The carbon and nitrogen budget of Desmophyllum dianthus-a voracious cold-water coral thriving in an acidified Patagonian fjord

Sandra R Maier; Carin Jantzen; Jürgen Laudien; Verena Häussermann; Günter Försterra; Astrid Cornils; Jutta Niggemann; Thorsten Dittmar; Claudio Richter

doi:10.7717/peerj.12609

The carbon and nitrogen budget of Desmophyllum dianthus-a voracious cold-water coral thriving in an acidified Patagonian fjord

PeerJ. 2021 Dec 9:9:e12609. doi: 10.7717/peerj.12609. eCollection 2021.

Authors

Sandra R Maier^{1

2}, Carin Jantzen¹, Jürgen Laudien¹, Verena Häussermann^{3

4}, Günter Försterra⁵, Astrid Cornils¹, Jutta Niggemann⁶, Thorsten Dittmar^{6

7}, Claudio Richter^{1

8}

Affiliations

¹ Department of Biosciences, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany.
² Department of Estuarine and Delta Systems, Royal Netherlands Institute for Sea Research (NIOZ-Yerseke), Yerseke, Netherlands.
³ Facultad de Economía y Negocios, Universidad San Sebastián, Puerto Montt, Chile.
⁴ Huinay Foundation, Puerto Montt, Chile.
⁵ Escuela de Ciencias del Mar, Facultad de Recursos Naturales, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
⁶ Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Oldenburg, Germany.
⁷ Helmholtz Institute for Functional Marine Biodiversity (HIFMB), University of Oldenburg, Oldenburg, Germany.
⁸ Department of Biology/Chemistry, University of Bremen, Bremen, Germany.

Abstract

In the North Patagonian fjord region, the cold-water coral (CWC) Desmophyllum dianthus occurs in high densities, in spite of low pH and aragonite saturation. If and how these conditions affect the energy demand of the corals is so far unknown. In a laboratory experiment, we investigated the carbon and nitrogen (C, N) budget of D. dianthus from Comau Fjord under three feeding scenarios: (1) live fjord zooplankton (100-2,300 µm), (2) live fjord zooplankton plus krill (>7 mm), and (3) four-day food deprivation. In closed incubations, C and N budgets were derived from the difference between C and N uptake during feeding and subsequent C and N loss through respiration, ammonium excretion, release of particulate organic carbon and nitrogen (POC, PON). Additional feeding with krill significantly increased coral respiration (35%), excretion (131%), and POC release (67%) compared to feeding on zooplankton only. Nevertheless, the higher C and N losses were overcompensated by the threefold higher C and N uptake, indicating a high assimilation and growth efficiency for the krill plus zooplankton diet. In contrast, short food deprivation caused a substantial reduction in respiration (59%), excretion (54%), release of POC (73%) and PON (87%) compared to feeding on zooplankton, suggesting a high potential to acclimatize to food scarcity (e.g., in winter). Notwithstanding, unfed corals 'lost' 2% of their tissue-C and 1.2% of their tissue-N per day in terms of metabolism and released particulate organic matter (likely mucus). To balance the C (N) losses, each D. dianthus polyp has to consume around 700 (400) zooplankters per day. The capture of a single, large krill individual, however, provides enough C and N to compensate daily C and N losses and grow tissue reserves, suggesting that krill plays an important nutritional role for the fjord corals. Efficient krill and zooplankton capture, as well as dietary and metabolic flexibility, may enable D. dianthus to thrive under adverse environmental conditions in its fjord habitat; however, it is not known how combined anthropogenic warming, acidification and eutrophication jeopardize the energy balance of this important habitat-building species.

Keywords: Comau Fjord; Deep-sea corals; Energy budget; Feeding; Krill; Mucus; Ocean acidification; Respiration; Scleractinian corals; Zooplankton.

Grants and funding

The study was funded by the German Federal Ministry for Research and Education through the project “ERRINA” to Jürgen Laudien and Claudio Richter (“B project CHL08/001”), by AWI (“PACES T1WP6”) to Sandra R Maier, Carin Jantzen, Jürgen Laudien and Claudio Richter; “Changing Earth –Sustaining our Future, Subtopics 6.1 and 4.2” to Astrid Cornils, Jürgen Laudien and Claudio Richter), by the National Fund for Scientific and Technological Development (FONDECYT projects 1150843 and 1201717) to Günter Försterra and Verena Häussermann, and by a Brede-Foundation travel grant to Sandra R Maier. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.