Combined effects of global climate change and nutrient enrichment on the physiology of three temperate maerl species

• Main Author: Qui Minet, Zujaila Nohemy
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2020
• Subjects: Ocean acidification
• Online Access: https://doi.org/10.5061/dryad.zkh18935j

Made up of calcareous coralline algae, maerl beds play a major role as ecosystem engineers in coastal areas throughout the world. They undergo strong anthropogenic pressures, which may threaten their survival. The aim of this study was to gain insight into the future of maerl beds in the context of global and local changes. We examined the effects of rising temperatures (+3ºC) and ocean acidification (-0.3 pH units) according to temperature and pH projections (i.e. the RCP8.5 scenario), and nutrient (N and P) availability on three temperate maerl species ( Lithothamnion corallioides , Phymatolithon calcareum , Lithophyllum incrustans ) in the laboratory in winter and summer conditions. Physiological rates of primary production, respiration and calcification were measured on all three species in each treatment and season. The physiological response of maerl to global climate change was species-specific and influenced by seawater nutrient concentrations. Future temperature-pH scenario enhanced maximal gross primary production rates in P. calcareum in winter and in L. corallioides in both seasons. Nevertheless, both species suffered an impairment of light harvesting and photo-protective mechanisms in winter. Calcification rates at ambient light intensity were negatively affected by the future temperature-pH scenario in winter, with net dissolution observed in the dark in L. corallioides and P. calcareum under low nutrient concentrations. Nutrient enrichment avoided dissolution under future scenarios in winter and had a positive effect on L. incrustans calcification rate in the dark in summer. In winter conditions maximal calcification rates were enhanced by the future temperature-pH scenario on the three species, but P. calcareum suffered inhibition at high irradiances. In summer conditions, the maximal calcification rate dropped in L. corallioides under the future global climate change scenario , with a potential negative impact on CaCO 3 budget for maerl beds in the Bay of Brest where this species is dominant. ...