Aragonite Saturation State as an Indicator for Oyster Habitat Health in the Delaware Inland Bays

Abstract

Bivalves such as oysters rely on aragonite and calcite for shell formation via the biomineralization of calcium carbonate. Ocean acidification reduces carbonate ion availability, compromising shell growth and inducing dissolution under undersaturated conditions ($\Omega$ < 1). This study assessed the aragonite and calcite saturation state ($\Omega$) as a proxy for evaluating habitat suitability for oyster aquaculture and restoration. Temperature, salinity, pH, and total alkalinity were monitored across multiple sites and used to calculate the aragonite and calcite saturation state via the Seacarb package. Calcium hardness and dissolved oxygen were also measured to evaluate compliance with hatchery water quality standards. Results indicated temporal and spatial fluctuations in saturation states, with frequent undersaturation during cooler months. Spearman correlation analyses demonstrated significant positive relationships between temperature and salinity (p = 0.46), between pH and aragonite saturation state (p = 0.72), and between alkalinity and aragonite saturation state (p = 0.51). These findings highlight the importance of carbonate chemistry variability and seasonal drivers in determining the suitability of sites for oyster cultivation and restoration under changing environmental conditions.

1. Introduction

Climate change is a significant challenge facing the modern world. Human activities have driven the increase in atmospheric carbon dioxide (CO₂), contributing to global climate shifts. One concerning consequence of these changes is ocean acidification, which poses serious threats to marine ecosystems, particularly shellfish populations. Estuarine ecosystems are especially susceptible to acidification [1] and anthropogenic influences. In the Delaware Inland Bays, eutrophication has become a serious concern, largely driven by urbanization, agricultural activities such as poultry farming, and low water flushing rates [2]. According to the 2021 State of the Bays report, excessive nutrient inputs have earned the Bays a “poor” rating, as they far exceeded healthy ecological limits [2]. This rating was determined based on the evaluation of six aspects of the Bays’ health, including watershed condition, nutrient pollution, water quality, living resources, human health risks, and climate, and assigning each a status (i.e., very good, good, fair, poor, or very poor) and trend (i.e., improving, degrading, or no trend). The data are collected from over 30 long-term monitoring sites, assessing indicators such as the nutrient concentrations of nitrogen and phosphorus, dissolved oxygen levels, water clarity, and the presence of aquatic vegetation and wildlife. Moreover, the intensification of agricultural practices in this region, combined with other anthropogenic factors (i.e., fossil fuels, deforestation, and additional agricultural and industrial practices) [3], exacerbate CO₂ and methane emissions, fueling climate change and amplifying concerns about its cascading effects on estuarine ecosystems, including those in the Delaware Inland Bays. Over the years, there has been a steady increase in the amount of CO₂ released, with at least 50% of the increase occurring in the past three decades [4]. As the concentration of hydrogen ions ($H^{+}$) increases in the seawater due to its reaction to CO₂, the pH decreases, and the water becomes more acidic. Ocean CO₂ uptake also lowers carbonate ion (CO₃²⁻) concentrations and calcium carbonate (CaCO₃) saturation state globally [5]. In addition, as methane breaks down, it oxidizes into CO₂ which directly contributes to more CO₂ uptake by oceans.

Eastern oysters (Crassostrea virginica) are a keystone species and are vital to the estuarine ecosystem. C. virginica provide many ecological services that benefit both humans and wildlife, including filtration, nutrient removal, shoreline protection, and providing food and habitation to aquatic species [6,7,8]. In addition to the ecological benefits of C. virginica, they are an important commercial species that have significant economic value for coastal regions [9]. The consumption and sale of oysters dates back to pre-colonial times. The first commercial oyster fishery originated in the early 1800s and was a growing industry in the 1950s, with more than 4000 acres of subaqueous land leased in Rehoboth Bay and Indian River Bay. However, the leased acreage and survivability of the oysters began to decline through the 1960s due to MSX and Dermo, which contributed to a 95% mortality. By 1978, there was no oyster production in the Inland Bays [10,11]. Shellfish aquaculture once again allowed leasing and harvesting in the Delaware Inland Bays in 2017 when there was a re-emergence of the oyster population. In present day, the shellfish aquaculture industry accounts for over USD 100,000 annually in generated state revenue [10]. Shellfish aquaculture farms also provide ecological benefits as well. The complex structures that are associated with aquaculture farms (i.e., gear, oyster cages, and bags) can provide habitat structure and can become an established feeding ground [12] for pelagic and benthic species.

