**Biodiversity and Conservation of the Estuarine and Marine Ecosystems of the Venezuelan Orinoco Delta**

Patricia Miloslavich1, Alberto Martín1, Eduardo Klein1, Yusbelly Díaz1, Carlos A. Lasso2, Juan José Cárdenas3 and Oscar M. Lasso-Alcalá4 *1Universidad Simón Bolívar, Departamento de Estudios Ambientales, Caracas 2Instituto Alexander von Humboldt, Bogotá 3Fundatún, Caracas 4Fundación La Salle de Ciencias Naturales, Museo de Historia Natural La Salle, Caracas 1,3,4Venezuela 2Colombia* 

#### **1. Introduction**

66 Ecosystems Biodiversity

Zhang, T. & Li, Z. (2007). Fish resources and fishery utilization of Lake Poyang. Journal of

Zhang, X.; Cao, L.; Liu, J.; Bai, L. & Yu, C. (2008). Growth pattern of redfin culter,

Zhu, S. (1995). Synopsis of freshwater fishes of China. Jiangsu Science and Technology Press,

Zhuang, P.; Wang, Y.; Li, S.; Deng, S.; Li, C. & Ni, Y. (2006). Fishes of the Yangtze estuary.

Shanghai Science & Technology Press, Shanghai, China.

Ocean Press, Beijing, China.

Lake Sciences., 19: 434-444.

Nanjing. 549 pp.

University (Natural Science), 32: 70-74.

productivity and improvement of ecological environment in Lake Honghu. Honghu Research Group, Institute of Hydrobiology, CAS (Ed). 162-171, China

*Cultrichthys erythropterus* Basilewsky (1855) in Poyang Lake. Journal of Nanchang

#### **1.1 Oceanographic features and eco-regions of the Orinoco Delta**

The Orinoco is one of the largest rivers in South America (2,150 Km). Globally, it is the third in water flow (yearly average of 39,000m3/s), and the fifth in sediment transportation (150 million tons/year). The Orinoco basin extends for nearly a million square kilometers within Colombian and Venezuelan territories, and is characterized by at least ten large terrestrial and aquatic eco-regions including its opening into the Atlantic through the vast Orinoco Delta (located between 07° 46´ to 10° 00´ N, and 59° 50´ to 62° 35´ W) (Michelangeli, 2000; Bone et al., 2004; Lasso et al., 2010). These deltaic plains were formed by the combined action of sediment and freshwater discharges from the Orinoco, with the tides on a flat alluvial plain (Miloslavich et al., 2011) creating a dynamic ecosystem of fluvial and estuarine habitats. The boundaries between these two habitats are defined according to their altitude above sea level and tidal influence (Lasso & Sánchez-Duarte, 2011), with the fluvial delta corresponding to the mid and high delta according to Cervigón (1985). The lower limit of the fluvial delta varies due to seasonal annual fluctuations in freshwater discharge from the Orinoco, related to regional and, even local, precipitation regimes, and a salt wedge from the sea that moves inward with the incoming tide. In the estuarine delta, the ecological boundary of the fluvial delta is the limit at which the sea water influences the main stream and its channels, while the ecological boundary with the sea is a fringe, which is variable in size and forms after sand or mud bars at the opening of the seaward channels. Along this longitudinal zone from the upper to the lower delta, a geomorphological, physico-chemical, and therefore, biological gradient can be observed. In addition to this longitudinal gradient, a very important transversal gradient also exists, that creates particular lentic ecosystems with specialized biota. Within the Atlantic, the major areas of influence of the Orinoco are (1) the Gulf of Paria, a semi-enclosed area between the Araya Peninsula (Venezuela) and the

Biodiversity and Conservation of the Estuarine

fish reservoir of juvenile stages.

euryhaline.

in meters.

and Marine Ecosystems of the Venezuelan Orinoco Delta 69

Subregion 3: Pedernales. This is a shallow water zone with a depth of 0-15 m with important extensions covered by mangroves, and some beaches characterized by boulders. The region has a high abundance of commercial species of fish and crustaceans and it is an important

Subregion 4: Gulf of Paria. This zone between 15 m of depth and the limit of international waters serves as an important migratory route for sea mammals, turtles and birds, and as a feeding area for turtles. The area was under intense pressure from trawling fisheries for many years, which were stopped in 2009 with the passage of a new environmental law in Venezuela that mandated that intensive trawling activities cease. While trawling fisheries

