| Report
on four dives on the Saba Bank, 17 and 18 July 1999
Paul Hoetjes, Mark Vermeij and Andy Caballero Introduction
Description of the dive sites
On July 17 the second dive (exact position unknown, but on the northern edge of the Bank immediately facing Saba) was performed on a sloping part of the Bank near the North edge, starting at a depth of 60 ft till a depth of about 90 ft. The bottom consisted mostly of sand here, but outcroppings of (dead) coral were seen more than during dives 1 and 4 on the plateau of the Bank. A few Conch were seen, and another stingray. Fig. 3. View of the reef at 80 ft. Groove and spur-like
During the first dive on July 18 at a depth of 80 ft the highest abundance of corals was encountered. The reef consisted of large stretches of coral rising up to 8 ft from sand valleys and sand patches that alternated with the reef, in a kind of spur and groove formation (fig. 3). A total of 32 coral species were observed (table 1). Many of the coral colonies were large (especially the Montastrea species), but many others were much smaller compared to colonies growing on undisturbed reefs in the same region. In between the corals an unusually dense layer of macro algae was present, composed mainly of Dictyota divaricata, 5-10 cm high (fig. 4), but areas covered with Lobophora variegata were also common. Compared to St. Maarten or Curaçao this reef was situated much deeper than similar reefs found around the other islands. The amount of macro algae present was striking and would seem to indicate some source of nutrients, perhaps caused by upwelling along the edge of the Bank. Many corals suffered from partial mortality, apparently recent (within the past 3-5 years). Yellow Blotch/Band (fig. 5)and Dark-Spot disease were seen regularly, but were not rampant. Partial bleaching was observed in a colony of Dendrogyra cylindrica (fig. 6). From this very limited impression, the health of this reef seemed in worse state than similar reefs around St. Maarten and Curaçao. For a pristine reef free of human impact this seems cause for concern. More research is needed to provide data on the state of the coral health. Fig 4. Lush growth of Dictyota divaricata
on
dead coral patches  Adjacent
to the coral reef area a larger stretch of flat sandy bottom was encountered,
in many places with a thin patchy cover of a blue-green algae (Schizotrix
calcicola?). Some patches of coral were scattered on this sand bottom
. No live Conch (some small dead ones were present) were observed here.
Fishes observed in this coral reef area included numerous Queen Triggerfish (> 10 individuals), and Red Hinds. Two individuals of the Yellowfin Grouper (Mycteroperca venenosa) were observed, (± 40 cm and 90 cm). Whitespotted Filefish (Cantherhines macroceros) (2 individuals) and Gray Angelfish (Pomacanthus arcuatus) (2 individuals) were also seen. Despite this, fishes seemed to be rather scarce. Fishes such as Yellowtail Snappers and Tangs, common elsewhere, were notably absent here.
Table 1. The following coral species (32) were found during dive
3:.
Table 2. Locations, depth and bottomtype of the dives made
|
On
July 17 and 18, 1999, four dives were made on the Saba Bank, a 1600
km2 (depth<50 m) sunken atoll, approximately 4 miles offshore
from the island of Saba (Netherlands Antilles). All dives took place
in the Upper North East corner of the Bank. Because of damage to the
handheld GPS, the positions of the first two dives on July 17 could
not be recorded, although a rough estimation of the position of the
first dive could be made (see fig. 1 and table 2). The purpose of the
dives was to investigate the local environment values of the Saba Bank,
an area that is a very important fishing ground for local fishermen,
especially for lobster (Panulirus argus). Where the dives took
place in a coral reef area they also presented an opportunity to get
an impression of the health and the state of the coral reef of the Bank.
During
the first dive a flat, solid limestone rock bottom was encountered at
a depth of 60 ft, covered with sparse coral rubble and thin patches
of sand. A dense monospecific cover of the brown algae Dictyopteris
justii was present here (bottom coverage > 80%), interspersed occasionally
with a strikingly green specimen of the green alga Codium isthmocladum.
Coral
Reef