Water quality is one of the important indicators of a healthy environment for bivalves. Temperature and salinity are both factors that can affect oyster growth and development. Although oysters are tolerant to fluctuating water temperatures and salinity levels [13,14], the ideal temperature for adult oysters ranges from 20 to 30 °C [15,16], and the optimal salinity range is from around 14 to 28 ppt [6]. Dissolved oxygen (DO mg/L) is also necessary for oyster survival, and 4 mg/L is considered the minimum level to maintain a healthy ecosystem [17] for oysters and other aquatic species. The pH measures the concentration of hydrogen in the water and is another important indicator of oyster health. Adult C. virginica can survive in pH levels between 6.75 and 8.75 [16]. Studies have shown that juvenile oysters are more sensitive to lower pH compared to adults [18,19]. The optimal pH range for juveniles is from 7.8 to 8.2. Values less than from 7.4 to 7.6 have been shown to impair the shell formation, growth rates, and survival of juvenile oysters [18,19]. When pH levels drastically decrease due to ocean acidification, this can impact the oysters’ ability to form their shells and can lead to poor survival. Alkalinity measures the capacity of water to buffer pH and neutralize acids. This can help prevent stress in oysters that result from rapid changes in pH. The recommended alkalinity level for shellfish hatcheries is between 150 and 180 mg/L [20]. Calcium hardness measures the amount of calcium ions in the water. Calcium binds with carbonate to form calcium carbonate (CaCO₃), which is used by oysters to form their shells. The recommended calcium hardness level for shellfish hatcheries is around 200 mg/L CaCO₃ [20]. Although Eastern oysters have a high tolerance and adaptability potential, optimal conditions are preferred to maximize growth and productivity.

Aragonite and calcite are the main calcium carbonate structures utilized by calcifying species to build their shells [21]. Aragonite is mainly utilized by oyster larvae, while juvenile and adult oyster shells are composed primarily of calcite. The Aragonite and Calcite Saturation State ($\Omega$) is a measure of the carbonate ion concentration in the water. However, the Aragonite Saturation State is considered a better indicator of ocean acidification due to its solubility [22,23]. In one study, a decline in the long-term pH and $\Omega$_Ar contributed, in part, to ocean acidification [24]. In contrast, researchers observed an increase in the long-term pH and $\Omega$_Ar with increased alkalization. In a study, two oyster species were exposed to varying levels of CO₂ to simulate different atmospheric conditions and found that C. virginica grew slower and biomineralized less calcium carbonate at elevated CO₂ levels [23]. In a similar study, bivalve and larvae were exposed to past, present, and future CO₂ conditions, and larvae demonstrated greater growth and survival under pre-industrial conditions compared to modern CO₂ levels [25]. Bivalve also demonstrated enhanced calcification under pre-industrial conditions but experienced shell deformities when exposed to predicted future CO₂ levels. Thus, understanding the aragonite saturation state can help to monitor the effects of climate change. The following formula is used to calculate the saturation state of seawater:

$$\Omega ={\displaystyle \frac{\left[{CO}_3^{2-}\right]\times \left[{Ca}^{2+}\right]}{K_{sp}^{*}}}$$

where [${Ca}^{2+}$] is the calcium concentration, and $K_{sp}^{*}$ is the solubility product of aragonite [23,26]. Aragonite and calcite values greater than one are considered supersaturated $(\Omega$ > 1) and more favorable, while values under one are undersaturated ($\Omega$ < 1) and favor dissolution [5,23]. When the saturation state falls below one, this can cause calcifying organisms to become stressed due to the elevated metabolic cost of calcification under less favorable conditions and can also decrease the shell area and calcium content of the oysters’ shells. Undersaturated levels also have the potential to slow down the species’ rate of calcification, so they have to remain in the water column for longer periods. With the integrity of their shells at odds, coupled with the slower rate of calcification, this makes them more susceptible to disease and predation [23]. These effects ultimately affect the ecosystem services that oysters provide and may hinder aquaculture practices.

