Investigating the potential impacts of coal ash runoff on the freshwater Seminole ramshorn snail (Planorbella duryi) under laboratory conditions

Investigating the effects of three trace metals on the viability, embryonic development, and locomotor behavior of the Seminole ramshorn snail at environmentally relevant concentrations

Trace metal contamination is a widespread issue due to its many natural and anthropogenic sources and known carcinogenic, teratogenic, and reproductive effects. As previous invertebrate trace metal research has primarily focused on model species (Daphnia magna, Chironomidae, etc.), our understanding of effects on non-model invertebrate species remains relatively poor. As such, this study assessed the exposure effects of cadmium, arsenic, and lead on viability, locomotor behavior, and embryonic development of the Seminole ramshorn snail (Planorbella duryi). Exposure treatments of CdCl2 , Na2 HAsO4 • 7H2 O, or Pb (NO3 )2 were prepared at concentrations of 0, 0.01, 0.1, 1, and 10 mg/L and confirmed using inductively coupled plasma optical emission spectroscopy (ICP-OES). Individual adult P. duryi were exposed for 7 days with viability assessed every 24 h, and locomotor behavior was accessed on Days 1 and 7 using ToxTrac v2.97 automated behavior software. Individual embryos from newly laid (<6 h old) embryonic clutches were exposed for 10 days, during which embryonic development stage was documented every 24 h. Based on our results, an additional follow-up study for cadmium was conducted using a lower range of 0-0.1 mg/L to allow for the observation of sublethal endpoints. Adult lead and cadmium exposure resulted in significant mortality in the highest treatments (1 and 10 mg/L), dose-dependent behavioral effects, and delayed embryonic development. Arsenic exposures resulted in little to no impacts for all assessed endpoints. Our results provide new insight into the sublethal impacts of these contaminants and highlight potential for behavior and embryonic development as useful tools for risk assessment. PRACTITIONER POINTS: The exposure effects of lead, cadmium, and arsenic on the viability, embryonic development, and locomotor behavior of a common freshwater snail species was investigated using environmentally relevant concentrations. The severity of impact differed for each trace metal, with cadmium being the most toxic and arsenic the least toxic at concentrations ranging from 0 to 10 mg/L. Embryonic development appeared to be the most sensitive endpoint of those tested in this study, suggesting that exposure may have prolonged effects that extend to population and community levels. The Seminole ramshorn snail serves as a sensitive alternative model species that can be used to assess the impacts of contaminants on freshwater invertebrates in future studies.

Assessing the presence, concentration, and impacts of trace element contamination in a Chesapeake Bay tributary adjacent to a coal ash landfill (Possum Point, VA)

Coal ash (CA) is an industrial waste product that has been shown to contain several neurotoxic constituents such as cadmium, selenium, mercury, lead, and arsenic. Contaminant-laced leachates enter the environment via seepage, runoff, permitted discharge, or accidental spills from CA storage ponds or landfills which may pose a risk to wildlife residing in receiving waterways. In this study, we assessed 1) the presence and concentration of thirteen trace elements (Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, Fe, B) in surface water and sediment grab samples using ICP-OES, 2) the temporal variability of trace elements using Pb-210 dated sediment core samples, 3) differences in species diversity using environmental DNA (eDNA) analyses, and 4) the presence and concentration of trace metals in banded killifish (Fundulus diaphanus) epaxial muscle tissue collected from waterways surrounding the Possum Point Power Station (Stafford, VA). Results showed the highest concentrations of As, Cd, Cr, Cu, Fe, Mg, Se, Zn, and B in Quantico Creek (QC) adjacent to the coal ash ponds and elevated average cadmium and zinc concentrations compared to both upstream and downstream locations along the Potomac River. Sediment core profiles and Pb-210 analyses showed historical enrichment of several trace elements in QC beginning after the commissioning of the power plant in 1948. When compared to upstream and downstream sites, species diversity was drastically reduced in Quantico Creek based on eDNA identification. Muscle tissues of banded killifish collected in Quantico Creek displayed increased Al, Cd, and Zn concentrations compared to upstream and downstream sites. Collectively, our results demonstrate the potential impacts of coal ash landfills on aquatic ecosystems and suggest that further research is needed to fully inform risk assessment and remediation efforts.