What will I learn? After taking this course you will have an understanding of Arctic landscapes, how they were formed and how they are changing. You will also learn how scientists from countries around the North are working together to understand how these changes will affect the People of the North and the global community. You will experience a range of scientific topics, up-to-date-methods for understanding our environment, and the current consensus views on the future of the Arctic environment. Do I need prior knowledge? No prior knowledge is needed for this course; participants should only come equipped with natural curiosity and a willingness to invest time in understanding an environmental issue of global concern. The terms and concepts are targeted at an educated public, not specialists, but resources will be provided so those who are motivated can explore some issues in more depth.
Lecture 8. Cold waters
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來自 National Research Tomsk State University 的課程
The Changing Arctic
104 個評分
從本節課中
Life in cold waters
In this module we will talk about high latitude lakes as indicators of environmental change past and present, changes in lake ice; the importance of water colour; wet surfaces and microbes, water plants and animals.
與講師見面
Terry V. CallaghanProfessor of Botany, Honorary Doctor
[NOISE]
[MUSIC]
Which is true?
Is it A, there are more insect species in the Arctic than all the plant species.
Or is it B, there are more species of plants than insects in the Arctic.
Or is it C, there are the same number of plants as insect species in the Arctic.
The answer's A.
there are more species in the Arctic than all the plant species.
>> This section deals with the cold waters of the Arctic,
and the life in those cold waters.
The vast majority of the world's waterbodies, larger than one-tenth
of a square kilometer, are found on permafrost in the north.
That's a really big number.
Together they total more than 300,000 square kilometers.
These Arctic lakes, and waterbodies are really important for many reasons.
That includes being water resources for
people in the mining industry, for bio-diversity, and
not just our bio-diversity, but as we shall see, the bio-diversity of the world.
And also, feedbacks to climate change that we looked at in section four,
and importantly, they contain archives of past environments, and
we will look at that in some detail.
That these Tundra lakes are very diverse, too, and they take many forms.
And the example we see here behind us is the type of lakes that form on
Permafrost thaws, as they're called, Permafrost thaw lakes, Thermokarst lakes,
and they're found in sub-Arctic Canada, and elsewhere.
In complete contrast to those vegetated high carbon areas
are the glaciated rock basin lakes.
It's again from Arctic Canada, but you see here little vegetation,
steep sided rocks and relatively clear waters.
Again, in contrast to the High Arctic lakes, and this particular case of
Lake Hazen in the High Arctic, it used to be permanently covered by ice,
now you can see the ice breaking up for the first time in living memory.
And then, there are the more smaller ponds, and
ponds are different from lakes in that they are small shallow water bodies
that often freeze to the bottom in winter.
Where as the lakes will have water underneath the ice in winter.
Providing a home for fish, and other wildlife.
The lakes of the Arctic are important indicators of climate change.
When we see lakes and ponds change, and
we know something is happening to our environment.
But also, they are really important archives
of past history of our environment in terms of climate, and
many other features, not just the lakes themselves.
Where they are surrounding them.
The sediments, the collections of mud at the bottom of the lake,
collect the remains of anything that's in that lake, that falls on the lake and
go down through the water, and accumulates in the mud, and then,
it's covered by another layer of mud, and so on.
And the types of and plants we've find there.
The biting sorry, the Non-Biting Midge Head
skeleton that you see on the left there.
And, next to it a Birch Pollen Grain, and funny that Birch Pollen Grain, if we find
a lot of them, tells us about the vegetation surrounding that lake or pond.
Is possible to get a huge amount of information about present environment, and
environmental change, and biodiversity by sampling the sediments on the lake.
And very often, we can use boat as platforms sailing onto the lake, and then,
taking cores down from the bottom of the lake.
Retrieving cylinders of mud that contain all these archives.
In the laboratory we separate these layers.
These individual layers that you see here.
And from each layer we look for various.
Signals have passed the environments.
Fundamental to the whole of this environment is looking at the organic
carbon, and dating it using Carbon-14 dating to give us a chronology,
a time when the deposits were formed, the sediments were formed,
and then, we can put a timed history of the lake together.
After that, we can analyze the bio-diversity changes,
the changes in the minute plants and animals that have been in our lake.
And they tell us about temperatures, and even regional vegetation, for
example, the birch pollen grains tell us there was a forest there in the past.
The analyses of magnetic material tell us about erosion process, and then,
assets of organic carbon indicate Indicate organic production in the past, and
also we can imply from that what the feedback to the climate had been
in the past in terms of the release of that carbon as greenhouse gasses.
