ECOSYSTEMS – AN ANTARCTIC CASE STUDY
LESSON 3 KRILL AS A KEYSTONE SPECIES (A CASE STUDY) LESSON 3 : KRILL AS A KEYSTONE SPECIES (A CASE STUDY)
LESSON OBJECTIVES
Understand how organisms affect, and are affected by, their environment Interpret observations and data, including identifying patterns and using observations, measurements and data to draw conclusions Identify further questions arising from the result
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WHY ARE KRILL IMPORTANT?
Many people consider krill to be one of the most important species in Antarctica.
Why do you think that is?
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YOUR TURN!
Krill are considered to be one of the most important species in the Antarctic!
Why is this?
On your cards you will find 6 facts about krill.
Read the facts and discuss as a group (of 3 or 4).
Order the facts from the most important reason to the least important to help explain why krill are important in Antarctic ecosystems.
Be prepared to discuss your reasons (remember, there are no right or wrong answers in this activity, only ideas with explanations).
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WHY ARE KRILL IMPORTANT?
Phytoplankton are the main producers in the Antarctic. However, not many species can eat phytoplankton because they are so small. Krill have an excellent design for eating phytoplankton. During the summer they eat phytoplankton and during the winter they eat the algae under the sea ice.
Because krill are relatively large, they are a suitable size for other Antarctic animals (e.g. whales, seals, penguins) to eat them. Consequently, krill is the primary consumer in nearly all food chains in the Antarctic. Imagine if krill disappeared, or krill numbers declined. What would happen to other species in the food chains and food webs?
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KRILL AS A KEYSTONE SPECIES
If krill disappeared from the Antarctic ecosystem, it would have a dramatic, negative impact on nearly all Antarctic species, especially on large Antarctic animals such as whales, seals and penguins.
When one species is so important to all the others in the ecosystem, it is know as a KEYSTONE SPECIES
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WHAT IS A KEYSTONE SPECIES?
Watch how an arch with a keystone (or capstone) is made. The keystone of an arch is vital to keep the arch supported and stable. The keystone species within an ecosystem is fundamental to keeping the ecosystem supported and stable. The keystone species helps keep organisms within an ecosystem in balance. Scientists monitor keystone species carefully because of the large knock-on impacts to many other species if there are significant changes in population size.
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SEA OTTER - A KEYSTONE SPECIES EXAMPLE
Sea otters are a keystone species in the kelp forest habitat, an ecosystem home to hundreds of species from sea stars to sharks. Sea otters eat sea urchins preventing overpopulation of sea urchins, which would overwhelm and destroy the ecosystem.
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GRAY WOLF – A KEYSTONE SPECIES EXAMPLE
The gray wolf of Yellowstone National Park, USA was a keystone species. It was an apex predator and helped to keep elk, bison, rabbit and bird populations in balance. When the US government formed the National Park, they eradicated the wolves as they were worried about the wolves’ impact on livestock herds. Due to a lack of an apex predator, elk numbers dramatically increased leading to overgrazing and consequent soil and river bank erosion. Starting in the 1990s, gray wolves are being slowly reintroduced and this has had positive impact on many species populations. © John Marriott
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KRILL – A KEYSTONE SPECIES EXAMPLE
Krill play a major role in the transfer of energy in Antarctic food chains. They are the primary producers within most Antarctic food chains. Therefore, almost all large Antarctic animals are reliant on krill.
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KEYSTONE SPECIES – A DEFINITION
A keystone species is a species which plays a critical role in maintaining the structure and balance of an ecosystem. It affects many other organisms and helps to determine the types and numbers of various other species in the ecosystem.
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GRAY WOLVES OF YELLOWSTONE NATIONAL PARK
Scientists like to keep a close eye on wolf numbers and how they interact with other species (mainly their prey) because they are keystone species. By recording wolf numbers each year they can better understand changes within the ecosystem and predict changes in the future.
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HOW DO SCIENTISTS KNOW?
In Yellowstone National Park, scientist monitor gray wolf numbers and their wolf-prey relationships (what they eat). They do this by: Using GPS collars to follow packs Counting pups in dens during Spring Observations – over 13, 000 volunteer hours in 2016
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HOW DO SCIENTISTS KNOW?
Yellowstone National Park is very large (over 3400 square miles) which means it needs a lot of volunteers to help make observations of wolf numbers. It is on land (USA) and is very accessible. Wolf numbers are relatively low (less than 200). Wolves are territorial (although these territories can be quite large). All this means, it is comparatively easy to collect information on gray wolves and their relationships within the ecosystem.
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GRAY WOLVES VS KRILL
Both are keystone species Scientists have detailed information on gray wolves in How do you think scientists collect Yellowstone National Park, right down to the number of data on krill? cubs born each year. What difficulties might they have? Scientists can use this data to carefully monitor the ecosystems within Yellowstone National Park
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WHY IS IT DIFFICULT TO COLLECT DATA ON KRILL?
Antarctica is huge (over 5.4 million square miles. It is very remote – the nearest country is Chile, approximately 1000 km away. It has a very hostile environment – the average temperature is -10 degrees Celsius. The Southern Ocean – with high winds, storms and icebergs, the Southern Ocean is one of the most inhospitable oceans of the world.
ANTARCTICA
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WHY IS IT DIFFICULT TO COLLECT DATA ON KRILL?
Krill are quite small (6 cm long). They live in the sea so it is not always easy to access them. They form blooms but where these bloom can be found is unpredictable and the Southern Ocean is very large. The blooms are very large (millions of krill) so you cannot count individuals.
© Andrea Izzotti / Thinkstock
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HOW DO SCIENTISTS COLLECT DATA ON KRILL?
