Photo: CC BY-SA Sponge bleaching, tissue loss and decay Typical sponge reefs from Northland, New Zealand. Sponges also add three-dimensional complexity to the sea floor, which provides habitat for a range of other species such as crabs, shrimps and starfish. These invertebrates in turn are consumed by organisms further up the food chain, including commercially and culturally important fish species. They filter large quantities of water, capturing small food particles and moving carbon from the water column to the seafloor where it can be eaten by bottom-dwelling invertebrates. They serve a number of important ecological functions. In New Zealand, they occupy up to 70% of the available seafloor, particularly in so-called mesophotic ecosystems at depths of 30-150m. Sponges are among the most ancient and abundant animals on rocky reefs across the world. The loss of sponges may have major repercussions for the whole ecosystem. Our latest research shows the most severe impacts on sponges occurred in areas where the marine heatwave was most intense. In contrast, we didn’t observe any bleaching or tissue loss in central areas of New Zealand’s coastline, despite extensive surveys. Subsequently, we reported tissue loss, decay and death of other sponge species across the northern coastline of New Zealand, with an estimated impact on hundreds of thousands of specimens.
A bleached (left) and healthy (right) cup sponge Cymbastella lamellata. While only one species, the cup sponge Cymbastella lamellata, was affected, a prolonged marine heatwave turned millions of the normally dark brown sponges bright white. But earlier this year, New Zealand recorded the largest-ever sponge bleaching event off its southern coastline. Marine sponges were thought to be more resilient to ocean warming than other organisms.
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