Determining the Ecological Importance of Heterotrophic Nutrition in Reef-building Corals: Novel Insights from ∂13C Analysis of Essential Amino Acids
Abstract
Coral reefs are often considered nutritionally self-sustaining ecosystems adapted to oligotrophic environments. However, coral reefs thrive across a wide range of oceanographic conditions. Emerging evidence suggests these systems, including the mixotrophic corals that build them, are more tightly linked with oceanic primary production than previously considered. On more productive reefs, corals have greater access to heterotrophic nutrition, which provides a multitude of physiological benefits and can directly enhance recovery from thermal stress. Yet the analytical challenges of disentangling the relative contributions of autotrophic vs. heterotrophic nutrition have hindered our ability to examine the importance of heterotrophy to coral growth and survival across space and time. Here, we provide a new framework for quantifying coral nutrition using carbon isotope (∂13C) analysis of individual essential amino acids (AAESS). Our results reveal that patterns in ∂13C values among AAESS from the autotrophic (coral endosymbionts) and heterotrophic (phytoplankton and zooplankton) sources are distinct from one another and are consistent across multiple years and several central Pacific Islands spanning ~1500 km. The robust separation of these sources provides a much-needed technique for determining heterotrophic contributions to coral diets among individuals and across species. On Palmyra Atoll in the Northern Line Islands, we found that conspecific corals situated only a few meters apart can have different trophic ecologies with some colonies relying predominantly on autotrophic or heterotrophic nutrition. We anticipate this emerging technique will be widely applied to future studies exploring links between oceanic primary production and coral reef ecosystem functioning. Consequently, we also explore the influence of derivatization protocols and sample preparation to establish recommended best practices and maximize the comparability of data for synthetic analyses. The new insights to coral nutrition afforded by this framework are essential for investigating connections between oceanography, resource availability, and coral survival in a changing ocean.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP31B..05F
- Keywords:
-
- 1635 Oceans;
- GLOBAL CHANGE;
- 4825 Geochemistry;
- OCEANOGRAPHY: CHEMICAL;
- 4220 Coral reef systems;
- OCEANOGRAPHY: GENERAL;
- 4916 Corals;
- PALEOCEANOGRAPHY