Future climate scenarios threaten British Columbia's glass sponge reefs

Many tropical sponges thrive under predicted scenarios of ocean warming and acidification, but there are also examples of sponge decline. In British Columbia (Canada), glass sponges (primarily made of silica), such as... [ view full abstract ]

Many tropical sponges thrive under predicted scenarios of ocean warming and acidification, but there are also examples of sponge decline. In British Columbia (Canada), glass sponges (primarily made of silica), such as Aphrocallistes vastus form large intricate reefs unique and important to this region. These reefs are a highly productive water filtration system thought to impact major local and regional biogeochemical cycles and food webs. While protecting A. vastus from physical damage is a vital component of a successful conservation strategy, its sensitivity and resilience to climate change has not yet been explored. 

 We tested the effects of elevated seawater temperature and pCO₂ on the pumping capacity of A. vastus held in mesocosms and subjected to one of four treatments: ambient, elevated temperature, elevated pCO₂, and combined (elevated temperature and pCO₂) for four months. Pumping start time and strength were measured at three week intervals, and presence of necrosis was noted throughout the experiment. Both elevated temperature and pCO₂ reduced sponge pumping capacity by 2-4x compared to control sponges. Necrotic tissue onset occurred earlier (within one month) in sponges exposed to elevated temperature (including the combined treatment) and 50-60% of sponges in these treatments ceased pumping after one month of exposure to elevated temperature (versus none in the control). 

Overall, our findings suggest that temperature stress events and ocean acidification may negatively impact A. vastus filtration capacity and contribute to this species’ mortality indicating that ongoing climate change is a serious threat to BC’s glass sponge reefs.