Evaluation of the Effect of Local Water Chemistry on Trace Metal Accumulation in Puget Sound Shellfish Shows That Concentration Varies With Species, Size, and Location

Eileen H Bates,Michael Maher,Paul Mcelhany,Alexander Gagnon,Tamas Ugrai,Jacqueline L Padilla-Gamiño,Lindsay Alma

doi:10.3389/fmars.2021.636170

Abstract

Global climate change is causing ocean acidification (OA), warming, and decreased dissolved oxygen (DO) in coastal areas, which can cause physiological stress and compromise the health of marine organisms. While there is increased focus on how these stressors will affect marine species, there is little known regarding how changes in water chemistry will impact the bioaccumulation of trace metals. This study compared trace metal concentrations in tissue of Mediterranean mussels (Mytilus galloprovincialis) and Olympia oysters (Ostrea lurida) in Puget Sound, Washington, a region that experiences naturally low pH, seasonal hypoxia, and is surrounded by urbanized and industrialized areas. Shellfish were held at three sites (Carr Inlet, Point Wells, and Dabob Bay) where oceanographic data was continuously collected using mooring buoys. Using inductively coupled plasma mass-spectrometry (ICP-MS) to measure trace metals in the tissue, we found differences in accumulation of trace metals based on species, location, and shellfish size. Our study found differences between sites in both the mean metal concentrations and variability around the mean of those concentrations in bivalves. However, high metal concentrations in bivalves were not associated with high concentrations of metals in seawater. Metal concentrations in shellfish were associated with size: smaller shellfish had higher concentrations of metals. Carr Inlet at 20 m depth had the smallest shellfish and the highest metal concentrations. While we could not eliminate possible confounding factors, we also found higher metal concentrations in shellfish associated with lower pH, lower temperature, and lower dissolved oxygen (conditions seen at Carr Inlet at 20 m and to a lesser extent at Point Wells at 5 m depth). There were also significant differences in accumulation of metals between oysters and mussels, most notably copper and zinc, which were found in higher concentrations in oysters. These findings increase our understanding of spatial differences in trace metal bioaccumulation in shellfish from Puget Sound. Our results can help inform the Puget Sound aquaculture industry how shellfish may be impacted at different sites as climate change progresses and coastal pollution increases.

Highlights

Climate change poses a global threat, but will impact coastal areas such as marginal seas through both land and marine driven changes in precipitation, runoff, sea level rise, ocean circulation, and seawater chemistry (Scavia et al, 2002; Harley et al, 2006; Pachauri et al, 2014)
This study used experimental data from the field to investigate how effects of temperature, pH, and DO are associated with the accumulation of trace metals in mussels and oysters from Puget Sound
Our results provide evidence that (1) lower pH is associated with higher metal concentrations in shellfish, and (2) depth may have more impact than site on metal bioaccumulation in Puget Sound

Summary

Introduction

Climate change poses a global threat, but will impact coastal areas such as marginal seas through both land and marine driven changes in precipitation, runoff, sea level rise, ocean circulation, and seawater chemistry (Scavia et al, 2002; Harley et al, 2006; Pachauri et al, 2014). Coastal cities and areas with high river discharge will face the threat of increased pollution (Fowler and Oregioni, 1976; Wang et al, 2018), which may have important consequences for bioaccumulation of metals and chemicals in marine organisms, further impacting their physiology and survival In marginal seas such as Puget Sound, research has been conducted on the variation of pH, temperature, and DO in coastal zones and how these oceanographic variables may interact to affect physiological performance, reproduction, and survival of species (Handisyde et al, 2006; Washington Sea Grant, 2015; Gobler and Baumann, 2016). These limitations emphasize the importance of collecting empirical data in furthering our understanding of how trace metal accumulation will vary in space and time as temperature and pCO2 increase due to anthropogenic effects

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