Research Article |
Corresponding author: Katherina Schimani ( k.schimani@bo.berlin ) Academic editor: Jan Pawlowski
© 2023 Katherina Schimani, Nélida Abarca, Oliver Skibbe, Heba Mohamad, Regine Jahn, Wolf-Henning Kusber, Gabriela Laura Campana, Jonas Zimmermann.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Schimani K, Abarca N, Skibbe O, Mohamad H, Jahn R, Kusber W-H, Campana GL, Zimmermann J (2023) Exploring benthic diatom diversity in the West Antarctic Peninsula: insights from a morphological and molecular approach. Metabarcoding and Metagenomics 7: e110194. https://doi.org/10.3897/mbmg.7.110194
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Polar regions are among the most extreme habitats on Earth. However, diatom biodiversity in those regions is much more extensive and ecologically diverse than previously thought. The objective of this study was to add knowledge to benthic diatom biodiversity in Western Antarctic coastal zones via identification by means of morphology, DNA metabarcoding and cultured isolates. In addition, a taxonomically validated reference library for Antarctic benthic diatoms was established with comprehensive information on habitat, morphology and DNA barcodes (rbcL and 18SV4). Benthic samples from marine, brackish and freshwater habitats were taken at the Antarctic Peninsula. A total of 162 clonal cultures were established, resulting in the identification of 60 taxa. The combination of total morphological richness of 174 taxa, including the clones, with an additional 73 taxa just assigned by metabarcoding resulted in 247 infrageneric taxa. Of those taxa, 33 were retrieved by all three methods and 111 only by morphology. The barcode reference library of Antarctic species with the new references obtained through culturing allowed the assignment of 47 taxa in the metabarcoding analyses, which would have been left unassigned because no matching reference sequences were available before. Non–metric multidimensional scaling analyses of morphological as well as molecular data showed a clear separation of diatom communities according to water and substratum types. Many species, especially marine taxa, still have no record in reference databases. This highlights the need for a more comprehensive reference library to further improve routine diatom metabarcoding. Overall, a combination of morphological and molecular methods, along with culturing, provides complementary information on the biodiversity of benthic diatoms in the region.
Antarctic Peninsula, benthic diatoms, DNA metabarcoding, morphology, rbcL, taxonomic reference library, unialgal cultures, 18SV4
The polar regions are among the most extreme environments on Earth. Total darkness in winter is paired with low temperatures, strong winds and heavy snow cover. In contrast, permanent light and higher temperatures in summer result in ice and snow melt (
An ecologically particularly important group of eukaryotic microorganisms in Antarctic shallow water coastal zones are benthic diatoms living on top of or associated with sediments, rocks or sea ice. Their benthic assemblage exerts multiple important functions as primary producers, providing a major food source for a diverse range of organisms such as bacteria by excretion of soluble organic matter, benthic protozoans as well as metazoans (
Numerous recent studies indicate that microorganisms display a distinct biogeography, which is also strongly supported by evidence from different freshwater and soil diatoms (
DNA metabarcoding has emerged as an alternative to light microscope-based identifications (LM) as it provides a faster and cheaper way of identifying species in an environmental sample because the morphological identification and counting of diatoms species in LM is time–consuming and demands extensive expertise since diatom taxonomy is constantly evolving. (
For a reliable identification, an unambiguous link between geno– and phenotype is crucial. Therefore, a comprehensive taxonomic reference library is required where molecular and morphological data are tied together with a taxonomic name (
The objective of this study was to add knowledge to the biodiversity of marine benthic diatoms in Western Antarctic shallow water coastal zone environments. In addition, some brackish and freshwater environments connected to the marine realm were explored. Benthic diatom biodiversity in communities sampled in Potter Cove, King George Island/ Isla 25 de Mayo, West Antarctic Peninsula were identified by the means of morphological and molecular methods to assess the status of their taxonomic coverage in Antarctic regions. To compare the performance of morphology and metabarcoding in the identification and quantification of diatom abundances, our objective was to compare the number of taxa retrieved by both analysis of environmental samples. A further goal was to create a regional vouchered barcode reference library with the help of clone cultures with comprehensive information on habitat, morphology and DNA barcodes (rbcL and 18SV4). This taxonomic reference library was utilized for DNA metabarcoding to access the concealed biodiversity beyond the limits of morphological and cultivating methods. Generating the thus far most extensive biodiversity dataset on Antarctic marine benthic diatoms provides a reference to monitor community changes to predict the potential impact of climate change on the coastal ecosystems of this region.
Epipsammic and epilithic samples from marine, brackish and freshwater habitats were taken in Austral summer 2020 at Potter Cove, a shallow coastal bay at King George Island/ Isla 25 de Mayo, West Antarctic Peninsula (Fig.
A Map of Antarctica. B Map of King George Island/Isla 25 de Mayo. C Map of the Potter Cove, with the 39 sample locations. Blue points represent marine sample locations, green points represent freshwater sample locations and orange points represent brackish water locations. Basemap: Landsat Image Mosaic of Antarctica (LIMA).
In total 39 samples were taken (Table
Sample sites with information on the location, georeference, altitude, collector, water type, substrate type and voucher at the BGBM.
Sample ID | Sampling date | Location | GPS coordinates | Altitude | Collector | Water type | Substrate type | Voucher at BGBM |
---|---|---|---|---|---|---|---|---|
D283 | 28.01.2020 | Coastal zone at Peñón 1 | 62.245938°S, 58.681731°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021363 |
D284 | 28.01.2020 | Lighthouse Melting Pond | 62.240866°S, 58.677563°W | 28 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021364 |
D285 | 29.01.2020 | IT Resevoire | 62.237876°S, 58.662233°W | 12 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021365 |
D286 | 29.01.2020 | Drinking water pond at Carlini station | 62.238091°S, 58.657689°W | 23 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021366 |
D288 | 29.01.2020 | Coastal zone at Peñón 0 | 62.241809°S, 58.681931°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021367 |
D289 | 30.01.2020 | Coastal zone at island A7 | 62.234665°S, 58.664624°W | 10 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021368 |
D290 | 30.01.2020 | Coastal zone at island A7 | 62.234665°S, 58.664624°W | 10 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021369 |
D292 | 30.01.2020 | Coastal zone at island A7 | 62.234665°S, 58.664624°W | 10 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021370 |
D293 | 30.01.2020 | Coastal zone at island A7 | 62.234665°S, 58.664624°W | 10 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021371 |
D294 | 30.01.2020 | Coastal zone east of Carlini station | 62.235314°S, 58.656489°W | 0 m | J. Zimmermann | brackish water | epipsammic biofilm | B 50 0021372 |
D295 | 30.01.2020 | Coastal zone east of Carlini station | 62.235771°S, 58.658364°W | 0 m | J. Zimmermann | brackish water | epipsammic biofilm | B 50 0021373 |
D296 | 31.01.2020 | Coastal zone at island A4 | 62.229219°S, 58.663369°W | 15 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021374 |
D297 | 31.01.2020 | Coastal zone at island A4 | 62.229219°S, 58.663369°W | 15 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | episammic biofilm | B 50 0021375 |
D299 | 01.02.2020 | Glacier meltwater run-off in Tres Hermanos area | 62.251939°S, 58.652703°W | 60 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021376 |
D300 | 01.02.2020 | Drinking Water Reservoire | 62.237861°S, 58.662250°W | 51 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021377 |
D301 | 04.02.2020 | Coastal zone at island A4 | 62.229219°S, 58.663369°W | 5 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | biofilm from stones | B 50 0021378 |
D302 | 04.02.2020 | Coastal zone at island A4 | 62.229219°S, 58.663369°W | 5 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021379 |
D303 | 04.02.2020 | Glacier meltwater run-off Fourcade | 62.236639°S, 58.647028°W | 10–15 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021380 |
D304 | 04.02.2020 | Glacier meltwater run-off Fourcade | 62.236639°S, 58.647028°W | 10–15 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021381 |
D305 | 05.02.2020 | Coastal zone at island A4 | 62.229219°S, 58.663369°W | 20 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021382 |
D306 | 06.02.2020 | Coastal zone at Punta Elefante | 62.237353°S, 58.679569°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021383 |
D307 | 07.02.2020 | Coastal zone at Peñón 1 | 62.247261°S, 58.680051°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021384 |
D308 | 07.02.2020 | Coastal zone at Peñón 1 | 62.247261°S, 58.680051°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021385 |
D309 | 07.02.2020 | Diver’s container at Carlini station | 62.237459°S, 58.667529°W | 2 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | biofilm from stones | B 50 0021386 |
D310 | 07.02.2020 | Coastal zone at Peñón de Pesca | 62.237906°S, 58.712278°W | 5 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | biofilm from stones | B 50 0021387 |
D311 | 08.02.2020 | Coastal zone at Punta Stranger | 62.256388°S, 58.625618°W | 2 m | J. Zimmermann | marine | biofilm from stones | B 50 0021388 |
D312 | 08.02.2020 | Coastal zone at Punta Stranger | 62.256296°S, 58.626069°W | 2 m | J. Zimmermann | marine | biofilm from stones | B 50 0021389 |
D313 | 08.02.2020 | Coastal zone at Punta Stranger | 62.258227°S, 58.642172°W | 1 m | J. Zimmermann | marine | biofilm from stones | B 50 0021390 |
D314 | 09.02.2020 | Glacier meltwater run-off Refugio Albatros | 62.252046°S, 58.659456°W | 49 m | J. Zimmermann | freshwater | biofilm from stones | B 50 0021391 |
D315 | 09.02.2020 | Coastal zone at Peñón 4 | 62.256107°S, 58.659703°W | 2 m | J. Zimmermann | marine | biofilm from stones | B 50 0021392 |
D316 | 09.02.2020 | Coastal zone at Peñón 2 | 62.250540°S, 58.675029°W | 2 m | J. Zimmermann | marine | biofilm from stones | B 50 0021393 |
D317 | 09.02.2020 | Coastal zone at Peñón 1 | 62.247073°S, 58.683764°W | 2 m | J. Zimmermann | marine | biofilm from stones | B 50 0021394 |
D318 | 10.02.2020 | Coastal zone at Peñón 2 | 62.250704°S, 58.675778°W | 1 m | J. Zimmermann | marine | biofilm from stones | B 50 0021395 |
D319 | 12.02.2020 | Coastal zone at Carlini station | 62.236950°S, 58.663583°W | 1 m | J. Zimmermann | marine | biofilm from stones | B 50 0021396 |
D320 | 13.02.2020 | Coastal zone at Punta Stranger | 62.256109°S, 58.630578°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021397 |
D321 | 13.02.2020 | Coastal zone at Punta Stranger- Peñón 4 | 62.256615°S, 58.641681°W | 0 m | J. Zimmermann | marine | biofilm from stones | B 50 0021398 |
D322 | 14.02.2020 | Coastal zone at island A2 | 62.227633°S, 58.678734°W | 10 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021399 |
D324 | 16.02.2020 | Coastal zone at island A6 | 62.223800°S, 58.642639°W | 15 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021400 |
D325 | 17.02.2020 | Coastal zone at island A6 | 62.223800°S, 58.642639°W | 20 m deep | J. Zimmermann, G. L. Campana, Divers Carlini Station | marine | epipsammic biofilm | B 50 0021401 |
At each sample location a composite sample of 60 ml was taken along a transect of approximately 10 m. At sample locations with rocky substrate the biofilm of three to four stones along the transect was scratched with a knife. At locations with soft sediment a sediment corer was used to collect the material of three to four spots along the transect. The top layer of the cores was then sampled with a syringe. The composite samples were homogenized, and divided into 3 subsamples of 20 ml each, which were used for 3 different purposes: 1) fixed in 70% alcohol for morphological identification of the mixed diatom community, 2) stored cooled for the establishment of clone cultures to build the barcode library and 3) fixed in 99% ethanol and frozen for a community analysis via DNA metabarcoding.
