J. Bio. & Env. Sci. 2018 Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 14, No. 2, p. 53-62, 2018 http://www.innspub.net RESEARCH PAPER OPEN ACCESS Assessment of mangrove diversity in Santa Cruz, Davao Del Sur, Philippines Jayson Cardillo, Annabelle Novero* Department of Biological Sciences and Environmental Studies, College of Science and Mathematics, University of the Philippines Mindanao, Davao City, Philippines Article published on February 28, 2018 Key words: Mangrove, Biodiversity, Sonneratia alba, Santa cruz, Philippines. Abstract This study assessed the mangrove species in Santa Cruz, Davao del Sur, Philippines. Six sample plots were established and results of the assessment yielded 17 different species of mangroves in the area with one categorized as Vulnerable (Avicennia rumphiana). Abundance curve estimated uneven distribution of species. Diversity indices yielded dominance (0.159) and evenness (0.535) values that are relatively lower compared to values from other municipalities in the Davao region. Shannon index value of 2.2 was concluded to be higher than other mangrove assessment studies which suggest higher diversity in the area. Investigation of the mangrove community structure concluded that Sonneratia alba (importance percentage of 24%) is a keystone species of the mangrove forest and that it is the most acclimated to the environment of Santa Cruz. Assessment of mangrove diversity is crucial to restoration efforts that address the problems of deforestation brought about by man-made disturbances. *Corresponding Author: Annabelle Novero [email protected] 53 | Cardillo and Novero J. Bio. & Env. Sci. 2018 Introduction such as Philippines as both irreplaceable and Mangroves are revered as of the most important floras vulnerable (Margules and Pressy, 2000; Brooks et al., in the world. They are uniquely identified as a group of 2002). Based on the data collected by the Department plants that can easily adapt to their environment of Environment and Natural Resources-Forest (Warne, 2007). They thrive in the coastlines of tropical Management Bureau (DENR-FMB, 2013), there was a and sub-tropical countries which exposes them to significant decrease in the total forest cover of extreme environmental conditions such as high Philippines from 1934-2010. Recorded data for temperature and salinity (Kathiresan and Bingham, mangrove habitat area over the past decades also 2001). However, they have a specific ultrafiltration revealed a substantial loss of almost 75% (Primavera, system which enables them to survive that harsh 1995; Primavera, 2000; Samson and Rollon, 2008) intertidal zone. The Philippines has a rich mangrove which translates very significantly especially because diversity with 35 known true mangroves that thrive most Philippine villages are along or dependent on throughout the country (Long and Giri, 2011). coastal resources (Primavera, 2000). If this continues to worsen, habitat loss will result into loss of biodiversity Moreover, the Philippines is home to approximately which will soon affect specific ecosystem functions and 50% of the known mangrove species in the world and ultimately the society (Cardinale et al., 2012). this includes various endangered species, vulnerable and some threatened species (Primavera et al., 2004; Biological diversity assessment is an important tool in Spalding et al., 2010; Garcia et al., 2014). determining the current state of biodiversity in a location. Moreover, this determines how the ecosystem, Mangroves are often used for thatching, firewood, species and genetic diversity are affected by the charcoal and timber (Brown and Fischer, 1918; Spalding execution or the difference in implementation of et al., 1997; Long and Giri, 2011). Mangrove forests are development and rehabilitation strategies (International known habitats for epibenthic, infaunal and meiofaunal Union for Conservation of Nature Monitoring and invertebrates while supporting other smaller Evaluation Initiative and International Union for communities such as phytoplanktons and zooplanktons Conservation of Nature Biodiversity Policy and (Cañizares and Seronay, 2016). They are also proven to International Agreements Unit, 2000). This study be good nursing sites for marine juveniles (Rönnback, assessed the mangrove diversity of four sites in Sta. 1999; Long and Giri, 2011) which keep the population of Cruz, Davao del Sur, Philippines. marine animals stable considering that fishing is an important livelihood in Philippines. Moreover, Materials and methods mangroves are nesting grounds to hundreds of bird Study area species (Nagelkerken, 2008; Garcia et al., 2014). Mangrove assessment was performed in November Mangroves also play a significant role in coastal 2017 in