POLAR RESEARCH BOATS Scientists can use specialised polar research vessels. These are specially designed to be able to break through the ice formed on the surface of the ocean. They have to be able to cope with extreme temperatures and huge storms. They are often slow. They are very expensive to operate.
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HOW DO SCIENTISTS COLLECT DATA ON KRILL?
DRONES New technology is helping develop research techniques all the time. Drone technology is currently in use to help track and research many animals. Flying drones are too delicate to survive the storms of the Southern Ocean.
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SAILDRONE
Saildrone is a type of drone, which sails. It is designed like a boat, steers like a boat and is powered by the wind like a boat. It uses wind energy to move. It uses solar energy to power all its data sensors. This makes it perfect for the Southern Ocean.
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SAILDRONE
Unlike a research vessel, there are no people on board which makes Saildrone cheaper and safer. It is also run solely on renewable energy (wind and solar). So it doesn’t use fossil fuels and has a very low Carbon footprint. It contains lots of data sensors so it can collect a range of data and send that back via satellite to data analysts anywhere in the world.
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SAILDRONE – HOW DOES IT HELP COUNT KRILL?
An echo sounder is used to locate krill blooms (large groups of krill). It works by transmitting a sound. This sound travels in waves and is reflected back when it hits something such as rocks, fish, whales or krill. Scientists learn to recognise the different patterns that different things in the oceans make. This is the main way scientists measure krill biomass in the Southern Ocean.
Image from http://sciencenordic.com/sounding-out-marine-life
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ECHOSOUNDER IMAGES
Data from an Krill Density echosounder can then be used to calculate the size of krill blooms and their KrillDensity biomass (how much (m) Depth krill there is by weight).
Latitude (S) https://docplayer.me/14835148-Vill-etter-krill-pa-ekspedisjon-med-g-o-sars-til-sorishavet.html (page 131 of the booklet in the link)
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INTERPRETING DATA
Data that is collected can be looked at in a variety of ways.
Comparing data over time e.g. years, seasons
Comparing data with abiotic factors (environmental factors such as temperature)
Comparing data with biotic factors (e.g. other animal population sizes)
The aim is to have enough data to try and spot patterns and also identify reasons for connections or changes.
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LOOKING AT DATA OVER TIME
What is this graph looking at? Average Monthly Arctic Sea Ice Extent September 1979 -2013 What does the black line represent? Why does the black line go up and down so much? What is the purpose of the blue line? What trend or pattern does this graph show?
Graph from http://nsidc.org/arcticseaicenews/2016/06/
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LOOKING AT ABIOTIC (ENVIRONMENTAL) FACTORS
What does the blue line represent? What does the red line represent? What happens to the Adelie penguin population over time? What is the general temperature change (or pattern) over time? Looking at the graph, would you suggest a correlation between changing temperatures and adelie penguin populations?
Graph from http://facts.net/adelie-penguins/
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LOOKING AT BIOTIC (BIOLOGICAL) FACTORS
What does the green line represent? What does the orange line represent? What happens to predator numbers as the number of prey increases? Explain why this might happen. What happens to prey numbers as the number of predators increase? Explain why this might happen. Give an example of a predator and prey in Antarctica.
Graph from https://www.ck12.org/biology/predation/lesson/Predation-BIO/ Credit: Hana Zavadska, Source: CK-12 Foundation, License: CC BY-NC 3.0
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YOUR TURN!
Choose one of the graphs.
Look carefully at what data is shown on the graph.
Think about what patterns or trends you could conclude from the graph.
Answer the questions about the data.
Repeat with another 2 graphs.
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PLENARY - LOOKING AT DATA OVER TIME
What more data would you want to Average Monthly Arctic Sea Ice Extent September 1979 -2013 collect? If you were writing a newspaper article about your findings, what would your headline be? What, if anything, would you be worried about for the future of this ecosystem?
Graph from http://nsidc.org/arcticseaicenews/2016/06/
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PLENARY - LOOKING AT ABIOTIC (ENVIRONMENTAL) FACTORS
What more data would you want to collect? If you wanted to raise awareness of the decline in adelie penguins, what picture and words would you use on an Instagram post? What, if anything, would you be worried about for the future adelie penguins?
Graph from http://facts.net/adelie-penguins/
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PLENARY - LOOKING AT BIOTIC (BIOLOGICAL) FACTORS
If the prey is krill and the predator is blue whales - What more data would you want to collect on krill or blue whales? Are there any additional factors or organisms that your would want to collect data on? How might you use this data to decide on krill fishing limits?
Graph from https://www.ck12.org/biology/predation/lesson/Predation-BIO/ Credit: Hana Zavadska, Source: CK-12 Foundation, License: CC BY-NC 3.0
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PLENARY – WHAT NEXT?
Science is a constant and continuing investigation of the world.
Once scientists have collected and analysed data, they will normally have further questions that they will want to investigate.
Data analysis might answer some questions.
It often leads to scientists asking more questions.
Look at the following graphs again to think about what you would want to investigate in the future.
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WHAT DID YOU LEARN TODAY?
Understand how organisms affect, and are affected by, their environment. Interpret observations and data, including identifying patterns and using observations, measurements and data to draw conclusions. Identify further questions arising from their results.
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KRILL – SO WHY IS IT IMPORTANT TO RESEARCH?
Krill is a good indicator species for the ‘health’ of the Antarctic because it is a keystone species. Many animals in Antarctica are dependent on krill because it is the beginning of so many food chains. Krill fishing is become more viable (with new technology) and more important (krill are used in aquaculture and in health foods). Krill numbers might be in decline. However, without good research into krill density (population size), this is hard to evidence. Krill, like many animals, may be adversely effected by global warming.
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