Impact of seasonal anoxic events on phytoplankton dynamics over the Western Indian shelf: An intra- and inter-annual study
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View abstract on PubMed
Summary
This summary is machine-generated.Coastal deoxygenation significantly alters phytoplankton communities. Certain diatoms thrive in dark, anoxic conditions, impacting marine ecosystems and productivity.
Area Of Science
- Marine Ecology
- Oceanography
- Phytoplankton Biology
Background
- Coastal deoxygenation events, particularly during the late southwest monsoon (LSWM), create hypoxic/anoxic conditions in the Western Indian Shelf.
- These deoxygenation events lead to stratified water columns with distinct oxygen, temperature, and salinity gradients.
Purpose Of The Study
- To investigate the inter- and intra-annual variability of phytoplankton communities during deoxygenation events.
- To understand the impact of seasonal hypoxia/anoxia on phytoplankton abundance and species composition.
- To assess the resilience of specific phytoplankton species to dark, anoxic conditions.
Main Methods
- Monitoring of phytoplankton communities at a shallow station (27m) off Goa from 2020-2023.
- Analysis of water column parameters including oxygen levels, temperature, salinity, and hydrogen sulfide presence.
- Laboratory experiments to determine phytoplankton survival under dark, anoxic conditions.
Main Results
- Phytoplankton abundance and species composition varied annually and within years.
- Higher phytoplankton abundance, dominated by pennate diatoms, was observed in anoxic subsurface waters (<18m depth).
- Specific pennate diatoms (Fragilaria, Pleurosigma, Navicula) showed resilience in dark, anoxic environments, unlike centric diatoms and dinoflagellates found in oxic surface waters.
Conclusions
- Coastal deoxygenation significantly reshapes phytoplankton communities, favoring resilient pennate diatoms in low-oxygen zones.
- Understanding these shifts is critical for predicting marine productivity changes in a warming climate.
- Further research is needed to explore the expanding magnitude of deoxygenation zones and their ecosystem-wide effects.
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