Sta. Cruz, Davao del Sur, Philippines. protection as it helps prevent the erosion of Perpendicular from the shoreline, six plots were unconsolidated coastlines and eventual flooding (Food established randomly in four different villages and Agriculture Organization, 1994). (barangay) of Sta. Cruz, Davao del Sur (Fig.1). Plots 1 (6°50’36”N 123°25’03”E) and 2 (6°50’39”N The Philippines was identified as a biodiversity 125°25’02”E) were in Zone III, Barangay Miranda. hotspot since 1988 (Myers, 1988; Marchese, 2015). Plot 3 (6°48’49”N 125°23’51”E) was established in This means that while it has a particularly high Barangay Tuban. Plots 4 (6°47’21”N 125°23’26”E) and biodiversity rating, most of its species are very 5 (6°47’55”N 125°23’03”E) were in Barangay Bato. susceptible to extinction due to habitat loss Lastly, plot 6 was (6°48’18”N 125°22’44”E) in (forestlands, grasslands, mangroves) and other Barangay Tagabuli. The mangrove forests of Barangay ecological factors. This renders biodiversity hotspots Bato, Tagabuli and Tuban had an estimated total 54 | Cardillo and Novero J. Bio. & Env. Sci. 2018 Marine Protected Area (MPA) of 80 hectares. measuring a 10x10m square (English et al., 1997). Unfortunately, there was no size estimate for Each corner was designated by a 30.48-cm metal pin Barangay Miranda. The plots were fashioned by and the section was cordoned with hemp rope. Fig. 1. Mangrove sampling sites in Sta. Cruz, Davao del Sur, Philippines, 6°50' 13" North, 125° 24' 47" East. Species identification and measurement of diversity Where, parameters pi = abundance of ith species over total number of In order to identify the mangrove species inside the individuals across all species plots, the mangrove field guide by Primavera and S = species richness eH Dianala (2009) was used. Mangroves were identified Evenness = [3] Where: S through their fruits, flowers, leaves and overall H = Shannon Wiener Index structure. Height was measured through a laser S = species richness S rangefinder and diameter at breast height (DBH) was Shannon Wiener Index (H) = ∑푖=1 푝푖푙푛 푝푖 [4] measured through a tree caliper. Moreover, the conservation status of each mangrove species Where, pi = abundance of ith species over total number of identified was determined through the International individuals across all species Union for Conservation of Nature Red List data. S = species richness Data Analysis Species community structure analysis Diversity indices and abundance curves: To assess Relative density, relative frequency, relative the floral biodiversity of each location, species dominance and importance value (equations 5, 6, 7 richness, dominance, evenness and the Shannon and 8 respectively) were calculated for each site to Wiener diversity index (equations 1, 2, 3 and 4 analyze the community structure of the species respectively) were calculated for each site. The identified (Netto et al., 2015). Paleontological Statistical Software Package (PAST) developed by Hammer et al. (2001) was used in Relative density determines which species have the highest count per unit area. Relative frequency calculating said indices. Furthermore, a visual establishes which species occur most in the location. representation for species richness and evenness was Relative dominance identifies the species that presented by generating an abundance curve. constitutes the largest part of the biomass of the Species richness (S) = total number of taxa [1] mangrove area. Importance value designates which ∑푆 2 Dominance (D) = 푖=1 푝푖 [2] component species are relatively acclimated to Sta. 55 | Cardillo and Novero J. Bio. & Env. Sci. 2018 Cruz.Relative Density= Identification of mangroves in the six sampling plots Total number of individuals of a species throughout the five plots yielded species 17 species from 11 Families (Table 1). ( Total plot area ) *100 [5] Total density There are around 35 to 40 species of mangrove in the Relative Frequency= Philippines (Long and Giri, 2011). Our study recorded Total number of times species is present in the five plots ( ) *100 [6] 43% of the total known species in the country. This is Total plot frequency comparatively higher than results of other studies in Relative Dominance= the Davao Region. Pototan et al. (2017) inventoried Total area of a species throughout the five plots ( Total plot area ) *100 [7] 12 species (30%) from Carmen, 11 (27%) from Tagum Total basal area and 16 (40%) from Panabo, all in Davao del Norte. A Importance Value Percentage= study in Hagonoy, Davao del Sur also yielded a low Relative density + Relative frequency + Relative dominance [8] 3 number of 7 species (17%; Jumawan et al., 2015). Hence, it can be inferred that Sta. Cruz has high Results and discussion species richness compared