Central repository for biodiversity related research and monitoring data from the Dutch Caribbean
Video documentary describing the importance of the Saba Bank as a natural resource for the island of Saba, including underwater footage and interviews with fishermen and managers.
Abstract - Due to multiple stressors, many coral reefs are degrading. Shifts from a coral
dominated system to an alternate phase are observed. For coral reefs, the shift described most
in the scientific literature is a shift to an algae dominated system. However, shifts to other
dominant species are observed as well, including sponge or cyanobacteria dominance. It is
thought that sponges may become dominant when macroalgae or turf algae cover increases.
Algae are producers of dissolved organic matter (DOM), a food source for sponges.
Cyanobacteria are producers of DOM as well, although it remains unclear whether sponges
can use this. Furthermore, the decrease in spongivore fish due to overfishing, and the increase
in picoplankton can result in increasing sponge cover. In this study, benthic cover of eleven
sites at Saba Bank in 2013 and 2015 is assessed. Corals and sponges were identified to species
level, to get insight into assemblages. Using the program CPCe, photo quadrats (N=10) of two
transects per site were analyzed. The same photo quadrats were used for analysis of sponge
diversity, all sponges larger than 4 cm were identified to species level. Last, in 2015 92
specimens of sponges were sampled and identified using DNA barcoding and morphological
analysis. Close-up photos of these specimens were made, so that sponge identification guide
of Saba Bank can be developed. A shift from turf algae dominance to cyanobacterial
dominance among the years 2013 and 2015 was observed. Possibly, Saba Bank experiences
some influence from the nearby islands Saba, St. Eustatius, and St. Kitts and Nevis.
Macroalgae cover was found to be higher in the northern and northeastern parts of the bank
(closer to the islands), whereas coral cover was lower in these parts. The coral with highest
cover in the benthic survey was Montastraea faveolata (34.7% and 45.5% of total coral cover
in 2013 and 2015). Using multivariate analysis, year and water depth had a significant effect
on coral composition, position of the site had no significant effect suggesting connectivity
between sites for corals. The species Xestospongia muta and Agelas sventres contributed most
to total sponge cover (X. muta: 11% and 12.9%; A. sventres: 10.4% and 15.4% of total sponge
cover in 2013 and 2015). Water depth, northing and non living cover had a significant effect
on sponge composition. Altogether, sponge cover was not high on Saba Bank and therefore it
is not (yet) becoming a sponge reef. In 2015, Saba Bank was dominated by cyanobacteria, this
may be beneficial to sponges, since cyanobacteria are producers of DOM.
A dedicated Saba Bank Symposium was organised by the University of Wageningen in December 2016. The Symposium was held in Den Helder and brought together researchers and conservationists from throughout the Kingdom to share their knowledge and to provide an overview of the current state of scientific knowledge about the Netherland’s largest and most remote National Park.
Among others, presentations were given on the following topics:
The Symposium ended with a panel discussion on the sustainable use of the Saba Bank and what is needed to protect the Saba Bank for the future.
We have done our best to capture the wealth of information presented at the symposium for you in our BioNews letter and hope, that like us, you are impressed by the depth and diversity of the work that has been done to explore and document our largest National Park: The Saba Bank.
To read this interactive Pdf, please make sure to have Adobe Acrobat Reader installed on your computer. We recommend you to open BioNews in full screen. In case you do not have this program, please click here to download. Feel free to email research@DCNAnature.org in case you experience any issues downloading the program so we can assist you.
BioNews is produced by the Dutch Caribbean Nature Alliance and funded by the Ministry of Economic Affairs.
A small submersible remotely operated vehicle (ROV) was used to explore mid-depth habitats of Saba Bank – a submerged carbonate platform in the northeastern Caribbean Sea. The ROV enabled observation and specimen collection to greater depths (40 to > 150 m) than possible with conventional scuba methods. The topography, substrate, benthic communities and fish assemblages of a prominent front reef system at Overall Bank were examined in some detail. Observations made from ROV indicate that substrate and benthic communities show consistent zonation patterns along the depth gradient of the front reef slope. A transition in the reef fish assemblage was also evident, though less pronounced, along this same depth gradient. Fish diversity (number of species observed per survey) was greatest in the reef crest zone and declined with depth, however sightings of commercially important lutjanids species such as silk and blackfin snapper increased with depth. Significant cover by reef-building corals (i.e. constructional reef development) was only evident in the reef crest zone, and terminated at 38 to 42 m depth. Substrate of the transition slope zone, from 42 m to 75 m depth, was primarily a hard bottom consisting of consolidated reef structures and rubble with sand interspersed. Sponges, gorgonians and macro algae dominated the benthic community there. In the deep slope zone (> 75 m depth), a soft bottom substrate predominated that was composed of fine, readily resuspended sediments together with scattered rubble fragments. Benthic invertebrates were very sparse in the deep slope zone. In addition to the surveys at Overall Bank, four ROV surveys were made at two other Saba Bank areas: Poison Bank and Grapplers Bank. The substrate at Poison Bank was comprised of coralline algal nodules or “rhodoliths” which formed extensive rhodoliths beds. At Grapplers Bank, a steep rocky escarpment was explored. The near-vertical rocky scarp began at 120 m depth and extended down slope beyond the limits of the ROV survey (157 m depth). Observations made from ROV at Overall Bank suggested a continuous reef system that is relatively uniform and predictable at mid-depths in terms of its structure, substrate composition, and community zonation patterns. In contrast, the few observations made by ROV at Poison Bank and Grapplers Bank revealed habitats that were quite different from those at Overall Bank. This implies that future ROV explorations to new areas of Saba Bank are likely to reveal still greater diversity in mid-depth habitat types.
