Macroalgae and phytoplankton as indicators of ... - Naturstyrelsen

3.4.2 Physico-chemical variables
Physico-chemical variables were modelled using the same methodology
as for algal variables. Annual mean levels of physico-chemical variables
varied markedly between areas (Figure 3.7). Nutrient concentrations were
generally highest in inner estuaries and lowest along open coasts. Modelled
mean concentrations of total phosphorus ranged from 0.53 µM TP
at Hesselø to 5.65 µM TP in inner parts of Roskilde Fjord, while concentrations
of inorganic phosphorus ranged from 0.06 µM DIP in Dybsø
Fjord to 4.62 µM DIP in inner parts of Roskilde Fjord (Figure 3.7A, B).
Modelled mean concentrations of total nitrogen ranged from 18.37 µM
TN north of Zealand to 85.33 µM TN in inner parts of Nissum Fjord,
while concentrations of inorganic nitrogen ranged from 0.89 µM DIN at
Hesselø to 33.81 µM DIN in inner parts of Nissum Fjord (Figure 3.7C, D).
Inner estuaries also generally had the most turbid waters with low Secchi
depths and high concentrations of chlorophyll while open coastal
waters had high water clarity and low concentrations of chlorophyll.
Area-specific mean Secchi depths ranged from an average of 1.4 m in
Nissum Fjord to 13.2 m at the west coast of Bornholm while area-specific
mean chlorophyll concentrations ranged from 1.27 µg l -1 in Køge Bay to
7.18 µg l -1 in Skive Fjord (Figure 3.7E, F).
Area-specific mean salinities declined markedly from water bodies in the
north-west towards those in the south-east, reflecting the mixing between
North Sea water of high salinity and Baltic Sea water of low salinity.
Salinity means ranged from an average of 7.3 at the eastern coast of
Bornholm to 30.7 in Nissum Broad (Figure 3.7G).
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