Editing Coral reef (section)

===Invasive algae===
Hawaiian coral reefs smothered by the spread of invasive algae were managed with a two-prong approach: divers manually removed invasive algae, with the support of super-sucker barges. Grazing pressure on invasive algae needed to be increased to prevent the regrowth of the algae. Researchers found that native collector urchins were reasonable candidate grazers for algae biocontrol, to extirpate the remaining invasive algae from the reef.<ref name="Westbrook-2015" />

====Invasive algae in Caribbean reefs====
[[File:Invasive_Algae_Removal.JPG|thumb|Students from Nā Pua No‘eau remove invasive algae from Kāne‘ohe Bay. Programs could be created to remove algae from Caribbean reefs]]
Macroalgae, or better known as seaweed, has to potential to cause reef collapse because they can outcompete many coral species. Macroalgae can overgrow on corals, shade, block recruitment, release biochemicals that can hinder spawning, and potentially form bacteria harmful to corals.<ref>{{Cite journal|last1=Vieira|first1=Christophe|last2=Payri|first2=Claude|last3=Clerck|first3=Olivier|date=2016-09-08|title=A fresh look at macroalgal-coral interactions: are macroalgae a threat to corals? |journal=Perspectives in Phycology|volume=3|issue=3|pages=129–140|doi=10.1127/pip/2016/0068 |url=https://www.researchgate.net/publication/308886983}}</ref><ref name="Knowlton-2001">{{Cite journal |last=Knowlton|first=N.|date=2001-04-24|title=Sea urchin recovery from mass mortality: New hope for Caribbean coral reefs? |journal=Proceedings of the National Academy of Sciences|volume=98|issue=9 |pages=4822–4824 |doi=10.1073/pnas.091107198|pmid=11320228|pmc=33118|bibcode=2001PNAS...98.4822K |issn=0027-8424|doi-access=free}}</ref> Historically, algae growth was controlled by herbivorous fish and sea urchins. Parrotfish are a prime example of reef caretakers. Consequently, these two species can be considered as keystone species for reef environments because of their role in protecting reefs.

Before the 1980s, Jamaica's reefs were thriving and well cared for, however, this all changed after [[Hurricane Allen]] occurred in 1980 and an unknown disease spread across the Caribbean. In the wake of these events, massive damage was caused to both the reefs and sea urchin population across Jamaican's reefs and into the Caribbean Sea. As little as 2% of the original sea urchin population survived the disease.<ref name="Knowlton-2001" /> Primary macroalgae succeeded the destroyed reefs and eventually larger, more resilient macroalgae soon took its place as the dominant organism.<ref name="Knowlton-2001" /><ref name="Edmunds-2001">{{Cite journal|last1=Edmunds|first1=P. J.|last2=Carpenter|first2=R. C.|date=2001-03-27|title=Recovery of Diadema antillarum reduces macroalgal cover and increases abundance of juvenile corals on a Caribbean reef|journal=Proceedings of the National Academy of Sciences|language=en|volume=98|issue=9|pages=5067–5071|doi=10.1073/pnas.071524598|pmid=11274358|pmc=33164|issn=0027-8424|doi-access=free}}</ref> Parrotfish and other herbivorous fish were few in numbers because of decades of overfishing and bycatch at the time.<ref name="Edmunds-2001" /> Historically, the Jamaican coast had 90% coral cover and was reduced to 5% in the 1990s.<ref name="Edmunds-2001" /> Eventually, corals were able to recover in areas where sea urchin populations were increasing. Sea urchins were able to feed and multiply and clear off substrates, leaving areas for coral polyps to anchor and mature. However, sea urchin populations are still not recovering as fast as researchers predicted, despite being highly fecundate.<ref name="Knowlton-2001" /> It is unknown whether or not the mysterious disease is still present and preventing sea urchin populations from rebounding. Regardless, these areas are slowly recovering with the aid of sea urchin grazing. This event supports an early restoration idea of cultivating and releasing sea urchins into reefs to prevent algal overgrowth.<ref>{{Cite journal|last1=McClanahan |first1=T.R.|last2=Kaunda-Arara|first2=B. |date=August 1996|title=Fishery Recovery in a Coral-reef Marine Park and Its Effect on the Adjacent Fishery|journal=Conservation Biology|volume=10|issue=4|pages=1187–1199 |doi=10.1046/j.1523-1739.1996.10041187.x|bibcode=1996ConBi..10.1187M |issn=0888-8892}}</ref><ref>{{Cite journal|last=Sammarco|first=Paul W.|date=1980 |title=Diadema and its relationship to coral spat mortality: Grazing, competition, and biological disturbance|journal=Journal of Experimental Marine Biology and Ecology|language=en|volume=45|issue=2 |pages=245–272|doi=10.1016/0022-0981(80)90061-1|bibcode=1980JEMBE..45..245S |issn=0022-0981}}</ref>