The Ocean’s Fragile Fortresses: Uncovering the Impact of Climate Change on Bryozoans

Bryozoans, small colonial invertebrates, play a vital role in forming marine habitats. However, their response to environmental changes has long been overlooked. A recent study published in Communications Biology sheds light on how ocean acidification and warming can affect bryozoan colonies, with crucial implications for marine conservation.

The researchers from the Institut de Ciències del Mar (ICM-CSIC) used a natural laboratory on the island of Ischia, Italy, to simulate the conditions projected for the end of the century. They analyzed the morphology, skeleton mineralogy, and microbiome of two bryozoan species exposed to these conditions. The findings revealed that the species exhibit some acclimation capacity, modifying their skeletal mineralogy to become more resistant.

However, a loss in functional microbial diversity was observed, with a decline in genera potentially involved in key processes such as nutrition, defense, or resistance to environmental stress. This suggests that even if colonies look externally healthy, changes in the microbiome could serve as early bioindicators of environmental stress.

The study also considered the effects of rising temperatures, another key factor in climate change. The models used indicate that the combination of these two stressors intensifies the effects observed, significantly reducing the coverage of the encrusting bryozoan and increasing mortality.

These findings have important implications for marine conservation. Habitat-forming species like bryozoans are not only vulnerable but their disappearance could trigger cascading effects on many other species that rely on them for shelter or food. The characterization of the microbiome and preliminary identification of potentially beneficial microorganisms open new research avenues to enhance the resilience of holobionts (host and its associated microbiome) through nature-based approaches.

The complexity of this issue demands integrated analyses, highlighting the importance of interdisciplinary approaches in anticipating future scenarios and protecting marine ecosystems.

The Great Barrier Reef, one of the world’s most iconic natural wonders, has been facing unprecedented threats due to climate change. Rising sea levels, more frequent heatwaves, and extensive bleaching have pushed the reef to the brink of collapse. However, a new study led by Professor Jody Webster from the University of Sydney suggests that the reef may be more resilient than previously thought.

The research, published in Nature Communications, draws on a geological time capsule of fossil reef cores extracted from the seabed under the Great Barrier Reef. The findings indicate that rapid sea level rise alone did not spell the end of the reef’s predecessor, Reef 4. Instead, it was the combination of environmental stressors such as poor water quality and warming climates that led to its demise about 10,000 years ago.

The study reveals that Reef 4, also known as the proto-Great Barrier Reef, had a similar morphology and mix of coral reef communities to the modern Great Barrier Reef. The types of algae and corals, and their growth rates, are comparable. Understanding the environmental changes that influenced it and led to its ultimate demise offers clues on what might happen to the modern reef.

Professor Webster and his colleagues used radiometric dating and reef habitat information to accurately pinpoint core samples pertaining to Meltwater pulse 1B, a period when global sea levels rose very rapidly. The cores underpinning this research were obtained under the International Ocean Discovery Program (IODP), an international marine research collaboration involving 21 nations.

The findings lend weight to already grave concerns about the Great Barrier Reef’s future. If the current trajectory continues, we should be concerned about whether the reef will survive the next 50 to 100 years in its current state. However, the study suggests that a healthy, active barrier reef can grow well in response to quite fast sea level rises.

The importance of learning from the past and understanding how reef and coastal ecosystems have responded to rapid environmental changes cannot be overstated. These data allow us to more precisely understand how reef and coastal ecosystems have responded to rapid environmental changes, like the rises in sea level and temperature we face today.

As we move forward with climate change mitigation efforts, it is crucial that we take a holistic approach, considering not only the direct impacts of rising sea levels but also the associated environmental stressors. By doing so, we may be able to prevent or slow down the decline of the Great Barrier Reef and ensure its continued resilience for generations to come.

A groundbreaking study published in the journal Coral Reefs has revealed that heat-tolerant symbiotic algae may hold the key to saving Florida’s elkhorn coral (Acropora palmata), a foundational species in Caribbean reef ecosystems, from the devastating impacts of marine heatwaves and coral bleaching.

The research, conducted by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, in collaboration with other institutions, provides timely insights into the thermal tolerance of elkhorn coral. The study tested 172 elkhorn coral colonies sourced from restoration nurseries stretching from Miami to the lower Florida Keys, using custom-built rapid heat stress testing systems onboard a research vessel.

The findings showed that elkhorn corals hosting the heat-tolerant symbiont Durusdinium could survive short-term exposure to temperatures almost 2°C higher than those with the more common Symbiodinium. These resilient colonies were sexually derived juvenile corals that had acquired Durusdinium in a land-based facility, providing evidence that manipulating symbiont communities in early life stages can be an effective strategy for producing heat-tolerant corals for restoration.

“This study represents the most extensive thermal tolerance dataset gathered on A. palmata,” said Richard Karp, lead author of the study. “By incorporating novel interventions like heat-tolerant symbionts into restoration efforts, we can boost coral resilience and help restore this iconic species.”

The findings come at a critical time, as a global coral bleaching event has already impacted 84 percent of the world’s reefs. The study emphasizes the importance of scaling up symbiont-based interventions as part of current and future coral conservation and restoration work.

“This is an example of Florida’s reef scientists sharing their scientific and restoration expertise to make critical discoveries,” said Andrew Baker, a professor at the Rosenstiel School. “We need to continue to innovate and think outside the box to help coral reefs in their fight for survival against continued warming and coral bleaching.”