Identification of Gastropodic Diversity in Aimere Coast Region Aimere District, Ngada Regency East Nusa Tenggara

: Aimere Beach is a beach located in the district of Ngada, Flores Nusa Tenggara East, and is a type of black sandy beach. The Aimere beach is not only used by fishermen but also as a tourist location, and there is a port as a means of transportation between the islands. There are many marine life that live in the Aimere Coast region; one of the biota found abundantly in the region is the gastropod. The degree of diversity of gastropods in an aquatic environment, especially in coastal waters, can be used as an indicator of pollution because these species have a high ability to adapt to their habitat. Therefore, this study aims to find out the diversity of gastropod species in the Aimere Coast region. Besides, to find out about the index of diversity, uniformity, and dominance of the gastropods in the Aimere Coast region. The method used is random sampling with samples taken from 3 stations, each consisting of 5 plot sizes of 1x1 m2. Data from the identification of gastropod species was analyzed using the diversity, uniformity, and dominance index formulas. The results of the research showed that the gastropod species found in the Aimere Coast region were 30 species belonging to 13 families. The index of diversity, uniformity, and dominance of the species of gastropods in the area of Aimère Coast is 2.8922, 0.8504, and 0.0738, respectively. These values indicate a high value of diversity, high uniformity, and a low value of dominance for gastropods .


INTRODUCTION
Indonesia is one of the countries that has thousands of coastal territories.The coastal region of the country extends from Sabang to Merauke, with so much fascinating coastal biodiversity.One of the islands in Indonesia that has a lot of coastal area is Flores Island.Flores Island has a variety of beaches with characteristics of both white sandy and black sandy beaches.Besides, the beaches on the island have a wide variety of marine life that is still very little known by the community because of the minimum research on the diversity of sea life on the Flores Island Coast.The beach is a sort of black sandy beach with calm sea waves, and its shoreline consists of sand and rocks as well as coral reefs with a variety of marine life.
There are many marine biota that live in the Aimere Coast region; one of the biota found abundantly in the region is the gastropod.Gastropoda is the largest class of Moluska filums, comprising 80,000 species, of which 1,500 are found in Indonesia (Ira et al., 2015).(Aba & Safrina, 2020).The gastropods have shapes and sizes that vary in shell size, with scales on the shell as well as a well-developed head equipped with eyes and tentacles.(Persulessy & Arini, 2018).The animals belonging to this class have a very wide spread from the suburbs to the waters at a depth of 8200 meters.(Andrianti & Rizal, 2020).In addition, these animals are widely found in various types of habitat substrata, both hard substrates such as rocks and sand as well as soft substrates such as mud, because they have higher adaptive abilities than other classes of animals.(Triwiyanto et al., 2015).Gastropods are one of the most important groups in the aquatic ecosystem because of their role as vital organisms or keys in the food network of aquatic regions.The degree of diversity of gastropods in an aquatic environment, especially in coastal waters, can be used as an indicator of pollution because these animals have a high ability to adapt to their habitat (Supratman et al., 2018).(Suwondo et al., 2006).These animals have good adaptability to different habitats, such as marine, freshwater, and land.Differences in substrate in each such habitat allow for differential types of gastropods that occupy a region.(Rukmana & Purnomo, 2019).
The Aimere coast also has a port used as a means of transportation for the laurel line between the islands.In addition, on this beach there are also a lot of fish-fishing activities and other marine resources that are used as a natural tourist attraction.Along with www.ijlsar.orgAvaliable at: 4 8 | 5 575 P a g e the exploitation of potential natural resources on the coast, of course, the many activities carried out in this coastal region can be a threat to the marine life that lives in the area, especially gastropods.At the same time, data and information on the diversity of gastropods are still very small, especially in the coastal area of Flores Island.Therefore, it is necessary to do research on the identification of the diversity of gastropods in the Aimere Coast region, Aimère district of Ngada district, and East Nusa Tenggara district.This research aims to find out the diversity of gastropod species in the Aimere Coast region.Besides, to find out about the index of diversity, uniformity, and dominance of the gastropods in the Aimere Coast region.

