Novel crab predator causes marine ecosystem regime shift.

Area of Science:

• Ecology
• Marine Biology
• Invasive Species Research

Background:

• Invasive species disrupt native ecosystems by altering energy flow and food web dynamics.
• Understanding how novel species impact bottom-up (resource) and top-down (consumer) control is crucial.
• Non-indigenous predators can significantly alter ecosystem structure and function.

Purpose of the Study:

• To investigate the ecological impact of the invasive crab Rhithropanopeus harrisii in the Baltic Sea.
• To assess how this novel predator influences bottom-up and top-down control in a previously predator-limited ecosystem.
• To understand the consequences of introducing a new predator on nutrient cycling and biomass production.

Main Methods:

• Field observations and ecological assessments in the Baltic Sea ecosystem.
• Analysis of changes in benthic invertebrate richness and biomass.
• Monitoring of pelagic nutrient levels and phytoplankton biomass.

Main Results:

• The invasive crab Rhithropanopeus harrisii established strong top-down control.
• Benthic invertebrate richness and biomass significantly declined following crab introduction.
• Pelagic nutrients and phytoplankton biomass increased, indicating a shift in ecosystem state.

Conclusions:

• The introduction of R. harrisii altered the Baltic Sea from a bottom-up to a top-down controlled system.
• This shift reduced benthic-pelagic coupling and reallocated nutrients to pelagic zones.
• The invasive crab facilitated a regime shift towards a degraded ecosystem state.