The Aragonite Saturation State will help us to better understand the impacts of ocean acidification on the calcification process of C. virginica. Saturation states may lead to shifts in habitat function, composition, and the provision of ecosystem services provided by oysters since they are “ecosystem engineers” [27,28]. The objectives of this study were to (1) monitor physiochemical water quality conditions at different habitat types in relation to oyster suitability, (2) calculate the omega aragonite and calcite saturations states at each site using water quality data, and (3) compare water quality conditions to determine the suitability of different sites for oyster aquaculture and restoration efforts. This study provides one of the first multi-year and multi-site assessments of carbonate saturation states in Rehoboth Bay. By exploring spatial and temporal trends, this study offers critical insights into the susceptibility of calcifying organisms and estuarine ecosystems to ocean acidification.

2. Materials and Methods

2.1. Study Sites

The Delaware Inland Bays is a natural estuary that covers 32 square miles of surface waters, located within a 320 square mile watershed [10,11]. The three systems that make up the Delaware Inland Bays include Rehoboth Bay, Indian River, and Little Assawoman. The Inland Bays account for over USD 4.5 billion in annual state income and supports over 35,000 jobs including those in the fisheries and aquaculture, tourism and recreation, infrastructure, and goods and services industries [10]. Rehoboth Bay is located in the northernmost part of the Inland Bays and is an important ecological and recreational region. There was a total of seven sites located in Rehoboth Bay, DE, USA that were monitored in this study. These sites are located on both the east and west side of Rehoboth Bay and are characterized as pilot artificial oyster reefs, private aquaculture farms, and control sites with no oysters or habitat structures (Figure 1). The artificial reefs are located at Camp Arrowhead (CAH, 38.65430° N, 75.12589° W) and Big Bacon Reef (BBR, 38.38007° N, 075.04866° W) and were created using recycled oyster shells and seeded with farm-grown oyster seeds through a program run by the Delaware Center for Inland Bays. The private aquaculture farms are located at Sally’s Cove (SC, 38.64877° N, 75.12870° W) and Rehoboth Bay Oyster Company (RBOC, Rehoboth Beach, USA; 38.39549° N, 075.04797° W), and the majority of the cultured oysters are suspended within the water column using off-bottom cages. The control sites are Sally’s Cove Control (SCC, 38.64446° N, 75.12656° W), Redefer Control (RC, 3839.177° N, 07504.938° W), and Bay City (BC, 3837.857° N, 7507.382° W). SCC is a small beach area with little marsh grass coverage and is located adjacent to Sally’s Cove on the west side of Rehoboth Bay. RC is a former aquaculture site that is no longer operational and has little to no structure remaining. Lastly, BC is a residential inlet that is more heavily influenced by boating and recreational activities.

2.2. Water Quality Monitoring

Temperature, pH, salinity, and dissolved oxygen (DO) were measured once every two weeks in the months from May to November during the early morning–afternoon. From 2020 to 2022, a 556 Handheld Multiparameter Instrument (YSI Xylem Inc., Yellow Springs, OH, USA) was used to collect the physical water quality parameters. In 2023, the prior instrument was replaced by the newer modeled ProDSS Multiparameter Digital Water Quality Meter (YSI Xylem Inc., Yellow Springs, OH, USA). Salinity was measured with a YSI Conductivity and Temperature Sensor and calibrated with 10,000 uS/cm Conductivity Solution traceable to NIST standard reference. Seawater pH was measured with a YSI pH/ORP Sensor and calibrated using a three-point calibration with 4.00, 7.00, and 10.00 YSI buffers traceable to NIST standard reference. The instruments were calibrated before each sampling event to ensure consistency and accuracy. The YSI 556 and ProDSS used a standard NBS scale ranging from 0 to 14. DO was measured with a YSI ODO Optical Dissolved Oxygen Sensor and calibrated with a one-point calibration in water-saturated air. Triplicate water samples were also collected to conduct nutrient analysis tests. Water samples were immediately stored at –20 °C until removal for analysis. Total alkalinity and calcium hardness were measured using a 9500 photometer (YSI Xylem Inc., Yellow Springs, OH, USA) and a colorimetric method. To test for total alkalinity (mg/L CaCO₃), water samples were first transferred to a 10 mL test tube. Then, one total alkalinity (Alkaphot) reagent (YSI Xylem Inc., Yellow Springs, OH, USA, Ca. No. YAP188) tablet was added and mixed until completely dissolved. The solution rested for one minute before it was placed into the 9500 photometer for analysis. Alkalinity mg/L CaCO₃ can be converted to μmol/kg of seawater using the following formula:

$$\mathrm{A}\mathrm{l}\mathrm{k}\mathrm{a}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{y}\left(\mathsf{\mu }\mathrm{m}\mathrm{o}\mathrm{l}/\mathrm{k}\mathrm{g}\right)={\displaystyle \frac{\mathrm{m}\mathrm{g}/\mathrm{L}{\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3\times 1000}{50}}=\mathrm{m}\mathrm{g}/\mathrm{L}{\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3\times 20$$

