Philippine Journal of Science 150 (S1): 383-394, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 20 Aug 2020

Distribution and Abundance of Seagrasses in the Southwest Coast of Oriental,

Neil C. Capin, Brian L. Pototan, Aileen Grace D. Delima, and Annabelle U. Novero*

Department of Biological Sciences and Environmental Studies College of Science and Mathematics, University of the Philippines Mindanao Mintal, Tugbok District, 8022 Philippines

Seagrasses are an important coastal resource that serves as homes and breeding grounds of fishes and other marine organisms and are useful indicators for the detection of changes in the coastal environment since they are vulnerable to bio-physical stressors. This study assessed the seagrass resources in terms of composition, percent cover, community similarity, and diversity in four municipalities (, , , and San Isidro) situated in the southwest coast of province facing . Thirty-six (36) transects, each with ten quadrats arranged in an alternate manner, were laid perpendicular to shore yielding a total of 360 plots. A total of eight seagrass species were observed: Cymodocea rotundata, Enhalus acoroides, Halodule pinifolia, Halophila minor, Halophila ovalis, Halophila spinulosa, Syringodium isoetifolium, and Thalassia hemprichii. Governor Generoso (33.77%) and San Isidro (26.01%) were classified to have fair seagrass bed conditions while Banaybanay (24.31%) and Lupon with the lowest coverage (15.90%) had poor status. T. hemprichii dominated the seagrass community in Banaybanay and Governor Generoso while C. rotundata were dominant in Lupon and San Isidro. The two most abundant species, T. hemprichii (41%) and C. rotundata (34.48%), had fair coverage comprising 75% of the entire seagrass while the remaining 25% cover was shared by Enhalus acoroides (19%) and other five species with very poor cover (0.30–2.43%). Diversity analysis using percent cover data revealed low diversity with overall Shannon index, H’= 1.2955, evenness J = 0.6657, and Simpson’s index of diversity, D = 0.3577. Dice community of coefficient grouped Banaybanay, Governor Generoso, and San Isidro together, indicating high similarities while separating Lupon, which had the poorest seagrass condition in terms of coverage. The status of seagrass diversity on the southwest coast of Davao Oriental calls for immediate attention and effective strategies to alleviate poor conditions and protect the seagrass beds.

Keywords: Cymodocea rotundata, Davao Oriental, diversity, seagrass cover, seagrass management, Thalassia hemprichii

INTRODUCTION an ecotone between a mangrove forest and coral reefs as well as a home of many marine organisms (Fortes 2013). Seagrasses are flowering plants that usually grow best Seagrasses serve as breeding and nursery grounds for in high-reducing sediments of shallow tropical and fishes and other marine organisms (Noel et al. 2012; subtropical locations in coastal communities, serving as Jumawan et al. 2015). They are also an important food *Corresponding Author: [email protected] source for sea cows (“dugong”) and sea turtles (Alcala

