Major Disturbances of Reefs

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Extracts from two papers:
(i) Marine Major Ecological Disturbances of the Caribbean
EH Williams and L Bunkley-Williams. 2000. Infect Dis Rev 2000;2(3):110-127.
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(ii) The transformation of Caribbean coral communities since humans 1500–1959, K.L. Cramer et al., 2021 Ecol Evol. 2021 Aug; 11(15): 10098–10118.
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also shown:
(iii) World Population 1940-2024
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(iv) Global Energy Consumption
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(i) PAPER 1: Marine Major Ecological Disturbances of the Caribbean
EH Williams and L Bunkley-Williams. 2000. Infect Dis Rev 2000;2(3):110-127.

MMED (Marine Major Ecological Disturbances)
They cite 5 categories
1. CORAL REEF BLEACHING “Coral-reef bleaching and its associated mass mortalities are the largest and most long-term disturbances known…Major coral-reef bleaching events are caused by unusually elevated seawater temperatures…corals can survive after bleaching if temperatures return to normal, and if water quality is oligotrophic.
1986-88 Bleaching Complex
Minor bleaching occurred in widely scattered areas in the Atlantic and Pacific in 1986. In 1987, major bleaching was concentrated in the Caribbean (1,5-7,24-27,35,36)..Extensive partial mortalities of colonies, and some total mortalities of coral-reef organisms occurred (48), including the death of some giant 400 – 500 year old colonies. Also listed are bleaching events in 1979/80, 1982/3, 1989/91, 1994/96, 1997-99

“The largest mass mortality of a marine invertebrate that has ever been recorded occurred throughout the Western North Atlantic throughout 1983 and affected the longspine sea urchin, Diadema antillarium. This has recurred several times since, but no causative agent has ever been identified”…The major event in the D. antillarium mass mortality (DAMM) began off the Caribbean coast of Panama in January 1983 and spread with the prevailing water currents throughout the western North Atlantic until most areas were affected by January 1984. From 95 – 99% of all the longspine sea urchins died in areas where they were monitored. The mortality passed through each area so rapidly (3-4 days) that study of the disturbance was difficult (66).

Both mass mortalities and enzootics of fishes have occurred in the Caribbean Region…In the last 20 years a number of large-scale fish mass mortalities have occurred in the Caribbean Region…All of these affected a variety of fish, occurred over extensive geographic areas, and over a long time period.
Unfortunately they were also poorly documented.”

We define “corals” in this section as either stony coral (Scleractinia) or fire coral (Milleporina). Until a few years ago, Caribbean coral diseases were limited to coral-reef bleaching, white-band disease, and black-band disease (1,8,26,38,79,80). Now suddenly, we are faced with 20- 40 (depending on who counts) new, alarming, epizootic diseases, syndromes, or conditions of Caribbean corals and other coral-reef organisms (12-16,81-83) (Table 1). Most of these new disturbances are poorly known and the causative agents are unknown.” They comment in more detail on a few:

White-band disease
White-band disease (WBD) is a mysterious ailment of corals which causes the tissue to slowly strip off exposing the white skeleton. It usually begins at the base of a colony and slowly moves upward until the entire colony is killed. Green and brown algae colonize the bare skeleton and move up the colony just behind the wide white band of WBD. Some attacks by WBD begin in the middle of a colony (possibly other diseases), and sometimes the entire colony is not killed. However, colonies that recover from one attack often suffer relapses…In the late 1970s or early 1980s, an epizootic of whiteband disease (WBD) began which drastically reduced the abundance of elkhorn coral, Acropora palmata, and staghorn coral, A. cervicornis, in the Caribbean (1,84). These corals are the fastest growing reef-building corals in the Caribbean and their destruction may reduce the ability of coral reefs to recover from other disturbances.

Black-band disease
Black-band disease (BBD) is characterized by a band, arranged in an arc or circle, of darkly colored cyanobacteria (also called bluegreen algae) that slowly spreads across a stony coral leaving white bare skeleton behind. The white area is soon covered with filamentous green and brown algae producing a greenish-brown dead area ringed in white and black bands with normal appearing tissue in front of the leading edge of the band…We received reports from many Caribbean locations of an increase in the incidence of BBD in the late 1980s and early 1990s”

Fire-coral fungal disease (FFD)
Coral-reef bleaching apparently reduces the resistance of Caribbean fire corals (Millepora spp.) to a fungal associate living in the skeleton of fire corals. This agent attacks the living tissues of fire coral and kills them. This agent was discovered in the Florida Keys (87), but probably occurs throughout the Caribbean Region. This may explain why fire corals suffer mass mortalities following bleaching events. The new epizootic diseases (Table 1) may be benefiting from a similar situation.

