Corresponding author: Vedran Šegota (
Academic editor: Marko Sabovljevic
An extensive macrophyte field survey of running and standing waters was conducted from 2016 to 2021 at 786 sampling sites across Croatia as a part of the implementation of the Water Framework Directive. This survey is the first to present a comprehensive floristic catalogue of the freshwater bryoflora, along with an analysis of the distribution and diversity patterns on a national level. In all, 83 bryophyte species (68 mosses and 15 liverworts) were recorded in the 228 sites, with average species richness of 4.17 species per site. The most frequent species were
Research was funded by Hrvatske vode and conducted within the national surface water monitoring scheme as required by Water Framework Directive.
Bryophytes colonised aquatic and riparian environments through several independent phylogenetical lineages of terrestrial species, by a secondary process of colonisation and morphological and physiological adaptations to a highly specialised habitat (
The studies on bryophytes of aquatic and semi-aquatic habitats so far conducted in Europe (e.g.
Comprehensive floristic studies on a national level, focusing on diversity, distribution, chorology or life-history traits of aquatic and semi-aquatic bryophytes are very scarce. In Europe, floristic studies were mostly focused on a single watercourse or particular river catchment (
Regarding southeast Europe, freshwater bryoflora is significantly better investigated in Bulgaria than in the rest of this region. Several papers dealing with diversity, ecology, as well as the bioindication potential of these species and their communities are available (
Given that systematic and comprehensive studies on bryophytes inhabiting freshwater habitats are absent from Croatia, we aimed to:
provide the first comprehensive inventory of this understudied group, analyse the distribution and diversity patterns on a national level, examine the chorological spectrum and life-history traits of bryophytes, as well as potential differences between Croatian hydrological and biogeographical regions.
Data on the distribution of bryophytes of freshwater habitats were collected within the national surface water monitoring scheme, i.e. the monitoring of macrophyte vegetation, to assess the ecological status of the water bodies as required by the WFD (
The Pannonian Ecoregion encompasses the continental part of the country, situated between three large rivers (Sava, Drava and Danube). This area consists of alluvial and diluvial plains with altitudes ranging between 80 and 135 m, along with rather low, solitary mountain massifs. According to lithological and geological composition, most of the Pannonian area belongs to silicate Quaternary deposits, while limestone is found only in the highest mountain areas. The climate is temperate, without a dry season, with warm summers in most of the territory (Cfb) and hot summers predominantly in the eastern part (Cfa) (
A survey of macrophyte vegetation was performed according to the national methodology for macrophyte sampling (
The chorological analysis of bryophyte flora was carried out according to
Aquatic and semi-aquatic bryophytes were present at 228 (29%) of the sampling sites (Fig.
Eighty-three bryophyte species, including 68 mosses (
The overall average bryophyte species richness at the 228 sites was 4.17 ± 0.25 species per site, while 27% of the sites had only one species and other sites up to a maximum of 20 species (Fig.
The collected species belong to 10 orders, 21 families and 43 genera (Table
The vast majority of recorded species had quite low coverage in survey localities, with the mean coverage of all species being 3.3%. As many as 69 species had a mean cover in the investigated sites of less than 5%, whereas just three species displayed a mean coverage greater than 10% (
The chorological analyses, based on major biomes, indicated the predominance of the temperate chorotype in Croatian freshwater bryoflora: temperate (30.1%), boreo-temperate (24.1%), southern-temperate (21.7%) and wide-temperate (8.4%). The biogeographical spectrum, based on the eastern limit, showed that the dominant chorotypes were circumpolar (54.2%) and European (31.3%). Analysis of life-forms, based on the species frequencies, revealed that the most dominant were aquatic trailings (28%), turfs (18%), rough mats (15%), smooth mats (11%) and wefts (11%). Regarding the life strategy, the most frequent were perennials (34%), colonists (30%) and competitive perennials (19%).
The recorded bryoflora displays rather wide niche heterogeneity concerning the humidity levels preferred. Only six recorded species could be classified as obligate aquatics, having little or no tolerance to drought conditions (
Concerning the threat status, the majority of the recorded species are considered to be of least concern (LC).
