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Earthquakes – They Affect Marine Life, Too!

 

Earthquakes – They affect marine life, too!

Sperm Whale

Sperm Whale

It seems obvious that earthquakes affect land animals. However, after coming across a National Geographic article on earthquakes and sperm whales, our group became interested in how earthquakes can affect marine megafauna.

Introduction

Abundant evidence exists demonstrating the effects of earthquakes on land animals. Historical evidence from 373B.C. documents that animals such as rats, snakes, and weasels had abandoned the Greek city of Helios days before an earthquake devastated the place. Anecdotal reports throughout hundreds of years detail similar strange behavior before earthquakes even strike: pet owners have long recorded reports of cats and dogs barking, whining, or showing signs of nervousness before a quake. However, it becomes less clear how these earthquakes may affect marine megafauna.

 Background

 

Sperm Whale Eating Squid Animation

Animation of a Sperm Whale Eating a Squid

 

 

         Sperm whales, or Physeter macrocephalus, are a species of marine mammal that can weigh 35 to 45 tons and are typically longer than the average school bus. Sperm whales received their name because they have large quantities of an oily substance called spermaceti in their heads. Although scientists are not completely sure about the purpose of this fluid, some hypothesize that it helps them change their buoyancy as they dive deep for squid and other prey. 

         In November of 2016, a 7.8 magnitude earthquake devastated Kaikoura, New Zealand. Although the number of human casualties was low, it caused complex environmental disturbances. The Kaikoura underwater canyon is one of the few places in the world where you can see sperm whales very close to the shore. The earthquake triggered a series of widespread underwater mudslides in the canyon, causing both powerful currents and changes in water depth relative to sea level. These landslides not only clouded the water, but they also killed or swept away many of the marine invertebrates living in the canyon. These invertebrates are an important source of food for squid and bottom dwelling fish, which are two key prey for male sperm whales. Therefore, scientists hypothesized that the loss and restructuring of marine invertebrates in the Kaikoura canyon would have profound effects on sperm whale feeding patterns. Marine biologist Liz Slooten happened to be studying in the Kaikoura canyon when the earthquake occurred, so she had the chance to directly study the effects of this earthquake. The article emphasizes that such an opportunity is rare in marine research.

 

Kaikoura Canyon

Kaikoura Canyon

 Results of the study

Using directional hydrophones, researchers tuned into sperm whale breathing sounds and found that post earthquake, male sperm whales spent roughly 25 percent longer at the surface to gather oxygen and rest their muscles. Scientists like Liz Slooten and PhD student Marta Guerra reasoned that this increase in surface breathing resulted because the earthquake swept away marine prey, causing the whales to have to dive deeper and longer to find food. According to the study, before the earthquake, sperm whales foraged in the upper parts of the canyon, but afterwards, they dove to deeper regions. Although this change seems disturbing, one positive note of resilience is that a year after the earthquake, the whales returned to their pre-earthquake breathing patterns. 

 Why are these findings significant? 

         If earthquakes are affecting the abundance and spatial variation of marine life, it is important to understand these effects so that governments can implement appropriate catch and fishing quotas to manage these areas post earthquake.

         Overall, it is clear that while these earthquakes may seem to only be affecting small invertebrates, the movement and death of these invertebrates can have profound trophic cascades. These trophic cascades will affect squid and other fish directly and the large sperm whale predators indirectly.

Additionally, while this study found that sperm whale feeding returned to normal after a year, additional studies should attempt to observe multi-year impacts to understand how earthquakes affect marine ecosystems over long periods of time. 

 Our Chosen Article:  

Rapp, J. L. (2020, January). Earthquakes can make it harder for whales to find food, first-ever study says. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/2020/01/earthquakes-sperm-whales-feeding-new-zealand/

Other References

Mott, M. (2003). Can Animals Sense Earthquakes. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/2003/11/animals-sense-earthquakes/

National Geographic. (n.d.). Sperm Whale. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/mammals/s/sperm-whale/

Wagner, E. (2011). The Sperm Whale’s Deadly Call. Smithsonian Magazine. Retrieved from https://www.smithsonianmag.com/science-nature/the-sperm-whales-deadly-call-94653/

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