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Interim report of the HELCOM CORESET project

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ard deviation (SD) was calculated using transformed values and <strong>the</strong>n back-transformed to arrive to <strong>the</strong><br />

upper and lower 95% limits <strong>of</strong> CI. In <strong>the</strong> context <strong>of</strong> GES for CB (CB%), upper limit is not relevant, whereas<br />

lower limit is not relevant for MMB (MMB%). Thus, GES boundary for CB (CB%) is <strong>the</strong> lower 95% CI limit,<br />

and for MMB (MMB%), it is <strong>the</strong> upper 95% CI limit. These values are set as threshold values which mark<br />

<strong>the</strong> boundary between acceptable and unacceptable conditions, i.e. CB (CB%) should not decline below its<br />

GES boundary, whereas MMB (MMB%) should not increase above its GES boundary.<br />

GES boundary for CB%<br />

For <strong>the</strong> data set analyzed, <strong>the</strong> most easy interpretable results were obtained with CB%. The GES boundary<br />

was estimated to be 73% based on <strong>the</strong> reference period 1983-1990, when herring and sprat stocks<br />

were relatively stable and had high WAA and body condition. This reference period was selected based<br />

on <strong>the</strong> data presented by Rahikainen & Stephenson (2004) and Casini et al. (2006). See Guidelines<br />

below for details.<br />

CB%<br />

100<br />

80<br />

60<br />

40<br />

reference<br />

period<br />

CB%<br />

mean<br />

GES<br />

boundary:<br />

lower<br />

95% CI<br />

1980 1990 2000 2010<br />

Year<br />

Figure 4.4. Long-term changes in copepod contribution to <strong>the</strong> total mesozooplankton biomass (CB%) in<br />

<strong>the</strong> Askö area, nor<strong>the</strong>rn Baltic proper (1976-2010; average summer values, n=6). According to <strong>the</strong> trend<br />

observed, CB% >73% indicate good feeding conditions for zooplanktivorous fi sh (green area).<br />

GES boundary for MMB%<br />

For <strong>the</strong> data set analyzed, <strong>the</strong> most easy interpretable results were obtained with MMB%. The GES boundary<br />

estimated was 22% based on <strong>the</strong> reference period 1976-1990, when water transparency complied with<br />

GES levels (various <strong>HELCOM</strong> documents; this period might need refi ning).<br />

MMB%<br />

40<br />

30<br />

20<br />

10<br />

reference period<br />

MMB%<br />

GES<br />

boundary:<br />

upper<br />

95% CI<br />

mean<br />

0<br />

1980 1990 2000 2010<br />

Year<br />

Figure 4.5. Long-term changes in microphagous zooplankton contribution to <strong>the</strong> total mesozooplankton<br />

biomass (MMB%) in <strong>the</strong> Askö area, nor<strong>the</strong>rn Baltic proper (1976-2010; average summer values, n=6).<br />

According to <strong>the</strong> trend observed, MMB%

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