The study revealed that the Dinaric Ecoregion supports higher freshwater bryophyte diversity (70 bryophyte species, out of which 60 are mosses), than the Pannonian Ecoregion with 57 recorded bryophyte species (44 mosses) (Table
The Dinaric Ecoregion had a higher species richness (4.6±0.33 species) and mean coverage (3.6%) per sampling site than the Pannonian Ecoregion (3.4±0.35 species; mean coverage 2.4%) per sampling site (Table
Within the Dinaric Ecoregion, the Continental Subecoregion showed a higher species richness (65 bryophytes; 55 mosses and 10 liverworts) than the Mediterranean Subecoregion with 40 bryophyte species (33 mosses and seven liverworts) recorded within this study. Furthermore, the Continental Subecoregion features higher species richness (5.9 ± 0.58 species) per sampling site than the Mediterranean Subecoregion (3.4±0.29 species), while the mean coverage per sampling site was similar in both subecoregions (Table
The chorological comparison of Croatian eco- and subecoregions, based on major biomes, revealed large chorotype overlapping, with the dominance of temperate chorotypes; however, some biogeographical differences were highlighted. The Mediterranean-Atlantic chorotype was almost completely absent from the Pannonian Ecoregion, while within the Dinaric Ecoregion, this type was more frequent in the Continental Subecoregion. On the other hand, the boreo-arctic and boreal-montane chorotypes were absent in the Mediterranean Subecoregion (Fig.
The chorological comparison of Croatian eco- and subecoregions, based on the eastern limit, showed the dominance of circumpolar and European chorotypes in all eco- and subecoregions (Fig.
Bryophyte life-forms were not evenly distributed within Croatian eco- and subecoregions (Fig.
Regarding the life strategies, all Croatian eco- and subecoregions feature the dominance of perennial and colonist bryophyte species. However, competitive perennial strategy is almost twice as frequent in the Dinaric Ecoregion (21%) as in the Pannonian (13%). Contrarily, the annual shuttle strategy in the Dinaric Ecoregion is almost negligible (1%), while in the Pannonian Ecoregion, it is relatively more frequent (10%) (Fig.
The present study is the first to compile a comprehensive floristic catalogue on Croatian freshwater bryophyte species including 83 species representing 12% of Croatian bryoflora (
The majority of species encountered are not considered to be truly aquatic, confirming other studies investigating the bryoflora of streams and rivers, for example, in the UK (
As previously recorded in other studies (e.g.
The lowest diversity was observed in the Pannonian Ecoregion, which is presumably related to the dominant characteristics of the water bodies there. These are mostly slow, eutrophic lowland streams and rivers with unstable sandy and gravelly alluvial sediments and higher depth of the water column (
The low mean coverages of all species (3.3%) can be explained by the fact that our study included evenly upper, middle and lower river sections. In our study, only three species with mean coverage greater than 10% were either tufa-forming mosses of waterfalls, such as
Amongst dominant families,
Considering the chorological spectrum of studied flora, the prevailing presence of temperate (circumpolar) species corresponds with the biogeographical characteristics of the studied area. This was also detected in the bryoflora of running waters of central Italy (
Bryophyte life-forms can be interpreted as recurring arrangements of the photosynthetic tissues that minimise evaporative water loss and maximise primary production (
Amongst Croatian freshwater bryophytes, the most frequent are those with a potential lifespan longer than one year. This includes perennial life strategy (
Besides the primary intention of the WFD to ensure water quality assessment on the national level, the implementation of monitoring in Croatia yielded a significant amount of new national bryophyte records. Through five years of intensive field surveys of Croatian freshwaters, as many as eight bryophyte species were found as new for national bryoflora:
The added value of our study is that, along with watercourses, we examined standing water bodies for their bryoflora as well. Altogether, nine natural lakes and 36 artificial or heavily-modified standing water bodies were studied. Bryophytes were found at five lakes and 12 artificial or heavily-modified standing water bodies. Most of the 24 recorded bryophyte species occupied shallow waters, lacustrine drawdown zones and moist riparian habitats. However, in our study, scattered populations of the rare species in the Croatian flora,
Bryophytes are an important part of freshwater biodiversity in Croatia, inhabiting a wide variety of ecological niches associated with running and standing waters. The diversity of aquatic and semi-aquatic species is governed by the heterogeneity of different environmental factors, which determine their presence or absence, as well as the community structure. Our research revealed a quite high bryophyte diversity in aquatic and semi-aquatic habitats, with substantial differences between particular regions, especially in species richness and composition, as well as in life-form and life-strategy spectra. The Water Framework Directive not only improved the assessment of the ecological status of water bodies in Croatia by including the bryophytes as a part of macrophyte vegetation, but it has proven to be a good tool for the detection of rare, neglected or overlooked bryophyte species. This is especially important in regions where the bryophytes are still generally little researched, as in the case of southeast Europe. This study is, therefore, a valuable contribution to the knowledge of freshwater bryophyte diversity of Croatia, as well as of southeast Europe.
We would like to thank to Hrvatske vode for funding this research.
A. Rimac - field research, species identification, data preparation and analysis, manuscript writing
V. Šegota - field research, data preparation and analysis, manuscript writing
A. Alegro - field research, species identification, manuscript editing
N. Vuković - field research, manuscript editing
N. Koletić - field research
All the authors read, discussed and approved the final form of the article.
Study area with 786 sampling sites distributed across Croatia (southeast Europe).
