Gastropod Community Structure Research Articles

The Community Structure of Gastropods (Mollusca Phylum) in The Intertidal Zone of Saung Beach, Wakan Village, Jerowaru District, East Lombok Regency

Gastropods are one of the phylum Mollusca classes having a single shell, normally spiral-shaped. This research aimed to analyze the Gastropod community structure (Mollusca Phylum) in the Intertidal Zone of Wakan Village, Jerowaru District, East Lombok Regency. The combination of line and quadrat transect was implemented to take samples in this study. The variables in the research include the type and quantity of Gastropods. There were 1.715 individual of Gastropod found in this study. They were included in 11 families and 17 species. The Gastropod species with the highest abundance value in station I and II was Strombus urceus with the abundance value of 12,8 ind/m2 and 5,72 ind/m2, respectively. Meanwhile, in station III, it was Terebralia sulcate with the abundance value of 3,4 ind/m2. The diversity index of Gastropods in the research location was categorized as medium (H’=2,32) with a stable divercity index (E=0,84) and a low domination index (C=0,14).

Gastropoda community structure in the mangrove forest of Ketapang Coastal Waters, Rupat District

Gastropod community structure is a concept or study that studies the arrangement or composition of species in an ecosystem. Changes influence the structure of this gastropod community in terms of environmental factors such as temperature, salinity, substrate type, and organic matter content. Rupat District is geographically located in a cluster of islands directly adjacent to the Strait of Malacca, strongly influenced by coastal environmental conditions. Rupat sub-district has one of three tropical marine ecosystems, namely mangroves. This study aims to determine the structure of gastropod communities in mangrove forests in Ketapang Beach, Rupat District waters. The study was conducted in April 2023 using the technique of random sampling with a total of three stations. There are 8 (eight) species of gastropods found, with the species Cerithidea obtusa the dominant one. The abundance of gastropods is 130,000 ind/ha. The value of the diversity index (H') is 1.24, the uniformity index (E) is 0.33, and the dominance index value (C) is 0.40. The distribution pattern (Id) is grouping. The similarity index (Ss) of gastropods between each station in Ketapang Beach is almost the same type and has similarities that are classified as high category. Test results Oneway ANOVA < 0.05. The LSD (Least Significance Difference) test states that the abundance between stations I and III is significant, just as stations II and III are markedly different. The abundance between station I and station II does not differ markedly.

Gastropod Community Structure in the Mangrove Area, Kuala Batee District, Southwest Aceh District

This research was conducted to determine the types of gastropods and the structure of the gastropod community in the Mangrove area of Kuala Batee District, Southwest Aceh Regency. The quantitative descriptive method is used to determine research stations using purposive sampling techniques. Gastropod sampling was carried out at three station locations, each station consisting of three sub-stations with a size of 10 x 10 m. In the substations, 15 transects measured 1 x 1 m, namely, two points at the corner of each transect and one point in the middle. The results of the research showed that the gastropods found were 11 species from 4 ordo, ordo Archaeogastropoda consists of Neritina turita, N.semiconica, N.variegate, Neritodryas dubia, and Clithon corona, ordo Ceanogastropoda consists of Faunus ater and Bitium munitum, ordo Mesogastropoda consists of Cerithidea optusa, Stenomelania plicaria, and Thiara scabra, ordo Ellobiida consist of Cassidula angulifera. The structure of the gastropod community in the mangrove area of Kuala Batee District, Southwest Aceh Regency, has a diversity index ranging from 0.65-1.32, including the medium category, uniformity index values ranging from 0.36-0.63 including the medium category, and dominance values ranging from between 0.33-0.63 is included in the medium category. Environmental parameters in the mangrove area show an average temperature value of 28.20C, a salinity value of 5.6 ppt, and a pH value of 8.3

Study of Gastropod Community Structure After Development of Tourism Activities on the Senjoyo River

