Leaf area index (LAI)
The leaf area of all macroalgae collected from the quantitative sampling
quadrats was determined from digital photographs (Canon EOS 600D) using
black calibration quadrats and the image analysis software ImageJ
(Schneider et al. 2012, Version 2.1.0). Single large specimens (e.g.
kelps and kelp like brown algae) were recorded individually whereas all
specimens of most understory algae per replicate were spread out and
photographed together. According to (Lüning, 1969), the leaf area index
(LAI) is the measured leaf area normalized to 1 m² ground. Samples from
0m were not included in the LAI analysis. For very few adult kelp
specimens (A. esculenta and ‘Digitate Kelps’: n = 4) the leaf
area was not measured. In these rare cases, a regression formula between
blade DW and leaf area of representatives of each species was calculated
(Appendix 1) and applied to the respective specimens.