Examples of the sampling sites in Croatia:
Distribution of 228 sampling sites with freshwater bryophytes in Croatia.
The most frequent bryophyte species (only species present in over 10 sampling sites are shown) (Font ant–
The most common freshwater bryophyte species in Croatia: A–
The number of species per sampling site.
The most represented families of freshwater bryophytes in Croatia.
Comparison of alpha diversity (Shannon-Wiener and Margalef alpha diversity indices) in the Pannonian Ecoregion, Dinaric Ecoregion, Dinaric–Continental Subecoregion and Dinaric–Mediterranean Subecoregion.
Chorological spectra of freshwater bryophytes, based on major biomes for Croatia, Pannonian Ecoregion, Dinaric Ecoregion, Dinaric–Continental Subecoregion and Dinaric–Mediterranean Subecoregion.
Chorological spectra of freshwater bryophytes, based on the eastern limit for Croatia, Pannonian Ecoregion, Dinaric Ecoregion, Dinaric–Continental Subecoregion and Dinaric–Mediterranean Subecoregion.
Life-form spectra of freshwater bryophytes for Croatia, Pannonian Ecoregion, Dinaric Ecoregion, Dinaric–Continental Subecoregion and Dinaric–Mediterranean Subecoregion, based on species frequencies (At–Aquatic trailing, De–dendroid, Le– lemnoid, Mr–rough mat, Ms–smooth mat, Mt–thalloid mat, St–solitary thalloid, Tf–turf, Ts–scattered turf, Tuft–tuft and We–weft).
Life strategy spectra of freshwater bryophytes for Croatia, Pannonian Ecoregion, Dinaric Ecoregion, Dinaric–Continental Subecoregion and Dinaric–Mediterranean Subecoregion, based on species frequencies (p–perennials, c–colonists, pc–competitive perennials, l–long-lived shuttle, a–annual shuttle, cp–pioneer colonists).
List of bryophyte species, along with the number of occurrences in Croatia and sub- and ecoregions. P–Pannonian Ecoregion, D–Dinaric Ecoregion, C–Continental Subecoregion, M–Mediterranean Subecoregion.
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1. |
D: C (6), M (3) | 9 |
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2. |
P (3); D: C (2), M (1) | 6 |
3. |
P (4); D: C (12), M (7) | 23 |
4. |
D: C (2) | 2 |
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5. |
P (3); D: C (22), M (18) | 43 |
6. |
P (7) | 7 |
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7. |
P (1); D: C (1) | 2 |
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8. |
P (8); D: C (6), M (1) | 15 |
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9. |
P (6); D: C (16), M (2) | 24 |
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10. |
P (4); D: C (1) | 5 |
11. |
P (6); D: C (3), M (1) | 10 |
12. |
P (1) | 1 |
13. |
P (1) | 1 |
14. |
P (3) | 3 |
15. |
P (2) | 2 |
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16. |
D: C (1) | 1 |
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17. |
P (4); D: C (1) | 5 |
18. |
D: M (1) | 1 |
19. |
P (1); D: M (1) | 2 |
20. |
P (2) | 2 |
21. |
D: C (1) | 1 |
22. |
P (8); D: C (10), M (7) | 25 |
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23. |
D: C (3) | 3 |
24. |
D: C (1) | 1 |
25. |
P (1) | 1 |
26. |
P (1); D: C (1) | 2 |
27. |
P (3); D: C (7) | 10 |
28. |
P (12); D: C (2), M (2) | 16 |
29. |
P (1); D: C (1) | 2 |
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30. |
P (1); D: C (4) | 5 |
31. |
P (2); D: C (3) | 5 |
32. |
P (5); D: C (1), M (2) | 8 |
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33. |
P (4); D: C (1) | 5 |
34. |
D: C (1) | 1 |
35. |
P (6); D: C (19), M (14) | 39 |
36. |
P (3); D: M (1) | 4 |
37. |
D: C (1), M (2) | 3 |
38. |
P (5) | 5 |
39. |
P (2); D: C (1), M (2) | 5 |
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40. |
P (1); D: C (2) | 3 |
41. |
D: C (1) | 1 |
42. |
D: C (20), M (16) | 36 |
43. |
P (2); D: C (28), M (21) | 51 |
44. |
P (7); D: C (22), M (13) | 42 |
45. |
D: C (6), M (1) | 7 |
46. |
D: C (1) | 1 |
47. |
D: C (1), M (2) | 3 |
48. |
D: C (3) | 3 |
49. |
D: C (2), M (8) | 10 |
50. |
D: C (6), M (4) | 10 |
51. |
D: C (1) | 1 |
52. |
D: C (3) | 3 |
53. |
D: C (1) | 1 |
