**3. Community structure of corals and benthic components**

predicting to which species belongs an individual chosen at random from asample of Sspe‐ cies and Nindividuals. Pielou's index of evenness (J') which measures the proportion of the diversity observed in relation to the maximum expected diversity with values ranging from 0 to 1, where values close to1 means that all speciesare equally abundant [18]. We used mul‐ tivariate techniques in order to statistically support the comparisons between localities, both in the community structure of coral and fish. A similarity matrix was generated using the Bray-Curtis coefficient of similarity; this coefficient measures the similarity between two samples with values ranging from 0 to 1, where values close to 0 correspond to different samples and close to 1 correspond to equal samples. Using the similarity matrix we per‐ formed an Analysis of Similarity (ANOSIM) for assessing the differences in community structure between locations. In addition a cluster analysis classification was performed in or‐ der to detect if a group of samples have more similarity to others within a group [19]. In the case of nutrient concentrations we applied a variance analysis (ANOVA) to detect statistical‐

**Figure 1.** Sampling localities at the Marine National Parks of Isla Mujeres – Cancún – Nizuc (PNIMCN), Arrecifes de

Puerto Morelos (PNAPM) and Arrecifes de Cozumel (PNAC) during 2006 - 2007.

ly significant differences between the parks studied.

32 Environmental Change and Sustainability

The three National Marine Parks were established to conserve the natural ecosystems found within the area, but human activities have not been restricted entirely, and instead, human settlements have increased on the coast, using these habitats for recreation and tourism as well as for fishing within in the limits of the Parks, poaching included.

In order to determine the current status of the coral reefs of the Yucatan Peninsula, an analy‐ sis of benthic components of each of these marine parks was conducted. The characteriza‐ tion of benthic components of the reefs provides information about the current health status of the ecosystem. The percentage of coral cover, macroalgae, seagrass, and other inverte‐ brates, is reported from the sampled localities and subsequently analyzed their spatial and temporal variability. During the months of November 2006 (beginning of the dry season) and May 2007 (beginning of wet season) we surveyed the benthic composition of the coral reefs of the three marine parks using the Line Intercept Transect (LIT) method [20]. We sur‐ veyed five reefs at the PNIMCN, two reefs at PNAPM, and six reefs at PNAC (Table 1).

There were a total of 40 species of coral identified in the study area with the Cozumel Reefs National Park consistently containing the highest number of species: 25 coral species found at Paso del Cedral reef and 19 at Chankanaab reef (which is its maximum for this locality but the minimum for the PNAC). In general, *Porites astreoides* and *Acropora palmata* are the most abundant species in the Parks of Northern Quintana Roo, i.e., in Isla Mujeres - Cancun - Nizuc and Puerto Morelos. In the reefs of Cozumel, the most abundant species are *Agaricia agaricites* and *Siderastrea siderea*. Of all the coral reefs studied, Chitales reef, located at Punta Cancun, is the one with the lesser number of species (only seven species) (Table 1).

As for the diversity indices, we see a decrease, both in diversity and in species richness from South to North along the Quintana Roo coast; Cozumel reefs have the highest richness in‐ dex, being Dalila reef the one with the highest value of D '= 6.97. Also, Chankanaab reef to‐ gether with 'Colombia' reef presented the highest diversity values of H' = 2.19 nits/Ind and H' = 2.18 nits/Ind, respectively. Diversity indices decrease towards the North, with theChi‐ tales reef having the lowest diversity value of H '= 1.60 nits/Ind. Based on the Pielou even‐ ness index, the benthic community structure appears to be distributed evenly because the index values are relatively high; this is reinforced by the Simpson dominance index values obtained (Table 1) for Punta Nizuc reef (λ = 0.27) and for Yucab reef (λ = 0.19).

With regard to the percentage coral cover and macroalage a trend can be observed contrary to the diversity indices and the number of species as the highest percentage of coral cover was observed in the reefs of northern Quintana Roo. Particularly Yucab reef at PNAC had the highest diversity and species richness but was the one with the lowest coral cover. In the case of algae cover there is also a decrease from North to South, as the National Reef Park Isla Mujeres- Cancun -Nizuc (PNIMCN) have the highest percentages in algal cover decreas‐ ing to 17.01% in Cozumel (Figure2). Consistently, always PNIMCN reefs have higher algal cover compared to coral. At the reefs of PNAC algal cover is consistently less than algal cov‐ er at PNPM and PNIMCN.


**Table 1.** Ecological Indices for the coral reefs of three marine national parks studied in northern Quintana Roo (PNIMCM: ParqueNacional Isla Mujeres,Cancún, Nizuc; PNAPM: ParqueNacionalArrecife de Puerto Morelos, PNAC: ParqueNacionalArrecifes de Cozumel)

In order to simplify comparison of benthic component data obtained from the different reef localities, we formed a single component group called abiotc components by grouping bot‐ tom components such as rocks, sand, dead coral and other non-living components.

