gorgonian

Multivariate Analysis of Gorgonian Habitats on Saba Bank, Netherlands Antilles

The second Saba Bank Expedition in October 2008 aimed at improving the knowledge of the gorgonacea by generating a comprehensive species list for shallow and deep water species with georeferenced in-situ photographs and voucher specimens for each sample taken.
Gorgonian species were common and conspicuous at all sites surveyed, except perhaps in some deep water (~60m) rubble flats south of Poison Bank. A total of 47 species were collected, including two new species in the genera Pterogorgia and Lytreia. Pterogorgia n. sp. was collected twice from 20m depth in the D zone. Lytreia n. sp. was collected twice from 50m depth near the A zone. The total number of gorgonian species collected from shallow water was 39. The number of gorgonian species from deep water (>50m) was 12. There was some overlap in the zones, with 4 shallow water species (Muriceopsis flavida, Eunicea clavigera, Pseudopterogorgia acerosa, and Ps. bipinnata) occurring below 50m. The species accumulation curve for shallow water species indicates the slope of the fitted line decreases with effort, but the line shows no clear asymptote. The species accumulation curve for deep water collections is still climbing. The line could be interpreted as a linear rise in deep-water species richness. There is no indication we have collected all the gorgonian species from the Saba Bank

The survey results add 38 species to the list of gorgonacea known to occur on Saba bank. The discovery of a new species of Pterogorgia was surprising because a) the discovery was made in shallow, easily accessible water depths and b) the new species was collected from the relatively depauperate reef flats in the “D zone”. This suggests the reef flat area in the interior of the Bank may be largely unexplored and the true diversity of the reef flat areas may be somewhat underappreciated.

Date
2008
Data type
Research report
Theme
Research and monitoring
Report number
Saba Bank Project 2007, Report 4
Geographic location
Saba bank
Author

Saba Bank Research Expedition 2013 - Progress Report

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.

Date
2014
Data type
Research report
Theme
Research and monitoring
Report number
C086/14
Geographic location
Saba bank