Chemical Profiling of Volatile Organic Compounds in the Headspace of Algal Cultures as Early Biomarkers of Algal Pond Crashes

Kristen L Reese,James D Jaryenneh,A Daniel Jones,Carolyn L Fisher,Matthew W Moorman,Matthias Frank,Pamela D Lane,Todd W Lane

doi:10.1038/s41598-019-50125-z

Abstract

Algae ponds used in industrial biomass production are susceptible to pathogen or grazer infestation, resulting in pond crashes with high economic costs. Current methods to monitor and mitigate unhealthy ponds are hindered by a lack of early indicators that precede culture crash. We used solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) to identify volatiles emitted from healthy and rotifer infested cultures of Microchloropsis salina. After 48 hours of algal growth, marine rotifers, Brachionus plicatilis, were added to the algae cultures and volatile organic compounds (VOC) were sampled from the headspace using SPME fibers. A GC-MS approach was used in an untargeted analysis of VOCs, followed by preliminary identification. The addition of B. plicatilis to healthy cultures of M. salina resulted in decreased algal cell numbers, relative to uninfected controls, and generated trans-β-ionone and β-cyclocitral, which were attributed to carotenoid degradation. The abundances of the carotenoid-derived VOCs increased with rotifer consumption of algae. Our results indicate that specific VOCs released by infected algae cultures may be early indicators for impending pond crashes, providing a useful tool to monitor algal biomass production and pond crash prevention.

Highlights

Parasitism[5,6]
A setup based upon solid-phase microextraction (SPME) fibers coupled with gas chromatography-mass spectrometry (GC-MS) allowed for non-invasive monitoring of volatile emissions
Algal cell concentrations and volatile organic compounds (VOC) headspace samples were collected at various time points for M. salina alone, M. salina and B. plicatilis, and ESAW media blanks (Fig. 3, Supplemental Fig. 1)

Summary

Introduction

Parasitism[5,6]. Notably, a single adult marine rotifer, Brachionus plicatilis (Fig. 1B), can consume 200 microalgal cells per minute and double in population within 1–2 days[7]. When applied early and in a targeted fashion after the detection of a deleterious species[16], chemical additives can be highly effective at saving algal cultures [for review of crop protection strategies, see Fisher & Lane 2019]. Compounds present during the active grazing period of rotifers on algal cultures, but not produced in healthy controls, were deemed potential biomarkers of high stress conditions. We propose that these biomarker compounds are potential diagnostic tools for chemical monitoring systems in microalgal cultivation systems to enabling the early detection of culture stress for improved algal crop production

Objectives

Methods

Results

Conclusion