Diversity of Echinoderms in Balekambang Beach, Malang District, East Java

Echinoderms is a component of biodiversity in the coral reefs. Echinoderms play an important role in ecosystem of coral reefs especially in food web, generally as predators and detritivors. This report aims to understand composition and density relative of fauna echinoderms on the Balekambang beach. The Transect line method were used and data retrieval was conducted at three stations. The result showed that echinoderms found in Balekambang beach consists of 7 species that are included in three classes, they were Phyllachantus imperialis, Tripneustes gratilla, Diadema setosum, Clypeaster reticulatus (Class Echinoidea), Archaster typicus (Class Asteroidea), Ophiotrix fragilis and Macrophiothrix belii (Class Ophiuroidea). The highest abundance of echinoderms on the station where located in the mangrove area which was dominated by Archaster typicus . The diversity of echinoderms on Balekambang beach were moderate category. The observations of chemical and physics parameters of the aquatic environment and the substrate obtained quite optimal for life ofEchinoderms.


INTRODUCTION
Echinoderms is a non-vertebrate organism that widely distributed in the ocean of Indonesia. Echinoderms can be found in the shallow waters up to abyssal dephts of the sea (Dahuri et al., 2001). Although, they are most likely to be found around coral reefs and seagrass beds in shallow water (Romimohtarto and Juwana, 1999). Echinoderms divided into several classes, they are Asteroidea, Echinoidea, Holothuroidea, Ophiuroidea and Crinoidea. Dani (2004), Echinoderm is a non-parasitic organism which live in litoral zone to 6000 m. Echinoderms are covered by a hard calciumrich plate called endoskeleton beneath their delicate skin. They have a unique circulatory system called ambulacra which distinguish them from other animal. They are a nonhermaphrodite organism and it is a bit difficult to distinguish whether male or female.
Intertidal areas such as the Balekembang beach is a suitable habitat for the majority of echinoderms. Echinoderms is a component of biodiversity in the coral reefs. Coral reefs provide shelter and food for the availability of echinoderms. The role of echinoderms in ecology is very important in food web, generally as predators and detritivor (Birkeland, 1989in Aziz, 1997.
The Balekambang beach in Malang District, Indonesia is one of coastal area which is utilized for tourist activities. In addition to tourism, the area is also used by local fishermen to fulfill their daily needs. Some local also sell dried coral-reef commercially for ornaments and accessories.
Echinoderm is one of the most important components in the food chain. When damage occurs on the community of echinoderms, the balance of food chain in the coastal ecosystem will also be disturbed.
The purpose of this study is to reveal composition and abundance echinoderms on the Balekambang beach, Srigonco, Bantur, Malang district, East Java.

a) Echinoderms Sampling
Transect line method was used to collect samples. Samples collection was conducted at three stations. Station 1 located in tourist area and human settlement, Station 2 located near estuary, and Station 3 located in mangrove ecosystem. The collection of echinoderms is hand sorted in the reef flat by transect method (Mudjiono, 1993). Transect was placed perpendicularly from the coastline to a recede. Samples were taken using a frame measuring 1 x 1 m plot on each transect. All samples were preserved in 50% alcohol (Class Asteroidea and Holothuroidea ) and 5-10% formalin (Class Echinoidea, Ophiuroidea and Crinoidea). The samples were marked by a label, label is written some information such as: collector's name, date of collection and collection station, and then taken to the laboratory for identification.
Water physical and chemical parameters were measured such as tidal range, temperature, current flow, substrates, pH, salinity, dissolved oxygen (DO) and total organic matter (TOM).

b) Data Analysis
The Data was analyzed by using a formula to calculate the abundance of echinoderms found on each station or point of the sample collection. Biological diversity (H') and dominance index (D) were calculated according to the following equation (Shannon and wiener, as well as Sampson index (1949) in Odum 1998).
Ni is total Specimen of related species N is total specimen S is total species.

a) Composition of Echinoderms
The result showed that three classes and seven species of echinoderms were found during data collection in Balekambang (Table  1). The lowest composition of echinoderms was found in station 1 which consists of Phyllachantus imperialis, Tripneustes gratilla, Diadema setosum and Macrophiothrix belii. The small composition of echinoderms at this station probably caused by human disruption of tourist and fishing activities.
The impact of human activities on seagrass ecosystems such as port development, domestic waste household, construction of organic waste, and pollution of agricultural waste could lead quality degradation to habitat destruction, increased water turbidity can also impact on damaged gills of aquatic animals, decreased dissolved oxygen content, and can be very harmful for animals associated with the seagrass (Fahruddin, 2002). This will also affect the existence of echinoderms and reduce the diversity in the water.
The highest composition of echinoderm was found in station 2 and 3. Seven species of echinoderm were found, they were Phyllachantus imperialis, Tripneustes gratilla, Diadema setosum, Ophiotrix fragilis, Clypeaster reticulatus, Archaster typicus and Macrophiothrix belii. Habitat in station 2 and 3 share similar condition and substrate. This resulting in similar data.

