Description: In the last few decades, numerous studies have investigated the impacts of simulated ocean acidification on marine species and communities, particularly those inhabiting dynamic coastal systems. Despite these research efforts, there are many gaps in our understanding, particularly with respect to physiological mechanisms that lead to pathologies. In this review, we trace how carbonate system disturbances propagate from the coastal environment into marine invertebrates and highlight mechanistic links between these disturbances and organism function. We also point toward several processes related to basic invertebrate biology that are severely understudied and prevent an accurate understanding of how carbonate system dynamics influence organismic homeostasis and fitness-related traits. We recommend that significant research effort be directed to studying cellular phenotypes of invertebrates acclimated or adapted to elevated seawater pCO2 using biochemical and physiological methods.

Description: The deep-sea water column below 200 m is a vast three-dimensional habitat with an enormous but largely unexplored biodiversity (Robison, 2009). Cephalopod mollusks are abundant in the deep sea and are important prey for many kinds of predators. Still, most deep-sea cephalopods have never been observed alive in their natural habitat and their reproductive biology remains poorly documented. In March of 2015, at a depth of 2566 m, we observed a female squid of an undescribed species but likely belonging to the Gonatidae, carrying few but exceptionally large eggs in her arms. This raises questions as to how these and other related animals reproduce in the deep sea, an environment that is generally characterized by darkness, low temperature, reduced oxygen, limited food availability, and low population densities. The authors were conducting dives with deep-sea robots (remotely operated vehicles or ROVs) equipped with cameras in the deep basins of the Gulf of California, to investigate how deep-sea fauna are distributed in relation to the extensive low-oxygen zones in the region (Gilly et al., 2013). The squid (Individual 1, Table 1) we observed with an ROV at 2566 m in the Gulf of California in 2015 was carrying 30–40 large eggs (average maximum diameter 11.2 mm, n = 5; measured eggs were 11.4, 10.4, 11.5, 11.7 and 11 mm maximum diameter) embedded in a small external egg sheet that did not extend beyond the arm tips. The size of the eggs was similar to those of two squid (Individuals 2 and 3, Table 1) that were observed close to the seafloor during earlier expeditions in the same region.