383 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental et al. 2008; Vinson et al. 2016). Further, they aid in the and Campbell 2002). Lack of knowledge and information stabilization of sediments in the ocean floor (Vinson et al. about the importance of seagrasses leads to the destruction 2016) and play an important role in the carbon cycle and of the resource (McKenzie and Campbell 2002; Jumawan nutrient cycle in coastal habitats (Redondo et al. 2017). et al. 2015). This study determined the composition of seagrass, the extent of seagrass cover, distribution, The Philippines has been noted to have the second most diversity index, and community similarity to assess the numerous taxa of seagrasses with 16 species (Fortes 1990) condition of the seagrass beds in four municipalities next to Australia with 19 species (Carruthers et al. 2007). situated in the southwestern portion of Davao Oriental However, conditions of seagrasses in the country face a facing Davao Gulf. Results of the study could help the serious threat (Dedel et al. 2018). There are pieces of local policymakers and stakeholders to improve the evidence that seagrasses are also declining globally (Björk communities’ understanding of the status of their seagrass et al. 2008). This is because seagrasses are susceptible beds and help them better conserve and manage these to changes in water quality and environmental quality coastal resources. (Vinson et al. 2016). This characteristic turns seagrass communities into useful indicators of changes in the coastal environment since it is vulnerable to biological and physical inconstancy, which is not easily observable MATERIALS AND METHODS in either coral reef or mangrove forest (Fortes 2013). Because these ecosystems are linked with each other, the instability of one system affects the other; thus, the Study Area destruction of seagrass beds has a great impact on our This study was conducted in the southwest portion in the marine environment (Jumawan et al. 2015). province of Davao Oriental, Philippines located between 62°00’ and 71°00’N latitude and 125°00’ and 126°00’E In the , there is still a large area where the longitude. This portion of the province facing Davao existence of seagrasses remains unknown – particularly Gulf is composed of four coastal municipalities (https:// surrounding the Davao Gulf, which is one of the country’s davaooriental.gov.ph): Banaybanay, Lupon, San Isidro, marine key biodiversity areas (CI et al. 2009). According and Governor Generoso. Banaybanay has a marine reserve to Alcala et al. (2008), the Department of Environment in Burias Islet; Lupon has reported sightings of hawksbill-, and Natural Resources has established marine protected green-, and leatherback turtles (Alcala et al. 2008); San areas (MPAs) along the shore of Davao Gulf that is Isidro has fish sanctuaries (https://davaooriental.gov. mostly composed of seagrass beds. However, there are ph), and Governor Generoso had sightings of dugong limited published seagrass monitoring surveys available (Lucero 2010). These marine animals are dependent on the (Noel et al. 2012; Jumawan et al. 2015). One of the available source of seagrass species used as food (Alcala reasons for limited information on seagrasses is that et al. 2008). Three sampling sites each were selected in the research tends to focus mainly on coastal resources with municipalities of Governor Generoso, San Isidro, Lupon, immediate economic value (Fortes 2013). Nevertheless, and Banaybanay (Figure 1). the importance of seagrasses in the marine waters of the Davao Gulf is highly recognized in their roles as We relied on local knowledge and Landsat imagery to locate feeding and nursery grounds to various species of fishes, seagrass beds. Purposive sampling was used, a non-random macroinvertebrates, and marine animals. Lucero (2010) technique that did not need underlying theories or a set reported that dugongs (Dugong dugon) visiting Davao number of informants (Tongco 2007). In every municipality, Gulf feed mostly on Halophila species. Noel et al. (2012) the seagrass covers were categorized into three – dense (D), also identified 13 fish species and 20 macroinvertebrate semi-dense (SD), and sparse (S) – wherein three 100-m species in seagrass beds in three municipalities in Davao transects were established for every category (Figure 2). Gulf. Among five provinces sharing the waters of the The three categories were identified to select priority sites Davao Gulf, the province of Davao Oriental possessed to represent the study area. Through key informants from the longest coastline in the country of about 3% (Cabrera the local fisherfolks and “” (hamlet) committee on and Lee 2020). With the observed coastal developments, agriculture, the three seagrass categories were identified. particularly in the southwestern portion of this coastline The site was visited only once. The following barangays facing the Davao Gulf, it is vital to assess the status of were sampled for each municipality: Maputi (D, SD) and seagrass beds. Kalubihan (S) in Banaybanay; Bagumbayan (S, SD, D) in Lupon; Baon (D), Bato-Bato (SD), and Cambaleon (S) Monitoring of seagrasses is very important to know the in San Isidro; and Lavigan (D, S) and Pundagitan (SD) in condition of the resource whether it is stable, declining, Governor Generoso. Each municipality consisted of nine or improving. Monitoring also is important in identifying transects, yielding a total of 36 transects. One hundred-meter areas that are in need of conservation measures (McKenzie (100-m) transect lines were established (nine transects per

384 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

Figure 1. Location of the seagrass sampling areas in Davao Oriental, Philippines (Governor Generoso, San Isidro, Lupon, and Banaybanay) located at 62°00’ and 71°00’N latitude and 125°00’ and 126°00’E longitude.

Figure 2. Categories of sampling for seagrass cover based on key informant interview in southwest coast of Davao Oriental, Philippines: A) dense, B) semi-dense, and, C) sparse.

site) from the coastline where the seagrass occurred to the 1990, 2013). The complete names of the species were seaward side, following the method Jumawan et al. (2015) based on the World Register of Marine Species (WoRMS with modifications. In Jumawan’s study, seagrass cover 2020). The conservation status of the recorded seagrass was considered as a single area whereas in our study, the species was determined based on the International Union seagrass cover was segregated into three (D, SD, and S). for Conservation of Nature (IUCN) 2010-3 (Short and Between transects, there was at least an interval distance Waycott 2010). of 50 m. Ten quadrats were laid at 10-m intervals in each transect. Seagrass Percent Cover The percent cover was estimated for each species within Seagrass Identification each quadrat via scoring following the method of Saito Seagrass species freshly collected on-site were examined and Atobe (1970). The method developed by Saito and and then identified down to the lowest taxonomic level Atobe (1970) is non-destructive because there is no using available field guides (Meñez et al. 1983; Fortes removal of biomass. It combines the transect and quadrat

