Variable photo-physiological performance of macroalgae and seagrasses from Saya de Malha and Nazareth Banks, Mascarene Plateau

Abstract

The photosynthetic performance of macroalgae and seagrasses related to their body parts, depth and colours from the poorly-studied Saya de Malha and Nazareth Banks on the Mascarene Plateau was investigated in this study. Two seagrass (Thalassodendron ciliatum and Halophila decipiens) and seven macroalgae species (Caulerpa cupressoides, Acrosorium ciliolatum, Dictyosphaeria cavernosa, Halimeda opuntia, Ulva sp., Udotea orientalis and Udotea palmetta) were collected using the five Van Veen grabs attached to the Video-Assisted Multi-Sampler (VAMS) from 29-79 m depths in May during the FAO EAF-Nansen Research Programme 2018. The photosynthetic performance was measured using a Diving-Pulse-Amplitude-Modulated (D-PAM) fluorometer and the parameters included effective quantum yield at photosystem II (PSII) (ΦPSII), relative maximum electron transport rate (rETRm), photosynthetic efficiency (α), photoinhibition (β), saturating light level (Ek), and maximum non-photochemical quenching (NPQmax). All photo-physiological parameters varied significantly in T. ciliatum and C. cupressoides across their body parts. However, variation with seawater depths was not significant for NPQmax and β in the seagrass, and ΦPSII, rETRm and β in the macroalgae. Photo-physiological functioning of the leaf of T. ciliatum was optimal at 40 m. The photosynthetic performance of the frond and stolon of C. cupressoides decreased and remained unchanged, respectively, at 79 m when compared to that at 29 m. The whitish lobes of H. opuntia at 31 m exhibited significantly lower photosynthetic performance, in terms of ΦPSII, rETRm,α and Ek, than the greenish lobes. These findings provide a first insight of seaplant body parts-, depth- and colour-related photo-physiological performance from the Mascarene Plateau.

Diplosoma simile (Ascidiacea: Didemnidae) distribution and its photosynthetic thermal stress responses from Mauritius: Implications for invasive or opportunistic behavior

“…Moreover, the urgency of in-depth studies on ascidian-related threats is even more pressing given that ascidian-induced-bioinvasion has been increasingly reported worldwide, especially following mass thermalinduced coral bleaching (Dijkstra et al 2007;Tebbett et al 2019). It is noteworthy that several local studies on photophysiological responses to thermal and other stressors have been conducted on scleractinian corals (Mattan-Moorgawa et al 2015Kaullysing et al 2016;Louis et al 2020;Bhagooli et al 2021b), seaweeds (Narain et al 2023;Bhagooli et al 2021c) and seagrasses (Bhagooli et al 2021c), microalgae (Sadally et al 2016;Soondur et al 2021Soondur et al , 2022 ascidians thermal stress responses are yet to be investigated.…”

Variations in photo-physiological responses of shaded and non-shaded mangrove, Rhizophora mucronata tree parts from Mauritius Island, western Indian Ocean

“…It is noteworthy that plant parts in other marine seaplants have been studied. For instance, the photosynthetic performance was found to be variable among the leaf, transition part between leaf and stem (transit), the stem of the seagrass Thalassodendron ciliatum, and between the frond and the stolon of the macroalga Caulerpa cupressoides (Bhagooli et al 2021a).…”

Antioxidant and photo-physiological acclimatisation in tropical macroalgae at sites with distinct nutrient levels

“…(Cossu et al 1997;Gopeechund et al 2020). However, studies on macroalgae and seagrass antioxidants (Somanah et al 2012;Ramah et al 2014;Narrain et al 2023) and photophysiology (Bhagooli et al 2021a;Narrain et al 2023) are limited in the Mauritian waters.…”