Polychaete invader enhances resource utilization in a species-poor system

Area of Science:

• Marine ecology
• Ecosystem function
• Biodiversity impacts

Background:

• Ecosystem consequences of biodiversity change are often studied from a species loss perspective.
• The effects of invasive species on ecosystem functions are rarely quantified.
• The Baltic Sea is a species-poor ecosystem where invasive species can have significant impacts.

Purpose of the Study:

• To experimentally quantify the effects of an invasive species on ecosystem functions.
• To measure the incorporation and burial of carbon and nitrogen from a simulated phytoplankton bloom by macrofauna communities.
• To compare the role of an invasive species (Marenzelleria arctia) with native species in nutrient cycling.

Main Methods:

• Used isotope tracers to track carbon and nitrogen.
• Simulated a spring phytoplankton bloom.
• Studied communities of one to four species of deposit-feeding macrofauna, including the invasive Marenzelleria arctia and native species (Monoporeia affinis, Pontoporeia femorata, Macoma balthica).

Main Results:

• Marenzelleria arctia showed rapid growth and high biomass production.
• The invasive species incorporated and buried bloom material at rates similar to native species.
• Multi-species treatments, especially those including the invader, showed higher isotope incorporation (nutrient utilization) than expected, indicating niche complementarity.
• Multi-species treatments had lower biomass increase than expected, suggesting interference competition.

Conclusions:

• Invasive species can enhance the incorporation and burial of organic matter from settled phytoplankton blooms.
• Niche complementarity in resource utilization was a key mechanism, particularly with the invader present.
• Interference competition may dampen overall community biomass despite enhanced nutrient cycling.
• These processes are fundamental for marine productivity.