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https://doi.org/10.5194/bg-2019-484
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-484
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 21 Jan 2020

Submitted as: research article | 21 Jan 2020

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This preprint is currently under review for the journal BG.

Dynamics of environmental conditions during a decline of a Cymodocea nodosa meadow

Mirjana Najdek1, Marino Korlević1, Paolo Paliaga2, Marsej Markovski1, Ingrid Ivančić1, Ljiljana Iveša1, Igor Felja3, and Gerhard J. Herndl4,5 Mirjana Najdek et al.
  • 1Center for Marine Research, Ruđer Bošković Institute, G. Paliaga 5, 52210 Rovinj, Croatia
  • 2Department of Natural and Health Sciences, University of Pula, Zagrebačka 30, 52100 Pula, Croatia
  • 3Department of Geology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia
  • 4Limnology and Bio-Oceanography, Center of Functional Ecology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
  • 5NIOZ, Department of Marine Microbiology and Biogeochemistry, Royal Netherlands Institute for Sea Research, Utrecht University, P.O. Box 59, Alberta, Den Burg, 1790, The Netherlands

Abstract. The dynamics of the physicochemical and biological parameters were followed during the decline of a Cymodocea nodosa meadow in the northern Adriatic Sea from July 2017 to October 2018. During the regular growth of C. nodosa from July 2017 to March 2018, C. nodosa successfully adapted to the changes of environmental conditions and prevented H2S accumulation by its re-oxidation, supplying the sediment with O2 from the water column and/or leaf photosynthesis. The C. nodosa decline was most likely triggered in April 2018 by a reduction of light availability which affected photosynthesis of C. nodosa and the oxidation capability of below-ground tissue. Simultaneously, a depletion of oxygen due to intense oxidation of H2S occurred in the sediment, thus creating anoxic conditions in most of the rooted areas. These linked negative effects on the plant performance caused an accumulation of H2S in the sediments of the C. nodosa meadow. During the decay of above- and below-ground tissues, culminating in August 2018, high concentrations of H2S were reached and accumulated in the sediment as well as in bottom waters. The influx of oxygenated waters in September 2018 led to the re-establishment of H2S oxidation and recovery of the below-ground tissue. Our results indicate that if disturbance of environmental conditions, particularly those compromising the light availability, take place during the recruitment phase of plant growth when metabolic needs are at maximum and stored reserves minimal, a sudden and drastic decline of the seagrass meadow occurs.

Mirjana Najdek et al.

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Mirjana Najdek et al.

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Short summary
The response of Cymodocea nodosa to environmental changes was reported during a 15-month period. The meadow decline was triggered in spring by the simultaneous reduction of available light in the water column and the creation of anoxic conditions in the rooted area. This disturbance was critical for the plant since it took place during its recruitment phase when metabolic needs are at maximum and stored reserves minimal. The loss of such habitat-forming seagrass is a major environmental concern.
The response of Cymodocea nodosa to environmental changes was reported during a 15-month period....
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