Brooks, B.L.

Two rarely reported and one newly described species of benthic marine algae are herein recognized from deep-water habitats at Bonaire, representing the first Caribbean reports of each. Archestenogramma profundum is previously known only from its type collection in Bermuda at 17 m depth and the rarely reported Halymenia integra is known originally from its type locality at Cabo Frio, Brazil. Verdigellas discoidea is newly described on the basis of morphological and molecular evidence. It forms flat circular thalli to 6.5 cm in diameter, measuring to 390 μm thick. The disc-like algae are attached by several small holdfasts on the ventral surface, but the margins are mostly free from their substrata.

Keywords: Archestenogramma; Caribbean; Halymenia; macroalgae; Verdigellas

Two rarely reported and one newly described species of benthic marine algae are herein recognized from deep-water habitats at Bonaire, representing the first Caribbean reports of each. Archestenogramma profundum is previously known only from its type collection in Bermuda at 17 m depth and the rarely reported Halymenia integra is known originally from its type locality at Cabo Frio, Brazil. Verdigellas discoidea is newly described on the basis of morphological and molecular evidence. It forms flat circular thalli to 6.5 cm in diameter, measuring to 390 μm thick. The disc-like algae are attached by several small holdfasts on the ventral surface, but the margins are mostly free from their substrata.

Keywords: Archestenogramma; Caribbean; Halymenia; macroalgae; Verdigellas.

Background:

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.

Methodology/Principal Findings:

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.

Conclusions/Significance:

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.