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54. |
P (1); D: C (3), M (2) | 6 |
55. |
P (7); D: C (1) | 8 |
56. |
P (1) | 1 |
57. |
P (1) | 1 |
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58. |
P (8); D: C (34), M (25) | 67 |
59. |
P (2); D: C (2), M (4) | 8 |
60. |
P (1) | 1 |
61. |
P (1) | 1 |
62. |
P (2); D: C (1), M (1) | 4 |
63. |
P (2); D: C (3) | 5 |
64. |
D: C (4) | 4 |
65. |
P (42); D: C (19), M (8) | 69 |
66. |
P (2); D: C (3), M (4) | 9 |
67. |
P (1); D: C (6), M (3) | 10 |
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68. |
P (3); D: C (2) | 5 |
69. |
P (2); D: C (10), M (3) | 15 |
70. |
P (4); D: C (6), M (1) | 11 |
71. |
D: C (1), M (1) | 1 |
72. |
P (8); D: C (4) | 12 |
73. |
D: M (1) | 1 |
74. |
P (6); D: C (4), M (1) | 11 |
75. |
D: C (1) | 1 |
76. |
D: C (3) | 3 |
77. |
P (19); D: C (38), M (36) | 93 |
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78. |
P (20); D: C (43), M (47) | 110 |
79. |
P (1); D: C (2) | 3 |
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80. |
P (1); D: C (1), M (2) | 4 |
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81. |
D: C (3), M (2) | 5 |
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82. |
P (1); D: C (7), M (1) | 9 |
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83. |
P (2) | 2 |
Comparison amongst Croatian ecoregions and subecoregions.
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44 | 60 | 55 | 33 |
pleurocarpous | 19 | 23 | 21 | 16 |
acrocarpous | 25 | 37 | 34 | 17 |
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15 | 15 | 10 | 7 |
leafy | 4 | 4 | 4 | 3 |
thallose | 11 | 11 | 6 | 4 |
dominant species* |
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coverage % (mean) | 2.40 | 3.60 | 4.04 | 4.15 |
species richness |
3.40 ± 0.35 | 4.60 ± 0.33 | 5.90 ± 0.58 | 3.40 ± 0.29 |
range (min–max) | 1–15 | 1–20 | 1–20 | 1–12 |
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number of families | 18 | 20 | 20 | 19 |
dominant families** |
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rivers/sampling sites | 50/56 | 69/107 | 39/57 | 30/50 |
artificial and heavily-modified watercourses / sampling sites | 18/20 | 16/25 | 4/5 | 12/20 |
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natural lakes/ sampling sites | - | 5/5 | 3/3 | 2/2 |
artificial or heavily-modified |
3/3 | 9/12 | 3/5 | 6/7 |
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mean ± SE | 146 ± 8.23 | 231 ± 13.53 | 310 ± 18.32 | 162 ± 16.15 |
range (min-max) | 81–547 | 1–711 | 111–703 | 1–711 |
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mean annual air temperature (°C) (± SE) | 11.6 ± 0.1 | 12.4 ± 0.1 | 10.9 ± 0.1 | 13.7 ± 0.1 |
mean daily mean air temperatures of the wettest quarter (°C) (± SE) | 17.4 ± 0.4 | 11.1 ± 0.2 | 11.6 ± 0.3 | 10.7 ± 0.3 |
mean daily mean air temperatures of the driest quarter (°C) (± SE) | 3.3 ± 0.1 | 14.1 ± 0.8 | 6.5 ± 0.9 | 20.9 ± 0.6 |
annual precipitation amount (kg/m2) (mean ± SE) | 935.3 ± 14.6 | 1360.2 ± 20.5 | 1415.1 ± 24.7 | 1311.5 ± 31.0 |
Complete list of the freshwater bryoflora of Croatia with distribution data, chorological and life-trait information on the species and altitude and climatological data of the sites.
Data table
Coordinates are given in WGS84 system. Abbreviations: PAN–Pannonian Ecoregion, DIN CON–Dinaric Ecoregion, Continental Subecoregion, DIN MED–Dinaric Ecoregion, Mediterranean Subecoregion; life-forms: At–Aquatic trailing, De–dendroid, Le –lemnoid, Mr–rough mat, Ms–smooth mat, Mt–thalloid mat, St–solitary thalloid, Tf–turf, Ts–scattered turf, Tuft–tuft and We–weft); life strategy: p–perennials, c–colonists, pc–competitive perennials, l–long-lived shuttle, a–annual shuttle, cp–pioneer colonists, Braun-Blanquet cover and abundance classes: r = one individual, + = up to 5 individuals, 1 = up to 50 individuals, 2m = over 50 individuals, 2a = coverage 5–15%, 2b = coverage 15–25%, 3 = 25–50%; 4 = coverage 50–75%; 5 = coverage over 75%.
File: oo_680458.xlsx