385 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental sampling methodologies, in which there is mapping of the Community Similarity vegetation along the inter-tidal to sub-tidal zones and the A hierarchical cluster in single linkage analysis computed quantitative estimation of vegetation cover to determine by the Dice coefficient of community using PAST version distribution pattern. It is also ideal in areas where there 3.0 was generated to interpret community similarity based are distinct changes in vegetation patterns and marked on species similarity in four municipalities in Davao environmental gradients, particularly from the landward Oriental. side towards the edge of the reef (Ogawa et al. 2011). For the percent cover computation of each species per Diversity Index quadrat, the formula of Saito and Atobe (1970) adapted In the study of Jumawan et al. (2015) and Abubakar and by English et al. (1994) was used (Table 1). The scoring Echem (2018), seagrass cover was utilized in lieu of of a 50 x 50 cm quadrat subdivided into 25 sections of individual counts in the analysis of diversity. In Shannon- 10 x 10 cm follows the classes of dominance. A score of Wiener index of diversity: “5” means that 50–100% of the surface of the substratum is covered by the seagrass. This is the highest score of (2) the six classes. A score of “0” means the substratum had no seagrass present. Each class has also an equivalent midpoint value. Then, the coverage (C) of each species in where pi = ni/N used the fraction of percent cover per each 50 x 50 cm quadrat is computed using the following species (ni) over total percent cover of all seagrass species formula: per study site (N). Pielou’s index of evenness, where lnS is the natural logarithm of species richness, was used: (1) (3) where: Mi is the midpoint percentage of class i and f is the frequency or the number of sectors with the same class For Simpson’s index of diversity, the same calculation of dominance (i). Then, the total cover for each species for pi using cover was used. In other plant communities, for all transects per study site was summed. The relative percent cover abundance was also utilized in diversity percent cover of each species was obtained by dividing analysis using Simpson’s index (Sikkink et al. 2013): the total percent cover of each species over the sum of percent cover of all species for all the study sites. The (4) proportion of percent cover for each municipality was then calculated by adding the relative percent cover of all species present in the municipality. The means of seagrass percent cover of all transects per municipality were tested for the difference using analysis of variance at a 95% RESULTS confidence level in PAST version 3.0. The seagrass cover condition was categorized using the method of Amran Species Composition and Distribution (2010) with five scales for coverage image: scale 5 with Eight species were recorded in four municipalities > 75.4% as “very good”; 4 with 50.5–75.4% as “good”; in the southwest portion of Davao Oriental. The 3 with 25.5–50.4% as “rather good”; 2 with 5.5–25.4% species identified were Cymodocea rotundata, Enhalus as “bad” and < 5.5% as “very bad.” acoroides, Halodule pinifolia, Halophila minor, Halophila ovalis, Halophila spinulosa, Syringodium

Table 1. Classes of dominance used to record cover (lifted from English et al. 1994). Class Amount of substratum covered % substratum covered Midpoint % (M) 5 ½ to all 50–100 75 4 ¼ to ½ 25–50 37.5 3 1/8 to ¼ 12.5–25 18.75 2 1/16 to 1/8 6.25–12.5 9.38 1 Less than 1/16 < 6.25 3.13 0 Absent 0 0

386 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

isoetifolium, and Thalassia hemprichii. These species human disturbances such as the docking point for the belong to Cymodoceaceae and Hydrocharitaceae and local fishermen’s canoes and motorized boats. Thalassia were classified as “Least Concern” in the IUCN Report hemprichii (18.06%) dominates the seagrass bed in this 2010 (Table 2). In total, seven species were observed in municipality while S. isoetifolium has the least percent the municipalities of Banaybanay and San Isidro while cover (0.33%). six species were observed in municipalities of Governor Generoso and Lupon (Table 3). On the other hand, the survey sites in Banaybanay, Lupon, and San Isidro were observed to contain varied substrates. Likewise, T. hemprichii has the highest relative cover of Seagrass Percent Cover per Municipality 15.25% in Banaybanay. T. hemprichii was observed in Among the four coastal municipalities, Governor Generoso areas with coral debris adjacent to coral reefs together with had the highest seagrass cover of 33.77%, followed by San several species of seaweeds and macroalgae. Meanwhile, Isidro with 26.01%, Banaybanay with 24.31%, and lastly C. rotundata is commonly present on muddy clay and Lupon with the lowest seagrass cover of 15.90% (Figure dominating the seagrass beds in San Isidro and Lupon 3). However, there were no significant differences found with a relative cover of 14.39% and 12.22%, respectively. among means for percent cover between municipalities These muddy areas were situated next to mangrove (p = 0.1086). The seagrasses in Governor Generoso were forests, which are mainly situated at the river mouths found in areas with muddy clay substrates within a lagoon locally known as “bukana.” Species with poor relative that were usually left with low water level during low tide. cover are H. spinulosa in both Banaybanay (0.11%) and The seagrasses when not exposed to waves are prone to Lupon (0.07%) and H. minor in San Isidro (0.07%).

Table 2. List of seagrass species identified in the four selected coastal communities of Davao Oriental and their IUCN conservation status (LC – Least Concern). Family Species IUCN conservation status Cymodoceaceae Cymodocea rotundata Ascherson & Schweinfurth, 1870 LC Halodule pinifolia (Miki) Hartog, 1964 LC Syringodium isoetifolium Ascherson (Dandy), 1939 LC Hydrocharitaceae Enhalus acoroides (Linnaeus f.) Royle, 1839 LC Halophila minor (Zollinger) Hartog, 1957 LC Halophila ovalis (R.Brown) J.D.Hooker, 1858 LC Halophila spinulosa (R.Brown) Ascherson, 1875 LC Thalassia hemprichii (Ehrenberg) Ascherson, 1871 LC

Table 3. Seagrass composition in the study sites belonging to four municipalities in the southwest coast in the province of Davao Oriental, Philippines. Seagrass species

Sites

Cymodocea Enhalus Halodule Halophila Halophila Halophila Syringodium Thalassia rotundata acoroides pinifolia minor ovalis spinulosa isoetifolium hemprichii Banaybanay        Governor       Generoso Lupon       San Isidro       

387 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

Figure 3. Proportion of seagrass percent cover in four coastal municipalities in southwest part of Davao Oriental facing Davao Gulf, Philippines.

