Table 1.

Summary of traits used in this study

Eco- physiological aspect	Ecological significance	Trait and unit	Related mechanism	Weight
Photosynthetic ability	Investment in photosynthesising structure maximises light capture, increasing productivity. Trade-off: lower investment in structural compounds affects integritya,b	Specific thallus area—STA (mm2 g−1)	High STA increases the proportion of light-absorbing surfacec	0.33
		Surface area to volume ratio -SA:V (mm2 mL−1)	High SA:V increases the proportion of nutrient- and gas- exchange surfaceb	0.33
		Thickness (mm)	Thicker fronds allow survival and draught resistancea,d	0.33
Structure	High ratios of hard structural to soft palatable tissue protects against desiccation and increases recalcitrance, contributing to carbon storage. Trade-off: slows productivityh	Thallus dry matter content—TDMC (ratio)	High TDMC confers structural integritye,f	0.50
		Carbon to Nitrogen ratio—C:N	High C:N confers structural integritye,g	0.50
Space use	Exploration of space, linked to competitive dominance, resource acquisition and habitat provisioni. Trade-off: potentially increases water dragj	Length (cm)	Holds seaweed high in water column, facilitates access to lighta,b	0.25
		Pneumatocysts (yes/no)	Holds seaweed upwards in water column, facilitates access to lightk	0.25
		Branching order (integer)	Increases complexity, may maximise light exposurel and delays desiccationm,n	0.25
		Surface area to perimeter ratio—SA:P	Reversely related to branching order; higher SA:P decreases complexity	0.25

Traits are divided into three groups, according to the eco-physiological aspects of macroalgae and the respective ecological significance. Proposed mechanisms linking traits to ecophysiology are provided. Each trait was assigned a weight for functional diversity metrics so that each of the three aspects of eco-physiology were equally represented

^aCarpenter (1990)

^bLittler and Littler (1980)

^cRoderick et al. (2000)

^dReich et al. (1999)

^eCornelissen et al. (2003)

^fElger and Willby (2003)

^gWeykam et al. (1996)

^hRodriguez et al. (2016)

ⁱSteneck and Dethier (1994)

^jStarko et al. (2015)

^kDromgoole (1981)

^lStewart and Carpenter (2003)

^mHay (1981)

ⁿTaylor and Hay (1984)