SEDIMENT REMOVAL ACTIVITIES of the SEA CUCUMBERS Pearsonothuria Graeffei and Actinopyga Echinites in TAMBISAN, SIQUIJOR ISLAND, CENTRAL PHILIPPINES

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Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

SEDIMENT REMOVAL ACTIVITIES OF THE SEA CUCUMBERS Pearsonothuria graeffei AND Actinopyga echinites IN TAMBISAN, SIQUIJOR ISLAND, CENTRAL PHILIPPINES

Lilibeth A. Bucol1, Andre Ariel Cadivida1, and Billy T. Wagey2*

1. Negros Oriental State University (Main Campus I) 2. Faculty of Fisheries and Marine Science, UNSRAT, Manado, Indonesia *e-mail: [email protected]

Teripang terkenal mengkonsumsi sejumlah besar sedimen dan dalam proses meminimalkan jumlah lumpur yang negatif dapat mempengaruhi organisme benthic, termasuk karang. Kegiatan pengukuran kuantitas pelepasan sedimen dua spesies holothurians (Pearsonuthuria graeffei dan Actinophyga echites) ini dilakukan di area yang didominasi oleh ganggang dan terumbu terumbu karang di Pulau Siquijor, Filipina. Hasil penelitian menunjukkan bahwa P. graeffei melepaskan sedimen sebanyak 12.5±2.07% sementara pelepasan sedimen untuk A. echinites sebanyak 10.4±3.79%. Hasil penelitian menunjukkan bahwa kedua spesies ini lebih memilih substrat yang didominasi oleh macroalgae, diikuti oleh substrat berpasir dan coralline alga.

Kata kunci: teripang, sedimen, Pulau Siquijor

INTRODUCTION the central and southern Philippines. These motile species are found in Coral reefs worldwide are algae-dominated coral reef. declining at an alarming rate due to P. graffei occurs mainly on natural and human-induced factors corals and sponge where they appear (Pandolfi et al. 2003). Anthropogenic to graze on epifaunal algal films, while factors include overfishing, pollution, A. echinites is a deposit feeding and agriculture resulting to high holothurian that occurs mainly in sandy sedimentation (Hughes et al. 2003; environments. These two species also Bellwood et al. 2004). Sedimentation is differ on their diel cycle since also a major problem for reef systems A. echinites is observed only at night (Hallock, 2001). Sediments can while P. graffei is active during daytime. smother coral colonies and other reef The main aim of this study was organisms (Rogers 1990), which in turn to evaluate the differences in the may affect marine biodiversity and amount of sediments removed by two fisheries (White et al. 2000). species of sea cucumbers (P. graeffei Sea cucumbers or sand fishes and A. echinites) in a shallow reef are well-known as “vacuum cleaners” of dominated by macroalgae with patches the sea because they consume large of live hard corals. This study is of high quantities of sediment. These significant addition to the growing organisms promote bioturbation and knowledge of the ecology (with recycling of organic material within the emphasis on sediment removal) of sediment (Wheeling et al. 2007). Two these species of sea cucumbers. In holothurians species Pearsonuthuria addition, most studies done on the graffei and Actinopyga echinites, are macroinvertebrates in the study area found throughout the Indo-Pacific focused on abundance (Wagey et al. region (Clark and Rowe, 1971) and are in high abundance in certain areas of

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

2017) and harvest (Wagey & Bucol, entire reef area is 6.68 hectares but in 2016). this study only the reef flat (2.13 hectares) with depth from 1.5 to 5 MATERIALS AND METHODS meters was visited. The samples were obtained in an algal dominated portion Description of The Study Area of the reef. Two species of sea The study was conducted in cucumbers, P. graffei and A. echinites Bobaboc Reef (9.186558°N, were used in this study. Data were 123.447785°E) located in Sitio Lapac, collected during day (0730-1700) and Brgy. Tambisan, San Juan, Siquijor night (1930-2100) for P. graeffei and A. (Fig. 1). The site is recognizable by a echinites, respectively. limestone outcropping (0.14 ha), also known as an emerged fossil reef. The

Figure 1. Locator map showing location of the study site.

The Following Hysico-Parameters vs/philippines.php#BoholSea_Philippin were Taken In Situ during The Entire es) from the satellite virtual station for Sampling the entire Bohol Sea.

Water temperature data during Sediment Removal by Sea the sampling were determined using a Cucumbers field thermometer (atmospheric and subsurface). Salinity, on the other hand, Specimens of P. graffei and A. was determined with the use of hand echinites were selected within the held refractometer. Depth was research area. The animal was measured using a dive computer carefully moved not to disturbed the (Suunto®). Aside from an in situ sediment. All sediments within an area measurement of sea surface of 25cm or 5cm x 5cm quadrat (each temperature (SST), additional data on immediately before the mouth and after SST for the entire year was the anus) were removed using a downloaded (freely accessible at suction generated by 60 ml syringes. http://coralreefwatch.noaa.gov/satellite/ Typically 3-4 syringes were suctioned and were placed in labeled plastic

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

Figure 2. A sample photo of sea cucumber P. graeffei measured using the software Optimas.

bottles. All the samples obtained were filtered using a filter paper and the transported to the Biology Laboratory of filtrate oven-dried for 24-48 h to Negros Oriental State University constant weight. After which dried mass (NORSU), Main Campus I in were determined for each sample using Dumaguete City. The sample the following equation: sediments from each quadrat were

