Assessment of biodiversity and environmental quality using macrozoobenthos communities in the seagrass meadow (Gulf of Gdańsk, southern Baltic)

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Sensitivity of taxa used for calculating the Benthic Quality Index (BQI), where 1 = tolerant and 15 = very sensitive

Sensitivity value (Si)	Taxa
1	Oligochaeta, Insecta larvae ind.
5	all polychaetes, Hydrobiidae, Macoma balthica
10	Amphibalanus improvisus, Cyathura carinata, Idotea chelipes, Idotea granulosa, Jaera spp., Corophium multisetosum, all gammarids, Theodoxus fluviatilis, Cerastoderma glaucum, Mya arenaria, Mytilus edulis
15	Idotea balthica, Bathyporeia pilosa, Crangon crangon

Frequency of occurrence (%) of taxa on Długa Mielizna on bare sand (Sand), vegetation-covered sand (Plants + sand) and on plants (Plants) (in bold – taxa observed only in places with plants)

Species	Sand	Plants + sand	Plants
Nematoda	7	75	76
Oligochaeta	53	100	82
Piscicola pojmanskae Bielecki, 1994	0	0	29
Hediste diversicolor (O. F. Müller, 1776)	87	100	82
Marenzelleria spp. Mesnil, 1896	40	81	12
Pygospio elegans Claparéde, 1863	80	94	12
Amphibalanus improvisus (Darwin, 1854)	0	13	29
Mysis relicta Lovén, 1862	0	0	6
Praunus flexuosus (Müller, 1776)	0	0	6
Cyathura carinata (Krøyer, 1847)	13	19	6
Idotea balthica (Pallas, 1772)	0	13	100
Idotea chelipes (Pallas, 1766)	27	94	100
Idotea granulosa Rathke, 1843	0	13	41
Idotea juv.	0	25	100
Jaera spp. Leach, 1814	0	6	35
Bathyporeiapilosa Lindström, 1855	7	0	0
Corophium multisetosum Stock, 1952	20	13	6
Gammarus inaequicauda Stock, 1966	0	0	6
Gammarus locusta (Linnaeus, 1758)	7	13	41
Gammarus oceanicus Segerstråle, 1947	0	0	18
Gammarus zaddachi Sexton, 1912	0	25	53
Gammarus tigrinus Sexton, 1939	13	25	29
Gammarus salinus Spooner, 1947	0	50	88
Gammarus spp. Fabricius, 1775	0	0	12
Gammarus juv.	7	44	100
Crangon crangon (Linnaeus, 1758)	7	6	6
Insecta larvae ind.	7	81	88
Theodoxus fluviatilis (Linnaeus, 1758)	0	6	6
Hydrobiidae Stimpson, 1865	100	100	100
Cerastoderma glaucum (Bruguiére,1789)	20	81	65
Macoma balthica (Linnaeus, 1758)	67	81	24
Mya arenaria Linnaeus, 1758	80	100	53
Mytilus edulis Linnaeus, 1758	27	94	100
Einhornia (Electra) crustulenta (Pallas, 1766)	7	0	24
fish eggs and larvae	0	0	12
Gobiidae	0	0	24
Total number of taxa	19	24	31

Class ranges on bare sand (Sand) and on the vegetation-covered bottom (Plants + sand)

	Class range
Sand	5.8-4.6	4.5-3.4	3.3-2.2	2.1-1.0	<1
Plants+sand	8.4-6.7	6.6-5.0	4.9-3.3	3.2-1.6	<1.6
	Very good	Good	Moderate	Poor	Bad