Meesters, H.W.G.

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Saba Bank; health status 2010 
Cruise report 
 
Erik H.W.G. Meesters 
IMARES 
December 2010 
 
The author was funded by the Ministry of Economic Affairs, Agriculture and Innovation under 
project number BO-11-007-000-IMARES-11. 
 
 
The research is part of the CARIBSAT project (http://www.caribsat.com) part of the European 
INTERREG IV program, led by the IRD Martinique. Within CARIBSAT this sub-project is the Marin 
Habitat project led by J.P. Maréchal from the Observatoire du Milieu Marin de le Martinique 
(OMMM). 
 
 
 
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Introduction 
Helpdesk question number HD3284 from the ministry of Economic Affairs, Agriculture and 
Innovation is intended to provide some perspective on the health status of the coral reefs of the 
Saba Bank. 
 
The Saba Bank is the largest atoll in the Caribbean Sea located just a few miles west of Saba. It 
consists of a relatively shallow bank of 40 by 60km that is mostly between 40 and 12m deep 
and that is fringed by coral reefs along the eastern and southern edges. Recently, a special 
issue of the journal Plos One (issue 5, 2010) has been devoted to the Saba Bank giving a good 
overview of the high biodiversity of the Bank. 
 
Director of the Institute (OMMM), Jean-Philippe Maréchal, gave the opportunity to participate in 
his project which is part of the European CARIBSAT project. This project aims at developing 
techniques to classify reefs using remote sensing methods to monitor shallow reefs in the 
Caribbean area. As the Saba Bank is very large, remote sensing is likely to be a good method to 
gain insight into where what communities are on the Bank. Previous research ((Van der Land, 
1977, Meesters et al., 1996), PLOS ONE issue 5, 2010) showed that the Saba Bank has large 
stretches of reef, algal fields, rubble fields, and big areas that are mainly covered by sand. Good 
classification maps of the Bank may help to identify important areas with high biodiversity. 
From 11 till 22 November 2010 a team of 8 people visited the bank to collect data for the 
CARIBSAT project. The team consisted of Jean-Philippe Marechal (OMMM), Paul Hoetjes (RCN), 
Marine Fumaroli (OMMM), manager of the Saba Marine Park (SMP) Kai Wulf (SCF), assistant 
manager of SMP Gregoor van Laake, manager of Bonaire Marine Park Ramon de Leon (STINAPA 
Bonaire), and Erik Meesters (IMARES). Data consisted of spectral light data coming from the 
substrate at many locations together with video footage of the bottom and 2-3 50m transects of 
coral communities at a number of sites along the edge of the Saba Bank. 
 
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Materials and Methods 
The Bank covers a very large area and the sea is generally rough. This means that going out 
and back to the Bank takes much time. Within 11 days we were able to go to the bank 7 times 
(). Each time we tried to make one or two dives on different places. At each place 2 to 3 belts of 
50m length were surveyed. Each belt was high resolution videotaped by one diver, while the 
others collected data on the species of fish, the number of bleached colonies, the number of 
corals with diseases, and the number of sea urchins. Additionally, we collected on many places 
of the Bank video footage with a camera that was lowered from the boat to the bottom of the 
Bank. In total camera drops were made on 200 spots of the Bank and under water video 
transects were made at 7 places (). Within a short period a very large amount of data was 
collected. This data now needs to be analyzed before any definitive conclusions can be made. In 
this report first impressions are presented regarding the health condition of the reefs at the 
visited locations. 
 
 
Figure 1. Saba Bank with positions where drops (   ) and dives ( ) where made. White lines 
represent the boat tracks. 
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Results and conclusions 
The main task of EM was to assess the health condition of the coral reefs of the bank. Only a 
very small part of the bank was visited during 7 dives, but together with the 200 video shots 
this gives a good impression of the status of the corals of the Saba Bank. Coral reef health is not 
clearly defined. Coral reefs are built by hermatypic corals which are mainly colonial organisms 
that live in symbiosis with algae (zooxanthellae). The reef bottom consists out of the skeleton of 
these animals as well as sediment that originates from the breakdown of coral colonies by other 
organisms (e.g. grazing fish, sea urchins, boring sponges). The total is cemented into a hard 
limestone bottom by different taxonomic groups of organisms. A reef is a very complex 
ecosystem built by coral colonies, that provide food and shelter to an enormous amount of 
species. The reef can only survive and grow under optimal conditions of low nutrient levels and 
clear waters. Next to that there are millions of intricate relationships between the organisms 
that inhabit a reef and that are important for a healthy functioning of the reef. A healthy reef 
thus is a reef in which all relationships between its inhabitants function properly. Because this is 
impossible to assess it is generally believed that a good impression of a coral reef's health can 
be obtained by observing the main components of the reef, i.e. the corals themselves. Further 
information may be obtained by including important components that fulfill important functions. 
For example, under the fish there are families such as the parrotfish that graze the algae of the 
reef. Corals and algae are dependent on light for their survival and algae may overgrow and kill 
corals. A high cover of algae may also hamper recruitment of corals which is necessary to 
balance the loss of coral colonies by environmental disturbances such as storms and hurricanes, 
predation or diseases. Therefore it is important to not have too many algae on a reef. Nutrient 
enrichment will generally lead to higher growth of algae and thus increase overgrowth of corals 
by algae. Grazing of algae is also carried out by sea urchins, however, the main urchin species 
in the Caribbean (Diadema antillarum) has been wiped out by a disease in 1983. A healthy coral 
reef generally has a relatively high cover of corals, much fish and other invertebrates and not 
too much algae. 
 
