Finding Home: Geomagnetic Migration in Marine Animals – and Human Impacts

Image credit: Tony Hisgett

I find the link between biology and geology endlessly fascinating – how animals (including us humans) are shaped and influenced by the Earth’s physics, and vice versa. Among the many aspects of this co-evolutionary relationship, something I find particularly intriguing is the ability of some species to use geomagnetic navigation. Magnetoreception – the ability to sense a magnetic field – has been observed across a wide range of living beings, from bacteria to cetaceans. However, given that human activity can influence geomagnetic fields, it also concerns me that we are interfering with the ability of other species to navigate their environments.

This blog post is adapted from an essay I wrote as a first-year student of BSc Marine Biology. Although I switched degrees, and therefore never made it past the first year, my fascination with these topics has remained, as has my desire to share that fascination with others.

So first, a short explanation of some of the research. A key hypothesis concerning geomagnetic migration is the concept of imprinting: scientists believe this is what happens when an animal becomes attuned to a specific location on the Earth’s magnetic field. This imprint would explain how marine animals are able to return so precisely to their places of birth after spending time in the vast open ocean. A growing body of research is demonstrating that this hypothesis is an accurate one. For example, because the Earth’s magnetic fields move and vary in intensity, it was hypothesised that if imprinting does occur, changes in the magnetic fields would influence natal homing routes. Data analysis of loggerhead sea turtles on the Florida coast does indeed show that slight changes in the geomagnetic field result in similar changes in nesting density.[1] Likewise, researchers analysing 56 years-worth of fisheries data found that magnetic intensity around Vancouver Island influenced whether sockeye salmon chose a northerly or southerly migratory route back to their spawning site.[2] Both studies suggest that animals migrate towards the geomagnetic signature they have been imprinted with, rather than the exact geographical location. In other words, where these animals nest or spawn is influenced by shifts in the magnetic field.

Main Compass Rose from Carta del Cantino

A variety of biophysical mechanisms that make geomagnetic navigation possible have been proposed. These include the biological presence of magnetite crystals: a magnetically-sensitive mineral which has been found in many species, including in the human brain.[3] Additionally, a study by Vidal-Gadea et al. found that nematodes (microscopic roundworms) have specific neurons which enable geomagnetic orientation. And Hiscock et al. propose that migratory birds are able to navigate the Earth’s magnetic fields due to quantum mechanical spin occurring in proteins called cryptochromes, which are found in the birds’ eyes.

One of the challenges faced by researchers in this field of study is that it requires cross-overs from many disciplines, including geology, biology, physics and, as just mentioned, even quantum mechanics. Another difficulty lies in how we determine the human impact on geomagnetic navigation in marine animals. Research into how human activity affects electromagnetic fields in the oceans is lacking, in part because the mechanisms by which marine animals use this field is itself not fully understood.

However, there is enough evidence to show that further research is much needed. For example, transmission cables from offshore wind farms have been found to alter localised magnetic fields. Although research suggests that the field of influence from wind farms is not far-reaching, there is not yet sufficient evidence to dismiss the potential of negative impact on marine migrations. In fact, some research does show that the presence of transmission cables changes foraging and resting behaviours in some species.[4] Additionally, research at the Mario Zucchelli Station on the Antarctic coast has shown that the station affects the local magnetic field up to a distance of 650 metres below ground,[5] thus demonstrating the extent to which large coastal or offshore structures can influence the magnetic field.

Further to this, research by Gieré highlights the problem of magnetite nanoparticles in atmospheric pollution, raising concerns about the potential of increased sensitivity to electromagnetic fields for humans and other animals. Whilst no research seems to have been carried out to investigate the effects of magnetite pollution on migratory marine animals, the use of magnetite has been proposed by researchers as a possible agent in clearing marine oil spills. Human pollution could have the potential to influence magnetic sensitivity of marine animals via bioaccumulation of magnetite, although there is currently no evidence for this.

When it comes to offshore wind farms, research into the negative impact on marine life may prove both publicly and politically unpopular, given that wind power has become emblematic of the modern environmental movement. Likewise, research into the negative impacts of clearing oil spills with magnetite may seem inconvenient to some. However, it is important that, in our efforts to create more harmonious relationships with our surroundings, we strive to make genuinely environmentally-friendly choices, and not simply content ourselves with solutions that are ideologically or politically appealing.