Measurement of Length using the image analysis software (Optimas). To determine length (in cm) of the sea cucumbers without disturbing RESULTS (most sea cucumbers retract when touched or disturbed) them while Physico-Chemical Parameters feeding, underwater photograph was During the sampling in March taken for each individual. A plastic slate 14-15, 2015, the following data on (used to record other field data with physic-chemical parameters were attached ruler) was placed about 5-7cm taken, consistent with at least three away from the sea cucumber to serve readings. Atmospheric temperatures as calibration for further measurement

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

Figure 3. Substrate preference (in % cover) of the two sea cucumber species in the study site. Error bars indicate standard error (SE) from the mean. ranged from 26-27°C while sub-surface sand (23±11.2%) appears second as temperature ranged from 26-27°C. preferred substrate for A. echinites. These values were similar to the This might be due to the burrowing satellite readings by the NOAA habit of this species on sand at daytime (National Oceanographic and and emerged at night time among Atmospheric Administration) during the macroalgae to feed. days of the sampling. Following months from March to Sediment Removal early May 2015 indicate warming sea Figures 3 and 4 show the surface temperatures. Salinity readings sediment removed (expressed in mean (33-35‰) were typical of marine waters ± %) by the two sea cucumber species. without any influence from freshwater P. graeffei removed as much as source. The nearest freshwater outflow 12.5±2.07% while A. echinites removed is located about 5 kilometers away in 10.4±3.79% of sediment. These values Poblacion, San Juan and has very were notably lower compared to those relatively low volume flow to influence reported by Nestler et al. (2014) for P. the study site. graeffei in Agan-an Marine Reserve,

Sibulan, Negros Oriental. Unlike most Substrate Preference of the coral reefs in the western side of By examining the substrate type Siquijor, including our study site, it underneath each of the sea cucumbers should be noted that Nestler’s site is subjected to this study, fleshy proximate to dense population and river macroalgae (70.8±8.7% Standard Error discharges. For this reason, the or SE althroughout this report for P. sediments located before the mouth of graeffei and 64.3±15% for A. echinites) the two sea cucumber species reached were the most dominant substrate 20 mg/cm2. According to Nestler (Figure 3). The rest of the substrates (2014), as little as 12 mg/cm2 amount of (live coral, rock, etc) were less sediment can have damaging effects on preferred by both species, although the coral.

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

In this study, the sediments above, these sea cucumbers ingested before the mouth only had mean mass about 10-12 % of the sediment, which of 9.8±1.75 mg/cm2 and 7.9±0.7 might also explain the reduced mg/cm2, for P. graeffei and A. echinites, sediment mass after the anus of most respectively. In addition, as shown of our samples (Figure 5).

Figure 4. Mean % removed sediment of P. graeffei (N=22) and A. echinites (N=10).

Figure 5. Mean sediment mass (mg/cm2) before the mouth and after the anus of P. graeffei (N=22) and A. echinites (N=10).

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

DISCUSSION CONCLUSION AND RECOMMENDATIONS The two species included in this study (P. graeffei and A. echinites) are This study provides some relatively common in the algal beds information on the sediment removal throughout their range in the Indo- ability of two sea cucumber species Pacific region (www.sealifebase.org, (one active during day time, P. graeffei 2015). While P. graeffei have been and one active at night time, A. regarded to feed on excess sediment in echinites) in an algae-dominated reef in the coral-dominated reef (Nestler et al. Tambisan, San Juan, Siquijor. Although 2014), thereby benefitting corals in the P. graeffei has been regarded as reef process, very little is known about its species, this study documented that sediment-removal impact in algae- this species prefers fleshy macroalgae dominated reef. It should be noted that as substrate. It is highly possible that an algal-dominated state of coral reefs the individuals encountered were is expected to occur on a global scale mostly juveniles. Larger individuals (Hughes et al. 2003, 2007; Bellwood et (adults) found in deeper (>5m) parts of al. 2011) as a direct result of excessive the coral reef were not included in this nutrient input and overfishing. study. It is highly possible that larger In this study, both species were individuals may also have higher able to remove sediments amounting to sediment removal compared to smaller at least 10%. Although this figure is six individuals. times lower compared to an earlier We recommend that the number study done by Nestler et al. (2014) in of samples be increased and should Agan-an Marine Reserve in Negros include a wider range of size classes. In Oriental. This might be caused by some addition, the temporal (seasonal) and other factors including size differences spatial variation should also be of the sea cucumbers. It is possible that considered for future studies. most of the individuals subjected to this Furthermore, some of the physic- study are mostly juveniles (13 cm for P. chemical parameters (atmospheric and graeffei and 7 cm for A. echinites) all in sub-surface temperatures, salinity, etc) depths lower than 3m while most of should be monitored year-round. those in Agan-an Reserve were more than 30 cm in length and found at ACKNOWLEDGMENTS depths of 12-15 meters (Nestler, J. We would like to thank the following pers.com). individuals for their help during the Given that there is no primary conduct of this study. Dr. Esther E. cause of sedimentation such as run-off Carumbana, Chairman of the Biology from agriculture and in the absence of a Department and our adviser, is deeply river nearby, there is only a small thanked for her valuable suggestions amount (below 10 mg/cm2) of sediment on the research topic and methodology. available for the sea cucumbers (before Dr. Edwin Romano, chairman of the mouth the mouth). According to Chemistry Department, for allowing us Fabricius (2005), corals can be to use the laboratory. Mr. Noe Bucol negatively affected by sediments as low assisted during fieldwork. as 12 mg/cm2. This study parallels to the findings of Nestler (2014) that sea LITERATURE CITED cucumbers reduce the amount of sediment or at least maintains the level Bellwood, D. R., Hughes, T. P., Folke, below the potential damage threshold. C., Nyström, M. 2004. Confronting the coral reef

Jurnal Pesisir dan Laut Tropis Volume 1 Nomor 1 Tahun 2018

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