advanced search and Google Scholar with similar functions. The Krishna et al. 10.3389/fmars.2024.14817341 Introduction Coastal ecosystems are exposed to a plethora of direct and indirect anthropogenic stressors such as climate warming, eutrophication, metal pollution, hypoxia, pH and salinity changes, and over?shing (Halpern et al., 2007; Crain et al., 2008; Griffen et al., 2016; Gissi et al., 2021). These stressors are inducing serious and irreversible changes in marine and coastal food webs (Carrier- Belleau et al., 2021), and they do not act in isolation but instead simultaneously (Griffen et al., 2016). It has been suggested that by 2050 about 90% of the global ocean will be impacted by exposure to multiple stressors (Henson et al., 2017). Interactions between stressors trigger responses in species and communities that are often different from the effects of the individual stressors (Crain et al., 2008; Jackson et al., 2016). To understand the changes in coastal ecosystems and to improve marine and coastal management, a better knowledge of stressor interactions is required (Gladstone-Gallagher et al., 2023; Gissi et al., 2021). The interactive effect of multiple stressors could be the sum of the individual responses, more than that, or less. When the combined effect of multiple stressors is equal to their expected cumulative sum, such an effect is called additive. When this is not the case, it is termed multiplicative or non-additive (both used interchangeably) (Pirotta et al., 2022). A non-additive effect could, in turn, be synergistic or antagonistic. When the net effect of interactions is greater than the sum of individual stress responses, the response is called synergistic (Crain et al., 2008; Jackson et al., 2016). On the contrary, in an antagonistic interaction, the effect intensity of the combined response is less than that of the cumulative single-stressor effects. Occurrences of additive and non-additive interactions have been reported in coastal ecosystems (Crain et al., 2008; Villar- Argaiz et al., 2018). For example, synergistic responses to elevated nutrient concentrations and metal loadings have been found in diverse plankton groups (Bundy et al., 2003; Wiegner et al., 2003; Simboura et al., 2016; Abbate et al., 2017). Negative synergistic effects have been reported in benthic organisms (such as crabs and bivalves) on exposure to ocean acidi?cation (OA), salinity, temperature, and metal pollution (Stueckle, 2008; Miller et al., 2014; Brooks and Crowe, 2019). The combined effects of heat stress and OA have been far more adverse than their individual effects in a variety of mussel species (Vihtakari et al., 2013; Rodrigues et al., 2015). Likewise, the adverse effects of over?shing can be intensi?ed by climate warming in top predatory ?sh species (Ainley and Blight, 2009). Stressor interactions also lead to antagonistic responses in coastal ecosystems. For example, it has been shown that elevated CO2 resulted in higher chlorophyll biomass under low irradiance, thereby compensating for light stress (Neale et al., 2014; Heiden et al., 2018). Similarly, low pH has been shown to have mitigated the negative effect of high temperature on egg volume in an estuarine ?ddler crab (Pardo and Costa, 2021). In spite of the signi?cant role of stressor interactions in driving ecosystem and community-level responses, investigations of these effects are largely disconnected from the implementation of conservation and management policies for coastal systemsFrontiers in Marine Science 02search included a topical search for multiple stressors, compound, cumulative or interactive effects at the coast or on the shelf, classi?ed as an article or review. We implemented the following search query: “TS=(((“multipl* stress*”) OR (“compound* effect”) OR (“cumulat* effect”) OR (“interact* effect”)) AND (coast* or shelves or shelf)) AND DT=(“ARTICLE” OR “REVIEW”)” Abstracts of all obtained records were prescreened independently by two researchers for false positives that should be discarded as not relating to the topic, e.g. articles relating to management and policy, society and socio-ecological systems, single stressors, freshwater systems, marshes or seismology. The review papers contained in the remaining records were screened for references to primary relevant literature that was not captured by the automated search. Citations within review papers that were identi?ed as relevant after screening their abstract were included in the subsequent full-text analysis. All remaining and manually added full texts were distributed for detailed evaluation among the author team. We employed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses [PRISMA, Moher et al. (2009)] approach for our analysis. The systematic search, based on queries and keywords, on WoS and Google Scholar yielded 814 papers that investigated the interactive effects of multiple stressors in marine ecosystems. All of these papers were screened, ?rst by an automated script and then manually, to select the studies that focused only on high-latitude coastal ecosystems, which reduced(Gladstone-Gallagher et al., 2023; Co?te? et al., 2016). Over the last decades, research and management focused on eutrophication problems in coastal environments (Smith and Schindler, 2009). The non-additive effects of eutrophication with other stressors such as climate warming, pollutants, hypoxia and changes in salinity have posed a multidimensional problem (Hewitt et al., 2016; Henson et al., 2017; Thrush et al., 2021). First, the intricacy of interactive effects makes it very dif?cult to elucidate the net response of an ecosystem in ever-changing environments (Carrier-Belleau et al., 2021). Secondly, the occurrence of several stressors triggers differential responses across organisms. Thirdly, critical stressor combinations vary between taxonomic groups. In this study, we address the aforementioned research gaps. With a focus on high-latitude coastal systems, we systematically review the existing studies on the interactive effects of multiple stressors in coastal habitats to answer the following important questions: 1) What are the critical stressors for triggering non- additive responses in coastal ecosystems? 2) What are the main stressor combinations for different taxonomic groups with respect to inducing negative synergistic effects? 3) What are the research gaps in multi-stressor studies? From our ?ndings, we provide valuable insights to scientists and stakeholders with respect to the advancement of multi-stressor research and for management of coastal ecosystems. 2 Materials and methods A systematic literature search for scholarly articles relating to the topic was performed using Clarivate’s Web of Science (WoS)frontiersin.org