Located in the Dutch Windward Islands, Saba Bank is a flat-topped seamount (20–45 m deep in the shallower regions). The primary goals of the survey were to improve knowledge of biodiversity for one of the world’s most significant, but little-known, seamounts and to increase basic data and analyses to promote the development of an improved management plan.
Our team of three divers used scuba to collect algal samples to depths of 50 m at 17 dive sites. Over 360 macrophyte specimens (12 putative new species) were collected, more than 1,000 photographs were taken in truly exceptional habitats, and three astonishing new seaweed community types were discovered. These included: (1) ‘‘Field of Greens’’ (N 17u30.6209, W 63u27.7079) dominated by green seaweeds as well as some filamentous reds, (2) ‘‘Brown Town’’ (N 17u28.0279, W 63u14.9449) dominated by large brown algae, and (3) ‘‘Seaweed City’’ (N 17u26.4859, W 63u16.8509) with a diversity of spectacular fleshy red algae.
Dives to 30 m in the more two-dimensional interior habitats revealed particularly robust specimens of algae typical of shallower seagrass beds, but here in the total absence of any seagrasses (seagrasses generally do not grow below 20 m). Our preliminary estimate of the number of total seaweed species on Saba Bank ranges from a minimum of 150 to 200. Few filamentous and thin sheet forms indicative of stressed or physically disturbed environments were observed. A more precise number still awaits further microscopic and molecular examinations in the laboratory. The expedition, while intensive, has only scratched the surface of this unique submerged seamount/atoll.
Combining the findings of this study with that of other studies, the authors conclude that the coral assemblage on the Saba Bank is diverse and healthy; it is representative and typical of those found elsewhere in the Caribbean.
- A total of 43 species were documented.
- There were no significant differences in coral composition amongst bottom types or depth classes.
- There was a significant difference between sites near and far from the platform edge. The number of coral species observed ranged from 0 and 1 in algal dominated habitats to 23 at a reef habitat on the Bank’s southern edge.
- Coral species richness was higher on reef dominated areas as opposed to algal dominated ones.
- Bleaching was evident at 82% of the sites assessed with 43 colonies bleached.
- Only three coral colonies were observed to have disease.
- Five reef sites had stands of Staghorn Coral (Acropora cervicornis), a critically endangered species on the IUCN Red List.
- No physical damage consistent with anchor usage or sand scour from shipping activity was noted at any of the sites assessed.
- Immediate action is necessary to protect the diverse coral reef habitats documented.
- The five healthy stands of staghorn coral (A. cervicornis) and their surrounding should be given highest priority for full protection in the zoning use plan under development (in consultation with all stakeholders).
- More information is needed on the Saba Bank to create a comprehensive zone use plan. For example, more sites need to be studied so as to get a more comprehensive coverage of the bank’s coral composition.
The main conclusion of this study is that the shallow, warm and saline back-water habitat which is continuing to increase in importance within Lac Bay is unable to support meaningful mangroves, seagrass or algal meadows, nor the key nursery species. As the natural process of land reclamation by mangroves carries on, the bay’s important nursery habitats will come under additional salinity stress and likely continue to decrease in coverage and quality at an accelerated rate.
Distribution of sea grass and algal beds in Lac Bay
- The valuable seagrass and mangrove habitats of Lac are currently trapped in an enclosed bay.
- High light-intensity and well-circulated shallow habitats that fringed the mangroves of the central bay have the richest assemblages with the highest biotic coverage.
- Isolated mangrove pools have the lowest total cover, species richness and biodiversity of all habitats.
- Biotic diversity and cover decrease towards the deeper parts of the bay.
- There is an alarmingly rapid invasion of the bay by the invasive seagrass H. stipulacea.
Fish species utilization of contrasting habitats in Lac Bay
- Fish community variables differ consistently among habitats and are influenced by the percent cover of seagrass vegetation or presence of mangrove-root structure.
- Mangrove fringe habitats are a premier habitat since multiple life stages of a variety of species showed highest densities there. Mangrove fringing open waters had highest overall fish densities and species diversity.
- The various vegetated sub-habitats all play a unique role for different size-classes of different fish species.
