Wednesday, October 04, 2023

Growth of coral reefs likely cannot keep pace with rising sea level

International research team’s mapping of 9,000 years of coral growth using drill cores from Belize shows decreasing accretion rate over recent earth history

Peer-Reviewed Publication

GOETHE UNIVERSITY FRANKFURT

Underwater images of Belize coral reef — IMAGE:
THE UPPER PANEL SHOWS A CORAL REEF MARGIN IN BELIZE WITH LIVING BRANCHED ACROPORA (ELKHORN) AND PLATY MILLEPORA (FIRE) CORALS, WHICH ARE BOTH COMPETITIVE AND FAST-GROWING. THE LOWER PANEL SHOWS BROKEN BRANCHES OF DEAD ACROPORA CORALS OVERGROWN BY WEEDY, FERTILE HILL AND FINGER CORALS (PORITES) AS WELL AS FLESHY ALGAE.
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CREDIT: PHOTOS: E. GISCHLER

FRANKFURT. Tropical coral reefs could end up being one of the first victims of climate change. The marine diversity hotspots are threatened by and declining as a result of global warming, ocean acidification, a deterioration of water quality, as well as diseases of reef-building organisms, and their growth is unable to keep up with the projected rise in sea levels. These are some of the conclusions drawn by an interdisciplinary team of scientists from Goethe University Frankfurt’s Institute of Geosciences, the company ReefTech Inc., the GEOMAR Helmholtz Center of Ocean Research, the University of Ottawa’s Department of Earth and Environmental Sciences, and the GSI Helmholtz Center of Heavy Ion Research. Their findings are based on an examination of 22 drill cores collected from the Belize barrier reef and atolls, the largest reef system in the Atlantic Ocean, which focused on identifying and dating coral growth and accretion rates over the past 9,000 years.

Professor Eberhard Gischler, head of the biosedimentology working group at Goethe University Frankfurt’s Institute of Geosciences, and other scientists reexamined the specimens Gischler and Dr. J. Harold Hudson, Miami, USA, had collected between 1995 and 2002 . Studying the drill cores – which taken together measure a total of 215 meters – “enables us to develop both detailed and systematic reconstructions of the environmental conditions that prevailed during the Holocene, based on which previous ecological and environmental conditions can be reconstructed, allowing us to determine whether the current coral and coral reef declines are in fact unprecedented,” Gischler says. Pooling their expertise, they identified and dated 127 coral fragments using radioisotope methods, and statistically analyzed the changes in coral community structure over time based on more than 1,100 fossil corals. Radioisotope dating allows scientists to determine the age of a material by referring to the decay rates of radioactive samples present in the sample.

Having dated the corals, the team then identified the distances between them in the drill cores to estimate their growth rates. “Our data show that coral accretion rates in Belize decreased during the Holocene. While at 3.36 millimeters per year, the average accretion rates of reef margins are in the same range as other regions in the western Atlantic, they are somewhat lower than those in the Indo-Pacific.” This has both an important impact on the future of tropical island-nations especially, which are either based on or protected by coral reef structure, and is also interesting in the context of climate change, Gischler explains. “The growth rates are at the lower end of the United Nations' Intergovernmental Panel on Climate Change’s (IPCC) predictions of future sea-level rise until 2100.”

The research confirms the drastic decline in live coral in the Caribbean, where many reefs are no longer dominated by corals, but fleshy algae as well as weedy, generalistic taxa. Looking at the evolution over time, Gischler and his colleagues found that stress-tolerant, reef-building corals predominate in the older sections. “At the base of our cores, directly overlying Pleistocene reef limestone, Pseudodiploria brain corals and Orbicella star corals are most common, illustrating that members of the stress-tolerant taxa are clearly dominating,” Gischler explains. Once the reef pedestal was fully inundated and environmental conditions improved, however, the abundance of this type of coral decreased.

The study’s authors point out that the shift from stony corals to fleshy algae and from common reef-builders to weedy taxa underlines the increasing importance of fecundity for the coral community, a trait which it seems helps them cope with increasing environmental stress.

Pre-Anthropocene gaps in growth

Another interesting detail unearthed in the drill cores is the existence of three centennial-scale gaps in the fossil record of the fast-growing, competitive “elkhorn coral” Acropora palmata in Belize – about 2,000, 4,000, as well as 5,500-6,000 years before today. The first and last of the gaps coincide with the two Acropora gaps in the Virgin Islands and the wider Caribbean, the researchers say, and likely point to periods of higher temperatures and increased storm activity as well as lower nutrient supply as possible causes.

By contrast, the gap around 4,000 years before today coincides with a potential mass mortality of grazing echinoids in the region, which might have caused an increase in the abundance of fleshy algae during this time window. Another possible cause advanced by the study’s authors is that the mortality was connected to the so-called 4.2 k-event, thought to have resulted in mid-latitude drought in North America as well as elevated sea surface temperature in tropical oceans.

Publication: Eberhard Gischler, J. Harold Hudson, Anton Eisenhauer, Soran Parang & Michael Deveaux: 9000 years of change in coral community structure and accretion in Belize reefs, western Atlantic. Scientific Reports 13:11349 (2023), https://doi.org/10.1038/s41598-023-38118-5.

