Increasing frequency and area of harmful algal blooms (HABs) in the East China Sea
DownloaD Graphic 2
In the East China Sea, the number of harmful algal blooms
increased from 10 in 1993 to 86 in 2003, when they
Algal blooms in the East China Sea
covered an area of 13 000 square kilometres. Fertilizer
Frequency of algal blooms/year Area covered (km
2
)
application in the sea’s catchment area has increased by
100 25 000
as much as 250 per cent, notably in the upstream and
coastal provinces of Anhui and Jiangsu, contributing a
80 20 000
high nutrient load to the sea. The blooms, which mostly
occur in the inner shelf of the Yangtze River, have a range 60 15 000
of human well-being and ecosystem implications. High
mortality rates of fish and benthic organisms have also 40 10 000
been observed.
20 5 000
0 0
1993 2000 2001 2002 2003
Source: UNEP-GIWA 2006a
Declines in the volumes of global marine and fresh-
water fisheries are dramatic examples of large-scale
ecosystem degradation related to overfishing, pollu-
tion, habitat disturbance and losses. The worldwide
fishing fleet grew rapidly in the mid 20th century,
with many stocks of fish either being over-exploited
or crashing altogether. Many of the more valuable
species of fish have been subject to particularly
The seafloor off Northwest Australia showing dense populations of corals and sponges
sharp declines and marine ecosystems have been The before trawling (left) and after trawling (right).seafloor off Northwest Australia showing dense populations of corals and sponges
severely damaged.
before
Credit: Keith Sainsbur
trawling (left) and
y, CSIRO
after trawling (right).
Credit: Keith Sainsbury, CSIRO
The greatest threat to biodiversity in deep sea areas
is bottom-trawling. This type of high seas fishing is
most damaging to seamounts and the coldwater cor-
als they sustain, which are home for several commer-
cial bottom-dwelling fish species.
DownloaD Graphic 2
34 VITAL GEO GRAPHICS
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