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Volaric MP, Berg P, Reidenbach MA
An invasive macroalga alters ecosystem metabolism and hydrodynamics on a tidal flat
Non-native macroalgae can dramatically alter the metabolism and flow hydrodynamics of invaded ecosystems. The Japanese seaweed Gracilaria vermiculophylla (also referred to as Agarophyton vermiculophyllum) is a macroalga that has increasingly invaded American and European coastal waters. Volaric and colleagues combined in situ aquatic eddy covariance and profiling acoustic Doppler velocimetry measurements of an invasive Gracilaria mat to quantify its impact on the metabolism and hydrodynamics of a previously bare Virginia (USA) tidal flat. The dense Gracilaria mat significantly increased both tidal flat primary production and respiration, but overall was metabolically balanced. Flow and turbulence were significantly dampened beneath the algal canopy. These conditions are likely favorable to algal growth, suggesting a positive feedback loop that facilitates further algal colonization.