percentage corresponding to different taxonomic groups (of increasing complexity) and to ecosystems. Phy, Phytoplankton; Zoo, Zooplankton; Biv, Bivalves; Dec, Decapods; Fsh, Fish; Sgr, Seagrass; Krishna et al. 10.3389/fmars.2024.1481734organic matter production and remineralization stimulates microbial mercury methylation which results in bioaccumulation of neurotoxic monomethyl mercury in phytoplankton (Soerensen et al., 2016). Metals like cadmium, nickel and copper are shown to make coastal areas more heterotrophic by increasing ecosystem respiration (Wiegner et al., 2003; Sundbäck et al., 2007; Nikulina and Dullo, Eco, Ecosystem.2009). However, some trace metals such as iron, silicon and copper on synergism and light blue a low score. For an explanation of the stressor abbr Frontiers in Marine Science 08stressor-pair scores. A dark blue tone indicates a high score for eviations see Figure 4.4.3 Bivalves Bivalves are the second most studied taxonomic group after phytoplankton in the multistressor literature. The most critical interactive stressor for bivalves is ocean acidi?cation combined with climate warming. The sensitivity to acidi?cation is a consequence of the production of calcium carbonate shells (Gazeau et al., 2013); the sensitivity to warming is metabolic stimulation with higher temperature, up to a critical threshold (CTmax) at which physiological process rates start to decline again (Schulte et al., 2011; Marshall et al., 2011; Giomi and Pörtner, 2013).estuarine waters by increasing the cellular uptake rates of macronutrients (Paerl, 1997; Zhang, 2000). Sometimes, the mechanisms employed by algal species to deal with metal and nutrient contamination can have negative consequences for other species or for the entire ecosystem. For example, the diatom Pseudo- nitzschia produces toxic domoic acid in response to copper-stressed conditions in nutrient-rich coastal waters, which is linked to amnesic shell?sh poisoning (Maldonado et al., 2002). Regardless of the intensi?cation or reduction in primary production or adaptation of a defense mechanism, the synergistic effects of metal and nutrients on phytoplankton are signi?cant; and as autotrophs constitute the base of coastal food webs, changes in their growth, defense or community- structure dynamics can greatly impact organisms at higher trophic levels and the ?ow of energy and matter. Eutrophication and metal pollution mediate other stressors too, such as hypoxia. In large parts of the coastal ocean, eutrophication and metal pollution lead to hypoxia, which in turn stimulate metal eco-toxicity. For example, hypoxia increases the bioavailability of manganese in sediment, potentially increasing its toxicity for pelagic and benthic organisms (Mustafa et al., 2012; Eriksson et al., 2013). FIGURE 9 Study types (?eld, laboratory, and modelling) expressed in terms ofcould stimulate primary production in eutrophic coastal and FIGURE 10 Critical stressor combination for phytoplankton (A) and bivalves (B) basedfrontiersin.org