As we have seen in previous posts, corals have a mutually beneficial relationship with symbiotic algae, zooxanthallae. It is hard to quantify just how much bacteria is found on corals. This algae is not the only thing that can be found around reefs. They play host to a wide variety of fish, crabs, sharks and all manner of other sea creatures. Like rainforests on land, coral reefs are hotspots for biodiversity. The Pacific Ocean is home to a vast array of plant and animal species, encompassing areas such as Australia, Indonesia, The Pacific Islands etc. these contain a large proportion of the worlds coral reefs. The Great Barrier Reef has 600 species of coral, 1500 species of fish and 6 species of turtle alone. The marine life flocks to the corals.
As we know, these corals are under threat, and so as a result of this these animals and plants are under threat. If corals were to be eradicated from the face of the earth, then it would be likely that the marine life dependant on them will follow suit. It is not just the decline of coral that affects these species. Overfishing has been increasing rapidly, coupled with the disease and bleaching of corals has left many ecosystems in a sorry state.
A study by JM Pandolfi et al. showed just what has been happening to the diversity at coral reefs from prehuman times to the present day. An alarming number of large herbivores have become extinct in this time period, with almost 30% of the large herbivores perishing. This contrasts to small herbivores who experienced no extinction over the same period, however there was still a high proportion of coral reefs that had depleted amounts of both small and large herbivores. It is a different story with regard to the carnivores found at coral reefs. Only 10% of large carnivores became extinct, 20% less than herbivores. Looking to plants, seagrass has become depleted at 50% of studied sites. These are worrying statistics. This has been taken across the entire world so gives a fairly accurate portrayal of what is currently going on in the worlds coral reefs. Here is a link to the study:
This reduction in biodiversity will then add to the issues faced by corals. The lack of fish and other marine animals will result in algal blooms. This will reduce the amount of sunlight reaching the corals. The corals will struggle to feed, resulting in more bleaching. Bleached corals will attract less animals. There is a multiplier effect occurring. This is a dangerous cycle that needs to be broken.
Things may be different on a local scale but on the whole things aren't looking good. The decrease in biodiversity is set to increase, with coral bleaching set to rise, along with unsustainable fishing, the oceans may be a lonely place to be in the future.
No comments:
Post a Comment