DISTRIBUTION AND ABUNDANCE OF SEAGRASSES OF BONTOC, SOUTHERN LEYTE

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1 DISTRIBUTION AND ABUNDANCE OF SEAGRASSES OF BONTOC, SOUTHERN LEYTE Abstract The seagrass areas of Bontoc, Southern Leyte, Philippines were studied to determine the seagrass species composition, distribution, abundance, and status of the habitat. The study utilized a modified field sampling design based from the intertidal fixed transect sites of McKenzie et al. (2003) and the sampling scheme of English et al. (1997). It was observed that multispecies and monospecific seagrass communities were abundant in the study area, Halodule pinifolia being the most abundant species among all the seagrasses.the seagrass habitats were disturbed by anthropogenic activities, and human impacts were prominent in terms of improper waste disposal and sewage discharge to the seagrass beds. Keywords: Halodule, Enhalus, Cymodocea 1.0 Introduction The fishing community of Bontoc, Southern Leyte, Philippines has been reported to be greatly dependent on the coastal resources of Sogod Bay.The fishing operations are categorized as small-scale municipal fishing and done mainly to meet subsistence needs. Moreover, fisherfolks have stated that fish catches have been declining for a decade already and has compromised food security (Espinas et al. 2010). Fish decline may indicate possible degradation of most of the marine ecosystems, including seagrass areas of Bontoc. Seagrass meadows support a rich diversity of species from neighboring systems and provide shelter for both commercially and ecologically important marine organisms (Fortes and Santos 2004). The seagrass areas of Bontoc could be heavily exploited and highly disturbed thus resulting in lower fish catch. Complex seagrass habitats can enhance the diversity and abundance of animals (Salita et al. 2003). They are often closely linked to other marine communities. In the tropics, the associations are likely to be the complex interaction with other marine ecosystems (i.e. mangroves and coral reefs) (McKenzie et al. 2003). Seagrass beds have been found to harbor more fish and have higher fish species diversity than adjacent areas with no vegetation (Salita et al. 2003). However, most seagrass areas are being exploited not only for fishing

2 94 but also for developmental purposes (Calumpong and Meñez 1994). In Bontoc, seagrass areas are not a management priority. The presence or absence of seagrasses in the coastal areas has not been thoroughly studied. There were even no documentation of the different seagrass species in the municipality. This study aimed to document the seagrasses found in the intertidal areas of Bontoc. Determined during the conduct of the study were species composition, distribution, abundance, in terms of percentage cover, and status of seagrasses. Such information will serve as a baseline for identifying significant areas in the municipality that need utmost attention. Data gathered will enable resource managers to make proper decisions regarding seagrass management with greater confidence. This study can also serve as a reference for monitoring environmental impacts on coastal areas especially for seagrass ecosystems. 2.0 Research Design and Methods Study Sites There were seven coastal barangays selected based on the presence of seagrass beds in the areas for the assessment of the distribution and abundance of seagrasses in the intertidal areas of the Municipality of Bontoc, Southern Leyte, Philippines. These include Brgys. Union, Divisoria, Sto. Niño, Poblacion, Talisay, Casao and Sta. Cruz (Fig. 1) which are part of the western side of Sogod Bay and is bordered by narrow intertidal areas. Table 1 shows the geographic location of the different sites where the transects were laid as well as the substrate types per site. The substrate types per site were also noted. Moreover, Bontoc has a narrow intertidal area and a tidal window for access of around five hours. Figure 1. Map of the Municipality of Bontoc, Southern Leyte indicating the seven Coastal barangays

3 95 Table 1. The GPS coordinates at the start of every transect line per study site in Bontoc, Southern Leyte Field Sampling Design The study followed a modified field sampling design based from the intertidal fixed transect sites of McKenzie et al. (2003) while the sampling scheme of English et al. (1997) was used. Field sampling data gathered from April to May 2010 utilized a total of 21 transects each having a length of 50 m; three transect lines laid per study site each separated from each other by a distance of 50 m (Fig. 2). For each transect, ten sampling stations were created at five meter intervals along each transect. Figure 2. The field sampling design based from the model of McKenzie et al. (2003)