Red-band disease
Red Band Disease (RBD) is one of the new, epizootic diseases (Table 1). It has been known to occur in sea fans since 1983 (88) and in stony corals (89), but has only recently become widespread and epizootic (14) [“Epizootic disease is a disease event in an animal population akin to an epidemic in humans.”]

Coralivorous (coral-eating) molluscs
“In the Caribbean, a coral-eating mollusc, Coralliophila abbreviata, has also begun to destroy Acropora spp. (4). We have also observed six outbreaks of Flamingo Tongues, Cyphoma gibbosum, killing Caribbean gorgonians (unpublished).”

Sudden reef demise
At Parque Nacional Morrocoy, Estado Falcón, Venezuela: “In January 1996, an unusual upwelling event, combined with large river outflows and poor water circulation, nutrified waters around the park, causing a massive plankton bloom. The reefs became covered with a mucus layer produced by the dinoflagellates and diatoms. Very calm seas allowed the bloom to remain in the park for a week. Almost all of the anemones, annelids, corals, crustaceans, echinoderms, fishes, gorgonians, sipunculids, sponges, and other coral-reef organisms were smothered by the mucus layer and died from anoxia (93). This sudden destruction of an entire coral reef and all its inhabitants was unprecedented in the Caribbean… We do not list this catastrophic elimination of an entire reef system as a new disease or syndrome (Table 1) because we hope it was a unique event.”

Fibropapillomas in sea turtles (Figure 3) are large (up to 30cm) lobate tumours on the skin, scales, scutes, eyes, mouth or viscera. They may cause disfigurement and interfere with vision, breathing, feeding and swimming. Fibropapillomas in sea turtles, and especially green turtles, Chelonia mydas, were first described more than 50 years ago in the Florida Keys. Until recently these tumours were very rare, but they have greatly increased in abundance in the last 20 years in Florida and Hawaii, and in the last 15 years in the Caribbean (2).

“Caribbean sponges (Porifera) suffered an early mass mortality, and some species have experienced general declines even to extirpation. More recently, recurring sponge blights and a new, undefined disease (Table 1) have begun to threaten these animals.”
One example: Florida Keys sponge blights 1983, 1987 & 1992 Mass mortalities of sponges occurred in the Florida Keys in the summers of 1983, 1987 (1) and 1992. The first two events coincided with major coral-reef bleaching and seawater temperatures elevated above the normal maximae in the same areas, and the last with a mass mortality of many organisms in Florida Bay (103).

“Toxic algal outbreaks or “Red or Brown Tides” are increasing in number, size, geographic extent, and types of toxic agents involved worldwide…”
“Algal overgrowth of both coral reefs and seagrass beds has become a serious problem in the Caribbean (Table 1)…Increased growth of algae seems to be threatening Caribbean coral reefs. Algal problems on Caribbean reefs are circumstantially and logically correlated with the loss of longspine sea urchins following the DAMM, loss of other herbivorous organisms, such as fish due to over fishing, and increases
in nutrification. To a certain extent, many of the organisms that once controlled the algae have been lost and increased nutrient levels, which encourage additional algal growth, have occurred on all Caribbean reefs. Combined with the impact of other disturbances, algal over growth has drastically reduced the amount of coral cover, for example, 3-5% in Jamaica (60,108).”

“- A mass mortality of the common sea fan occurred along the Caribbean coast of Costa Rica in 1982 (110), and later on the Caribbean coast of Colombia (111).

“- Aspergillosis (fungal disease) of sea fans (SFD) This alarming condition suddenly appeared in sea fans
across the Caribbean (112) (Table 1). It causes holes or lesions to open in the blade of the fan and the gradual loss of all tissue down to the axial skeleton (113).”


