Macroalgae and phytoplankton as indicators of ... - Naturstyrelsen

of Danish coastal waters
683 Macroalgea and phytoplankton as indicators of ecological status
This report contributes to the development of tools that can be applied
to assess the five classes of ecological status of the Water Framework Directive
based on the biological quality elements phytoplankton and macroalgae.
Nitrogen inputs and concentrations representing reference
conditions and boundaries between the five ecological status classes were
calculated from estimates of nitrogen inputs from Denmark to the Danish
straits since 1900 combined with expert judgement of the general environmental
conditions of Danish waters during different time periods. From
these calculated nitrogen concentrations and a macroalgal model ecological
status class boundaries were established for six macroalgal indicators
in a number of Danish estuaries and coastal areas. Furthermore, sitespecific
correlations between concentrations of nitrogen and chlorophyll
a were used to define reference conditions and ecological status class boundaries
for the phytoplankton metric ‘mean summer concentration of
chlorophyll a’ in several Danish estuaries and coastal areas. Precision of
the two different chlorophyll a indicators ‘summer mean’ and ‘90-percentile’
was evaluated. The 90-percentile was substantially more uncertain
than the mean or median indicators, particularly for small sample sizes
but also for large sample sizes.
National Environmental Research Institute 978-87-7073-060-0
University of Aarhus . Denmark ISSN 1600-0048