Southern Ocean fish adapting to global climate change

Scientists have identified how the fish in the Southern Ocean are adapting to global climate change specifically the increasing temperatures of the ocean.

A 2021 climate analysis posited that by 2050 some areas of the Antarctic continental shelf will be at least 1 degree Celsius warmer. Researchers from Virginia Tech’s Fralin Biomedical Research Institute at VTC have published a new study in PLOS ONE describing how two species of Antarctic fish – one with hemoglobin in its blood cells and one without – respond to acute thermal stress.

Scientists observed that both species responded to progressive warming with an elaborate array of behavioral maneuvers, including fanning and splaying their fins, breathing at the surface, startle-like behavior, and transient bouts of alternating movement and rest.

For the research researchers examined five specimens of white-blooded blackfin icefish and five red-blooded black rockcod, Notothenia coriiceps, in a climate-controlled shoreline laboratory that circulated, and progressively warmed, saltwater straight from the Southern Ocean. The fishes acclimated to the lab conditions, before being transferred to the experimental tank, where water temperature rose from -1.8 degrees Celsius to 13 degrees, at a rate of 3 degrees per hour. The researchers captured extensive video recordings, allowing them to examine and quantify the fishes’ motility, breathing rate, maneuvers in the tank, and fin movements.

As the water temperature rose, the white-blooded icefish displayed intensive pectoral fin fanning – a behavior previously observed in icefish during egg guarding – that the researchers suggest may help facilitate respiration. By contrast, the red-blooded fish employed complex maneuvers, including pectoral fin fanning and splaying, followed by startle-like C-turns, which may augment gill ventilation.

While the research team observed that stenothermal Antarctic fishes show remarkable capacity to withstand acute thermal stress, they also warn that these vulnerable species still need protection.

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