Photosynthetic Characteristics of Three Cohabitated Macroalgae in the Daya Bay, and Their Responses to Temperature Rises.

Xiaohan Shi,Zengling Ma,Shanshan Hu,Guangming Mai,Gang Li,Dinghui Zou

doi:10.3390/plants10112441

Abstract

Biochemical compositions and photosynthetic characteristics of three naturally cohabitated macroalgae, Ulva fasciata, Sargassum hemiphyllum and Grateloupia livida, were comparably explored in the field conditions in Daya Bay, northern South China Sea, as well as their responses to temperature rise. Chlorophyll a (Chl a) and carotenoids contents of U. fasciata were 1.00 ± 0.15 and 0.57 ± 0.08 mg g−1 in fresh weight (FW), being about one- and two-fold higher than that of S. hemiphyllum and G. livida; and the carbohydrate content was 20.3 ± 0.07 mg g−1 FW, being about three- and one-fold higher, respectively. Throughout the day, the maximal photochemical quantum yield (FV/FM) of Photosystem II (PS II) of these three macroalgae species decreased from morning to noon, then increased to dusk and kept steady at nighttime. Consistently, the rapid light curve-derived light utilization efficiency (α) and maximum relative electron transfer rate (rETRmax) were lower at noon than that at morning- or night-time. The FV/FM of U. fasciata (varying from 0.78 to 0.32) was 38% higher than that of G. livida throughout the day, and that of S. hemiphyllum was intermediate. The superoxide dismutase (SOD) and catalase (CAT) activities in U. fasciata were lower than that in S. hemiphyllum and G. livida. Moreover, the rises in temperature species-specifically mediated the damage (k) caused by stressful high light and the corresponding repair (r) to photosynthetic apparatus, making the r/k ratio increase with the rising temperature in U. fasciata, unchanged in S. hemiphyllum but decreased in G. livida. Our results indicate that U. fasciata may compete with S. hemiphyllum or G. livida and dominate the macroalgae community under aggravatedly warming future in the Daya Bay.

Highlights

IntroductionMarine macroalgae, including Chlorophyta, Rhodophyta and Phaeophyta, are commonly found in the worldwide coastal regions
The macroalgae distribution, growth and productivity are generally mediated by a complex of environmental factors, among which the temperature is important [10,11] because varying temperatures can alter macroalgae enzymes activity, 4.0/)
In this study we aimed to characterize (i) photosynthetic characteristics of naturally cohabitated macroalgae, Ulva fasciata (Chlorophyta), Sargassum hemiphyllum (Phaeophyta) and Grateloupia livida (Rhodophyta), three dominant macroalgae species in the Daya Bay; and clarify (ii) how they respond to temperature rise from a photophysiological viewpoint

Summary

Introduction

Marine macroalgae, including Chlorophyta, Rhodophyta and Phaeophyta, are commonly found in the worldwide coastal regions They are important in marine ecosystems because they can supply high trophic levels via herbivory or detrital food chains [1], contribute for amount of organic carbon burial [2] and remove surplus nutrients from surroundings [3,4]. According to Iñiguez et al [12], higher temperatures can enhance the activities of the key photosynthetic-involved enzymes, e.g., Ribulose-1,5-bisphosphate carboxylase-oxygenase (RubisCO), enhancing the photosynthesis of macroalgae. Such an increased temperature can neutralize the negative effects of other environmental stressors such as high light [13] and UV-B [14] on photosynthesis. Moderate increases in temperature have often been observed to stimulate the growth and productivity of marine macroalgae [10,13]

Objectives

Methods

Results

Conclusion