In these study sites, we observed that seagrass species The third abundant species was E. acoroides that accounted grew abundantly in areas that are part of the area’s MPA. for only about 19% in the total seagrass cover. Species of There were fewer activities observed in these areas due E. acoroides thrive in areas with murky waters, muddy to the presence of “Bantay Dagat” personnel, whose main substrates usually found in the mouth of the river. These duty is to patrol and impose local ordinances pertaining areas are also favorite sites for mangrove planting activities to the management of coastal resources. Most of the threatening the existence of seagrass habitats. Lastly, the apprehensions were brought about by “karas” or scraping remaining 6% seagrass cover was shared by five species, the seagrass vegetation to harvest the seashells that thrive with H. minor having the lowest seagrass cover. in the area. Another factor is the more frequent patrolling activities of maritime authorities in specific locations of Community Similarity the said municipalities. Seagrass communities in municipalities of San Isidro, Governor Generoso, and Banaybanay were clustered Relative Percent Cover per Species together showing high similarity (92.31%) than that of In terms of the relative coverage per species, about Lupon (76.92%), as shown in Figure 5. Six seagrass 41% of the overall seagrass cover was dominated by species were commonly found in clustered municipalities T. hemprichii (Figure 4) being the highest and most – which are C. rotundata, E. acoroides, H. pinifolia, H. abundant in two municipalities (Governor Generoso and ovalis, S. isoetifolium, and T. hemprichii. Meanwhile, only Banaybanay). T. hemprichii was the dominant seagrass four species in Lupon were commonly found across sites species and grew abundantly on dead reef platforms that included C. rotundata, H. pinifolia, S. isoetifolium, and in bottom sediments composed of coral sand and and T. hemprichii. coral rubble. The second most abundant was C. rotundata with 34.48% Diversity Indices cover that dominated the two other municipalities (San Diversity and evenness showed that sampled seagrass Isidro and Lupon). We observed that C. rotundata in beds in Governor Generoso was the most diverse (H’ = Governor Generoso was subjected to constant human 1.100) and had the highest evenness (J = 0.6570) using activities because it thrived in shallow areas attributing percentage cover in the analysis, as shown in Table 4. to its low cover in the area. Canoes and motorized boats These indices were highly influenced by the high percent of local fisherman docks on the shallow part of the shore cover of seagrasses present in Governor Generoso despite during low tide. Most of the area where C. rotundata involving only six out of eight species. For both diversity occurred was also where mangrove planting activities and evenness, Banaybanay ranked second, followed by were observed. Rhizophora species were planted, causing San Isidro, with Lupon as the least diverse. For Simpson’s high disturbance of C. rotundata’s natural habitat. index of diversity, a more similar trend with that of total

388 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

Figure 4. Relative percent cover of eight seagrass species recorded in four municipalities in Davao Oriental, Philippines.

Figure 5. Community similarity according to Dice coefficient in single linkage analysis across four seagrass sampling sites in Davao Oriental, Philippines.

389 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

Table 4. Seagrass diversity in four coastal municipalities in southwestern part of Davao Oriental facing Davao Gulf, Philippines. Indices Banaybanay Lupon San Isidro Governor Generoso Overall Species richness 7 6 7 6 8 Shannon-Wiener index of diversity 1.1005 0.8443 1.0930 1.1773 1.2955 Hmax 1.9459 1.7917 1.9459 1.7917 2.0794 Pielou’s index of evenness 0.5655 0.4712 0.5617 0.6570 0.6230 Simpson’s index of diversity 0.5497 0.3926 0.6026 0.6234 0.3577

