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Toxic effects of Heterosigma akashiw o do not appear to be mediated by hydrogen peroxide
Author(s) -
Twiner Michael J.,
Dixon S. Jeffrey,
Trick Charles G.
Publication year - 2001
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2001.46.6.1400
Subject(s) - heterosigma akashiwo , hydrogen peroxide , artemia salina , brine shrimp , red tide , biology , reactive oxygen species , chemistry , algal bloom , biochemistry , ecology , toxicity , phytoplankton , organic chemistry , nutrient
The ichthyotoxic red tide organism Heterosigma akashiwo (Raphidophyceae) has been associated with fish kill events within the aquaculture industry for many years. The precise toxicological mechanism involved in these fish kills is unclear; however, much research attention has focused on the production of reactive oxygen species (ROS) by these toxic algae. In this study, we investigated the production of hydrogen peroxide (H 2 O 2 ) by isolates of H. akashiwo and the nontoxic chlorophyte Tetraselmis apiculata . Subsequently, we tested those concentrations of H2O2 on vertebrate cell lines and the invertebrate Artemia salina (brine shrimp) to investigate mortality. Net production rates for the H. akashiwo isolates ranged from 0.46 to 7.89 pmol H 2 O 2 min −1 (10 4 cells) −1 while obtaining maximum concentrations between 0.14 and 0.91 µM H 2 O 2 . Conversely, T. apiculata produced only 0.03 pmol H 2 O 2 min ±1 (10 4 cells with a maximum level on 0.04 µM. However, toxic effects on UMRߚ106 and HEKߚ293 cells were only induced by acute and protracted exposure to concentrations of H 2 O 2 >= 0.1 mM. Additionally, significant mortality of A. salina in the presence or absence of ferric and ferrous iron was induced by H 2 O 2 levels >= 1 mM. Iron is a redox metal that reduces H 2 O 2 to hydroxy radicals. These data collectively indicate that production of H 2 O 2 by multiple isolates of H. akashiwo is orders of magnitude less than that required for mortality of either the vertebrate cell lines or the invertebrate A. salina . Other nonichthyotoxic roles for extracellular ROS are proposed.