Estimating growth parameters from growth rate data : Problems with marine sedentary invertebrates

Area of Science:

• Ecology
• Marine Biology
• Quantitative Biology

Background:

• Non-linear growth curves are common in biological systems.
• The choice of growth model can significantly impact interpretations of biological growth.
• Sigmoid growth patterns, characterized by an initial slow phase, acceleration, and then deceleration, are prevalent in many organisms.

Purpose of the Study:

• To investigate how measurement time intervals affect observed growth rates in non-linear growth curves.
• To analyze the potential misapplication of the von Bertalanffy growth equation to sigmoid growth patterns.
• To highlight the challenges in accurately estimating growth parameters for organisms with microscopic early stages.

Main Methods:

• Analysis of growth rates derived from sigmoid (logistic) and non-sigmoid (von Bertalanffy) growth equations.
• Examination of how growth rate data plotted against initial sizes can obscure the inflection point of sigmoid curves.
• Consideration of data limitations when fitting growth models to observed growth rates.

Main Results:

• Observed growth rates are dependent on the time interval of measurement.
• The von Bertalanffy growth equation may inaccurately represent sigmoid growth, particularly when early microscopic stages are not observed.
• The inflection point of sigmoid growth curves can be underestimated when using non-instantaneous growth rate data.

Conclusions:

• The fitting of the von Bertalanffy growth equation to marine macro-benthos data may yield misleading results due to their sigmoid growth and microscopic initial stages.
• Extrapolation of the von Bertalanffy growth equation to smaller stages requires careful, independent validation.
• Accurate representation of biological growth necessitates careful consideration of the underlying growth curve shape and data sampling intervals.