percent cover was observed from Governor Generoso, Based on categories made by Amran (2010) on the San Isidro, Banaybanay, and Lupon from highest to condition of seagrass beds, the municipalities of San Isidro lowest ranks. A little difference between Shannon and and Governor Generoso had rather good or fair seagrass Simpson’s indices between Banaybanay and San Isidro beds (scale 3: 25.5–50.4%), while Banaybanay and Lupon was noted, which could be attributed to the percent had bad or poor status (scale 2: 5.5–25.4%). Governor cover of different dominant species per study site, i.e. T. Generoso had higher seagrass coverage than that of hemprichii in Banaybanay and C. rotundata in San Isidro. Hagonoy, (Jumawan et al. 2015). Similarly, Overall, the seagrass Shannon index (H’ = 1.2955) as T. hemprichii was also the most abundant in Hagonoy, well as Simpson’s index of diversity (D = 0.3577) were Davao del Sur along with C. rotundata (Jumawan et al. low, which can be influenced by the dominance of certain 2015). In contrast, Noel et al. (2012) reported that in species of seagrass per study site. Governor Generoso, Cymodocea species had the highest cover while Thalassia had the least. The disparity could be mainly due to the different locations of seagrass surveys aside from the time difference between the studies. The DISCUSSION sampling map of the previous study showed Don Chicote, Jamboree in Barangay Nangan and Lawis in Barangay According to Fortes (2013), there were eighteen known Tibanban areas, while this study specifically assessed seagrass species in the Philippines. Davao Oriental seagrass beds in two barangays – Lavigan and Pundagitan. seagrasses accounted for 44.44% of the recorded In Tawi-Tawi, T. hemprichii (56.59%) was the most Philippines seagrass species. According to Alcala et al. abundant, suggesting dominating capability preventing (2008), areas with good seagrass meadows harbored more the growth of other species (Abubakar and Echem 2018). than 10 seagrass species. At the local level, however, this Thalassia hemprichii was also found growing with S. northeastern portion of Davao Gulf comprises 50% of the isoetifolium, C. rotundata, E. acoroides, and H. ovalis previously recorded 14 seagrass species in selected sites in the mostly mud-coral sand or coarse coral sand area, in Davao Gulf based on the study of Noel et al. (2012). as similarly noted by Meñez et al. (1983). Though T. In the study of Jumawan et al. (2015) on seagrasses in hemprichii reportedly thrived in Governor Generoso Hagonoy, Davao del Sur, two species outside the transect because the area had mud-coral sand or coarse coral sand lines were included in their species composition, resulting substrate (Meñez et al. 1983), this may not necessarily be in seven species. However, in our study, only species the case for all T. hemprichii sightings. There are other within the transect plots were recorded. Apparently, some factors affecting this species such as tolerance to a wide species may have been missed out during the single visit. range of temperatures (Fortes 2013). Tupan and Uneputty In this study, H. spinulosa and E. acoroides were newly (2018) found that the growth of T. hemprichii was strongly recorded; however, Halodule uninervis and Cymodocea positively affected by high nitrate and phosphate in the serrulata in the previous study (Noel et al. 2012) were water and sediments. not sampled. The differences in the species distribution in the study area could be connected to the physical Although Banaybanay and San Isidro have the highest characteristics of the study sites. According to Meode et species richness, they are affected by environmental al. (2014), the substratum is a very important regulator of pressures that influence the seagrass bed conditions such seagrass distribution. Moreover, predation and associated as the construction of seawall, coastal road, and cutting biota are the other factors that influence the distribution and clearing of mangroves to create aquaculture ponds for of seagrass (Wahab et al. 2017). The adaptability of “bangus” (Chanos chanos) and Nile tilapia (Oreochromis seagrasses to environmental conditions is very different niloticus). According to Primavera (1991), coastal from one species to another (Wahab et al. 2017). developments such as mangrove conversion into ponds affect the neighboring ecosystems by causing salt intrusion