It is thought that the development of the Senjoyo River as a tourist attraction in Semarang Regency will cause changes to the natural ecosystem in the area, one of which is changing the structure of the existing gastropod community. This research is a quantitative analysis research using a survey method that aims to examine the structure of the gastropod community after the development of tourism activities on the Senjoyo River. Gastropod samples were taken from 10 different observation stations along the Senjoyo River, which are located at 7˚22'23"S and 110˚31'37"E. Observation station locations were determined by the purposive random sampling method, based on tourism activity density. The result showed types of gastropods that were found in the Senjoyo River namely, Sulcospira testudinaria, Tarebia granifera, Brotia costula, Thiara scraba, and Melanoides tuberculata with clustered distribution patterns (Id>1). Statistical analysis showed that location affected gastropod abundance (Asymp. Sig of 0.043), with the highest abundance found at station seven (45,11 individuals/m2). So station seven, with sandy and muddy substrate conditions, moderate current speed (0.257 m/s), and rarely found human activity, is the most suitable location to support the survival of gastropods in the Senjoyo River. Furthermore, the gastropod community structure indicates environmental changes at observation stations nine and ten, the locations where the most activities and construction of tourism facilities were found. That was indicated by the low diversity (H’= 0.00-0.01) and evenness (E = 0.00) index of gastropods, and there is dominance by Sulcospira testudinaria (C= 0.98-1.00).

Gastropod community structure in the water of Terkulai Island Tanjungpinang City

Gastropods are marine biota found in the waters of Pulau Terkulai, Tanjungpinang City and are one of the catch of fishermen. However, information on the structure of the gastropod community in these waters is not widely known. The purpose of this study was to determine the types of gastropods, gastropod community structure, and the relationship between gastropod community structure and environmental parameters in the waters of Terkulai Island. This research was conducted in April-August 2023. Determination of sampling points using random sampling method as many as 30 points with sampling plots measuring 1x1m2. The results of this study obtained 650 individuals with 15 species of gastropods. The highest density was found in Batillaria attramentaria species with a total of 12.20 ind/m2. Gastropod community structure diversity value (H') ranged from 1.512 which is classified as moderate. The uniformity value (E) ranges from 0.558 which is classified as moderate and the dominance value (D) ranges from 0.353 which is classified as moderate. The results of the measurement of the physicochemical parameters of the waters are still at a feasible threshold for gastropod life. The principal component analysis (PCA) shows that the density with water parameters has a positive correlation with temperature and organic matter.

Gastropod community structure on seagrass beds in Bahoi Village, North Minahasa

The village of Bahoi has a vast expanse of seagrass meadows of approximately 16.50 Ha, located between mangrove and coral reef ecosystems. This study aims to inventory the gastropod species in the seagrass meadow of Bahoi village waters and to determine the gastropod community structure through analysis of species density, relative density, species diversity index, and dominance index. The method used was a transect line method along 50 meters and a 1x1m quadrat pulled towards the sea, repeated three times during low tide. A total of 117 individuals were found, belonging to 26 species (11 families and 17 genera) of gastropods in the seagrass meadow of Bahoi village coastal waters. Based on the results, the highest density value was 1.10 ind/m2 with a relative density of 28.20%. Based on the analysis, the dominance index (D) of gastropods in the seagrass meadow of Bahoi village coastal waters was low, with values of D = 0.019 to 0.041, indicating that there was no specific species dominance in the seagrass meadow of Bahoi village coastal waters. This has an effect on the diversity index with a value of H' = 2.51, which is categorized as moderate. These results show that the diversity of gastropod species in the seagrass meadow of Bahoi village waters is quite diverse due to the absence of specific gastropod species dominance.
 Keywords: Bahoi, Seagrass Meadow, Gastropods, Community Structure.
 Abstrak
 
