Invasive macroalgae in native seagrass beds: vectors of spread and impacts

Area of Science:

• Marine Biology
• Ecology
• Invasive Species Research

Background:

• Marine invasive species spread globally, impacting ecosystems and organisms.
• Human activities are primary vectors, but biological interactions like epibiosis are emerging as significant.
• Understanding novel spread mechanisms is crucial for marine conservation.

Purpose of the Study:

• To investigate limpets as a novel transport mechanism for the invasive alga Sargassum muticum.
• To assess the physiological impact of Sargassum muticum invasion on the seagrass Zostera marina.
• To determine the role of epibiosis in the introduction of invasive species into sensitive marine habitats.

Main Methods:

• Conducted intertidal and seagrass surveys to assess Sargassum muticum-limpet associations.
• Performed a 4-year field study on Zostera marina shoot density, dry weight, and phenolic compounds.
• Utilized laboratory experiments to analyze nutrient partitioning, photosynthetic efficiency (Fv/Fm), and growth of Zostera marina under invasion.

Main Results:

• Sargassum muticum was found attached to limpets on rocky shores (15%) and in seagrass beds (5%).
• Zostera marina exhibited reduced density and phenolic content in areas co-invaded by Sargassum muticum.
• Sargassum muticum did not affect Zostera marina's nutrient partitioning but had variable photosynthetic responses.

Conclusions:

• Limpets serve as epibionts and a previously unrecognized vector for introducing Sargassum muticum into new habitats.
• Reduced phenolics in Zostera marina may compromise its defenses, facilitating Sargassum muticum proliferation.
• Zostera marina shows some resilience to Sargassum muticum, particularly in nutrient sequestration, though photosynthetic impacts warrant further investigation.