- Management action is needed to stem further erosion of nursery habitat quality and ensure that a tipping-point is not reached beyond which recovery may be difficult or impossible.
- Measures should be taken to help restore water depth and circulation to relieve the bay’s ecosystem of thermal and salinity stress caused by the shallow backwaters. This includes excavating accumulated erosional and biogenic sediments as well as dredging to restore former feeder channels by removal of mangrove overgrowth (as already started by Stinapa).
- Further studies to assess the impacts of the invasive seagrass H. stipulacea on the bay’s flora and fauna.
Het Bonaire National Marine Park (BNMP) staat sinds 2011 op de Nederlandse Voorlopige lijst van het Werelderfgoed. Dit betekent dat een nominatie kan worden ingediend om als natuurlijk werelderfgoed erkend te worden. In dit rapport wordt beschreven welke stappen nodig zijn om tot een nominatie voor de status van werelderfgoed te komen.
De ‘Outstanding Universal Value’ (datgene wat het gebied wereldwijd uniek maakt) moet worden aangetoond. Hierbij zijn drie aspecten van belang:
- Het gebied moet voldoen aan minimaal één van de vier door UNESCO gestelde criteria voor natuurlijke werelderfgoederen;
- Het gebied moet voldoen aan condities voor integriteit;
- Het beheer van het gebied moet voldoende zijn om de kwaliteit van het ecosysteem van het BNMP veilig te stellen voor de komende generaties.
Verder moet het gebied en haar OUV worden vergeleken met vergelijkbare werelderfgoed gebieden en met vergelijkbare gebieden elders in de wereld door middel van een Comparative Analysis.
De hele procedure is in dit rapport samengevat in een schematisch stappenplan. Omdat er zware eisen gesteld worden aan de nominatie zijn in dit stappenplan ook beslismomenten aangegeven waarop aan bepaalde voorwaarden voldaan moet zijn om verder te gaan met de aanvraag (zogenaamde ‘go/no-go’ momenten).
Aangezien de hele procedure de nodige financiële middelen vraagt, moet min of meer zeker zijn dat de nominatie haalbaar lijkt voordat aan de verschillende onderdelen van de nominatie begonnen wordt.
Biodiversity surveys were conducted on Saba Bank, Netherlands Antilles, to assess ichthyofaunal richness and to compare with published surveys of other Caribbean localities. The primary objective was to estimate the total species richness of the Saba Bank ichthyofauna. A variety of sampling techniques was utilized to survey the fish species of both the visually accessible megafauna and the camouflaged and small-sized species comprising the cryptic ichthyofauna. Based on results presented herein, the number of species known on Saba Bank is increased from 42 previously known species to 270 species. Expected species-accumulation curves demonstrate that the current estimate of species richness of fishes for Saba Bank under represents the actual richness, and our knowledge of the ichthyofauna has not plateaued. The total expected fish species richness may be somewhere between 320 and 411 species. The Saba Bank ichthyofaunal assemblage is compared to fish assemblages found elsewhere in the Caribbean. Despite the absence of shallow or emergent shore habitats like mangroves, Saba Bank ranks as having the eighth highest ichthyofaunal richness of surveyed localities in the Greater Caribbean. Some degree of habitat heterogeneity was evident. Fore-reef, patch-reef, and lagoonal habitats were sampled. Fish assemblages were significantly different between habitats. Species richness was highest on the fore reef, but 11 species were found only at lagoonal sites. A comprehensive, annotated list of the fishes currently known to occur on Saba Bank, Netherland Antilles, is provided and color photographs of freshly collected specimens are presented for 165 of the listed species of Saba Bank fishes to facilitate identification and taxonomic comparison with similar taxa at other localities. Coloration of some species is shown for the first time. Preliminary analysis indicates that at least six undescribed new species were collected during the survey and these are indicated in the annotated list.
The main conclusion from this study is that the health of the reefs of the Saba Bank has deteriorated since the first observations in 1972, 1996, and 2002. The general impression is that the Bank is still recovering from the 2005 bleaching disaster, but there is not enough data to exclude other reasons (e.g. overfishing, anchor damage, hurricanes).
- In 1996, Meesters et al. estimated coral cover at 7 locations to lie between 60 and 90%. These percentages were nowhere observed this time. The best site visited had an estimated coral cover of around 50%.