 Desa Bahoi memiliki luas hamparan padang lamun ± 16.50 Ha yang berada di antara ekosistem mangrove dan ekosistem terumbu karang. Penelitian ini bertujuan untuk melakukan inventarisasi jenis-jenis gastropoda di hamparan lamun perairan Desa Bahoi, dan mengetahui struktur komunitas gastropoda melalui analisis kepadatan spesies, kepadatan relatif, indeks keanekaragaman spesies, dan indeks dominasi. Metode yang digunakan adalah metode transek garis sepanjang 50 meter dan kuadrat berukuran 1×1m yang ditarik ke arah laut, dan dilakukan ulangan sebanyak 3 kali pada saat air surut.Ditemukan 117 individu yang termasuk ke dalam 26 spesies (11 famili dan 17 genera) gastropoda di hamparan padang lamun perairan pantai desa Bahoi. Berdasarkan hasil penelitian, nilai kepadatan tertinggi sebesar 1,10 ind/m2 dengan kepadatan relatif 28,20%. Berdasarkan hasil analisis, Indeks Dominansi (D) gastropoda di hamparan lamun perairan pantai desa Bahoi tergolong rendah, dengan nilai D=0,019 sampai dengan 0,041 menunjukkan bahwa tidak terdapat dominasi spesies tertentu di hamparan padang lamun perairan pantai desa Bahoi. Hal ini berpengaruh terhadap Indeks Keanekaragaman dengan nilai H’=2,51 sehingga berada pada kategori sedang. Hasil tersebut menunjukkan bahwa keanekaragaman jenis gastropoda di hamparan lamun perairan pantai desa Bahoi cukup beragam dikarenakan tidak adanya dominasi spesies gastropoda tertentu.
 Kata kunci: Bahoi, Padang Lamun, Gastropoda, Struktur Komunitas

GASTROPOD COMMUNITY STRUCTURE IN THE INTERTIDAL ZONE OF PASUMPAHAN ISLAND, PADANG CITY, WEST SUMATRA PROVINCE

Pasumpahan Island is one of the islands located in West Sumatra Province which has various activities of daily life, especially in the intertidal zone; it is suspected that it can interfere with the existence of aquatic organisms one of which is gastropods. Studying the structure of gastropod communities in the intertidal zone is an interesting natural laboratory to study. This research was conducted from December 2021 to January 2022 on Pasumpahan Island Padang City West Sumatra Province. The purpose of this study was to determine the structure of the gastropod community which includes species, abundance, diversity, uniformity, dominance, and distribution pattern of gastropods. As supporting data in this study, several environmental parameters were also measured which included water quality, sediment type, and sediment organic matter content. The research method used is a survey method, where sampling using the quadrat transect method is carried out at 3 stations. Based on the results of the study found 13 species of gastropods. The most common species found at all stations was Pythia scarabaeus, where the gastropod abundance values obtained between stations ranged from 2,78 to 5,00 ind/m2. The value of the species diversity index ranged from 1,50 to 2,02, which was moderate, the uniformity index value ranged from 0,77 to 0,88, which was high uniformity, and the dominance index value ranged from 0,16 to 0,29, meaning that there were no species found dominates and the value of the distribution pattern ranges from 1,31 to 2,47 with a clustered distribution pattern

Community distribution and utilization of gastropods in the Coastal Area of Liki Island, Sarmi District, Papua, Indonesia

Abstract. Sujarta P, Mailissa MG, Keiluhu HJ, Hadisusanto S, Yuliana S. 2022. Community distribution and utilization of gastropods in the Coastal Area of Liki Island, Sarmi District, Papua, Indonesia. Biodiversitas 23: 5001-5011. Gastropods and snails are mollusk phylum animals with diverse species that inhabit and spread in various marine ecosystems. The main objective of this study was to determine the structure of gastropod communities and their utilization in the coastal area of Liki Island, Sarmi District, Papua, Indonesia. Samples of gastropods were collected through descriptive-quantitative surveys using the line-transects technique. In addition, information on the utilization of gastropods was collected from surveys with semi-structural interviews with selected respondents from Liki Island, the outermost island in East Indonesia, with a total area of 1318.54 ha. The result showed a total of 1812 living specimens from 63 species of gastropods from 23 families, collected from six sampling stations, with 182-603 specimens on average. There were five species of gastropods encountered in all sampling stations, namely Conus litteratus (family of Conidae), Monetaria moneta, Monetaria annulus (Cypraeidae), Oxymeris crenulata (Terebridae), and Polinices flemingianus (Naticidae). The highest Importance Value Index (IVI) belonged to Nerita albicilla (Neritidae) from Station 1 (IVI 58.45). In contrast, the lowest belonged to the species of Nassarius limnaeiformis (Nassariidae), Oliva caerulea, and Oliva oliva (Olividae) from Station 4 (each IVI 2.56), with the moderate value of Shannon-Wiener Diversity Index and low value of Dominance Index. People in the coastal area of Liki Island use 12 species of gastropod as wall ornaments and consume 12 species of gastropod, as well. In general, the people of Liki Island use gastropods wisely based on the socio-cultural characteristics of the local community.

