Grazer responses to variable macroalgal resource conditions facilitate habitat structuring

Area of Science:

• Ecology
• Marine Biology
• Paleontology

Background:

• Consumer dietary shifts can alter ecosystem functioning.
• Stromatolites exhibit annual layering, influenced by environmental factors and grazer activity.

Purpose of the Study:

• To investigate seasonal dietary changes in grazer communities within South African stromatolite pools.
• To understand how macroalgal resource availability affects grazer diet composition.
• To determine the implications of these dietary shifts for stromatolite formation and ecological integrity.

Main Methods:

• Stable isotope mixing models were used to analyze the dietary composition of metazoan consumers.
• Seasonal data collection focused on macroalgal characteristics and grazer diets.
• Field observations were conducted in living stromatolite pools.

Main Results:

• Macroalgal bleaching in summer led to a dietary shift in metazoan consumers from macroalgae to a more generalist diet.
• Microalgae, a minor winter food source, became more prominent in grazer diets during summer.
• Seasonal grazing pressure on microalgae influences stromatolite accretion and layering.

Conclusions:

• Seasonal changes in macroalgal resources drive significant dietary shifts in stromatolite grazer communities.
• These dietary shifts have cascading effects on stromatolite ecosystems, particularly influencing the annual layering process.
• Understanding grazer-microalgae-stromatolite interactions is crucial for comprehending stromatolite formation and ecological dynamics.