3.1 Biodiversity

Biodiversity is a characteristic of nature and a property of living beings. It is a highly complex and nonlinear system, which is produced from a complex dynamic of interactions between living beings and their nonliving supports (physical, chemicals, etc.) through different contexts of time, geography, and cultures. The reef system is among the most biodiverse, equated with the tropical rain forest and linked to the ecological services provided by this interaction that finally integrates the environment and reflects the sensitivity of these services with concerning the depletion and disappearance of resources, communities, and populations. In this case we present the results obtained when investigating two lagoons of Atlantic Ocean reefs.

direction. Chinchorro Bank shows a similar tendency to Alacranes, where there is a descent from the south to the north, only that the trend slope is lower. The living

In relation to the organisms collected in the reef lagoons, three phyla with 70 species were registered, the disposition of the groups in each reef is presented in Table 1, and in the annex the presence of the species in each lagoon is recorded. Even though some species are presented in both reefs, the dominance percentage of the five most representative species is shown in Figure 3; they show that the dominance percentage of Orbicella annularis for Chinchorro Bank is higher and that for Alacranes reef decreases until the fourth place. On the other hand, the alga Lobophora variegata is presented in the second place in Chinchorro Bank but rises to

The richness of species is lower in Chinchorro, since the sites that present the

Table 2 seeks to gather the general information of the two ocean reefs, their origin, presenting the totals in terms of their size, as well as the parameters of total

Groups Alacranes reef Chinchorro Bank

The five species with the highest percentage of dominance. (A) Alacranes reef, (B) Chinchorro Bank lagoons.

Algae 11 8 Sponges 18 4 Hydrozoa 2 2 Hard corals 18 16 Soft corals 9 9 Total 58 39

Species number per group registered in Alacranes reef and Chinchorro Bank lagoons.

substrate increases also from the south to the north with a similar slope.

Lagoons Reefs of Alacranes Reef and Chinchorro Bank: Ocean Reef of Mexican Atlantic

the first in Alacranes reef; however, the dominance percentage is similar.

value (Figure 4C, E).

Table 1.

Figure 3.

215

diversity that are presented in both lagoons.

DOI: http://dx.doi.org/10.5772/intechopen.88662

greatest richness reach only seven species, while in Alacranes most sites are between 15 and 20, reaching in the southern area up to 40 species (Figure 4A, D). Diversity in Chinchorro Bank goes from 0 (one species) to 2.4 bits/ind., while in the Alacranes reef, it goes from 1 to 4.3 bits/ind. (Figure 4B, E). Equitability has similar behavior to diversity in both reefs, reaching 0.9 as its maximum

In both reefs the nonliving substrate generally has a higher percentage (Figure 2); however, in some places living coverage exceeds the substrate. On the other hand, on the Alacranes reef, only three sites are given this situation also in the southern part (Figure 2A). Some areas of the Chinchorro Bank, especially the southern part, show greater coverage than inert substrate (Figure 2B). Generally, the tendency for Alacranes reef is a decrease in living coverage from the south to the north, and consequently an increase of the substrate does not live in that

Figure 2.

Live coverage and inert substrate percentages in the reef lagoons. (A) Alacranes reef, (B) Chinchorro Bank.

Lagoons Reefs of Alacranes Reef and Chinchorro Bank: Ocean Reef of Mexican Atlantic DOI: http://dx.doi.org/10.5772/intechopen.88662

direction. Chinchorro Bank shows a similar tendency to Alacranes, where there is a descent from the south to the north, only that the trend slope is lower. The living substrate increases also from the south to the north with a similar slope.

In relation to the organisms collected in the reef lagoons, three phyla with 70 species were registered, the disposition of the groups in each reef is presented in Table 1, and in the annex the presence of the species in each lagoon is recorded.

Even though some species are presented in both reefs, the dominance percentage of the five most representative species is shown in Figure 3; they show that the dominance percentage of Orbicella annularis for Chinchorro Bank is higher and that for Alacranes reef decreases until the fourth place. On the other hand, the alga Lobophora variegata is presented in the second place in Chinchorro Bank but rises to the first in Alacranes reef; however, the dominance percentage is similar.