Following the procedures outlined in
Environmental samples and material harvested from the unialgal cultures were treated with 35% hydrogen peroxide at room temperature to oxidize the organic material and washed with distilled water as described in
Each environmental sample was inspected for their benthic diatom composition using LM. Observations were conducted with a Zeiss Axioplan Microscope equipped with Differential Interference Contrast (DIC) using a Zeiss 100× PlanApochromat objective. Microphotographs were taken with an AXIOCAM MRc camera. To record the occurrence and abundance of each diatom taxon at all sampling sites, at least 400 frustules were counted per sample and the relative abundance of each taxon calculated. All samples were scanned for rare species.
Furthermore, morphological identification of the unialgal cultures were conducted also by LM and extended by scanning electron microscopy (SEM) if appropriate. Therefore, aliquots of cleaned culture material were dried on silicon wafers and mounted on stubs and observed under a Hitachi FE 8010 scanning electron microscope operated at 1.0 kV.
Cultured material was first centrifuged, and culture medium was discarded by carefully pipetting. DNA was isolated from the remaining pellet using NucleoSpin Plant II Mini Kit (Macherey–Nagel, Düren, Germany) following product instructions. DNA fragment size and concentrations were evaluated via gel electrophoresis (1.5% agarose gel) and Nanodrop (PeqLab Biotechnology LLC; Erlangen, Germany) respectively. Amplification was conducted by polymerase chain reaction (PCR) after
A volume of 2–4 ml of each sample was centrifuged at 4 °C and 11.000 rpm for 5 min. The supernatant was removed and from the remaining pellet the DNA was extracted with the NucleoSpin Soil Kit (Macherey and Nagel) following the manufacturer instructions. Short areas of the hypervariable region V4 of the 18S rRNA gene and the rbcL plastid gene were amplified in separated target PCRs. For the 18S V4 region the Nextera primers DIV4for: 5’ – GCGGTAATTCCAGCTCCAATAG–3’ and DIV4rev3: 5’ – CTCTGACAATGGAATACGAATA–3’ were used after
Raw demultiplexed reads were deposited at GenBanks Sequence Read Archive and are publicly available under project number PRJNA997374.
The BeGenDiv performed demultiplexing of the samples providing two fastq files per sample containing forward reads (R1) and reverse reads (R2) respectively. Primers were removed from the reads with cutadapt (
Taxonomic assignment for each barcode was performed using an own established reference library comprising the Diat.barcode library (
After bioinformatic analyses with DADA2 the R package metabaR was used to identify artefactual sequences like contaminants and tag–jumps (
Venn diagrams with eulerr (
In total, 142 diatom taxa were identified through counts of valves in LM, 50 to genus level and 88 to species level (Table
LM pictures of taxa found by morphological analyses. A Odontella litigiosa. B Porosira cf. glacialis. C Thalassiosira scotia. D Thalassiosira antarctica. E Melosira sp. F Unidentified centric diatom. G Minidiscus chilensis. H Orthoseira roeseana. I Shionodiscus gracilis var. expectus. J Actinocyclus actinochilus. K Trigonium arcticum. L Ellerbeckia sol. M Corethron pennatum. Scale bars: 10 µm (A–J); 50 µm (K–M).
List of all taxa observed in light microscopy (LM) with author, references and morphometric information. (R) behind the taxa indicates that it was a rare species just observed in a thorough scan of the slide.
Taxa | Author | Reference | Length [µm] | Width [µm] | Diameter [µm] | Striae RV in 10 µm | Striae RLV in 10 µm | Areolae in 10 µm | Fibulae in 10 µm |
---|---|---|---|---|---|---|---|---|---|
Achnanthes bongrainii | (M. Peragallo) A. Mann |
|
27.2–50.3 | 7.6–11.1 | 6–8 | 6–7 | |||
Achnanthes vicentii | Manguin |
|
4.6–16.2 | 4.0–7.1 | 12–16 | 11–16 | |||
Achnanthes sp. 1 | 21.8–32.4 | 8.4–10.3 | 8–10 | 8 | |||||
Achnanthes sp. 2 | 16.2–47.8 | 6.2–10.5 | 6–8 | 6–8 | |||||
Achnanthes sp. 3 | 31.8–34.3 | 4.0–5.5 | 11 | 9–10 | |||||
Achnanthes sp. 4 (R) | 13.9–23.4 | 4.3–4.5 | 10 | 8–10 | |||||
Achnanthes sp. 5 (R) | 48.5 | 9.8 | 6 | ||||||
Achnanthidium australexiguum | Van de Vijver |
|
13.1–16.9 | 5.6–7.4 | 26–28 | 24–26 | |||
Achnanthidium cf. maritimo-antarcticum | Van de Vijver & Kopalová |
|
14.0–16.9 | 2.3–2.6 | 28–32 | ||||
Actinocyclus actinochilus | (Ehrenberg) Simonsen |
|
57.5 | 9–10 | |||||
Amphora gourdonii | M. Peragallo |
|
23.2–64.4 | 6.6–10.8 | 9–13 | ||||
Amphora cf. gourdonii (R) | M. Peragallo |
|
25.7–37.3 | 4.8–7.2 | 11–16 | ||||
Amphora cf. pusio (R) | Cleve |
|
21.4–30.3 | 3.9–6.8 | 13–17 | ||||
Amphora sp. (R) | 37.7 | 7.5 | 11 | ||||||
Australoneis frenguelliae | (Riaux-Gobin & J.M.Guerrero) J.M.Guerrero & Riaux-Gobin |
|
22.4–34.3 | 12.5–20.5 | 4–5 | 5–6 | |||
Berkeleya rutilans | (Trentep. ex Roth) Grunow |
|
21.6–24.6 | 5.6–6.9 | 28–30 | ||||
Berkeleya cf. sparsa (R) | Mizuno |
|
24.8–35.9 | 5.0–6.0 | 22–26 | ||||
Biremis ambigua | (Cleve) D.G. Mann |
|
33.7–48.8 | 5.0–5.8 | 6–8 | ||||
Brachysira minor | (Krasske) Lange Bertalot |
|
10.4–18.1 | 3.4–4.3 | |||||
Brandinia charcotii | (Perag.) Zidarova & P.Ivanov |
|
68.7 | 8.7 | 13 | ||||
Caloneis australis | Zidarova, Kopalova & Van de Vijver |
|
25.6 | 4.3 | 22 | ||||
Chamaepinnularia australis | Schimani & N. Abarca |
|
9.7–19.2 | 4.2–5.5 | 18–24 | ||||
Chamaepinnularia gerlachei | Van de Vijver & Sterken |
|
9.0–21.8 | 3.1–5.2 | 16–20 | ||||
cf. Chamaepinnularia | 17.7–39.9 | 3.6–5.1 | 14–15 | ||||||
cf. Cocconeis 1 | 10.6–22.2 | 6.5–15.2 | 14–19 | 14–18 | |||||
Cocconeis antiqua | Tempère & Brun |
|
49.3–79.0 | 31.1–51.5 | 11–15 | 13–19 | |||
Cocconeis californica | Grunow |
|
11.2–24.8 | 6.4–15.5 | 17–20 | 11–16 | |||
Cocconeis costata | Gregory |
|
14.9–30.4 | 8.3–15.0 | 10–12 | 8–10 | |||
