1. Introduction

Coral reefs are one of the most diverse communities on the planet and the most diverse in the marine environment; they occupy less than 1% of the bottom of the ocean but are inhabited by 25% of all the marine species currently present [1]. In the Caribbean, coral reefs emerged about 27–30 million years ago in the mid-Oligocene, reaching outstanding development during the Miocene and part of the Pliocene (23–2.5 million years) due to the enrichment of species from the Pacific Ocean to the closure of the Isthmus of Panama [2], which confers it to be one of the oldest environments of the Earth [3].

It is built by living beings of the Scleractinia group that are the main builders and that rise from the bottom to the surface and that by its dimensions and physical structure, influence the environment. Its inhabitants are very diverse and have specific adaptations to each part of this system; therefore, the system has high sensitivity to external agents and an enormous complexity. They are systems located between the tropics, with high temperatures of 18–28°C, surrounded by

clear oligotrophic waters, with high oxygenation, and a salinity of 35 parts per thousand [4].

2.1 Study area

2.1.1 Alacranes reef

530.407 m<sup>2</sup>

2.1.2 Chinchorro Bank

211

reserve.

Both reefs are oceanic and the largest in Mexico and are marine protected areas: Alacranes reef with the National Park status and Chinchorro Bank as a biosphere

The physiographic reef structure makes it possible to recognize two sections,

N, 89°410

, representing 1.7% of the area [13]. By virtue of the intense dynamics of

the islands, their shape and dimensions can vary from the order of meters or tens of meters in short periods of time [11]. All cays are very low with maximum height of 3–4 m. A Thalassia testudinum seagrass bed and other algae are frequent in the lagoon reef. The cays are important site for nesting seabirds and nesting green turtles. Sharks are abundant in shallow waters; the management program [5] reported 116 bird species, 136 fishes, 24 species of shark, and 34 coral species. The reef is currently visited by fishermen who collect queen conch and other shells. Lobsters and grouper are also taken, mainly by skin diving and spear gun. The tourism is more and more frequent. The area has frequent climatological

disturbance (winds of the north and hurricanes). The area has a forbidden period

–18°23<sup>0</sup>

coast of southeastern Quintana Roo, México, between Xcalak and the Ubero and about 100 km north from Turneffe Island in Belize. This reef is part of the Great Atlantic Reef Belt (second world barrier). Chinchorro has an area of 53.379 ha. It is a kidney-shaped prominence and is separated from the mainland by a 1000-m-deep channel [14]. The current is very strong (often over two knots). There are four cays: Cayo Norte (two mangrove-covered islands with an area of 2645.2 ha, destined for the protection of the reef); Cayo Centro, the largest, is a mangrove island with few little inner lagoons with an area of 1263.76 ha, comprises the entire cay and adjacent waters; and Cayo Sur (or Lobos), the smallest (300 m long), is a sandy bank, the only close to the windward margin of the atoll, with 678.53 ha, destined mainly to the protection of the elkhorn corals; all the cays represent 5.82% of the total area of

N, 87°14<sup>0</sup>

–87°27<sup>0</sup>

W, and 24 km off

; lagoon reef maximum depth is

for the conch and lobster for the Fish Secretary decree.

the reserve [15]. The reef has an area of 1443.6 km<sup>2</sup>

Their geographical location is 18°47<sup>0</sup>

W, and 135 km off coast of Port

windward and leeward, and at least four main areas, South Lagoon, Central

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

Progreso on the Yucatan Shelf. This reef is the largest and most complex of the series of reef lying along the edge of the Campeche Sound. The reef has the form of the atoll with northwest trend, due in part by winds and strong westerly currents. Its sub-oval pattern of outer reefs encloses shallow lagoon, and relationship to the Campeche Sound characterizes it as a shallow lagoon shelf atoll [11, 12]. The surrounding waters are 52 m deep. The lagoon reef maximum depth is 20 m in the north. We recognize a semicircular well-developed windward reef on the eastern side and leeward margin less sharply defined belt of reef growth. The windward reef forms a continuous barrier along the north, east, and southeast. The leeward side is characterized by small patch reefs and submerged sandbars. The lagoon is filled with microatolls giving a reticular pattern. There are five sand cays on the leeward rim of the reef: Bird or White Island, Isla Chica, Pérez Island, Dead Island, or Deserter and Banished Island. The total area recorded for the five islands is

Lagoon, North Lagoon, and reef crest that border each reef.

Their geographical location is 22°230

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

In addition to the high diversity in which these ecosystems live and develop, they are very productive marine communities. They play a critical role as habitat and protection areas of approximately 10–20% of the world's fisheries [5, 6].This great system consists of sections that confer zoning. These sections can or will not be presented according to the type of reef in question, providing a distinctive and unique trait to each one. In our case, we will focus on the description of one of these sections, the reef lagoon, and we will do this by confronting the two largest reefs in Mexico, Alacranes Reef and Chinchorro Bank, both of them belong to the Atlantic Ocean, but their structures, characteristics, and components are different.

Both reefs have been studied under different aspects ranging from shipwrecks, [5] ecology [6, 7], biology [8], sociology [9], and paleontology [10], which gives us an idea of the importance of these ocean reefs to the country in relation to the exploitation of its natural resources, conservation, and even its importance in the delimitation of the territorial sea and consequently its sovereignty.

One of the fade questions, however, was: are these reefs subject to the same ecological-environmental pressures and controllers even though they belong to two different ocean systems? To get closer to this response, we try to put the reader in context by making a wide description of each reef highlighting its ecological, fishing, and tourist importance, showing the results obtained through two sampling periods in the lagoon in particular and discussing them in relation to the southern, central, and northern areas of each of them, the leeward and windward zones and above all their membership in one or another ocean system.

One of the objectives of this research is to determine whether there are differences in the processes that occur in a given area of the reef, and this will lead to different ideas about whether it is possible to propose conservation and management plan differentials; different surveillance efforts, in the case of protected areas; differences in the natural resources exploitation, etc. That is the importance of this study. In the biological-ecological sense, there are also a number of objectives such as identifying the most important species in the structure of the lagoon community, knowing the dominant species in each area, and determining whether there is a substitution of species in each time period and above all knowing how stability is in the broader sense of this area of the reefs, recognizing that corals can be under such pressure that they can suffer disease and even death when the ambient conditions change rapidly without giving time to acclimatization. Around the world there is concern about coral reef conditions, especially because of the multiple problems they face such as coastal development and alterations by human influence that lead to a higher rate than estimated. Solutions to this problem can only be given through a vigorous drive for scientific research, particularly ecological and necessarily multidisciplinary that proposes informed procedures with firm scientific foundations. Fortunately, there are national and international efforts to preserve the health of reefs by restraining their arguments and procedures in scientific discoveries; we are sure that our contribution will serve as a further support to the efforts of conservation of these reefs.