Abstract
Most gorgonian octocoral species are described using diagnostic characteristics of their sclerites (microscopic skeletal components). Species in the genus Pterogorgia, however, are separated primarily by differences in their calyx and branch morphology. Specimens of a morphologically unusual Pterogorgia collected from Saba Bank in the NE Caribbean Sea were found with calyx morphology similar to P. citrina and branch morphology similar to P. guadalupensis. In order to test morphological species boundaries, and the validity of calyx and branch morphology as systematic characters, a phylogenetic analysis was undertaken utilizing partial gene fragments of three mitochondrial (mtMutS, cytochrome b, and igr4; 726bp total) and two nuclear (ITS2, 166bp; and SRP54 intron, 143bp) loci. The datasets
for nuclear and mitochondrial loci contained few phylogenetically informative sites, and
tree topologies did not resolve any of the morphological species as monophyletic groups. Instead, the mitochondrial loci and SRP54 each recovered two clades but were slightly incongruent, with a few individuals of P. guadalupensis represented in both clades with SRP54. A concatenated dataset of these loci grouped all P. anceps and P. guadalupensis in a clade, and P. citrina and the Pterogorgia sp. from Saba Bank in a sister clade, but with minimal variation/resolution within each clade. However, in common with other octocoral taxa, the limited genetic variation may not have been able to resolve whether branch varia- tion represents intraspecific variation or separate species. Therefore, these results suggest that there are at least two phylogenetic lineages of Pterogorgia at the species level, and
the atypical Pterogorgia sp. may represent an unusual morphotype of P. citrina, possibly endemic to Saba Bank. Branch morphology does not appear to be a reliable morphological character to differentiate Pterogorgia species (e.g., branches “flat” or “3–4 edges” in P. gua- dalupensis and P. anceps, respectively), and a re-evaluation of species-level characters (e.g., sclerites) is needed.
Although little fisheries data exist for red hind, Epinephelus guttatus (Linnaeus, 1758) on the Saba Bank, Netherlands Antilles, spawning aggregation characteristics from other populations can be used to assess the health of a red hind spawning population previously undocumented there. In December 2005, a spawning aggregation site for red hind was surveyed on Saba Bank at 17°33.6´N, 63°17.7´W. Red hind aggregated on the northeast edge of the bank, in an area of 0.053 km2 . Spawning occurred in January 2006 during the week prior to and possibly after the full moon. Reproductively developed males and females were collected from December through February, however, in January average fish density increased from 1.46 ± 0.26 fish 100 m–2 to 34.27 ± 2.20 fish 100 m–2 and the M:F sex ratio shifted from 4:1 to unity. Fish were observed exhibiting little territorial or haremic behavior. Gonadosomatic indices in females reached high daily averages in January and February of 15.86 ± 5.4 and 6.93 ± 2.40 respectively, one day prior to the full moon. Average daily water temperature dropped throughout the study period, and during the week prior to the full moon in January, ranged from 26.7 °C to 26.5 °C. Current direction was dominated by tidal fluctuations but during the spawning period was predominantly directed to the southwest. Comparison of spawning population characteristics across red hind aggregation sites in the eastern Caribbean under varying degrees of protection suggests that the Saba Bank aggregation is moderately exploited and should be monitored and more closely managed.