Cocconeis dallmannii | Al-Handal, Riaux-Gobin, Romero & Wulff | Al-Handal et al. 2008: p. 275, figs 33–48 | 11.9–20.7 | 8.2–14.9 | 13–19 | 10–12 | |||
Cocconeis fasciolata | (Ehrenberg) Brown |
|
21.7–45.0 | 12.4–28.3 | 5–6 | 5–7 | |||
Cocconeis imperatrix | A. Schmidt |
|
47.2–68.8 | 31.8–44.4 | 4–5 | 4–5 | |||
Cocconeis infirmata | Manguin |
|
10.7–24.9 | 6.0–17.4 | 8–16 | ||||
Cocconeis matsii | (Al-Handal, Riaux-Gobin & Wulff) Riaux-Gobin, Compère, Romero & D.M.Williams |
|
9.2–19.4 | 5.7–11.9 | 5–8 | ||||
Cocconeis melchioroides | Al-Handal, Riaux-Gobin, Romero & Wulff | Al-Handal et al. 2008: p. 271, figs 2–15, 18–32 | 9.9–20.4 | 7.0–10.6 | 12–14 | 6–10 | |||
Cocconeis pottercovei | Al-Handal, Riaux-Gobin et Wulff |
|
11.2–14.8 | 7.1–8.9 | 11–13 | 10–12 | |||
Corethron pennatum | (Grunow) Ostenfeld |
|
17.8 | ||||||
Craspedostauros laevissimus | (West & G.S.West) Sabbe |
|
30.2–49.4 | 4.7–5.6 | 26–29 | ||||
Diploneis sp. | 17.8 | 6.6 | 16 | ||||||
Ellerbeckia sol | (Ehrenberg) R.M.Crawford & P.A.Sims | as Melosira sol in |
94.4–102.6 | ||||||
Encyonema ventricosum | (C.Agardh) Grunow |
|
12.9–23.4 | 4.7–6.4 | 15–19 | ||||
Entomoneis sp. | 52.1–53.2 | 6.5–11.1 | 30 | ||||||
Entopyla ocellata | (Arnott) Grunow |
|
60.8 | 16.6 | 3 | ||||
Fallacia marnieri | (Manguin) Witkowski, Lange-Bertalot & Metzeltin | as Navicula marnieri in |
10.1(6.1)–24.5 | 5.4(3.8)–11.0 | 9–14(15) | ||||
Fragilaria cf. parva | Tuji & D.M.Williams |
|
16.1–52.1 | 2.6–4.8 | 15–20 | ||||
Fragilaria cf. striatula | Lyngbye |
|
43.0–51.7 | 7.5–8.1 | 13–14 | ||||
Fragilariopsis curta | (Van Heurck) Hustedt |
|
11.7–31.4 | 5.7–6.6 | 10–13 | ||||
Fragilariopsis cylindrus | (Grunow ex Cleve) Helmcke & Krieger |
|
3.7–16.4 | 2.4–3.4 | 15–16 | ||||
Fragilariopsis kerguelensis | (O’Meara) Hustedt |
|
25.8–27.5 | 7.8–8.7 | 5–6 | 11 | |||
Fragilariopsis rhombica | (O’Meara) Hustedt |
|
12.6–33.2 | 8.4–11.6 | 11–16 | ||||
Fragilariopsis separanda | Hustedt |
|
11.8–15.3 | 7.6–9.1 | 8–13 | ||||
cf. Gedaniella | 9.3–18.9 | 2.4–4.4 | 14–18 | ||||||
Gomphonema maritimo-antarcticum | Van de Vijver, Kopalová, Zidarova & Kociolek |
|
15.3–39.7 | 4.7–7.5 | 10–15 | ||||
Gomphonemopsis ligowskii | Al-Handal & E.W.Thomas |
|
11.4–16.3 | 2.1–2.9 | 14–16 | ||||
Gyrosigma cf. fasciola | J.W. Griffith & Henfrey |
|
101.2–172.8 | 12.4–15.9 | 20–22 | ||||
Gyrosigma tenuissimum var. angustissimum | Simonsen |
|
155.2–159.6 | 7.4 | 19 | ||||
Gyrosigma sp. | 158.0–256.9 | 15.5–20.4 | 22–24 | ||||||
cf. Halamphora (R) | 21.7 | 3.0 | |||||||
Halamphora ausloosiana | Van de Vijver & Kopalová |
|
16.4–36.5 | 4.5–6.9 | 22–24 | ||||
Halamphora lineata | (Gregory) Levkov |
|
37.0–44.0 | 5.8–7.1 | 15 | ||||
Halamphora cf. staurophora | (Juhlin-Dannfelt) Álvarez-Blanco & S.Blanco |
|
13.7–21.0 | 3.3–3.6 | 24 | ||||
Halamphora cf. veneta (R) | (Kützing) Levkov |
|
39.1 | 5.8 | 23 | ||||
Halamphora sp. 1 (R) | 36.9 | 7.6 | 16 | ||||||
Halamphora sp. 2 | 34.9–38.3 | 4.4–6.2 | 11–14 | ||||||
Halamphora sp. 3 (R) | 17.4–21.0 | 4.3–5.0 | 14 | ||||||
Hantzschia amphioxys (R) | (Ehrenberg) Grunow |
|
31.5–49.8 | 6.1–6.3 | 21–22 | 4–6 | |||
Hantzschia hyperaustralis | Van de Vijver & Zidarova |
|
79.7–109.2 | 12.4–14.8 | 20–21 | 4–7 | |||
Hantzschia cf. virgata | (Roper) Grunow |
|
72.3–81.6 | 7.7–9.0 | 11–13 | 24 | 6 | ||
Hippodonta hungarica | (Grunow) Lange-Bertalot, Metzeltin & Witkowski |
|
12.4–18.2 | 4.8–5.4 | 9–10 | ||||
Humidophila sceppacuerciae | Kopalová |
|
7.7–9.6 | 2.1–3.1 | |||||
Humidophila tabellariaeformis | (Krasske) R.L. Lowe et al. |
|
13.9–15.0 | 4.9–5.1 | 25–26 | ||||
Licmophora antarctica | M. Peragallo |
|
47.1–100.5 | 9.6–12.6 | 6–7 | ||||
Licmophora belgicae (R) | M. Peragallo |
|
134.6 | 15.6 | 11 | ||||
Licmophora cf. gracilis | (Ehrenberg) Grunow |
|
22.2–56.9 | 5.0–12.2 | 17–25 | ||||
Luticola australomutica | Van de Vijver |
|
18.8 | 6.7 | 20 | ||||
Luticola austroatlantica (R) | Van de Vijver, Kopalová, Spaulding & Esposito |
|
21.4–23.6 | 7.4 | 16 | ||||
Luticola desmetii | Kopalová & Van de Vijver |
|
21.9–29.3 | 10.6–12.6 | 15–16 | ||||
Luticola higleri | Van de Vijver, Van Dam & Beyens |
|
10.7–28.5 | 7.2–10.3 | 12–18 | ||||
Luticola cf. muticopsis | (Van Heurck) D.G. Mann |
|
13.7–20.0 | 6.6–8.2 | 16 | ||||
Luticola cf. truncata | Kopalová & Van de Vijver | Kopalová et al. 2009: p. 118, figs 34–50 | 13.7–20.0 | 6.6–8.2 | 16 | ||||
Mayamaea cf. permitis | (Hustedt) K.Bruder & Medlin |
|
6.4–7.3 | 3.3–3.5 | |||||
Mayamaea sweetloveana | Zidarova, Kopalová & Van de Vijver |
|
6.8–7.7 | 3.8–4.7 | 20–26 | ||||
Minidiscus chilensis | Rivera |
|
2.9–3.5 | ||||||
Navicula australoshetlandica | Van de Vijver |
|
13.0–30.5 | 4.5–6.0 | 12–15 | ||||
Navicula concordia | Riaux-Gobin & Witkowski |
|
19.5–30.5 | 4.7–6.9 | 13–15 | ||||
Navicula cremeri | Van de Vijver & Zidarova |
|
27.3 | 5.5 | 12 | ||||
Navicula criophiliforma | Witkowski, Riaux-Gobin & Daniszewska-Kowalczyk |
|
23.3–55.9 | 5.8–8.5 | 11–13 | ||||
Navicula directa | (W.Smith) Ralfs |
|
67.7–123.6 | 8.2–13.1 | 7–9 | ||||
Navicula glaciei | Van Heurck |
|
16.3–25.6 | 5.2–6.7 | 13–18 | ||||
Navicula gregaria | Donkin |
|
16.4–25.6 | 5.1–6.6 | 16–20 | ||||
Navicula cf. pagophila var. manitounukensis (R) | Poulin & Cardinal |
|
27.0–32.1 | 10.8–12.8 | 21–26 | ||||
Navicula cf. perminuta | Grunow |
|
5.5–19.9 | 1.9–5.0 | 12–20 | ||||
Navicula sp. 2 | 20.9–48.6 | 3.6–6.6 | 12–16 | ||||||
Navicula sp. 3 | 18.0–31.5 | 3.9–5.4 | 10–15 | ||||||
Navicula sp. 4 | 14.2–24.0 | 2.8–3.7 | 11–14 | ||||||
Navicula sp. 5 | 16.9–48.9 | 4.4–7.4 | 10–14 | ||||||
Navicula sp. 6 | 21.8–24.4 | 3.8–4.3 | 12–14 | ||||||
Navicula sp. 7 | 14.4–28.1 | 4.3–5.2 | 12–15 | ||||||
Navicula sp. 8 | 17.8–29.6 | 3.0–4.7 | 9–11 | ||||||
Navicula sp. 9 | 14.0–17.3 | 2.9–3.3 | 19–21 | ||||||
Navicula sp. 10 | 40.3–57.7 | 5.8–7.4 | 8–9 | ||||||
Navicula sp. 11 | 27.3–31.4 | 4.9–5.3 | 8–9 | ||||||
