Download Biology response 4 vanishing ecosystems

Vanishing Ecosystems
The bulk of this response is the research you needed to do in order to construct your press
release or other outcome that you decided upon. This response is an opportunity for you
compare what you decided was relevant with the decisions someone else has made.
N.B. If you have chosen to write a press release make sure you start with the most important
facts – the punches - you have to turn the classic way of story telling upside down
What is happening/has happened?
Why is it happening?
Details?
Bring in the details e.g. the carbon cycle much later in your article if you feel that it is
necessary at all. Also try to keep your release to one page of A4 and be concise.
Carbon cycle
In order to understand this topic you need to have a good understanding of the carbon cycle. This
example is interesting as it is quantitative.
The illustration above shows total amounts of stored carbon in black, and annual carbon fluxes in purple.
(Illustration courtesy NASA Earth Science Enterprise). GtC is gigatons of carbon.
Source: http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle4.html
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Increasing carbon dioxide concentration
Analysis of CO2 levels in ice cores have shown scientists that for the 400,000 years before the
industrial revolution began in the 1800s, atmospheric CO2 concentrations remained between 200
and 280 parts per million (ppm). Today CO2 levels are reaching 380 ppm in the atmosphere.
Man’s activities, including burning fossil fuels, cement production and deforestation puts at least 6.6
giga tons (GtC) into the atmosphere each year, but the increase in atmospheric CO2 is only about
one-half of what would have been expected.
Where is the missing carbon dioxide?
You can see from the carbon cycle that there are a number of processes that remove carbon dioxide
from the atmosphere. One of these processes is photosynthesis.
In photosynthesis, plants 'breathe' in carbon dioxide from the atmosphere and, with sunlight energy,
convert it and water into food and oxygen. The oxygen they do not use for respiration is then
‘exhaled’.
Research has shown that increased CO2 levels lead to increased net production by photoautotrophs
[plants, algae, and some bacteria (cyanobacteria) - use light as the source of the needed energy].
There is evidence that at least some of the missing CO2 has been incorporated by:
A - increased growth of forests, especially in North America;
B - increased amounts of phytoplankton in the oceans;
C - uptake by photoautotrophs in desert soils (mechanism as yet unknown).
There are also other processes that remove carbon dioxide from the atmosphere, including carbon
dioxide dissolving in seawater (see next section).
Effects of more carbon dioxide dissolving in the Oceans
About half of the CO2 produced by man’s activities or ‘anthropogenic CO2’ taken up over the last 200
years, can be found in the upper 10 percent of the ocean. The ocean has removed 48 percent of the
CO2 we have released to the atmosphere from burning fossil fuels and cement manufacturing.
Over the long-term, the ocean has been the only reservoir on Earth to consistently take up
anthropogenic CO2 from the atmosphere. This uptake changes seawater chemistry, and can have
significant impacts on the biology of the upper oceans.
The ocean and atmosphere are the two primary 'sinks' [holding tanks] of this carbon dioxide since
the beginning of the industrial revolution.
But that ocean ‘sink’ may be changing.
As CO2 is an acidic gas, the surface ocean pH is dropping as this acidic gas dissolves in the sea.
Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately
8.179 to 8.104. If current scenarios are realised, surface ocean pH could drop lower than it has
been for more than five million years.
This is known to have at least two effects. Firstly, a substantial amount of the calcium carbonate,
found in shells of marine animals living in surface waters, dissolves in the upper acidic ocean.
Secondly, there is a reduced ability to produce protective calcium carbonate shells in many species
of marine organisms at high CO2 levels, including corals and plankton, drifting plants and animals on
which other marine life feeds.
Dissolving calcium carbonate shells also partially act to neutralise CO2, thus allowing the ocean to
take up more carbon dioxide from the atmosphere. However, the effects of decreased calcification
in microscopic algae and animals could alter marine food webs and, combined with other changes in
salinity, temperature and nutrients, could substantially alter the diversity and productivity of the
oceans.
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There may also be many other effects that are, as yet, poorly understood or not even anticipated.
Coral reefs as an example ecosystem
Acidification of oceans could irreversibly destroy coral reefs and other marine ecosystems even if
the atmospheric carbon dioxide stabilises at 450 ppm, which is a lot lower than the predicted levels
in the reported climate change forecasts. If the levels stabilise at this ppm, less than 10% of coral
reefs would be sustained in previously coral inhabited oceans.
Atmospheric CO2 absorbed by the oceans’ surface water changes its pH to an acidic solution,
making certain carbonate minerals dissolve easily in seawater e.g. the shells of many sea creatures,
rendering them unable to survive. One such mineral is aragonite, this mineral is used by corals and
many other marine organisms to form their skeletons. For corals to form and build reefs, which
require rapid, strong supporting growth, their immediate environment needs to be highly
supersaturated with aragonite.
For the rich cold waters near the North and South Pole, the prospects are also worrying. At
atmospheric CO2 levels as low as 450 ppm, large parts of the Southern Ocean, the Arctic Ocean,
and the North Pacific would experience a rise in acidity that would completely alter the water quality;
changing its ecological sustainability which would devastate many of the food chains that rely on
these waters for their survival; e.g. as stated previously, if shells of molluscs, starfish and corals
dissolved, many animals reliant on this food source would starve.
