Dissolved organic matter uptake balances carbon budgets of Red Sea bivalves and ascidians
6 affiliations
- 1Department of Evolution, Systematics and Ecology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
- 2Faculty of Marine Sciences, Ruppin Academic Center, Mikhmoret 4029700, Israel
- 3The Interuniversity Institute for Marine Sciences in Eilat, Eilat 8810302, Israel
- 4School of Zoology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 6997801, Israel
- 5Department of Marine Ecology, University of Bremen, Bremen 28359, Germany
- 6Bermuda Institute of Ocean Sciences, Arizona State University, St. Georges GE01, Bermuda
Abstract
Benthic suspension feeders have long been thought to depend solely on particulate organic matter (POM) for their nutritional needs. Our research, conducted in the Gulf of Aqaba (Red Sea), shows that the available concentration of planktonic carbon in the reef water is too low to meet the metabolic demands (measured through in situ oxygen uptake) of common bivalves (Spondylus sp. and Chama pacifica) and ascidians (Polycarpa mytiligera and Halocynthia spinosa). In situ measurements confirmed a concentration-dependent uptake of bulk dissolved organic carbon (DOC) and protein-like dissolved organic compounds (fDOM, analyzed via spectrofluorometry) by Spondylus sp. and P. mytiligera, suggesting that DOC uptake may balance their carbon budgets. Stable isotope (δ13C) mixing models indicate that reef-derived DOC (mean δ13C = −18.4 ± 0.7‰) emerges as the primary carbon source for bivalves (57% of their body composition), far surpassing contributions from particulate sources (26% from POC > 100 µm and 14% from POC < 100 µm). While ascidians still rely primarily on POM (60 to 71%), DOC plays an essential role as a supplementary food source (23 to 29%). These results challenge the prevailing assumption that POM is the exclusive food source for these organisms. Given the widespread presence of bivalves and ascidians in benthic habitats, our findings highlight their ability to bypass the microbial loop and directly utilize dissolved organic compounds, prompting a reevaluation of current benthic carbon budgets.
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BibTeX
@article{diga2026dissolved,
title = {{Dissolved organic matter uptake balances carbon budgets of Red Sea bivalves and ascidians}},
author = {Rei Diga and Tal Amit and Benjamin Mueller and Amatzia Genin and Craig A. Carlson and Gitai Yahel},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
year = {2026},
month = oct,
doi = {10.1073/pnas.2606052123},
url = {https://doi.org/10.1073/pnas.2606052123},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Dissolved organic matter uptake balances carbon budgets of Red Sea bivalves and ascidians
AU - Rei Diga
AU - Tal Amit
AU - Benjamin Mueller
AU - Amatzia Genin
AU - Craig A. Carlson
AU - Gitai Yahel
PY - 2026
DA - 2026/10/28
JO - Proceedings of the National Academy of Sciences of the United States of America
DO - 10.1073/pnas.2606052123
UR - https://doi.org/10.1073/pnas.2606052123
AB - Benthic suspension feeders have long been thought to depend solely on particulate organic matter (POM) for their nutritional needs. Our research, conducted in the Gulf of Aqaba (Red Sea), shows that the available concentration of planktonic carbon in the reef water is too low to meet the metabolic demands (measured through in situ oxygen uptake) of common bivalves (Spondylus sp. and Chama pacifica) and ascidians (Polycarpa mytiligera and Halocynthia spinosa). In situ measurements confirmed a concentration-dependent uptake of bulk dissolved organic carbon (DOC) and protein-like dissolved organic compounds (fDOM, analyzed via spectrofluorometry) by Spondylus sp. and P. mytiligera, suggesting that DOC uptake may balance their carbon budgets. Stable isotope (δ13C) mixing models indicate that reef-derived DOC (mean δ13C = −18.4 ± 0.7‰) emerges as the primary carbon source for bivalves (57% of their body composition), far surpassing contributions from particulate sources (26% from POC > 100 µm and 14% from POC < 100 µm). While ascidians still rely primarily on POM (60 to 71%), DOC plays an essential role as a supplementary food source (23 to 29%). These results challenge the prevailing assumption that POM is the exclusive food source for these organisms. Given the widespread presence of bivalves and ascidians in benthic habitats, our findings highlight their ability to bypass the microbial loop and directly utilize dissolved organic compounds, prompting a reevaluation of current benthic carbon budgets.
SN - 0027-8424
SN - 1091-6490
ER -