Gulf of Venezuela

Richness and distribution of stony corals in the north-western coast of the Gulf of Venezuela

Coral reef ecosystems are considered by several authors as key areas which hold a vast diversity of marine species. Comprehensive studies have been developed in Venezuela describing these ecosystems both taxonomically and ecologically. Nevertheless, there has been a lack of information from the Gulf of Venezuela. Systematic information was gathered through direct observations (apnea diving), submarine transects, underwater photography and videos, which confirmed the presence of coral patches, as well as their geographical, bathymetrical and environmental characteristics – salinity, temperature and turbidity  in the Gulf of Venezuela. Fifteen species of stony coral were identified; 12 scleractinian and three milleporina. The effect of freshwater and significant sedimentation may be the reasons of a low richness in comparison with other areas in the southern Caribbean. These records increase the species and habitats diversity for the Gulf of Venezuela.

Los ecosistemas arrecifales son considerados por diversos autores como refugio para una gran diversidad de especies marinas. En Venezuela han sido muchos los trabajos que describen taxonómica y ecológicamente a este ecosistema, pero existe una notable ausencia de información registrada para el Golfo de Venezuela. Se recabó información, a través de observación directa (buceo apnea), registros fílmicos y fotográficos, que corroboran la presencia de bancos arrecifales (ubicación geográfica, batimétrica y otras características físicas – salinidad, temperatura y turbidez) en la zona noroccidental del Golfo de Venezuela. Se registraron 15 especies de corales duros: 12 escleractinios y tres especies mileporinas. Su riqueza es sustancialmente menor, comparada con la reportada para otras comunidades coralinas del Caribe Sur, lo que podría estar relacionado a la influencia de la descarga de agua dulce y de la marcada sedimentación en diferentes zonas; ambos elementos podrían estar afectando la supervivencia de las comunidades coralinas en la zona de estudio. Con los registros se incrementa la diversidad de especies y de hábitats para el Golfo de Venezuela.

Molluscs are the invertebrates with the highest level of morphological
adaptation, allowing their establishment in the majority
of aquatic environments. In fact, the highest fitness level
is achieved by those species, such as bivalves, adapted to live
on cryptic ecosystems build by themselves. In order to describe
the diversity of cryptic bivalve molluscs in two sampling areas
in the western coast of the Gulf of Venezuela (Kazuzain and
Porshoure), samples were manually collected in June and July
2010, respectively, by snorkelling in random coralline rocks (3-
5m depth), and stored them in 10% formalin for transportation.
In the laboratory, the rocks were fragmented and all organisms
within removed. Diversity was determined by the Shannon-Wiener index for each locality, and the Kruskal-Wallis test
was used to compare the bivalves composition between both
localities in order to establish a possible significant difference
(p<0.05). Five families, eight genera and ten species were found
(n=53). Lithophaga corrugata, Lioberus castaneus, Gregariella
coralliophaga and Choristodon robustus are reported as new records for Venezuela; while Leiosolenus appendiculatus, Lithophaga teres and Malleus candeanus are new records for the Maracaibo Lake System. No significant difference was found between the studied communities (p=0.1587). The specimens remain in the invertebrates collection of the Biology Museum, La Universidad del Zulia (MBLUZ), Maracaibo, Venezuela.

The Guiana dolphin (Sotalia guianensis) is widely
distributed along the coasts of Central and South
America. Similar to other delphinids, this species
emits echolocation clicks, burst pulses, and whis-
tles. Although whistling seems to play a major role
in the social organisation of dolphins, there is a
lack of knowledge about Guiana dolphin whistles
outside of its populations in Brazil and Costa Rica.
In this study, we describe the acoustic structure of
Guiana dolphin whistles from the southern Gulf
of Venezuela for the first time. We recorded the
whistles using an omnidirectional hydrophone
(CR1). For each whistle, we measured maximum
frequency (kHz), minimum frequency (kHz), start-
ing frequency (kHz), ending frequency (kHz),
duration (s), and number of inflection points, us-
ing spectrograms created in SpectraLAB 4.32,
Version 17. Whistles presented an average starting
frequency of 10.58 kHz (SD = 2.49 kHz), a mean
ending frequency of 13.96 kHz (SD = 2.60 kHz),
an average minimum frequency of 10.31 kHz
(SD = 2.33 kHz), a mean maximum frequency of
13.96 kHz (SD = 2.51 kHz), an average duration
of 0.27 s (SD = 0.14 s), and a maximum of four
inflection points (mode 0). This research provides
new insights into the acoustic behaviour of the
Guiana dolphin in the Gulf of Venezuela.