Contributed Session.
Lead Organizer: Katie Barott, University of Pennsylvania (kbarott@sas.upenn.edu)
Co-organizers:
Kelly LuiS, NASA Water Resources (kelly.m.luis@jpl.nasa.gov)
Presentations
06:00 PM
ANALYSIS OF LONG-TERM SPATIO-TEMPORAL REEF BENTHOS COVER IN THE EGYPTIAN RED SEA (9054)
Primary Presenter: Sara Ahmed, Leibniz Centre for Tropical Marine Research (ZMT) (sara.galal@leibniz-zmt.de)
The Egyptian Red Sea is home to distinctive and varied coral reefs, totaling to about 1.3% of all coral cover on Earth. The 1,800 km Egyptian coast occupies most of the Red Sea's northwestern shore, where corals show exceptional thermal resistance. Hence, the northern Red Sea may provide a refuge for coral reefs. Corals in this area are expected to be among the last to decline and may serve as candidates for worldwide reef restoration. Nevertheless, despite their high value and potential resilience, Red Sea reefs are still subject to anthropogenic stressors and extensive damage due to coastal industrial development, fishing, and tourism activities. Moreover, growing climate and anthropogenic stressors can cause non-random community changes, which may occur gradually or abruptly when an ecological tipping point is exceeded. This study aims to investigate whether there are long-term significant temporal or spatial pattern changes in reef benthos assemblages in the Egyptian Red Sea reefs. To address this, we use long-term research and monitoring data collected from different sources, including published peer-reviewed articles, grey literature, and monitoring reports. We focus on changes in the composition of the coral reef benthos, mainly addressing hard coral, soft coral, and macroalgae cover changes, encompassing a period of 36 years.
06:00 PM
Context-Dependent Top-Down and Bottom-Up Regulation of Algal Growth: A Global Meta-Analysis and Experimental Evidence from a Nutrient-Enriched Coral Reef (9160)
Primary Presenter: Alexandra McCallum, McGill University (alexandra.mccallum@mail.mcgill.ca)
Coral reefs face increasing risks of phase shifts from coral to algal dominance due to anthropogenic pressures such as nutrient enrichment, overfishing, and climate change. Algal dominance can be promoted by top-down (overfishing of herbivores) and bottom-up (nutrient enrichment) factors. However, variation in their relative importance is still poorly understood. We tested the dependence of top-down control of algal growth on algal groups and herbivore size. We first conducted a controlled field experiment in a marine protected area along a coastal area of Barbados exposed to high nutrient enrichment. Exclusion cages of varying mesh sizes were used to assess the role of herbivore size in controlling macroalgae. Algal biomass was significantly higher in both large and small mesh cages compared to open and partial controls, highlighting the critical role of large herbivores in algal suppression. A global meta-analysis of 93 field experiments further revealed that both nutrient enrichment (bottom-up control) and herbivore exclusion (top-down control) significantly increase primary producer abundance, with the strongest effects observed when both factors co-occurred. While cyanobacteria showed synergistic responses to these combined pressures, macrophytes and crustose coralline algae exhibited antagonistic effects. These findings suggest herbivory can regulate both the net growth and community structure of primary producers and mitigate the impacts of nutrient enrichment on coral reef ecosystems.