The richness of species is lower in Chinchorro, since the sites that present the greatest richness reach only seven species, while in Alacranes most sites are between 15 and 20, reaching in the southern area up to 40 species (Figure 4A, D). Diversity in Chinchorro Bank goes from 0 (one species) to 2.4 bits/ind., while in the Alacranes reef, it goes from 1 to 4.3 bits/ind. (Figure 4B, E). Equitability has similar behavior to diversity in both reefs, reaching 0.9 as its maximum value (Figure 4C, E).

Table 2 seeks to gather the general information of the two ocean reefs, their origin, presenting the totals in terms of their size, as well as the parameters of total diversity that are presented in both lagoons.


#### Table 1.

3. Results

Ocean reefs.

Figure 2.

214

3.1 Biodiversity

Biodiversity is a characteristic of nature and a property of living beings. It is a highly complex and nonlinear system, which is produced from a complex dynamic of interactions between living beings and their nonliving supports (physical, chemicals, etc.) through different contexts of time, geography, and cultures. The reef system is among the most biodiverse, equated with the tropical rain forest and linked to the ecological services provided by this interaction that finally integrates the environment and reflects the sensitivity of these services with concerning the depletion and disappearance of resources, communities, and populations. In this case we present the results obtained when investigating two lagoons of Atlantic

Lagoon Environments Around the World - A Scientific Perspective

In both reefs the nonliving substrate generally has a higher percentage (Figure 2); however, in some places living coverage exceeds the substrate. On the other hand, on the Alacranes reef, only three sites are given this situation also in the southern part (Figure 2A). Some areas of the Chinchorro Bank, especially the southern part, show greater coverage than inert substrate (Figure 2B). Generally, the tendency for Alacranes reef is a decrease in living coverage from the south to the north, and consequently an increase of the substrate does not live in that

Live coverage and inert substrate percentages in the reef lagoons. (A) Alacranes reef, (B) Chinchorro Bank.

Species number per group registered in Alacranes reef and Chinchorro Bank lagoons.

The five species with the highest percentage of dominance. (A) Alacranes reef, (B) Chinchorro Bank lagoons.

#### Figure 4.

Richness (A, D), diversity (B, E), and equitability (C, F) in the lagoons of Alacranes (ABC) and Chinchorro (D,E,F) reefs. The three areas are south, central, and north.


The Chinchorro Bank sampling sites form nine groups at a level of 50%. The largest of them includes eight stations, of which six belong to the south zone, one to the central part on windward, and one of the north zone in leeward. Group II gathers five sites of which three are in the south zone, one in the central part on windward, and one in the north area in leeward. The third cluster is exclusive to the southern zone. Cluster IV is made up of two sites in the south windward area and one in the center of the central area. Group V has three exclusive sites in the middle

Sites similarity given by the Bray-Curtis index. (A) Alacranes reef, (B) Chinchorro Bank lagoons.

Lagoons Reefs of Alacranes Reef and Chinchorro Bank: Ocean Reef of Mexican Atlantic

DOI: http://dx.doi.org/10.5772/intechopen.88662

area, two of them close to the island of Cayo Centro and one of them on the windward edge. The sixth cluster has five stations, almost all of them from the middle area, except for a site located in the south area. Group VII has four locations, close to each other in the central area except for one of them located in the leeward area. The eighth cluster is formed by two stations in the central zone and the other in the north. The last group consists of two sites in the central area, one on the

In relation to the spatial distribution of species of Alacranes reef, there were 58 species (flora and fauna) that also form, most of them, a large conglomerate close to the three axes of coordinates. There were paired associations as in the case of Amphimedon compressa with Stephanocoenia intersepta, Siderastrea siderea, and Millepora alcicornis, among others; Antillogorgia bipinnata, Porites astreoides, Agaricia agaricites, Dictyota sp., Acanthophora spicifera, and Isophyllia sinuosa move

In Chinchorro Bank, it has to be generally presented that for 39 species most of

them cluster at the origin of the three axes, forming a large group. The species Halimeda incrassata and Lobophora variegata show a very close relationship, while the species Callyspongia plicifera, Antillogorgia acerosa, Agaricia agaricites, Orbicella annularis, Eunicea mammosa, Eunicea flexuosa, and Gorgonia flabellum are out of any

windward edge and the other in the leeward (Figure 5B).

3.3 Spatial species distribution

Figure 5.

away from any grouping (Figure 6A).

conglomerate (Figure 6B).