To test for calcium hardness (mg/L CaCO₃), water samples were first transferred to a 10 mL test tube. Then, one Calcicol No.1 (YSI Xylem Inc., Yellow Springs, OH, USA, Ca. No. YAP252) tablet was added to the sample and mixed until dissolved. After, one Calciol No.2 tablet was added to the solution and mixed until completely dissolved. The solution rested for two minutes before it was placed into the analyzing instrument.

2.3. Calculation of Aragonite Saturation State

The Aragonite Saturation State was calculated using the Seacarb program package in R (version 4.1.0). Seacarb is an open-source package that is widely used for carbonate calculations and simulating changes in seawater chemistry. This package provides robust formulas and built-in algorithms for analyzing marine carbonate systems, making it an essential tool for oceanographic and water quality studies. To calculate the $\Omega$Ar, a set of water quality parameters—temperature, salinity, pH, and total alkalinity– were inputted into the Seacarb program. The calculations leveraged Seacarb’s built-in functions to determine the omega aragonite and calcite saturation state based on these inputs. Additional outputs included CO₂, HCO₃, CO₃, DIC, pCO₂, and fCO₂. We utilized the ‘Seawater pH scale’ in Seacarb, which is designed for marine environments and is commonly used when measuring seawater acidity. To visualize the data, statistical graphs were developed in Rstudio (version 4.3.1) and Python (version 3.13.3), incorporating tools for advanced data visualization. These graphs demonstrated the average aragonite and calcite saturation states across multiple study sites over a temporal range from 2020 to 2023. Spearman correlation heatmaps were also developed in Rstudio to identify relationships between physiochemical water quality parameters and the saturation states.

3. Results

3.1. Physiochemical Water Quality Monitoring

Average water quality data are presented for the temperature, salinity, pH, dissolved oxygen, total alkalinity, and calcium hardness at all sites from May to November 2020–2023 (

Table 1. Average physiochemical water quality values between the different sampling years. Note: Data are presented based on the mean value of three different repeats.

Year	Temperature (°C)	Salinity (ppt)	pH	DO (mg/L)	Alkalinity (mg/L CaCO3)	Calcium Hardness (mg/L CaCO3)
2020	23.0 ± 4.8	29.0 ± 3.0	7.96 ± 0.2	8.61 ± 1.6	82.0 ± 27.4	254.41 ± 79.8
2021	21.6 ± 5.6	28.5 ± 1.2	8.04 ± 0.1	5.84 ± 1.4	92.3 ± 27.7	261.51 ± 59.4
2022	23.0 ± 4.8	33.56 ± 2.0	7.83 ± 0.35	7.52 ± 1.7	87.9 ± 25.7	223.64 ± 60.7
2023	23.1 ± 3.6	26.50 ± 8.7	7.77 ± 0.46	6.87 ± 1.5	86.0 ± 20.5	221.31 ± 58.0

). There were no significant differences in temperature across the four years. BC consistently recorded the highest temperatures, and BBR the lowest (Figure 2). Salinity was relatively stable in 2020 and 2021, increased slightly in 2022, and then declined in 2023—particularly during May and June. BBR had the highest overall average salinity, whereas BC had the lowest (Figure 3). No significant variation in pH levels was observed across the four years, and it remained within an optimal range for shellfish growth. RBOC and RC had the highest average pH, while BC had the lowest, showing potential vulnerability to acidification (Figure 4). For dissolved oxygen, RBOC recorded the highest overall average DO, and BC recorded the lowest (Figure 5). Seasonal fluctuations followed expected trends, with higher DO in cooler months. Alkalinity showed the greatest interannual and site-specific variation, with notable declines observed at SCC in both 2021 and 2023. The site with the highest average alkalinity varied by year, but SCC consistently recorded the lowest overall values (Figure 6). Calcium hardness (mg/L CaCO₃) was similar between 2020 and 2021 and between 2022 and 2023, respectively. CAH had the highest overall average calcium hardness, while the site with the lowest values varied each year (Figure 7).

