What’s the Temperature Like Down There?

Wendy Wu ’22

Figure 1: Whales are deep-diving marine mammals and frequently experience large fluctuations in water temperature.

Marine mammals are highly sensitive to temperature, often witnessed migrating to warmer/colder waters depending on their preferences. Research into the thermal habitats of marine mammals has so far been based on surface water temperatures. Stephanie Adamczak, a graduate student at the School of Marine and Atmospheric Sciences at Stony Brook University, sought to investigate the impact of deeper water temperatures on habitat use and seasonal movements, particularly in regards to deep-diving marine mammals. Since temperatures fluctuate greatly from the surface to greater depths, Adamczak suspects that temperature at depth has poorly researched influence over habitat use and that current data may be non-reflective of actual thermal habitats.

From 2008 to 2014, Adamczak and her team followed a pod of 22 short-finned pilot whales—who typically forage from 500-1500 m and enjoy cooler, northern waters in the summer—off Cape Hatteras, North Carolina. This region is marked by the merging of cold, low-salinity waters and warm, high-salinity waters, making it suitable for studying temperature at depth preferences. The scientists monitored the diving behavior of the pilot whales using digital acoustic recording tags (DTAGs). Whales spent 57% of their time at or above 20m, or surface depths, and 7% of their time at deep dives greater than 500m. Because there was lag in the DTAG temperature measurements, an issue common with many marine mammal tagging technologies, this data was not analyzed. Instead, Adamczak referenced annually averaged temperature data from the Met Office Hadley Centre EN4 database. By combining the seasonal and latitudinal data with the data obtained about diving depths, researchers were able to estimate thermal habitats at depth. 

It was found that short-finned pilot whales regularly experience temperature differences around 18℃. Temperature differences between the surface and at depth were particularly varied during spring and summer months. It is clear that surface temperatures are not enough to determine thermal habitats for these deep-diving marine mammals. In fact, short-finned pilot whales are found in waters with temperatures significantly colder than previous research estimates. Incorporating temperature at depth data would give better insight into the actual thermal preferences of this species and thus, insight into methods of monitoring and managing this species. Further research should focus on incorporating diving temperatures and establishing more accurate estimates of thermal habitats for other deep-diving species. Additional data from other whale pods in different locations would strengthen Adamczak’s observations and result in better understanding of whale diving behavior.

Works Cited: 

[1] S. K. Adamczak, et al., The impact of temperature at depth on estimates of thermal habitat for short-finned pilot whales. Marine Mammal Science, (2020). doi: https://doi.org/10.1111/mms.12737

[2] Image retrieved from: https://www.pexels.com/photo/black-and-white-whales-under-water-4666753/

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