Subregion 5: Boca de Serpiente. This zone with a depth between 0 and 60 m has a complex hydrodynamic system due to the acceleration of marine currents. It is an important migratory route for sea mammals, turtles and birds. Its marine and estuarine biodiversity is relatively high, with high abundance of phytoplankton and zooplankton, including fish larvae. The area contains wetlands with a high biodiversity of birds and a continuous, extensive, tall mangrove formation. Its beaches are formed by muddy sediments and its

Subregion 6: Boca Grande. At a depth between 0 and 60 m, this zone is under the direct influence of the discharge of many of the delta channels, including the largest or Rio Grande. The zone contains numerous islands of different sizes with fragmented mangrove formations. Erosion and sedimentation processes are very active, and the area is significantly influenced by freshwater input. Biodiversity associated with this area is mainly

Fig. 1. Map of the Orinoco Delta and Gulf of Paria region in the Venezuelan Atlantic front. Map shows the main ecosystems and human settlements. Bathymetry and elevation scales

still take place, they are conducted at the same intensity as artisanal fisheries.

benthic community shows marked seasonal variations.

west coast of Trinidad, connected to the Caribbean by Boca del Dragón, a ~8km strait, (2) the Orinoco Deltana Platform, the area within the Atlantic Ocean directly adjacent to the Orinoco deltaic plain, and (3) Boca de Serpiente, which connects the Deltana Platform with the Gulf of Paria. These combined areas cover 27,630 km2 and shelter one of the major and best-preserved wetlands in South America (Figure 1).

In general, the Orinoco Delta and the marine area under its influence has a mean annual temperature between 25 and 28 ºC (range: 15.7 to 37.2 ºC), with two warm peaks, one occurring in May and the other in September. There are two seasons, the dry season occurs between January and April, and the rainy season between June and November. May and December are transitions months between the seasons. The rainy season occurs when the Intertropical Convergence Zone (ITCZ) moves from the Equator towards the Caribbean producing a mean of 1,500 to 2,000 mm of rainfall per year. At this time, winds usually come from the east at an average speed of 3.2 m/s. When the ITCZ moves back to the Equator, the area is influenced by the trade winds that blow from the north-northeast at an average speed of 6.2 m/s (Bone et al., 2004; Martín & Bone, 2007). The area is also affected by the discharge of the Orinoco, which introduces significant changes in salinity, temperature, nutrients, and water quality at both spatial and temporal levels. The productivity of this area is significant and one of the highest in comparison to the eastern Caribbean region. Such high productivity is due to the seasonal upwelling off the northeast coast of Venezuela, and the seasonal dispersal of the Orinoco plume, which covers an area of more than 300,000 km2 in the adjacent Caribbean and provides for a significant increase in concentration of nutrients and photosynthetic pigments (Martín & Bone, 2007; Muller-Karger et al., 1989). The region is also influenced by the Guiana current, which flows parallel to the coastline towards the northwest (~106m3/s). The Guiana current originates from the Brazilian current and forms high-energy whirlpool structures that may surpass in intensity the normal circulation and consequently cause transitory episodes of current reversal. The Amazon river also affects this area during the first six months of the year, when its waters extend to the northwest, increasing turbidity in coastal waters, and creating a large plume and sections of brackish water offshore. Tides are very important at the local level particularly because of associated currents. Tides in this region are mostly semidiurnal, but in the Gulf of Paria, tides are mixed. Within the Gulf, the height of the tide is magnified within an increasing gradient from Boca del Dragón to the south, reaching up to 2 m (Martín & Bone, 2007).

Based on ecological and biological features, and aiming toward a better conservation strategy, the area was classified into seven subregions (Figure 1), defined according to the internal variability of their ecosystems, communities, and populations, including those of the terrestrial areas when these are included in the landscape (Klein & Cárdenas, 2009). The subregions, along with the main marine or estuarine features that characterize them, are:

Subregion 1: Paria Peninsula. This zone is characterized by a high landscape heterogeneity, with beaches, coves, a few rocky shores, and wetlands (Mata Redonda and Bajo Alcatraz).