METHOD
Sampling was carried out in the Aimere Beach area, located in the Aimère district of Ngada, East Nusa Tenggara.The method used is random sampling with samples taken from 3 stations, each consisting of 5 plot sizes of 1x1 m2.Station I (rock substrates), Station II (slightly sandy rock substrates), and Station III (sandy substrates).The gastropod species are identified based on the morphological characteristics of shell shape, color, and pattern.Data from the identification of gastropod species was analyzed using the diversity, uniformity, and dominance index formulas.

Diversity Index
Species diversity was calculated using the Shannon-Wiener index (Odum 1993) in (Ulum et al, 2012).H' = -Σ Pi ln (Pi) Description: H' = Species diversity index Pi = The proportion of individuals of a species to all individuals encountered, with Pi obtained from: Pi = Ni/Ntotal Ln= Natural logarithm

RESULT AND DISCUSSION Gastropoda species in the Aimere Coast Region
Research results suggest that there are several species of gasropods that live in the Aimere Coast region.The gastropods that were discovered consisted of 30 species belonging to 13 families, for a total of 2702 gastropodic individuals at the entire research station on the Aimere Coast.The most frequently discovered gastropod species were the Nerita patula, with 316 individuals at all stations.While the least known species are the Bela nebula with 13 individuals and the Clithon sp. with 13 people at the whole station, Below is a table of gastropod species in the Aimere Coast region that have been successfully identified (tabel 1).The family Turbinidae has the characteristic of having a hard, rough shell with a rough and lengthy operculum with a white or white edge, a green shell with brown black (Saleky dkk, 2020).In this study, species of the family Turbinidae were found, including Turbo argyrostomus and Lunella cinerea.Below is a picture of the two species.The Muricidae family has a characteristic shell with a variable shape with a long head with long legs and a slightly cut anterior.(Nafi,ah, 2019).Has a reinforced operculum of the inner rib.(Nuha, 2015).The gastropod species of this family that were found locally were the species Reishia bitubercularis and Morula anaxares.Below is a picture of the species.

Figure 16. Species Morula anaxares
The Nassariidae are a family of gastropods that have a slightly rounded, swollen shell with a rib-to-rib surface leading to the axial.It has a short spire with a small aperture and a relatively small and narrow siphon canal, while the lips are in a smooth state without any folds.Extral shell rotation direction (Maretta dkk, 2019).The species of this family found are Nassarius reeveanus, Nassaris exilis, and Nassaarius pupinoides, according to the picture below.The family Littorinidae is characterized by a shell in the shape of eggs, a fine columella, and a thin operculum.(Nafi,ah, 2019).He has a head with a short hook and a knot-shaped tentacle.(Nuha, 2015).The species of this family found in the research area is Littorina littorea, according to the picture below.

Figure 20. Species Littorina littorea
The family Cerithiidae is a family of gastropods characterized by a crochet shell with brown and black spots, a thick and sharp elongated shell, and a large number of axial twists.The shell has a dextral rotation direction with an elongating aperture and a short siphon canal, and a columella without a strong spiral fold.(Maretta dkk, 2019).Species of this family found include Clypeomorus inflata and Clybeomorus subbrevicula, as shown below.
. The family Columbellidae is a family of gastropods that has a small, thick shell with a surface without axial lines, a brownish shell, and white, black, and slightly yellow spots.In the direction of the dextral rotation, with an elongated spire and a long and narrow aperture, there is also a short sifon canal (Maretta dkk, 2019).The species of this family found on the Aimere Coast are the species Anachis terpsichore and Pardalinops testudinaria, according to the following picture.The family Costellariidae is a family of gastropods that has a circular shell shaped like an egg, no operculum, and a meruncing apex.Has a small, narrow head, a pair of tentacles, and small legs.(Nuha, 2015).One of the species in this family is Vexilum anthracinum.

