Coastal eutrophication transforms shallow micro-benthic reef communities

Area of Science:

• Marine Ecology
• Environmental Science
• Microbiology

Background:

• Coastal eutrophication globally degrades coral reefs, reducing coral cover and promoting algal blooms.
• Micro-benthic communities are significantly affected by eutrophication, yet their specific responses remain understudied.
• Foraminifera, diatoms, and bacteria are potential bioindicators of reef health.

Purpose of the Study:

• To investigate the impact of turbidity and eutrophication on micro-benthic communities in the Spermonde Archipelago.
• To compare the sensitivity of foraminifera, diatoms, and prokaryotes to environmental changes along a turbidity gradient.
• To differentiate impacts on shallow reef flat versus deep reef slope communities.

Main Methods:

• Sampling across 12 islands and 600 sites in the Spermonde Archipelago, Indonesia.
• Utilizing environmental DNA (eDNA) metabarcoding for community analysis.
• Analyzing satellite imagery to assess turbidity and habitat variables.

Main Results:

• Reef flat micro-benthic communities were 1.5- to 2-fold more impacted by turbidity than reef slope communities.
• Large benthic foraminifera and diatoms showed high sensitivity to turbidity, contrary to expectations for prokaryotes.
• Prokaryotic communities on reef flats were primarily influenced by substrate type, not water quality.
• 112 exact sequence variants (ESVs) identified as turbidity indicators, with 87 from foraminifera and diatoms in turbid waters.

Conclusions:

• Turbidity and eutrophication significantly shape micro-benthic communities, particularly on reef flats.
• Foraminifera and diatoms are robust bioindicators of turbidity and eutrophication in coral reef ecosystems.
• Micro-benthic communities serve as crucial early warning signals for coral reef degradation.