Table 1. Likely biological responses to changes in ocean biogeochemistry.

	Temperature	pH	Oxygen	Productivity
Body size and growth	Due to temperature control over metabolism [60], everything else being equal, warming should reduce growth and body size [31],[61],[62]. In some regions, warming of extreme cold places could enhance individual body growth [63].	Acidification may reduce skeletogenesis [33],[64] and increase metabolic costs of calcification [32], although some taxa are resistant [65] and some plants may benefit [66] (but see [67]). CO2 can increase in the blood (i.e., hypercapnia) reducing growth [33],[68]–[70].	Hypoxia (reduced oxygen) should reduce growth and body size [71]–[73]. Oxygen concentration also exerts a strong control over calcification rates of corals [74].	Growth and body size should decline with lowered productivity [19],[31],[75]–[79]. Changes in life-history strategies of abyssal macrofauna may be related to changes in surface productivity [80].
Survival and abundance	In some taxa, thermal tolerance thresholds could be surpassed by warming leading to excessive mortality [3],[81]–[83], especially if in interacting with other stressors [29],[84]. Warming thus reduces abundance [83],[85]–[87] and may enhance diseases [88]–[93].	Acidification increases mortality in selected adult [94] and juvenile [95]–[98] marine invertebrates [33] and plants [67]. Abundance can decline among producer species [67] (but see [66],[99]).	Hypoxia causes mortality in most large eukaryote species [23],[71],[84],[100], and anoxia (complete lack of oxygen) could cause extinction in macro- and megafauna [71],[101]–[104]. Hypoxia may enhance dominance by some taxa that are hypoxia tolerant [103],[105],[106] or that are released from ecological interactions [16],[71],[107],[108].	Mortality of benthic invertebrates is generally higher with reductions in food supply [83]. Reduced productivity could reduce abundance [75],[83],[108]–[114] and lead to dominance shifts from large to small taxa [115].
Range and distribution	Warming could cause range shifts poleward and to deeper waters [116]–[119], which in turn could affect the strength of ecological interactions [120], gene flow, and rates of evolution [121]. Warming also reduces habitat suitability for species that do not shift ranges [122].	Reduced calcium carbonate saturation could prevent calcification and growth and thus lead to the disappearance of calcifying species from certain shallow [3],[123] and deep-sea [124] areas.	Some taxa may disappear from hypoxic waters [24],[71],[103],[125]–[129] but others may appear and thrive [24],[125],[128]. Some evidence exists for increased endemism among benthic foraminifera in core regions of oxygen minimum zones [130].	Certain species are unlikely to maintain their distribution in food-limited areas of the seafloor [131].
Species richness	Theory suggests a positive relation between richness and temperature [132]–[135], which is confirmed in several marine studies [54],[117],[136],[137]; although some regions and/or taxa fail to show a relationship [138].	Acidification will likely lead to loss of species [94],[139],[140].	Diversity declines as oxygen declines for protists [16],[23],[101], meiofauna [16], macrofauna, and megafauna [23],[24],[71],[101],[125].	Richness shows a unimodal [83],[112],[114],[131] or no [137],[138] relationship with proxies of food supply. Productivity seasonality may negatively affect diversity [141],[142]. Eutrophication causes diversity decline via hypoxia and anoxia [16].
Functioning	Ecosystem malfunctioning could be extensive if key-stone species are affected [3],[55],[56],[120],[122]. Trophic cascades (e.g., rise of jellyfish) could also occur [105].	Acidification can affect nutrient cycling [140],[143], while reduced calcification can reduce sinking rates and carbon export fluxes to the seafloor via less mineral ballast [144].	Carbon cycling could shift from metazoans to benthic foraminifera [145] and microbiota [20],[145] in suboxic and anoxic zones. Hypoxia can reduce colonization, recovery, and resilience [146].	Reduced food supply can reduce carbon cycling [19],[147],[148], modify food-web structures [114], and cause shifts from macrofaunal- to microbial-dominated nutrient cycling [75],[149],[150].