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The Race to Decode Secrets of Antarctica’s Most Important Ocean Animal

The future of krill – and all the marine wildlife that feed on them – is uncertain in the changing Southern Ocean. Krill biologist Stephen Nicol says they may be adaptable to climate change, but new technologies need to be deployed to study their enigmatic behavior.

Written by Stephen Nicol Published on Read time Approx. 9 minutes
Krill. Photo12/UIG via Getty Images

Editor’s note: This piece is adapted from Stephen Nicol’s recent book “The Curious Life of Krill.” In the book, Nicol, a marine biologist and adjunct professor at the University of Tasmania in Australia, describes his fascination with these often-overlooked swimming crustaceans, developed over his long science career studying them all over the world, but particularly around Antarctica – where they serve as a crucial food source for whales, penguins, seals and other animals.

Antarctic krill are among the world’s most abundant animals and have a critical role in the Antarctic ecosystem, but their environment is changing rapidly. There is a tendency to view environmental change as a threatening process, but for adaptable animals, like krill, it may end up being challenging rather than life-threatening.

Over millennia krill have thrived, rather than being threatened by every change in their challenging physical and biological world, but how they have done this is yet unknown.

Their history in the Antarctic is opaque. In a confounding quirk of krill, we have been unable to find any fossil record for any species of krill that would assist us in learning how they have reacted to historical changes. We know that Antarctic krill probably emerged about 20 million years ago, but how the population responded to the tumultuous changes that have occurred since then is a mystery. We do know that krill are remarkably successful, so they must have considerable powers of adaptation, and this gives me some hope for their future.

The main problem, however, is that so many changes are now happening rapidly and simultaneously. Animals can adapt to slow change over evolutionary periods, and animals with short life spans can adapt the fastest. Unfortunately, because krill are long-lived, their ability to adapt to rapid change might be limited.

But they do have one weapon for avoiding the worst element of a changing ocean – behavior. By reacting to an unfavorable environment krill can alter their distribution and stay away from areas that are threatening. This avoidance behavior is probably only limited, but coupled with slow physiological adaptation to change it may allow krill to survive even in areas where their doom has been predicted.

There is no fossil record for krill, making it hard to know how they reacted to past environmental change. (Stephen Nicol/AAD)

Krill behavior is one of the great unknowns, but it is rarely considered in modeling studies that are used to predict the response of krill to climate change. Future studies examining the fate of the krill population when faced by a warming, more acidic ocean with less sea ice will need to incorporate a realistic assessment of their behavioral abilities. There are currently few data that could be used to do this. Those who are brave enough to try to predict the effect of a warming ocean on the krill population have a fiendishly complicated task.

It has usually been assumed that krill are merely being acted upon by their physical environment. We know that they migrate both vertically and horizontally, and there is some evidence that when the surface waters are too warm, they can spend more time in the cooler deep water. So krill are unlikely to be passive players in the game of global warming.

This is not to assert that there are not immense environmental challenges to the survival of krill, and by extension, the Southern Ocean ecosystem. We know that changes to critical aspects of the Southern Ocean are occurring right now and have in the recent past. It is uncertain how krill can cope with these changes, and nor is it immediately evident what we can do at the local level to ensure the conservation of krill.

For the last century the tools available to study krill have been crude and our access to their environment has been limited. Because of developments in fields as diverse as electronics and molecular biology, the next few decades will see a renaissance in research into krill and other marine organisms. We will never achieve the degree of certainty that physicists aspire to, but with careful study and the application of new technology, we will be able to make great strides in marine biology.

A humpback whale tail near Palmer Station, Antarctica. Humpbacks will dive for 15 to 20 minutes, feeding mostly on krill. (Jeff Keller, National Science Foundation)

Simple acts, such as capturing images of krill on underwater video, have changed the way in which we view the vertical range of krill in the ocean and have given new insights into their behavior. Satellites, aircraft, drones and autonomous underwater vehicles can now be used to map krill populations and follow their movements, but we still have difficulty keeping track of individual krill.

One of the most significant developments in studying the biology of larger animals, both on land and in the ocean, has been the development of equipment that allows researchers to track individuals in space and time. A range of miniaturized sensors has been developed that provides information on the location of an animal, how fast it is moving, what depth it is at and what it is feeding on, as well as providing the temperature and salinity of the ocean. Such instrumentation has revolutionized our understanding of the behavior of large marine animals.

Our understanding of how krill predators operate in their natural environment has increased dramatically over the last two decades; why has this revolution not yet flowed on to krill? There are two main reasons.

First, diving mammals and birds must visit the surface of the ocean to breathe, and flying birds spend most of their lives above the waves. This means that signals from instruments that have been attached to them can be relayed to satellites. Second, even though miniaturization has developed at an amazing pace, we are not yet at the stage where we can attach a sensor to an aquatic animal the size of a krill. I suspect that with the current size of most sensors we would find that a krill, loaded down with an electronic backpack and released into the ocean, would head straight to the ocean floor and lie there until some benthic predator made a meal of it.

