Geoeco Journal ISSN: 2460-0768 Vol

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044

THE ABUNDANCE, DIVERSITY, AND THE DENSITY OF MOLLUSKS IN TUTUWOTO MANGROVE AREA OF ANGGREK DISTRICT, NORTH GORONTALO REGENCY, GORONTALO, INDONESIA

Dewi Wahyuni K. Baderan1, Marini Susanti Hamidun2 , Farid S M3

1,2,3 Department of Biology, Faculty of Mathematics and Natural Sciences, Universitas Negeri Gorontalo, Jl. Jendral Sudirman No. 6 Gorontalo City 96128, Gorontalo Province, Indonesia. Tel./Fax. +0435-821752 e-mail: [email protected]

ABSTRACT

The aim of the current study is to calculate the value of the abundance, diversity, and the density of phyla mollusks in the Tutuwoto mangrove area of Anggrek District. The survey method is used in this study as a method, which means that it collects the data directly at the research area. The observations were carried out under mangrove stands. The area of the observation plot is 5m x 5m. Phylum mollusks collected at the study site were counted by the number of individuals, abundance, diversity, and density of the types of each species. Sanon-Wienner formula is used to calculate the species diversity, Brower formula is used to calculate the density, and Odum formula is used to calculate the abundance of the species. The findings show that it is found that the reasearch about phylum mollusks in Tutuwoto mangrove area consisted of 6 (six) types namely Terebralia sulcata, Terebralia palustris, Nerita articulate, Hexaplex trunculus, Anadara granosa, and Mactra grandis. Based on the calculation of the abundance, diversity, and density of the mollusks phylum at the research site, there are several types that have the highest value. In the gastropod class, Nerita articulata has the highest score with an abundance of 30.41%, diversity of 0.36, and density of 0.17 ind / m2, followed by Terebralia sulcata with an abundance of 28.07%, diversity 0.36, and density of 0.16 ind / m2. However, the lowest is owned by Terebralia palustris with an abundance value of 17.54%, diversity of 0.31, and density of 0.10 ind / m2. The values of abundance, diversity, and density in the bivalve class have different values. The type of Anadara granosa has an abundance value of 53.06%, diversity of 0.34, and density of 0.08 ind / m2 while Mactra grandis has an abundance value of 46.94%, diversity of 0.36, and density of 0.07 ind / m2. Based on the predetermined criteria of the Gastropod class, it has the abundance in many categories, exceptional of Terebralia palustris which has sufficient criteria.

Keywords: Mangrove, Mollusks, Tutuwoto

A. INTRODUCTION muddy coastal tidal areas (Bengen, 2001). Mangroves are categorized as the Lisna et al., (2017) states that mangrove types of plants that are often found on ecosystems are the main ecosystems muddy coasts and river estuaries. The supporting life that are important in coastal mangrove ecosystem is a tropical coastal and marine areas. Therefore, it can be vegetation community consisting of several concluded that the mangrove ecosystem is species that develop and are able to grow in a coastal ecosystem that consists of a group

