Prof. Dominique Davoult1, Dr Lydia White1
1Sorbonne Université, Roscoff, France
Accurate estimates of primary productivity of macroalgae are needed to predict the consequences of current invasive species expansions and climate-related range shifts for coastal ecosystem functioning. We examined the potential impacts of observed climate-driven shifts in the relative abundances of foundation species within a temperate reef system. We estimated primary productivity rates of 3 co-occurring kelp species, the cold-temperate kelp Laminaria hyperborea, the warm-temperate Laminaria ochroleuca and the introduced Undaria pinnatifida, present in Brittany (France) at contrasting regions of their ranges (centre, leading-edge and invasive, respectively) via in situ photorespirometry. Lamina tissues of cold-temperate L. hyperborea and warm-temperate L. ochroleuca had similar rates of net productivity. Stipes of L. hyperborea, however, displayed much higher rates of productivity and respiration than L. ochroleuca, as the consequence of the dense macroalgal epiphytes colonising their surface. Our results suggest that replacement of L. hyperborea by L. ochroleuca in the NE Atlantic, due to increased dominance or further range expansion of this warm-temperate species, might lead to reduced rates of net productivity driven by increased lamina respiration and reduced photosynthetic capacity of stipes. Net productivity rate of the invasive kelp U. pinnatifida, at saturating light levels (294 µmol O2 g−1 DW h−1), was three times higher than any kelp species ever incubated in situ, helping to explain its high success as an invader. Shifts in the distributions and relative abundances of seemingly similar foundation species may thus lead to subsequent changes in net metabolic balance.
Presentation Slides – Dominique Davoult
Biography:
Professor at Sorbonne Université, working on the ecology of macroalgae-dominated temperate reefs in Roscoff, Brittany. Mainly involved in benthic community functioning through in situ experiments and metabolic measurements, both in the intertidal and the shallow subtidal.
