Use of preserved museum fish to evaluate historical and current mercury contamination in fish from two rivers in Oklahoma, USA

Abstract

We examined the effects of a commonly used preservation technique on mercury concentration in fish tissue. After fixing fish muscle tissue in formalin followed by preservation in isopropanol, we found that mercury concentration in fish muscle tissue increased by 18%, reaching an asymptote after 40 days. We used formalin-isopropanol-preserved longear sunfish (Lepomis megalotis) from the Sam Noble Oklahoma Museum of Natural History to examine historical changes and predict current mercury concentrations in fish from two rivers in southeastern Oklahoma. Glover River was free-flowing, while Mountain Fork River was impounded in 1970 and a coldwater trout fishery was established upstream from the collection site in 1989. Mercury concentrations in longear sunfish from Glover River showed no historical changes from 1963 to 2001. Mercury concentrations in longear sunfish from Mountain Fork River showed no change from 1925 to 1993 but declined significantly from 1993 to 2003. We also compared mercury concentrations of the most recently collected longear sunfish in the museum to mercury concentrations of unpreserved fish collected from the rivers in 2006. Concentrations of mercury in museum fish were not significantly different from mercury concentrations in unpreserved fish we collected from the rivers. Our study indicates that preserved museum fish specimens can be used to evaluate historical changes and predict current levels of mercury contamination in fish.

The Influence of Preservation on Fish Morphology in Museum Collections Based on Two Species of the Genus <I>Lepomis</I> (Actinopterygii: Perciformes: Centrarchidae)

“…Examining these collections allows identification or quantification of changes in species composition, biodiversity, biogeographic distributions, accumulation of toxins, and morphology across temporal and spatial scales. These changes can result from both natural and anthropogenic influences including channelization (Lau et al 2006), water pollution (Hill et al 2010), climate change, and modification of land use (Daniels et al 2005). For example, museum specimens have been used to identify the accumulation of mercury in marine and freshwater fishes (Barber et al 1972, Miller et al 1972, Hill et al 2010, the temporal change in Costa Rican fish assemblages (Reznick et al 1994), and how an impoundment may result in the morphological divergence of a fish species (Franssen 2011).…”

Mercury in tropical and subtropical coastal environments

“…Nations benefiting from these economic and social changes need to cooperate on a global scale to evaluate the environmental costs from altered mercury cycling and to find appropriate ways to minimize or mitigate the negative impacts. Records from museum and biological specimen collections (Hill et al, 2010) and sediment cores (Xu et al, 2011) may contribute to the assessment of global and local conditions and their quantitative and qualitative changes over time and space.…”

Can Preserved Museum Specimens Be Used to Reconstruct Fish Mercury Burden and Sources through Time?

“…Since the mid-1800s, scientists have collected and preserved wildlife specimens for taxonomic and systematic purposes. This has made museums critical repositories for representing biological diversity across time and space. − These collections now serve as a unique archive of past environments and are ripe for creative research. ,, Contaminant research could benefit from museum biological collections − and environmental specimen banks − because they offer tissues that represent a wide range of historical and spatial contexts, and access to these tissues is inexpensive compared to launching new field efforts. These costs savings can allow researchers to direct resources toward applying more sophisticated and expensive tools, such as compound-specific stable isotopes or trace contaminant analyses.…”