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 of endemic coastal species that function as environment such as food availability, supporters of coastal life. predation, and competition. In addition, the Moreover, mangrove forests are one pressure and changes in the environment of the natural ecosystems that have high can affect the number of types and ecological value. The ecological functions differences in structure (Sari et al, 2012). of mangrove ecosystems include protecting Mangrove forests often get stress due the coast from wind attacks, currents, and to irresponsible management that will cause waves from the sea, habitats (living the pressure that can lead to changes in the quarters), feeding ground, nursery, and ecosystem, both affecting the physical, enlargement, and spawning ground for chemical, and biological conditions of the aquatic biota including, shrimp, crabs, fish mangrove forest itself. The damage to the and shellfish (mollusks). The animals mangrove ecosystem occurs because of the belonging to the phylum of mollusks are influence of two factors, namely natural and one of the non-fish biological resources that human factors. The natural factors that have high diversity. Some mollusks cause mangrove damage are the occurrence animals can live on land, fresh waters, and of storms, global warming and the rise of marine waters. Mollusks associate with the sea level. Moreover, the damage caused by mangrove ecosystem as a habitat for the human factors includes the existence of living, sheltering, spawning and also as a irresponsible logging, uncontrolled land food supply area that supports the growth of conversion and the use of unsynchronized these mollusks. According to Odum (1996), coastal areas between one region and etc. mollusks play a role as a food chain detritus The forests of mangrove in Tutuwoto feeder in the nutrient cycle because Village of Anggrek District, North mollusks are located as early decomposers Gorontalo Regency are located along the that work by chopping mangrove leaves coast with an area of 11 hectares (KPH into small parts and then being followed by North Gorontalo, 2010). The mangrove smaller organisms namely microorganisms area of Tutuwoto has experienced a so that its presence is very influential in the reduction in area, the local community uses food chain. The existence and abundance of mangrove areas as residential and mollusks in the mangrove ecosystem is agricultural areas, and uses mangrove wood largely determined by mangrove as a material for making houses and vegetation. The composition and diversity livestock pens. of mollusks are influenced by the local

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044

The lower understanding of the mangrove forests. A study that aims to community about mangrove forests that are determine the value of diversity, abundance used to fulfill their needs by themselves, and density of mollusks needs to be done. enable interdependence to overuse the So that the role of mangrove forests as a actions that have a detrimental effect supporter and provider of services for the resulting in habitat degradation without survival of the fauna inside is maintained. regard to sustainability and considerable B. MATERIALS AND METHODS benefits for ecosystem productivity. These The current research was carried out activities will affect the decreasing density in the Tutuwoto mangrove area of Anggrek of mangroves which results in less leaf litter District, North Gorontalo Regency, production and reduced decomposition Gorontalo Province. It was also conducted process as the supply of energy sources for for 3 (three) months, starting from April- living resources inside, especially June 2018. The timeline of the current mangrove crabs, mollusks, shrimp and fish research included the preparation of the that feed in the mangrove ecosystem. The research proposal, data collection, data changes caused by human activities such as analysis of the research to the report of increased logging of mangrove forests can research results. cause a decrease in the quantitative value of

b c

Figure 1. The research site, (fig. a) The condition of the mangrove, (fig. b) the outermost condition of mangrove, (fig. c) the adminisrative map of the research site.

A survey is used as a method in this fauna belonging to the phyla of mollusks is study, which is a method of collecting data done by direct observation. The observation directly at the research site. The aquatic is carried out under mangrove stands. The

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 area of the observation is 5m x 5m. The D < 5%, non-dominant category fauna found in the next observation plot is The abundance of each species is calculated using Odum formula (1996), as follows: counted the number of individuals and is 푲 recorded in the observation book. 퐭퐡퐞 퐧퐮퐦퐛퐞퐫 퐨퐟 퐭퐡퐞 퐢퐧퐝퐢퐯퐢퐝퐮퐚퐥 퐬퐩퐞퐜퐢퐞퐬 퐢 = 퐱 ퟏퟎퟎ% Furthermore, the aquatic fauna collected at 퐭퐡퐞 퐧퐮퐦퐛퐞퐫 퐨퐟 퐚퐥퐥 퐢퐧퐝퐢퐯퐢퐝퐮퐚퐥퐬 퐨퐟 퐭퐡퐞 퐬퐩퐞퐜퐢퐞퐬 the research site is calculated by the number By taking the criteria of the abundance by Michael, of individuals, abundance, diversity, and (1995) as follows: 0 = none density of each species. 1-10 = less 11-20 = enough >20 = many The calculation of the species diversity uses a Sannon-wienner formula: C. RESULTS AND DISCUSSION 퐇′ = −Ʃ 푷풊 퐥퐧 푷풊 where pi= (ni/N) Results