It is important to note that while Cozumel reefs have the highest species richness and diver‐ sity, and reduced algal cover, these reefs are characterized by a higher percentage of abiotic components (above 40%). In the case of Northern reefs it is the algae that contributes to the higher percentage of benthic components (Figure3). In the case of the reef sites of Punta Ni‐ zuc, Bonanza and Radio Pirata are characterized by the presence of seagrasses.

Applying the ANOSIM similarity analysis significant differences were detected between the various reefs studied (R = 0.497, p = 0.001), except for El Bajito reef, which in terms of the struc‐ ture of benthic components it was not significantly different from Chitales reef (R = -0.006, P = 0.51), being the two reefs part of the same national park (PNIMCN). At the Cozumel Reefs Na‐ tional Park, the Paso del Cedral reef and Delilah reef, Paraiso reef and Chankana'ab reef are the only reefs that present no significant differences in the structure of benthic components (R = 0.047, P = 0.142; R = -0.039 p = 0.75). This can be confirmed by a cluster analysis, that based on a similarity matrix generated using the Bray-Curtis, can be seen that the diagram is clearly divid‐ ed into two groups separating Cozumel reefs park (PNAC) from the parks of Puerto Morelos (PNAPM) and Isla Mujeres-Cancun-Nizuc (PNIMCN); and within this latter group, the sepa‐ ration between Puerto Morelos and PNIMCN can be clearly seen (Figure4).

Conservation and Sustainability of Mexican Caribbean Coral Reefs and the Threats of a Human-Induced Phase-Shift http://dx.doi.org/10.5772/54339 35

**Reef Loc. Coral**

34 Environmental Change and Sustainability

ParqueNacionalArrecifes de Cozumel)

**(%)**

**Algae (%)**

**No. of sp. Richness**

Cuevones 26.20 41.60 10 2.76 0.73 1.68 0.24 Chitales 16.91 49.09 7 2.12 0.82 1.60 0.25 El Bajito 16.17 50.17 17 5.75 0.73 2.07 0.21 Punta Nizuc 17.40 58.00 14 4.55 0.71 1.88 0.27

Radio Pirata 27.60 20.60 12 3.32 0.80 2.00 0.19

Chankanaab 15.69 39.31 17 5.84 0.77 2.19 0.15 Yucab 9.31 17.01 15 6.50 0.73 1.96 0.19 Paso del Cedral 18.33 21.18 18 5.93 0.72 2.09 0.20 Dalila 18.40 32.57 21 6.95 0.69 2.09 0.22 Colombia 22.22 21.88 16 4.85 0.79 2.18 0.14

PNIMCN Manchones 27.00 48.00 13 3.64 0.69 1.78 0.24

PNAPM Bonanza 12.40 41.20 12 4.37 0.77 1.93 0.21

PNAC Paraiso 11.32 24.51 14 5.40 0.77 2.03 0.18

**Table 1.** Ecological Indices for the coral reefs of three marine national parks studied in northern Quintana Roo (PNIMCM: ParqueNacional Isla Mujeres,Cancún, Nizuc; PNAPM: ParqueNacionalArrecife de Puerto Morelos, PNAC:

tom components such as rocks, sand, dead coral and other non-living components.

zuc, Bonanza and Radio Pirata are characterized by the presence of seagrasses.

ration between Puerto Morelos and PNIMCN can be clearly seen (Figure4).

In order to simplify comparison of benthic component data obtained from the different reef localities, we formed a single component group called abiotc components by grouping bot‐

It is important to note that while Cozumel reefs have the highest species richness and diver‐ sity, and reduced algal cover, these reefs are characterized by a higher percentage of abiotic components (above 40%). In the case of Northern reefs it is the algae that contributes to the higher percentage of benthic components (Figure3). In the case of the reef sites of Punta Ni‐

Applying the ANOSIM similarity analysis significant differences were detected between the various reefs studied (R = 0.497, p = 0.001), except for El Bajito reef, which in terms of the struc‐ ture of benthic components it was not significantly different from Chitales reef (R = -0.006, P = 0.51), being the two reefs part of the same national park (PNIMCN). At the Cozumel Reefs Na‐ tional Park, the Paso del Cedral reef and Delilah reef, Paraiso reef and Chankana'ab reef are the only reefs that present no significant differences in the structure of benthic components (R = 0.047, P = 0.142; R = -0.039 p = 0.75). This can be confirmed by a cluster analysis, that based on a similarity matrix generated using the Bray-Curtis, can be seen that the diagram is clearly divid‐ ed into two groups separating Cozumel reefs park (PNAC) from the parks of Puerto Morelos (PNAPM) and Isla Mujeres-Cancun-Nizuc (PNIMCN); and within this latter group, the sepa‐

**(D')**

**Eveness (J')**

**H' (nits/indv)** **Dominance (λ)**

**Figure 2.** Coral and algal cover (percentage) at the Northern Quintana Roo National Reefs parks for the years 2006-07. The dashed line represents the average coral cover (percentage) for each park.

**Figure 3.** Benthic components of the coral reefs at three National Marine Parks in Northern Quintana Roo during 2006-2007.

**Figure 4.** Cluster analysis of the coral reefs of Northern Quintana Roo (data for 2006-2007).