Subregion 2: Sac of the Gulf of Paria. This is a shallow water zone with a depth of 0-15 m characterized by extensive and tall mangrove formations that comprise a heterogeneous wetland with interconnected small channels into which the salt water penetrates. In this region, two estuarine systems (Caño Ajíes and Caño San Juan) are important fish reservoirs, with high biomass of fish larvae of the families Sciaenidae and Lutjanidae.

west coast of Trinidad, connected to the Caribbean by Boca del Dragón, a ~8km strait, (2) the Orinoco Deltana Platform, the area within the Atlantic Ocean directly adjacent to the Orinoco deltaic plain, and (3) Boca de Serpiente, which connects the Deltana Platform with the Gulf of Paria. These combined areas cover 27,630 km2 and shelter one of the major and

In general, the Orinoco Delta and the marine area under its influence has a mean annual temperature between 25 and 28 ºC (range: 15.7 to 37.2 ºC), with two warm peaks, one occurring in May and the other in September. There are two seasons, the dry season occurs between January and April, and the rainy season between June and November. May and December are transitions months between the seasons. The rainy season occurs when the Intertropical Convergence Zone (ITCZ) moves from the Equator towards the Caribbean producing a mean of 1,500 to 2,000 mm of rainfall per year. At this time, winds usually come from the east at an average speed of 3.2 m/s. When the ITCZ moves back to the Equator, the area is influenced by the trade winds that blow from the north-northeast at an average speed of 6.2 m/s (Bone et al., 2004; Martín & Bone, 2007). The area is also affected by the discharge of the Orinoco, which introduces significant changes in salinity, temperature, nutrients, and water quality at both spatial and temporal levels. The productivity of this area is significant and one of the highest in comparison to the eastern Caribbean region. Such high productivity is due to the seasonal upwelling off the northeast coast of Venezuela, and the seasonal dispersal of the Orinoco plume, which covers an area of more than 300,000 km2 in the adjacent Caribbean and provides for a significant increase in concentration of nutrients and photosynthetic pigments (Martín & Bone, 2007; Muller-Karger et al., 1989). The region is also influenced by the Guiana current, which flows parallel to the coastline towards the northwest (~106m3/s). The Guiana current originates from the Brazilian current and forms high-energy whirlpool structures that may surpass in intensity the normal circulation and consequently cause transitory episodes of current reversal. The Amazon river also affects this area during the first six months of the year, when its waters extend to the northwest, increasing turbidity in coastal waters, and creating a large plume and sections of brackish water offshore. Tides are very important at the local level particularly because of associated currents. Tides in this region are mostly semidiurnal, but in the Gulf of Paria, tides are mixed. Within the Gulf, the height of the tide is magnified within an increasing gradient from Boca del Dragón to the south,

Based on ecological and biological features, and aiming toward a better conservation strategy, the area was classified into seven subregions (Figure 1), defined according to the internal variability of their ecosystems, communities, and populations, including those of the terrestrial areas when these are included in the landscape (Klein & Cárdenas, 2009). The subregions, along with the main marine or estuarine features that characterize

Subregion 1: Paria Peninsula. This zone is characterized by a high landscape heterogeneity, with beaches, coves, a few rocky shores, and wetlands (Mata Redonda and

Subregion 2: Sac of the Gulf of Paria. This is a shallow water zone with a depth of 0-15 m characterized by extensive and tall mangrove formations that comprise a heterogeneous wetland with interconnected small channels into which the salt water penetrates. In this region, two estuarine systems (Caño Ajíes and Caño San Juan) are important fish reservoirs,

with high biomass of fish larvae of the families Sciaenidae and Lutjanidae.

best-preserved wetlands in South America (Figure 1).

reaching up to 2 m (Martín & Bone, 2007).

them, are:

Bajo Alcatraz).

Subregion 3: Pedernales. This is a shallow water zone with a depth of 0-15 m with important extensions covered by mangroves, and some beaches characterized by boulders. The region has a high abundance of commercial species of fish and crustaceans and it is an important fish reservoir of juvenile stages.

Subregion 4: Gulf of Paria. This zone between 15 m of depth and the limit of international waters serves as an important migratory route for sea mammals, turtles and birds, and as a feeding area for turtles. The area was under intense pressure from trawling fisheries for many years, which were stopped in 2009 with the passage of a new environmental law in Venezuela that mandated that intensive trawling activities cease. While trawling fisheries still take place, they are conducted at the same intensity as artisanal fisheries.

Subregion 5: Boca de Serpiente. This zone with a depth between 0 and 60 m has a complex hydrodynamic system due to the acceleration of marine currents. It is an important migratory route for sea mammals, turtles and birds. Its marine and estuarine biodiversity is relatively high, with high abundance of phytoplankton and zooplankton, including fish larvae. The area contains wetlands with a high biodiversity of birds and a continuous, extensive, tall mangrove formation. Its beaches are formed by muddy sediments and its benthic community shows marked seasonal variations.

