1467 / 2024-09-27 15:31:18
The Distribution and Photosynthetic Parameters Characteristics of Microphytobenthos in the Intertidal Zones of Coastal China
intertidal zone; microphytobenthos; chlorophyll-a; photosynthetic parameters
Session 28 - Towards a Holistic Understanding of the Ocean's Biological Carbon Pump
Abstract Accepted
It is well known that microalage are important primary producers in the oceans, but their contribution to the intertidal zones can be overlooked. Microphytobenthos, in particular, are essential producers in these areas. This study investigates the spatial distribution and primary productivity characteristics of microphytobenthos in intertidal sediments along the Chinese coastline, based on stratified chlorophyll-a concentration data (0-10 cm) and surface (0.5 cm) photosynthetic parameters measurements obtained during the spring of 2024. Sampling stations were chosen to cover different latitudes and ecological environments. Surface sediment samples were collected at five depth intervals (0-0.5 cm, 0.5-1 cm, 1-2 cm, 2-5 cm, and 5-10 cm) to examine the variation of chlorophyll-a concentration with depth. Additionally, in situ fluorometer was used to measure photosynthetic parameters in the top 0.5 cm sediment, which was suspended by filtered seawater, to assess the photosynthetic activity of microphytobenthos.
Results show that chlorophyll-a concentrations within the surface 0.5 cm ranged from 0.18 to 28.44 μg/g, with an average of 8.87 μg/g. A clear depth-dependent gradient was observed, with average concentrations decreasing from 8.87 μg/g in the top 0-0.5 cm layer to 2.60 μg/g at 5-10 cm, highlighting the dependence of microphytobenthos on light availability. In muddy sediments, chlorophyll-a concentrations showed a positive correlation with latitude, indicating lower biomass in northern regions and higher biomass in the south. However, low chlorophyll-a levels at certain stations suggest regulation by other environmental factors beyond latitude.
Further analysis of chlorophyll fluorescence data revealed spatial differences in photosynthetic efficiency. Fv/Fm values ranged from 0.076 to 0.450, showing no significant correlation with latitude. However, both F₀ and Fₘ fluorescence intensities in the surface 0.5 cm sediment showed a positive correlation with latitude. Additionally, microphytobenthos in sandy sediments exhibited higher F₀, Fₘ, and Fv/Fm values compared to muddy sediments, indicating greater photosynthetic activity and potential in sandy environments. Although the magnitude of productivity cannot be directly represented by photosynthetic parameters, these parameters can effectively serve as indicators of the health and photosynthetic capacity of microphytobenthos.
By analyzing chlorophyll-a concentration and fluorescence parameters in intertidal sediments, this study provides a preliminary qualitative assessment of benthic microphytobenthos biomass and primary productivity potential in different ecological environments along the Chinese intertidal zones. Subsequent studies on the community structure of microphytobenthos and environmental factors will provide crucial data to reveal the primary productivity, ecological function, and contribution of microphytobenthos in intertidal sediments to coastal ecosystems.
Results show that chlorophyll-a concentrations within the surface 0.5 cm ranged from 0.18 to 28.44 μg/g, with an average of 8.87 μg/g. A clear depth-dependent gradient was observed, with average concentrations decreasing from 8.87 μg/g in the top 0-0.5 cm layer to 2.60 μg/g at 5-10 cm, highlighting the dependence of microphytobenthos on light availability. In muddy sediments, chlorophyll-a concentrations showed a positive correlation with latitude, indicating lower biomass in northern regions and higher biomass in the south. However, low chlorophyll-a levels at certain stations suggest regulation by other environmental factors beyond latitude.
Further analysis of chlorophyll fluorescence data revealed spatial differences in photosynthetic efficiency. Fv/Fm values ranged from 0.076 to 0.450, showing no significant correlation with latitude. However, both F₀ and Fₘ fluorescence intensities in the surface 0.5 cm sediment showed a positive correlation with latitude. Additionally, microphytobenthos in sandy sediments exhibited higher F₀, Fₘ, and Fv/Fm values compared to muddy sediments, indicating greater photosynthetic activity and potential in sandy environments. Although the magnitude of productivity cannot be directly represented by photosynthetic parameters, these parameters can effectively serve as indicators of the health and photosynthetic capacity of microphytobenthos.
By analyzing chlorophyll-a concentration and fluorescence parameters in intertidal sediments, this study provides a preliminary qualitative assessment of benthic microphytobenthos biomass and primary productivity potential in different ecological environments along the Chinese intertidal zones. Subsequent studies on the community structure of microphytobenthos and environmental factors will provide crucial data to reveal the primary productivity, ecological function, and contribution of microphytobenthos in intertidal sediments to coastal ecosystems.