Photo‐enhanced toxicity of fluoranthene to Gulf of Mexico marine organisms at different larval ages and ultraviolet light intensities

Abstract

Significant increases in toxicity have been observed as a result of polycyclic aromatic hydrocarbon (PAH) absorption of ultraviolet (UV) radiation in aquatic organisms. Early life stage aquatic organisms are predicted to be more susceptible to PAH photo-enhanced toxicity as a result of their translucence and tendency to inhabit shallow littoral or surface waters. The objective of the present study was to evaluate the sensitivity of varying ages of larval mysid shrimp (Americamysis bahia), inland silverside (Menidia beryllina), sheepshead minnow (Cyprinodon variegatus), and Gulf killifish (Fundulus grandis) to photo-enhanced toxicity and to examine the correlation between photo-enhanced toxicity and organism pigmentation. Organisms were exposed to fluoranthene and artificial UV light at different larval ages and results were compared using median lethal concentrations (LC50s) and the lethal time-to-death (LT50s). In addition, a high UV light intensity, short-duration (4-h) experiment was conducted at approximately 24 W/m(2) of ultraviolet radiation A (UV-A) and compared with a low-intensity, long-duration (12-h) experiment at approximately 8 W/m(2) of UV-A. The results indicated decreased toxicity with increasing age for all larval organisms. The amount of organism pigmentation was correlated with observed LC50 and LT50 values. High-intensity short-duration exposure resulted in greater toxicity than low-intensity long-duration UV treatments for mysid shrimp, inland silverside, and sheepshead minnow. Data from these experiments suggest that toxicity is dependent on age, pigmentation, UV light intensity, and fluoranthene concentration.

Evaluation of the phototoxicity of unsubstituted and alkylated polycyclic aromatic hydrocarbons to mysid shrimp (Americamysis bahia): Validation of predictive models

“…Narcotic LC50s were beyond water solubility for benzo[a] pyrene, chrysene, dimethyl-phenanthrene, benz[a]anthrene, dibenz[ah]anthracene, and anthracene (Table 1). Narcotic and phototoxic LC50 values for fluoranthene were obtained from previous studies conducted under the same laboratory and UV light conditions [9]. However, dimethyl-anthracene was considered phototoxic because of the absence of toxicity in UV-filtered control (highest PAH concentration of 5 dilution series placed under UV-filtering Plexiglas), while the same concentration in the highest PAH treatment that was exposed to UV light resulted in 100% mortality in <1 h. Furthermore, LT50s were obtained for dimethyl-anthracene in <1 h, suggesting a highly phototoxic compound (Supplemental Data, Table S3).…”

“…Mysid shrimp (3 d old) were exposed to a series of PAHs including benzo[a]pyrene (Sigma-Aldrich; >96% pure), benz-[a]anthracene (Sigma-Aldrich; 99% pure), dibenz[a,h]anthracene (Sigma-Aldrich; 99% pure), fluorene (Sigma-Aldrich; 98% pure), chrysene (Sigma-Aldrich; 98% pure), naphthalene (Sigma-Aldrich; 98% pure), dibenzothiophene (Sigma-Aldrich; 98% pure), fluoranthene (data obtained from Finch and Stubblefield [9]), phenanthrene (Sigma-Aldrich; 98% pure), 3-methyl-phenanthrene (Fisher Scientific; >98% pure), 3, 6-dimethyl-phenanthrene (Fisher Scientific; >95% pure), anthracene (Sigma-Aldrich; >98% pure), 2-methyl-anthracene (Fisher Scientific; 97% pure), 2,3-dimethyl-anthracene (Fisher Scientific; >98% pure), pyrene (Sigma-Aldrich; >98% pure), and 1-methyl-pyrene (Fisher Scientific; >94% pure). Polycyclic aromatic hydrocarbons were chosen based on commercial availability, prevalence in the environment, and/or lack of empirical data.…”

“…Photo-enhanced toxicity of various unsubstituted (parent) and alkylated polycyclic aromatic hydrocarbons exposed to 3- a Compounds were designated as phototoxic if a 2-fold difference between narcotic and ultraviolet light exposure studies were observed. d Data obtained from Finch and Stubblefield [9]. If a compound was phototoxic, it was designated as "Yes" and nonphototoxic compounds are designated as "No."…”

“…Most notably, atmospheric and hydrospheric conditions can drastically reduce ultraviolet (UV) light transmittance in aquatic environments [6,7]. Organisms regularly exposed to UV light generally develop protective mechanisms against UV light exposure, but studies have shown that those protective mechanisms progressively develop with age [9,10]. Organisms regularly exposed to UV light generally develop protective mechanisms against UV light exposure, but studies have shown that those protective mechanisms progressively develop with age [9,10].…”

“…However, few studies have examined how photo-enhanced toxicity changes with different degrees of alkylation. The mysid shrimp was selected as a model organism as a result of its transparency, low pigmentation, and sensitivity [9]. In some crude oils, PAHs are predominantly alkylated [23,24] but are currently considered equivalent in toxicity to unsubstituted PAHs in models and environmental regulation.…”