and communities will be negatively affected. It is important to ning of the industrial era (Sabine and Feely, 2007). In so doing,
highlight that enhanced stratification is already a fact in temper- the ocean acted as a buffer for earth’s climate, as this absorption
ate seas at mid-latitudes, where stratification is diminishing the of CO
2
mitigates the effect of global warming by reducing its
total annual primary production as a result of the reduction in the concentration in the atmosphere. However, this continual intake
supply of nutrients to the surface layers (Cushing, 1989; Valdés of CO
2
and heat is changing the ocean in ways that will have
and Moral, 1998; Valdés et al., 2007). Warming temperatures are potentially dangerous consequences for marine ecology and bio-
also changing the geographical ranges of marine species. Chang- diversity. Dissolved CO
2
in sea water lowers the oceans’ pH level,
es in depth range are occurring, as species shift down in the causing acidification, and changing the biogeochemical car-
water column to escape from warming surface waters. There is bonate balance (Gattuso and Buddemeier, 2000; Pörtner et al.,
also evidence that the distribution of zooplankton, fish and other 2004). Levels of pH have declined at an unprecedented rate in
marine fauna has shifted hundreds of kilometers towards higher surface sea water over the last 25 years and will undergo a further
latitudes, especially in the North Atlantic, the Arctic Ocean, and substantial reduction by the end of this century as anthropogenic
the Southwest Pacific Ocean (Cheung et al., 2009) sources of CO
2
continue to increase (Feely et al., 2004).
Another important role played by the ocean is the storage and As the ocean continues to absorb further heat and CO
2
, its ability
exchange of CO
2
with the atmosphere, and its diffusion toward to buffer changes to the atmosphere decreases, so that atmosphere
deeper layers (solubility pump) (Fact box 2) (Siegenthaler and and terrestrial ecosystems will face the full consequences of cli-
Sarmiento, 1993). The ocean has absorbed approximately one- mate change. At high latitudes, dense waters sink, transferring
third of the total anthropogenic CO
2
emissions since the begin- carbon to the deep ocean. Warming of the ocean surface inhibits
this sinking process and therefore reduces the efficiency of CO
2
Fact box 2. The ocean – a giant carbon pump
transport and storage. Furthermore, as water warms up, the solu-
bility of CO
2
declines, therefore less gas can be stored in the sea
The solubility pump: CO
2
is soluble in water. Through a gas-
water. With acidification, warming, reduced circulation and mix-
exchange process CO
2
is transferred from the air to the ocean,
ing, there has been a significant change in plankton productivity
where it forms of dissolved inorganic carbon (DIC). This is a in the ocean, reducing the portion of the carbon budget that would
continuous process, as sea water is under-saturated with CO
2
be carried down to the deep seafloor and stored in sediments.
compared to the atmosphere. The CO
2
is subsequently distrib-
uted by mixing and ocean currents. The process is more effi-
So, the ocean system is being threatened by the anthropogenic
cient at higher latitudes as the uptake of CO
2
as DIC increases
activities which are causing global warming and ocean acidifica-
at lower temperatures since the solubility of CO
2
is higher in
tion. As waters warm up and the chemical composition of the
cold water. By this process, large quantities of CO
2
are removed
ocean changes, the fragile equilibrium that sustains marine bio-
from the atmosphere and stored where they cannot contribute
diversity is being disturbed with serious consequences for the
immediately to the greenhouse effect.
marine ecology and for earth’s climate. There is already some
The biological pump: CO
clear evidence that the global warming trend and increasing
2
is used by phytoplankton to grow.
The excess of primary production sinks from the ocean sur-
emissions of CO
2
and other greenhouse gases are affecting en-
face to the deep sea. In the very long term, part of this carbon
vironmental conditions and biota in the oceans on a global scale.
is stored in sediments and rocks and trapped for periods of
However, we neither fully appreciate nor do we understand how
decades to centuries. In order to predict future CO
significant these effects will be in the near and more distant fu-
2
concentra-
tions in the atmosphere, it is necessary to understand the way
ture. Furthermore, we do not understand the mechanisms and
that the biological pump varies both geographically and tem-
processes that link the responses of individuals of a given spe-
porally. Changes in temperature, acidification, nutrient avail-
cies with shifts in the functioning of marine ecosystems (Valdés
ability, circulation, and mixing all have the potential to change
et al., 2009). Marine scientists need urgently to address climate
plankton productivity and are expected to reduce the trade-off
change issues, particularly to aid our understanding of climate
of CO
2
towards the sea bed. change effects on ecosystem structure, function, biodiversity,
and how human and natural systems adapt to these changes.
27
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71