Gastropod Community Structure in Ecosystem Lamun Village Lihunu North Minahasa Regency North Sulawesi Province

The research was conducted in the seagrass ecosystem of Lihunu Village, East Likupang Subdistrict, North Minahasa Regency, and North Sulawesi Province. The area is one of the coastal areas in North Sulawesi that lack information about gastropod resources. Therefore, the main reason for conducting research is to find out the presence of gastropods in the area. The purpose of the study was to know the types of gastropods and to know the structure of communities through species density, relative density, diversity, and dominance. Sampling is done using the quadratic transect technique measuring 50 x 50 cm. Quadrate used 50 cm x 50 cm, then converted to square meters to 0,25 m2. The density of the species is 4,80 Ind/m2. The relative density value of the species with the highest percentage is in Euplica scripta Species with a value of 14,44% and the species with the lowest percentage value, namely Cymbiola vespertilio Species with a value of 0,56%. Diversity index values in 3 transects fall under the high criteria. Transect 1 is H'= 5.30, transect 2 is H'= 4,18 and transect 3 is H' = 3,95. And the highest dominance value in Euplica scripta Species with a value of C = 0,48. The water area of Lihunu Village of North Minahasa Regency has an average temperature of 30 ° C. Salinity is obtained with an average of 30‰. The degree of acidity (pH) obtained is 8.Keywords: Gastropod; Community Structure; Lihunu.AbstrakPenelitian dilakukan di ekosistem lamun perairan Desa Lihunu, Kecamatan Likupang Timur, Kabupaten Minahasa Utara, Provinsi Sulawesi Utara. Daerah tersebut menjadi salah satu daerah pesisir di Sulawesi Utara yang kekurangan informasi mengenai sumberdaya gastropoda. Oleh karena itu, yang menjadi alasan utama melakukan penelitian adalah untuk mengetahui keberadaan gastropoda di daerah tersebut. Tujuan dari penelitian ini yaitu mengetahui jenis-jenis gastropoda serta mengetahui struktur komunitas melalui: Kepadatan spesies, kepadatan relatif, keanekaragaman, dan dominansi. Pengambilan sampel dilakukan dengan menggunakan teknik transek kuadrat berukuran 50 x 50 cm. Kuadrat yang dipakai 50 cm x 50 cm, kemudian dikonversikan ke meter persegi menjadi 0,25 m2. Nilai kepadatan spesies yaitu 4.80 Ind/m2. Nilai kepadatan relatif jenis dengan persentase tertinggi terdapat pada Spesies Euplica scripta dengan nilai 14.44% dan spesies dengan nilai persentase terendah yaitu Spesies Cymbiola vespertilio dengan nilai sebesar 0,56%. Nilai indeks keanekaragaman di 3 transek masuk dalam kriteria tinggi. Transek 1 yaitu H’= 5,30 ,pada transek 2 yaitu H’= 4,18 dan transek 3 yaitu H’ = 3,95. Dan nilai dominansi tertinggi pada Spesies Euplica scripta dengan nilai C = 0.48. Daerah perairan Desa Lihunu Kabupaten Minahasa Utara memiliki rata-rata suhu 30°C. Salintas yang diperoleh dengan rata-rata 30‰. Derajat keasaman (pH) yang diperoleh yaitu 8.Kata kunci :Gastropoda; Struktur Komunitas; Lihunu.

