Introduction
Agriculture and terrestrial livestock have long been key sources of protein, but they are also associated with significant environmental impacts, including nutrient pollution and greenhouse gas emissions (Ilea, 2009). In contrast, bivalve aquaculture offers a more sustainable protein production system, requiring no feed inputs and delivering valuable ecosystem services such as nutrient remediation and carbon sequestration (Higgins et al., 2011 and Van der Schatte et al., 2020) . This study aims to evaluate the environmental performance of Irish Pacific oyster farming by combining life cycle assessment (LCA) with ecosystem service analysis to understand better its role in reducing eutrophication and mitigating climate change.
Materials and methods
This study assessed ecosystem services and environmental impacts of Pacific oyster farming in Ireland using both field sampling and LCA methodology . Morphological and elemental analyses were undertaken on oysters from two production sites, measuring carbon (C), nitrogen (N), and phosphorus (P) content in both tissue and shell. These values were extrapolated to farm and national levels to estimate annual nutrient removal and assign economic value to this ecosystem service. LCA was performed on three sites using primary farm data and secondary databases, covering activities from seed procurement to processing. Environmental impacts were quantified using the CML method, and nutrient and carbon sequestration in oyster shells were integrated into the LCA results to calculate net eutrophication and greenhouse gas emissions.
Results
The study found that Pacific oyster farming in Ireland provides significant ecosystem services, removing an estimated 834.3 tonnes of carbon, 33.9 tonnes of nitrogen, and 3.9 tonnes of phosphorus from coastal waters annually. The LCA results showed a carbon footprint of 373.86 kg CO₂-eq per tonne of oysters, primarily driven by electricity use and diesel combustion. On the other hand, results showed a eutrophication potential and acidification potential of 0.39 kg PO4 eq. tonne−1 and 1.33 kg SO2 eq. tonne−1 , respectively. Using ecosystem services metrics, one tonne of harvested oysters can remove, on average, 3.05 kg of nitrogen, 0.35 kg of phosphorus, and sequester 70.52 kg of carbon from the environment, thus potentially acting as a nutrient remediator and a short-term carbon sink . From an economic perspective, the valorisation of the nutrient removal potential resulted in an additional income of €1.9 million per year to the Pacific oyster industry, of which N removal accounts for 97.67% .
Discussion
This study provides a comprehensive evaluation of Ireland’s Pacific oyster farming sector, focusing on its contributions to ecosystem services and environmental impacts through a life cycle assessment. While oyster farming demonstrated lower environmental impacts than other protein production systems ( Aubin et al., 2009; Nguyen et al., 2010; Djekic et al., 2015; Kalhor et al., 2016) , challenges remain in assessing nutrient and carbon fluxes due to methodological limitations. The study highlighted the role of biodeposition and denitrification in nutrient cycling (Ayvazian et al., 2021) and stressed the need for improved LCA models to capture these services more accurately. Extrapolations were made under justified assumptions, though future research is needed to account for regional variability. Economically, the Irish oyster industry could benefit from nutrient credit schemes and opportunities within the circular economy , such as reusing shells in agriculture and construction. The findings support the integration of oyster farming into environmental management strategies, including carbon farming and water quality improvement, and advocate for the expansion of environmental footprint assessments to inform sustainable aquaculture policy and practice.
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