Environmental contaminant effects on juvenile striped bass in the San Francisco Estuary, California, USA

Abstract

The decline of pelagic organisms in the San Francisco Estuary (SFE) (California, USA) is attributed to several factors, including water diversions, invasive species, and exposure to environmental toxicants. The present study evaluated the effects of environmental contaminants on liver vitellogenin, metallothionein, 7-ethoxyresorufin-O-deethylase (EROD), and benzyloxyresorufin O-deethylase (BROD) activity in juvenile striped bass (Morone saxitilis) in the SFE. Analysis of juvenile striped bass liver extracts revealed site-specific elevations of vitellogenin, metallothionein, and EROD biomarkers across the estuary. Although some striped bass in the estuary showed EROD activity similar to unhandled hatchery controls, several sites in the estuary showed significantly higher EROD activity that was in the range of beta-naphthoflavone (BNF)-injected, positive controls. Overall, EROD activity averaged 283% higher in estuary fish than in hatchery controls. Chemical analyses of extracts from semipermeable membrane devices (SPMDs) deployed in the estuary for one month showed elevated polyaromatic hydrocarbon (PAH) levels. Semipermeable membrane devices extract injections-induced metallothionein and BROD in striped bass livers. These data show that environmental exposures are impacting EROD and other biomarkers in the SFE striped bass population. Previous studies in our laboratory have associated poor larval development with maternal transfer of environmental contaminants. Further studies are needed to monitor contaminant exposures by the use of biomarkers and to integrate them into a more effective pelagic species recovery plan in the SFE.

Cytochrome P4501A mRNA and protein induction in striped bass (Morone saxatilis)

“…Liver microsomal 7 ethoxyresorufin-O-deethylase (EROD) activity is commonly used as a proxy of Cyp1a induction. Although Cyp1a is the main enzyme catalyzing the de-ethylation of ethoxyresorufin, other CYP enzymes also can contribute to EROD activity (Spearow et al 2011). It has also repeatedly been reported that EROD can substantially be inhibited by elevated levels of PCBs, fluoranthene (a prevalent PAH), dioxins and heavy metals (e.g., Viarengo et al 1997;Gooch et al 1989;Willett et al 2001;Ortiz-Delgado et al 2008).…”

“…It has also repeatedly been reported that EROD can substantially be inhibited by elevated levels of PCBs, fluoranthene (a prevalent PAH), dioxins and heavy metals (e.g., Viarengo et al 1997;Gooch et al 1989;Willett et al 2001;Ortiz-Delgado et al 2008). EROD activity is technically easy to measure, and it is still considered as a robust biomarker (Oris and Roberts 2007); however, this enzymatic activity biomarker shows some limitations that can make interpretation sometimes difficult in field studies (Spearow et al 2011). Although several studies have focused separately on Cyp1a induction at different organizational levels such as gene expression (e.g.…”

“…Current monitoring efforts in the San Francisco Estuary have highlighted the presence of a number of contaminants, including PAHs and PHAHs (SFEI 2008). The newly developed Cyp1a ELISA described here, along with knowledge-based applications of numerous other molecular and biochemical biomarkers (Burge et al 2004;Geist et al 2007;Picha et al 2008;Washburn et al 1996;Durieux et al 2011;Spearow et al 2011) will permit the assessment and understanding of the sublethal effects of complex mixture of chemical contaminants on striped bass. In addition, as an apex predator, striped bass is a sentinel species in this threatened ecosystem such that the approach developed and described here can be an extremely useful and effective mean of assessing, understanding and potentially mitigating sublethal contamination in estuarine habitats where striped bass reside.…”

“…The results confirmed that the antigenic Cyp1a protein fragment was present. The competitive Cyp1a ELISA described above was shown to be optimized by coating plates overnight with 200 ng ml -1 Cyp1a at 4°C, co-incubating S9 fraction sample with 1/10,000 dilution of mouse anti-fish Cyp1a in the competitive binding step, and incubating with 1/10,000 dilution of goat anti-mouse HRP (Ostrach et al 2009;Spearow et al 2011). S9 fraction sample was prepared; powdered liver tissues of each sample were homogenized in 10 volumes by weight of ice-cold extraction buffer consisting 0.02 M 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES) 0.15 M KCl, (pH 7.5) 0.22 mM 4-(2-aminoethyl) benzenesulfonyl fluoride and 1/200 protease inhibitor cocktail (Sigma).…”

Life Histories, Salinity Zones, and Sublethal Contributions of Contaminants to Pelagic Fish Declines Illustrated with a Case Study of San Francisco Estuary, California, USA

“…Organisms can also acclimate to chronic contaminant exposure via compensatory processes. For example, many fish, including striped bass, can detoxify metals through greater production of the metalbinding protein metallothionein (Geist et al 2007;Spearow et al 2011). Because contaminants are agents of natural selection, over multiple generations some organisms develop heritable resistance to aromatic contaminants such as polychlorinated biphenols (PCBs; electronic coolants), polycyclic aromatic hydrocarbons (PAHs; by-products of combustion) (Wirgin and Waldman 2004;Yuan et al 2006;Wirgin et al 2011), pesticides (Relyea and Hoverman 2006), and metals Guinand et al 2010).…”