COMMUNITY STRUCTURE OF FRESHWATER GASTROPODS IN NORTH KOLAKA REGENCY SOUTHEAST SULAWESI

This research was conducted in January-March 2021 in North Kolaka Regency. The purpose of this study was to determine the structure of the freshwater gastropod community in North Kolaka Regency. This research applies a combination method (qualitative-quantitative) in determining the sampling location and sampling process. Determination of the sampling location using purposive sampling method based on the presence of gastropod communities and quantitative sampling using simple random sampling technique. Gastropod samples were collected manually using a metal hand scoop and gloves. The total gastropod sample obtained at 17 sampling points was 4250 individuals. The gastropod community structure in North Kolaka Regency consists of 19 genera and 33 species spread over 9 families, namely Achantinidae, Ampullariidae, Ariophantidae, Lymnaeidae, Neritidae, Pachychilidae, Planorbidae, Thiaridae and Viviparidae. The results of the analysis of the gastropod community structure showed a relatively stable condition, where the average abundance of gastropods reached 91.94 ind./m2 and the abundance of gastropod species ranged from 0.29-16 ind./m2. Gastropod species diversity was categorized as moderate with a maximum value (H' = 2.96) or close to H'>3 (high category), moderate evenness (E = 0.85), high species richness (R = 4.35), dominance which showed that there was no dominant species (C = 0.08) and the distribution of gastropods showed a clustered pattern (Ip = 0.01). The freshwater types in North Kolaka Regency are generally rocky rivers so that the gastropod community is dominated by the Neritidae and Thiaridae families, especially the Tarebia granifera, Melanoides tuberculata and Clithon corona.

Gastropods in the Intertidal Shore of Kota Kinabalu, Sabah (Malaysian Borneo)

Intertidal gastropods provide numerous ecological benefits and are responsible for the dynamics of the intertidal shores habitat and its community assemblages. This study examined the community structure of gastropods in the intertidal shore located near the city of Kota Kinabalu, the capital of Sabah where coastal areas are rapidly developed for various purposes and consequently destroying natural habitats. A total of 36 gastropods species from 15 families were recorded. The Planaxis sulcatus was the most abundant species with a density of 480 ind. m-2 followed by Nodilittorina pyramidalis (182 ind. m-2) and Cellana radiata (97 ind. m-2) respectively. The number of species and their abundance, respectively, are almost three times lower than the number ever recorded for intertidal shores located in non-urban areas or remote locations. This suggests that the rapidly growing coastal urban areas threatening the diversity and abundance of intertidal gastropods. The density of gastropod (i.e. P. sulcatus & N. pyramidalis) was significantly (p<0.05) high at the lower intertidal shore where slope gradient is steeper with rocks and crevices are the major component of substrates compared to the upper or middle zone which is flatter and composed mainly of coral rubble and sand. Our study suggests that gastropod communities in intertidal shores located adjacent to the urban areas are threatened especially by anthropogenic factors such as frequent human visitations and modification of natural habitat. Future development in the intertidal shore should minimise habitat destruction and should consider infrastructures that encourage gastropod populations to grow and highlighting their ecological role for conservation reasons.

Gastropod Community Structure as Environmental Change Signals for Tropical Status In Sedati Waters, Indonesia

Gastropod Community Structure as Environmental Change Signals for Tropical Status In Sedati Waters, Indonesia

Community structure of gastropods and bivalves associated in mangrove ecosystem at Pusung Cium Island, Seruway, Aceh Tamiang

The purposes of the present study were to analyze the community structure of gastropods and bivalves as well as to analyze the relationship between the abundance of gastropods and bivalves within mangrove density in Pusung Cium Island, Seruway, Aceh Tamiang Regency. The research was conducted from October to November 2019. The method used in determining the location of the research station was Stratified Random Sampling based on the density of mangrove vegetation, the station 1st, 2nd, 3rd were dense, medium, and rare categories, respectively. There were 4.67 ind/m2 consisted of 3 species for bivalves class and 143.33 ind/m2 species of gastropods class consisted of 41 species. The highest abundance was in station three, and the highest gastropods species abundance was Littorina angulifera (51.33 ind / m2) and Saccostrea cucculata (1.33 ind / m2) for bivalves class. Biological indices showed that the diversity index of gastropods and bivalves was high and ranged from 4.24 to 2.35, evenness and dominance indices were ranged from 0.44 to 0.79 and 0.20 to 0.21. Furthermore, the distribution pattern of gastropods and bivalves were uniform, random, and clumped. The correlation between the density of mangrove and abundance of gastropods-bivalves was weak and moderate and there was no significant correlation between the density of mangrove and abundance of biota aquatic (gastropods and bivalves) where Psig > 0.05. In conclusion, the community structure of gastropods and bivalves was in stable condition showed by high diversity index, moderate evenness index, and low dominance index.