Navicula sp. 12 | 31.9–42.2 | 6.4–7.6 | 8–9 | ||||||
Navicula sp. 13 | 16.5–31.9 | 4.5–6.3 | 11–14 | ||||||
Navicula sp. 14 | 6.0–13.5 | 3.2–5.5 | 14–20 | ||||||
Nitzschia annewillemsiana | Hamsher, Kopalová, Kociolek, Zidarova & Van de Vijver |
|
10.6–23.1 | 2.9–4.1 | 24–26 | 10–12 | |||
Nitzschia kleinteichiana | Hamsher, Kopalová, Kociolek, Zidarova & Van de Vijver |
|
14.2–23.3 | 2.5–3.3 | 25–29 | 10–14 | |||
Nitzschia cf. gracilis | Hantzsch |
|
29.0–54.7 | 2.5–4.3 | 14–18 | ||||
Nitzschia homburgiensis | Lange-Bertalot |
|
29.1–39.2 | 3.9–5.1 | 10–16 | ||||
Nitzschia cf. hybrida | Grunow |
|
59.8–73.5 | 5.1–6.9 | 24–25 | 8–12 | |||
Nitzschia medioconstricta | Hustedt |
|
52.3–72.1 | 4.4–6.8 | 24–26 | 8–11 | |||
Nitzschia soratensis | Morales & Vis |
|
6.4–17.1 | 2.6–3.5 | 28–30 | 8–12 | |||
Nitzschia sp. 1 (R) | 17.6 | 3.5 | 13 | ||||||
Nitzschia sp. 2 | 23.9–31.6 | 2.9–4.4 | 10–12 | ||||||
Nitzschia sp. 4 | 32.8–44.3 | 4.1–6.8 | 24–29 | 8–12 | |||||
Nitzschia sp. 5 | 41.4–48.1 | 3.6–3.7 | 9–11 | ||||||
Nitzschia sp. 6 | 22.3–28.2 | 4.4–5.5 | 14–17 | ||||||
Nitzschia sp. 7 | 12.2–24.3 | 3.1–5.0 | 12–17 | ||||||
Odontella litigiosa | (Van Heurck) Hoban | as Biddulphia litigiosa in |
23.6–52.5 | 17.6–60.7 | |||||
Orthoseira roeseana (R) | (Rabenhorst) Pfitzer |
|
13.3 | ||||||
Parlibellus cf. schuetii (R) | (Van Heurck) E.J.Cox |
|
71.0 | 24.0 | 14 | ||||
Petroneis cf. plagiostoma | (Grunow) D.G.Mann |
|
36.6–48.8 | 18.1–20.8 | 10–12 | 6–12 | |||
Petroneis sp. 1 | 19.0–22.0 | 7.7–8.1 | 19 | 12–20 | |||||
Petroneis sp. 2 | 21.3–26.6 | 10.2–11.1 | 16–19 | 12–20 | |||||
Pinnularia australoglobiceps | Zidarova, Kopalová & Van de Vijver |
|
30.1–35.8 | 10.4–12.9 | 12–14 | ||||
Pinnularia australomicrostauron | Zidarova, Kopalová & Van de Vijver |
|
24.7–63.0 | 9.7–12.7 | 12–14 | ||||
Pinnularia australorabenhorstii (R) | Van de Vijver |
|
42.0 | 16.7 | 6–8 | ||||
Pinnularia borealis (R) | Ehrenberg |
|
42.3 | 9.0 | 5–6 | ||||
Pinnularia parallelimarginata | Simonsen |
|
30.5 | 5.1 | 15 | ||||
Pinnularia cf. quadratarea | (A.Schmidt) Cleve |
|
18.0–79.8 | 6.1–10.5 | 8–12 | ||||
Pinnularia subantarctica var. elongata (R) | (Manguin) Van de Vijver & Le Cohu |
|
25.9–32.2 | 5.5–6.0 | 14 | ||||
Placoneis australis | Van de Vijver & Zidarova |
|
21.4–23.0 | 6.5–7.4 | 14–18 | ||||
Planothidium australe | (Manguin) Le Cohu |
|
12.3–22.3 | 7.4–9.6 | 13–17 | 14–17 | |||
Planothidium quadripunctatum | (Oppenheim) Sabbe |
|
8.4–9.8 | 3.9–4.5 | 16–18 | 16–17 | |||
Planothidium rostrolanceolatum | Van de Vijver, Kopalová & Zidarova | Van de Vijver et al. 2013: p. 109, figs 61–84 | 15.0–27.5 | 5.3–7.9 | 13–16 | 13–16 | |||
Planothidium wetzelii | Schimani, N.Abarca & R.Jahn |
|
10.9–18.8 | 5.6–6.7 | 14–18 | 14–18 | |||
Planothidium sp. | 13.6–19.9 | 5.6–8.6 | 10–13 | 10–12 | |||||
Pleurosigma sp. 1 | 189.4–225.5 | 20.7–20.8 | 13–15 | ||||||
Pleurosigma sp. 2 | 153.2–187.2 | 20.7–24.4 | 21–22 | ||||||
Porosira cf. glacialis | (Grunow) Jørgensen |
|
19.5–81.0 | 18–22 | |||||
Psammothidium germainii | (Manguin) Sabbe |
|
19.7 | 9.6 | 22 | ||||
Psammothidium germainioides (R) | Van de Vijver, Kopalová & Zidarova |
|
15.7 | 6.8 | 28 | ||||
Psammothidium incognitum | (Krasske) Van de Vijver |
|
13.8–16.3 | 5.0–5.6 | |||||
Psammothidium manguinii (R) | (Hustedt) Van de Vijver |
|
14.3 | 6.6 | 23 | 22 | |||
Psammothidium papilio | (D:E. Kellogg, M. Stuiver, T.B. Kellogg & G.H. Denton) Kopalová & Van de Vijver | Kopalova et al. 2012: p. 204, fig. 5Q–T; |
8.5–14.7 | 4.3–5.8 | 24–30 | 24–30 | |||
Psammothidium rostrogermainii | Van de Vijver, Kopalová & Zidarova |
|
16.0–19.3 | 8.1–8.8 | 16 | 18 | |||
Pseudogomphonema kamtschaticum | (Grunow) Medlin |
|
9.9–51.6 | 3.2–7.5 | 10–16 | ||||
Pteroncola carlinii | Almandoz & Ferrario |
|
5.0–23.4 | 2.5–3.3 | |||||
Rhabdonema sp. | 134.3–135.2 | 21.3–25.6 | 5–6 | ||||||
Rhoicosphenia michalii | Ligowski |
|
20.5–27.9 | 3.7–5.9 | 7–8 | ||||
Sabbea cf. adminii | (D.Roberts & McMinn) Van de Vijver, Bishop & Kopalová |
|
31.1–32.0 | 4.5–4.6 | |||||
Sellaphora jamesrossensis | (Kopalová, & Van de Vivjer) Van de Vivjer & C.E. Wetzel | as Eolimna jamesrossensis in Kopalová et al. 2009: p. 116, figs 15–33, |
11.8–14.2 | 5.5–6.0 | 20–22 | ||||
Shionodiscus gracilis var. expectus | (VanLandingham) Alverson, Kang et Theriot | as Thalassiosira gracilis var. expecta in |
9.9–13.6 | 14–18 | |||||
Stauroneis acidojarensis (R) | Zidarova, Kopalová & Van de Vijver |
|
45.2 | 9 | 22 | ||||
Stauroneis latistauros | Van de Vijver & Lange Bertalot |
|
26.4–35.1 | 7.4–8.4 | 20–24 | ||||
Stauroneis pseudomuriella (R) | Van de Vijver & Lange Bertalot | Vijver et al. 2004: p. 56, pl. 61; Zidarova et al. 2016: p. 330, pl. 150 | 21.4–29.9 | 4.8–5.0 | 22 | ||||
Staurosira pottiezii | Van de Vijver |
|
25.8 | 4.2 | 13 | ||||
Synedropsis cf. recta | Hasle, Medlin & Syvertsen |
|
6.4–54.7 | 3.0–6.9 | 9–15 | ||||
Thalassionema gelida | M.Peragallo |
|
63.1–153.5 | 3.5–6.3 | 10–11 | ||||
Thalassiosira antarctica | Comber |
|
29.0–44.6 | 13–15 | |||||
Thalassiosira scotia | Fryxell & Hoban |
|
21.9–29.1 | 8–9 | |||||
Trachyneis aspera | (Ehrenberg) Cleve |
|
94.0–188.7 | 17.5–31.7 | 7–8 | ||||
Trigonium arcticum | (Brightwell) Cleve |
|
123.0 | 3–4 | |||||
Tripterion cf. margaritae | (Frenguelli & Orlando ex Fernandes & Sar) Fernandes & Sar |
|
12.1–16.2 | 3.2–4.1 | 24–25 | ||||
Unidentified centric diatom | 2.8–4.5 | ||||||||
Unidentified pennate diatom | 12.4 | 3.0 | 12 |
The most abundant taxa (> 2% of all counts per habitat, Table
Most abundant taxa (> 2% of average abundance) across marine, brackish water and freshwater samples for morphology count (LM) and metabarcoding rbcL and 18SV4, AA: average abundance across the habitat, NA: not taxonomically assigned. Several ASVs were assigned to the same taxon through the metabarcoding pipeline.
