Antarctic seas host a surprising mix of lifeforms – and now we can map them



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In contrast to common perceptions, Antarctic seafloor communities are highly diverse. This image shows a deep East Antarctic reef with plenty of corals, sponges and brittlestars. Can you spot the octopus?
Australian Antarctic Division

Jan Jansen, University of Tasmania; Craig Johnson, University of Tasmania, and Nicole Hill, University of Tasmania

What sort of life do you associate with Antarctica? Penguins? Seals? Whales?

Actually, life in Antarctic waters is much broader than this, and surprisingly diverse. Hidden under the cover of sea-ice for most of the year, and living in cold water near the seafloor, are thousands of unique and colourful species.

A diverse seafloor community living under the ice near Casey station in East Antarctica.

Our research has generated new techniques to map where these species live, and predict how this might change in the future.

Biodiversity is nature’s most valuable resource, and mapping how it is distributed is a crucial step in conserving life and ecosystems in Antarctica.




Read more:
Explainer: what is biodiversity and why does it matter?


Surprises on the seafloor

The ocean surrounding the Antarctic continent is an unusual place. Here, water temperatures reach below freezing-point, and the ocean is covered in ice for most of the year.

While commonly known for its massive icebergs and iconic penguins, Antarctica’s best-kept secret lies on the seafloor far below the ocean surface. In this remote and isolated environment, a unique and diverse community of animals has evolved, half of which aren’t found anywhere else on the planet.

These solitary sea squirts stand up to half a metre tall at 220m depth in the dark, cold waters of East-Antarctica. Images such as this one were taken with cameras towed behind the Australian Icebreaker Aurora Australis.
Australian Antarctic Division

Colourful corals and sponges cover the seafloor, where rocks provide hard substrate for attachment. These creatures filter the water for microscopic algae that sink from the ocean surface during the highly productive summer season between December and March.

In turn, these habitat-forming animals provide the structure for all sorts of mobile animals, such as featherstars, seastars, crustaceans, sea spiders and giant isopods (marine equivalents of “slaters” or “woodlice”).

The Antarctic seafloor is also home to a unique group of fish that have evolved proteins to stop their blood from freezing.

Most Antarctic fish have evolved ‘anti-freeze blood’ allowing them to survive in water temperature below zero degrees C.
Australian Antarctic Division

Mapping biodiversity is hard

Biodiversity is a term that describes the variety of all life forms on Earth. The unprecedented rate of biodiversity loss is one of the biggest challenges of our time. And despite its remoteness, Antarctica’s biodiversity is not protected from human impact through climate change, pollution and fisheries.




Read more:
It’s funny to name species after celebrities, but there’s a serious side too


Although scientists have broadly known about Antarctica’s unique marine biodiversity for some time, we still lack knowledge of where each species lives and where important hotspots of biodiversity are located. This is an issue because it hinders us from understanding how the ecosystem functions – and makes it hard to assess potential threats.

Why don’t we know more about the distribution of Antarctic marine species? Primarily, because sampling at the seafloor a few thousand metres below the surface is difficult and expensive, and the Antarctic continental shelf is vast and remote. It usually takes the Australian Icebreaker Aurora Australis ten days to reach the icy continent.

A selection of the diverse and colourful species found on the Antarctic seafloor.
Huw Griffiths/British Antarctic Survey

To make the most of the sparse and patchy biological data that we do have, in our research we take advantage of the fact that species usually have a set of preferred environmental conditions. We use the species’ relationship with their environment to build statistical models that predict where species are most likely to occur.

This allows us to map their distribution in places where we have no biological samples and only environmental data. Critically, until now important environmental factors that influence the distribution of seafloor species have been missing.




Read more:
Antarctica has lost 3 trillion tonnes of ice in 25 years. Time is running out for the frozen continent


Using predictions to make a map

In a recent study, we were able to predictively map how much food from the ocean-surface was available for consumption by corals, sponges and other suspension feeders at the seafloor.

The science behind linking food-particles from the ocean surface to the biodiversity of Antarctic seafloor fauna. Satellites (1) can detect the amount of algae at the ocean-surface. Algae-production is particularly high in ice-free areas (2) compared to under the sea-ice (3). Algae sink from the surface (4) and reach the seafloor. Where ocean-currents are high (5), many corals feed from the suspended particles. In areas with slow currents (6), particles settle onto the seafloor and feed deposit-feeding animals such as seacucumbers.
Jansen et al. (2018), Nature Ecology & Evolution 2, 71-80.

Although biological samples are still scarce, this allowed us to map the distribution of seafloor biodiversity in a region in East Antarctica with high accuracy.