3.2. Calculated Aragonite–Calcite Saturation States

Average omega aragonite and calcite saturation state were calculated for each site across the four-year period (

Table 2. Average omega aragonite and calcite saturation state between the different sampling sites and years. Note: Data are presented based on the mean value of three different repeats.

Sites	Year	Omega Aragonite	Omega Calcite
BBR	2020	0.72 ± 0.2	1.10 ± 0.3
	2021	1.10 ± 0.5	1.70 ± 0.7
	2022	0.77 ± 0.1	1.19 ± 0.2
	2023	0.90 ± 0.5	1.40 ± 0.8
BC	2020	1.31 ± 0.4	1.80 ± 0.7
	2021	1.05 ± 0.6	1.60 ± 1.0
	2022	0.58 ± 0.4	0.88 ± 0.6
	2023	0.49 ± 0.3	0.77 ± 0.5
CAH	2020	1.19 ± 0.5	1.80 ± 0.8
	2021	1.16 ± 0.5	1.80 ± 0.8
	2022	0.86 ± 0.3	1.31 ± 0.4
	2023	0.75 ± 0.4	1.20 ± 0.7
RBOC	2020	0.99 ± 0.5	1.50 ± 0.7
	2021	1.20 ± 0.6	1.80 ± 0.9
	2022	1.02 ± 0.2	1.56 ± 0.3
	2023	0.97 ± 0.4	1.51 ± 0.6
RC	2020	0.49 ± 0.2	0.80 ± 0.3
	2021	1.38 ± 0.6	2.10 ± 0.9
	2022	0.92 ± 0.4	1.41 ± 0.6
	2023	0.87 ± 0.5	1.37 ± 0.8
SC	2020	1.34 ± 0.4	2.10 ± 0.7
	2021	1.10 ± 0.4	1.70 ± 0.6
	2022	0.80 ± 0.2	1.22 ± 0.4
	2023	0.67 ± 0.3	1.05 ± 0.5
SCC	2020	0.48 ± 0.3	0.80 ± 0.4
	2021	0.88 ± 0.6	1.40 ± 0.9
	2022	0.90 ± 0.3	1.38 ± 0.5
	2023	0.77 ± 0.5	1.21 ± 0.8

). Both saturation states exhibited significant spatial and temporal variability across sites and seasons (Figure 8). Monthly values occasionally fell below the critical threshold of $\Omega <1$, indicating undersaturation and the potential for shell dissolution, particularly during cooler months. The peak saturation occurred during the months from May to June likely due to increased photosynthetic activity and temperature, which elevated pH and carbonate ion concentrations. This then started to decline after August, with the lowest values observed in October and November. There was higher variability in the spring and early summer months, indicating strong seasonal drivers. The most frequent undersaturated conditions occurred in 2023, aligning with a concurrent decline in salinity and calcium hardness levels, suggesting a possible connection between freshwater input and reduced saturation state. Calcite saturation followed similar trends to aragonite but consistently showed slightly higher values, which was expected given calcite’s lower solubility. SCC had the lowest average saturation state in 2020, while SC had the highest. In 2021, SCC again had the lowest average, and RC the highest. In 2022, BC had the lowest average, with RBOC recording the highest. By 2023, BC continued to have the lowest average saturation state, while RBOC had the highest.

3.3. Correlations Between Water Quality and Saturation States

Spearman correlation heatmaps were used to understand the relationships between the different water quality parameters and the calculated Aragonite Saturation State at each site (Figure 9). The red boxes indicate significant positive correlations, while the blue boxes indicate significant negative correlations (the darker the color is, the stronger the relationship is). At Big Bacon Reef, there was a significant negative relationship between salinity and pH (p = −0.43), while there were significant positive relationships between alkalinity and aragonite (p = 0.37) and between pH and aragonite (p = 0.53). At Rehoboth Bay Oyster Company, there was also a negative relationship between pH and salinity (p = −0.38) and between temperature and dissolved oxygen (p = −0.53), while there were positive relationships between temperature and salinity (p = 0.46) and between pH and aragonite (p = 0.63). At Redefer control, there were negative relationships between salinity and pH (p = −0.42) and between salinity and calcium hardness (p = −0.38), and significant positive relationships again between temperature and salinity (p = 0.38) and between pH and aragonite (p = 0.60). At Sally’s Cove, there were no significant negative relationships, but there was a significant positive relationship between pH and aragonite (p = 0.63). At Camp Arrowhead, there were no significant negative relationships, but there was a significant positive relationship between temperature and salinity (p = 0.37), between calcium hardness and aragonite (p = 0.39), and between pH and aragonite (p = 0.72). At Sally’s Cove Control, there were again no significant negative relationships, but there were significant positive relationships between pH and aragonite (p = 0.38) and between alkalinity and aragonite (p = 0.51). Lastly, at Bay City, there were no significant negative relationships as well, but there were significant positive correlations between temperature and salinity (p = 0.37), between temperature and calcium hardness (p = 0.41), and between pH and aragonite (p = 0.59). At a majority of sites, there were strong correlations between pH, alkalinity, and omega aragonite, which demonstrates the relationships between these parameters and how they can impact the aragonite saturation state in the future.