Where: Macintosh et al (2002) stated that H’ = The Diversity Index ni = Ʃ The individual of each mollusks are the organism that has an species N = Ʃ the total individual of all important role in ecological functions in the species mangrove ecosystems, namely as bio- Criteria : Odum, 1996 H’< 1 = Low diversity indicators in aquatic ecosystems. The group 1< H’ < 3 = Medium diversity mollusks mangrove as part of the mangrove H’ > 3 = High diversity forest ecosystem has an important role

The calculation of the density uses Brower which directly or indirectly supports the et al., 1990 formula: ecological functions of the mangrove 퐍퐢 forests. 푫 = 퐱ퟏퟎퟎ% 퐀 Based on the research results about Where: mollusks, it is found that there are six (6) 2 D = Biota density (ind/m ) types of mollusks found in the Tutuwoto Ni = The number of individuals A = the plot of the observation area mangrove area namely Terebralia sulcata, (m2) Terebralia palustris, Nerita articulate, By obtaining the D value, it can be made the Hexaplex trunculus, Anadara granosa, and classification of each species by referring to Mactra grandis. The classification of each the following dominance criteria species can be seen in the table 1 below, (Jorgensen): moreover, the morfology form is presented in the Figure 2. Criteria: D > 5%, Dominant category D = 2-5%, sub-dominant

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044

Table 1. The Classification of Mollusks Phylum Found in Tutuwoto Mangrove Area

PHYLUM CLASS ORDO FAMILY GENUS SPECIES Terebralia sulcata Caenogastropoda Potamididae Terebralia Terebralia palustris Gastropods Neritimorpha Neritidae Nerita Nerita articulata Mollusks Hypsogastropoda Huricidae Hexaplex Hexaplex trunculus Arcoida Arcidae Anadara Anadara granosa Bivalves Veneroidae Mactridae Mactra Mactra grandis

a b c

d e f a Figure 2. The Morphology Form of Mollusk Phylum Found in the Research site (a)Anadara granosa, (b)Mactra grandis, (c)Terebralia sulcata, (d)Hexaplex trunculus, (e)Nerita articulate (f)Terebralia palustris

The Abundance (K) Mollusk Phylum community. The index value of the The abundance is the number of the abundance at the research site is presented individuals in the particular site in a in Figure 3.

The Index of Mollusc Abundance

60 53,06 50 46,94 40 30,41 28,07

% 30 23,98 20 17,54 10 0 T. sulcata T. palustris N. articulata H. trunculus. A. granosa M. grandis Species

Figure 3. The Abundance Index of Mollusk at the Research Site

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044

The highest index of abundance is the river mouth. Therefore, this type owned by Anadara granosa with a value of dominates the area. 53.06%. The type of Anadara granosa (blood clams) is found in the study sites The Diversit (H’) Mollusk Phylum because it is associated with muddy The diversity is the total number of substrate conditions. Latifah (2011) species in a particular area or it is also emphasizes that blood clams are non-fauna, interpreted as the number of species which is alive by immersing themselves contained in an area between the total under the surface of the mud. The blood number of individuals of the species present clams are more commonly found in areas in a community. Wahyuni et all, (2017) farther away from river estuaries because states that a community has high diversity river estuaries are the sites most affected by if all species have relatively the same or pollutants and fisheries that can exploit almost the same abundance, besides, there shellfish excessively (Intan et al, 2012). is no large dominance so that the diversity This condition is in line with the conditions value in the study location reflects each at the research site whose substrate has species that spread relatively in equal characteristics that are muddy and far from numbers. The diversity index at the research site is presented in Figure 4

The Index of Mollusc Diversity 0,37 0,36 0,36 0,36 0,36 0,35 0,34 0,34 0,34 0,33

H' 0,32 0,31 0,31 0,3 0,29 0,28 T. sulcata T. palustris N. articulata H. trunculus. A. granosa M. grandis Species

