Flow, form, and force: methods and frameworks for field studies of macroalgal biomechanics

Macroalgae are ecologically important organisms that often inhabit locations with physically challenging water motion. The biomechanical traits that permit their survival in these conditions have been of interest to biologists and engineers alike, but logistical and technical challenges of conducting investigations in macroalgal habitats have often prevented optimal study of these traits. Here, we review field methods for quantifying three major components of macroalgal biomechanics in moving water: fluid flow, macroalgal form, and hydrodynamic force. The implementation of some methodologies is limited due to the current state and accessibility of technology, but many of these limitations can be remedied by custom-built devices, borrowing techniques from other systems, or shifting lab-based approaches to the field. We also describe several frameworks for integrating flow, form, and force data that can facilitate comparisons of macroalgal biomechanics in field settings with predictions from theory and lab-based experiments, or comparisons between flow conditions, habitats, and species. These methods and frameworks, when used on scales that are relevant to the examined processes, can reveal mechanistic information about the functional traits that permit macroalgae to withstand physically challenging water motion in their habitats, using the actual fluid flows, macroalgal forms, and physical forces that occur in nature.