Deep hermatypic reefs have also been discovered at the southwest coast of Isla Desecheo.
These include the SW Wall Reef, at depths between 30-40 m, and Agelas Reef, at depths
between 45 – 70 m. Substrate cover at the SW Wall Reef was dominated by benthic
macroalgae (mostly Lobophora variegata), sand, sponges, and massive corals. Sponges
were highly prominent (mean surface cover: 17.3 %), growing mostly as large erect and
branching forms that produced substantial topographic relief and protective habitat for fishes
and invertebrates. In many instances, sponges were observed growing attached to stony
corals, forming sponge-coral bioherms of considerable size. One of the most common
associations involved the brown tube (Agelas conifera, A. sceptrum) and row pore sponges
(Aplysina spp.) with star corals (Montastrea cavernosa, M. annularis). A total of 25
scleractinian corals, three hydrocorals and two antipatharian (black coral) species were
present along the SW Wall Reef. Great star corals (Montastrea cavernosa, M. annularis
complex) were the dominant species of scleractinian corals at the SW Wall Reef.
Agelas Reef (45 – 70 m) appears to be a crustose algal formation colonized by encrusting
brown algae (Lobophora variegata), large erect and branching sponges (Agelas conifera,
Agelas spp., Aplysina spp.) and lettuce corals (Agaricia spp). Sessile-benthic biota grows
over a vast deposit of rhodolite nodules loosely anchored to the bottom. The reef has very
low topographic relief as it lies over an essentially flat platform and massive corals do not
contribute significantly to its rugosity. A total of 18 species of scleractinian corals, two
hydrozoans (Millepora alcicornis and Stylaster roseus) and the antipatharian black wire coral
(Stichopathes lutkeni) were identified from Agelas Reef. The combined mean substrate
cover by the nine species of scleractinian corals within video-transects was 13.1 % (range:
7.4 – 36.4). Irregular sheets or laminar growth by lettuce corals (Agaricia spp.) prevailed at
depths between 45 and 53 meters (148 – 175’), with a combined substrate cover of 8.9 %,
representing 70 % of the total cover by scleractinian corals. Lamark’s sheet coral (Agaricia
lamarki) appeared to be the main species present.
A total of 70 fish species were identified from depths below 30 m at Isla Desecheo. The
numerically dominant ichthyofauna within belt-transects surveyed was dominated by
zooplanktivorous taxa, suggesting that planktonic food webs are most relevant on deep
reefs Deep reefs studied at Isla Desecheo are the natural habitats of many exploited
commercially important food fishes, such as large groupers (Nassau, Yellowfin, Red Hind)
and snappers (Cubera) and target species of the aquarium trade (Blue Chromis, Royal
Gramma, Pigmy Angelfishes, Butterflyfishes, Jawfishes). Densities of adult red hind
(Epinephelus guttatus) from 40 m at the SW Wall are the highest recorded for Puerto Rico.
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These include the SW Wall Reef, at depths between 30-40 m, and Agelas Reef, at depths
between 45 – 70 m. Substrate cover at the SW Wall Reef was dominated by benthic
macroalgae (mostly Lobophora variegata), sand, sponges, and massive corals. Sponges
were highly prominent (mean surface cover: 17.3 %), growing mostly as large erect and
branching forms that produced substantial topographic relief and protective habitat for fishes
and invertebrates. In many instances, sponges were observed growing attached to stony
corals, forming sponge-coral bioherms of considerable size. One of the most common
associations involved the brown tube (Agelas conifera, A. sceptrum) and row pore sponges
(Aplysina spp.) with star corals (Montastrea cavernosa, M. annularis). A total of 25
scleractinian corals, three hydrocorals and two antipatharian (black coral) species were
present along the SW Wall Reef. Great star corals (Montastrea cavernosa, M. annularis
complex) were the dominant species of scleractinian corals at the SW Wall Reef.
Agelas Reef (45 – 70 m) appears to be a crustose algal formation colonized by encrusting
brown algae (Lobophora variegata), large erect and branching sponges (Agelas conifera,
Agelas spp., Aplysina spp.) and lettuce corals (Agaricia spp). Sessile-benthic biota grows
over a vast deposit of rhodolite nodules loosely anchored to the bottom. The reef has very
low topographic relief as it lies over an essentially flat platform and massive corals do not
contribute significantly to its rugosity. A total of 18 species of scleractinian corals, two
hydrozoans (Millepora alcicornis and Stylaster roseus) and the antipatharian black wire coral
(Stichopathes lutkeni) were identified from Agelas Reef. The combined mean substrate
cover by the nine species of scleractinian corals within video-transects was 13.1 % (range:
7.4 – 36.4). Irregular sheets or laminar growth by lettuce corals (Agaricia spp.) prevailed at
depths between 45 and 53 meters (148 – 175’), with a combined substrate cover of 8.9 %,
representing 70 % of the total cover by scleractinian corals. Lamark’s sheet coral (Agaricia
lamarki) appeared to be the main species present.
A total of 70 fish species were identified from depths below 30 m at Isla Desecheo. The
numerically dominant ichthyofauna within belt-transects surveyed was dominated by
zooplanktivorous taxa, suggesting that planktonic food webs are most relevant on deep
reefs Deep reefs studied at Isla Desecheo are the natural habitats of many exploited
commercially important food fishes, such as large groupers (Nassau, Yellowfin, Red Hind)
and snappers (Cubera) and target species of the aquarium trade (Blue Chromis, Royal
Gramma, Pigmy Angelfishes, Butterflyfishes, Jawfishes). Densities of adult red hind
(Epinephelus guttatus) from 40 m at the SW Wall are the highest recorded for Puerto Rico.
3