The Complexity of Aquaculture Sustainability

Aquaculture, like all food production activities, has an environmental impact. Unlike other sectors of the agrifood system, aquaculture is highly diverse, and its impacts are varied and complex, extending from nutrient cycles to carbon dynamics and are determined by the wide range of farmed species, culture systems, practices, and locations. For the sector to thrive and achieve greater sustainability, it must remain genuinely committed to continuous improvement, innovation, and transparent, honest reflection on its practices. This final issue of 2025 of Reviews in Aquaculture (Volume 17, Issue 4) includes a series of important contributions on environmental sustainability that invite reflection on what I call here “the complexity of aquaculture sustainability”. Life Cycle Assessment (LCA) is an effective tool for systematically evaluating the environmental impacts of a product or process across its entire life cycle, from raw material extraction to production, distribution, use, and disposal. Reviewing previously published LCA studies, Budhathoki et al. [1] showed that feed, rather than farming system design, is the true sustainability bottleneck in salmon aquaculture, with feed production dominating impacts such as global warming and eutrophication, even though nitrogen emissions remain underestimated. The authors' key message was that systemic gains will come not from choosing “the right system” but from innovating in feeds and energy. This study helps underscore both the power and the limits of LCA. In fact, LCA can reveal critical hotspots, but if interpreted too broadly it may obscure complexity and reinforce oversimplified generalisations. Focusing on nitrogen emissions, and moving from salmon to shrimp and from LCA to a deeper eco-physiological study, the review by Bian et al. [2] showed that nitrite is not just a water-quality parameter but a fundamental ecological stressor linking shrimp physiology, microbial balance, and ecosystem degradation. The review combined mechanistic insights with practical interventions such as biofloc, probiotics, and antioxidant feeds, presenting a framework that clearly identified nitrite as both a productivity constraint and an ecological threat. This case illustrated how system-level metrics like LCA must be complemented by detailed eco-physiological understanding for a balanced assessment of sustainability. Moving from pollution generated by aquaculture to environmental pollution impacting aquaculture, Huvet et al. [3] reviewed the effects of micro- and nanoplastics in bivalve farming. The authors showed that while microplastics seldom cause acute mortality in oysters and mussels, they induce persistent sublethal impacts, ranging from impaired energy metabolism and immune function to reduced reproductive success. An important and novel contribution of this study was the link between organism-level effects and broader ecosystem and industry feedbacks, including the role of aquaculture gear, waste, and packaging as contamination sources. In doing so, the authors showed that plastic pollution is responsible for chronic, system-wide stressors that directly affect the health, reproduction, and ecosystem services of oyster and mussel aquaculture. The study reframed plastic pollution as both a husbandry challenge and a governance imperative, calling for regulation of plastic additives, stronger waste management, and safer materials. Following on mariculture, a novel study by Krause et al. [4] challenged the assumption that “local is always better.” The study showed that regionalisation offers potential gains such as reduced transport emissions, circular feed use, and stronger local governance. However, it also carries significant trade-offs, including higher costs, land-use conflicts, and social displacement. The authors applied a five-dimensional sustainability framework (ecological, economic, social, governance, cultural) to show how benefits in one domain may be offset by risks in another. In doing so, Krause et al. [4] reframed regionalisation as neither inherently sustainable nor unsustainable. Instead, the study positioned it as a diversification strategy: partial regional capacity, combined with global linkages, can strengthen resilience if guided by adaptive governance that integrates cultural as well as ecological values. Turning from generalisations to the question of science–policy alignment in mariculture, Ruff et al. [5] exposed a critical mismatch. By contrasting scientific studies with national policies across several countries, the review showed that the vast majority of both literature and policy frames mariculture as threatened by climate change. However, the research highlighting the adaptive and mitigating capacities of seaweed and bivalve farming remains largely absent from policy frameworks. The study identified this imbalance and pointed to the need for closer research–governance alignment to position mariculture as part of climate solutions. However, the progress of science is not always linear, particularly for complex and multifaceted issues such as sustainability. At times, authors and researchers disagree, and scientific debates are essential for advancing knowledge. In this issue, we published a letter by Pernet et al. [6], the third part of a three-paper exchange on whether bivalve farming should be considered a CO2 sink. Pernet et al. [7] first argued against the notion. He et al. [8] then responded with data and a new budget framework suggesting it might act as a weak sink, and Pernet et al. [6] replied by identifying methodological gaps and urging caution. This exchange exemplifies a fundamental aspect of science: open, transparent debate that acknowledges uncertainty, exposes assumptions, and sharpens methodologies. On complex issues such as aquaculture's environmental footprint, disagreement, when public and constructive, can be a driver of progress. The environmental impacts of aquaculture are multiple and complex, and the sector must continually evolve to address them. However, broad generalisations, whether through simplified LCAs, popular narratives, or selective framings in policy, risk adding confusion and widening the science–policy gap. I believe we need more open, transparent, and respectful scientific debates to help us navigate this complexity and ultimately move toward genuinely sustainable solutions. I also acknowledge that the studies highlighted in this editorial draw heavily on examples from the Global North. Whilst this is understandable, particularly because these are reviews based on available studies, we need to increase future work focusing on the Global South, where aquaculture is growing most rapidly and where sustainability challenges and opportunities are often most acute. I hope you find value in this final issue of Reviews in Aquaculture for 2025 and recognise the journal's commitment to providing a space for rigorous scientific advancement, exchange, and open debate. As we look ahead, our aim is for Reviews in Aquaculture not only to foster dialogue within the research community but also to help bridge the science–policy gap, contributing to the continuous improvement of aquaculture's environmental sustainability in all its complexity. Giovanni M. Turchini: conceptualization, writing – original draft, writing – review and editing. I used ChatGPT (OpenAI) to assist with grammar, readability, and style. All content and conclusions are my own and have been verified for accuracy. Declaring such use openly reflects my view that AI, when applied responsibly, can be a useful ally in scholarship. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.