Many environmental variables may influence fish assemblage structures in terms of abundance, biomass and mean size. The aim of this study is to provide a baseline survey on reef fish assemblages and shark presence covering the whole Saba bank (Dutch Caribbean). Hereby determining the influence of habitat, depth and fishing pressure on the structure of reef fish assemblages and shark presence. Baited Remote Underwater Video (BRUV) survey was used to describe reef fish assemblage structures on the Saba bank. Between 2012-2014, a total of 165 60 min BRUV deployments were conducted on locations varying in habitat complexity (0-4, Polunin and Roberts, 1993), depth (15-40m) and fisheries. The eleven most abundant fish species observed on the Saba bank represented eight families and accounted for nearly 50% of the total number of individual fish observed. Labridae was the most abundant fish family observed with a relative abundance of 22%. Most abundant fish species by number of individuals were Thalassoma bifasciatum (N=849 (9.8%)) Stegastus partitus (N=725 (8.4%)) and Acanthurus bahianus (N=430 (5.0%)).
Habitat complexity was positively correlated with species richness (Nsp), fish abundance (MaxN), and mean biomass, and negatively correlated with mean fish length. Strongly developed vertical relief habitats were found to support high numbers of fish species (N=19.1±0.6SE) of relatively low mean lengths (22.4cm±0.3SE), whereas less complex habitats were characterized by low numbers of species (N=8.3±0.8SE) with relatively high mean lengths (24.6cm ±0.81SE). Depth was negatively correlated with Nsp, MaxN and mean biomass and positively correlated with mean fish length. These relationships were all according to expectations based on earlier studies.
A minor part of the variability in the structure of reef fish assemblages was explained by differences in fisheries activity, indicating that no clear fisheries effect was observed in fish assemblages in this study. Furthermore, no significant differences in average size of target species were observed between areas with different fishing pressure. However, the general absence of piscivores such as large snappers and groupers was an indication of the indelible effects of past fisheries on the Saba bank.
A total of 85 shark observations were made with Ginglymostoma cirratum as most abundant species (N=41), followed by Carcharhinus perezii (N=36), Galeocerdo cuvier (N=5) and Carcharhinus limbatus (N=3). Relatively high shark abundances (0.20 sharks hour-1) were observed on the Saba bank compared with other Caribbean regions (The Bahamas: 0.14 sharks hour-1, Belize, 0.17 sharks hour-1). Shark abundance (CPUE) was positively correlated with habitat complexity, whereas depth exerted a negative influence on shark abundances. High shark numbers are a good sign for the health of the Saba Bank ecosystem, since sharks are apex predators, making them a prime indicator for ecosystem health.
Besides ‘traditional’ measures, ecomorphology was presented as an alternative measure in explaining variation in reef fish assemblages. For ecomorphological analysis insight in trophic morphology was obtained by using a Fish Food Model (FFM). The FFM in this study quantitatively related properties of 14 marine food types to morphological characterics of 15 common fish species on the Saba bank and predicted the capacity of utilizing these food types for each species. Strong differences in morphology and little overlap was observed for all different fish species in the FFM-analysis, which was mainly explained by two sets of variables involving predatory and herbivorous lifestyle. By multiplying each species’ capacity of using food types with its abundance an ecomorphological profile of each fish assemblage was calculated. On a functional level reef fish assemblages showed less variability than on species composition level, this possibly is an indication for high levels of robustness in niche differentiation in reef fish communities on the Saba bank.
Contour map of the Saba bank (GIS)
The Saba Bank is the largest submerged carbonate platform of 2,200 km2 in the Caribbean Sea, which lies partially within the Exclusive Economic Zone of the Netherlands and partially within the territorial waters of Saba and St. Eustatius. The Saba Bank houses an expansive coral reef ecosystem with a rich diversity of species and as such is also an important source of commercial fish for the nearby islands.
The Saba Bank furthermore forms the largest protected area of the Kingdom of the Netherlands, after the Dutch part of the Wadden Sea in Europe. It was declared a protected area by the Dutch Government in 2010 and has been registered as such in the Specially Protected Areas and Wildlife (SPAW) protocol of the Cartagena Convention for the Protection and Development of the Marine Environment of the Wider Caribbean. In 2012 it was internationally declared a Particularly Sensitive Sea Area (PSSA) by the International Maritime Organization (IMO) and an Ecological or Biological Significant Area (EBSA) by the Convention on Biological Diversity (CBD). As there are no large land masses nearby, the Saba Bank can be considered as relatively pristine and remote from human influences. Anthropogenic threats such as fisheries and environmental threats such as climate change, sea surface temperature increase and acidification, however, also threaten the Bank’s coral reefs.
As part of the Saba Bank research program 2011-2016, commissioned by the Dutch Ministry of Economic Affairs (EZ), expeditions to the Saba Bank were conducted in October 2011 and from 19 to 26 October 2013. The Saba Bank research program aims to obtain information on the biodiversity, ecological functioning and carrying capacity for commercial fisheries to facilitate sustainable management of the area. The expedition was funded by the Dutch Ministry of Economic Affairs and the World Wildlife Fund in the Netherlands.