217

#### Table 2.

Alacranes reef and Chinchorro Bank characteristics.

#### 3.2 Site affinity

The similarity given by the Bray-Curtis index, of the Alacranes Reef, forms seven groupings: The first is formed by two sites in the northern area. The second clusters more sites (11), which are distributed throughout the reef; however, at lower levels, sites of the same area or at least contiguous areas such as stations 8, 12, and 18 are associated. The third group joins two stations: one from the central zone and the other from the north.

The four clusters include five stations that although they identify some area, some site of another area is joined as is the case of sites 19, 20, 21, and 23, elements of the central zone to which site 28 of the north zone is joined. The fifth group relates eight sites, showing an association that completely identifies the area in the south. The sixth cluster has five sites, most of them from the south zone and only one from the north zone (site 29). The seventh group has only two sites: one of the south zone and one of the north (Figure 5A).

Lagoons Reefs of Alacranes Reef and Chinchorro Bank: Ocean Reef of Mexican Atlantic DOI: http://dx.doi.org/10.5772/intechopen.88662

Figure 5. Sites similarity given by the Bray-Curtis index. (A) Alacranes reef, (B) Chinchorro Bank lagoons.

The Chinchorro Bank sampling sites form nine groups at a level of 50%. The largest of them includes eight stations, of which six belong to the south zone, one to the central part on windward, and one of the north zone in leeward. Group II gathers five sites of which three are in the south zone, one in the central part on windward, and one in the north area in leeward. The third cluster is exclusive to the southern zone. Cluster IV is made up of two sites in the south windward area and one in the center of the central area. Group V has three exclusive sites in the middle area, two of them close to the island of Cayo Centro and one of them on the windward edge. The sixth cluster has five stations, almost all of them from the middle area, except for a site located in the south area. Group VII has four locations, close to each other in the central area except for one of them located in the leeward area. The eighth cluster is formed by two stations in the central zone and the other in the north. The last group consists of two sites in the central area, one on the windward edge and the other in the leeward (Figure 5B).

#### 3.3 Spatial species distribution

In relation to the spatial distribution of species of Alacranes reef, there were 58 species (flora and fauna) that also form, most of them, a large conglomerate close to the three axes of coordinates. There were paired associations as in the case of Amphimedon compressa with Stephanocoenia intersepta, Siderastrea siderea, and Millepora alcicornis, among others; Antillogorgia bipinnata, Porites astreoides, Agaricia agaricites, Dictyota sp., Acanthophora spicifera, and Isophyllia sinuosa move away from any grouping (Figure 6A).

In Chinchorro Bank, it has to be generally presented that for 39 species most of them cluster at the origin of the three axes, forming a large group. The species Halimeda incrassata and Lobophora variegata show a very close relationship, while the species Callyspongia plicifera, Antillogorgia acerosa, Agaricia agaricites, Orbicella annularis, Eunicea mammosa, Eunicea flexuosa, and Gorgonia flabellum are out of any conglomerate (Figure 6B).

3.2 Site affinity

H0

H0

J

Table 2.

216

Figure 4.

Area (km<sup>2</sup>

Island area [km<sup>2</sup>

Lagoon area [km<sup>2</sup>

and the other from the north.

Alacranes reef and Chinchorro Bank characteristics.

south zone and one of the north (Figure 5A).

The similarity given by the Bray-Curtis index, of the Alacranes Reef, forms seven groupings: The first is formed by two sites in the northern area. The second clusters more sites (11), which are distributed throughout the reef; however, at lower levels, sites of the same area or at least contiguous areas such as stations 8, 12, and 18 are associated. The third group joins two stations: one from the central zone

Richness (A, D), diversity (B, E), and equitability (C, F) in the lagoons of Alacranes (ABC) and Chinchorro

Attribute Alacranes reef Chinchorro Bank Origin Pleistocene-Cretaceous Cenozoic: Pliocene-Pleistocene

Islands 5 4

Insular percentage 1.7 0.40

Surrounding water depth (m) 52 m +500 m S (species no.) 58 39 H<sup>0</sup> (bits/ind.) 4.44 4.38

max (bits/ind.) 5.85 5.25

min (bits/ind.) 0.127 0.308

<sup>0</sup> 0.759 0.834

) 300 1443.6

] 0.53 5.82

] 299.755 533.79

(D,E,F) reefs. The three areas are south, central, and north.