390 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental and vulnerability to floods. These could lead to social so common component of shallow seagrass beds. In Tawi- costs such as reduced water supplies and decreased fish Tawi, H. pinifolia has the smallest cover and its rarity is and food crop production, which may further marginalize attributed to sensitivity to oceanic changes (Abubakar fisher folk. Fortes et al. (2016) reported that developments and Echem 2018). in the coastal areas of the country have a huge impact on marine ecosystems such as seagrass meadows. The In summary, this pattern in percentage cover reported disturbances created accelerate the degradation of the in our study is typical of seagrass beds found in the ecosystems. Coastal construction and reclamation Philippines and other places in Asia with sandy-muddy- dredging, for instance, alter the water flow. This causes coral rubble substrates. The occurrence of these dominant physical changes and shading of waterways affecting species, T. hemprichii and C. rotundata, conforms with seagrass beds. Structures like seawalls and the like can Noel et al. (2012) in that they had relatively similar dramatically change the water movement or hydrology abundance with other areas surveyed in Davao Gulf of a water body, causing eutrophication and algal bloom. (Jumawan et al. 2015) and other areas in Mindanao such Reclamation and dredging not only physically remove and as in Tawi-Tawi (Abubakar and Echem 2018). In addition, destroy seagrass beds but degrade and alter substrates as other species with a low cover were found thriving along well as decrease the recreational and economic quality with these dominant species. Paz-Alberto et al. (2015) of water by increasing turbidity and sedimentation. reported that three species of seagrass were abundant in Furthermore, the seagrass coverage area of Lupon is small Candelaria, Zambales. These were C. rotundata (smooth because the seawall cover is high and blocks the seagrass ribbon seagrass), T. hemprichii (sickle seagrass), and S. cover. Sand tends to cover the seagrass area during the isoetifolium (noodle seagrass). A seagrass survey in Sabah, “habagat” season, which is why a long and tall seawall Malaysia reported the dominance of C. rotundata and H. cover was previously constructed. uninervis in a zone characterized by the predominance of fine sand, which was sometimes overlaid with soft These two species, T. hemprichii and C. rotundata, were to compacted mud (Ismail 1993). In Indonesia, the categorized under fair condition (Amran 2010). The seagrass species commonly found on muddy, sandy, growth of C. rotundata was found to be favorable in the coral rubble, and mixed substrate were T. hemprichii, four selected areas of Davao Oriental province because Enhalus acoroides, Halophila ovalis, Halodule pinifolia, of the shallow water and sand-mud or sand substrate near H. uninervis, C. rotundata, and Thalassodendron ciliatum river mouths and coral reefs. According to Meñez et al. (Nontji et al. 2012). (1983), C. rotundata occurred in shallow water, on sand- mud, or sand substrates in bays, lagoons, river mouths, In comparison with neighboring areas surrounding Davao and in coral reef areas – making the species suitable in Gulf, the Shannon indices for these sampled municipalities the coastal environment of Lupon and San Isidro where are higher than seagrass diversity in Hagonoy, Davao del the area had a muddy to sandy substrate. The dominance Sur with H’ = 0.30919 (Jumawan et al. 2015). According of C. rotundata due to the substrate in the form of sand- to the categories of Odum (1983) as cited in Abubakar and mud and rubble was scattered in the area (Wahab et al. Echem (2018), the sampled seagrass beds in this portion 2017). In addition, C. rotundata may be found growing of Davao Oriental had a low Shannon index of diversity with E. acoroides, H. ovalis, Halodule uninervis, S. (H’ < 2.0). In comparison with another surveyed seagrass isoetifolium, T. hemprichii, or Cymodocea serrulata area in Mindanao, this area although with higher species (Meñez et al. 1983). The third most abundant species is E. richness has a much lower Shannon index (H = 1.296) acoroides, which was the largest species. It has a massive than in Bongao, Tawi-Tawi with seven species and H’ = rhizome which thrives together with T. hemprichii (Rollon 1.653. Both sites are categorized as having low diversity 1998) but is slow growing and sensitive to ecosystem but differ in coverage. This further implies the degradation perturbations (Short and Waycott 2010). The remaining of seagrass conditions in Lupon and Banaybanay due to 6% of seagrass cover was comprised mostly of Halophila poor seagrass cover and low diversity, leading to low species with low cover categorized from poor to very poor community stability (Abubakar and Echem 2018). This condition. Amran (2010) also reported H. minor in very condition can be attributed to environmental pressures poor condition due to its very small cover. These species and threats observed in the area. Meanwhile, the other two have different characteristics – H. minor seems to prefer municipalities in San Isidro and Governor Generoso have muddy bottoms and tolerate sedimentation found in the a rather good seagrass cover with poor to fair conditions deep bay that is well-protected from wave action while of seagrass species. However, seagrass resources in H. spinulosa occurs on sand, mud, or coral rubble in these areas are also threatened with human activities the sub-littoral zone (Meñez et al. 1983). Largo (1987) despite the monitoring of “Bantay Dagat” personnel. The reported that H. spinulosa was found more than 10 m disproportion in the number of “Bantay Dagat” personnel deep in waters between Bohol and Cebu, making it a not to the long shoreline of Governor Generoso creates a

