Veracruz Reef System, Gulf
of Mexico
Guillermo Horta-Puga and Guadalupe Barba-Santos
The Veracruz Reef System (VRS) situated in front off the Port of Veracruz
in the Gulf of Mexico was sampled in July 1999. Although the system is composed
of 22 well developed reefs, only three reefs were studied applying the AGRRA
protocols for corals and algae. The reefs chosen are part of the North Group:
Galleguilla, Isla de Sacrificios and Isla Verde. The Galleguilla (G)
reef was chosen because is a highly threatened reef, located off the outlet of
the sewage water treatment plant of the City of Veracruz. The moderately
threatened Isla de Sacrificios (IS), also was chosen because it was highly
impacted by tourism activities up to 1982, when it was closed and protected
from any human activity by the Mexican local authorities. Isla Verde (IV)
was chosen because it is representative of a low to moderately threatened reef.
Two sampling stations were selected in the zone of maximum reef development,
the fore-reef zone (windward or East slope) at two depths: 3-6 m the Acropora
biotope, and 9-12 m in the area of highest coverage. A total of 723 live stony
coral colonies, 138 transects and 662 algal quadrats were sampled.
Fifteen coral taxa were recorded Acropora cervicornis, A. palmata, Agaricia
agaricites, Colpophyllia natans, Diploria spp., Montastraea annularis, M. cavernosa, M.
faveolata, M. franksii, Madracis decactis, Millepora alcicornis, Oculina
diffusa, Porites spp., Siderastrea spp. and Stephanocoenia intersepta.
The number of coral taxa recorded per reef is: 7 (G), 14 (IS) and 11 (IV) and,
by depth, 14 at 3 m and 13 at 9 m. Some other species were seen in the transects,
but as they measured <25 cm, were not recorded.
The bottom area covered by living coral (>25 cm in diameter) in the VRS was 15.1%, with a total coral density of 0.5 ind/m. The remaining area was mainly long dead and highly eroded coral skeletons with a layer of terrigenous sediment. Coral coverage and density were 16.5% and 0.5 ind/m at 3 m and 15.8% and 0.5 ind/m at 9 m, respectively. Coral coverage showed some degree of variation among reefs: 11.9% (G), 17.5% (IS) and 16.2% (IV). However, density by reef was almost the same: being 0.5 ind/m (G), 0.6 ind/m (IS) and 0.5 ind/m (IV).
In the VRS coral coverage (area covered by a single taxon of coral)
overall was dominated by M. cavernosa (6.0%), followed by C. natans
(4.7%), Diploria
spp. (1.9%) and Siderastrea spp. (1.2%). At the windward slope the dominance
by depth was M. cavernosa (6.9%), C. natans (4.9%), Diploria spp. (2.3%) and Siderastrea
spp. (1.4%) at 3 m, and M. cavernosa (5.0%), C. natans (4.8%) and Siderastrea
spp. (3.3%) at 9 m. The hierarchy of cover dominance by
reef was
M. cavernosa (7.6%), C. natans (2.4%) and Siderastrea spp. (1.2%) at
G, M.
cavernosa (9.6%), C. natans (2.1%), Siderastrea spp. (1.9%) and Diploria
spp. (1.8%) at IS, and C. natans (9.1%), Diploria spp. (3.3%) and M. cavernosa
(1.4%) at IV.
In terms of relative numerical abundance, M. cavernosa (35%, 253
colonies) was the dominant taxon in the VRS, followed by C. natans (26.7%, 193 col.),
Siderastrea
spp. (17.0%, 123 col.) and Diploria spp. (12.3%, 89 col.). At 3 m,
the dominant species was M. cavernosa (40%) followed by C. natans
(25.5%) and Diploria
spp. (16%). At 9 m, M. cavernosa (29.5%) was dominant followed
by C.
natans (27.5%) and Siderastrea spp. (25.5%). Dominance among
reefs was strikingly different: The hierarchy was M. cavernosa (63%) C. natans
(21.5%) and Siderastrea
spp. (10.5%) for G, M. cavernosa (52%), Diploria spp. (14%), C. natans
(11%) and Siderastrea
spp. (11%) for IS and C. natans (55%), Diploria spp. (20.5%) and M. cavernosa
(8%) for IV, respectively.
The incidence of partial mortality for the VRS´s hard macrocorals is
high. Of all surveyed colonies 45.3% have lost part of their surface living
tissue, mainly due to algal overgrowth. Corals with partial mortality, on the
average, lost 21.1% of their tissues. The dead areas of the coral were covered
by algae (90.0%), sponges (3.0%), fish bites (3.0%) or appeared bleached
(3.9%). ). Old death was present in 91.2% of the colonies, and only 8.8% were
recently dead. Only two colonies of the total sampled community presented both
old and recent death areas. The percent of colonies affected by partial
mortality, and the average tissue loss, both old and recent death, was 41.8%
and 18.9% for G, 46.9% and 22.4% for IS, and 47.9% and 21.4% for IV,
respectively. The same data by depth was 46.9% and 21.4% at 3m and 44.0% and
20.5% at 9 m. Bleached or partially bleached colonies accounted for 2.8% of the
total sampled coral community. No other coral disease was observed.
Coral recruitment, quantified as ind/m² (ind = colonies <2cm in size) from the algal quadrats was low for the VRS 1.7 ind/m². Recruitment by depth was 1.0 ind/m² and 2.6 ind/m² for the 3 m and 9 m depths respectively. Recruitment by reef was 3.1 ind/m² (G), 0.7 ind/m² (IS), and 1.3 ind/m² (IV).
In the VRS crustose coralline algae (46.9%), followed by turf algae (30.4%), dominated the substrate available for coral settlement and development. Macroalgae are notably scanty in the fore-reef zones of the VRS (0.5%), and sediment (terrigenous + endogenous) accounts for up to 22.2% of the quadrats. The proportions quantified by depth are for the 3 m and 9 m sites, respectively: crustose coralline algae 46.3% and 47.7%, turf algae 27.6% and 34.3%, macroalgae 0.3% and 0.9% and sediment 25.8% and 17.1%.
Although present in the VRS, only two specimens of Diadema antillarum were
counted on all transects. So, we decided to count the number of individuals of
the most important sea urchin in the area Echinometra spp. (E. lucunter + E. viridis).
The density of Echinometra in the VRS was 0.6/m². Density by reef was 0.34%
(G), 1.25% (IS), and 0.45% (IV). Density of Echinometra by depth was 0.75% at
3m, and 0.37% at 9m.
The AGRRA surveys were performed during the local rainy season. As the
VRS is influenced by the discharge of the Antigua, Jamapa and Papaloapan
Rivers, water turbidity was high.. Visibility at any depth was usually < 5
m, and often <2 m.
The survey staff: Gilberto Acosta, Guadalupe Barba-Santos, Xóchitl
González, Kublai Horta, Guillermo Horta-Puga, Eduardo Palacios, and Edgar
Tovar.
For more information please contact:
INVEMAR, Lab. Biogeoquímica, UBIPRO, ENEP-Iztacala
UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO
Av. de los Barrios S/N, Los Reyes Iztacala
Tlalnepantla, Edo. de México 54090, MEXICO
Tel: (+52) 56231126, 56231132
Fax: (+52) 56231225
E-mail: horta@servidor.unam.mx