Environmental factors\xa0controlling the distributions of Botryococcus braunii (A, B and L) biomarkers in a subtropical freshwater wetland

Ding He,Bernd R T Simoneit,Rudolf Jaffé

doi:10.1038/s41598-018-26900-9

Ding He, Bernd R T Simoneit + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-26900-9

Copy DOI

Abstract

Here we report the molecular biomarker co-occurrence of three different races of Botryococcus braunii (B. braunii) in the freshwater wetland ecosystem of the Florida Everglades, USA. Thespecific biomarkers include C32–C34 botryococcenes for race B, C27–C32n-alkadienes and n-alkatrienes for race A, and lycopadiene for race L. The n-alkadienes and n-alkatrienes were present up to 3.1 and 69.5 µg/g dry weight (dw), while lycopadiene was detected in lower amounts up to 3.0 and 1.5 µg/g dw in periphyton and floc samples, respectively. Nutrient concentrations (P and N) did not significantly correlate with the abundances of these compounds. In contrast, n-alkadienes and n-alkatrienes were present in wider diversity and higher abundance in the floc from slough (deeper water and longer hydroperiod) than ridge (shallower water and shorter hydroperiod) locations. n-Alkadienes, n-alkatrienes, and lycopadiene, showed lower δ13C values from −40.0 to −35.5‰, suggesting that the source organisms B. braunii at least partially utilize recycled CO2 (13C depleted) produced from OM respiration rather than atmospheric CO2 (13C enriched) as the major carbon sources.

Highlights

Than ridge locations. n-Alkadienes, n-alkatrienes, and lycopadiene, showed lower δ13C values from −40.0 to −35.5‰, suggesting that the source organisms B. braunii at least partially utilize recycled CO2 (13C depleted) produced from OM respiration rather than atmospheric CO2 (13C enriched) as the major carbon sources
Gas chromatography-mass spectrometry (GC-MS) analysis of the n-hexane eluted fraction from various periphyton and floc sample extracts showed the presence of n-alkadienes, n-alkatrienes and one lycopadiene (Fig. 2; Table 2)
Lycopadiene has been reported as a specific biomarker for race L of B. braunii[4], while botryococcenes have been suggested to derive from race B of B. braunii in the Everglades18. n-Alkadienes and n-alkatrienes were not detected in floc and surface soil at the mangrove-dominated estuarine locations[27], nor in the leaves or roots of dominant plant species across the Everglades ecosystem22,28. n-Alkadienes and n-alkatrienes have been reported in insect wax lipids, but they usually cover higher carbon chain lengths up to C3929

Summary

Introduction

Than ridge (shallower water and shorter hydroperiod) locations. n-Alkadienes, n-alkatrienes, and lycopadiene, showed lower δ13C values from −40.0 to −35.5‰, suggesting that the source organisms B. braunii at least partially utilize recycled CO2 (13C depleted) produced from OM respiration rather than atmospheric CO2 (13C enriched) as the major carbon sources. Dominated communities, and scattered tree islands dispersed throughout this landscape[12] Within this diverse distribution of plant species, periphyton mats, composed of abundant calcareous mixtures of diatoms, cyanobacteria and green algae, are distributed widely throughout this ecosystem[13,14]. B. braunii is distributed widely in aquatic ecosystems, especially in tropical oligotrophic freshwater to brackish lakes[16], the microfossils of Botryococcus have only been reported in soil cores of tree islands in the Everglades[17]. We report the molecular characterization of various tracers of three races of B. braunii including botryococcenes, long chain n-alkadienes, n-alkatrienes, and lycopadiene in environmental samples of the Everglades ecosystem, examine their stable carbon isotopes, and discuss possible controlling factors including nutrients and hydroperiod on their distribution and abundances

Methods

Results

Discussion

Conclusion