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  Paläontologie und Historische Geologie
Letzte Änderung
11.03.2009
 

Distribution and ecology of the Recent ostracods in the Java Sea, Indonesia

(in co-operation with Babinot, J. F (Marseille) and Colin, J. P. (Cestas)).


Abstract. We give a preliminary account of Recent ostracods from the Java Sea. This part of the study is concentrated on the taxonomy of particular species gathered from a single bottom sediment sample taken from off Bali at a depth of 1, 50 m. A total of 34 ostracod species were recovered belonging to 22 genera. The majority of the species determined are well known by previous investigations, however, their taxonomic range is rather confused and in need of modern revision. The fauna is in general widely distributed in the tropical littoral zone of Indo- West Pacific. Only 4 species are shared with the Red Sea and 4 have also been recorded from Caribbean area, only one species is common with the Mediterranean.


Key words: Ostracods - Systematic Biogeography Ecology Bali.


INTRODUCTION

Recent Ostracods from the Indo-Pacific Ocean have been the subject of numerous investigations in the last decades, which have provided a relative complete picture of the variety and complexity of ostracod communities living in this area ( e. g. Hartmann, 1978 and in references cited above, Howe and McKenzie, 1989, Jellinek, 1993, Mostafawi, 1992, Yassini et Jones, 1995, Zhao and Whatley, 1989, Zhao et al ., 1985, Zhao et al ., 2000). The distribution of the ostracod communities in this area is controlled by water temperature, water depth and salinity. Conclusion derived from these studies applied to record of the provincial distribution of shallow water species (Titterton and Whatley, 1988) and to distinction of different ostracodal ecozonations (e. g. Zhao and Wang, 1988). However, information on ostracods from the Java Sea is comparatively inadequate. Moreover, the taxonomic range of many ostracod species is very confused and in need of modern revision. The most valuable contribution is that by Dewi (1997, 2003). She reported numerous species from Bawean Island and South Kalimantan with some associated ecological parameters. In an ecological context, Whatley and Watson (1988) listed communities of genera with environmental affinities characteristic of the Pulau Seribu (Thousand Islands) providing an understanding of regional generic diversity of ostracod fauna. The purpose of this study will be the taxonomical review of the fauna.


GEOLOGICAL SETTING AND SEDIMENTS

The location of the sampling is situated on the Indian Ocean coast of Bali Island, in the Badung Strait separating Bali from the Nusa Penida Island. The Badung Strait is the western branch of the Lombok Strait which separates islands of Bali and Lombok. It is the second most important strait through which water exchange takes place between the Pacific and Indian Oceans. It is also one of the few passages where current measurements have been performed (Chong et al., 12000; Potemra et al., 2002; Potembra et al., 2003; Sprintall et al., 2003). The Badung Strait has an annual mean transport of around 1.7 Sv of the total estimate of 20-30 Sv through the entire Indonesian archipelago (Murray & Arief, 1988).


During May, the beginning of the dry season, the water temperature varied between 25 and 28 C° with peaks exeeding above 30 C°.


Sediments analysed are calcareous bioclastic sands essentially composed of coral debris. Other biological elements are small gastropods, bryozoas, echinoid spines and benthic foraminifers. The finest fraction of the sediments < 200 µm is composed of volcanic sand originated from the 1963 eruption of the Gunung Agung Volcano in the NE part of Bali.


OSTRACOD ASSEMBLAGE

A total of 34 species belonging to 22 genera have been recorded from sample B1 collected in the southern Java Sea. The faunal assemblage is dominated by Auradilus convolutus, Auradilus australiensis, Jugosocythereis elongata Kotoracythere inconspicua, Loxoconcha cf. gracilis, Paranesidea conulifera and Xestoleberis sp. 1. Whereas, Loxoconcha cf . gracilis with 32, 2 % is the most frequent species. Neonesidea schulzi with 6,4 %, Paracytheridea remanei with 2,6 % and Jugosocythereis deltoids with 1,7 % are the next dominant species. The remaining taxa are rarely represented, making up only 0,4-1,3 % of the population.


There is a high level of faunal affinity between the Java Sea and Indian Ocean (35,2 %). Four species ( Keijia demissa, Kotoracythere inconspicua, Paracytheridea remanei and Triebelina sertata) recorded from the study area are common with the Red Sea, but of these only T. sertata penetrated into the Mediterranean. Auradilus convolutes, Kotoracythere inconspicua, Keijia demissa and Triebelina sertata are also well-represented from Caribbean region. Ornatoleberis morkhoveni and Triebelina pustulata appear to be endemic to the Java Sea and immediately adjacent costal areas. Some species, e. g. Tanella ochracea and Paranesidea nodulifera , range up the moderate climatic zone of North new Zealand and appear to be at the southern limit of their distribution. The absent of fossil evidence outside the Indo-West Pacific suggests that the Indo-West Pacific is the locus of origin of these taxa. They achieved their present-day distribution only recently by man-induced dispersal (Witte et van Harten, 1991, Witte, 1993a-b). However, Titterton and Whatley (1988) consider the oceanic currents as the major factor of the passive transoceanic distribution. Teeter (1973) concluded that these taxa were inadvertently transported by tankers in ballast or in fouling overgrowth attached the hull. However the background of this dispersal may be, one is obvious that increasingly more organisms (fauna and flora), especially micro-organisms are transported in ballast water by merchant ships, which contributes to bio- contamination of the oceans.


Papers


Mostafawi, N. (2001): How severely was the Persian Gulf affected by oil spills following the 1999 Gulf war?. Environ.Geol, 40 (10): 1145-1191.


Mostafawi, N. (2002): A revision of selected ostracod species from Uliczny 1969 (Pleistocene; Cephalinia, Greece). Rev. Esp. Micropaleont., 34 (3): 315-330.


Mostafawi, N. (2003): Recent Ostracods from the Persian Gulf. Senckenberg. maritima, 32 (1/2): 51-75.


Mostafawi, N & Freiwald A. (1998): Ostracods in a Cold-Temperature Coastal Environmen, Western Troms, Northern Norway: Sedimentary Aspects and Assemblages. Facies, 38: 255-274.


Colin, J. P. Mostafawi, N. & Babinot, J. F.: A preliminary account of Recent ostracods in Java Sea off Bali, Indonesia. Rev. Micropal. (in press).