Interim report of the HELCOM CORESET project

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Step 3: Prepare a list of species/groups routinely identifi ed in zooplankton samples (if unavoidable,
use groups that are pooled in a consistent manner) to calculate ZSD values as a ratio between the number
of species observed in a given year (or season if the assessment is done on a seasonal basis) and the total
number of species ever observed in routine zooplankton monitoring in this area. This is a proxy for species
richness.
Step 4: Prepare available time series or data published in various reports for each of the main indicators
(ZSD, CB, CB%, MMB and MMB%) and additional indicators (MeanSize, Zooplankton/Phytoplankton ratio):
a) Pay particular attention to the data availability for the periods of the high fi sh growth conditions and
acceptable eutrophication levels indentifi ed from the time series for these background data;
b) Note that both absolute biomass (mg/m3; CB and MMB) and relative (proportion or percentage of the
indicator group in the total mesozooplankton biomass; CB% and MMB%) will be needed;
c) When calculating CB and CB%, include all copepodites stages of copepods;
d) When calculating MMB and MMB%, include only holoplankton (i.e., no benthic larvae); most relevant
being the following species/groups:
i rotifers,
ii appendicularians,
iii small (