Organismal Metabolism and Their Drivers in Coral Reefs

The two most important and fundamental processes describing coral reef ecosystem functioning are photosynthesis (primary production) and calcification (reef growth). They determine energy flow, carbon cycling and habitat provision (calcium carbonate structures) in reefs. The MABEE lab addresses research questions that relate to the temporal and spatial dynamics of reef organism and reef community metabolism under in-situ or near-natural conditions. The strong seasonal environmental fluctuations in Bermuda and the long-standing ocean time series BATS provide an ideal framework to study the capacity for metabolic adjustments in corals and other reef organisms. This knowledge forms an important basis for further studies that aim to understand how reefs and their functional processes may change under progressing global change.

Current Projects

1. Eddy Reef (NSF-funded, since 2021): The main goal of the project is to understand the impact of mesoscale eddies on coral performance, in particular on coral calcification. Mesoscale eddies are large-circulating current patterns in the ocean. In the Sargasso Sea, meso-scale eddies spin off the Gulf Stream and can create substantial vertical water mixing. Their effect on coral reefs is so far largely unexplored. This project (1) assesses the physical and biogeochemical changes of reef waters that occur during eddies, (2) determines how these biogeochemical changes affect coral performance and (3) systematically explore long-term eddy impacts on corals (several decades) through the examination of oceanic time-series data and coral skeleton proxy records. This project is conducted in collaboration with Damian Grundle (BIOS/ ASU) and Nathalie Goodkin (AMNH).

Read more about the project here .

Student interns involved:

• Emily Fricska – undergraduate, of Victoria, Canada, 2023
• Natalie Graham – undergraduate [REU], Univ. of Louisiana at Lafayette, USA, 2022
• Justin Gross - graduate, Univ. of Victoria, Canada, 2022
• Cara DeLacluyse - undergraduate, Eckerd College, FL, USA, 2022

1. Reef metabolism time series: In 2021, we started a reef metabolism time series providing insight into short-term vs long-term variability in reef metabolism and its drivers. This time series is embedded in BIOS educational programs (summer CRE courses & REU program) and is conducted in collaboration with Matthew Long and Jeffrey Coogan at Woods Hole Oceanographic Institute (WHOI), who significantly advanced the utility of the applied Gradient-Flux approach.

Student interns involved:

• Isabel Martinez Farrington – undergraduate [REU], Univ. of Puerto Rico, 2022
• Kelly Koehler – undergraduate [REU], North Carolina State Univ, USA, 2021

1. Organism metabolism, coral heterotrophy and nutrient fluxes: All living organisms and their environment are in constant exchange of components, including O2, CO2, nutrients, and a range of inorganic and organic carbon compounds. To measure these processes, we recently constructed an innovative fully automated in-situ incubation chamber setup (BIO-RESORT; value ~$100k), together with engineers at GEOMAR Helmholtz Center for Ocean Research, Kiel, Germany. The BIO-RESORT allows continuous measurements of metabolic rates in 6 units simultaneously for up to one week at a time. Next to photosynthesis and respiration rate measurements (with O2 sensors), custom-built automated water samplers connected to each incubation chamber allow determining rates of, for example, calcification and nutrient uptake / release. The BIO-RESORT plays a significant role in the currently ongoing Eddy Reef and ENCORE projects.

Further research efforts are currently directed towards improving our understanding of coral energy gain via autotrophy and heterotrophy mostly as part of student intern projects. Those include (1) refined measurements of gross photosynthesis (GP) and daytime respiration of corals on a diurnal and seasonal scale and (2) the exploration of new approaches to improve coral heterotrophy quantification (in collaboration with Leocadio Blanco-Bercial, BIOS). (In-situ) coral heterotrophy and its contribution to the coral’s energy budget and nutrition is a so far poorly explored, although its significance may increase under climate change driven environmental stress.

Student interns involved:

• Sem Docekal – bachelor thesis, Van Hall Larenstein Univ., Netherlands, 2022
• Emie Woodburn - graduate, Univ. of Victoria, Canada, 2021
• Benjamin Shirey – graduate, Eckerd College, USA, 2021
• Chloe Root - undergraduate, Eckerd College, USA, 2021
• Hanne Borstlap - undergraduate, Princeton University, USA, 2021
• Roderick Bakker - bachelor thesis, Univ. of Leiden, Netherlands, 2021
• Natalia Padillo-Anthemides - undergraduate, Florida International Univ., USA, 2020
• Nicole Adams - undergraduate, Univ. of California – San Diego, USA, 2020
• Kathryn McLaughlin - undergraduate, Princeton Univ., USA, 2020
• Alexis Savard-Drouin - undergraduate, Dalhousie Univ., Canada, 2020
• Charlie Schneider - undergraduate, Colorado College, USA, 2019
• Anna Nicosia - undergraduate, Lehigh Univ., USA, 2019

Past Projects

1. Coral Reef Airborne Laboratory (CORAL) & light-use-efficiencies (NASA-funded, 2016 – 2019)

The mission of CORAL has been to investigate coral reef conditions, namely benthic community structure, primary production and calcification via remote sensing, which would ultimately allow reef monitoring on a global scale. Here, Sawall assessed community-scale light use efficiencies (LUEs) of different reef photosynthesizers using outdoor fumes. These LUEs are defined as the daily gross photosynthetic rates (or calcification rate) per daily absorbed light, and are required to derive primary production of reefs from airborne hyperspectral imagery (Sawall et al. 2018, more publications are currently in preparation). The ultimate goal of this work is to be able to model LUE based on community type and environmental condition, similar to what is already done for remote sensing of productivity in terrestrial ecosystems (e.g., satellite-based MODIS-GP).

Student interns involved: Allison Doolittle, David Flesher, Ashley Miller (maser thesis), Kelly Chimpen Mac Leod, Zoe Pearson (maser thesis)