Marine områder 2011 - DCE - Nationalt Center for Miljø og Energi

10
Summary
Jens Würgler Hansen
The nationwide status of the Danish marine environment in 2011 is summarised
by subject below.
Climate
Air temperature was 1.3 °C higher in 2011 compared to the standard period
1961-1990 but on average level compared to the last 15 years.
Winds were generally weak and mainly from south-easterly directions.
Freshwater run-off to the inner Danish marine waters was 19 % above
normal (1961-1990) and unusually high in late summer due to extensive
rain.
Sea temperature at the surface was higher in 2011 than in the cold 2010
but on level with temperatures since 1989. Bottom water was relatively
cold compared to recent years.
Sea water temperatures have increased about 1.5°C during the last 40
years.
The radiation in 2011 was average, but generally there is a tendency towards
increased radiation in the latest 10 years during the summer
months.
From the 1960s to the mid-1980s pH of sea water increased (approx. 0.3),
but has since decreased equivalently despite an increase over the last
couple of years.
Nutrient loads and concentrations
The total deposition of nitrogen to the Danish marine waters was 79,000
tonnes in 2011.
On average 12 % of the atmospheric nitrogen deposition to the Danish marine
waters originated from Danish sources.
Since 1989 the atmospheric nitrogen deposition to the Danish waters has
experienced a 32 % decline.
Freshwater runoff from land to the Danish marine waters varies substantially
from one year to another. In 2011 the runoff was 9 % more than the
average for the period 1990-2010.
For Denmark as a whole the total phosphorus and nitrogen loads in 2011
were 2,600 tons phosphorus and 59,000 tons nitrogen.
Nitrogen and phosphorus loads have decreased about 50 % and 59 %
since 1990 when corrected for variation in freshwater runoff.
The reduction in phosphorus load is primarily a result of improved
wastewater treatment, whereas the reduction in nitrogen load is mainly a
result of reduced leaching from cultivated land, although also improved
wastewater treatment has contributed significantly to the decrease in nitrogen
load.
Overall, nutrient concentrations in 2011 were relatively low, especially
for nitrogen, despite a relatively large run off.
During the early spring bloom of Chattonella sp. there was a large uptake
of DIN and DIP in the open inner Danish waters. In return, the uptake of
DSi was moderate resulting in relatively high concentrations of DSi.
Nutrient-rich water with low salinity, presumably due to a high fresh water
input, entered the open inner Danish waters from the Baltic Sea in May
and resulted in unusually high nutrient concentrations. However, there
was no sign of the waters being affected significantly by water masses
from the Jutland coastal current.