b) Echinoderms Abundance
The abundance value of echinoderms highly influenced by environmental factors. Based on Table 2, the lowest abundance was in station 2 (13 ind/m 2 ) which was dominated by Archaster typicus. Whereas the highest abundance was in station 3 which is equal to 19 ind/m 2 and was dominated by Archaster typicus. The results of the average abundance can be stated to represent the abundance of echinoderms in Balekambang beach.
The highest average of echinoderms abundance was 6 ind/m 2 for Archaster typicus, followed by Tripneustes gratilla of 4 ind / m 2 and the lowest average was Diadema setosum, Ophiotrix fragilis, Clypeaster reticulates of 1 ind/m 2 . The results showed that the habitat in Balekambang beach is suitable Archaster typicus and Tripneustes gratilla. This also supported by substrate analysis of Balekambang Beach which dominantly has sand substrate contained rocks.

DISCUSSION a) Diversity and Dominance of Echinoderms species
Archaster Typicus population are found in tidal areas (intertidal) with coral and sand substrate, distributed in coral reefs habitat of Indo-West Pacific region by Clark and Rowe in Darsono (1988). The high value of the average abundance Archaster typicus is supported by the high value of TOM in Balekembang waters which range between 63-112 ppm. Echinoderms prefer clean and clear water more to support the formation of cell bodies namely lining membranes fertilization which form the larva or embryo of echinoderms at later stage and will form a new individual in further stage.
Waters turbidity and dirtiness will inhibit larva development and the development of fertilization of echinoderms in waters. The abundance of echinoderms is affected by the ability to survive and to compete in their habitat. Some echinoderms are associated with a harder substrate (a mixture of sand and gravel) such as brittle stars from clan Ophiotrix, Ophioptheron, Ophiactis (Azis, 1997).
Based on Shannon-Wiener index, the range value of 1,207-1,649 belongs to medium diversity, while index of dominance value 0,216-0,333 belongs to low dominance. It shows that the distribution of echinoderms in Balekambang beach are evenly spread and absence of domination.

b) Environmental condition of Echinoderms
shown in Table 3. The tides range of each location were 1.5 m which are very tolerant for the life of Echinoderms. Water temperature in Balekambang beach ranges from 27-28° C which are suitable for Echinoderms growth. The types of substrate on the Balekambang beach were vary. Station 1 has rocky and sandy substrate with coral on it along with algae combined in puddles. Station 2 substrate tend to be sandy and there was rarely stone in it which is carried by the stream. Station 3 was sandy, rocky and a little muddy, with some algae in it. These three locations have suitable parameter and substrate for the life of echinoderms.
The average speed range of the current flow is 0.05 m/s-0.09 m/swhich can be classified in the category of very slow. This is in accordance with Welch (1980) in Ayudyawati (2001), who said that the current velocity in water can be divided into five categories: >100 cm/s categorized very fast; 50-100 cm/s: categorized fast; 25-50 cm/s: categorized medium; 10-25 cm/s: categorized slow; and <10 cm/s: categorized for very slow.
Water salinity of each location is ranging from 33-36% which classified in normal category. This is consistent with the statement in Effendi (2003) that the salinity of ocean waters is 30%-40 %. In general, echinoderms are stenohaline (have narrow tolerance in salinity range), although some members of a class asteroidea, ophiuroidea, the echinoidea and holoturoidea show wider tolerance. In this case a small group of the Echinodermata fauna can be categorized as euryhaline (Aziz, 1994). Drouin et al., in Azis (1994) adding that the adaptability of echinoderm group is lower than the molusca group due to their skin membrane relatively thin and very permeable.
Total organic material contained in the waters are ranged from 63-112 ppm. The total organic material of water is derived from vegetation mangrove around the station. The number of organic material is affecting the echinoderms for organic material is a source of food for echinoderm. According to Dahuri ( 2003 ), echinoderms are scavenger or detritus eater.

CONCLUSION
The diversity of echinoderms on Balekambang beach indicating the absence of domination. The echinoderms found in Balekambang beach consists of 7 species that are included in three class. The highest abundance of echinoderms found in mangrove area. The diversity of echinoderms on Balekambang beach were moderate category. The observations of chemical and physical parameters of the aquatic environment and the substrate showed optimal for the life of Echinoderms.