“[THE CARIBBEAN REGION] has by far, the greatest number and severity of coral-reef-associated MMEDs on the planet…A vast complex of human-related sins are killing the Caribbean coral reefs. These causes are direct (over fishing, pollution, sedimentation, anchor impact, coral harvest, etc.) and indirect (global warming due to green house gasses, increased UVB due to global destruction of the ozone layer, and global pollution) (1,12-15,59). We have attacked the reef internally, removing many of its key components, and externally changing the physical parameters to exceed the narrow band of conditions under which it evolved and in which it can survive.

“The Caribbean is a “small fish bowl” compared to other coral-reef systems in the world. It is more easily destroyed. However, parts of these other coral-reef systems are already in as bad or worse condition. Their collapse may take a bit longer, but they will follow. Saving the coral reefs is no longer an option. We should now consider if we can save other ecosystems, and ultimately ourselves.”


(ii) PAPER 2: The transformation of Caribbean coral communities since humans 1500–1959, K.L. Cramer et al., 2021 Ecol Evol. 2021 Aug; 11(15): 10098–10118.

Abstract: The mass die‐off of Caribbean corals has transformed many of this region’s reefs to macroalgal‐dominated habitats since systematic monitoring began in the 1970s. Although attributed to a combination of local and global human stressors, the lack of long‐term data on Caribbean reef coral communities has prevented a clear understanding of the causes and consequences of coral declines. We integrated paleoecological, historical, and modern survey data to track the occurrence of major coral species and life‐history groups throughout the Caribbean from the prehuman period to the present. The regional loss of Acropora corals beginning by the 1960s from local human disturbances resulted in increases in the occurrence of formerly subdominant stress‐tolerant and weedy scleractinian corals and the competitive hydrozoan Millepora beginning in the 1970s and 1980s. These transformations have resulted in the homogenization of coral communities within individual countries. However, increases in stress‐tolerant and weedy corals have slowed or reversed since the 1980s and 1990s in tandem with intensified coral bleaching and disease. These patterns reveal the long history of increasingly stressful environmental conditions on Caribbean reefs that began with widespread local human disturbances and have recently culminated in the combined effects of local and global change.

And  from the discussion, a section whihc  underscores  the  increasing significance of nutrient pollution:

“In contrast to the early transformation of Caribbean coral communities following the initial loss of Acropora in the 1950s/1960s, more recent changes since the 1980s/1990s demonstrate the heightened effects of local stressors and climate change acting on reefs simultaneously. Although our study suggests that White Band Disease was not the cause of initial Acropora declines, it confirms that it has unequivocally contributed to the loss of this genus: the second significant Acropora decline observed in our time series in the early 1980s immediately followed the first instances of this disease reported in the late 1970s (Gladfelter, ). Land‐based runoff has been shown to exacerbate coral bleaching and disease (Bruno et al., ; Lapointe et al., ; Wiedenmann et al., ), suggesting that reef eutrophication played a role in the emergence of these morbidities. Similarly, the region‐wide plateaus/declines in stress‐tolerant and weedy corals we observed since the 1980s/1990s reveal that local and global stressors are making Caribbean reef environments less suitable for those corals with the hardiest of life‐history strategies. Indeed, recent monitoring efforts have documented declines in several stress‐tolerant taxa from bleaching and disease that were initiated two decades ago (Edmunds & Elahi, ; Harvell et al., ) and show that several stress‐tolerant species are currently rapidly succumbing to the highly lethal Stony Coral Tissue Loss Disease that does not affect Acropora (Precht et al., ; Weil et al., ; van Woesik & Randall, ). Monitoring efforts are also documenting declines in weedy corals such as Agaricia due to recent Caribbean‐wide bleaching events (Walton et al., ). Finally, thermal stress and algal overgrowth are causing recruitment failure in Caribbean coral species regardless of life‐history guild (Arnold et al., ; Hughes & Tanner, ; Randall & Szmant, ). Thus, the shifts documented in our 131,000‐year record indicate a long history of increasingly stressful environmental conditions on Caribbean reefs that began with local human disturbances and have culminated in the combined effects of local and global change.”