Subregion 6: Boca Grande. At a depth between 0 and 60 m, this zone is under the direct influence of the discharge of many of the delta channels, including the largest or Rio Grande. The zone contains numerous islands of different sizes with fragmented mangrove formations. Erosion and sedimentation processes are very active, and the area is significantly influenced by freshwater input. Biodiversity associated with this area is mainly euryhaline.

Fig. 1. Map of the Orinoco Delta and Gulf of Paria region in the Venezuelan Atlantic front. Map shows the main ecosystems and human settlements. Bathymetry and elevation scales in meters.

Biodiversity and Conservation of the Estuarine

and Marine Ecosystems of the Venezuelan Orinoco Delta 71

reports mainly on fishes (Fowler, 1911, 1912, 1931), mollusks (Baker, 1923, 1925, 1927), and birds (Phelps & Phelps, 1950a, 1950b; Zimmer & Phelps, 1950). Between 1950 and 2000, a significant increase of studies in the region occurred with a commensurate amount of scientific literature was produced (Figure 2). The themes of these publications are variable

Fig. 2. Number of publications in books, conferences, journals technical reports, thesis and

others between 1950 and 2008 related to the Orinoco Delta and the Gulf of Paria.

Subregion 7: Oceanic region. Extending from the 60 m isobar to the limit of the Venezuelan border with international waters, this zone is characterized by mostly oceanic species, with low benthic abundance. The area is within important migratory routes for marine mammals, turtles and birds, and is considered an important nursery ground for fishes. In contrast to the other regions, the waters here are oligotrophic, with low primary productivity and low content of particulate organic matter.

#### **1.2 Local indigenous populations**

Within the *Orinoquia* (area related to the Orinoco river covering Venezuelan and Colombian territories), a total of 17 ethnic groups and cultures have been reported, but within the Orinoco Delta, the dominant group are the *Warao* (the "canoe people", or "low-land people"). For the *Warao*, the exploitation of natural resources is a delicate balance between man, nature, and supernatural beings. Any intervention by man must be compensated so the harmony between these three dimensions is maintained. In this way, they alternate the use of natural resources through permanent and through temporal settlements, their habitat, or entourage being the most important spatial concept. The *Waraos* are natural sailors with their *curiaras* (long canoes made of wood). Their main source of protein comes from fishing, but they also grow wild plants (*moriche* palm) and other cultivated plants such as banana, sugar cane and yucca. Besides obtaining starch from the *moriche* palm, they work to obtain the fibers with which they build baskets, roofs, *chinchorros* (hammocks), and fishing gear. Their hunting of terrestrial animals is limited to rodents and birds. The *Warao* population in the Orinoco Delta was nearly 24,000 individuals in the 1990s (Michelangeli, 2000) and grew to 36,027, according to the Venezuelan National Census in 2001, of which more than 75% still speak the *Warao* language. This is the second largest ethnic group in Venezuela, and constitutes 25% of the population of the Delta Amacuro state. The *Warao* villages are built along the edges of the many delta channels, their wooden houses (or *palafitos*) elevated by wood pillars to avoid flooding. Each village is composed of an "extended" family comprising four to five generations (~120 people). These small communities driven by marriage and movement are considered sub-tribes (Michelangeli, 2000). About 202 *Warao* villages have been reported in four of the seven subregions mentioned above: Sac of the Gulf of Paria, Pedernales, Boca de Serpiente, and Boca Grande (Klein & Cárdenas, 2009). Throughout the 20th century and still at present, the Warao have been subject to several socio-cultural, religious, and environmental impacts that have brought important changes to their lifestyle, mostly with negative consequences (García Castro & Heinen, 1999; García Castro, 2000). In 2009, an area of 12 km2 around each of the 202 villages was suggested as a conservation area to protect the *Warao* and their settlements, as well as the area under their direct use and influence, aiming to preserve their environment and the use they give to biodiversity, either for subsistence or for cultural reasons (Klein & Cárdenas, 2009).