Reefs occur mainly along the eastern and southeastern edge of the Bank generally below 15m. 
In 2005 there was an extreme el ninjo event (Eakin et al., 2010) and corals all over the 
Caribbean were hit hard. In many places living cover decreased by more than 50 percent. The 
corals of the Saba Bank were probably no exception. Much of this mortality is still visible today 
as surface irregularities on coral colonies (e.g. Figure 2). 
 
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Figure 2. A large Montastrea faveolata colony of which most tissue has been killed. Only small pieces 
with living tissue are visible of this once large colony. The small remnants (also called ramets) may be 
hundreds of years old. Much of the killed surface is now covered by algae (Dictyota spp. And 
Lobophora variegate). 
 
 
The general impression is that the Bank is still recovering from the 2005 disaster (Table 1). 
Furthermore it was observed that there also is a high cover of algae (mainly Dictyota spp. and 
Lobophora spp.) on the reefs of the Bank. Coral cover increases through growth of colonies and 
through the settlement of new colonies on substrate. Substratum that is covered by algae is not 
available for the settlement of coral larvae. Black sea urchins, which are an important grazer of 
algae, were not observed, though they are recovering in many reefs around the Caribbean(e.g. 
Vermeij et al., 2010). Fish numbers appeared to be lower than previously observed, though we 
observed sharks almost on every dive, indicating that there still is an intact food chain. The low 
numbers of fish may be a seasonal effect, a result of the presence of predators, or a result of 
changes that followed from the 2005 bleaching event. Hardly any coral colonies with diseases 
were observed and although some colonies were bleached as result of the seasonal high water 
temperatures, there appeared to be almost no mortality among these bleached colonies. 
 
Table 1. Overview of positive and negative observations. 
Optimistic 
-no diseases 
-no recent bleaching mortality on coral colonies 
-large predators present 
 
Concern 
-no black sea urchins 
-high cover of algae 
-low numbers of fish and lobster 
 
In summary, the reefs of the Saba Bank have deteriorated since the first observations in 1972, 
1996, and 2002. Meesters et al. (1996) describe percentage coral cover at 7 locations to lie 
between 60-90%. These percentages were nowhere observed this time (the best site visited had 
an estimated coral cover of around 50%, however the videotapes still need to be analyzed). 
6 
 
Possibly this is caused by just one event, i.e. the 2005 bleaching, but there just aren't any data 
that exclude other reasons (for example overfishing, damaged reefs by anchors, or hurricanes). 
The absence of important grazers such as the black sea urchin is likely to slow down recovery, 
but still corals appear healthy and the reefs of the Saba Bank are probably slowly recovering to 
their previous grandeur. Meesters et al. (1996) also describe the virtual absence of diseases 
which appears still to be the case. 
It is important that monitoring of the coral reefs of the Bank and human impacts (e.g. fishery) is 
installed as soon as possible. Permanent video transects are planned to be installed in 2011 at a 
number of sites on the Bank. 
7 
 
Acknowledgements 
I like to thank Jean Philippe Maréchal for inviting me on this research cruise, Paul Hoetjes for 
setting up the contacts in the first place, and the Bonaire and Saba Marine Park managers 
Ramon Deleon and Kai Wulf, as well as park ranger Gregoor vander Lake for their good 
company. I thank Michel and Wes for their assistance during the field trip, taking us to the 
Bank, and their hospitality.  
 
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Abbreviations 
IMARES Institute for MArine Resources and Ecosystem 
Studies 
OMMM Observatoire du Milieu Marin de le Martinique 
RCN Rijksdienst Caribisch Nederland 
SCF Saba Conservation Foundation 
 
 
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References 
EAKIN, C. M., MORGAN, J. A., HERON, S. F., SMITH, T. B., LIU, G., ALVAREZ-FILIP, L., BACA, B., et 
al. 2010. Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005. 
PloS one, 5: -. 
MEESTERS, E. H., NIJKAMP, H. and BIJVOET, L. 1996. Towards sustainable management of the Saba 
Bank. 51 pp. 
VAN DER LAND, J. 1977. The Saba Bank - A large atoll in the norteastern Caribbean. FAO Fish. Rep., 
200: 469-481. 
VERMEIJ, M. J. A., DEBROT, A. O., VAN DER HAL, N., BAKKER, J. and BAK, R. P. M. 2010. Increased 
recruitment rates indicate recovering populations of the sea urchin Diadema antillarum on 
curacao. Bull. Mar. Sci., 86: 719-725. 
 
 


Saba bank; health status 2010

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