Fisheries, low oxygen and climate change: how much do we really know?

Abstract

As a result of long-term climate change, regions of the ocean with low oxygen concentrations are predicted to occur more frequently and persist for longer periods of time in the future. When low levels of oxygen are present, this places additional pressure on marine organisms to meet their metabolic requirements, with implications for growth, feeding and reproduction. Extensive research has been carried out on the effects of acute hypoxia, but far less on long-term chronic effects of low oxygen zones, especially with regard to commercially important fishes and shellfishes. To provide further understanding on how commercial species could be affected, the results of relevant experiments must support population and ecosystem models. This is not easy because individual effects are wide-ranging; for example, studies to date have shown that low oxygen zones can affect predator-prey relationships as some species are able to tolerate low oxygen more than others. Some fishes may move away from areas until oxygen levels return to acceptable levels, while others take advantage of a reduced start response in prey fishes and remain in the area to feed. Sessile or less mobile species such as shellfishes are unable to move out of depleted oxygen zones. Some species can tolerate low oxygen levels for only short periods of time, while others are able to acclimatize. To advance the knowledge-base further, a number of promising technological and modelling-based developments and the role of physiological data within these, are proposed. These include advances in remote telemetry (tagging) and sensor technologies, trait-based analyses to provide insight into how whole assemblages might respond in the future, research into long-term adaptability of species, population and ecosystem modelling techniques and quantification of economic effects. In addition, more detailed oxygen monitoring and projections are required to better understand the likely temporal and local-scale changes in oxygen.

Hypoxic Induced Decrease in Oxygen Consumption in Cuttlefish (Sepia officinalis) Is Associated with Minor Increases in Mantle Octopine but No Changes in Markers of Protein Turnover

“…These geographic areas are at risk of becoming hypoxic because of the increase of nutrients and organic matter into the coastal waters (Van Den Thillart et al, 1994; Grantham et al, 2004; Chan et al, 2008). Hypoxic conditions occur naturally in nature (Ekau et al, 2010); however, there are reports of a global oceanic oxygen decline (Schmidtko et al, 2017), which is becoming a problem for marine biodiversity (Vaquer-Sunyer and Duarte, 2008) and an important environment stressor to marine species (Cosme and Hauschild, 2016; Townhill et al, 2017). Hypoxia is also a potential challenge under intensive aquaculture conditions (Brett, 1979; Delaney and Klesius, 2004; Burt et al, 2013) due to the high density of animals and because of the costs associated with keeping oxygen saturation at normal levels.…”

Emergence of Summertime Hypoxia and Concurrent Carbonate Mineral Suppression in the Central Bohai Sea, China

“…Deoxygenation will reduce species diversity and species richness in marine ecosystems (Breitburg et al, 2018;Wu, 2002). Although certain benthic species can tolerate DO values lower than 63 μmol O 2 /L for several days to weeks (Rabalais et al, 2010;Wu, 2002), many physiological functions of aquatic organisms are seriously affected at this DO level (e.g., Breitburg et al, 2018;Townhill et al, 2017). Some sensitive species are affected even at a DO concentration of higher than this value (e.g., Díaz & Breitburg, 2009;Vaquer-Sunyer & Duarte, 2008;Wu, 2002).…”

Mussel: a potential pollution indicator in the aquatic ecosystem and effect of climate change

“…Up to one third of global carbon dioxide emissions are absorbed by the oceans (Borunda, 2019;Ülker et al, 2018;Townhill et al, 2017). The ocean is a natural sink for carbon dioxide (CO2); however, the increase of anthropogenic emissions is changing the ocean chemistry by lowering the seawater pH, and causing a reduction in the availability of carbonates (CO32-) and biogenic calcium carbonate (CaCO3), a process widely known as ocean acidification (Caldeira and Wickett, 2003;Feely et al, 2009;Gattuso and Hansson, 2011;Gazioğlu and Okutan, 2016).…”