COVER VOL 7 copy JPAIR: Multidisciplinary Journal 106 Macrobenthic Composition of Sea Water Associated with Seagrass in East and West Portions of the Igang Bay, Nueva Valencia, Guimaras MARY JEAN L. DE LA CRUZ JUNE RAYMUND PETER FLORES MELCHOR M. MAGRAMO CHRISTY MADAS MARLON TERUNEZ JBLFMU-Arevalo, Ilo-ilo City, Philippines Abstract - The macrobenthic invertebrates are associated with seagrass communities in East and West at the Igang Bay, Nueva Valencia, Guimaras. Seven groups were found in West Igang which includes the hard coral, gastropod, bivalve, soft coral, starfish, limpet, hermit crab and cowrie while eight groups composed of bivalve, gastropod, snail, cowrie, hard coral, hermit crab and sponge were found in the seagrass community of East Igang. Results show that gastropod was the dominating group in both sites. The hard coral group was the most frequent to occur in West Igang while the gastropod in East Igang was frequently observed. Common groups in both sites were hard coral, gastropod, bivalve, and cowrie. West Igang had higher diversity of macrobenthos (H’ = 0.608) than the East Igang with (H’ = 0.513). Both sites have sandy, silty-muddy type of substrates although some portions of West Igang were rocky. Salinity ranged Vol. 7 · January 2012 Print ISSN 20123981 • Electronic ISSN 2244-0445 International Peer Reviewed Journal doi: http://dx.doi.org/10.7719/jpair.v7i1.156 JPAIR Multidisciplinary Journal International Peer Reviewed Journal 107 from 28 to 30 parts per thousand and temperature from 20.67 to 32.67 degrees Celsius. Water depth recorded ranged from 0.43 to 0.60 meters. The higher variability of substrates in West Igang probably promoted the higher diversity of macrobenthic groups in the area suitable for different attachments and mobility along with denser growth of seagrass in the said site. Keywords - Seagrass, Igang Bay, Macrobenthic invertebrates, hard corals, gastropod, bivalve INTRODUCTION Macrofauna or macrobenthos are the largest benthic animals associated with the marine water bottom sediment. Benthic animals are classified into three ecological categorie, viz., infauna and epifauna, based on where they thrive relative to the substrate. The infauna are those that live wholly or partly within the substrate which includes many clams and worms polychaetes as well as other invertebrates which usually dominate communities in soft substrates and are most diverse and abundant in subtidal regions. Few are found in hard substrate communities with rock-boring clams being one example. The epifauna are those animals living on or attached to the seafloor which encompass about 80% of the larger zoobenthos. Epifauna include corals, barnacles, mussels, many starfish and sponges. These animals are present on all substrate types but are particularly richly developed on hard substrates and are most abundant and diverse in rocky intertidal areas and coral reefs. A third category include animals hat live in association with the seafloor but also swim temporarily above it and include prawns and crabs and flatfish such as sole ( Parsons and Lally, 1997). The macrobenthic composition of a particular area traditionally gives baseline information along with valuable insights on the interaction between the biotic and abiotic components of a benthic community. As concerns on the consequences of effluent discharges heighten, the benths are now looked upon as probable indicators of environmental changes (Rees et. al. 1991). JPAIR: Multidisciplinary Journal 108 The balanced ecological conditions with a diverse flora and fauna characterize a pristine environment. In such an environment of stable condition, conservative species are traditionally regarded as the competitive dominant and are usually the first ones affected by perturbation. Benthic community assemblages are composed of organisms with diverse functional groups defined by feeding types, mobility and method of food capture, reproductive modes, life history patterns and physiological adaptations to environmental conditions (Kennish, 1994). This diversity along with limited mobility, close association with the sediment substrate and ease of quantitative sampling are all good indicators of healthy habitat to benthic organisms. Information from macrobenthic studies, i.e., shifts in population and community parameters has a history of use in monitoring programs (Kemp et. al., 2005), assessment of water quality (Che and Morton, 1991) and pollution effects (Grizzle and Penniman, 1991 provide baseline information on impacts of human associated activities such as fishing activities (Thrush and Dayton, 2002), dumping of sewage sludge (Lopez Gappa et al., 1990 and recovery after cessation of dumping (Moore and Rodger, 1991). Studies on benthos in the Philippines are expanding in scope, these studies focus on associated fish and/or characteristics of certain islands or reefs (Estacion et al., 1993) to taxonomy (Palpal-Latoc 1996), community assemblages (Mequila et al., 2004) and oil spill impacts. FRAMEWORK Benthic fauna in the world conatin cosmopolitan genera and species occupy similar ecological niches. Their distribution is affected by various physical factors. No single variable is controlling, rather influence can be heightened or lessened depending on their combination (Maurer et al., 1978). It has been shown that the