If we do not reduce CO2 levels in the oceans in the in the next few decades, by reducing the level of
atmospheric CO2 we produce, it will result in chemical conditions in our seas that have not been
present for millions of years. Ecosystems like coral reefs that have been around for many millions of
years will not be able to cope with the changes we are inflicting.
Other effects on ocean ecosystems
Ecologically productive cold waters
Marine organisms at the base of the food chain will die as shells will dissolve due to decrease in pH
e.g. Sea butterflies, also known as Thecosomata or flapping snails.
Changes in ocean currents
This would have a dramatic effect on many ecosystems. Effects may be extrapolated from the
changes that happen during eg an El Niño. El Niño is seen as the warm phase of the irregular
climate oscillation called ENSO (El Niño/Southern Oscillation), which is caused by unstable
interactions of the ocean and atmosphere. Conversely to El Niño, the cold phase, La Niña, occurs
with some cooling of the surface waters in the equatorial Pacific Ocean. La Niña events may follow
an El Niño, but not always.
Effect of changing ocean circulation patterns
It has been predicted that if current patterns of change in the Arctic and North Atlantic Oceans
continue, alterations of ocean circulation could occur on a global scale, with potentially dramatic
implications for the world's climate and biosphere.
Over 65 million years, the Earth has undergone several major warming and cooling episodes, which
were initiated by the expansion and contraction of sea ice in the Arctic. When the Arctic cools and
ice sheets and sea ice expand, the increased ice cover increases the ability to reflect the sun's rays
by the ice. When more of the sun is reflected rather than absorbed, this leads to global cooling.
Likewise, when ice sheets and sea ice contract and expose the darker-coloured land or ocean
underneath, heat is absorbed, accelerating warming of the atmosphere.
Changes in Arctic climate and ice cover have led to several reorganizations of Northern ocean
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circulation patterns which seriously affect the saltiness of the sea in places close to the Arctic Circle,
as explained below.
When Arctic climate changes, waters in the Arctic can go from storing large quantities of freshwater
to exporting that freshwater to the North Atlantic in large pulses, referred to as ‘great salinity
anomalies’ (GSA). These GSAs flow southward, disrupting the ocean's circulation patterns and
altering the temperature layers observed in marine ecosystems.
When these GSA’s arrive in the northwest atlantic, some ocean ecosystems see major drops in
salinity or ‘saltiness’, and an explosion of some marine invertebrate populations which like to live in
a freshwater environment; and a collapse of cod stocks, which require salt water to survive and
breed – therefore changing the natural biodiversity and environment; hence, skewing the foodchains
and ecosystems in the vicinity.
Continued exposure to such freshwater ‘forcing’ could disrupt global ocean circulation during the
next century and lead to very abrupt changes in climate; similar to those that occurred at the onset
of the last ice age.
If the Earth's deep ocean circulation were to be shut down, many of the atmospheric, glacial and
oceanic processes that have been stable in recent times would change, and the change is likely to
be rapid.
Other Ecosystems
Land plant ecosystems – surprising effects
Wood, wetland and herbaceous, crop ecosystems are also affected by the rise in CO2 levels. Plants
supply the carbon, food and energy for all living things and require four basic components to deliver
these to all organisms – light, nutrients, water and CO2. Plants evolved at a time when there were
high levels of atmospheric CO2, however since this time, many millions of years ago, the
atmospheric levels have dropped and the plants have adapted to thrive in these conditions.
Changes here can lead to an imbalance in the leaf litter quality (compost/soil enrichment for future
growth) and the decomposition rate of leaf litter. Levels, however, are now on the rise and therefore
plants need to again adjust their optimal living conditions. This adaptation takes a long time and at a
slower rate than the CO2 levels are increasing. However, surprising data shows that there is an
increase in there their reproduction, growth and development – this is a good thing - Yes?
Going further
There is a newly described organism that is an atypical member of the cyanobacteria, a group of
photosynthetic bacteria formerly known as blue-green algae.
Nitrogen fixation in these abundant unicells is decoupled from photosynthesis. So what is the
potential role of these abundant microbes in the ocean?
Unlike all other known free-living cyanobacteria, this one lacks some of the genes needed to carry
out photosynthesis, the process by which plants use light energy to make sugars out of carbon
dioxide and water.
The mysterious microbe can do something very important, though: it provides natural fertilizer to the
oceans by "fixing" nitrogen from the atmosphere into a form useable by other organisms. Although
80 percent of Earth's atmosphere is nitrogen, most organisms cannot use it unless it is "fixed" to
other elements to make molecules like ammonia and nitrate. Because nitrogen is essential for all
forms of life, nitrogen fixation is a major factor controlling overall biological productivity in the
oceans. This new microbe is one of the most abundant nitrogen fixers in many parts of the ocean.
This micro organism is missing the entire set of genes needed for photosystem II and carbon
fixation, essential parts of the molecular machinery that carries out photosynthesis in plants and
cyanobacteria. During photosynthesis, photosystem II generates oxygen by splitting water
molecules. Because oxygen inhibits nitrogen fixation, most nitrogen-fixing cyanobacteria only fix
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nitrogen at night, or do it in specialized cells. The lack of photosystem II enables the new microbe to
fix nitrogen during the day.
But without photosynthesis, it can't take carbon dioxide from the atmosphere and convert it into
sugars. So it's not clear how the new microbe feeds itself. Either it has some way of feeding on
organic matter in its environment, or it lives in close association with other organisms that provide it
with food.
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