Galaxea, Journal of Reef Studies (Special Issue): 195-200（2013）

Proc 2nd APCRS

Distribution and diversity of the soft coral family (Coelenterata: Octocorallia) in Lembeh Strait, Indonesia

Michael P. JANES1, *

1 AquaTouch, 12040 North 32nd Street, Phoenix, Arizona 85028 USA

* Corresponding author: M. P. Janes E-mail: [email protected]

Abstract The Xeniidae are a major component of benthic coral reef communities in Lembeh, Indonesia. A two- Introduction week survey of the xeniids from this region was conducted. Scuba collections were carried out to a depth of 25 meters. The Xeniidae soft inhabit warm, shallow tropical A total of 48 samples were examined, encompassing a waters from the coast of East Africa, Red Sea and South­ variety of species found in Lembeh Strait. Representatives east Asia to the Central Pacific. Their presence in the of the genera , Cespitularia, , San­ Indo-Pacific and the islands of Indonesia has received sibia, , and were recorded using micro­ limited investigation (Tomascik et al. 1997). Most pub­ scopic analysis. Visual estimates were made of the under­ lished descriptions were recorded prior to the twentieth water abundance and distribution of these genera. Three century (Quoy and Gaimard 1833; Dana 1846; Schenk habitats containing xeniids were identified. Sand slopes, 1896; Ashworth 1899). Later, Verseveldt (1960) identified which were limited to the genera Anthelia, and Xenia. five species collected during the Snellius expedition. In Hard substratum patch reefs supported the greatest diver­ 1996 Imahara published a review of Indonesian octocorals sity, which included communities of Anthelia, Cespitularia, including members of the Xeniidae. Heteroxenia, Sansibia, Sympodium, and Xenia. The genera During 2009 a two-week survey was conducted through­ Cespitularia, Heteroxenia and Xenia were found to out Lembeh Strait, Indonesia. The focus of this fieldwork colonize reef walls. Only one colony of Sansibia and one was to collect the diverse genera and species of xeniid colony of Sympodium were recorded in this survey. octocorals, identify which habitats these genera are Abundant assemblages of Xenia were found to occur at associated with, and determine their relative abundance. depths of 3-25 meters, primarily on sand slopes. Inter­ This is the first time such a detailed survey of xeniid estingly, most colonies of Cespitularia and Heteroxenia octocorals has been conducted in Indonesia. were observed below 10 meters on both patch reefs and Field identification of xeniids to the species level is not reef walls. possible given the need for modern scanning electron microscopic (SEM) analysis of the sclerites or skeletal Keywords , Octocorallia, Xeniidae, Soft Corals, elements. Samples were collected and examined in the Lembeh, Indonesia laboratory following the in situ observations. These sam­ ples are currently housed in the collections of the Cali­ fornia Academy of Sciences (CAS). Detailed species descriptions derived from classical , SEM pre­ 196 Janes: Distribution and diversity of the soft corals in Indonesia parations of sclerites and molecular analysis is currently along the outermost aboral row. Sclerites were isolated in preparation (Janes et al.). The preliminary identification from the tissue of the polyps and stalk when present and results and field data are presented below. wet mount preparation was used for microscopic exami­ nation. Compound microscope observa-tions were made at 100-power, which consisted of 10-power oculars com­ Material and Methods bined with a 10-power objective. Colony and sclerite de­ tails observed during microscopic examination were re­ Field surveys were conducted at each station (Fig. 1). corded with digital photographs. Each station location was recorded with GPS data (Nikon Corporation, Tokyo, Japan) at the mooring location of the boat. Scuba diving equipment was employed to a maxi­ Results mum depth of 25 meters. Distribution data were recorded by visual estimates along each site. Sites were categorized Distribution as sand slope, rocky patch reefs, or reef walls. Additionally, Xeniid octocorals were observed to occur on hard sub­ photographs were taken with an Olympus C8080 camera stratum throughout Lembeh Strait. There were three hab­ (Tokyo, Japan) at each site. Environmental parameters itats supporting coral development identified in this sur­ were recorded which included substratum type, depth of vey: sand slopes, patch reefs and reef walls (Fig. 2). specimen if collected, depth range where a particular Sloped sandy bottoms were predominately found in the genus occurred, commensal organisms on a colony if pre­ central and southern portions of the Strait. Although they sent, and nearby scleractinan or octocoral colonies grow­ are primarily comprised of volcanic sand, some of the ing in the same habitat. slopes occurring around patch reefs were constructed of Analysis of samples collected during the survey was coral sand and course rubble. In the sand zones small rock conducted in the laboratory (AquaTouch, Phoenix, Ari­ outcroppings or dead coral skeletons served as the zona, USA). Generic affiliation of each sample was con­ substratum for Xenia, Heteroxenia, and Anthelia. They firmed by morphological examination with a dissecting were found to occur at depths from three to fifteen meters. microscope at 20-power. Measurements were taken to the At the southern limits of the Lembeh Strait xeniid pop­ nearest 0.01 mm with the use of a micrometer. Colonies, ulations are non-existent. The port city of Bitung located tentacles, and pinnule sizes were measured. Polyps were on the northern shore of North Sulawesi has a sixty-meter examined for the number of pinnule rows and pinnules deep shipping channel that eliminates substratum for coral settlement. Likewise, along the shoreline at the southern end of Lembeh Island both new resort development and anthropogenic disturbances have eliminated xeniids from the coral sand slopes of this area. Along the central portion of the Strait, patch reefs were present within ten meters of the shore in some areas. The patch reefs contained the largest assemblages of xeniids. Anthelia, Cespitularia, Heteroxenia, and Xenia were found to inhabit depths of four to fifteen meters. Heteroxenia and Cespitularia colonies were most prevalent below ten meters. Both Sansibia and Sympodium were nearly absent with only one colony of each recorded. Live coral cover­ age was high on all patch reefs. In some areas xeniids dominated the reef while in others they were intermixed Fig. 1 Map of the Survey site with sampling stations. with other octocorals belonging to the genera Sarcophyton, Janes: Distribution and diversity of the soft corals in Indonesia 197