Figure 4. The index of Mollusk Diversity at the Research Site

The results of the calculation of location are 2.07. This shows that the Shannon winner diversity about the total spread of individual numbers per species index of mollusk diversity in the study and community instability is classified as

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 moderate. The diversity in research grows in the area as a form of migration due locations in dominance by species to the high sea level. The foraging activities Terebralia sulcata, Nerita articulate and in this species are active at night and when Anadara granosa with the diversity value the condition of the water is not in tidal (H’) 0.36. These three types dominate the wave conditions because of its nature as a area because they are related to habitat, and scavenger. On the other hand, Mactra the way of life of each type. Nerita grandis breeds and lives in areas that have articulate and Terebralia sulcata types muddy sand substrates. generally live in groups and are often found attached to the roots, stems, leaves, rocks The Density (D) Mollusk Phylum and wood weathering. This is in line with The density results of the Molusca the statement by Nontji A. (2006), he phylum calculation at the location of the explains that Nerita articulate species is study show that there are several types that generally found in the groups with diverse have the highest value. Anadara granosa populations. This community can be found type has the highest value of 53.1% and in the supralitoral area with the followed by Mactra grandis of 46.0%. The characteristic of sticking, both in the roots, density index of mollusk at the research site stems and leaves of the vegetation that is presented in Figure 5.

The Density Index of Mollusc 60 53,1

50 46,0

40 30,4 28,2

% 30 23,9

20 17,5

0 T. sulcata T. palustris N. articulata H. trunculus. A. granosa M. grandis Species

Figure 5. The Density Index of Mollusk at the Research Site

Both types are included in the bivalve related to the place and way of life. The class. The height of these two types is blood clams of Anadara granosa and

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 mactra grandis grow well in calm waters, The environmental factors have a very especially in muddy bays that are 46-76 cm important role in supporting the mollusks or thicker. The high value is thought to be life. Based on the measurement of related to the substrate where they live and environmental factors at the research look for food and also their tolerance to the location, the environmental temperature extreme environment. This can be seen in results are ranged from 27-28oC, generally Bivalve life preferences in sandy mud or mollusks are able to adapt to varying mud habitat in the form of gathering and temperatures, that is from 0 ºC to 48.6 ºC spreading (Intan, et al., 2014). and is active at a temperature range of 5 ºC - 38 ºC (Wahyuni et al, 2017). For the The Enviromental Parameters at the details, the results of measuring Research Site environmental parameters are presented in Table 2.

Table 2. The results of measuring environmental parameters at the research site

Week Environmental factor

Temperature Humidity Soil ph Dissolved Water Salinity (ppt) (%) temperature oxygen (mg/l) (ºC)

The observations of salinity at the Discussion study site are still quite normal in The animals that live on the bottom of supporting the life of Mollusks, which the water are macrozoobenthos. ranged from 23.42 24 -24.17 ‰ because of Macrozoobenthos is one of the most the range of normal salinity values for important groups in aquatic ecosystems due mollusk life, which is ranged from 5 75 - 75 to its role as a key organism in the food ‰. Most Mollusk like the pH value around web. Furthermore, the level of diversity 7.0 - 8.5 and the pH at the research location found in the aquatic environment can be is at 6.6. Dissolved oxygen ranges from used as an indicator of pollution. Fitriyani 2.22-2.24, water temperature 28.23- et al., (2016) emphasizes that 28.42oC. Humidity ranges from 68-75%, macrozoobenthos is included in the initial decomposer which plays a role in chopping