LM | AA [%] | rbcL | AA [%] | 18SV4 | AA [%] |
---|---|---|---|---|---|
Marine samples | |||||
Navicula cf. perminuta | 51.8 | Navicula cf. perminuta | 13.3 | NA | 24.8 |
Minidiscus chilensis | 6.2 | Navicula cf. perminuta | 11.3 | Navicula cf. perminuta | 20.3 |
Navicula sp. 5 | 5.5 | NA | 11.0 | NA | 4.7 |
Pseudogomphonema kamtschaticum | 4.5 | NA | 6.3 | Paralia sol (syn. Ellerbeckia sol) | 4.6 |
Achnanthes vicentii | 3.1 | NA | 4.5 | NA | 4.4 |
Gyrosigma sp. | 2.8 | NA | 3.7 | Thalassiosira minima | 2.5 |
Synedropsis cf. recta | 2.2 | Navicula cf. perminuta | 3.2 | Navicula directa | 2.4 |
Cocconeis fasciolata | 2.2 | Minidiscus chilensis | 2.9 | ||
Navicula sp. | 2.9 | ||||
Licmophora cf. gracilis | 2.8 | ||||
NA | 2.5 | ||||
Ellerbeckia sp. | 2.2 | ||||
NA | 2.2 | ||||
Brackish water samples | |||||
Navicula gregaria | 52.3 | Navicula gregaria | 33.9 | Pinnularia australomicrostauron | 47.4 |
Navicula australoshetlandica | 13.3 | Navicula australoshetlandica | 11.7 | Navicula gregaria | 20.6 |
Chamaepinnularia australis | 7.1 | Nitzschia sp. | 8.8 | Navicula cf. veneta | 7.0 |
Nitzschia cf. gracilis | 6.2 | Pinnularia australomicrostauron | 6.7 | Nitzschia sp. | 4.1 |
Nitzschia sp. 6 | 6.0 | Navicula gregaria | 6.4 | Pinnularia australomicrostauron | 2.8 |
Halamphora ausloosiana | 5.3 | Chamaepinnularia australis | 5.2 | Pinnularia australomicrostauron | 2.6 |
Planothidium australe | 2.2 | NA | 5.1 | ||
Nitzschia cf. gracilis | 5.0 | ||||
Halamphora ausloosiana | 3.2 | ||||
Pinnularia australoglobiceps | 3.0 | ||||
Nitzschia sp. | 2.3 | ||||
Freshwater samples | |||||
Nitzschia annewillemsiana | 19.4 | Mayamaea sweetloveana | 13.6 | Pinnularia australomicrostauron | 28.1 |
Nitzschia kleinteichiana | 16.0 | Fragilaria sp. | 9.9 | Nitzschia cf. frustulum | 10.9 |
Mayamaea sweetloveana | 11.4 | Nitzschia cf. frustulum | 8.5 | Gomphonema maritimo-antarcticum | 7.7 |
Unidentified centric diatom | 10.8 | Nitzschia kleinteichiana | 8.3 | NA | 6.5 |
Nitzschia soratensis | 10.5 | Nitzschia sp. | 7.6 | Fragilaria sp. | 5.8 |
Psammothidium papilio | 7.0 | NA | 6.6 | Encyonema sp. | 3.4 |
Achnanthidium cf. maritimo-antarcticum | 6.1 | Nitzschia cf. gracilis | 6.1 | Planothidium rostrolanceolatum | 3.4 |
Fragilaria cf. parva | 4.6 | Encyonema sp. | 4.9 | Nitzschia cf. gracilis | 2.9 |
Planothidium quadripunctatum | 2.4 | Achnanthidium sp. | 4.2 | Achnanthidium sp. | 2.4 |
Planothidium rostrolanceolatum | 2.1 | Mayamaea cf. permitis | 3.6 | NA | 2.3 |
Nitzschia cf. gracilis | 2.0 | Gomphonema maritimo-antarcticum | 4.2 | Nitzschia sp. | 2.2 |
Planothidium rostrolanceolatum | 3.4 | Planothidium rostrolanceolatum | 2.2 | ||
Planothidium cf. pumilum | 2.6 | ||||
Nitzschia sp. | 2.0 |
A total of 162 clonal cultures were established, resulting in the identification of 60 taxa: 33 of those taxa could be identified to species level, 23 to genus level and 4 where the genus affiliation is inconclusive (Table
Taxa which were established as clonal cultures, strain numbers, in case of publication: reference and accession number.
Taxon | Strain | Voucher at BGBM | DNA Bank | Publication of strain | Accession number rbcL | Accession number 18SV4 |
---|---|---|---|---|---|---|
Achnanthes vicentii | D305_008 | B 40 0045332 | DB43189 | |||
D322_002 | B 40 0045222 | DB43092 | ||||
D326_020 | B 40 0045334 | DB43015 | ||||
Brachysira minor | D300_027 | B 40 0045258 | DB42968 | |||
D300_029 | B 40 0045305 | DB43129 | ||||
Chaetocerus cf. neogracilis | D305_007 | B 40 0046208 | DB43188 | |||
Chamaepinnularia australis | D294_001 | B 40 0045203 | DB43033 | ( |
OX386460 | OX386235 |
D294_002 | B 40 0045204 | DB43034 | ( |
OX386461 | OX386236 | |
D294_013 | B 40 0045208 | DB43043 | ( |
OX386464 | OX386239 | |
D294_014 | B 40 0045209 | DB43074 | ( |
OX386465 | OX386240 | |
Chamaepinnularia gerlachei | D294_005 | B 40 0045272 | DB43037 | ( |
OX386462 | OX386237 |
D294_006 | B 40 0045207 | DB43038 | ( |
OX386463 | OX386238 | |
D296_001 | B 40 0045355 | DB43045 | ( |
OX258987 | OX258985 | |
D296_002 | B 40 0045356 | DB43046 | ( |
OX386466 | OX386241 | |
D297_003 | B 40 0045277 | DB43047 | ( |
OX386467 | OX386242 | |
cf. Chamaepinnularia | D301_002 | B 40 0045342 | DB42990 | |||
Cocconeis fasciolata | D326_023 | B 40 0045353 | DB43018 | |||
cf. Cocconeis 1 | D301_001 | B 40 0045179 | DB42989 | |||
D301_009 | B 40 0045315 | DB42997 | ||||
cf. Cocconeis 2 | D326_035 | B 40 0045271 | DB43025 | |||
D326_037 | B 40 0045328 | DB43027 | ||||
D326_038 | B 40 0045350 | DB43028 | ||||
D326_039 | B 40 0045329 | DB43029 | ||||
Cylindrotheca cf. closterium | D322_018 | B 40 0046211 | DB43648 | Not available | ||
Fallacia marnieri | D301_003 | B 40 0045314 | DB42991 | This study | OR355374 | Not available |
D301_004 | B 40 0045217 | DB42992 | This study | OR355375 | OR352010 | |
D323_016 | B 40 0045268 | DB43144 | This study | Not available | OR352011 | |
D326_002 | B 40 0045167 | DB43001 | This study | OR355376 | OR352012 | |
D326_005 | B 40 0045169 | DB43003 | This study | OR355377 | OR352013 | |
D326_007 | B 40 0045199 | DB43005 | This study | OR355378 | OR352014 | |
D326_014 | B 40 0045235 | DB43010 | This study | OR355379 | OR352015 | |
D326_016 | B 40 0045236 | DB43012 | This study | OR355380 | OR352016 | |
D326_017 | B 40 0045346 | DB43013 | This study | OR355381 | OR352017 | |
D326_041 | B 40 0045367 | DB43209 | This study | OR355382 | OR352018 | |
Fragilaria cf. parva | D299_016 | B 40 0045214 | DB43076 | |||
D299_020 | B 40 0045279 | DB43080 | ||||
D299_026 | B 40 0045255 | DB43087 | ||||
D300_016 | B 40 0045284 | DB42962 | ||||
cf. Gedaniella | D291_001 | B 40 0045201 | DB43030 | |||
D293_001 | B 40 0045170 | DB43183 | ||||
D324_004 | B 40 0045231 | DB43205 | ||||
Gomphonema maritimo-antarcticum | D299_018 | B 40 0045245 | DB43078 | This study | OR355383 | OR352019 |
D299_021 | B 40 0045290 | DB43081 | This study | OR355384 | OR352020 | |
D299_028 | B 40 0045294 | DB43089 | This study | Not available | OR352021 | |
D300_013 | B 40 0045282 | DB42959 | This study | OR355385 | OR352022 | |
D300_014 | B 40 0045283 | DB42960 | This study | OR355386 | OR352023 | |
D314_002 | B 40 0045188 | DB42971 | This study | OR355387 | OR352024 | |
D314_004 | B 40 0045190 | DB42973 | This study | OR355388 | OR352025 | |
D314_014 | B 40 0045264 | DB42983 | This study | OR355389 | OR352026 | |
D314_019 | B 40 0045307 | DB42988 | This study | OR355390 | OR352027 | |
Halamphora ausloosiana | D294_007 | B 40 0045273 | DB43039 | This study | OR355391 | OR352028 |
D294_008 | B 40 0045274 | DB43040 | This study | OR355392 | OR352029 | |
Hantzschia hyperaustralis | D314_011 | B 40 0045306 | DB42980 | This study | OR355393 | OR352030 |
Humidophila sceppacuerciae | D300_002 | B 40 0045280 | DB42950 | This study | OR355394 | OR352031 |
D300_022 | B 40 0045302 | DB42965 | This study | OR355395 | OR352032 | |
Licmophora cf. gracilis | D308_002 | B 40 0045343 | DB43191 | |||
D308_003 | B 40 0045220 | DB43192 | ||||
D308_004 | B 40 0045316 | DB43193 | ||||
Lunella sp. | D292_010 | B 40 0045571 | DB43435 | |||
D309_004 | B 40 0045580 | DB43438 | ||||
D323_012 | B 40 0045228 | DB43140 | ||||
D326_015 | B 40 0045200 | DB43011 | ||||
Luticola higleri | D299_001 | B 40 0045311 | DB43062 | This study | OR355396 | OR352033 |
D299_010 | B 40 0045312 | DB43071 | This study | OR355397 | OR352034 | |
Luticola desmetii | D300_028 | B 40 0045313 | DB43128 | This study | OR355398 | OR352035 |
