Creosote Toxicity to Photosynthesis and Plant Growth in Aquatic Microcosms

Abstract

To assess photosynthesis as a bioindicator of toxicity from polycyclic aromatic hydrocarbons (PAHs), the response of chlorophyll-a fluorescence to creosote exposure was compared with effects on population-level plant growth. Large, outdoor, freshwater microcosms containing Eurasian watermilfoil (Myriophyllum spicatum) received either a single application or multiple applications of liquid creosote at nominal concentrations from 0.109 to 32.7 mg L(-1). For several weeks following treatment, photosynthetic electron transport was measured using pulse amplitude-modulated chlorophyll-a fluorescence. The maximum efficiency of photosystem II electron transport (Fv/Fm) and the quantum yield of photochemistry (deltaF/F'm) were diminished in plants shortly after the addition of creosote. In microcosms that received a single treatment of creosote only, the 50% effective concentrations (EC50s), expressed as the aqueous concentration of 15 of the most abundant PAHs, were 0.28 mg L(-1) for Fv/Fm and 0.30 mg L(-1) for deltaF/F'm. Chlorophyll-a fluorescence was diminished to a greater extent in microcosms that received multiple treatments of creosote, with EC50s of 0.13 mg L(-1) for Fv/Fm and 0.10 mg L(-1) for deltaF/F'm. Plant biomass accumulation was inhibited in a concentration-dependent manner in all microcosms treated with creosote, but this inhibition occurred to a greater degree in microcosms treated with multiple creosote applications. The response of chlorophyll-a fluorescence, measured only 8 d after creosote treatment, was similar to plant growth over the entire growing season, indicating that this technique can be used to estimate potential effects of contaminants before detrimental impacts on populations.

Biomarkers in Aquatic Plants: Selection and Utility

“…Measurements of chlorophyll fluorescence are now widely used for studying plant photosynthesis and stress response (Force et al 2003 ;Frankart et al 2003 ;Marwood et al 2001Marwood et al , 2003Oxborough 2004 ;Roger and Weiss 2001 ;Strasser et al 2000) . Chlorophyll fluorescence will change in response to chemical contaminant exposure and abiotic stress (drought, suboptimal temperatures and nutrient deficiency) (Chesworth et al 2004 ;Christensen et al 2003 ;Deltoro et al 1999 ;Kellomäki and Wang 1999 ;Mahan et al 1995 ;Sayed 2003) .…”

“…Lipophilic compounds (e.g., PAHs, creosote, anthracene and the hydrophobic components of wastewater) have been shown to affect fluorescence parameters in aquatic plants and algae at earlier times, or at comparable or lower concentrations, than those affecting growth (Gensemer et al 1999 ;Juneau et al 2003 ;Marwood et al 2001Marwood et al , 2003 . Heavy metals including Cr, Cu, Cd and Zn, have also shown effects on chlorophyll fluorescence; only Cr, however, shows such effects at concentrations lower than those affecting growth (Appenroth et al 2001 ;Drinovec et al 2004) .…”

Protecting non-target plant species; suggested improvements to current pesticide registration guidelines

“…herbicides, heavy metals, air pollutants, etc.) (Smillie and Hetherington, 1983;Krugh and Miles, 1996;Juneau and Popovic, 1999;Franzaring et al, 2001;Korres et al, 2003;Marwood et al, 2003).…”