Partitioning colony size variation into growth and partial mortality

Area of Science:

• Ecology
• Marine Biology
• Organismal Biology

Background:

• Body size is a critical ecological and demographic trait influencing organismal life history.
• Modular organisms, like corals, exhibit complex body size dynamics due to growth and partial mortality.
• Previous studies suggest size-dependent mortality plays a role in coral colony dynamics.

Purpose of the Study:

• To develop a generalizable model for partitioned growth and partial mortality in modular organisms.
• To investigate the relationship between body size, growth, and partial mortality in reef-building corals.
• To identify life-history trade-offs influencing coral demography.

Main Methods:

• Developed a mathematical model to partition net growth into components of growth and partial mortality.
• Applied the model to demographic data from 11 species of reef-building corals.
• Analyzed size-dependency of radial growth increments and partial mortality rates.

Main Results:

• Coral colony extension rates are generally size-independent.
• Partial mortality disproportionately affects smaller coral colonies.
• A significant life-history trade-off between growth and partial mortality was identified, varying with coral growth form.

Conclusions:

• Net coral growth is an allometric outcome of size-independent growth and size-dependent partial mortality.
• Understanding the interplay of growth and mortality provides mechanistic insights into coral demography.
• This framework can help differentiate the impacts of intrinsic (growth) and extrinsic (mortality) factors on coral populations.