Abstract
Ocean acidification is occurring globally through increasing CO 2 absorption into the oceans creating particular concern for calcifying species. In addition to ocean acidification, near shore marine habitats are exposed to the deleterious effects of runoff from acid sulfate soils which also decreases environmental pH. This coastal acidification is being exacerbated by climate change‐driven sea‐level rise and catchment‐driven flooding. In response to reduction in habitat pH by ocean and coastal acidification, mollusks are predicted to produce thinner shells of lower structural integrity and reduced mechanical properties threatening mollusk aquaculture. Here, we present the first study to examine oyster biomineralization under acid sulfate soil acidification in a region where growth of commercial bivalve species has declined in recent decades. Examination of the crystallography of the shells of the Sydney rock oyster, Saccostrea glomerata, by electron back scatter diffraction analyses revealed that the signal of environmental acidification is evident in the structure of the biomineral. Saccostrea glomerata, shows phenotypic plasticity, as evident in the disruption of crystallographic control over biomineralization in populations living in coastal acidification sites. Our results indicate that reduced sizes of these oysters for commercial sale may be due to the limited capacity of oysters to biomineralize under acidification conditions. As the impact of this catchment source acidification will continue to be exacerbated by climate change with likely effects on coastal aquaculture in many places across the globe, management strategies will be required to maintain the sustainable culture of these key resources.
Highlights
We investigated the impact of this form of coastal acidification on oyster biomineralization in the Sydney rock oyster, Saccostrea glomerata, in a region where the growth of this species has been in decline over recent decades
Coastal acidification is a widespread concern for coastal aquaculture (Dent & Pons, 1995; Dove & Sammut, 2007b; O’Connor & Dove, 2009; Sonnenholzner & Boyd, 2000) yet there are few studies on the impacts of this form of decreased pH on the growth of the shells and skeletons of cultured species and almost no consideration of how this stressor will interact with climate change impacts
We show that a commercially important oyster, the Sydney rock oyster, S. glomerata, shows phenotypic plasticity in response to coastal acidification driven by acid sulfate soil outflows
Summary
We investigated oysters in two subtropical estuary systems that are major oyster farming areas, Wallis Lake and Port Stephens located in the mid-north coast of New South Wales (NSW; Figure 2). The shells of the Sydney rock oysters from the “control” site at Cockatoo Island are comprised of calcite prisms and chalk that produced good quality EBSP (MAD < 1) during EBSD data acquisition (Figure 3). In comparison the shells of the Sydney rock oysters grown under coastal acidification in Wallis Lake at “acidified site 1” appear disordered throughout the outer prismatic layer The shells of the Sydney rock oysters grown at “acidified site 2” in Port Stephens show similarities in the chalky layer crystallographic growth compared to oysters grown in “control” conditions at Cockatoo Island (Figures 3 and 6). There was no visual increase in sulfur levels in oyster shells grown at acidified sites 1 or 2, Representative SEM-EDS sulfur maps of the shells are provided in the Supporting Informations (Supporting Information Figure S1)
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