Fish that tend patches of stringy algae seem to shield branching corals from the worst effects of marine heat waves and help them recover after bleaching. In 2019, the reefs near the French Polynesian island of Moorea in the South Pacific Ocean endured their worst heat stress event in 14 years. Branching corals there bleached en masse. Some of those colonies were in "gardens" defended by farmerfish, which cultivate their own algae for food and chase off fish that eat plants and corals. The researchers discovered that, after one year, just 44 per cent of colonies inside gardens died compared with 67 per cent of those outside gardens. What’s more, colonies on the turf of the territorial fish were twice as likely to recover living tissue to the levels they had been before bleaching. Mark Hay, Regents Professor and Teasley Chair in the School of Biological Sciences, didn't work on the research but said that tissue recovery was "a big deal" and that the farmerfish seem to be having a positive effect. (Subscription required)