Warming ocean temperatures and acidification drastically reduce the skeletal strength and filter-feeding capacity of glass sponges, according to new UBC research.
Researchers harvested Aphrocallistes vastus, one of three types of reef-building glass sponges, from Howe Sound and brought them to UBC for study.
The findings, published in Scientific Reports, indicate that ongoing climate change could have serious, irreversible impacts on the sprawling glass sponge reefs of the Pacific Northwest – the only known reefs of their kind in the world.
Ranging from the Alaska-Canada border and down through the Strait of Georgia, the reefs play an essential role in water quality by filtering microbes and cycling nutrients through food chains. They also provide critical habitat for many fish and invertebrates, including rockfish, spot prawns, herring, halibut and sharks.
“Glass sponge reefs are ‘living dinosaurs’ thought to have been extinct for 40 million years before they were re-discovered in B.C. in 1986,” said Angela Stevenson, who led the study as a postdoctoral fellow at UBC Zoology.
“Their sheer size and tremendous filtration capacity put them at the heart of a lush and productive underwater system, so we wanted to examine how climate change might impact their survival.”
She ran the first successful long-term lab experiment involving live sponges by simulating their natural environment as closely as possible with Howe Sound glass sponges. She then tested their resilience by placing them in warmer and more acidic waters that mimicked future projected ocean conditions.
Within one month, ocean acidification and warming, alone and in combination, reduced the sponges’ pumping capacity by more than 50 per cent and caused tissue losses of 10 to 25 per cent, which could starve the sponges.
“Most worryingly, pumping began to slow within two weeks of exposure to elevated temperatures,” said Stevenson.
The combination of acidification and warming also made their bodies weaker and more elastic by half. That could curtail reef formation and cause brittle reefs to collapse under the weight of growing sponges or animals walking and swimming among them.
Year-long temperature data collected from Howe Sound reefs in 2016 suggest it’s only a matter of time before sponges are exposed to conditions which exceed these thresholds.
“In Howe Sound, we want to figure out a way to track changes in sponge growth, size and area and area in the field so we can better understand potential climate implications at a larger scale,” said co-author Jeff Marliave, senior research scientist at the Ocean Wise Research Institute
