Ecophysiological responses to elevated CO2 and temperature in Cystoseira tamariscifolia (Phaeophyceae)

Abstract

Ocean acidification increases the amount of dissolved inorganic carbon (DIC) available in seawater which can benefit photosynthesis in those algae that are currently carbon limited. Carbon dioxide emissions are causing fundamental changes in surface ocean carbon chemistry that are expected to boost growth rates in some algae but not others, leading to shifts in the structure and function of seaweed communities. Recent studies show ocean acidification driven shifts in seaweed community dominance depend on interactions with other factors such as light and nutrients. The study of interactive effects of ocean acidification and warming can help elucidate the likely effects of climate change on marine primary producers. In this study, we investigated the ecophysiological responses in a brown macroalgae species Cystoseira tamariscifolia (Hudson) Papenfuss with important structural role in the coastal Mediterranean communities. Algae were collected in oligotrophic vs ultra-oligotrophic waters in the Mediterranean Sea and they were incubated in tanks at ambient (ca. 400-500 ppm) and high CO2 (ca. 1200-1300 ppm), and at two testing temperatures at 20ºC (ambient temperature) and 24ºC (ambient temperature + 4ºC). Increased CO2 levels benefited the algae from both origins. Biomass increased in elevated CO2 treatments and was similar in algae from both origins. The maximal electron transport rate (ETRmax), used to estimate photosynthetic capacity, increased in ambient temperature/high CO2 treatments. The highest polyphenol content and antioxidant activity were observed in ambient temperature/high CO2 conditions in algae from both origins being the phenol content higher in algae from ultra-oligotrophic waters (1.5-3.0 %) than that from oligotrophic waters (1.0-2.2 %). Our study shows that ongoing ocean acidification can be expected to increase algal productivity (ETRmax), boost antioxidant activity (EC50) and increase production of photoprotective compounds (polyphenols). Cystoseira tamariscifolia collected from oligotrophic and ultra-oligotrophic waters were able to acclimate to increases in DIC with under ambient temperature.

Effects of Ocean Acidification on Marine Photosynthetic Organisms Under the Concurrent Influences of Warming, UV Radiation, and Deoxygenation

“…Studies in areas with naturally high levels of CO 2 show that coastal ecosystems are altered especially if elevated DIC is combined with high levels of nutrients (Celis-Plá et al, 2017;Rastrick et al, 2018). In upwelling areas such as Namibia and Peru, these acidified waters have productive food webs that support major fisheries.…”

Ecological Function of Phenolic Compounds from Mediterranean Fucoid Algae and Seagrasses: An Overview on the Genus Cystoseira sensu lato and Posidonia oceanica (L.) Delile

“…Ocean acidification is expected to increase algal productivity, boost antioxidant activity and increase production of photoprotective compounds [96]. Under elevated pCO 2 conditions an increase in the biomass of C. tamariscifolia has been observed, but only at optimal temperature conditions and also if nutrients were sufficiently available.…”

Depth distribution of canopy‐forming algae of the order Fucales is related to their photosynthetic features

“…Bianchi et al, 2014;Catra et al, 2019;Cormaci & Furnari, 1999;Mariani et al, 2019;Thibaut et al, 2005Thibaut et al, , 2015, their vulnerability to pollution (e.g. Arévalo et al, 2007;Ivesa et al, 2016;Munda, 1993;Pinedo et al, 2013;Sales et al, 2011;Soltan et al, 2001), grazing (Agnetta et al, 2015;Bonaviri et al, 2011;Sala et al, 2011;Vergés et al, 2009Vergés et al, , 2014 or warming (Capdevila et al, 2019;Celis-Plá et al, 2017a), as well as on information about measures to improve their conservation (De la Fuente et al, 2019;Medrano et al, 2020;Verdura et al, 2018), very few studies have been devoted to their photosynthetic features (Celis-Plá et al, 2017b;Coudret & Jupin, 1985;Delgado et al, 1995;Tremblin et al, 1986) and none has addressed the light-related ecophysiological features that explain their bathymetric distribution.…”