Interim report of the HELCOM CORESET project

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7. Use of the indicator in previous assessments
Not
8. Link to anthropogenic pressures
The indicator refl ects the response of ephemeral (opportunistic) macroalgae to increased nitrate availability.
Nutrients cause rapid growth of opportunistic species, which can also overgrow and displace perennial
vegetation.
9. Pressure(s) that the indicator refl ect
Input of fertilizers (Waterborne discharges of nitrogen, atmospheric deposition of nitrogen; aquaculture)
and ship traffi c.
10. Spatial considerations
Baltic-wide but eventually with region-specifi c GES boundary values
11. Temporal considerations
Monitoring in the end of growing season. Timing of measurement is important.
12. Current monitoring
Not, but could be included in the current fi eld monitoring with low extra expenses.
13. Proposed or perceived target setting approach with a short justifi cation.
Does not require historical reference conditions. GES boundary will be set on the basis of the response
of the alga length/biomass to the nitrate concentrations. Thus, the target for nitrate concentration in
water determines the boundary between GES and sub-GES. This target has been already established for
coastal water types under the EU WFD and for open sea areas in HELCOM EUTRO PRO. Classifi cation
requires the use of a response curve, which relates the length or biomass measurement to nitrate levels
(and status classes) and wave action of study site.
GES boundaries (response curves) require regional validation (at least on main basin level).
4.14. Size distribution of benthic long-lived species
1. Working team: Benthic habitats and associated communities
Author: Karin Furhaupter
2. Name of candidate indicator
Size distribution of benthic long-lived species (e.g.
Cerastoderma, Macoma or Saduria)
3. Unit of the candidate indicator
Ind./size class
4. Description of proposed indicator
The population structure (abundance per size class) of specifi c, long-lived species like bivalves or Saduria
or decapod crustaceans, which are key-species of different communities or target species of other
ecosystem components (e.g. birds).
The indicator describes the condition (functionality) and abundance of the biological component.
Population structure of food web and community key species is an indicator for the whole habitat
condition.
5. Functional group or habitat type
Infralittoral, circalittoral infauna communities (eventually also sediments below the halocline)
6. Policy relevance
Descriptor 1, criterion 1.6 Habitat condition
Descriptor 4, criterion 4.3 Abundance/distribution of key trophic groups and species
Descriptor 6, criterion 6.2 Condition of the benthic communities
BSAP: Viable populations of species
7. Use of the indicator in previous assessments
Not.