A research team analyzes krill at Palmer Station in Antarctica. (Keri Nelson, National Science Foundation)

For us to benefit from the electronics revolution we will need much smaller instruments and an efficient way of sending information through water. I am sure these developments will happen soon, and it will probably transform our science the way that satellite tracking has changed the way we think of vertebrate predators.

Back in the laboratory, it is the genetic revolution that holds great promise for the future. Two decades ago there was little conception of the revolution that was about to be unleashed through developments in the field of molecular biology. This area of research is developing so fast that it has outstripped the ability of “normal” biologists (like me) to be able to keep up and understand even what tools are available. Luckily, a younger generation of scientists are now beginning to apply their skills and knowledge to many of the intriguing issues surrounding the biology of krill and the management of the krill fishery.

Molecular techniques are being applied to individual krill and to populations of krill, but, predictably, there are problems thrown up by the enigmatic creatures themselves. A significant obstacle for geneticists is the huge genome of krill – 12 times the size of our own. This means that, even in the era of rapid and cheap genome sequencing, it will take a few more years of technical development before the krill genome can be sequenced and we can begin to unravel its secrets. But molecular techniques have already been used to determine what krill eat by looking at the DNA in their guts and how the timing of the krill life cycle is regulated through an internal clock. Perhaps the most intriguing development is in the area of “environmental DNA” where detection of krill genetic material in seawater may provide information on the thorny problem of assessing distribution and abundance of krill. Given the pace of the molecular revolution, it is impossible to predict what might happen next.

Antarctic krill play a critical role in the Southern Ocean ecosystem. (Stephen Nicol/AAD)

The key to applying all these new methodologies to answer the critical questions concerning krill is to ensure that our key questions are widely appreciated so that those with the appropriate skills are attracted to the scientific challenge of answering them. But it is not enough to merely apply new methods; we must also develop new concepts and a new language to describe the world that our technology opens for us. There is a subtle and overlooked interaction between the techniques we use to study life in the ocean and the language we use to describe its inhabitants and their interactions. Victorian terms such as zooplankton need to fade away as we discard Victorian tools like the plankton net. The next few decades will be an exciting time to be a krill researcher and will change forever the way we view krill and their environment – I hope I can be around to observe this revolution.

As we gain more insights and observations from using new technology our knowledge of krill and their environment will improve immeasurably. In parallel, mathematical models will be developing as computing power increases and as clever mathematics percolates its way into the field of ecology. The combination of improved observations, better biological understanding and enhanced modeling power will mean that in the decades to come we will be in a far better position to make some meaningful predictions about the future state of the Southern Ocean ecosystem and of the animal that is at its center.

Krill behavior is still a mystery, but scientists are gaining more tools to study them. (Wolfgang Kaehler/LightRocket via Getty Images)

In turn, these predictions will allow us to make more considered decisions about management of activities in the Antarctic region, including fishing. This does not mean that we should wait until our knowledge and our methods are perfect (they never will be) before acting. Rather it suggests that we should exercise extreme caution now, and only when we have greater certainty can we relax our guard somewhat.

The conservation of krill is critical for the future of the Southern Ocean ecosystem. Such a statement assumes that there is consensus on the qualities of the ecosystem that should be conserved. In a changing environment, and with limited data, it is difficult to know which form of the ecosystem should be the preferred baseline and how to ensure that human actions drive the system toward this preferred state. There is an oft-repeated myth that the Antarctic region is pristine – we know that there has been a 200-year history of extreme exploitation. The current ecosystem is quite different, physically and biologically, from that encountered by the first humans who explored the Southern Ocean nearly 300 years ago.

With the catalogue of environmental changes already under way I fear that the political process will be unable to respond fast enough, and we may all sit on the sidelines while the planet’s ocean ecosystems change. The best that we can do is to develop our ability to monitor the change and improve our capability to predict the future state of the ecosystem and spread the message widely about the state of the environment. Better information is our best weapon in the fight to ensure the conservation of the Antarctic region.

Krill can alter their behavior in response to threats. (Stephen Nicol/AAD)

Despite my reservations, I remain cautiously optimistic for the future of krill in the Antarctic. Krill is an extraordinary animal. Its abundance, size, nutritional content and swarming behavior have ensured its critical ecological importance. Its longevity, physiological plasticity and behavior have all contributed to its major role in many of the ocean’s biological, chemical and physical cycles.

Yet, despite these aspects, all of which contribute to resilience, we must be extremely cautious when scoping out potential futures for the krill population. Some of the planet’s most abundant species, such as the passenger pigeon, were exterminated over very short periods of time, so mere abundance alone does not guarantee survival against a backdrop of natural and human-induced changes.

We are now at a critical point in history for krill – our actions now could spell doom for an entire ecosystem, or we could make some well-informed choices that enhance the conservation of krill and thus the entire Antarctic ecosystem.

Adapted from “The Curious Life of Krill” by Stephen Nicol; Copyright © 2018 by the author. Reproduced by permission of Island Press, Washington, D.C.

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