Climate impacts on ocean and coastal ecosystems will be exacerbated by increases in intensity, reoccurrence and duration of marine heatwaves , in some cases, leading to species extirpation, habitat collapse or surpassing ecological tipping points . Some habitat- forming coastal ecosystems including many coral reefs, kelp forests and seagrass meadows, will undergo irreversible phase shifts due to marine heatwaves with global warming levels >1.5℃ and are at high risk this century even in <1.5℃ scenarios that include periods of temperature overshoot beyond 1.5°℃ . Under SSP1-2.6, coral reefs are at risk of widespread decline, loss of structural integrity and transitioning to net erosion by mid-century due to increasing intensity and frequency of marine heatwaves . Due to these impacts, the rate of sea level rise is very likely to exceed that of reef growth by 2050, absent adaptation. Other coastal ecosystems, including kelp forests, mangroves and seagrasses, are vulnerable to phase shifts towards alternate states as marine heatwaves intensify . Loss of kelp forests are expected to be greatest at the low-latitude warm edge of species' ranges . 
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report