391 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental greater chance of occurrence of illegal activities. Due REFERENCES to human activities and natural disturbances, seagrass resources undergo deprivation (Dedel et al. 2018). ABUBAKAR FZB, ECHEM RT. 2018. Distribution and Seagrass communities are not only exploited for fishing abundance of seagrass in Bongao, Tawi-Tawi. World but they are also prone to developmental purposes (Meode J. Pharm. Life Sci. 4(7): 17–21. et al. 2014). This is true for the case of the southwestern ALCALA AC, INGLES JA, BUCOL AA. 2008. Review coast of Davao Oriental, wherein the construction of a of the biodiversity of Southern Philippine seas. Philipp coastal road and sea wall has caused the decline in the Sci 45: 1–61. doi: 10.3860/psci.v45i0.991 seagrass population based on actual interviews with locals AMRAN MA. 2010. Estimation of seagrass coverage in the area. by depth invariant indices on quickboard imagery. BIOTROPIA. 17(1): 42–50. BJÖRK M, SHORT F, MCLEOD E, BEER S. 2008. CONCLUSION Managing Seagrasses for Resilience to Climate Change IUCN Global Marine Programme, IUCN Resilience There are eight seagrass species representing two Science Group Working Paper Series. 56p. families: Cymodocea rotundata, Halodule pinifolia, and Syringodium isoetifolium of Family Cymodoceaceae; and CABRERA JS, LEE HS. 2020. Flood risk assessment for Enhalus acoroides, Halophila minor, Halophila ovalis, Davao Oriental in the Philippines using geographic Halophila spinulosa, and Thalassia hemprichii of Family information system-based multi-criteria analysis and Hydrocharitaceae found in the southwest coast of Davao the maximum entropy model. J Flood Risk Manag Oriental. This number falls below the minimum number e12607. https://doi.org/10.1111/jfr3.12607 of ten species that make up an ideal seagrass meadow, CARRUTHERS TJB, DENNISON WC, KENDRICK as per the literature. The two most dominant species GA, WAYCOTT M, WALKER DI, CAMBRIDGE ML. found were T. hemprichii and C. rotundata. The seagrass 2007. Seagrass of south-west Australia: a conceptual inventory conducted revealed low species diversity indices synthesis of the world’s most diverse and extensive sea- and poor- to fair- coverage, necessitating an immediate grass meadows. J Exp Mar Biol Ecol 350(1–3): 21–45. call for interventions to mitigate further coastal resource degradation in the southwestern coastline of Davao [CI] Conservation International Philippines, [DENR- Oriental. PAWB] Department of Environment and Natural Resources–Protected Areas and Wildlife Bureau, [DA-BFAR] Department of Agriculture–Bureau of Fisheries and Aquatic Resources. 2009. Priority Sites ACKNOWLEDGMENTS for Conservation in the Philippines: Marine and Ter- restrial Key Biodiversity Areas Map. Retrieved on 07 This study was funded by the Commission on Higher Dec 2020 from https://fpe.ph/biodiversity.html/view/ Education DARE-TO (Discovery-Applied Research and the-philippine-key-biodiversity-areas-kbas Extension for Trans/Inter-disciplinary Opportunities) Research Grant 2018–2020 under the project titled DEDEL JIC, CRESENCIO CC, AYATON MA, DELA- “Vulnerability Assessment of Coastal Areas in Davao BAHAN ICB, GAMALINDA EF, CALAGUI LB. Gulf to Climate Related Hazards” implemented by the 2018. Seagrass species distribution and coverage in University of the Philippines Mindanao and Davao Del the intertidal zones of Bucas Grande island, Surigao Norte State College. We would like also to acknowledge Del Norte. Int J Fis Int J Fish Aquat Stud 6(3): 59–62. the support of Hon. Adalia L. Tambuang, municipal ENGLISH S, WILKINSON C, BAKER V. 1994. Survey mayor of Banaybanay; Hon. Katrina Joy H. Orencia, Manual for Tropical Marine Resources. ASEAN– municipal mayor of Governor Generoso; Hon. Linda Lim, Australia Marine Science Project: Living Coastal municipal mayor of Lupon; and Hon. Justina MB. Yu, Resources. Australian International Development. p. municipal mayor of San Isidro – all in Davao Oriental. The 235–252. local government units’ respective offices of Municipal Agriculture, Planning, and Development plus barangay FORTES MD. 1990. Seagrasses: A Resource Unknown personnel and field technicians who facilitated our field in the ASEAN Region. ICLARM Educ Ser (5): 46. surveys are likewise acknowledged. Finally, we thank FORTES MD. 2013. A review: biodiversity, distribution Dr. Lea A. Jimenez and Dr. Emily S. Antonio of Davao and conservation of Philippine seagrasses. Philipp J Oriental State College of Science and Technology for Sci 142(3): 95–111. sharing their expertise on seagrass assessment.