The primary objectives of the 2011 and 2013 research expeditions were to collect data on benthic and reef fish communities, and on sponges and nutritional sources of the sponge community. Studies added to the 2013 expedition were research into the structural complexity of the reef; coral-algal interactions; and connectivity between populations. An international, multidisciplinary team of marine biologists investigated the coral reef structure as well as the spatial variation in species assemblages and population genetic connectivity of corals, algae, fish and sponges during eleven SCUBA dives at 20-30m depth.
During the expedition thirty-three 50m long transects resulted in more than 2000 images of the reef, and over 5000 fish counts of almost 100 fish species. A preliminary comparison with the data from 2011 gives the impression of a reduction in snappers, groupers and grunts, while there were noticeably more sharks. There were fewer algae on the Saba Bank than in 2011, possibly indicating a healthier reef, although there appeared to be a gradient of increasing algal cover towards the island of Saba. It seems unlikely that this is related to anthropogenic activities on the island, but more likely to natural causes.
An overview of collected data and preliminary results is given in this progress report. Further comparative analysis between the data collected in the 2011 and 2013 and further analysis between research components, e.g. between algal biomass, herbivorous fish biomass and nutrient levels, will be performed in 2014. This may give more information on the potential causes of the observed south-north algal gradient.
The expedition elicited large public interest and media coverage in both Dutch and Caribbean media (details provided in Appendix F). The work of the researchers, both above and under water, was also recorded on film as part of the documentary series Marine Life for Discovery Channel.
Findings
A management plan was prepared in close consultation with a considerable number of stakeholders and stakeholder group representatives.
The plan specifies management goals and strategies for the Saba Bank Management Organization (SBMO) related to the organization mission. It also identifies the major existing and potential threats and issues facing the Bank from ecological, social and cultural perspectives and includes substantial input from stakeholders. It is designed to be an adaptive management tool.
Below is a very brief overview of the management plan
Part I: Saba Bank Background Information
PART II: Management Environment
Summary of Issues (see below)
Management Recommendations (PART III: Management Environment)
Key issue: Create a clearly defined conch reserve on the Saba Bank.
Actions: Create and implement the queen conch reserve with no commercial take of conch. Research into queen conch stocks.
Key issue: Monitor the landings of commercial fish catches (there is currently very little data available on the yearly landings from the commercial fishermen of Saba).
Actions: Collect records of fishing activity on the Saba Bank. Develop a system to report landing from commercial fishermen. This dataset will lay the foundation for establishing a long-term commercial fisherman reporting system, which in turn will enable the SBMO to assess the state of the Saba Bank’s fish stocks.
Key issue: Enforcement of fisheries regulations (there is currently minimal enforcement of the fisheries regulations)
Actions: Collaboration; work with the Government, Harbour Office and Police to establish clear enforcement procedures and publicize the outcome. Encourage local fishermen to work with the police in the enforcement of the regulations. The SCF is in the process of having one of their rangers trained as a special agent.
Key issue: Monitor red hind spawning aggregation; assist in the development of a spawning aggregation closed season.
Actions: Gather initial information: determine where the majority of the fishermen are from and gauge trends in fish densities during the aggregations. Consult with stakeholders, including both the public and fishermen. Provide assistance in draft legislation for closing the spawning aggregation.
Key issue: Monitor tanker anchorage damage on the Saba Bank.
Actions: Monitor the impacts of anchoring. Prevent anchorage within the 12 miles of territorial waters. Provide whatever support is required for the Central Governments proposal to have the Bank recognized as a Particularly Sensitive Sea Area (PSSA).
Key issue: Evaluate the potential for artificial reef development on the Saba Bank.
Actions: Create and monitor an experimental artificial reef.
Key issue: Monitor and evaluate coral health.
Actions: Continue to monitor bleaching. Continue to monitor the state of the coral at existing sites established in 2007 on a regular basis. Adapt methods where appropriate. Co-ordinate with other islands. Communicate methods and results with St. Eustatius, St Maarten, and other DCNA islands, as well as the regional Global Coral Reef Monitoring Networkm (GCRMN) nodes.
Key issue: Facilitate and promote research from visiting scientists
Actions: Promote scientific research on the Bank (conferences, local, national media, and presentations). Provide assistance to researchers (providing logistic support and access to equipment)
Key issue: Work with the commercial fishermen in the management of the fisheries resource.
Actions: Promote the creation of a fisheries association among the fishermen as key stakeholders.
Key issue: Establish sustainable financing mechanisms
Actions: Raise money from fishing permits. Seek structural funding from the Dutch government under the new constitutional relationships.