#### **2. Brief history of research and species discovery in the region**

A bibliographic database containing 2,430 references within the time period of 1838 to 2008 was built and analyzed. The first recorded study was by Alexander von Humboldt (Humboldt, 1838) on the morphology, anatomy, distribution, and use of Orinoco manatees. During the late 1800s, a few works described the physical conditions of the Gulf of Paria (e.g. Guppy, 1895a) and provided records on mollusks (Guppy, 1895b, 1895c). Between 1900 and 1950, scientific literature related to the biodiversity of the area is very scarce with occasional

Subregion 7: Oceanic region. Extending from the 60 m isobar to the limit of the Venezuelan border with international waters, this zone is characterized by mostly oceanic species, with low benthic abundance. The area is within important migratory routes for marine mammals, turtles and birds, and is considered an important nursery ground for fishes. In contrast to the other regions, the waters here are oligotrophic, with low primary productivity and low

Within the *Orinoquia* (area related to the Orinoco river covering Venezuelan and Colombian territories), a total of 17 ethnic groups and cultures have been reported, but within the Orinoco Delta, the dominant group are the *Warao* (the "canoe people", or "low-land people"). For the *Warao*, the exploitation of natural resources is a delicate balance between man, nature, and supernatural beings. Any intervention by man must be compensated so the harmony between these three dimensions is maintained. In this way, they alternate the use of natural resources through permanent and through temporal settlements, their habitat, or entourage being the most important spatial concept. The *Waraos* are natural sailors with their *curiaras* (long canoes made of wood). Their main source of protein comes from fishing, but they also grow wild plants (*moriche* palm) and other cultivated plants such as banana, sugar cane and yucca. Besides obtaining starch from the *moriche* palm, they work to obtain the fibers with which they build baskets, roofs, *chinchorros* (hammocks), and fishing gear. Their hunting of terrestrial animals is limited to rodents and birds. The *Warao* population in the Orinoco Delta was nearly 24,000 individuals in the 1990s (Michelangeli, 2000) and grew to 36,027, according to the Venezuelan National Census in 2001, of which more than 75% still speak the *Warao* language. This is the second largest ethnic group in Venezuela, and constitutes 25% of the population of the Delta Amacuro state. The *Warao* villages are built along the edges of the many delta channels, their wooden houses (or *palafitos*) elevated by wood pillars to avoid flooding. Each village is composed of an "extended" family comprising four to five generations (~120 people). These small communities driven by marriage and movement are considered sub-tribes (Michelangeli, 2000). About 202 *Warao* villages have been reported in four of the seven subregions mentioned above: Sac of the Gulf of Paria, Pedernales, Boca de Serpiente, and Boca Grande (Klein & Cárdenas, 2009). Throughout the 20th century and still at present, the Warao have been subject to several socio-cultural, religious, and environmental impacts that have brought important changes to their lifestyle, mostly with negative consequences (García Castro & Heinen, 1999; García Castro, 2000). In 2009, an area of 12 km2 around each of the 202 villages was suggested as a conservation area to protect the *Warao* and their settlements, as well as the area under their direct use and influence, aiming to preserve their environment and the use they give to

biodiversity, either for subsistence or for cultural reasons (Klein & Cárdenas, 2009).

A bibliographic database containing 2,430 references within the time period of 1838 to 2008 was built and analyzed. The first recorded study was by Alexander von Humboldt (Humboldt, 1838) on the morphology, anatomy, distribution, and use of Orinoco manatees. During the late 1800s, a few works described the physical conditions of the Gulf of Paria (e.g. Guppy, 1895a) and provided records on mollusks (Guppy, 1895b, 1895c). Between 1900 and 1950, scientific literature related to the biodiversity of the area is very scarce with occasional

**2. Brief history of research and species discovery in the region** 

content of particulate organic matter.

**1.2 Local indigenous populations** 

reports mainly on fishes (Fowler, 1911, 1912, 1931), mollusks (Baker, 1923, 1925, 1927), and birds (Phelps & Phelps, 1950a, 1950b; Zimmer & Phelps, 1950). Between 1950 and 2000, a significant increase of studies in the region occurred with a commensurate amount of scientific literature was produced (Figure 2). The themes of these publications are variable

Fig. 2. Number of publications in books, conferences, journals technical reports, thesis and others between 1950 and 2008 related to the Orinoco Delta and the Gulf of Paria.

Biodiversity and Conservation of the Estuarine

such as birds and mammals, as well as plants (mangroves).

**3. Marine and estuarine biodiversity of the region** 

83 families, comprised of gastropods and bivalves (Table 1).

(Pannier, 1979; Conde & Alarcón, 1993).

