. In this study, we used PAR at the river surface and did not consider the attenuation coefficient of light in the river water 46,47 . Thus, the actual light level received by the autotrophs in rivers may have been not proportional to PAR at the surface.…”

Inherent Optical Properties based Vulnerability Assessment of Euphotic Zone Compression in peatland influenced Southeast Asian coastal waters

“…These photosynthetic organisms have a narrow range of blue and blue-green wavelengths to absorb effectively (Prieur and Sathyendranath, 1981). The implications of light scarcity may propagate to higher trophic levels and impact the ecosystem function (Brandao et al, 2017). Policymakers require two kinds of information for coastal and offshore planning.…”

“…The high attenuation and poor water quality due to the enhanced terrestrial run-off are considered a threat to coastal ecosystems (Fredston-Hermann et al, 2016;Jones et al, 2021). The effects of photic compression will exacerbate the vulnerability of coastal and marine species, habitats, and ecosystems (Gattuso et al, 2006;Brandao et al, 2017;Jones et al, 2021). Vertically compressed coral depth distributions have been reported in Singapore's turbid reef systems located in the central Sunda Shelf Sea (Morgan et al, 2020).…”