Mayamaea sweetloveana | D299_006 | B 40 0045175 | DB43067 | This study | OR355399 | OR352036 |
D299_007 | B 40 0045176 | DB43068 | This study | OR355400 | OR352037 | |
D299_009 | B 40 0045178 | DB43070 | This study | OR355401 | OR352038 | |
D304_001 | B 40 0045246 | DB42998 | This study | OR355402 | OR352039 | |
D304_002 | B 40 0045259 | DB42999 | This study | OR355403 | Not available | |
Mayamaea cf. permitis | D300_006 | B 40 0045241 | DB42969 | |||
D300_011 | B 40 0045256 | DB42958 | ||||
Melosira sp. | D323_018 | B 40 0045309 | DB43146 | ( |
OR036645 | OR042180 |
D323_019 | B 40 0045310 | DB43147 | ||||
Minidiscus chilensis | D323_014 | B 40 0045229 | DB43142 | This study | OR355404 | OR352040 |
D326_021 | B 40 0045325 | DB43017 | This study | OR355405 | OR352041 | |
Navicula australoshetlandica | D295_001 | B 40 0045460 | DB43327 | This study | OR355406 | Not available |
D300_018 | B 40 0045330 | DB43123 | This study | OR355407 | OR352042 | |
Navicula concordia | D310_004 | B 40 0045317 | DB43201 | ( |
OX258991 | OX259170 |
D310_002 | B 40 0045186 | DB43199 | This study | OR355408 | OR352043 | |
D310_003 | B 40 0045187 | DB43200 | This study | OR355409 | OR352044 | |
D310_006 | B 40 0045576 | DB43439 | This study | OR355410 | OR352045 | |
Navicula criophiliforma | D288_003 | B 40 0045335 | DB43182 | ( |
OX258986 | OX259166 |
D288_002 | B 40 0045247 | DB43181 | This study | OR355411 | OR352046 | |
D326_027 | B 40 0045237 | DB43021 | This study | OR355412 | OR352047 | |
D322_014 | B 40 0045380 | DB43102 | This study | OR355413 | OR352048 | |
Navicula directa | D326_001 | B 40 0045166 | DB43000 | This study | OR355414 | OR352049 |
Navicula gregaria | D294_003 | B 40 0045205 | DB43035 | This study | OR355415 | OR352050 |
D300_003 | B 40 0045281 | DB42951 | This study | OR355416 | OR352051 | |
D300_004 | B 40 0045296 | DB42952 | This study | OR355417 | OR352052 | |
D300_007 | B 40 0045216 | DB42954 | This study | OR355418 | OR352053 | |
Navicula cf. perminuta | D323_004 | B 40 0045159 | DB43133 | |||
D323_011 | B 40 0045322 | DB43139 | ||||
D326_010 | B 40 0045233 | DB43008 | ||||
D326_012 | B 40 0045234 | DB43009 | ||||
Navicula sp. 1 | D326_009 | B 40 0045232 | DB43007 | |||
Navicula sp. 4 | D307_001 | B 40 0045475 | DB43346 | Not available | ||
D310_007 | B 40 0045583 | DB43440 | Not available | |||
Navicula sp. 5 | D301_007 | B 40 0045242 | DB42969 | |||
D301_008 | B 40 0045331 | DB42996 | ||||
Navicula sp. 6 | D291_006 | B 40 0045474 | DB43320 | |||
Navicula sp. 13 | D310_001 | B 40 0045185 | DB43198 | |||
D326_006 | B 40 0045198 | DB43004 | ||||
D326_019 | B 40 0045347 | DB43014 | ||||
Nitzschia annewillemsiana | D300_012 | B 40 0045357 | DB43122 | ( |
OX258988 | OX259167 |
Nitzschia cf. gracilis | D299_014 | B 40 0045212 | DB43074 | |||
Nitzschia homburgiensis | D299_002 | B 40 0045172 | DB43063 | This study | OR355419 | OR352054 |
Nitzschia kleinteichiana | D314_005 | B 40 0045191 | DB42974 | This study | OR355420 | OR352055 |
D314_008 | B 40 0045194 | DB42977 | This study | OR355421 | OR352056 | |
Nitzschia medioconstricta | D309_001 | B 40 0045569 | DB43526 | This study | OR355422 | Not available |
D309_002 | B 40 0045577 | DB43527 | This study | OR355423 | Not available | |
Nitzschia soratensis | D300_026 | B 40 0045257 | DB42967 | This study | OR355424 | OR352057 |
Nitzschia sp. 3 | D322_015 | B 40 0045364 | DB43103 | |||
D322_016 | B 40 0045365 | DB43104 | ||||
Nitzschia sp. 4 | D310_008 | B 40 0045584 | DB43441 | Not available | ||
Nitzschia sp. 7 | D324_002 | B 40 0045165 | DB43203 | |||
Odontella litigiosa | D305_005 | B 40 0045181 | DB43186 | |||
D323_008 | B 40 0045163 | DB43137 | ||||
Pinnularia australoglobiceps | D294_004 | B 40 0045206 | DB43036 | |||
Pinnularia australomicrostauron | D299_005 | B 40 0045211 | DB43066 | |||
D314_001 | B 40 0045261 | DB42970 | ||||
D314_003 | B 40 0045189 | DB42972 | ||||
D314_010 | B 40 0045195 | DB42979 | ||||
D314_013 | B 40 0045263 | DB42982 | ||||
D314_017 | B 40 0045287 | DB42986 | ||||
Pinnularia cf. quadratarea | D324_001 | B 40 0045164 | DB43202 | |||
Pinnularia sp. | D322_010 | B 40 0045321 | DB43098 | Not available | ||
Planothidium australe | D294_010 | B 40 0045275 | DB43041 | This study | OR355425 | OR352058 |
D294_011 | B 40 0045276 | DB43042 | This study | OR355426 | OR352059 | |
D300_005 | B 40 0045297 | DB42953 | This study | OR355427 | OR352060 | |
Planothidium rostrolanceolatum | D299_003 | B 40 0045173 | DB43064 | This study | OR355428 | OR352061 |
D299_008 | B 40 0045177 | DB43069 | This study | OR355429 | OR352062 | |
D299_022 | B 40 0045252 | DB43082 | This study | OR355430 | OR352063 | |
D300_021 | B 40 0045286 | DB42964 | This study | OR355431 | OR352064 | |
D314_007 | B 40 0045193 | DB42976 | This study | OR355432 | OR352065 | |
Planothidium wetzelii | D300_015 | B 40 0045340 | DB42961 | ( |
OX258989 | OX259168 |
D300_019 | B 40 0045358 | DB43124 | ( |
OR036648 | OR042183 | |
D300_020 | B 40 0045301 | DB43125 | ( |
OR036647 | OR042182 | |
D300_025 | B 40 0045341 | DB42966 | ( |
OR036646 | OR042181 | |
Planothidium sp. | D326_029 | B 40 0045349 | DB43022 | Not available | ||
Pleurosigma sp. 2 | D293_002 | B 40 0045202 | DB43184 | |||
D322_007 | B 40 0045320 | DB43097 | ||||
D323_001 | B 40 0045226 | DB43130 | ||||
D323_002 | B 40 0045267 | DB43131 | ||||
D323_003 | B 40 0045227 | DB43132 | ||||
D324_003 | B 40 0045230 | DB43204 | ||||
D326_003 | B 40 0045197 | DB43002 | ||||
Porosira cf. glacialis | D308_005 | B 40 0045182 | DB43194 | |||
D323_005 | B 40 0045160 | DB43134 | ||||
Psammothidium papilio | D300_023 | B 40 0045303 | DB43126 | ( |
OX258990 | OX259169 |
D299_012 | B 40 0045238 | DB43072 | This study | OR355433 | OR352066 | |
D299_013 | B 40 0045239 | DB43073 | This study | OR355434 | OR352067 | |
Psammothidium papilio | D299_023 | B 40 0045291 | DB43083 | This study | OR355435 | OR352068 |
D299_024 | B 40 0045253 | DB43084 | This study | OR355436 | OR352069 | |
D299_025 | B 40 0045254 | DB43086 | This study | OR355437 | OR352070 | |
D300_001 | B 40 0045295 | DB43121 | This study | OR355438 | OR352071 | |
D300_010 | B 40 0045300 | DB42957 | This study | OR355439 | OR352072 | |
D314_015 | B 40 0045319 | DB42984 | This study | OR355440 | OR352073 | |
Stauroneis latistauros | D314_009 | B 40 0045318 | DB42978 | This study | OR355441 | OR352074 |
D314_016 | B 40 0045344 | DB42985 | This study | OR355442 | OR352075 | |
Surirella australovisurgis | D300_017 | B 40 0045285 | DB42963 | |||
Synedropsis cf. recta | D305_003 | B 40 0045180 | DB43185 |
From the 60 taxa, only six had a sequence record in the International Nucleotide Sequence Database Collaboration (INSDC) databases (DDBJ, EMBL–EBI and NCBI) and 54 are new sequenced taxa. Some sequences from our Antarctic cultures were already published with a thorough morphological examination and in two cases with the description of a new species (
LM pictures of taxa found by morphological analyses. A Brandinia charcotii. B Fragilaria cf. striatula. C Fragilaria cf. parva. D cf. Gedaniella. E Pteroncola carlinii. F Synedropsis cf. recta. G Staurosira pottiezii. H Unidentified pennate diatom. I Licmophora antarctica. J Licmophora belgicae. K Thalassionema gelida. L Rhabdonema sp. M Cocconeis pottercovei. N Cocconeis infirmata. O, P Cocconeis matsii. Q Entopyla ocellata. R Licmophora cf. gracilis. Scale bar: 10 µm.