4 96 Field Sampling of Seagrasses The study used the seagrass species identification keys compiled by McKenzie et al. (2003) and a key to the Philippine seagrasses by Meñez et al. (1983) to identify the seagrass species within each replicate quadrat. It also determined the distribution and abundance of seagrasses using the transect-quadrat method (English et al. 1997). The geographic location at the start of each transect was recorded using a global positioning system (GPS) (Garmin GPS72). Each transect was laid perpendicular to the shore where the seagrass habitat began using a handheld compass. There were three replicate transects at each site. Estimation of the percent cover for each seagrass species found in each quadrat was done using the 10 cm grids of the quadrats. A score was given to each species found in the grid using the categories developed by Saito and Atobe (1974) as shown in Table 2. Table 2. Classes of dominance for estimating percent cover of seagrasses Data Analysis Calculations for the cover (C) of each species in each 0.5 m x 0.5 m quadrat are as follows (English et al. 1997): Where: Mi = midpoint percentage of Class i; f = frequency (number of sectors with the same class of dominance (i)). The cover for each transect was determined by dividing the sum of the average covers for each sampling station by the number of sampling stations utilized. The corresponding seagrass percent cover per study site was determined by getting the total percent cover of the transects divided by the number of transects used for each study site. Status The status or condition of the assessed seagrass habitats was determined by utilizing the criteria for evaluation of Fortes (1989) as cited by Deguit et al. (2004) as shown in the table below.

5 97 Table 3. Criteria for evaluating the status or condition of seagrass habitat from Fortes (1989) as cited by Deguit et al. (2004). Diversity Shannon-Weiner diversity index was computed to determine the seagrass diversity for the evaluation of the status or condition of seagrass areas. The diversity index was calculated in the following manner: where pi is the proportion of individuals found in species i and computed as: pi = ni/n, where ni is the percent cover per species i and N is percent cover of seagrasses per study site 3.0 Results and Discussion Species Composition and Distribution of Seagrasses Recorded were a total of seven seagrass species in the intertidal area of Bontoc, Southern Leyte. The seagrass species identified were Enhalus acoroides, Halophila minor and H. ovalis belonging to family

6 98 Hydrocharitaceae and Cymodocea rotundata, C. serrulata, Halodule pinifolia and H. uninervis belonging to family Cymodoceaceae. There are 60 seagrasses described worldwide (McKenzie et al. 2003) and the observed number of species represents around 12% of the species in the world. In the Philippines, there are 18 species (Fortes 2004) and the study recorded about 38% of the country s known species. As reflected in Table 3, six of the seagrass species encountered in the study were from Talisay while five species were from the Poblacion. Most of the study sites such as Union, Sto. Niño and Sta. Cruz had only four species. Divisoria had three species present while lowest number of species was in Casao where only monospecific stands of H. ovalis was recorded.

7 99 Table 4. Seagrass composition of the study sites The differences in the species composition per study site could be attributed to the physical characteristics of the study sites, especially the substratum. The substratum is a very important regulator of seagrass distribution (Greve and Binzer 2004). Halophila ovalis thrived in Casao because the area had a sand-coralline substrate that most of the observed species could not tolerate. The other study sites had sandy to muddy substrates that suited the rest of the observed species. According to McKenzie et al. (2003), Halophila is known as a pioneer species that can tolerate a wide range of substrates. Moreover, the species was found in the deeper portions of Casao where waters can reach up to six meters deep which exemplifies the ability of the species belonging to Halophila to grow deep in regions (McKenzie et al. 2003). Percentage Cover and Diversity of Seagrasses Halodule pinifolia was the most abundant species in Bontoc in terms of percent cover. Halodule species covered most of the sites. According to Phillips and Meñez (1988), these species are pioneer species that occur in intertidal areas that are capable of growing in disturbed areas. In addition, H. pinifolia is also a commonly distributed species in tropical areas (Meñez et al. 1983). The dominance of H. pinifolia in Bontoc is similar to the findings of United Nations Educational, Scientific and Cultural Organization (UNESCO 2002) in Ulugan Bay, Palawan, an area reported as having extensive seagrass beds. As shown in Fig. 3, Union had the highest total mean cover

8 100 (26.69%) among all the study sites. Cymodocea rotundata (16.87%) dominated the area. The growth of this species was favorable in Union because it has a shallow water environment of sand-mud or sand substrates near river mouths that it prefers. Poblacion and Talisay followed with % and 21.70% cover, respectively. Although Divisoria has only three species of seagrasses, it obtained a cover of 14.35% because of the occurrence of the Halodule species. The site is near the Divisoria River, which subject the area to sedimentation. The Halodule species can survive this disturbance because they are eurybiontic allowing these species to have a wide range of tolerance to environmental factors. Casao had a very poor cover of 4.44% mainly due to the topography of the substratum that was only tolerable to H. ovalis. The area was mostly rocky at the first 15m of the intertidal area and had some coral reef patches seaward. Only a minimal area of sandy-coralline substrate was available for seagrasses to thrive on. Figure 3. Seagrass cover from the seven coastal barangays of Bontoc, Southern, Leyte Most of the areas have low diversity indices due to the dominance of some seagrass species over others like in Union and due to low number of species as in Casao, where only one species was observed (Table 5). Among all the study areas, Sta. Cruz had the most diverse seagrass area. The four species present on the area were more evenly distributed than the seagrasses found in other study areas. Seagrass Status Following the criteria for evaluation by Fortes (1989) as cited

