Ecological structure and function differs between habitats dominated by seagrasses and green seaweeds

Area of Science:

• Marine ecology
• Coastal ecosystem services
• Habitat dynamics

Background:

• Marine vegetated habitats, such as seagrass meadows, are vital for coastal ecosystems and human welfare.
• Human impacts are causing seagrass meadows to be replaced by other vegetation, like green rhizophytic seaweeds.
• The consequences of these habitat shifts for ecosystem functions and services are not well understood.

Purpose of the Study:

• To compare ecosystem structure and function between seagrass meadows (Cymodocea nodosa) and seaweed-dominated beds (Caulerpa prolifera).
• To assess five ecological proxies: primary production, epifauna, juvenile fish, adult fish, and sediment retention.
• To understand the implications of habitat shifts for coastal ecosystem services.

Main Methods:

• Ecological comparison of Cymodocea nodosa seagrass meadows and Caulerpa prolifera seaweed beds.
• Quantification of primary production using community metabolism.
• Assessment of epifauna and fish (juvenile and adult) abundance, species density, and biomass.
• Measurement of sediment retention as a proxy for sediment stabilization.

Main Results:

• Seagrass meadows showed higher gross primary productivity (1.4x) and sediment stabilization (1.4x) compared to seaweed beds.
• Seagrass meadows supported significantly more small (2.1x abundance) and large (3.6x abundance) fish.
• Seaweed beds had higher epifauna abundance (3.1x) and species density (1.7x) than seagrass meadows.

Conclusions:

• Habitat shifts from seagrass to seaweed dominance alter ecosystem structure and function.
• Different ecosystem functions are not effective surrogates for one another.
• Assessing ecosystem services requires considering multiple, distinct functions rather than relying on a single proxy.