substratum is a significant factor influencing benthic diversity (Li and Gao, 1989). At the Berg River estuary, distribution and seasonal abundance of invertebrate macrofauna was closely tied to sediment characteristics and vegetation cover (Kalejta and Hockey, 1991). The benthos of gastropod group at the Berg River estuary were restricted to certain sediment types favouring a coarse sediment. Salinity can be International Peer Reviewed Journal 109 factor in determining the distribution of benthic organism. Freshwater, marine and estuarine benthos all play similar ecological function, but the composition can be quite different (Coumo and Zinn 1997). As a response of stenohaline species to reduce salinity, a reduction in the number of marine macrofauna toward the estuaries can be expected. Gage, 1972 in Maurer et al., 1978 concluded that salinity was more influential in controlling the distribution of brackish macrofauna than sediment type in shallow water but at greater depths, the reverse was true. Waves are the main reason for water movement (Levinton, 2001), especially in the intertidal area of the sea. Its effect can reach up to a maximum depth of 10-20 meters wherein sand is moved. These vertical disturbances to the water surface can cause resuspension of the fine- grained sediments, extend the intertidal zone and influence mixing of atmospheric gases and penetration of light (Li and Gao, 1989 (. In shallow, enclosed inlets, the tides play role in the periodic movement of water. The dynamic physical environment is rarely considered in relation to faunal community despite the role played by tidal currents in influencing the nature of the bottom substrate. Warwick and Uncles, 1980 in their work on the Birstol Cahnnel, were able to directly correlate faunal type and tidal stress. Frascari et al., (2002) attributed the dominance of mollusks and a polychaete in the shallow areas of the Fattibelo Lagoon to continue oxygenation of tidal currents and wave motion. Such findings are relevant to initial understanding of physical control of community structure and function. Biotic predations, such as predation and competition can also play a role in controlling community structure. It has been reported that in eutrophical site, predation is not A major controlling factor of community structure. However, in non-eutrophicated site, it could be an important factor controlling abundance at least of some faunal components. Berge and Valderhaug (1983) studied the effect of epibenthic macropredators in a low-energy subtidal eutrophicated habitat of the Oslofjord, in an attempt to verify and elucidate previous findngs and concluded that macropredators are not important in determining community structure in sediments, exerting a small controlling effect on the densities of the macrofauna. Their conclusion was contrary to findings of Alongi and Christofferson (1992) who concluded that epibenthic predation, along with several JPAIR: Multidisciplinary Journal 110 other factors such as low food availability, periodic disturbance by tidal effects, etc. to be one of the major regulators in the distribution, abundance and structure of benthic infaunal assemblages in the Great Barrier Reef. OBJECTIVES OF THE STUDY The present study aims to investigate the macrofauna composition associated with seagrass communities in west and east portions of Igang Bay Nueva Valencia, Guimaras. A monitoring study of the seagrass communities in the said sites started on April 2008 and is still ongoing until April 2010. However, a faunal composition associated on east and west Igang Bay seagrass communities has never been conducted. This study will provide insights on the habitat health of the seagrass communities in Igang Bay. Specifically, the determination of faunal composition of the macrobenthos in east and west Igang Bay seagrass communities and the physical factors like the substrate type, temperature, salinity, and water depth will be addressed. MATERIALS AND METHODS The study was conducted in the seagrass communities of east and west Igang Bay where the monitoring study is conducted. Three 50-meter transects with a distance of 50 meters from each transect were laid in each site. From each transect, 3 points at 5, 25 and 45 were sampled by placing 1 m x 1 m quadrat in each point. The macrobenthic animals found inside the quadrat was recorded and the numbers were counted. The physico-chemical parameters were noted such as the temperature at each point at the mid-water depth. Water samples were taken for salinity and substrate types were characterized and noted. The degree of vegetation was described and recorded. The macrobenthic animals present in every quadrat were identified and recorded according to their groups (i.e., bivalves, corals, gastropods, starfish, sea urchin, sea cucumbers, crabs, shrimps, sponges). The relative abundance, frequency, dominance and important values of every group of macrobenthos and the indices of diversity and similarity of macrobenthos of one site to the other were International Peer Reviewed Journal 111 determined using the following formulas (Odum, 1971): Relative density = number of individual organism per group x 100 Total sampled area (9 square meter) Relative frequency = number of occurrence of each group x 100 Total number of occurrences of all groups Relative Dominance = number of individual organism per group x 100 Total number of all individuals Importance Value = Relative density + Relative frequency + relative dominance Index of diversity (Shannon index of general diversity H’) = - ∑ (ni/N) log (ni/N) Where: ni = importance value for each group N = total of importance values Index of similarity (S) = 2C / A + B Where: A = number of groups in east Igang B = number of groups in west Igang C = number of groups common to both sites RESULTS AND DISCUSSION Eight groups of macrobenthos were found to occur in the seagrass community of West Igang which include the hard coral, gastropods, bivalves, soft coral, starfish, limpet, hermit crab and cowrie (Table 1) while only seven groups were recorded in East Igang that include the bivalves, gastropods, snail, cowrie, hard coral, hermit crab and sponge (Table 2). Common to both sites were bivalves, gastropods, hard coral, hermit crab and cowrie while soft coral, starfish and kimpet were observed in West Igang and but not found in East Igang. On the other hand, snail and sponge were not sampled in West Igang Igang which were not observed in West Igang (Table 4). JPAIR: Multidisciplinary Journal 112 Table 1. Macrobenthic components found associated with seagrass community in West Igang, Villa Igang, Nueva Valencia, Guimaras Groups Rel. Density Rel. Frequency Rel. Dominance Importance Values hard coral 31.85 29.67 31.84 93.369 gastropod 36.96 21.34 36.94 95.241 bivalve 24.53 24.37 24.52 73.419 soft coral 2.40 7.20 2.40 11.995 starfish 1.89 7.20 1.89 10.985 limpet 0.51 3.03 0.51 4.040 hermit crab 0.51 3.03 0.51 4.040 cowrie 1.39 4.17 1.39 6.944 Among groups in West Igang, the gastropods were found to be most abundant and dominant with a relative density of 36.96% and relative dominance of 36.94% while hard coral was most frequent to occur in sampled points with relative frequency of 29.67%. Least abundant, frequent and dominant groups were exhibited by the limpet and hermit crab with values of 0.51%, 3.03% and 0.51%, respectively. Most important group observed was the gastropod with importance value of 95.241 while limpet and hermit crab with 4.040 were least important groups in West Igang )Table 1). In East Igang, the bivalve was found to be the most abundant group with 55.28% while most frequent and dominant group was gastropod with values of 40.00% and 40.39%, respectively. Sponge was found to be the least important group observed in East Igang with a value of 4.046 while the gastropod was the most important group of all with value of 106.997 (Table 2). International Peer Reviewed Journal 113 Table 2. Macrobenthic components found associated with seagrass community in East Igang Bay, Villa Igang, Nueva Valencia, Guimaras Groups Rel. Density Rel. Frequency Rel. Dominance Importance Values bivalve 55.28 24.44 36.03 99.402 gastropod 21.13 40.00 40.39 106.997 snail 2.90 8.89 2.90 18.335 cowrie 4.94 8.15 4.94 19.845 hard coral 7.04 8.89 7.04 26.610 hermit crab 7.96 8.89 7.96 24.758 sponge 0.74 0.74 0.74 4.046 Comparing the indices of sites, West Igang was found to be relatively more diverse in terms of macrobenthic organisms associated with seagrass community with an index of 0.608 than East Igang with 0.513 (Table 3, Figure 1). Index of similarity of these macrobenthos between the two sites is relatively high with a value of 0.667 (Table 3). Table 3. Indices of diversity and similarity of macrobenthic components associated with seagrass communities in West and East Igang Bay, Villa Igang, Nueva Valencia, Guimaras Indices West Igang East Igang Diversity Index )H’) 0.608 0.513 Similarity Index (S) 0.667 JPAIR: Multidisciplinary Journal 114 Figure 1. Index of diversity of macrobenthos associated with seagrass communities in West and East Igang Bay, Villa Igang, Nueva Valencia, Guimaras Table 4. Groups of macrobenthos associated with seagrass communities in West and East Igang Bay, Villa Igang, Nueva Valencia, Guimaras groups West Igang East Igang hard coral gastropod bivalve soft coral starfish limpet hermit crab cowrie sponge snail International Peer Reviewed Journal 115 The physico-chemical parameters were observed to be variable between two sites especially in temperatures. However, higher salinity was recorded in West Igang. Type of substrates was relatively similar between sites with occurrence of occasional rocky bottom in West Igang (Table 5). Table 5. Physico-chemical parameters recorded in West and East Igang Bay, Villa Igang, Nueva Valencia, Guimaras Physico-chemical factors West Igang East Igang Temperature (oC) Surface 30.67 32.67 Bottom 31.00 30.83 Salinity (ppt.) 30.00 28.67 water depth (m) 0.43 0.60 substrate rocky, sandy, silty-muddy in transect 1 sandy, silty-muddy CONCLUSIONS Some of the macrobenthos observed in West Igang but were not included in the sampled points were the sea cucumbers, sea urchins, sand dollar, sponges and snail. Starfish, brittle stars, sea urchins, sea cucumbers and soft corals were observed in East Igang. Degree of vegetation was relatively high in both sites. Starfish was observed to be relatively more abundant outside the sampled points in West Igang than East Igang. The same observation was inherent in sponges, soft and hard corals. JPAIR: Multidisciplinary Journal 116 LITERATURE CITED Alongi, D.M. and P. 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