4. Discussion

Most parameters showed seasonal patterns, with some interannual changes—notably a decline in salinity, alkalinity, and aragonite saturation in 2023. BC and SCC exhibited lower pH, alkalinity, and saturation state, increasing susceptibility to acidification. The water conditions at BC may be influenced by its proximity to residential development and greater anthropogenic inputs affecting water quality. RBOC and CAH consistently maintained more favorable conditions for oyster health. Across the four years, temperature, pH, salinity, and dissolved oxygen remained within optimal ranges for oyster growth. Calcium hardness values showed more variability between sites and seasons but generally met hatchery recommendations of approximately 200 mg/L. In contrast, average alkalinity values across sites were consistently below the recommended range for shellfish hatcheries (150–180 mg/L) [20]. Reduced alkalinity may diminish the buffering capacity of the water, potentially making oysters more susceptible to pH fluctuations and the broader impacts of ocean acidification. There were notable variations in both the Aragonite and Calcite Saturation State levels. Oftentimes, the Aragonite Saturation State values were falling below $\Omega <1$, indicating undersaturation and an increased risk of shell dissolution. There was a notable decrease in both saturation state values in 2023 across nearly all sampling sites. During that same year, there was a mass mortality event observed at our aquaculture site, SC, where approximately 85% of the oysters collected were dead. Heatmap analysis revealed significant positive correlations between pH, alkalinity, and the Aragonite Saturation State. This relationship was expected, as reduced pH (indicative of ocean acidification) directly affects carbonate availability and lowers saturation states. Similarly, temperature and salinity were also positively correlated with saturation states. As temperature and salinity increase, CO₂ solubility decreases, leading to CO₂ outgassing and increased carbonate saturation. Conversely, in deeper, cooler, and more saline waters with higher dissolved CO₂ from respiration, the saturation state declines [4,29].

An important factor not directly monitored in this study is the potential feedback oysters themselves may exert on carbonate chemistry. Oysters contribute to biogeochemical changes through calcification and respiration. As they form their shells, they remove calcium and carbonate ions from the water, potentially lowering local saturation states. Additionally, respiration and calcification processes can release CO₂, further influencing water chemistry [30]. These effects are particularly relevant in dense aquaculture systems. One study formulated a predictive model to account for the impact of calcification on the estuarine carbonate system and estimated that oysters can decrease the aragonite saturation state by 3% during the growing season [30]. Interestingly, our data from 2020 to 2021 showed that control sites (i.e., locations without oysters) had lower saturation states compared to aquaculture farms and oyster reefs. Furthermore, Spearman correlation analysis found no significant relationship between calcium hardness and Aragonite Saturation State, suggesting that calcium alone may not drive saturation dynamics at these estuarine sites. Nevertheless, the role of oyster-driven biogeochemical feedback warrants further investigation, as it could have important implications for both aquaculture and restoration practices [30] in Delaware and similar estuarine systems.

5. Conclusions

Understanding the role of water quality and conducting continuous water quality monitoring is essential to maintaining a healthy environment for wildlife. The Aragonite–Calcite Saturation State also shows a potential to better understand the effects of ocean acidification and climate change on oysters and our estuarine environments. In the future, predictive models can be formulated to monitor the aragonite–calcite saturation state to account for future trends that impact both larvae and juvenile–adult oysters. These considerations can help promote sustainable aquaculture practices and an understanding of how oysters increase biodiversity and ecosystem function can promote continued reef restoration efforts in the Delaware Inland Bays.