392 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

FORTES MD, FORTES EG, SARCEDA MB, JIMENEZ ODUM EP. 1983. Basic Ecology. CBS College Publish- LA, LUCERO RS. 2016. Seagrasses: See How They ing, New York. In: Abubakar FZB, Echem RT. 2018. Protect Us. A Guide for Community Appreciation of Distribution and abundance of seagrass in Bongao, Seagrasses in the Philippines. Department of Science Tawi-Tawi. World J Pharm Life Sci 4(7): 17–21. and Technology, Asia-Pacific Network for Global OGAWA H, SIDIK JB, HARAH MZ. 2011. Seagrasses: Change Research, National Council of the Philippines, Resources Status and Trends in Indonesia, Japan, U.P. Marine Science of Institute CS, Quezon City, Malaysia, Thailand and Vietnam. Japan Society for Philippines. 43p. the Promotion of Science (JSPS) and Atmosphere and [IUCN] International Union for Conservation of Nature. Ocean Research Institute (AORI), The University of 2010. The IUCN Red List of Categories and Criteria. Tokyo. Tokyo: Seizando-Shoten Publishing Co. Ltd. Gland, Switzerland. PAZ-ALBERTO AM, PAKAIGUE-HECHANOVA M, ISMAIL N. 1993. Preliminary study of the seagrass flora SIGUA GC. 2015. Assessing diversity and phytore- of Sabah, Malaysia. Pertanika J Trop Agric Sci 16(2): mediation potential of seagrass in tropical region. Int 111–118. J Plant Anim Env Sci 5(4): 24–33. JUMAWAN J, BITALAS MB, RAMOS JJC, GARCIA PRIMAVERA J. 1991. Intensive prawn farming in the ARP, LANDERO RS, CORDERO JA, MATELA Philippines: ecological, social, and economic implica- MNV, APOSTOL MAD, CATALUÑA RB. 2015. tions. AMBIO: J Hum Env 20(1): 28–33. Seagrass diversity and structure along the coastal area REDONDO AFS, DAGOC KMF, IGNACIO MTT, SAN- in Paligue, Hagonoy, Davao del Sur, Philippines. AES CHEZ RRG, TAMPUS AD. 2017. Seagrass mapping Bioflux 7(3): 351–356. and assessment using remote sensing in the Munici- LARGO DB. 1987. The Halophila spinulosa (R. Brown) pality of Kauswagan, Lanao del Norte, Philippines. J Ascherson: a new seagrass record for the Visayan Biodiv Env Sci 11(4): 74–88. waters. Philipp Sci 24: 1–4. ROLLON RN. 1998. Spatial variation and seasonality in LUCERO RS. 2010. Population estimate and foraging growth and reproduction of Enhalus acoroides (L.f.) niche of Dugong (Dugong dugon) in Davao Gulf. Royle populations in the coastal waters off Cape Bo- Proceedings of the 5th International Symposium on linao, NW Philippines [Dissertation]. A.A. Balkema, SEASTAR2000 and Asian Bio-logging Science (the Rotterdam. Netherlands. 134p. 9th SEASTAR2000 workshop). p. 59–62. SAITO Y, ATOBE S. 1970. Phytosociological study of MCKENZIE LJ, CAMPBELL SJ. 2002. Manual for intertidal marine algae. In: Survey Manual for Tropical Community (citizen) Monitoring of Seagrass Habitat Marine Resources. English S, Wilkinson C, Baker V Western Pacific Edition. Department of Primary In- eds. ASEAN-Australia Marine Science Project: Living dustries, Queensland, Australia. Coastal Resources. Australian International Develop- ment. p. 235–252. MEÑEZ EG, PHILIPS RC, CALUMPONG HP. 1983. Seagrasses from the Philippines. Smithsonian Contri- SHORT FT, WAYCOTT M. 2010. Enhalus acoroides. The butions to the Marine Sciences No. 21. IUCN Red List of Threatened Species 2010. Retrieved on 23 Dec 2020 from https://dx.doi.org/10.2305/IUCN. MEODE ML, MONTES EB, PALOMA AQ, PANAL UK.2010-3.RLTS.T173331A6992567.en MEN, PESQUERA NM. 2014. Distribution and abun- dance of seagrasses of Bontoc, Southern Leyte. J Sci SIKKINK PG, RENKIN R, CHONG G, SIKKINK A. Eng Technol 2: 93–103. 2013. Assessing five field sampling methods to monitor Yellowstone National Park's northern ungulate winter NOEL HW, LUCERO RS, SATURNINO CP, LABIS PY, range: the advantages and disadvantages of implement- LUCERO MJ. 2012. Productivity and Distribution of ing new sampling protocol. In: Final Report: Assessing Seagrass Communities in Davao Gulf. Proceedings of Sampling Methods YNP 2013. 41p. Retrieved on 21 the 7th International Symposium on SEASTAR2000 Dec 2020 from https://www.fs.usda.gov/treesearch/ and Asian Bio-logging Science (The 11th SEAST- pubs/44773 AR2000 workshop). p. 59–63. THE OFFICIAL WEBSITE OF THE PROVINCE OF NONTJI A, KURIANDEWA TE, HARRYADIE E. 2012. DAVAO ORIENTAL. Davao Oriental Fun Map. Re- National review of dugong and seagrass: Indonesia. trieved on 23 Dec 2020 from https://davaooriental.gov. GEF/UNEP Project on the Dugong And Seagrass ph/tourism-4/explore-davao-oriental/ Conservation. 36p.

393 Philippine Journal of Science Capin et al.: Distribution and Abundance of Seagrasses Vol. 150 No. S1, Special Issue on Biodiversity in Southwest Coast of Davao Oriental

TONGCO MDC. 2007. Purposive sampling as a tool for informant selection. Ethnobot Res Appl 5: 147–158. doi: 10.17348/era.5.0.147-158 TUPAN CI, UNEPUTTY PA. 2018. Growth and pro- duction of leaves of Thalassia hemprichii on the Suli coastal waters, Ambon Island. Int J Mar Eng Inn Res 2(20): 112–116. VINSON NS, ANTE SC, ROXAS RJFS, SALVIO SMC, RABE SLC, TORRES MAJ, CABRERA MLN, RE- QUIERION EA. 2016. Correlation between water quality and seagrass distribution along intertidal zone in Sarangani Province, Philippines. J Biodiv Env Sci 8(5): 2220–6663. WAHAB I, MADDUPA H, KAWAROE M. 2017. Seagrass species distribution, density and coverage at Panggang Island, Jakarta. OP Conference Se- ries: Earth and Environmental Science 54: 012084. doi:10.1088/1755-1315/54/1/012084 [WoRMS] World Register of Marine Species. 2020. Retrieved on 21 Dec 2020 from http://www.marine- species.org/

394