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 the remnants of leaves that are reissued into survived by crawling and attaching the feces then followed by bacteria or fungi that body to the substrate. Mollusks also have convert organic matter into protein and good body resistance and shell adaptation, carbohydrates. The organic material is the so they are able to survive compared to most important contribution of mangrove other classes (Dali, 2018). Based on the forests to the ecosystem through litter calculation of the value of abundance, avalanches that fall into the forest floor. diversity, and density of aquatic fauna in The litter will be utilized by the mollusk class in the study location are macrozoobenthos as an energy source and in the dominance of the species Nerita will be broken down again by micro-fauna articulate (gastropod) and Anadara into nutrients that help mangrove growth. granosa (Pelecypoda). Both of these types Mollusks are categorized as one dominate the area because they are related organism that has an important role in the to habitat and the way of life of each type. ecological function of the mangrove Nerita articulate types generally live in ecosystem. As for those belonging to the groups and are often found sticking to the Mollusk group is phylum makrozoobenthos roots, stems, leaves, rocks and wood namely gastropod and bivalve which can be weathering. This is in line with the used as bio-indicators in aquatic statement of Nontji A. (2006) who explains ecosystems (Macintosh et al, 2002). that Nerita articulate species are generally Mollusks found at the research site are found in groups with diverse populations. Terebralia sulcata, Terebralia palustris, In the supralitoral area, this community can Nerita articulate, Hexaplex trunculus, be found with the characteristic of sticking, Anadara granosa, and Mactra grandis. The both in the roots, stems, and leaves of the group of mangrove mollusk as part of the vegetation that grows in the area as a form mangrove forest ecosystem has an of migration due to the high sea level. The important role that directly or indirectly foraging activities in this species are active supports the ecological functions of at night and the condition of the water is not mangrove forests. Some mollusk species in tidal conditions because of its nature as a such as members of the Potamididae, scavenger. Neritidae, and Carithidae are species that In relation to maintain its survival, make mangroves their habitat (Arbi, 2008). living things interact with the environment Moreover, mollusks have the ability and tend to choose the best environmental to adapt well to the mangrove environment, conditions and habitat types to continue to

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044 grow and reproduce. The factors that Nerita articulata species with a influence the growth of shellfish are the value of 30.41%, Terebralia sulcata season, temperature, salinity, substrate, species with a value of 28.07%, food, and other water chemical factors that Hexaplex trunculus species with a vary in each region. Measurement of value of 23.98% and the lowest physical-chemical parameters can describe owned by Terebralia palustris the quality of the environment at a certain species with a value of 17.54%. time. Besides, biological indicator 2. The value of diversity index of measurements can monitor continuously mollusks in the Tutuwoto mangrove and are easy instructions to monitor the area of Anggrek District, North occurrence of pollution. The physical- Gorontalo Regency shows that the chemical factors of the waters in the study spread of individual numbers per location are still below the threshold and are species and community instability is still within tolerance for the conditions of classified as in the moderate level. life and development of mollusks. The diversity value index of Therefore, the diversity of mollusks in the Terebralia sulcata, Nerita research location can also be influenced by articulata and Mactra grandis the physical-chemical factors of the waters. species has the same value namely H '= 0.36, Hexaplex trunculus and D. CONCLUSION Anadara granosa species have H' = 0.34, and Terebralia palustris As a conclusion related to the study species has a value of H '= 0.31. conducted in Tutuwoto mangrove area of 3. The index of the density value of Anggrek district, North Gorontalo, it can be mollusks in the Tutuwoto mangrove concluded that: area of Anggrek District, North 1. The abundance index of mollusks in Gorontalo Regency, shows different Tutuwoto mangrove area in values for each species. The highest Anggrek Subdistrict, North density index is owned by Anadara Gorontalo District, shows different granosa species with a value of values for each species. The highest 53.1%, Mactra grandis species with abundance index value is owned by a value of 46.0%, Nerita articulate Anadara granosa species with a species with a value of 30.4%, value of 53.06%, Mactra grandis Terebralia sulcata species with a species with a value of 46.94%,

GeoEco Journal ISSN: 2460-0768 Vol. 5, No. 1 (January 2019) Page. 43-54 E-ISSN: 2597-6044

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