dcdevil
New
I am very interested in figuring out why Caribbean coral reefs have declined so much in the last 30 or 40 years. There are many reasons for the deterioration of the reef, but it is clear that the die-off of the long-spined Diadema sea urchins in 1983 was and is still a major contributor to the loss of coral. Sea Urchins are instrumental in keeping algae in check and allowing room for corals. This summary by Martin Moe provides an excellent overview and summary:
"The large, pre-plague populations of Diadema that inhabited the reefs were efficient bioerroders of the limestone reef structure as well the keystone herbivores on the reefs. They created much of the coral sand that surrounds the reef and kept the reef substrates clear of the algae and sediment that inhibits the settlement and growth of juvenile corals. Algae and sediment now cover much of the reef structure so even when the remaining few corals successfully spawn in late summer and release millions of planula larvae, if there are only a few areas where the larvae can settle and grow, recruitment of new coral formations are few and far between...
Loss of this keystone herbivore has shifted the ecology of coral reefs from stony corals to dominance of macro algae and algal turf. Natural recovery of small pockets of Diadema populations in St. Croix , Jamaica, Belize, Dry Tortugas and other areas,... has shown that when adequate populations of Diadema are restored to coral reef areas, this trend is reversed and coral settlement and growth once again become dominant on the reef.
And Then They Were Gone
I am currently in St. Croix and have seen pockets of healthy sea urchins in large numbers in Coakley Bay, Chenay Bay, and many juvenile sea urchins in the very shallow rocky areas near shore in many locations in St. Croix including Boiler Bay and Coakley Bay. Also, while much of the elkhorn and staghorn is dead and gone, there are seemingly more and healthier brain corals, porites, pillar corals, and montastrea, as well as less algae.
I am wondering if other divers have seen evidence of any comeback of the sea urchins in other areas of the Caribbean?
"The large, pre-plague populations of Diadema that inhabited the reefs were efficient bioerroders of the limestone reef structure as well the keystone herbivores on the reefs. They created much of the coral sand that surrounds the reef and kept the reef substrates clear of the algae and sediment that inhibits the settlement and growth of juvenile corals. Algae and sediment now cover much of the reef structure so even when the remaining few corals successfully spawn in late summer and release millions of planula larvae, if there are only a few areas where the larvae can settle and grow, recruitment of new coral formations are few and far between...
Loss of this keystone herbivore has shifted the ecology of coral reefs from stony corals to dominance of macro algae and algal turf. Natural recovery of small pockets of Diadema populations in St. Croix , Jamaica, Belize, Dry Tortugas and other areas,... has shown that when adequate populations of Diadema are restored to coral reef areas, this trend is reversed and coral settlement and growth once again become dominant on the reef.
And Then They Were Gone
I am currently in St. Croix and have seen pockets of healthy sea urchins in large numbers in Coakley Bay, Chenay Bay, and many juvenile sea urchins in the very shallow rocky areas near shore in many locations in St. Croix including Boiler Bay and Coakley Bay. Also, while much of the elkhorn and staghorn is dead and gone, there are seemingly more and healthier brain corals, porites, pillar corals, and montastrea, as well as less algae.
I am wondering if other divers have seen evidence of any comeback of the sea urchins in other areas of the Caribbean?