Eberhard Gischler (left; on winch), Harold Hudson (center; on tripod) and Belizean assistant Eric Vasquez coring using a hydraulic rotary drill on the pavement of the Belize Barrier Reef. .

CREDIT

Photo: G. Meyer

JOURNAL

Scientific Reports

DOI

10.1038/s41598-023-38118-5

ARTICLE TITLE

9000 years of change in coral community structure and accretion in Belize reefs, western Atlantic

“Hope is hard” - Shedd Aquarium’s recent research expedition reveals alarming extent of coral mortality in Florida

Business Announcement

SHEDD AQUARIUM

Shedd Research Team Survey Extend of Coral Mortality in Florida — IMAGE:
SHEDD SCIENTIST SURVEYS EXTEND OF CORAL MORTALITY IN FLORIDA REEFS THROUGH SCUBA DIVE OBSERVATION
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CREDIT: ©SHEDD AQUARIUM/GAVIN WRIGHT

Scientists from Chicago’s Shedd Aquarium, a leader in conservation research, returned from a multi-institutional research expedition to survey coral bleaching impacts from Miami and the Florida Keys to the Dry Tortugas, following an unprecedented rise in ocean temperatures. The week-long trip revealed that 90-95 percent of corals showed signs of extreme bleaching, and some coral species, such as endangered staghorn and elkhorn coral, were nearly all dead – a testament to how quickly water temperatures soared. Researchers at Shedd, who have long been studying coral heat tolerance, stress that Florida may be a bellwether for the future of coral reefs globally, if the climate continues to warm.

“With record high temperatures since July, we were expecting severe bleaching and prepared ourselves for the worst-case scenario, and that is unfortunately what we witnessed,” said Dr. Ross Cunning, research biologist at Shedd Aquarium. “For Shedd Aquarium, this trip begs two big questions: how do we prepare and safeguard other corals for future warming, and how can we accelerate efforts to enhance heat tolerance and give corals a chance for survival in hotter oceans?”

Aboard Shedd’s research vessel, the Coral Reef II, Shedd researchers hosted partners from the University of Miami, Palm Beach Zoo and the University of Southern California who collaborated to visit and survey 76 coral sites and report their findings to the Florida Fish and Wildlife Conservation Commission (FWC). The group witnessed the effects of the bleaching get worse the further they ventured south. What was once colorful, thriving coral a few months prior is now stark white, indicating severe bleaching or worse – covered in algae – an indicator that the living coral tissue is gone.

While the team had hoped to bring back hundreds of genetically unique staghorn corals from the Dry Tortugas to the University of Miami’s land-based facilities for gene banking and restoration, they found that the abundant populations they had seen and studied on a previous research expedition just two months earlier suffered almost complete mortality from the extreme heat stress. The few living fragments that remained were severely bleached, and researchers believe their chances of recovery are extremely low.

Even after searching extensively throughout the Dry Tortugas – down to depths of 60 feet where researchers hoped for a greater chance for survivors – not a single viable staghorn coral was found.

“In moments like this it can feel difficult to tell a story with hope,” said Dr. Shayle Matsuda, research biologist at Shedd Aquarium. “This drastic bleaching may spread globally in the next one to two years. Our research efforts to find and save corals with higher levels of heat tolerance is more critical now than it has ever been before.”

Ocean temperatures across the globe have been steadily increasing as a direct result of climate change. These high, sometimes record-setting temperatures are sustained for months – in this case leading to the fast and expansive coral mortality event. El Nino, a climate pattern that is characterized by unusually high ocean temperatures, exacerbated conditions in the Florida Keys, which registered temperatures well above their seasonal peak early in the summer.

For the past several years, Shedd Aquarium’s research team has been focused on learning more about the natural variance of heat tolerance in coral to determine how interventions harnessing genetics or microbial conditions can help corals withstand higher ocean temperatures. Unfortunately, large colonies of elkhorn and staghorn coral that were the focus of various research and restoration efforts were wiped out by this mass bleaching.

“Tragically, our mission turned from rescue to witness," said Cunning. “This is the worst bleaching event in history, and the impacts the high temperatures have had on Florida’s genetic coral diversity cannot be overstated.”

Despite this setback, Shedd Aquarium remains more committed than ever to working with partners in Florida and beyond to monitor native reefs and advocate for stronger coral safeguards and intervention strategies as ocean temperatures continue to rise.

What You Can Do

Commit to stopping climate change: Combating the effects of climate change is the most impactful effort we can make individually and as a society to ensure the longevity of our planet and the future of coral populations. Anyone interested in learning more about climate change and how to make an impact can join Surge, Shedd’s free, premier digital advocacy community that includes conservation-focused news and action alerts that provide tangible and timely ways to act and advocate for wildlife.
Help protect corals from local stressors like dredging: In 2019, Shedd published a paper with colleagues from Miami Waterkeeper and the University of Miami describing widespread coral mortality caused by dredging at the PortMiami that was done to make way for larger cargo ships. Years later, NOAA has released a report on the impacts of the dredging with some new analysis and data, affirming the findings in 2019 — that millions of corals were likely killed. With more potential dredging on the horizon, Shedd is asking the public to support Miami Waterkeeper in calling for the Army Corps of Engineers to fix the impacts from the last dredging, document lessons learned and direct any mitigation funding to scale up coral restoration at industrial levels.
Encourage Funding for Coral Futures: Making a donation to organizations like Shedd Aquarium can directly fuel ongoing coral research and intervention efforts.

