How healthy is the marine ecosystem?
The health of a marine ecosystem can be expressed by various indicators. For St Eustatius and Saba, marine ecosystem health is shown in the Reef Health Index, on a scale from 1 (critical) to 5 (very good). For Bonaire, an indication of reef health is the percentage of coral bleaching.
| Year | Coral cover |
|---|---|
| 2021 | 2.89 |
| 2020 | 2.82 |
| 2019 | 4.57 |
| 2018 | 4.21 |
| 2017 | 5.07 |
| 2016 | 4.99 |
| 2015 | 5.00 |
| 2014 | . |
| 2013 | . |
| 2012 | . |
| 2011 | . |
| 2010 | . |
| 2009 | . |
| 2008 | 6.50 |
| 2007 | . |
| 2006 | . |
| 2005 | . |
| 2004 | . |
| 2003 | . |
| 2002 | . |
| 2001 | . |
| 2000 | . |
| 1999 | 23.00 |
| No data available for 2000 to 2007, 2009 to 2014 | |
The Reef Health Index score is determined by the presence of coral cover, microalgae cover (growing partly on the corals), herbivorous fish (that eat algae) and commercially important large groupers and snappers (which eat smaller fish and are in turn eaten by people).
Coral cover nearly the same in 2020 and 2021
Over the past five years, St Eustatius’ marine ecosystem health has been stable, scoring 3 (fair) on the Reef Health Index due to the ‘very good’ biomass levels of key herbivorous fish and commercially important fish, and despite the critically low health of the coral reefs themselves. The coral cover (2.9 percent) was nearly the same in 2020 as in 2021. At the same time, key commercial fish populations have been declining since 2018, but are still large enough to be rated as ‘very good’ biomass levels.
| Year | Key commerical fish, St Eustatius [g/100m2] |
|---|---|
| 2021 | 5623 |
| 2020 | 7379 |
| 2019 | 7940 |
| 2018 | 11897 |
| 2017 | 9299 |
| 2016 | 1680 |
| 2015 | 1670 |
| 2014 | . |
| 2013 | . |
| 2012 | . |
| 2011 | . |
| 2010 | . |
| 2009 | . |
| 2008 | 2261 |
| 2007 | . |
| 2006 | . |
| 2005 | . |
| 2004 | . |
| 2003 | . |
| 2002 | . |
| 2001 | . |
| 2000 | . |
| 1999 | 921 |
| No data available for 2000 to 2007 and 2009 to 2014 | |
Saba Bank’s Reef Health Index considered poor
The Saba Bank, a submarine atoll three to six kilometres south of Saba, is the largest protected nature area of the Netherlands at a size of 2,200 km2. The Saba Bank is home to many organisms, including coral reefs, fish, lobsters, sea turtles, whales and dolphins. In 2018, the Saba Bank’s Reef Health Index was considered poor with a score of 2.25, due to a low coral cover (5.7 percent) and a low fleshy macroalgae cover (11.3 percent).
| Year | 10 metres depth | 25 metres depth |
|---|---|---|
| 2016 | 15.70 | 35.77 |
| 2017 | 44.19 | 65.35 |
| 2019 | 14.94 | 33.48 |
| 2020 | 55.90 | 66.62 |
| No data available for 2018 | ||
The percentage of corals affected by coral bleaching in Bonaire during warm water events (temporarily warming of seawater, for example through the occurrence of La Nina or El Nino) is determined by human-induced climate change. Corals bleach as a stress response to changing temperature, light or nutrients. Coral bleaching is measured at both 10 and 25 metres depth. Generally, more corals bleach at 25 than at 10 metres depth. For each event in the past few years, the percentage of coral affected was directly related to the temperature of the surface waters and the duration of the event. Each year, the corals recover from bleaching because the stress event was not too intense or too long in duration.
More information on marine health in the waters around St Eustatius, Saba and Bonaire