LM pictures of taxa found by morphological analyses. A Achnanthes bongrainii. B Achnanthes vicentii. C Achnanthes sp. 1. D Achnanthes sp. 2. E Achnanthes sp. 4. F Achnanthes sp. 5. G Psammothidium rostrogermainii. H Achnanthes sp. 3. I Psammothidium germainii. J Psammothidium incognitum. K Achnanthidium australexiguum. L Psammothidium manguinii. M Planothidium wetzelii. N Achnanthidium cf. maritimo-antarcticum. O Psammothidium germainioides. P Planothidium rostrolanceolatum. Q Psammothidium papilio. R Planothidium quadripunctatum. S Planothidium sp. T cf. Cocconeis 2. U Planothidium australe. V Cocconeis melchioroides. W Cocconeis californica. X Australoneis frenguelliae. Y Cocconeis fasciolata. Z cf. Cocconeis 1. AA Cocconeis dallmannii. AB Cocconeis antiqua. AC Cocconeis imperatrix. AD Cocconeis costata. Scale bars: 10 µm (A–AA, AD); 30 µm (AB, AC).
LM pictures of taxa found by morphological analyses. A Navicula sp. 3. B Navicula sp. 12. C Navicula sp. 1. D Navicula sp. 5. E Navicula sp. 10. F Navicula criophiliforma. G Navicula sp. 2. H Navicula directa. I Trachyneis aspera. J Navicula concordia. K Navicula sp. 13. L Navicula glaciei. M Navicula gregaria. N Navicula sp. 14. O Navicula cf. perminuta. P Navicula sp. 8. Q Navicula cremeri. R Navicula sp. 11. S Navicula sp. 6. T Navicula sp. 7. U Navicula australoshetlandica. V Navicula cf. pagophila var. manitounukensis. W Sabbea cf. adminii. X Navicula sp. 9. Y Navicula sp. 4. Z Petroneis cf. plagiostoma. AA Petroneis sp. 2. AB Petroneis sp. 1. AC Berkeleya rutilans. AD Berkeleya cf. sparsa. AE Mayamaea sweetloveana. AF Mayamaea cf. permitis. AG Sellaphora jamesrossensis. AH Stauroneis acidojarensis. AI Stauroneis latistauros. AJ Stauroneis pseudomuriella. AK Diploneis sp. AL Fallacia marnieri. AM Placoneis australis. AN Lunella sp. AO Humidophila sceppacuerciae. AP Brachysira minor. AQ Humidophila tabellariaeformis. AR Hippodonta hungarica. Scale bar: 10 µm.
LM pictures of taxa found by morphological analyses. A Luticola cf. truncata. B Luticola cf muticopsis. C Luticola desmetii. D Luticola higleri. E Luticola austroatlantica. F Luticola australomutica. G Parlibellus cf. schuetii. H Pinnularia borealis. I Pinnularia australorabenhorstii. J Pinnularia sp. K Pinnularia australomicrostauron. L Biremis ambigua. M Pinnularia cf. quatratarea. N Pinnularia australoglobiceps. O Pinnularia parallelimarginata. P Pinnularia subantarctica var. elongata. Q Caloneis australis. R cf. Chamaepinnularia. S Chamaepinnularia australis. T Chamaepinnularia gerlachei. U Pseudogomphonema kamtschaticum. V Gomphonema maritimo-antarcticum. W Rhoicosphenia michalii. X Gomphonemopsis ligowskii. Y Tripterion cf. margaritae. Z Encyonema ventricosum. AA Halamphora cf. staurophora. AB cf. Halamphora. AC Amphora gourdonii. AD Amphora sp. AE Halamphora cf. veneta. AF Halamphora sp. 2. AG Halamphora sp. 3. AH Halamphora ausloosiana. AI Amphora cf. pusio. AJ Halamphora sp. 1. AK Halamphora lineata. Scale bar: 10 µm.
LM pictures of taxa found by morphological analyses. A Nitzschia cf. hybrida. B Nitzschia medioconstricta. C Nitzschia sp. 4. D Nitzschia sp. 3. E Nitzschia sp. 5. F Pleurosigma sp. 2. G Pleurosigma sp. 1. H Gyrosigma tenuissimum var. angustissimum. I Gyrosigma sp. J Nitzschia sp. 6. K Nitzschia sp. 7. L Nitzschia sp. 2. M Nitzschia homburgiensis. N Nitzschia cf. gracilis. O Nitzschia kleinteichiana. P Nitzschia sp. 1. Q Nitzschia soratensis. R Nitzschia annewillemsiana. S Entomoneis sp. T Hantzschia cf. virgata. U Hantzschia amphioxys. V Hantzschia hyperaustralis. W Gyrosigma cf. fasciola. X Surirella australovisurgis. Y Fragilariopsis kerguelensis. Z Fragilariopsis curta. AA Fragilariopsis separanda. AB Fragilariopsis cylindrus. AC Fragilariopsis rhombica. Scale bars: 10 µm (A–E, J–U, X–AC); 30 µm (F–I, U, V).
Sequences of taxa, where identification was possible, were submitted to GenBank. The other sequences will be published when a thorough morphological description of the species has been performed. Those sequences can be retrieved from the DNA Databank of the Botanic Garden Berlin after personal communication.
The Illumina MiSeq sequencing run generated 7,460,203 reads for the rbcL marker and 5,623,490 reads for the 18S V4 marker. After processing the reads through the DADA2 pipeline and improvement of the dataset by metbaR for rbcL 7,381,429 reads remained belonging to 1,041 ASVs and for 18S V4 5,570,517 reads remained belonging to 2,251 ASVs.
For the rbcL marker 6,002,917 of reads and 810 of ASVs belong to diatoms corresponding to 81.3% and 77.8% respectively. The majority of the non–diatom reads were assigned to green and brown algae. The average number of diatom–ASVs per sample ranged between 24 and 135. Of all ASVs, 283 could be assigned to a species in the reference library, whereby several ASVs were assigned to the same species and additional 156 ASVs could be assigned to genus level. In the marine samples, 611 ASVs were found; 292 ASVs could be assigned to genus level (47.8%) and 190 to species level (31.1%). In the freshwater samples, 216 ASVs were recovered; 152 could be assigned to genus level (70.4%) and 96 to species level (44.4%). Finally in the brackish water samples 52 ASVs were found; 38 could be assigned to genus level (73.0%) and 25 to species level (48.1%).
The most abundant taxa (sequence relative abundance ≥ 2%, Table
For the 18S V4 marker 2,835,064 of reads and 1,439 of ASVs belong to diatoms corresponding to 50.8% and 63.9% respectively. Here as well, the majority of the non–diatom reads were assigned to green and brown algae. The average number of diatom–ASVs per sample ranged between 5 and 248. Of all ASVs 344 could be assigned to a species in the reference library, whereby several ASVs were assigned to the same species and additional 348 could be assigned to genus level. In the marine samples, 1090 ASVs were found; 462 ASVs could be assigned to genus level (42.4%) and 207 to species level (19.0%). In the freshwater samples, 300 ASVs were recovered; 211 could be assigned to genus level (70.3%) and 131 to species level (43.3%). Finally, in the brackish water samples 107 ASVs were found; 60 could be assigned to genus level (56.1%) and 36 to species level (33.6%).
The most abundant taxa (sequence relative abundance ≥ 2%, Table
In the clonal cultures 60 taxa could be identified, but 51 of them were also found in the microscopy examinations of environmental samples, which means that 9 taxa were only retrieved through culturing (Lunella sp., cf. Cocconeis 2, Chaetocerus cf. neogracilis, Cylindrotheca cf. closterium, Melosira sp., Navicula sp.1, Nitzschia sp.3, Pinnularia sp., Surirella australovisurgis Van de Vijver, Cocquyt, Kopalová & Zidarova, Fig.
Venn diagrams comparing the performance of morphology and DNA metabarcoding in diatom identifications. A Morphological richness across all environmental samples and clonal cultures, M: infrageneric taxa identified by counting 400 valves per sample under light microscopy (LM), C: infrageneric taxa identified from clonal cultures, MR: infrageneric taxa identified by scanning LM slide for rare species. B Genera identified by morphology (Mor) and metabarcoding with the rbcL and 18SV4 marker gene. C Infrageneric taxa identified by morphology including rare taxa (Mor) and metabarcoding with the rbcL and 18SV4 marker gene (only assigned taxa to species level from metabarcoding shown).
The relative abundances on genus level shows that in general the same genera per samples are retrieved between the three datasets (Fig.
Average taxa richness across water and substratum type was always higher in the metabarcoding inventories than in LM (Table
Average taxa Richness and Shannon diversity index across water and substratum types with the morphological and DNA metabarcoding inventories (rbcL and 18SV4).
LM | rbcL | 18SV4 | ||||
Taxa richness | Shannon index | Taxa richness | Shannon index | Taxa richness | Shannon index | |
Marine, biofilm from stones | 10 | 0.8 | 58 | 1.9 | 39 | 1.3 |
Freshwater, biofilm from stones | 12 | 1.1 | 42 | 1.8 | 58 | 2.1 |
Marine, epipsammic biofilm | 43 | 2.8 | 73 | 2.0 | 164 | 2.5 |
Brackish water, epipsammic biofilm | 16 | 1.6 | 40 | 2.2 | 80 | 1.9 |
The NMDS plots for morphology, rbcL and 18SV4 inventories show a clear separation in the community composition of samples taken from marine and freshwater habitats (Fig.