- There is now a high cover of algae (mainly Dictyota spp. and Lobophora spp.) on the reefs of the Bank.
- The present absence of important grazers such as the black sea urchin are likely to slow down recovery.
- Fish numbers appeared to be lower than previously observed, though sharks were observed on almost every dive, indicating a still 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.
However, corals appear healthy and the reefs of the Saba Bank are probably slowly recovering to their previous grandeur.
- Very few coral colonies with diseases were observed.
- Some colonies were bleached as result of the seasonal high water temperatures, but there appeared to be almost no mortality among these bleached colonies.
Begin to regularly monitor the health of the Bank’s coral reefs and the impact of human activities such as fishing as soon as possible (permanent video transects are planned to be installed in 2011 at a number of sites on the Bank).
A preliminary inventory is given of key terrestrial nature values of Bonaire in order to determine their occurrence in relation to areas designated as “nature” and “open landscape”, according to the Spatial development plan of Bonaire. This was based on a literature study and supplemented by expert advice.
In 2010 a spatial development plan was written in order to determine the spatial policy and regulation for the future development of Bonaire. The island was partitioned into areas for different uses such as agriculture and recreation. Two specific designations are “nature” and “open landscape”. The occurrence of nature values within these areas remained unclear. This makes implementation of protective measures based on international treaties and island legislation problematic. An inventory of the occurrence of these values should help facilitate more effective implementation of these protective measures. In the present study key nature values are determined, both in terms of protected species and essential habitat (e.g. caves).
From the literature study it became apparent that data on the occurrence of most of the priority species of flora and fauna, is limited and scattered, especially with respect to “open landscape” and “nature” outside parks. Therefore, only a preliminary inventory is provided showing the general distribution of nature values across the entire island, as linked to various habitat types. An exact distribution of the different nature values was not possible at this time, but extrapolation from areas of known occurrence into other areas of similar habitat type was used to show the occurrence of overlapping distributions of nature values within the designated areas of “nature” and “open landscape”. The number of overlapping distributions of nature values may contribute to setting conservation priorities.
From the results it can be concluded that the areas of “open landscape” and “nature” (outside the national parks) seem to harbour unique and critical nature values. These areas are not actively managed or protected as national parks. The “open landscape” of Bolivia possibly harbours a few rare plant species (unique), an important population of critical key columnar cacti and at least two columnar cactus-pollinating bat species. The “open landscape” of Washikemba/Bakuna harbours key mangrove species that only have another main location at Lac Bay (national park). The “nature” area of Terrace Landscape Middle Bonaire seems to harbour a concentration of unique (e.g. Tillandsia balbisiana) and rare plant species (e.g. Krugiodendron ferreum etc.) and four bat species. The same is the case for Lima (e.g. Sabal palm, Maytenus versluysii and three bat species) while in Southern Bonaire key mangrove species also still occur. Table 1 shows which nature values are found or expected to occur within each “open landscape” and “nature” (outside national parks) area.
It can be concluded that outside the current parks, the main regions that harbour a concentration of key nature values are Terrace Landscape Middle Bonaire/Sta. Barbara, Bolivia, Washikemba/Bakuna and Lima. Terrace Landscape Middle Bonaire is designated as “nature” area, while Washikemba/Bakuna and Bolivia are in part designated as “open landscape”. Lima has both “nature” and “open landscape” designations. Sta. Barbara is designated for other uses, but the present review shows that the occurrence of several significant nature values is likely within this area.
Additionally, based on the preliminary inventory, the combination of apparent concentrations of rare plants, occurrence of critical bat species and the high probability of corridor values show that the areas of Terrace Landscape Middle Bonaire/Sta. Barbara and Lima are important areas concerning conservation and further research. The areas of Bolivia and Washikemba/Bakuna follow closely.
To be able to implement the necessary protective measures within these areas, it is recommended that more extensive research through fieldwork is done, in order to obtain a complete inventory of the different nature values found on Bonaire, not only in the areas of “nature” and “open landscape” but also in areas with other designations. Additionally, it is recommended to assess the list of vulnerable and endangered species (‘Informatieblad beschermde dier- en plantensoorten Bonaire’) as certain species that may be of importance to Bonaire are not included.