9 101 by Deguit et al. (2004), the seagrass beds in Bontoc can be classified as a disturbed seagrass area. Moreover, the areas were also observed to receive constant anthropogenic disturbance. Human settlements were observed in all sites as well as infrastructures for recreational purposes (Fig. 4). b a Figure 4. Human settlements along the coast of Sta. Cruz (a) and recreational structure in Casao (b) Pollution was also observed in the area. In Poblacion, the effluents of the town proper flow into the seagrass area (Fig. 5). Moreover, during low tide several garbage materials would be found littered among the seagrasses. Figure 5. Outlet of the drainage system of Poblacion, Bontoc, Southern Leyte.

10 Conclusion Seven species of seagrasses were observed in the selected intertidal areas of Bontoc, Southern Leyte and these were Enhalus acoroides, Halophila minor and H. ovalis of family Hydrocharitaceae and Cymodocea rotundata, C. serrulata, Halodule pinifolia and H. uninervis of family Cymodoceaceae. The highest number of species was recorded in Talisay, where six of the seven species of seagrasses were observed. Among the seven seagrasses found in Bontoc, only H. minor was absent in Talisay. The lowest number of species encountered was in Casao, wherein only H. ovalis was seen. The most extensive seagrass bed in Bontoc was found in Union while the narrowest was identified to be in Casao. However, the seagrass beds of Bontoc were relatively diverse but they are classified as disturbed areas since it is located near human settlements. Furthermore, the areas showed physical disturbance and pollution. 5.0 References Cited Bjork M, Short F, Mcleod E, Beer S Managing seagrasses for resilience to climate change. Gland, Switzerland: International Union for Conservation of Nature. p. 56. Calumpong H, Meñez E Seagrass beds of the Philippines. Ann Trop Res. 16(1):1-15. Deguit E, Smith R, Jatulan W, White AT Participatory coastal resource assessment training guide. Cebu: Coastal Resource Management Project, Department of Environment and Natural Resources. English S, Wilkinson C, Baker V Survey manual for tropical marine resources. 2nd ed. Australia: Australian Institute of Marine Science. p Espinas IM, Espiritu R, Gultiano W, Lausa, J Status of marine fisheries in Bontoc, Southern Leyte. [BS thesis]. [Bontoc, Southern Leyte]:Southern Leyte State University-Bontoc. Fortes MD Wetland conservation and management in the Philippines. In: Wong MH, editor. Wetlands ecosystems in Asia: Function and management. Oxford: Elsevier. p Fortes M, Santos K Seagrass ecosystem of the Philippines: status, problems and management directions. In: Turbulent seas: the status of Philippine marine fisheries.

11 103 Cebu City, Philippines, Coastal Resource Management Project of the Department of Natural Resources, p Greve T, Binzer T Which factors regulate seagrass growth and distribution? In: Borum J, Duarte CM, Krause -Jensen D, Greve TM, editors. European seagrasses: an introduction to monitoring and management. The Monitoring and Management of European Beds Project p Fisheries Hokkaido University. 21(2): Salita J, Ekau W, Saint-Paul U Field evidence on the influence of seagrass landscapes on fish abundance in Bolinao, Northern Philippines. Mar Ecol Prog Ser. 247: UNESCO An ecological assessment of Ulugan Bay, Palawan, Philippines. Paris: UNESCO. p. 46. McKenzie L., Campbell S, Roder, C Seagrass-watch: manual for mapping and monitoring seagrass resources by community (citizen) volunteers. 2nd ed. Australia: Queensland Department of Primary Industries. Meñez E, Phillips R, Calumpong H Seagrasses from the Philippines. Washington: Smithsonian Institution Press. Phillips RC, Meñez EG Seagrasses. Washington DC: Smithsonian Contributions to the Marine Sciences. Saito Y, Atobe S.1974 June. Phytosociological study of intertidal marine algae. Bulletin of the Faculty of