Intermittency in processing explains the diversity and shape of functional grazing responses

Area of Science:

• Ecology
• Theoretical Ecology
• Aquatic Ecosystems

Background:

• Consumer feeding response functions are crucial for trophic interaction models but often lack mechanistic derivation.
• Existing models (Ivlev, Holling types I-III) have limitations in representing feeding dynamics.
• Queuing theory offers a framework to mechanistically derive consumer response functions.

Purpose of the Study:

• To apply queuing theory to model plankton feeding behavior and derive a novel grazing function.
• To investigate the influence of prey patchiness and prey size on feeding intermittency.
• To provide mechanistic explanations for different grazing models and refine size-based ecosystem models.

Main Methods:

• Applied queuing theory to model food item processing as two stages with variable synchronicity.
• Derived a novel grazing function incorporating a "shape" parameter to represent feeding intermittency.
• Evaluated hypotheses using empirical data for Acartia tonsa, rotifers, copepods, and ciliates.

Main Results:

• Feeding intermittency, influenced by prey patchiness (e.g., turbulence) and prey size ratio, determines grazing kinetics.
• The novel function explains variations in clearance rates of Acartia tonsa under different turbulence levels.
• Increasing food size enhances intermittency, affecting grazing responses, with potential prey density effects in ciliates.

Conclusions:

• Queuing theory provides a mechanistic basis for understanding feeding intermittency and its impact on grazing functions.
• The derived grazing function offers a more robust representation of consumer feeding responses.
• This approach can refine size-based ecosystem models in plankton ecology.