Lakes and ponds accumulate carbon from aquatic organisms, and
from the land surrounding the water.
For example, the pollen grains reflecting the [INAUDIBLE] forest.
That carbon can be decomposed or released as greenhouses gases, as I mentioned.
Or they can be transported away by resident streams.
In the picture here is a 3 to 4,000 year old core from West Greenland.
And this shows changes in the type of carbon that's been present over time.
You can see, a band Here of aquatic microfossils that tell us that this
was a very productive, open lake.
But at the same time, earlier than that in the sequence, you can see gyttja,
or a band of carbon from peat, indicating that the area was surrounded by peatlands,
and this was not a pure, open lake.
That was an example of type of information that you get.
The question that I want deal with now,
is what is happening to these lakes and ponds.
We know it's getting warmer.
So, what is happening to the ponds and lakes.
Well, as usual it's not a clear answer it's a complicated answer.
The lakes are dynamic even in nature they're dynamic.
They form and they drain, and they form again.
And we've seen this in the section on land form.
But, if we now think about climate warming, and permafrost thaw, and
the directional change not just the natural cycle.
Then, we see that Climate warming.
Permafrost thaw.
Surprisingly, produce two different results.
Two processes.
First of all, lake formation takes place in areas with extensive permafrost.
And wetland creation, take place in areas with less extensive permafrost.
Although, lakes can vanish there too.
And, if we look at the graphic every one of those red spots in this
area of Northern Siberia is a lake or pond that has vanished in the last 30 years.
So, you can see a lot of water resources are disappearing.
The tundra is dying, but in other areas, and
if you'll look at the beginning of the graphic.
You can actually see that the results are not negative,
they're positive in that some lakes are being formed.
So, what's going on?
Well, if we look at this graphic from
the sub-arctic of northern Sweden you can see an experiment that manipulates snow.
Snow insulates permafrost, so,
permafrost starts to thaw under deep snow more than elsewhere.
And, you can see that under those patches of deep snow that we created,
you get shallow, moist depressions, and eventually these will form ponds.
That's one process of creating new ponds.
In complete contrast, in the middle of west Greenland, we can see the opposite
process where a lake, present in 1970, has drained away by 2009.
It's disappeared, probably because this is an area not of organic soil like the last
pictures, but an area of rock where drainage is easier away from the site.
Lakes and ponds are extremely useful for local biodiversity, and
even global diversity as they are summer homes to millions of migratory
bird from around te world.
The various organism interact through complex food webs,
and phytoplankton is basis of all these food webs.
The phytoplankton that go down are eaten by benthic organisms,
benthic invertebrates.
Also, it supports zooplanktons in the open water, and the zooplanktons is eaten
by fish in the lakes, and birds in the more shallow ponds were lakes not survive.
The water fowl and the wetland birds eat fish in lakes and invertebrates, and
zoo plankton in ponds.
And finally, the energy captured under the water is transported
onto land by the predators of those birds, such as the fox.
Some of the wetland organisms include Nitrogen-fixing cyanobacteria,
birds such as the greater snow goose, fish such as the arctic char,
which is extremely important for people who live in the Arctic.
As well as the importance to the people who live in the Arctic,
the organisms that live in the lakes are extremely important to basic
fundamental research such as evolution.
Researchers have been using cold water micro organisms,
which as a diatom on the left, and an branching strand of bacteria on the right,
to ask these questions about evolution.
Theoretically, because these very, very tiny micro organisms come to be dispersed
throughout the atmosphere anywhere on Earth, we would expect,
we would see the same species in similar environments in the Arctic,
in the Antarctic, and even Alpines.
But when we look carefully, what we find is that that's not the case.
If you look at the red lines, they are the number of species per genus or
group in the Arctic.
In Greenland, but, the next side of that,
the blue lines are the number of species or genus in the antarctic and
similar environments, and what we find is a difference.
So, these microorganisms is the arctic, are getting us an indication of how
evolution works at the global scale way beyond the arctic lake where they live.
Our next section focus on both land and
lake ecosystems as they provide services for the people of the north.
>> Which is correct.
A. Thawing permafrost leads to loss of
lakes only.
B. Thawing
permafrost leads to creation of lakes only.
C.
Thawing permafrost leads to both creation and loss of lakes or D.
Thawing permafrost has no effect on the permanence of lakes.