When executing a complete and extensive inventory of Bonaire it would be of value to also determine the ecological conditions needed for the different species to survive. Based on the ecological conditions necessary for their life functions, it may be possible to pinpoint those areas of main ecological importance per species. A complete inventory of the nature values on the island can contribute to better management of nature values (e.g. determining the distribution of caves and the distribution, health status and diversity of keystone cacti species for better management of bat populations). It is also recommended to determine areas with high potential for the occurrence of rare or relict species and which areas harbour high corridor values.
For future research it is recommended to execute a complete and extensive inventory of Bonaire, through fieldwork, in order to implement the necessary protective measures to ensure the conservation of these nature values. The present study shows that the areas of WNSP/Brasil, Terrace Landscape Middle Bonaire, Lima and Bolivia may be of priority as these areas seem to harbour a concentration of unique and critical plants.
Present studies shows that key nature values may occur in areas with a different designation than “nature” or “open landscape”. For future research it is recommended not to limit inventory research to the areas of “nature” and “open landscape”, but to include other areas with different designations.
In the present study the nature values chosen were based on the list of vulnerable and endangered species (Informatieblad beschermde dier- en plantensoorten Bonaire). During the study several species were added based on expert knowledge. The list used therefore seems to be limited. For future research it is recommended to assess if there are other nature values that are important to Bonaire that should be included on the list (e.g. Clusia sp, Ammodramus savannarum).
A complete inventory of the nature values on the island can contribute to the better management of nature values. A good example is the management of Bonaire’s bat population. In order to define the priority areas to maintain for the management of the different bats on Bonaire it is essential to obtain a detailed inventory of the different caves that these species use as habitat.
Additionally for the nectar-feeding bats it is crucial to map the occurrence of the different candle cacti on which they feed. The nectar-feeding bats are the critical pollinators of the three candle cacti (Petit, 2001). As already mentioned these cacti are key species on the island as they provide food for several species of animals during the dry season, when many other plant species are non-productive (Petit, 2001). Research on the distribution, health status and diversity of candle cacti on Bonaire is recommended in order to pinpoint priority areas for nectar- feeding bats. The cactus populations are threatened severely by feral livestock (goats, donkeys) which remove the bark of the mature trees, thereby threatening the food supply for frugivores and nectarivores. From our analysis open land areas of Bolivia would seem to possess large cactus populations of vital interest to conservation of endangered bird species on an island-wide scale.
When executing a complete and extensive inventory of Bonaire it would be of value to determine the ecological conditions and various habitats needed for the different species to survive. Based on the ecological conditions necessary for their life functions it may be possible to pinpoint those areas of principal ecological importance per species.
It is necessary to identify those areas with a high potential for the concentration of nature values rare species or relict vegetation species in order to secure the survival of these species and to be able to implement the necessary protective measurements. Such areas for instance are the open land and nature sections of Lima, Terrace Landscape Middle Bonaire (nature) and Bolivia (open). For future research it is recommended to determine those areas with high corridor values for the implementation of ecological corridors and buffer zones on Bonaire.
Botanical and zoological collections may serve as archives for historical ecologi- cal research on the effects of global change and human impact on coral reef biota. Museum collections may harbour old specimens of reef-dwelling species that have become locally extinct. Such collections also help to determine whether early records of invasive species can be obtained from times when they were not yet recognized as such. A case study (2006) involving Saba Bank, Caribbean Netherlands (former Netherlands Antilles), suggests that the coral reef fauna here may have become impoverished when compared with data obtained during an earlier expedition in 1972. However, the 1972 sampling may have been incomplete, as it was performed by professional divers who were not trained taxonomists, whereas the collecting in 2006 was done by expe- rienced marine biologists who knew the taxa they were sampling. As Saba Bank has been under stress due to the anchoring of large vessels, and invasive species have been a potential threat as well, future studies are needed to obtain more insights into the changing reef biota of Saba Bank. Using this Saba Bank exam- ple, we want to address the importance of natural history collections as reser- voirs of valuable data relevant to coral reef biodiversity studies in a time of global change. As such, these collections are still underexplored and underexploited.