Community Structure of Gastropods in Seagrass Meadows at Coastal Area of Nusi and Gersen, Nabire Regency

Gastropods plays an important role in the food chain on seagrass ecosystem and its existence are depend on the physical-chemical factors in the seagrass ecosystem. This study aims to determine the density and diversity of gastropods associated in seagrass habitat in Nusi and Gersen coastal waters. The measurement results of some physical-chemical waters variables, are still quite good for the life of gastropods. Species composition of gastropod in Nusi at higher than at the Gersen, but instead of individual density in Gersen more higher than Nusi. Diversity index of gastropods at Nusi station is higher (3,757) than Gersen (3.053), on the contrary the eveness and dominance index are higher at Gersen station than Nusi station. Community similarity index by species is low between the two stations, which indicates that the species of gastropods at both stations is quite different. The influence of human activity and higher utilizatin of gastropods in Nusi has lowered the density of gastropods in seagrass habitat, so it needs awareness efforts on the importance of gastropods and the seagrass habitat for coastal ecosystem.

The community structure of Gastropods as bioindicators of water quality in Krueng Aceh, Banda Aceh

Gastropods have an important role in an ecosystem that is directly involved in the food chain system and can be used as a bioindicator of water quality because it is sensitive to water pollution. This study was conducted to analyze the quality of the waters of Krueng Aceh by identifying the diversity of the Gastropod community and analyzing the COD and BOD content in the waters. The study used a purposive sampling method by applying 5 sampling stations along the study area. Gastropod samples are taken using Ponal Grab, which is 23 cm x 23cm and sieved from the substrate using a mesh filter. The results showed that the highest abundance index was obtained at station 1, which is 15 ind/m2. The results of identification in the study area are 15 Gastropod Species. Furthermore, the most widely found Gastropod species is Snail tiger, while the least is Margarites. This result informs that the highest diversity index is found at station 1, which is 2.51 categorized as moderate pollution and on the other hand the dominance index level is less than 0.50 or no one dominates at each station.

Community structure of Gastropods in mangrove ecosystem of Pulo Sarok Village, Aceh Singkil Regency, Indonesia

The purpose of this study was to determine the community structure of gastropods in the mangrove ecosystem in Pulo Sarok Village, Singkil District, Aceh Singkil Regency, Indonesia. This research was conducted in April 2018 located in the coastal mangrove ecosystem of Pulo Sarok Village, Singkil District, Aceh Singkil Regency. The purposive random sampling was used in this study. The results showed there were 564 individuals Gastropod in all stations consisted of 4 species of Gastropod, namely Faunus ater as many as 354 individuals, Terebralia palustris as many as 123 individuals, Neritina turrita as many as 58 individuals and Neritina semiconica as many as 29 individuals. The highest density (D) was found at station 3 with a value of 2.44 Individuals per m−2. The diversity (H ') obtained from the three stations ranged from 0.50 to 1.77 which was categorized a the low and medium levels. Evenness index (E) from 0.14 to 0.37 which were in the low category. Furthermore, Domination index (C) of Gastropods range from 0.32 - 0.83. The level of similarity index (IS) ranges from 85.71% - 100%. It is concluded that based on the biological indices the structure of the Gastropods community in the Pulo Sarok Village is at the poor category.

STRUKTUR KOMUNITAS GASTROPODA DI SUNGAI DIGOEL DISTRIK EDERA KABUPATEN MAPPI

Edera District is the one of separated districts of six districts in the Mappi Regency. The increasing of community population has caused an increase activities in resource utilization, especially in the Digoel River area. As a result of excessive utilization activities can potentially cause pollution that threatens the existence and continuity of organisms such as Gastropods. This study aims to determine the community structure of Gastropods in the Digoel River in Edera District, Mappi Regency. The study lasted for 3 months from January to March 2018 by using the survey method and reviewing several variables including: diversity index, uniformity index and dominance index. The results showed that at the 3 observation stations the total sample was 1233 individuals. The highest diversity index value was at station II, namely itlic. and lowest was at station I Ellobium chinense species. Uniformity index shows that the number of uniformity is not evenly distributed in all three stations due to the occurrence of certain types of dominance.
 
