Fresh carbon inputs to seagrass sediments induce variable microbial priming responses.

Area of Science:

• Marine microbial ecology
• Coastal biogeochemistry
• Carbon cycling

Background:

• Microbes regulate the marine carbon cycle, but mechanisms driving carbon sequestration in coastal zones are unclear.
• Microbial priming, enhanced carbon remineralisation due to fresh substrate and oxygen, risks CO2 release in coastal ecosystems.
• Seagrass sediments are key carbon sequestration sites vulnerable to priming.

Purpose of the Study:

• To quantify microbial priming in seagrass sediments.
• To identify factors influencing priming and its impact on carbon storage.
• To assess the implications of priming for CO2 release and ecosystem management.

Main Methods:

• Experimental addition of fresh carbon to seagrass sediments.
• Measurement of CO2 release rates from recent and accumulated carbon deposits.
• Analysis of factors influencing priming, including substrate recalcitrance and environmental conditions.

Main Results:

• Addition of fresh carbon stimulated a 1.7- to 2.7-fold increase in CO2 release from seagrass sediments.
• Priming at the sediment surface can be reduced by recalcitrant carbon inputs and low oxygen conditions.
• Disturbance-induced reintroduction of deep sediments to the water column enhances carbon remineralisation.

Conclusions:

• Microbial priming weakens sediment carbon storage capacity in seagrass ecosystems.
• Priming acts as a pathway for CO2 release, particularly in disturbed or degraded habitats.
• Effective management and restoration of seagrass ecosystems can reduce anthropogenic disturbances and bolster carbon sequestration.