Further, estimates of how and where the supply of food increased after the tip of a massive glacier broke off and changed ocean conditions in the region allowed us to predict where abundances of habitat forming fauna such as corals and sponges will increase in the future.

Colourful and diverse communities are also found living in shallow waters.
Australian Antarctic Division

Antarctica is one of the few regions where the total biomass of seafloor animals is likely to increase in the future. Retreating ice-shelves increase the amount of suitable habitat available and allow more food to reach the seafloor.

For the first time in history, we now have the information, computational power and research capacity to map the distribution of life on the entire continental shelf around Antarctica, identify previously unknown hotspots of biodiversity, and assess how the unique biodiversity of the Antarctic will change into the future.


The Conversation


Read more:
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Jan Jansen, Quantitative Marine Ecologist, University of Tasmania; Craig Johnson, Professor, University of Tasmania, and Nicole Hill, Research fellow, University of Tasmania

This article was originally published on The Conversation. Read the original article.

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Drought on the Murray River harms ocean life too



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The mouth of the Murray River delivers vital nutrients to marine life in the ocean beyond.
SA Water, Author provided

Hannah Auricht, University of Adelaide and Kenneth Clarke, University of Adelaide

Drought in the Murray River doesn’t just affect the river itself – it also affects the ecosystems that live in the ocean beyond.

In a study published in Marine and Freshwater Research today, we found that the very low flows in the river over the past decade reduced the abundance of microscopic marine plants called phytoplankton, which are ultimately the base of all marine food webs.

This shows that the health of the Murray River has a much bigger influence on the marine environment than we previously realised. With climate change poised to make droughts more frequent and severe in the river, it will be crucial to monitor the health not just of freshwater species, but of the local marine ones too.


Read more: Is the Murray-Darling Basin Plan broken?


Phytoplankton depend on nutrients, which are often delivered to the ocean by rivers. In turn, these tiny plants are a source of food for almost all marine ecosystems. Worldwide, they are responsible for half the production of organic matter on the planet.

In South Australia, a dry period dubbed the Millennium Drought (2001 to 2010) and overallocation of water resources (primarily for agriculture) meant that very little water was delivered from the Murray Mouth to the coastal ocean. Between 2007 and 2010, no water was discharged at all. The water in the river’s lower reaches became much saltier and cloudier.

We used historical flow records and satellite imagery, taken between early 2002 and late 2016, to figure out how much phytoplankton and other organic matter were in the coastal ocean each month. We broke up the area into incremental zones, venturing up to 130km from the river mouth.

We found that during and after high-flow events, Murray River discharge resulted in a huge increase in phytoplankton concentrations – as far as 60km beyond the river’s mouth. Surprisingly, before our research it wasn’t known that the river played such an important role in stimulating phytoplankton growth over such a large area.

The mouth of the Murray River, where sometimes no water flows into the ocean at all.
CSIRO/Wikimedia Commons, CC BY

Armed with an understanding of how river flows influenced phytoplankton growth, we used historic flow records to estimate phytoplankton concentrations back to 1962. Our results showed that large flows used to occur more often and in greater volumes, and consequently that phytoplankton populations would have gone through more frequent and larger booms.

This in turn would have benefited all of the species that ultimately depend on phytoplankton for food, either directly or indirectly. This food web encompasses almost the whole marine ecosystem.

The past affects the future

Water resource management has greatly altered the volume and timing of freshwater discharges from the Murray. The ocean beyond the Murray mouth now receives small and infrequent deliveries of freshwater.

Rainfall and streamflow are decreasing in this already variable region, while temperatures are rising. This means that South Australia is likely to experience more severe and more frequent droughts, which will cause flows from the Murray mouth to decline still further, ultimately reducing phytoplankton abundance.

Previous research had already established the links between river outflows, phytoplankton and health of marine environments and species. But as far as we can tell, no other research has looked at exactly how extended periods of no or low river outflows affect marine ecosystems. This makes it difficult to predict how these systems will respond to climate change.

We believe that reduced Murray River outflows and reduced phytoplankton concentrations would likely have also placed strain on local mulloway fish and Goolwa cockle populations. Juvenile mulloway use river outflows as habitat and environmental cues, and cockles feed on organic material in the water.


Read more: ‘Tax returns for water’: how satellite-audited statements can save the Murray-Darling


This is why it is so important that the management of the Murray River doesn’t just stop at the river’s mouth, but continues into the ocean beyond. Current plans are focused on restoring flows to support the riparian and wetland ecosystems of the Murray as well as the Lower Lakes and Coorong.

But there has been little recognition of the role of river outflows on the marine environment – let alone in management. Although we might not always think about it, the marine environment is really the end of the river system, and part of a larger global cycle. It would therefore be beneficial if plans extend to monitor the marine ecosystem’s response, both at broad and fine scales, to varying flow events.