06:00 PM
THE ROLE OF HETEROTROPHY IN OCULINA ARBUSCULA’S RESPONSE TO OCEAN ACIDIFICATION (9331)
Primary Presenter: Alejandra Daniel, Department of Biology (ad07436@georgiasouthern.edu)
Anthropogenic carbon dioxide emissions have been increasing since the Industrial Revolution. Once CO2 enters the ocean, chemical reactions occur that result in increased hydrogen ion concentration (and therefore decreased seawater pH) and decreased carbonate ion concentration; this process is known as ocean acidification (OA). Ocean acidification has been well documented to cause dissolution of calcium carbonate, reduced calcification rates, and coral bleaching. In healthy corals, symbiotic algae autotrophically fix carbon in excess, transferring most of it to the coral host which supplies it with up to 100% of its daily needs. Corals also obtain carbon heterotrophically, which contributes up to 60% of fixed carbon. Exposure to OA conditions may induce stress, causing symbiotic algae to be expelled from the coral host and resulting in a loss of autotrophically acquired carbon. Carbon acquisition patterns may change, and heterotrophically acquired carbon can become a more significant source of energy. Oculina arbuscula is a facultatively symbiotic coral that has shown similar resistance to OA in both symbiotic and aposymbiotic corals. To determine the role heterotrophy has in allowing O. arbuscula to ameliorate the effects of OA, a 90-day lab experiment will be conducted exposing O. arbuscula to low pH conditions and varying levels of feeding. Results of this study will contribute to knowledge of what mechanisms aid in coral resistance to OA, and how ocean acidification will affect to calcium carbonate-based organisms.
06:00 PM
Characterization of Fatty Acids in Symbiotics and Aposymbiotic Astrangia poculata: Insigth into Energy Acquisitions and Environmental Adaptations (9437)
Primary Presenter: Héctor G. Torres-De Jesús, University of Puerto Rico (htorresdejesus@gmail.com)
Fatty acids (FAs), a major component of lipids, play a crucial role in energy storage, cellular signaling, and the structure of cell membranes. These biomolecules provide valuable insights into resource acquisition, modification, and allocation in organisms. The Northern Star Coral, Astrangia poculata, serves as a model system for examining the role of fatty acids in metabolism due to its facultative symbiosis, allowing it to exist in both symbiotic and aposymbiotic states. Studying the fatty acid composition in A. poculata tissues offers insight into their dietary intake and how they acquire energy to support their metabolic functions in these different states. For this research, samples of both symbiotic and aposymbiotic A. poculata were collected from Fort Wetherill, Jamestown, RI. The coral tissue was processed to extract and transesterify the fatty acids, followed by analysis using Gas Chromatography Flame Ionization Detection (GC-FID) to separate the FAs by size, identify key types, and determine their concentration. Results revealed that the symbiont ecotype of A. poculata shares FAs between the host and the symbiont. Understanding the role of fatty acids in these corals is crucial to recognizing how they can achieve beneficial adaptations in challenging environments, with implications for the conservation of entire ecosystems impacted by environmental and anthropogenic stressors.
06:00 PM
DEEP-SEA CORAL COMMUNITIES AS DRIVERS OF HABITAT COMPLEXITY (9353)
Primary Presenter: Ignacio Rueda, University of Puerto Rico Mayaguez (ignacio.rueda@upr.edu)
The physical structure of habitats shapes biodiversity, ecosystem function, and resilience. Deep-sea corals are habitat-forming organisms that contribute significantly to seafloor structural complexity and associated ecosystem functions. However, quantifying coral-driven habitat complexity in the deep sea is challenging due to the difficulty of surveying these environments and the complex morphologies of deep-sea corals. In this study, we assessed structural complexity at the Keahole Point Precious Coral Bed and the Japanese submarine I-201 in the waters of Hawai’i aboard the E/V Nautilus cruise NA156 using seafloor imagery provided by the ROV Hercules to directly quantify the structural complexity provided by deep-sea corals. We generated high-resolution 3D models and then digitally removed the corals to compare habitat structural complexity (defined as the ratio of 3D to 2D area) for paired models with and without the corals to quantify their contribution to structural complexity. Our preliminary results suggest that even relatively low coral cover deep-sea communities can detectably increase seafloor structural complexity. Further analyses will assess how different coral taxa contribute to structural complexity at both sites and examine the scale-dependence of this complexity to better understand their role in habitat provisioning across spatial scales. These findings highlight the role of deep-sea corals as ecosystem engineers, enhancing habitat structural complexity and contributing to the resilience of both natural and artificial ecosystems.
CS06P - Coral Reef Ecosystems
Description
Time: 6:00 PM
Date: 29/3/2025
Room: Exhibit Hall A