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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2018-512
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2018-512
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 28 Mar 2019

Research article | 28 Mar 2019

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Biogeosciences (BG) and is expected to appear here in due course.

Light-dependent calcification in Red Sea giant clam Tridacna maxima

Susann Rossbach, Vincent Saderne, Andrea Anton, and Carlos M. Duarte Susann Rossbach et al.
  • Biological and Environmental Science and Engineering Division, Red Sea Research Centre (RSRC) and Computational Bioscience Research Center (CBRC), King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia

Abstract. Tropical giant clams of the Tridacninae family, including the species Tridacna maxima, are unique among bivalves as they live in a symbiotic relationship with unicellular algae and generally function as net photoautotrophic. Light is therefore crucial for these species to thrive. Here we examine the light-dependency of calcification rates of T. maxima in the Central Red Sea as well as the patterns of its abundance with depth in the field. Red Sea T. maxima show highest densities in a depth of 3 m with 0.82 ± 0.21 and 0.11 ±  0.03 individuals m−2 (mean ± SE) at sheltered and exposed sites, respectively. Experimental assessment of net calcification (μmol CaCO3 cm−2 h−1) and gross primary production (μmol O2 cm−2 h−1) under seven light levels (1061, 959, 561, 530, 358, 244 and 197 μmol quanta m−2 s−1) showed net calcification rates to be significantly enhanced under light intensities corresponding to a water depth of 4 m (0.65 ± 0.03 μmol CaCO3 cm−2 h−1; mean ± SE), while gross primary production was 2.06 ± 0.24 μmol O2 cm−2 h−1 (mean ± SE). We found a quadratic relationship between net calcification and tissue dry-mass (DM in gram), with clams of an intermediate size (about 15 g DM), showing the highest calcification. Our results show that the Red Sea giant clam T. maxima stands out among bivalves as a remarkable calcifier, displaying calcification rates comparable to other tropical photosymbiotic reef organism, such as corals.

Susann Rossbach et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Susann Rossbach et al.
Susann Rossbach et al.
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Short summary
Giant clams, including the species Tridacna maxima, are unique among bivalves as they live in a symbiosis with unicellular algae and generally function as net photoautotrophs. Light is therefore crucial for these species to thrive. We show that net calcification and photosynthetic rates of T. maxima are light-dependent, with maximum rates at conditions comparable 3 m water depth, reflected also in its depth-related distribution in Red Sea, with maximum abundances in shallow, sunlit coral reefs.
Giant clams, including the species Tridacna maxima, are unique among bivalves as they live in a...
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