The Use of the Marine Microalga Tisochrysis lutea (T-iso) in Standard Toxicity Tests; Comparative Sensitivity With Other Test Species

Tania Tato,Ricardo Beiras

doi:10.3389/fmars.2019.00488

Abstract

The marine flagellate Isochrysis galbana, with a global distribution, is one of the most common microalgae used as natural food in aquaculture. In recent years I. galbana has been also increasingly used in toxicity testing, although it is not included in current international protocols such as ISO that relies on Phaeodactylum tricornutum and Skeletonema costatum as marine species, and Raphidocelis subcapitata as freshwater species. Sensitivity of I. galbana to selected model toxicants was compared with that of those recommended species using the 72h growth-rate inhibition response. Internationally accepted standard methods with fixed test conditions (light intensity, photoperiod, temperature, nutrients concentrations, initial cell density, time of exposure and endpoint) were followed to allow this comparison. Toxicity of model chemicals representative of the main environmental toxicants: a trace metal (zinc), a polyaromatic hydrocarbon (fluoranthene), an herbicide (benzalkonium chloride), an insecticide (chlorpyrifos), a surfactant (4-nonylphenol), and a microbiocide (triclosan) were evaluated to determine EC50 and EC10 values. In general, I. galbana showed higher sensitivity for most groups of toxicants, meeting the acceptability criteria in terms of control growth set in standard protocols. For example EC50 and EC10 of I. galbana for chlorpyrifos were 246 µg L-1 and 132 µg L-1, whereas for P. tricornutum these values were ca. 5-fold higher: 1117 and 746 µg L-1 respectively. Therefore, the use of I. galbana in marine toxicity testing as standard model representative of photosynthetic organisms is recommended.

Highlights

Unicellular planktonic algae are primary producers that support oceanic food webs
The aim of this study was to assess the sensitivity of Tiso in comparison with other microalgal species recommended in standard methods: P. tricornutum and R. subcapitata, using selected model toxicants representative of the main groups of aquatic pollutants
For all the chemicals evaluated, T-iso was more sensitive than P. tricornutum and than R. subcapitata for 4-n-NP and TCS

Summary

Introduction

Unicellular planktonic algae are primary producers that support oceanic food webs. Microalgae are well suited for toxicity bioassays because they are cultured and sensitive to organic and inorganic pollutants (Klaine and Lewis, 1995). Isochrysis galbana, culture strain isolated from Tahiti (hereafter T-iso), recently renamed Tisochrysis lutea (Bendif et al, 2013), has been one of the most used marine microalgae in toxicity tests (MorenoGarrido et al, 2000; Hampel et al, 2001; Yap et al, 2004; Satoh et al, 2005; Campa-Córdova et al, 2006; Correa-Reyes et al, 2007; Garrido-Perez et al, 2008; Debelius et al, 2009; Pérez et al, 2010a; Liu et al, 2011; Fisher et al, 2014; Suratno et al, 2015; Trenfield et al, 2015) This species was selected on the basis of its sensitivity and the ease to culture (Shaw and Chadwick, 1998; Pérez et al, 2009) as well as its economic importance in aquaculture (Renaud et al, 1991). They have a fast growth rate and wide physicochemical tolerance ranges (O’Shea et al, 2008)

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