 Keywords: Gastropoda; Community Structure; Digoel River; Mappi Regeucy
 Regeucy
 

Gastropod communities associated with different morphologies of the intertidal seaweed Hormosira banksii

Hormosira banksii is an important intertidal habitat-forming seaweed in southern Australia that shows large variation in morphology. We examined the relationship between morphological variation in Hormosira and associated gastropod community structure, abundance and diversity in Tasmania, southern Australia. We sampled both Hormosira and gastropods from sites in two habitats (coast and estuary), two times (February–March and October–November) at two regions (northern and eastern Tasmania). There were distinct Hormosira morphs on the north coast (small individuals), east coast (intermediate sized individuals) and in estuaries (large individuals). Multivariate analysis showed that gastropod communities varied among the different algal morphologies, and suggest an influence of morphological traits, specifically thallus length, vesicle number and size, on the distribution patterns of gastropod species. Despite the finding of distinct gastropod communities associated with the different Hormosira morphs, because the different morphs occur in different locations with different physical conditions, we cannot unequivocally attribute the differences in gastropod communities to seaweed morphology per se. Nonetheless, our results confirm that H. banksii is an important foundation species in the intertidal zone and suggest a habitat-specific effect of algal morphological traits on gastropods.

Structure of gastropod communities at mangrove ecosystem in Lubuk Kertang village, West Berandan District, Langkat Regency, North Sumatera Province

Gastropod was one of the class from mollusca in mangrove ecosystem. Lubuk Kertang Village’s mangrove forest was been converted into tourist areas, agricultural land and settlements. The purpose of this study was to analyze the structure of gastropods at Avicennia lanata, Rhizophora apiculata and Sonneratia alba. This research was conducted at Lubuk Kertang Village in February-March 2017. Gastropod were collected in 1 m × 1 m transect in mangrove. Examples of biota were taken by using shovel, then the biota was inserted into a plastic bag sample, wrote date of sampling and identified. The results showed there were 15 species Gastropods, namely Achatina fulica, Cerithidea alata, Cerithidea cingulata, Cerithidea obtusa, Chicoreus capucinus, Cymatium pileare, Ellobium aurimisdae, Ellobium aurisjudae, Littoraria melanostoma, Littoraria scabra, Murex tribulus, Nerita balteata, Nerita planospira, Pugilina cochlidium, Stramonita gradata, Telescopium telescopium and Terebralia sulcata. Diversity index ranged 1.702 to 2.165 was in medium category, Similarity index ranged 0.676 to 0.799 was in low category and Dominance index ranged 0.142 to 0.282 that categorized was low. The highest gastropod density was 31 individuals/m2 in the Sonneratia alba. The conclusion of the research is the existing mangrove ecosystem in Lubuk Kertang Village in a stable state.

Thirty-year recovery of mollusc communities after nuclear experimentations on Fangataufa atoll (Tuamotu, French Polynesia).

A 30-year study of temporal changes in gastropod community structure on the reefs of a Pacific Ocean atoll (Fangataufa, Tuamotu Archipelago) subjected to atmospheric nuclear tests during the 1960s offered the opportunity for an otherwise impossible field experiment that could help ecologists understand mollusc primary succession. Reef molluscs were partly or entirely wiped out by the heat of the nuclear tests and the reefs were recolonized by ocean larvae. On all reefs, community composition before the tests was very different from what it evolved to afterwards. A new method of analysis was developed to study the temporal variation in community composition before versus after the tests (temporal beta diversity). Analyses showed that community compositions diverged through time among the reefs. Only some species can survive the harsh conditions of supralittoral zones, so the same species recolonized them; environmental filtering controlled the development of the new communities. In the reef flat and edge zones, differences in community composition seem to be the result of neutral stochastic colonization by larvae coming from the open ocean. All reefs developed a community composition quite different from that before the nuclear tests.