An official website of the United States government
How ocean acidification (OA) interacts with other stressors is understudied, particularly for predators and prey. We assessed long-term exposure to decreased pH and low salinity on (1) juvenile blue crab Callinectes sapidus claw pinch force, (2) juvenile hard clam Mercenaria mercenaria survival, growth, and shell structure, and (3) blue crab and hard clam interactions in filmed mesocosm trials. In 2018 and 2019, we held crabs and clams from the Chesapeake Bay, USA, in crossed pH (low: 7.0, high: 8.0) and salinity (low: 15, high: 30) treatments for 11 and 10 wk, respectively. Afterwards, we assessed crab claw pinch force and clam survival, growth, shell structure, and ridge rugosity. Claw pinch force increased with size in both years but weakened in low pH. Clam growth was negative, indicative of shell dissolution, in low pH in both years compared to the control. Growth was also negative in the 2019 high-pH/low-salinity treatment. Clam survival in both years was lowest in the low-pH/low-salinity treatment and highest in the high-pH/high-salinity treatment. Shell damage and ridge rugosity (indicative of deterioration) were intensified under low pH and negatively correlated with clam survival. Overall, clams were more severely affected by both stressors than crabs. In the filmed predator-prey interactions, pH did not substantially alter crab behavior, but crabs spent more time eating and burying in high-salinity treatments and more time moving in low-salinity treatments. Given the complex effects of pH and salinity on blue crabs and hard clams, projections about climate change on predator-prey interactions will be difficult and must consider multiple stressors.
more »
« less
Consequences of Salinity Change, Salinity History, and Shell Morphology on Early Growth of Juvenile Oysters
Estuaries provide valuable habitat for the eastern oyster (Crassostrea virginica). Although salinity at a given location fluctuates regularly with tides, upbay and downbay salinity differences span a broad estuarine salinity gradient. Higher salinity habitats downbay support faster oyster growth, whereas lower salinities upbay act as a refuge from predation and disease but slows growth. Two experiments were performed to investigate the effect of salinity, postsettlement salinity changes, and shell morphology on juvenile oyster growth. One experiment used wild oyster spat collected from three distinct Delaware Bay salinity zones that were then transplanted into various salinity conditions in the laboratory, where growth was monitored. Transplanting into low salinity led to decreased growth compared with transplanting to higher salinity, and growth of oyster spat was overall highest for spat from the lowest salinity source. Growth did not differ among shell morphologies. A second experiment used hatchery reared larvae set in one of four different salinity conditions. Those spat were maintained in settlement salinities 22, 16, 10, and 6 for 2–3 wk postsettlement, then measured before fully factorial transfer into new salinity conditions with measurement 3 wk later. Lower final salinity treatments were associated with lower growth, lower initial salinity treatments were associated with faster final treatment growth, and final growth depended on the interaction between initial and final salinity. Therefore, in addition to the effects of acute salinity changes on growth, early postsettlement hyposalinity stress can generate compensatory juvenile oyster growth. As increased freshwater events due to climate change are expected in the Delaware Bay and regionally in the Northeast, these results indicate that nonlinear early life stress responses are important to quantify to better understand oyster stock resilience and plan management.
more »
« less
- Award ID(s):
- 1756712
- PAR ID:
- 10494725
- Publisher / Repository:
- Journal of Shellfish Research
- Date Published:
- Journal Name:
- Journal of Shellfish Research
- Volume:
- 42
- Issue:
- 1
- ISSN:
- 0730-8000
- Page Range / eLocation ID:
- 21-28
- Subject(s) / Keyword(s):
- Oyster spat morphology salinity growth carryover effects
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Salinity is a major environmental factor that influences the population dynamics of fish and shellfish along coasts and estuaries, yet empirical methods for hindcasting salinity at specific sampling stations are not widely available. The specific aim of this research was to predict the salinity experienced by juvenile and adult oysters (Crassostrea virginica) collected at sampling stations in Delaware Bay. To do so, empirical relationships were created to predict salinity at five oyster bed stations using observing systems data. These relationships were then applied to construct indices of salinity exposure over an oyster’s lifetime. Three independent salinity data sources were used in conjunction with observing systems data to construct and validate the predictive relationships. The root mean square error (RMSE) of the models ranged from 0.5 to 1.6 psu when model predictions were compared with the three independent data sets. Results demonstrated that data from an observing system near the head of Delaware Bay could be used to predict salinity within ± 2 psu at oyster bed stations as far down-estuary as 39 km. When these models were applied to estimate low salinity exposure of 2-year-old oysters via the metric of consecutive days below 5 psu, the indices suggested that there could be as much as a 42-day difference in low salinity exposure for oysters at stations just 31 km apart. The approach of using observing systems data to hindcast salinity could be applied to advance understanding of salt distribution and the effect of low salinity exposure on organisms in other estuaries, especially bottom-associated species.more » « less
-
