Sponge exhalent metabolites influence coral reef picoplankton dynamics

Area of Science:

• Marine biology
• Microbial ecology
• Biogeochemistry

Background:

• Coral reef sponges are key filter feeders, processing organic matter and releasing dissolved metabolites.
• The impact of sponge-derived dissolved metabolites on reef picoplankton communities and nutrient cycling remains largely unknown.

Purpose of the Study:

• To investigate the effects of sponge exhalent on reef picoplankton community composition, diversity, and growth.
• To analyze changes in the dissolved metabolite pool resulting from sponge exhalent exposure.

Main Methods:

• Incubation experiments using sponge exhalent (Niphates digitalis, Xestospongia muta) and control reef seawater.
• 16S rRNA gene sequencing and flow cytometry for picoplankton analysis.
• Metabolomic profiling to assess changes in dissolved metabolites.

Main Results:

• Sponge exhalent significantly altered picoplankton community structure, reducing diversity but increasing growth efficiencies.
• Copiotrophic and denitrifying taxa, such as Marinomonas and Pontibacterium, increased in abundance.
• Sponge treatments showed decreased adenosine, inosine, and ammonium, alongside increased monosaccharides, nitrite, and nitrate.

Conclusions:

• Sponge exhalent supports the growth of efficient, copiotrophic picoplankton, influencing nutrient dynamics in coral reefs.
• These findings highlight the significant, yet underappreciated, role of sponges in structuring microbial communities and nutrient cycling in oligotrophic reef environments.