COASTAL DIATOM‐ENVIRONMENT RELATIONSHIPS IN THE BRACKISH BALTIC SEA¹

Abstract

High-quality calibration data sets are required when diatom assemblages are used for monitoring ecological change or reconstructing palaeo-environments. The quality of such data sets can be validated, in addition to other criteria, by the percentage of significant unimodal species responses as a measure of the length of an environmental gradient. This study presents diatom-environment relationships analyzed from a robust data set of diatom communities living on submerged stones along a 2,000 km long coastline in the Baltic Sea area, including 524 samples taken at 135 sites and covering a salinity gradient from 0.4 to 11.4. Altogether, 487 diatom taxa belonging to 102 genera were recorded. Detrended canonical correspondence analysis showed that salinity was the overriding environmental factor regulating diatom community composition, while exposure to wave action and nutrient concentrations were of secondary importance. Modeling the abundances of the 58 most common diatom taxa yielded significant relationships with salinity for 57 taxa. Twenty-three taxa showing monotonic responses were species with optimum distributions in freshwater or marine waters. Thirty-four taxa showing unimodal responses were brackish-water species with maximum distributions at different salinities. Separate analyses for small (cell biovolume <1,000 lm 3 ) and large ( ‡1,000 lm 3 ) taxa yielded similar results. In previous studies along shorter salinity gradients, large and small epilithic diatom taxa responded differently. From our large data, we conclude that counts of large diatom taxa alone seem sufficient for indicating salinity changes in coastal environments with high precision.

Distribution patterns of epilithic diatoms along climatic, spatial and physicochemical variables in the Baltic Sea

“…Therefore, some earlier studies have noted air and water temperatures to be influential to . We also showed silicon to exert a strong effect on littoral diatom composition, which is inconsistent with several previous studies suggesting that silicon is a limiting nutrient only in the pelagic areas [12,19].…”

“…The salinity gradient in our study area was 0.1-6.1, thus making the RDA result consistent with previous studies. Busse and Snoeijs [17], Ulanova and Snoeijs [18], and Ulanova et al [19] studied the Swedish coast (salinity gradient approx. 0.4-11.4) and emphasized the role of salinity as one of the most important explanatory variables for diatoms.…”

“…17,18]. However, sampling has usually covered only a limited spatial scale with the exception of the study by Ulanova et al [19]. Thus, there is a lack of broad research studies investigating the effects of climatic, spatial and water physicochemical variables on benthic diatoms in the Baltic Sea.…”

“…In addition, we observed 18 common taxa that represented at least 1.0% of the identified diatom cells, and whose average abundance in sampling sites also exceeded 1.0% (Table 1) (and see Additional file 3: Supplementary material for the entire list of diatom species).Some of the species were common (>1.0% of cells) only in a particular region of the study area. For example, Navicula incertata was abundant only in the Gulf of Finland and the Archipelago Sea (sampling sites 2-13), while Bacillaria paxillifera (sampling sites [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], Diatoma monoliformis , Fragilaria fasciculata (2-21), Navicula margalithii (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), Nitzschia frustulum , Nitzschia inconspicua and Nitzschia liebetruthii were abundant in all areas except the Bothnian Bay. Encyonema silesiacum (28)(29)(30)…”

“…The study comprised 37 sampling sites located in the southern and western coasts of Finland, in the Gulf of Finland and the Archipelago Sea (sampling sites 1-13), the Bothnian Sea (sampling sites [14][15][16][17][18][19][20][21][22][23] and the Bothnian Bay (sampling sites [24][25][26][27][28][29][30][31][32][33][34][35][36][37]. The northernmost sampling site was in Kemi (65° 44′ N, 24° 34′ E), the southernmost in Hanko (59° 49′ N, 22° 58′ E), the westernmost in Kustavi (60° 33′ N, 21° 22′ E) and the easternmost in Virolahti (60° 35′ N, 27° 42′ E) (Fig.…”