VISUALS: High-res photos and video from Shedd Aquarium’s recent coral monitoring trip to the Florida Keys and Dry Tortugas can be viewed and downloaded here: https://personal.filesanywhere.com/fs/v.aspx?v=8e6e678d596176bba968.

Photo credit: ©Shedd Aquarium/Gavin Wright
Coral side-by-side credit: ©Shedd Aquarium/Ross Cunning
Video credit: ©Shedd Aquarium/Sam Cejtin

# # #

About Shedd Aquarium 

The John G. Shedd Aquarium in Chicago sparks compassion, curiosity and conservation for the aquatic animal world. Home to 32,000 aquatic animals representing 1,500 species of fishes, reptiles, amphibians, invertebrates, birds and mammals from waters around the globe, Shedd is a recognized leader in animal care, conservation education and research. An accredited member of the Association of Zoos & Aquariums (AZA), the organization is an affiliate of the Smithsonian Institution and supported by the people of Chicago, the State of Illinois and the Chicago Park District. www.sheddaquarium.org  

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

Animals

Understanding greenhouse gases in oil palm plantations

Research team led by Göttingen University investigates nitrous oxide emissions in Jambi

Peer-Reviewed Publication

UNIVERSITY OF GÖTTINGEN

Drone view of oil palm plantation with tower to measure N2O emissions — IMAGE:
DRONE VIEW OF OIL PALM PLANTATION WITH TOWER TO MEASURE N2O EMISSIONS
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CREDIT: ANNAGGADIPA R. JAMBI

The rapid spread of oil palm plantations and associated high use of fertilizer raises concerns about the emission of nitrous oxide (N2O), a powerful greenhouse gas. A new study by an international research team led by the University of Göttingen shows that oil palms’ photosynthesis and their response to meteorological and soil conditions play an important but still widely unexplored role in the amount of N2O produced by oil palm plantations. The results are important for strategies to reduce the negative impact of N2O emissions from oil palm cultivation by selecting appropriate locations and improving plantation management. The study was published in the journal Global Change Biology – Bioenergy.

During recent decades, rising global demand for cheap oils and fats has promoted the expansion of oil palm plantations in tropical regions. High yields of palm oil are typically achieved by a high use of fertilizer. However, high fertilizer levels or inappropriate timing of fertilizer application may cause environmental problems such as increased emissions of N2O. The scientists carried out their research in a mature plantation in Jambi, Indonesia, with the aim of quantifying N2O emissions in oil palm and assessing environmental and meteorological drivers of N2O emissions over different timescales.

“The timing and location of N2O emissions in oil palm plantations vary hugely, which means it is really difficult to estimate emissions. This has really hampered our understanding of cause-and-effect relationships,” says first author Dr Christian Stiegler from the Bioclimatology Group, University of Göttingen. “However, we found that variations in N2O emissions are strongly linked to oil palm metabolism and the oil palms’ response to meteorological and soil conditions. Over the course of the day, for instance, emissions were mainly related to oil palm photosynthesis. During the night, we could link the level of emissions to oil palm respiration and soil temperature. Over longer periods of time, meaning several days to several weeks, we found that changes in weather patterns, soil moisture and soil temperature directly impact oil palm photosynthesis, respiration and N2O production in the soil and therefore N2O emissions,” explains Stiegler. This multitude of drivers interacting over various time periods imposes high demands on how the effects could be measured. The study also shows that conventional measurement approaches that do not take into account how N2O is transported within individual oil palms risk underestimating N2O emissions from oil palm cultivation by 49%.

“The oil palm plantation that we studied is a strong local source of N2O, with up to 77% higher emissions compared to natural forest systems in Jambi province,” explains Professor Alexander Knohl, senior author and head of the Bioclimatology Group, University of Göttingen. “This research highlights how important it is to quantify N2O emissions in oil palm and to understand their dynamics and the controlling factors. This will allow farmers to develop optimal fertilizer management systems adapted to the age of the palms, nitrogen requirements of each plant, and local soil and climate condition for mitigating the negative impacts of oil palm cultivation by reducing N2O emissions.”

This research is part of the German-Indonesian Collaborative Research Centre “Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems (EFForTS)”, funded by the German Research Foundation (DFG). Further information can be found here: www.uni-goettingen.de/efforts.

Original publication: Christian Stiegler et al. Temporal variation in nitrous oxide (N2O) fluxes from an oil palm plantation in Indonesia: an ecosystem-scale analysis. Global Change Biology – Bioenergy. DOI: 10.1111/gcbb.13088

https://www.uni-goettingen.de/en/544871.html

Ecosystem-scale measurement system and view from the tower over oil palm plantation in Jambi, Indonesia.