Figure 1.
A map of Saba Bank, in the Netherlands Antilles.
Saba Bank is shown relative to its nearest neighbor, Saba. A pale band of color representing 11–20 m depths represents a “fore-reef” extending 50 km along the southeast perimeter of the Bank. Red stars indicate the location of 8 quantitative transects, four on the fore-reef (A sites and CV sites) and four in the plateau (E3, E4, D9, Void) of Saba Bank's interior region. The dashed lines indicate Overall Bank, where a zonation scheme with random sites was in effect. Void was random, Conch Valley was non-random.
Figure 2.
Depth profiles of the Saba Bank platform edge.
Profiles of platform edge “fore-reef” dive sites on Overall Bank (A7, A12 in Figure 1) and in the Conch Valley (CV1, CV2 in Figure 1). Each fore-reef is bounded on the interior by a trough of varying depth and character. Troughs were generally sandy, with intermittent patch reefs.
Table 1.
List of octocoral species collected from Saba Bank.
Figure 3.
Ordination plot of Caribbean octocoral localities.
A non-metric multidimensional scaling (MDS) plot based on Bray-Curtis dissimilarity measures derived from presence and absence of octocoral species in surveys of Florida [9], Colombia [10], and Puerto Rico [11].
Figure 4.
Species accumulation curve for Saba Bank gorgonians.
The graph shows a sample-based rarefaction curve (in black) based on 17 shallow and deep dives. The technique employs a Mao Tau estimator [21] of expected species richness with 95% confidence intervals (in light blue). The species accumulation curve is steeply inclined, not approaching asymptote. More gorgonian species remain to be discovered on Saba Bank, though richness is already higher than other study sites in the West Atlantic.
Table 2.
Summary table of gorgonian density and diversity.
Figure 5.
High-diversity gorgonian assemblage on the Saba Bank fore-reef.
An image from one of the “A” sites on the fore-reef of Saba Bank (∼25 m) shows an assemblage characterized by sea fans (Gorgonia ventalina), sea plumes (Pseudopterogorgia americana), and the Eunicea/Plexaura sp. complex, Eunicea fleuxosa, center. The fore-reef environment consists of a series of reef crests near the platform edge on Saba Bank [4] with diverse and abundant octocoral species.
Figure 6.
Low-diversity gorgonian assemblage on the Saba Bank plateau.
An image from one of the “E” sites in the Saba Bank plateau region shows a large sea plume (∼1.5 m- Pseudopterogorgia acerosa) and scattered sea fans Gorgonia mariae attached to a hard carbonate platform covered with a thin veneer of sediment. The plateau region is distinct from the fore-reef, consisting of reef flat and lagoon bottom environments [4].
Figure 7.
Ordination plot of Saba Bank transects.
A non-metric multidimensional scaling (MDS) plot based on Bray-Curtis dissimilarity measures derived from species abundance values in 8 quantitative transects. Fore-reef sites (A, CV) are significantly different (ANOSIM, P<0.05) from plateau sites (D, E, and Void), but not significantly different from each other. There is good separation between fore-reef and plateau sites, with slight prospect of a misleading representation (2D stress <0.10).