From Table A1 in Cramer et al., 2021:  Time bins included in the analysis of long‐term change in Caribbean coral communities and significant events affecting reef environments and detection of ecological change by researchers. Timeline sourced from Jackson et al. (2014) and Cramer, Jackson et al. (2020)

Pleistocene (131,000–12,000 years ago) Period prior to human settlement in Caribbean; high‐magnitude fluctuations in sea level and climate with transitions from glacial to interglacial periods
Holocene (9,100 years ago–1500 AD) Humans settle in Caribbean; sea‐level rise (following last glacial period) slows and sea level begins to stabilize; first European contact in Caribbean
1500–1959 Increasing utilization of reef resources by European colonizers; decline of indigenous populations from genocide and disease; first application of synthetic pesticides and fertilizers in Caribbean watersheds in 1950s; first widespread application of synthetic pesticides on agricultural crops in the Caribbean in 1950s
1960–1969 Increase in fertilizer use and pesticide imports in Caribbean region
1970–1979 First recorded incidence of White Band Disease in Caribbean Acropora corals; first signal of anthropogenic ocean warming in Caribbean; first systematic monitoring of Caribbean reefs
1980–1984 Mass die‐off of urchin Diadema antillarum due to disease in 1982–1983; increase in macroalgae on many Caribbean reefs
1985–1989 First warming‐related coral bleaching outbreaks
1990–1994 First regional‐scale coral bleaching in Caribbean; increase in coral disease outbreaks; intensification of region‐wide reef monitoring programs
1995–1999 Extreme heating event resulting in mass coral bleaching in 1998
2000–2004 Massive loss of reef architectural complexity following coral bleaching in 1999
2005–2011 Extreme heating events and coral bleaching outbreaks in 2005 and 2010

(iii) World Population, from

Year Population Gr. Rate
2024 8,118,835,999 0.91% 2023 was first year over 8 billion
2020 7,840,952,880 0.98%
2010 6,985,603,105 1.27% 2011 was first year over 7 billion
2000 6,148,898,975 1.34% 1999 was first year over 6 billion
1990 5,316,175,862 1.77%
1980 4,444,007,706 1.80% 1987 was first year over 5 billion
1970 3,695,390,336 2.06% 1975 was first year over 4 billion
1960 3,019,233,434 1.65% 1960 was first year over 3 billion
1950 2,499,322,157 0.00%

1940 approx. 2.3 billion

(iv) Global Energy Consumption

Screen Capture of chart in: Global Energy Consumption by Source, and Carbon Emissions (1900-2021) by Truman Du on the, Accessed Feb 12, 2024. Remarkably ” Despite its relative share decreasing over time, as of 2021, coal remains the second biggest energy source, accounting for 25% of the world’s energy needs.” Note the massive increase in energy consumption between 1950 and 2000 – 4.3 fold; population increased 2.8 fold over the same interval. The world was being rapidly industrialized.

On storm activity, warming etc
Hurricanes have been affecting the Caribbean for centuries…Historically, the island which has suffered the least due to these natural disasters is Barbados as it is the most easterly island in the island chain, and tends not to be in the direct path of most hurricanes affecting the region. “Dean” 2007, “Ivan” 2004, “Lenny” 1999, and “Luis” 1995 are perhaps some of the most memorable hurricanes to hit the region.

Marine heatwave events
-Bove CB, Mudge L, Bruno JF. A century of warming on Caribbean reefs. PLOS Clim. 2022. 1: e0000002.  “Caribbean coral reefs now experience on average 5 marine heatwave events annually, compared to 1 per year in the early 1980s, with recent events lasting on average 14 days. These changes in the thermal environment, in addition to other stressors including fishing and pollution, have caused a dramatic shift in the composition and functioning of Caribbean coral reef ecosystems.”

Sea-level rise
Cazenave A, Palanisamy H, Ablain M.  Contemporary sea level changes from satellite altimetry: What have we learned? What are the new challenges? Advan Space Res. 2018; 62: 1639-1653. “Since the early 1990s, high-precision multi-mission satellite altimetry has provided a 25-year-long sea level record from which global mean sea level rise and superimposed interannual and regional variability can be derived. Most recent results show that the global mean sea level is rising at a mean rate of 3.1 ± 0.3 mm/yr since January 1993. A clear acceleration is also visible on this 25-year time span, estimated to 0.10 mm/yr2.”

Wave energy
– Reguero BG, Losada IJ, Méndez FJ. A recent increase in global wave power as a consequence of oceanic warming. Nat Commun. 2019; 10: 205. “Results indicate the upper-ocean warming, a consequence of anthropogenic global warming, is changing the global wave climate, making waves stronger.”