te Krishna et al. 10.3389/fmars.2024.1481734FIGURE 1 Schematic representation of our applied Preferred Reporting Items for Sys screen studies from the databases.Frontiers in Marine Science 03matic Reviews and Meta-Analyses (PRISMA) scheme to identify andthe number of papers from 814 to 400 (Figure 1). Out of these, a few were review or synthesis papers which were discarded from the analysis, and the remaining were distributed amongst the co- authors to review and ?ll up the “Summary Table” (Table 1). In total, we could identify 198 studies in which non-additive or additive effects were reported (Figure 1). All further analyses were performed based on the information provided in this table. To quantify the magnitude of interactive effects (synergistic = SYN, additive = ADD, and antagonistic = ANT) for stressor combinations, we implemented a fuzzy coding/scoring method where scores between 1 to 3 were assigned for the reported responses. For example, if a study reports only a synergistic effect for a given stressor combination, a score of 3 is assigned for SYN and a score of 0 for ANT and ADD. If two types of effects (e.g. SYN and ANT or ADD and SYN) are reported then a score of 1.5 is given to each and 0 to the third effect which is missing. And, if all three effects (SYN, ANT, and ADD) could be identi?ed then a score of 1 is assigned to all. For a given stressor pair, the sum of all three effects is always 3 (SYN + ANT + ADD = 3). If there are more than two stressor combinations, then the same procedure is followed for the respective stressor pairs resulting from that particular combination (e.g. 4 stressor combinations yield 6 stressor pairs). The ?nal score for a given effect (SYN or ADD or ANT) is then calculated by adding up their individual scores identi?ed from different stressor combinations. The detailed schematic of this scheme is illustrated in Figure 2. 3 Results Interactive effects are reported at different levels of the coastal ecosystem; the majority (n=109, 55%) of studies focused on the species or organism level, 36% (n=71) on the community level, and 9% (n=18) on the entire ecosystem. The types of effects reported can be classi?ed as synergistic, antagonistic, or additive. Most of the studies either reported additive (n = 62) or synergistic (n = 68) effects, and a few (n=15) reported both (Figure 3). These ?ndings are indicative of the intensi?cation or compounding of responses tomulti-stressor exposure in coastal ecosystems. Whereas ANT effects are identi?ed in only 20 studies (10% of the total). A handful of studies (n = 5) reported both ADD and ANT effects. Likewise, only 12 papers identi?ed both SYN and ANT effects. Lastly, a few (n = 16) reported all three effects. Next, we identi?ed the most investigated stressors that affect various taxonomic groups and communities in coastal ecosystems. The most frequent individual stressors in a multi-stressor constellation are temperature (Temp, 25%, n=50), followed by nutrient loading (Nut, 17%, n=33) and toxic metals/pollution (Metal) and ocean acidi?cation (OA, together 28%, n=56) (Figure 4). While high turbidity and salinity stress are moderately studied (both 11%), hypoxia (DO) and physical/mechanical disturbances (Dist) are the least studied stressors. Quanti?cation of the interactive effects (SYN, ANT, and ADD) for the stressor combinations of the most reported stressors is shown in Figure 5. The combinations of acidi?cation– eutrophication (OA and Nut)frontiersin.org