Abundance Each of the genera in Table 2 was assigned to one of four abundance categories: dominant, abundant, sporadic and rare after Benayahu (1995), which are illustrated for each of the three coral reef habitats. Relative abundance estimates revealed the largest populations of all genera occur on patch reefs. Xenia was the only genus present in all three habitats. Species of this genus were most domi­ nant on sand slopes, very abundant on patch reefs and only occur sporadically along reef walls. Anthelia species were abundant on sand slopes but only occurred spo­ radically on patch reefs. Heteroxenia dominated reef walls, Fig. 2 Distribution of xeniid habitats in Lembeh Strait. yet species of this genus were only found occasionally in aggregations on patch reefs. Cespitularia was found to be common on most patch reefs, abundant along reef walls, Sinularia, Klyxum, and Briarium. but absent in sand slope habitats. Both Sansibia and The northern limits of Lembeh Strait are comprised of Sympodium were observed to be rare in Lembeh Strait reef walls. In areas where graded slopes or ledges occur (Table 2). Only one colony belonging to each genus was populations of Cespitularia, Heteroxenia, and Xenia were found, Sansibia on a sand slope and Sympodium on a recorded. Colonies range in depth from five to twenty-five patch reef. Notably absent on sand slope habitats were the meters. However, both Cespitularia and Heteroxenia are genera Cespitularia, Heteroxenia, and Sympodium. most abundant below ten meters. Heteroxenia is a di­mor­ phic genus and was recorded visually by the presence of siphonozooids. Although not all colonies within a popu­ Discussion lation exhibited siphonozooids and at least one large colony showed evidence of siphonozooids in half of the Distribution and Abundance colony, bisected uniformly across the capitulum. The objective of this survey was to investigate the Xeniidae fauna of Lembeh Strait. Patch reef habitats Diversity located primarily in the central portion of the strait were A total of twenty-nine species from six genera were observed to have the highest diversity and abundance of recorded from this region of Indonesia (Table 1). One xeniid genera. The limited presence of Sympodium col­ species each from the genera Cespitularia, Sansibia and onies in Lembeh might be due to their slow membranous Sympodium has been identified. Four species of Anthelia, growth, which has been observed in the Red Sea (Reinicke four species of Heteroxenia, and eighteen species of Xenia 1997). It is likely the hard substratum and shallow depths have been identified. A detailed account of the species contribute not only to xeniid populations but other zoo­ richness of xeniids from Lembeh Strait is forthcoming xanthellate octocorals, especially the Sinularia and Sarco­ (Janes, Reynolds, and McFadden, in preparation). Pre­ phyton species observed here. Mid and outer shelf reefs of viously ten species of Xenia (Dana 1846; Schenk 1896; the Great Barrier Reef have also exhibited abundant Ashworth 1899), Anthelia glauca (Lamarck, 1816) iden­ populations of xeniids (Fabricius 1995), which has been tified by Verseveldt (1960) and Cespitularia multipinnata attributed to the fast-growing “fugitive” nature of some (Quoy and Gaimard 1833) were noted to occur in the members of this family. Indonesian Archipelago. In sandy-sloped areas Anthelia and Xenia were recorded to be quite prolific. Both of these genera are able to pro­ duce runner like stolons, which aid in asexual propagation 198 Janes: Distribution and diversity of the soft corals in Indonesia