**3.1 Invertebrates 3.1.1 Benthos** 

and Marine Ecosystems of the Venezuelan Orinoco Delta 73

La Salle Foundation of Natural Sciences (FLSCN) has the longest tradition of research in this area (Cervigón, 1965; Ginés & Cervigón, 1968; Ginés et al., 1971, 1972; Lasso, 1993; Monente & Colonnello, 1997, 2004; Ponte & Mochcco, 1997; Jorgensen et al., 2000; Lasso et al., 2002, 2004a, 2004b, 2008, 2009; Lasso & Meri, 2003; Martínez-Escarbassiere et al., 2003; Colonnello, 2004; Lasso-Alcalá et al., 2005a, 2005b, 2008, 2009; Achury et al., 2006; Lasso-Alcalá & Lasso, 2007; Schneider et al., 2007; Lasso & Sánchez-Duarte, 2011),, and in more recent years, due to the pressure from gas and oil companies to carry out offshore exploitation in the area, more institutions have become involved. Despite the great research effort completed, projects carried out in this region have been very focused, geographically localized and punctual in time (no time series data) as well as very isolated. The area is very vast, so most of it remains largely unexplored. As for biodiversity, the best known groups are the fish, mollusks, and crustaceans, groups that are of economic importance, and other vertebrates

The total number of species reported in the region is 2,118, of which 27% are planktonic species (not represented in the benthic community), 38% benthic, 21% fish, and nearly 15% other vertebrates. As in other 26 coastal regions of the world (Costello et al., 2010), half of all species richness is contributed by three groups: fish, crustaceans, and mollusks. Unlike these other 25 regions across the globe, where the contribution of other vertebrates, mainly mammals, reptiles and birds averaged only 2% and at most 8%, in the Orinoco Delta, the contribution of these groups is much higher, due to the extremely high bird species richness in this region (Martín & Bone, 2007). The following sections develop further the present

A total of at least 809 species-level taxa have been reported on benthic communities, from 5 animal phyla, 2 plant phyla (algae and angiospermae: mangroves and seagrasses) and only one group of protists (Foraminifera). Within these benthic communities, the group with the highest diversity is the crustaceans, with 310 species and 91 families reported, with amphipods and decapods comprising the greatest number (or highest percentage). The amphipod species are mainly marine, while decapods are represented by both marine and estuarine species. Mollusks represent the second most diverse group, with 189 species and

Phytobenthos are dominated by benthic algae, with 135 species and 33 families. Although eight seagrass species have been reported for the coast of Venezuela, none has been reported for the delta, only for the Gulf of Paria (Vera, 1992). The absence of seagrasses and benthic macroalgae might be a consequence of high loads of suspended matter and a lack of suitable substrates (Conde, 2000). The dominant terrestrial vegetation of the delta is the mangroves, with a mangrove formation between the Gulf of Paria and the Orinoco Delta representing more than 73% (183,500ha) of Venezuela's mangrove forest (Conde & Alarcón, 1993). Dominant mangrove species are the red mangrove *Rhizophora mangle*, the black mangrove *Avicennia germinans* and the white mangrove *Laguncularia racemosa*, though *R. harrisonii* and *R. racemosa*, the other two species of red mangrove have also been reported for the mid-delta

knowledge of biodiversity of the different communities of the Orinoco Delta.

and range from the abiotic to the biotic. In general, the number of publications has increased for most of the themes, with studies related to fish and fisheries the most prolific (Figure 3).

Fig. 3. Number of publications by themes between 1950 and 2008 related to the Orinoco Delta and the Gulf of Paria.

La Salle Foundation of Natural Sciences (FLSCN) has the longest tradition of research in this area (Cervigón, 1965; Ginés & Cervigón, 1968; Ginés et al., 1971, 1972; Lasso, 1993; Monente & Colonnello, 1997, 2004; Ponte & Mochcco, 1997; Jorgensen et al., 2000; Lasso et al., 2002, 2004a, 2004b, 2008, 2009; Lasso & Meri, 2003; Martínez-Escarbassiere et al., 2003; Colonnello, 2004; Lasso-Alcalá et al., 2005a, 2005b, 2008, 2009; Achury et al., 2006; Lasso-Alcalá & Lasso, 2007; Schneider et al., 2007; Lasso & Sánchez-Duarte, 2011),, and in more recent years, due to the pressure from gas and oil companies to carry out offshore exploitation in the area, more institutions have become involved. Despite the great research effort completed, projects carried out in this region have been very focused, geographically localized and punctual in time (no time series data) as well as very isolated. The area is very vast, so most of it remains largely unexplored. As for biodiversity, the best known groups are the fish, mollusks, and crustaceans, groups that are of economic importance, and other vertebrates such as birds and mammals, as well as plants (mangroves).
