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Checklist of Baltic Sea Macro-species - IOW

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2.3 Defining parameters<br />

The aim has been to compile a checklist valid for the<br />

<strong>Baltic</strong> <strong>Sea</strong> area as defined by HELCOM (see Figure 1).<br />

Species included in the macrophyte checklist were<br />

required to fulfil the following criteria:<br />

1. All <strong>species</strong> should be listed in at least one <strong>of</strong> the<br />

international databases given in Section 2.2 to<br />

verify the taxonomic reference.<br />

2. All <strong>species</strong> should form stable populations in<br />

brackish waters with a minimum salinity <strong>of</strong> at<br />

least 0.5 (identification <strong>of</strong> ‘borderline’ cases with<br />

freshwater and/or land environments).<br />

3. Records for all <strong>species</strong> must be geographically<br />

located within the <strong>Baltic</strong> <strong>Sea</strong> itself and not just in<br />

nearby ponds, rocky pools or rivers.<br />

4. Species identification must be reliable. Therefore,<br />

<strong>species</strong> with a very low number <strong>of</strong> records will<br />

be checked by macrophyte experts and doubtful<br />

identifications will be excluded.<br />

2.4 Distribution<br />

The checklist includes presence/absence data for<br />

the <strong>Baltic</strong> <strong>Sea</strong> sub-basins. The sub-basins used in<br />

the HELCOM Red List project are shown in Figure<br />

1. The total number <strong>of</strong> <strong>species</strong> per sub-basin is<br />

shown in Figure 3.<br />

For the macrophyte checklist a few modifications<br />

were necessary:<br />

• Great Belt and Little Belt were combined<br />

• Bothnian <strong>Sea</strong> and the Quark were combined<br />

• All records from the island <strong>of</strong> Bornholm were<br />

included in the Bornholm Basin<br />

• All records from the island <strong>of</strong> Gotland were<br />

included in the Western Gotland Basin.<br />

Bothnian Bay<br />

10<br />

The Quark<br />

Bothnian <strong>Sea</strong><br />

Gulf <strong>of</strong> Finland<br />

9<br />

Archipelago<br />

<strong>Sea</strong><br />

Åland <strong>Sea</strong><br />

Northern <strong>Baltic</strong><br />

Proper<br />

Western<br />

Gotland Basin<br />

Little Belt<br />

Great Belt<br />

Kattegat<br />

The Sound<br />

Bornholm<br />

Basin<br />

Gulf <strong>of</strong> Riga<br />

Eastern<br />

Gotland Basin<br />

Gulf <strong>of</strong> Gdańsk<br />

2a<br />

1a<br />

1b<br />

1c<br />

1d<br />

1e<br />

2d<br />

2c<br />

2b<br />

4a<br />

3a<br />

8b<br />

8a<br />

6 5c<br />

4b 5a<br />

3b<br />

5b<br />

7<br />

Arkona Basin<br />

Bay <strong>of</strong> Mecklenburg<br />

Kiel Bay<br />

Figure 6. <strong>Baltic</strong> <strong>Sea</strong> sub-basins used for the HELCOM checklist (left) and the geographical areas used by Nielsen et al. (1995);<br />

the publication used as the basis for data compilation (right).<br />

10

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