Background Abundance of the commercially and ecologically important Eastern oyster, Crassostrea virginica , has declined across the US Eastern and Gulf coasts in recent decades, spurring substantial efforts to restore oyster reefs. These efforts are widely constrained by the availability, cost, and suitability of substrates to support oyster settlement and reef establishment. In particular, oyster shell is often the preferred substrate but is relatively scarce and increasingly expensive. Thus, there is a need for alternative oyster restoration materials that are cost-effective, abundant, and durable. Methods We tested the viability of two low-cost substrates—concrete and recycled blue crab ( Callinectes sapidus ) traps—in facilitating oyster recovery in a replicated 22-month field experiment at historically productive but now degraded intertidal oyster grounds on northwestern Florida’s Nature Coast. Throughout the trial, we monitored areal oyster cover on each substrate; at the end of the trial, we measured the densities of oysters by size class (spat, juvenile, and market-size) and the biomass and volume of each reef. Results Oysters colonized the concrete structures more quickly than the crab traps, as evidenced by significantly higher oyster cover during the first year of the experiment. By the end of the experiment, the concrete structures hosted higher densities of spat and juveniles, while the density of market-size oysters was relatively low and similar between treatments. The open structure of the crab traps led to the development of larger-volume reefs, while oyster biomass per unit area was similar between treatments. In addition, substrates positioned at lower elevations (relative to mean sea level) supported higher oyster abundance, size, and biomass than those less frequently inundated at higher elevations. Discussion Together, these findings indicate that both concrete and crab traps are viable substrates for oyster reef restoration, especially when placed at lower intertidal elevations conducive to oyster settlement and reef development.more » « less
-
NA (Ed.)Oyster reef restoration efforts and on-bottom aquaculture are frequently plagued with high predation rates. Oysters are phenotypically plastic, and rearing juvenile oysters, Crassostrea virginica, with predator cues causes them to grow stronger shells that increases survivorship in the field. However, induced defenses (e.g., shell hardening in oysters) are often associated with cost-benefit trade-offs, and the extent the increased shell strength persists into adulthood and alters the growth of somatic and reproductive tissues remains unknown. We raised diploid oysters (used in reef restoration) and triploid oysters (used in aquaculture) with and without predator cues for one month before placing individuals on an oyster farm to grow to market size. Oyster shell characteristics, soft tissue mass, and reproductive investment were measured periodically over one year of culture and compared across treatments. Both diploid and triploid oysters had significantly stronger and smaller shells than controls at the end of their nursery period. However, while diploid shells became 15 % stronger and 17 % smaller than controls, triploid shells became 28 % stronger and 23 % smaller. Additionally, triploid oysters exposed to predator cues returned to the size of controls faster and maintained their shell strength differences longer than diploids. Differences in soft tissue mass between treatments mirrored the patterns exhibited in shell size and weight with greater initial physiological costs and faster recovery for triploid individuals. There was no significant difference in somatic or reproductive tissue mass between induced and control oysters of the same ploidy after seven months in the field. Triploid oysters were 15–110 % larger than diploids depending on the characteristic measured at maturity. Additionally, there was a significant interaction between treatment and ploidy because induced triploids had marginally greater growth than their control counterparts while induced diploids had marginally less growth than controls. These findings demonstrate that physiological costs of oysters reacting to predators in early life stages are minimal by the time individuals reach maturity. Early exposure to predator cues is a promising tool for improving oyster survivorship in restoration and aquaculture operations, especially in regions with high predation pressure.more » « less
-
Telesca, L (Ed.)Rapid environmental changes are predicted to impact shellfish abundance and their commercial value. The Eastern Oyster, Crassostrea virginica, a key foundation species with high environmental and commercial value has dramatically declined due to climate and anthropogenic impacts over the last century. Our current understanding of oyster vulnerability mostly stems from laboratory-based experiments but lacks studies in natural systems. Here, we investigated how shell production and composition of C. virginica are affected by natural salinity gradients under different temperature regimes. We studied variations in oyster shell shape, production, structure, composition, and organic matrix content in oysters from a temperate, Hudson River (NY), and subtropical, Galveston Bay (TX), estuary. parameters such as weight, area, density, chalk production, and organic matrix to see how the shells varied based on salinity and temperature. Our findings showed that Eastern oysters produced shells with higher chalk content under calcification-limiting environments (i.e., low temperature and low salinity). In comparison, shells with lower chalk content were produced in high predation environments (i.e., high temperatures and salinity). Temperate oyster's shell structure preferentially favored chemical protection against dissolution while subtropical oysters preferentially favored mechanical protection against predation. Oyster’s shell showed a strong capacity for protective responses under calcification- and predation-controlled environments.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.2983/035.042.0103
