Quick Summary
- Warming waters plus ocean acidification are predisposing some marine life to dissolving
- Faced with warming, bryozoans build more magnesium into their skeletons, making them vulnerable to acidification
- Other marine animals who build skeletons in similar ways may also be vulnerable
The one-two punch of warming waters and ocean acidification is predisposing some marine animals to dissolving quickly under conditions already occurring off the Northern California coast, according to a study from the University of California, Davis.
In , researchers at the y raised bryozoans, also known as 鈥渕oss animals,鈥 in seawater tanks and exposed them to various levels of water temperature, food and increased acidity.
The scientists found that when grown in warmer waters and then exposed to acidity, the bryozoans quickly began to dissolve. Large portions of their skeletons disappeared in as little as two months.
鈥淲e thought there would be some thinning or reduced mass,鈥 said lead author Dan Swezey, a recent Ph.D. graduate in professor Eric Sanford鈥檚 lab at the 嘿嘿视频 Bodega Marine Laboratory. 鈥淏ut whole features just practically before our eyes.鈥
Skeletons key
Bryozoans are colonial animals, superficially similar to, but not related to, corals. Abundant in California kelp forests, they are calcareous, meaning they build their honeycomb-shaped skeletons from calcium carbonate.
The scientists found that when raised under warming conditions, bryozoans altered their chemical composition by building higher levels of magnesium into their skeletons, particularly if they were also eating less food. When exposed to more acidic conditions already observed off coastal California, these changes predisposed the animals to dissolve.
The researchers consider bryozoans a canary in the coal mine for other marine animals that build calcareous skeletons containing magnesium. These include sea stars, sea urchins, calcifying algae and tube-building worms.
The authors do not know why the bryozoans added more magnesium to their skeletons under warmer temperatures. But they conclude that marine organisms with skeletons made of high-magnesium calcite may be especially susceptible to ocean acidification because this form of calcium carbonate dissolves more easily than others.
Bryozoans grow in connected colonies. During the experiments, the animals shut down parts of themselves when undergoing the stress of ocean acidification, redirecting their energy to new growth. This was somewhat like closing down units of a condominium complex while building new ones at the same time. But the moss animals could not outpace the dissolution.
鈥淭hey were trying to grow but were dissolving at the same time,鈥 Swezey said.
Calcified animals increasingly vulnerable
The authors said the study underlines the increasing vulnerability of calcified animals to ocean acidification, which occurs as the ocean absorbs more atmospheric carbon emitted through the burning of fossil fuels.
During the spring and summer months, deep ocean water rich in carbon dioxide periodically wells up along the California coast when surface waters are pushed offshore by strong winds. These events also push nutrients to the surface to help support kelp forests and productive fisheries. However, this deep water tends to be more acidic.
Climate modeling shows that the trends of warming ocean temperatures, stronger winds and increasingly strong upwelling events are expected to continue in the coming years as carbon dioxide concentrations in the atmosphere increase. This indicates that acidified conditions will likely become more common, rather than episodic.
Marine life faces many changes
鈥淢arine life is increasingly faced with many changes at once,鈥 said co-author Sanford, a professor in the 嘿嘿视频 Department of Evolution and Ecology. 鈥淔or bryozoans, their response to warmer temperature makes them unexpectedly vulnerable to ocean acidification. The question now is whether other marine species might respond in a similar way.鈥
The study鈥檚 other co-authors include Jessica Bean, Aaron Ninokawa, Tessa Hill and Brian Gaylord from 嘿嘿视频. Bean is also affiliated with UC Berkeley.
The study was supported by grants from the National Science Foundation and the University of California Multicampus Research Programs and Initiatives. Swezey was also supported by a NSF Graduate Research Fellowship.
Read and other climate change on the 嘿嘿视频 website.
Media Resources
Daniel Swezey, 嘿嘿视频 Bodega Marine Laboratory, 831-345-6108, dsswezey@ucdavis.edu
Kat Kerlin, 嘿嘿视频 News and Media Relations, 530-750-9195, kekerlin@ucdavis.edu