The ConversationIt would seem the time is past ripe to call for greater research and consideration on this matter, so that we don’t do further damage to what is actually still a part of the Murray River system, and can improve measures to protect the marine environment.

Hannah Auricht, PhD candidate, University of Adelaide and Kenneth Clarke, Researcher, School of Biological Sciences, University of Adelaide

This article was originally published on The Conversation. Read the original article.

Citizen scientist scuba divers shed light on the impact of warming oceans on marine life



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A volunteer diver surveys marine life at Lord Howe Island.
Rick Stuart-Smith/Reef Life Survey, Author provided

Madeleine De Gabriele, The Conversation

Rising ocean temperatures may result in worldwide change for shallow reef ecosystems, according to research published yesterday in Science Advances.

The study, based on thousands of surveys carried out by volunteer scuba divers, gives new insights into the relationship of fish numbers to water temperatures – suggesting that warmer oceans may drive fish to significantly expand their habitat, displacing other sea creatures.

Citizen science

The study draws from Reef Life Survey, a 10-year citizen science project that trains volunteer scuba divers to survey marine plants and animals. Over the past ten years, more than 200 divers have surveyed 2,406 ocean sites in 44 countries, creating a uniquely comprehensive data set on ocean life.

Reef Life Survey takes volunteers on surveying expeditions at hard-to-reach coral reefs around the world.
Rick Stuart-Smith/Reef Life Survey, Author provided

Lead author Professor Graham Edgar, who founded Reef Life Survey, said the unprecedented scope of their survey allowed them to investigate global patterns in marine life. The abundance of life in warm regions (such as tropical rainforests and coral reefs) has long intrigued naturalists. At least 30 theories have been put forward, but most studies have been based on relatively limited surveys restricted to a single continent or group of species.

By tapping into the recreational scuba diving community, Reef Life Survey has vastly increased the amount of information researchers have to work with. Professor Edgar and his colleagues provide one-on-one training to volunteers, teaching them how to carry out comprehensive scans of plants and animals in specific areas.

Dr Adriana Vergés, a researcher at the University of New South Wales specialising in the impact of climate change on ocean ecosystems, said that the Reef Life Survey has already substantially improved our understanding of the marine environment.

“For example, Reef Life Survey data has greatly contributed to our understanding of the factors that determine the effectiveness of effectiveness of marine-protected areas worldwide. The team have made all their data publicly available and more and more research is increasingly making use of it to answer research questions,” she said.

Some of the divers have been working with Reef Life Survey for a decade, although others participate when they can. One volunteer, according to Professor Edgar, was so inspired by the project that he began a doctorate in marine biology (he graduated this year).

There’s a strong link between fish numbers and water warmth, which means warming oceans are likely to change global fish distribution.
Rick Stuart-Smith/Reef Life Survey, Author provided

Warming oceans means fish on the move

One of the important insights delivered by the Reef Life Survey datatbase is the relationship between water temperature and the ratio of fish to invertebrates in an ecosystem. Essentially, the warmer the water, the more fish. Conversely, colder waters contain more invertebrates like lobster, crabs and shrimp.

Professor Stewart Frusher, director of the Centre for Marine Socioecology at the University of Tasmania (and a former colleague of Professor Edgar) told The Conversation that he believes we will see wide-scale changes in fish distribution as climate change warms the oceans.

“Species are moving into either deeper water or towards the poles. We also know that not all species are moving at the same rate, and thus new mixtures of ecosystems will occur, with the fast-moving species of one ecosystem mixing with the slower moving of another,” he said.

As species migrate or expand into newly warmed waters, according to Professor Frusher, they will compete with and prey on the species already living in that area. And while it’s uncertain exactly how disruptive this will be, we do know that small ecosystem changes can rapidly lead to larger-scale impacts.

In order to predict and manage these global changes, scientists need reliable and detailed world-wide data. Professor Frusher said that, with research funding declining, scientists do not have the resources to monitor at the scales required.

The Conversation“Well-developed citizen science programs fill an important niche for improving our understanding of how the earth is responding to change,” he said.

Madeleine De Gabriele, Deputy Editor: Energy + Environment, The Conversation

This article was originally published on The Conversation. Read the original article.

Warming seas will set marine life on the move, with some good news among the bad


David Schoeman, University of the Sunshine Coast and Jorge García Molinos, Scottish Association for Marine Science

How will climate change affect life in the oceans? In research to be published in Nature Climate Change* we, among several other authors, show that the answer is likely good and bad.

Our study models how species might move in response to different future climate scenarios. The good news is that overall, thanks to species migrations, most places will end up with greater numbers of species. According to our models, climate change is unlikely to directly cause extinction through warming waters for most species, except for those that can’t move or have very narrow thermal tolerances.

