Allometric models effectively predict Saccharina latissima (Laminariales, Phaeophyceae) fresh weight at local scales

Obtaining reliable estimates of algal biomass is key to assessing the contributions of macroalgae to nearshore ecosystems and to monitoring the effects of environmental change on macroalgal-dominated reefs. Using non-destructive methods to estimate macroalgal biomass leaves algal beds intact but requires precise allometric models (e.g., length-weight relationships). In this study, we established allometric relationships for the widespread kelp, Saccharina latissima, in the Salish Sea. Thalli were harvested from five sites across two regions in Southern British Columbia and the abilities of four non-destructive metrics (stipe length, blade length, blade width, and total thallus length) to predict thallus fresh weight were compared. Allometric models were developed for each region for all combinations of thallus metrics to explain thallus fresh weight and models were ranked based on their AICc scores. Finally, using our largest sample (n = 114 individuals), we performed a resampling experiment to determine the appropriate sample size for constructing local models. These models can be developed from as little as 2 hours of field data collection and are inexpensive and effective methods for non-destructively estimating S. latissima biomass.

Automated summary

This study aimed to establish allometric relationships for the widespread kelp Saccharina latissima in the Salish Sea, comparing the abilities of four non-destructive metrics to predict thallus fresh weight and ranking models based on their AICc scores. The appropriate sample size for constructing local models was determined through a resampling experiment, providing inexpensive and effective methods for non-destructively estimating S. latissima biomass.