Macrophyte disturbance alters aquatic surface microlayer structure, metabolism, and fate

Area of Science:

• Ecology
• Environmental Science
• Marine Biology

Background:

• Macrophytes are crucial for salt marsh ecosystem functioning.
• Restoration efforts often involve temporary macrophyte clearing.
• The impact of macrophyte removal on the aquatic surface microlayer is not well understood.

Purpose of the Study:

• To investigate how temporary macrophyte clearing affects the aquatic surface microlayer.
• To compare the development, deposition, and breakup of the surface microlayer in cleared and restored salt marshes.
• To assess the impact on metabolic, physical, and chemical processes within the microlayer.

Main Methods:

• Seasonal monitoring of tidal creek surface microlayers in cleared and restored marshes.
• Comparison of metabolic rates (photosynthesis, respiration) in microlayers and underlying water.
• Analysis of organic and inorganic components, including chlorophyll-a and fatty acids, on simulated plant stems.
• Quantification of fiddler crab activity and particulate matter in the microlayer.

Main Results:

• Cleared sites showed significantly less chlorophyll-a on simulated stems.
• Lower photosynthesis and respiration rates were observed in the microlayer of cleared creeks.
• Reduced diversity and concentration of fatty acids indicated smaller microbial communities in cleared sites.
• Fiddler crab activity was higher in cleared areas, potentially consuming edaphic algae.
• Less total particulate matter and earlier dropout from the microlayer were noted in cleared creeks.

Conclusions:

• Temporary macrophyte clearing alters salt marsh surface microlayer dynamics.
• Reduced microbial diversity and altered food web pathways result from macrophyte removal.
• Fiddler crab herbivory plays a significant role in redirecting resources.
• These changes impact sediment deposition and overall ecosystem function during restoration.