Thresholds Database > Coral to brown algae, Caribbean Sea, South America

Certainty of shift: Demonstrated
Location: South America, Atlantic Ocean, Caribbean Sea, Jamaica
System Type: Social-Ecological
Regime Shift Category: 4a
Ecosystem Type
Coral reef
Spatial Scale
Type of Resource Use
Number of Possible Regimes
Ecosystem Service
Food, recreation, storm protection, ecotourism
Time Scale of Change
Resource Users
Fishers, boaters, tourists 
Reversibility of Shift


By the late 1960's, high levels of fishing had significantly reduced fish biomass and by the late 1970's, the reefs were damaged, through the direct and indirect effects of fishing.

Alternate Regimes

1. Coral

2. Brown algae

Fast or Dependent Variable(s)
Coral / brown algae species composition
Slow or Independent Variable(s)
Densities of fish and the sea urchin Diadema
Disturbance or Threshold Trigger(s)
Fishing, hurricanes, pathogen of Diadema
External / Internal Trigger


Fishing first reduced the number of large predatory fish and when these populations were exhausted, herbivorous fish were caught. These herbivorous fish and the sea urchin Diadema both feed on algae, keeping it's density in check. The loss of the herbivorous fish provided a greater food source for Diadema, whose numbers increased. In 1981, a hurricane hit the area, killing or damaging most of the branching coral species, allowing for even more algal growth. The benthic algae were still controlled by Diadema until 1982/1983, when a species-specific pathogen killed 99% of the Diadema population in some areas. Brown algae then became very abundant, out-competing the remaining coral colonies and preventing coral larvae from settling.

Management Decisions in Each Regime

Jacqui Meyers


CSIRO Sustainable Ecosystems,
PO Box 284,
Canberra ACT 2601

empirical data, Pollution