Mechanisms of inorganic carbon acquisition in two estuarine Rhodophyceans: Bostrychia scorpioides (Hudson) ex Kützing Montagne and Catenella caespitosa (Withering) L. M. Irvine

Abstract

Marine macroalgae possess a range of mechanisms to increase the availability of CO2 for fixation by ribulose-1,5-bisphosphate carboxylase/oxygenase. Of these, possession of a periplasmic or external carbonic anhydrase and the ability to use bicarbonate ions is widely distributed. The mechanisms of carbon acquisition were studied in two estuarine red macroalgae Bostrychia scorpioides and Catenella caespitosa using a range of techniques. pH-drift and CO2-depletion experiments at constant pH suggested that CO2 is the main source of inorganic carbon in both species. Inhibitors indicated that internal and external carbonic anhydrase were present in both species. Inhibitors also suggested that uptake of bicarbonate is unlikely to be present (P < 0.05).

Carbon assimilation in upper subtidal macroalgae is determined by an inverse correlation between Rubisco carboxylation efficiency and CO2 concentrating mechanism effectiveness

“…k cat c and semisaturation constant for CO 2 ( K c ) have only been assessed in very few macroalgal species (Whitney et al ., 2001; Iñiguez et al ., 2019), whereas to date, no data are available for the Rubisco O 2 affinity or the specificity factor ( S c/o ) for ochrophyte macroalgae (Iñiguez et al ., 2020). Rubisco kinetics in macroalgae are possibly related to the effectiveness of their CCMs, as indirect physiological evidence of these mechanisms has been reported in macroalgae (Koch et al ., 2013; Ruiz‐Nieto et al ., 2014; Rautenberger et al ., 2015; Stepien, 2015; Iñiguez et al ., 2016a,b). In this sense, high CO 2 conditions provided by CCMs could overcome the selection for higher carboxylation catalytic efficiency in macroalgae, as found in C 4 plants (Kapralov et al ., 2011; Whitney et al ., 2011; Sharwood et al ., 2016), marine microalgae (Young et al ., 2016; Heureux et al ., 2017), freshwater algae (Goudet et al ., 2020), and seagrasses (Capó‐Bauçà et al ., 2022).…”

Differential Nutrient Uptake by Saltmarsh Plants Is Modified by Increasing Salinity

“…A progressive salinization has also been observed (Clavero et al, 1999 ; Rubio et al, 2003 ; Sánchez de Pedro et al, 2016 ), following the trend of other Mediterranean coastal wetlands, as mentioned above. This coastal ecosystem has been intensively studied, in relation to the impacts of environmental changes and human activities on nutrient cycles and ecophysiology of the different macrophytes inhabiting them (Pérez-Lloréns and Niell, 1990 ; Clavero et al, 1997 , 1999 , 2000 ; Hernández et al, 1997 ; Palomo et al, 2004 ; Niell et al, 2005 ; Palomo and Niell, 2009 ; Ruiz-Nieto et al, 2014 ; Sánchez de Pedro et al, 2016 ). In this salt marsh, the dominant plant species belong to the genera Sarcocornia, Atriplex , and Arthrocnemum , occurring in distinct zones of the salt marsh, following an elevation gradient (Palomo and Niell, 2009 ).…”

Analysis of the Mycosporine-Like Amino Acid (MAA) Pattern of the Salt Marsh Red Alga Bostrychia scorpioides

“…Bostrychia scorpioides (Hudson) Montagne ex Kützing is one of the most common red macroalgae growing in coastal salt marshes in Europe [1], and the only one found in Europe of approximately 40 Bostrychia species that are known globally [2]. It occurs on rocks, mud, and wood structures and partially as tufts on halophytes such as Halimione portulacoides in the upper and middle intertidal zones [3].…”

“…It occurs on rocks, mud, and wood structures and partially as tufts on halophytes such as Halimione portulacoides in the upper and middle intertidal zones [3]. It can survive for a long period when exposed to air [1,4] by experiencing severe osmotic and desiccation stress. This taxon has been reported to produce different metabolites in comparison to other Rhodophyta, such as polyols, d-sorbitol, and d-dulcitol instead of the most common heterosides floridoside or digeneaside [5].…”