The bad news is that there are a few very special places that will lose species – particularly the spectacular ocean ecosystems of what’s known as the Coral Triangle, the epicentre of global marine biodiversity.

First, the good news

As ocean temperatures increase, marine life will likely move towards the poles – animals and plants will expand their ranges. We can already see this happening. In Australia, tropical species of fish are turning up in northern New South Wales.

We wanted to know how this would affect the overall numbers of animals and plants in the oceans – marine biodiversity – and the distinctive communities they comprise. While many things affect where marine life lives – habitat, competition, salinity – most species are affected fundamentally by temperature.

Using temperature to find out where species might move allowed us to look at an unprecedented number of species – nearly 13,000. These included animals and plants as diverse as fish, corals, jellies, snails, clams, crabs, shrimps and seaweeds.

We looked at two different climate scenarios, business as usual (known as RCP8.5) leading to warming of around 2.5ºC by 2100, and a scenario with medium mitigation (RCP4.5) leading to warming of around 1ºC over the same period.

Our model shows how fast different temperature zones will move and to where, using a measure known as “climate velocity”. This is a good way of predicting where species could move because it traces pathways connected by climate.

We should emphasise that our study shows where species could move. Our projections don’t necessarily mean that they will move, nor that they will successfully establish themselves at the locations where they arrive. That depends on a variety of factors, including their specific habitat requirements and how species interact with each other. But studies of invasive species suggest that species that can move will tend to do so.

Overall we found that biodiversity of the oceans will likely increase at local scales. As a result, we anticipate that marine ecosystems will become more similar. For instance, today on the east Australian coast, the types of species found along the central Queensland coast are quite different from those found in central New South Wales. As sea temperatures warm, we expect those boundaries to gradually break down, leading to what we call a “smearing” of biodiversity.

Bad news for the tropics

There are several theories as to why there are so many species in the tropics, and especially the Coral Triangle. Irrespective, we know that this area supports over 500 species of reef-forming corals, together with a massive diversity of fish, including whale sharks, and six of the seven extant species of sea turtles; it is also visited by many species of whales and dolphins. This concentration of marine biodiversity contributes significantly to livelihoods of the region’s 120 million or so human inhabitants.

Species living in tropical seas already live close to their thermal optimum. As temperatures increase, they will exceed the upper thermal limits of some species. When this happens, some species will adapt, for instance by seeking out micro-refuges, such as small patches of cool water caused by upwelling, or they might resort to living in deeper waters, if the water is clear enough.

But in the long term, most species will need to move. The reason we expect marine biodiversity to decrease in the tropics with warming is that there is no place warmer to act as a source of new species to replace those species moving out.

More than 5,000 of the 13,000 species we looked at in our study are found in the coral triangle. According to our projections, approximately 500 to 1,000 of these species will leave the region thanks to warming waters under RCP4.5 and RCP8.5, respectively.

What can we do?

Our modelling shows that the loss of marine life is strongly related to how much we mitigate climate change.

Even if we take only intermediate levels of action (under scenario RCP4.5), we can minimise the damage. But we can’t eliminate it entirely: under the emission-stabilisation RCP4.5 scenario we anticipate that the Coral Triangle will lose roughly half as many species as under the business-as-usual RCP8.5 scenario.

We can also look at how we manage the world’s oceans. Some regions, such as the northeast Atlantic and eastern Mediterranean, have seen greater impacts from people than others, and some of these overlap with regions likely to be affected by climate change.

Where there is overlap, we can look at alleviating the damage caused by people, such as pollution of coastal waters, or minimising the pressure on key species, for example by reducing fishing pressure on them.

In other areas, such as the poles, there is low human impact, but we project substantial changes in biodiversity. From a conservation perspective, we want representative sections of these areas to remain free from additional human pressure, for instance by using regulation to control future development.

And because climate change doesn’t respect national boundaries, all of these efforts will require international cooperation.

Only in that way will we ensure the seas remain rich and healthy in the future.

We acknowledge the contributions of all co-authors: Jorge Garcia Molinos, Benjamin S. Halpern, David S. Schoeman, Christopher J. Brown, Wolfgang Kiessling, Pippa J. Moore, John M. Pandolfi, Elvira S. Poloczanska, Anthony J. Richardson and Michael T. Burrows

*Update August 25: the paper on which this article is based has not yet been published. The article will be updated when the link is available.

The Conversation

David Schoeman is Associate professor, Biostatistics at University of the Sunshine Coast and Jorge García Molinos is Research Associate Climate Change Ecology at Scottish Association for Marine Science

This article was originally published on The Conversation. Read the original article.