Earth systems are so complex, in ways that can both fascinate and bewilder us. Understanding how to align ourselves better with them requires humility on our part and a consistent openness to learning more - always learning more.

[1] Brothers, J.R. and Lohmann, K.J. (2015) ‘Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles.’ Current Biology. 25 (3). 392 – 396. [2] Putman, N.F., et al. (2015) ‘Evidence for Geomagnetic Imprinting as a Homing Mechanism in Pacific Salmon.’ Current Biology. 23. 312 – 316. [3] Gieré, R. (2016) ‘Magnetite in the human body: Biogenic vs. anthropogenic.’ Proceedings of the National Academy of Sciences. 113 (43). 11986 – 11987. [4] Hutchison, Zoe L., et al. (2020) 'Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species.' Scientific Reports, 10, 4219. https://www.nature.com/articles/s41598-020-60793-x [5] Armadillo, E., et al. (2012) ‘Impact of Human Activities on the Geomagnetic Field of Antarctica: A High Resolution Aeromagnetic Survey Over Mario Zucchelli Station.’ Environment International. 47. 1 – 7.

References:

Armadillo, E., E. Bozzo, M. Gambetta, and D. Rizzello. ‘Impact of Human Activities on the Geomagnetic Field of Antarctica: A High Resolution Aeromagnetic Survey Over Mario Zucchelli Station.’ Environment International, v. 47 (2012), pp. 1 – 7. https://doi.org/10.1016/j.envint.2012.05.005

Atta, Ayman M., Hamad A. Al-Lohedan, and Sami A. Al-Hussain. ‘Functionalization of Magnetite Nanoparticles as Oil Spill Collector.’ International Journal of Molecular Sciences, v.16, no. 4 (2015), pp. 6911 – 6931. https://www.mdpi.com/1422-0067/16/4/6911

Brothers, J. Roger. and Kenneth J. Lohmann. ‘Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles.’ Current Biology, v. 25, no. 3 (2015), pp. 392 – 396. https://doi.org/10.1016/j.cub.2014.12.035

Gieré, Reto. ‘Magnetite in the human body: Biogenic vs. anthropogenic.’ Proceedings of the National Academy of Sciences, v. 113, no. 43 (2016), pp. 11986 – 11987. https://doi.org/10.1073/pnas.1613349113

Hiscock, H. G., Worster, S., Kattnig, D.R., Steers, C., Jin, Y., Manolopoulos, D. E., Mouritsen, H. and Hore, P. J. (2016) ‘Quantum needle of the avian magnetic compass.’ Proceedings of the National Academy of Sciences.

Hutchison, Zoe L., Andrew B. Gill, Peter Sigray, Haibo He and John W. King. 'Anthropogenic electromagnetic fields (EMF) influence the behaviour of bottom-dwelling marine species.' Scientific Reports, 10, 4219 (2020) https://www.nature.com/articles/s41598-020-60793-x

Kirschvink, J. L., Walker, M. M. and Diebel, C. E. (2001) ‘Magnetite-based magnetoreception.’ Current Opinion in Neurobiology. 11 (4). 462 – 467.

Otremba, Z. and Andrulewicz, E. (2015) ‘Physical Fields During Construction and Operation of Wind Farms by Example of Polish Maritime Areas.’ Polish Maritime Research. 3. 113 –122.

Putman, N.F., Lohmann, K.J., Putman, E.M., Quinn, T.P., Klimley, A.P. and Noakes, D.L.G. (2015) ‘Evidence for Geomagnetic Imprinting as a Homing Mechanism in Pacific Salmon.’ Current Biology. 23. 312 – 316.

Vidal-Gadea, A., Ward, K., Beron, C., Ghorashian, N., Gokce, S., Russell, J., Truong, N., Parikh, A., Gadea, O., Ben-Yakar, A. and Pierce-Shimomura, J. (2015) ‘Magnetosensitive Neurons Mediate Geomagnetic Orientation in Caenorhabditis elegans.’ eLife. DOI:10.7554/eLife.07493 3