Table 1 Species identified from Lembeh Strait, Indonesia Table 2 Generic affiliation, distribution and abundance es­timates of the xeniid octocorals of Lembeh Strait, Indo­ nesia.

vertically angled inclinations. Observations of Xenia and Heteroxenia in Thailand indicated that these genera occur on similarly inclined substrates (Chanmethakul et al. 2010). The reef walls also contained a lower diversity of scleractinian and octocoral species than other coral habi­ tats. It is highly probable that reduced competition for settlement space and clear oceanic waters (Fabricius & Alderslade 2001) contribute to the success of Cespitularia and Heteroxenia in this habitat.

Diversity A survey of xeniid species recorded from the literature was conducted (Table 3) for comparison with the relatively high number of species recorded from this survey. Among the biogeographic distribution of the family Xeniidae, Lembeh, Indonesia now represents the third highest diver­ sity of species and it is among the highest number of genera recorded for a location. The Philippines has the most recorded species but this is only from one published account (Roxas 1933). The Seychelles (Janes 2008) and (Benayahu 2004). Further, the often heavily pinnate Taiwan (Benayahu et al. 2004) both record the same polyps can assist in sediment removal (Schlichter 1983), number of species present and similar generic diversity. which is beneficial for colonizing sandy bottom habitats. Although Australia only exhibits thirteen species from The species of Sansibia also observed here has essentially five genera (Verseveldt 1977) a thorough investigation the same morphological characteristics as Anthelia, so its has not yet been conducted in this area (P. Alderslade, presence in this habitat is not surprising. personal communication). Interestingly, records from Vertical reef walls located at the northern part of Lembeh Japanese waters reveal seventeen species recorded from 6 Strait support abundant assemblages of Cespitularia and genera. This is likely due to the warm Kuroshio current, Heteroxenia, with smaller populations of Xenia. The which carries larvae up from Indo-Pacific waters (Kayanne benthic structure is comprised of limestone shelves or et al. 2004). Three locations associated with environmental Janes: Distribution and diversity of the soft corals in Indonesia 199

Table 3 Biogeographic diversity of xeniids. USA. I am grateful to Danny Charlton, Catherine Jacobs and the staff of Lembeh Divers for logistical support and assistance during my stay in Lembeh.

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