What are some major threats to coral reefs?

The choice identifying climate change and overfishing as major threats to coral reefs is correct because both factors have a significant and detrimental impact on these ecosystems.

Climate change contributes to coral bleaching, a phenomenon where corals lose their vibrant colors due to stress from elevated water temperatures and other factors associated with climate change, including ocean acidification. When corals are stressed, they may expel the symbiotic algae living in their tissues, which provide them with essential nutrients; this can ultimately lead to coral death if prolonged and not reversed.

Overfishing further exacerbates the situation by disrupting the delicate balance of marine ecosystems. When key species are removed from the food web, such as herbivorous fish that graze on algae, the increased algae growth can smother corals and compete for space and resources, hindering coral recovery and health.

The other options presented do not address the core threats recognized by marine scientists. Increased biodiversity typically benefits coral reefs rather than threatens them, as a diverse ecosystem supports resilience against diseases and environmental changes. Medicinal usage of marine compounds usually involves sustainable practices, and while age longevity is important to individual species, it is not a direct threat to the survival of coral reefs as a whole. Limited water temperatures might also imply a