Lagoon Environments Around the World - A Scientific Perspective

The four clusters include five stations that although they identify some area, some site of another area is joined as is the case of sites 19, 20, 21, and 23, elements of the central zone to which site 28 of the north zone is joined. The fifth group relates eight sites, showing an association that completely identifies the area in the south. The sixth cluster has five sites, most of them from the south zone and only one from the north zone (site 29). The seventh group has only two sites: one of the

(the second form of environmental change). In turn, environmental variability has been conceptually used to frame all possible values that may exhibit the physical

Alacranes reef can be considered as the most studied coral complex of the Mexican seas due to its extraordinary characteristics, which place it within the most

described for more than a century [40] but, until the late 1950s, began to be studied more or less constantly, mainly by foreigners [41]. Alacranes has a vast history of shipwrecks and has been a point of attraction of visitors since colonial times [42]. The Yucatan Peninsula is a platform of sedimentary origin, constituted by a karstic Quaternary complex. It is the most recent emersion area in the country, and its growth is associated with sediment coastal transport processes and marine transgression and regression cycles. Therefore, Alacranes is of recent formation, originated by the biological action of the corals with the gradual deposit of calcareous material during the Pleistocene and Cretaceous, favored by the slow immersion of the Yucatan Peninsula [43]. Alacranes sits on a terrace of 51–64 m that is supposed to be carved during the descent eustatic sea level at the end of Wisconsin or at the beginning of the transgression Holocene (11,000 years ago), hence began the modern reef growth, arriving some 5000 years, both the reef and the sea level, to its

extensive and important coralline masses of the country [39]. The reef was

Lagoons Reefs of Alacranes Reef and Chinchorro Bank: Ocean Reef of Mexican Atlantic

current values [44]. The area is a platform reef of approximately 300 km<sup>2</sup>

of conservation of the reef can be considered good [48].

219

rises 50 m from the seabed. According to several investigations [45], it is known that the pattern of currents and the contribution of nutrients for the Alacranes reef come from the upwelling process that originates in the eastern end of the Yucatecan platform. The current of the Caribbean, as it passes through the Yucatán Strait and ascends on the platform, contributes high values of nutrients and therefore a high productivity [46]. Thanks to this contribution, there are commercial fisheries of lobster (Panulirus argus) and the groupers (Epinephelus sp.) [47]. The general state

Alacranes is a resting area for migratory birds that cross the Gulf of Mexico; particularly one of the islands of the Alacranes reef is considered one of the most important breeding areas in the world for the bird Sula dactylatra. Thus, it is considered an important area for the conservation of birds of the country [49], especially with a record of 110 species between accidental and permanent residents in the reef. In the reef environment, the management program has registered 34 species of corals, some of which are considered species under special protection [50] —in this assessment we report 28. According to the Alacranes bathymetric characterization, the slope of windward descends to an average of 55 m of depth; in the north part there is a marked inflection of the profile in comparison of the areas center and south, where the slope descends gently. The windward slope is the only site on the Alacranes reef where the stony corals of the genus Orbicella/Montastraea are not dominant. The dominance corresponds to Siderastrea radians. One of the characteristics of this area is the high density of soft corals or octocorals; the dominant genus is Pseudopterogorgia, although Gorgonia flabellum is also frequent and reaches large size. In addition to these, the genera Eunicia, Plexaura, and Plexaurella are represented in this part, like the one reported by other studies [42, 51]. The barrier reef is physiographically one of the most conspicuous elements of the system, and like any barrier reef, in turn is divided into outer barrier, west in the case of Alacranes, reef crest, and inner barrier [52]. The outside is the one that is exposed to the prevailing winds and the persistent swell train. Along the barrier at different points, it reaches the surface. The notorious dominance of the Palythoa caribbeaerum colonial anemone extends to the areas of the crest and the inner barrier. In the shallow part, between three and four meters of depth, the Hydrozoa Millepora alcicornis is frequent, like Gorgonia flabellum. In this area, the hard corals

, which

and chemical characteristics of a benthic habitat [37, 38].

DOI: http://dx.doi.org/10.5772/intechopen.88662

Figure 6.

Spatial ordination of the species found in the reef lagoons. (A) Alacranes reef, (B) Chinchorro Bank.
