Nitrogen fixation and diversity of benthic cyanobacterial mats on coral reefs in Curaçao

Hannah J. Brocke , Bastian Piltz , Nicole Herz , Raeid M. M. Abed , Katarzyna Palińska , Uwe John , Joost den Haan , Dirk de Beer , Maggy M. Nugues

Abstract

Benthic cyanobacterial mats (BCMs) have increased in abundance on coral reefs worldwide. However, their species diversity and role in nitrogen fixation are poorly understood. We assessed the cyanobacterial diversity of BCMs at four coral reef sites in Curaçao, Southern Caribbean. In addition, nitrogen fixation rates of six common mats were measured. Microscopic examinations showed 22 cyanobacterial species, all from the order Oscillatoriales. Species diversity was similar among sites despite differences in overall BCM abundance. Dominant mats were primarily composed of Hydrocoleum glutinosum, Oscillatoria bonnemaisonii or Lyngbya majuscula. However, some mats exhibited highly variable species composition despite consistent macroscopic appearance. 16S rRNA-based phylogeny revealed similar species as those identified by microscopy, with additional sequences of unicellular (Xenococcus and Chroococcidiopsis) and heterocystous (Rivularia and Calothrix) cyanobacteria. Vice versa, morphotypes of Tychonema, Schizothrix and Dichothrix were found by microscopy only. The detection of similar species at the same sites in a study conducted 40 years ago indicates that changes in environmental conditions over these years may have favored indigenous species to bloom, rather than facilitated the introduction and proliferation of invasive species. Nitrogen fixation rates of mats were 3–10 times higher in the light than in the dark. The highest areal nitrogen fixation rate (169.1 mg N m−2 d−1) was recorded in the cyanobacterial patch dominated by O. bonnemaisonii. A scale-up of nitrogen fixation at a site with 26% BCM cover at 7 m depth yielded an aerial rate of 13 mg N m−2 reef d−1, which exceeds rates reported in open ocean blooms of Trichodesmium in the Caribbean. Our results suggest that the Caribbean basin is not only a hotspot for planktonic nitrogen fixation, but also for benthic nitrogen fixation. Because BCMs fix vast amounts of nitrogen, their proliferation will strongly alter the nitrogen budget of coral reefs.
Author Hannah J. Brocke
Hannah J. Brocke,,
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, Bastian Piltz
Bastian Piltz,,
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, Nicole Herz
Nicole Herz,,
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, Raeid M. M. Abed
Raeid M. M. Abed,,
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, Katarzyna Palińska (FOG / IO / DMBE)
Katarzyna Palińska,,
- Department of Marine Biology and Ecology
, Uwe John
Uwe John,,
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, Joost den Haan
Joost den Haan,,
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, Dirk de Beer
Dirk de Beer,,
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, Maggy M. Nugues
Maggy M. Nugues,,
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Journal seriesCoral Reefs, ISSN 0722-4028, (A 45 pkt)
Issue year2018
Vol37
No3
Pages861-874
Publication size in sheets0.65
Keywords in Englishcyanobacterial mats, coral reef, nitrogen fixation, diversity, blue-green algae
DOIDOI:10.1007/s00338-018-1713-y
URL https://doi.org/10.1007/s00338-018-1713-y
Languageen angielski
LicenseOther; published final; Uznanie Autorstwa (CC-BY); with publication
Score (nominal)45
ScoreMinisterial score = 45.0, 05-11-2018, ArticleFromJournal
Ministerial score (2013-2016) = 45.0, 05-11-2018, ArticleFromJournal
Publication indicators WoS Impact Factor: 2016 = 2.906 (2) - 2016=3.565 (5)
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