NMDS multivariate clustering of benthic diatom communities regarding water type and substratum type. A Morphology. B rbcL marker gene. C 18SV4 marker gene. Stress: 0.1 (A–C).
According to the SIMPER results (Suppl. material
This study demonstrated that the shallow coastal zone of Potter Cove harbours a rich diatom community with a total of 116 marine taxa identified by morphological investigation. Two floristic studies on benthic diatoms were already performed in Potter Cove by
Even though fewer freshwater samples in our study were evaluated, 93 taxa were still found in these habitats. In general, many more studies investigating freshwater rather than marine habitats in Antarctica have been performed to date. Floristic studies found 122 taxa on King George Island/Isla 25 de Mayo (
This study demonstrated that DNA metabarcoding presents an efficient method for surveying diatom biodiversity in coastal and freshwater ecosystems as it recorded a similar number of genera as the LM method with a high proportion of the genera identified by both methods. However, there are some discrepancies between the inventories. Some genera and species (23 and 73, respectively) were exclusively identified by DNA metabarcoding. DNA metabarcoding based on both marker genes retrieved a higher number of ASVs than taxa identified by LM. Several ASVs, however, were then assigned to the same taxon by the metabarcoding pipeline. Due to the incompleteness of the reference library the number of assigned species was lower for both marker genes in the metabarcoding approach compared to the LM approach which showed a greater efficiency for identifying taxa at species level.
Despite those restraints, similarity analyses of morphological as well as molecular data led to the same results. There was a clear statistically significant separation of diatom community according to water and substratum type. Based on all three approaches marine communities differ from freshwater communities and the brackish water communities are more similar to the freshwater ones. In addition, substratum type (sand or stones) seems to be a factor leading to dissimilarities in the diatom community as well. However, species contributing most to the dissimilarities between habitats differed, due to discrepancies in the inventories, which are discussed later.
60 diatom species were cultured and helped assign 47 taxa in our metabarcoding dataset because their sequence data were new to science. In the case of 27 taxa, sequence data was uploaded to ENA or GenBank in this or previous studies analysing the data from the same sampling campaign. Taxa, where a taxonomic investigation is still needed, will be published in combination with their sequence data, when a thorough taxonomic treatment is completed. Many of them will probably be described as new. In advance, their data is available at the Herbarium Berolinense. The large fraction of unidentified taxa especially in the marine habitat (∼68%) is not surprising since benthic diatoms were not broadly studied in this habitat.
Interestingly, some taxa established in culture were not observed in the morphological inventory. This was already shown in Mexican and Canadian streams in
The multitude of successfully grown taxa indicates that our approach using several culture media with different salinities was suitable for culturing benthic diatoms from Potter Cove. Even though an extensive culturing effort was undertaken, many taxa could not be established as a unialgal culture. They were not observed as living cells in our enrichment culture as they might not be sampled alive, culture conditions were not suitable, or long–distance shipment might have destroyed more delicate species. Furthermore, some taxa were not able to grow after single cell isolation or the unialgal culture died before enough material was available for analysis. Therefore, an increased diversity of culture media and variation of culture conditions (e.g., temperature, agitation, light intensity or day/night cycle) could potentially stimulate the growth of additional less competitive species and thus improve culture success.
In our metabarcoding dataset many of the taxa could not be assigned by the reference library, even on genus level. This is especially true for marine habitats. The reference library established from the sequence database from the Herbarium Berolinense comprises mostly freshwater diatoms and already
Several discrepancies between the morphological and the molecular inventory were evident. Most obvious was the above discussed fact, that many species and some genera were not encountered in the molecular inventory since the reference database was lacking a representative sequence. This was the case for e.g. Gyrosigma sp., Pteroncola carlinii Almandoz & Ferrario or Achnanthidium cf. maritimo–antarcticum listed with a relative high abundance in the LM inventory but without an entry for both metabarcoding inventories since both barcode sequences are unknown. Furthermore, some samples, where a high abundance of taxa in LM identified to the genera like Navicula and Gyrosigma, had no corresponding match in the metabarcoding inventories. This is indeed surprising, since those genera have a rather intensive representation in the reference databases. Studies in the last decades have shown that taxa morphologically assigned to an existing genus in Antarctica had been actually force fitted. Several new genera in the Antarctic or southern hemisphere have been established and existing taxa underwent a new combination (
One of the key issues concerning sediment DNA metabarcoding is the distinction of living organisms that are part of the active benthic community from those organisms that are represented either by inactive resting stages or solely by DNA traces (
Varying gene copy numbers per organism due to cell size and number of chloroplasts per cell is probably another reason for discrepancies between the LM and metabarcoding inventory. This correlation was noted in the case of rbcL by
The poor representation of Cocconeis in the rbcL inventory (1025 reads, 2 ASVs) despite the very high diversity of Cocconeis species revealed by LM was also an issue in the study of Burillo et al. 2022. Sequences of the Antarctic species C. fasciolata were available in our reference database as a culture of this species was established. No ASVs were assigned to this taxon in the rbcL inventory in contrast to the 18SV4 inventory. A worrying possibility is that primers of the rbcL barcode might not be suitable for marine Cocconeis. In fact, in comparable freshwater studies C. placentula was the most abundant taxon (
In general, the list of taxa with the highest relative abundance of the LM data set correlates better with the rbcL than with the 18SV4 inventory. Similar results were found by
It has been shown that the metabarcoding approach can complement and improve traditional identification via LM. It enables to detect tiny and delicate species. Lunella sp. and Cylindrotheca cf. closterium were detected in metabarcoding but not via the count of valves in LM. Rare species may be detected as well. In traditional identification, generally a few hundred valves are counted per sample probably not reaching saturation of species richness, while in metabarcoding several 10,000 to 100,000 reads are usually evaluated. Furthermore, it may detect cryptic diversity. Species that are morphologically similar may be better separated in the metabarcoding dataset.
In addition to the extension of information about Antarctic diatom diversity, our study also provided a new tool to survey water quality changes in Antarctica. In recent decades, climate change has had a crucial impact in the polar regions with increasing air and water temperature leading to glacial melting and the accompanying freshwater increase in coastal areas (
Antarctica is among the most extreme environments on Earth. An increased research effort is required in the light of desynchrony between the pace of change in polar regions and information demands to face engendered challenges (
The slides of the environmental samples, morphological and molecular data gained by LM and SEM investigation as well as sequencing of cultures together with the metabarcoding dataset represents the currently most extensive biodiversity dataset of marine benthic diatoms of Western Antarctica. All voucher material as well as the data are deposited at the Herbarium Berolinense and could be used as a baseline for further investigations, as a reference for monitoring routines and as training records in modelling tasks.
We would like to express our deep gratitude to Professor Andrzej Witkowski who has provided constructive comments improving this research. He was a prominent scientist and specialist of marine diatoms. He was always a great supporter for early career scientists as well as a great cooperation partner. His invaluable contribution and commitment to diatom science will be remembered. We would like to thank the team of the Argentinian Antarctic Research Station “Carlini” of the Instituto Antártico Argentino (IAA) for their support and logistics, especially Dr. María Liliana Quartino. The authors are grateful to Jana Bansemer for work in the molecular lab and to Juliane Bettig for support at the SEM at the BGBM Berlin.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This project was funded within the framework of the SPP 1158 Antarktisforschung by the DFG under the grant number ZI 1628/2–1. OS acknowledges funding from the Verein der Freunde des Botanischen Gartens und des Botanischen Museums Berlin-Dahlem e.V.. GC acknowledges support from PADI Foundation (47918/2020), ANPCyT–DNA (PICT 2017–2691), UNLu (DCDD–CB 343/19 and 69/21) and the EU’s H2020 research and innovation programme under the Marie Skłodowska–Curie grant agreement No 87269 CoastCarb. We acknowledge support by the Open Access Publication Fund of the Freie Universität Berlin.
KS and JZ developed the concept of this study. JZ and GC sampled and OS isolated, purified and established clonal cultures. KS, HM and JZ performed the metabarcoding analysis. KS provided the light microscopic analysis and KS, NA and RJ did the taxonomic identification. NA and WHK are responsible for the curation and data curation. KS wrote the first version of the paper. All authors edited and approved the final version of this manuscript.
Katherina Schimani https://orcid.org/0000-0003-2125-0239
Nélida Abarca https://orcid.org/0000-0001-8897-160X
Oliver Skibbe https://orcid.org/0000-0003-1495-5468
Heba Mohamad https://orcid.org/0000-0002-3217-3067
Regine Jahn https://orcid.org/0000-0002-3833-3746
Wolf-Henning Kusber https://orcid.org/0000-0003-4543-5764
Gabriela Laura Campana https://orcid.org/0000-0002-6507-2369
Jonas Zimmermann https://orcid.org/0000-0002-0522-0569
All of the data that support the findings of this study are available in the main text or Supplementary Information. Raw demultiplexed reads were deposited at GenBanks Sequence Read Archive and are publicly available under project number PRJNA997374.
Statistic results
Data type: docx
Explanation note: table S1. Taxa Richness and Shannon diversity of the sample sites with the morphological and DNA metabarcoding inventories (rbcL and 18SV4). table S2. SIMPER results listing the four most contributing species or ASV’s to the dissimilarities between samples taken from different water types (freshwater, brackish water and marine) and substratum types (epipsammic biofilm, biofilm on rocks) for the LM, the rbcL and the 18SV4 inventories, CC: Cumulative contribution to dissimilarity, AA: Average abundance across all samples.