Figure 25. Species Vexilum anthracinum
The family Mangeliidae is a family of gastropods with a small shell that is tall and has a fusiform to biconic shape.This family does not have an operculum with deep anal sinuses on the substructural tracks as well as a thick calus.(Nuha, 2015).One of the species of this family found on the Aimere Coast is the Bela nebula, as shown below.

Figure 26. Species Bela nebula
The family Trochidae is a family of gastropods that has a large shell in the shape of a brown-shaped white scratch with axial engraving and a spiral with a thong, as well as a flat shell base.The shell size is about 6 mm long and 5 mm wide.It has a wide and narrow syphon and a dectral direction of rotation.(Maretta dkk, 2019).One of the species of this family found on the Aimere Coast is Trochus lineatus, as shown below.The Nacellidae are a family of gastropods that have a shell that stands out in the middle of the front with colors that vary, like black, yellow, or brown.The edges of the shell have black radial lines from the inside to the outside.(Fitriani, 2020).One species of this family found on Aimere Beach is Cellana testudinaria, as shown below.

Figure 28. Species Cellana testudinaria
The Cymatiidae family is a gastropod family that has a medium-to very large size with a rough shell.The periostracum part is well developed and almost always has an outstanding shell part with a horned operculum with a large multispiral protokonch that usually disappears in adulthood.(Nuha, 2015).One species of this family found on the Aimere Coast is Gyrineum natator, as shown below.

Figure 29. Species Gyrineum natator
The Siphonariidae family is a gastropod family that has the characteristics of having a shell with a fold on the right side with a coat hole, and there is a clear lateral loop on the left side (Nuha, 2015).One species of this family found on the Aimere Coast is Siphonaria normalis, as shown below.

Index of Diversity, Uniformity, and Dominance of Gastropoda Species in the Aimere Coast Region
Based on the data on gastropod species that have been obtained, the index of diversity, uniformity, dominance, and abundance of the species of gastropods in the Aimere Coast region can be seen in the table below (table 2).The Gastropods Species Diversity Index in the Aimere Coast region is 2.8922, which indicates a high degree of diversity.On the diversity index, species Nerita patula has the highest diversity index value of all species at 0.25098.Species with the lowest variability index values are Clithon sp. and Bela nebula at 0.02568.If we look at the uniformity index, we get an index value of 0.8504, which indicates a high degree of uniformity.Species Nerita patula has the highest value of 0.07379.Species with the lowest uniformity value are Clithon sp. and Bela nebula, with 0.00755.Based on the dominance index, a value of 0.0738 was obtained, which indicates the low degree of dominance of gastropods in the Aimere Coast region.The gastropod species obtaining the highest index value is Species Nerita patula, which is 0.01368.Species with the lowest dominant index values are Clithon sp. and Bela nebula at 0.00002.

Table 2. Diversity Index (H'), Uniformity (E), dan Dominance (C) of Gastropod Species Found on the
Based on these four indices, the distribution patterns of the gastropod are influenced by environmental factors such as the availability of feed, competition with other biota, and predators.Each species has different adaptive abilities, so certain environmental conditions and factors cause adaptation differences, which affect the spread or distribution of gastropods in their habitat (Ardiyansyah, 2018).
Gastropoda is one of the environmental indicators; the animal class is very sensitive to the changes that occur in the environment due to the contamination of inorganic materials.(Ardiyansyah, 2018).Ranjan & Babu (2016), in Wulansari & Kuntjoro (2018), add that gastropods can be used as bioindicators of coastal waters when the coastal environment is indicated to be contaminated by heavy metals.This is because the animal moves slowly, lives in the water, has a diet of detritus, and is able to accumulate or build up imia compounds in its body tissues.
The index of diversity, uniformity, and dominance of gastropod species in the Aimere Coast region of 2.8922, 0.8504, and 0.0738, respectively, indicates a high degree of diversity, a high level of uniformity, and a low degree of dominance.
was calculated using the Simpsons Dominance index formula (1949) in (Ulum et al., 2012).C = Σ(Pi) 2 Description: C = Species dominance index Pi = The proportion of individuals of a species to all individuals encountered, with Pi obtained from: Pi = Ni/Ntotal