POST WEST MONSOON PLANULAE RECRUITMENT IN DAMAGED COASTAL CORAL OF PANJANG ISLAND JEPARA, CENTRAL JAVA -INDONESIA [302211]

[anonimizat] -INDONESIA

Pujiono W. Purnomo, [anonimizat], Semarang 50275 Indonesia

ABSTRACT. Successfulness of planulae metamorphosis to become juveniles introduced succession toward the formation of a new coral community following a stress. [anonimizat], [anonimizat]. During the first week of June 2013 until the end of October 2013, [anonimizat] 1.5m depths. [anonimizat]- [anonimizat], [anonimizat], depth, turbidity, [anonimizat], as well as inorganic and organic content of the sediment. [anonimizat], Pocillopora and Platygira. [anonimizat]. Planulae recruit considered low with metamorphosis ability to become juveniles only at 5 colonies.m-2.month-1 at the southward and 1.3 colonies.m-2.month-1 at the northward of the island. [anonimizat], i.e., Pseudomonas spp. and Phormidium corallyticum amongst the recruited planulae.

Key Words: [anonimizat], [anonimizat]. Coastal coral community prone to environmental stresses; in one hand these stressors served as a forcing function to survived and formed the community accordingly as it may alter community structure of the reef. [anonimizat], [anonimizat], leaving the diversity of remained species to restructure the system. Planulae recruit is therefore the main concern to recover reef damages.

Bachtiar (2011) reported that survived biological structure of a reef could become the most important seed in recovering the ecosystem since the remaining component, e.g., [anonimizat]. [anonimizat]. [anonimizat] a habitat, for various species. Jepara in Central Java has some remnants of coastal reefs; the one in Panjang Island is in a state of disrepair.

Recruitment is obviously not a [anonimizat]. Larval dispersion over dead coral and on other natural collectors marked the commencement of young juveniles. This is thus important for both local recolonisation (Pearson, 1981) as well as the study of community interconnectivity. Involved within these seral stages is successive courses of microorganisms to survive and thrive, including the meroplanktonic planulae. The whole process provides information regarding response of a particular coral community against physical, chemical, as well as biological stresses, such as sedimentation, hurricane, overgrazing, predation or coral bleaching phenomenon (Hughes et al., 1999). For which, this study aimed at evaluating recolonisation development in a damage coastal coral community in Panjang Island Jepara following post west monsoon, based on some physical and chemical variables along with observation on the seral stages, including survivorship and growth of planulae along a time gradient.

Material and Method

Assessment of Coral Reef Condition

Three stations were established in the southward (06°34’44.21”S 110°37’44.25”E), northward (06°34’21.38”S 110°37’36.71”E) and eastward of Panjang Island (06°34’30.33”S 110°37’53.77”E) from the first week of June to the end of October 2013. Evaluation of reef condition after previous season was conducted at the beginning of the study (June 2013), by referring its coral coverage to the work of Gomez & Yap (1988). Coral identification was observed by means of Line Intercept Transect methods (LIT; English et al., 1994; Veron, 1995) on three transect lines of 30m each held parallel to the coastline in each station.

Figure 1. Panjang Island in Jepara Regency Central Java Indonesia

Bacteria and Periphyton Sampling

Throughout the course of the study, set of 6 material collectors made of natural slate (15 x 15 cm; Figure 2) was set up in the slope of each station. The first sampling was conducted after 3 weeks submersion in the water. Therefore, thoroughly, week counted started at week III and collectors were sampled twice a week for three weeks thereafter.

Figure 2. Slate Collector used in this Study

Samples of planulae were taken by scraping an area of 5 x 5 cm from the slate into a wide-mouth bottle. Under aseptic condition, samples were then separated for periphyton analyses, i.e., fixed with Lugol, whilst for bacteria analyses samples were put into polyethylene plastic bag (Whirpak Nasco, USA) and kept in the cool box for further processed as soon as possible.

Pure bacteria cultures obtained from streak method were used to identify bacteria strain by observing morphological features of the colony followed by biochemical tests (oxidative test, catalase, Hugh-Leison test, H2S, indol, methyl red, Vogen-Proskauer test, nitrate reduction, citrate, sugar, decarboxylase and carbohydrate hydrolysis) according to Holt et al., (1994).

Sedimentation rate was measured by placing sediment traps sampled every 3 weeks. Meanwhile, water temperature, salinity, pH, current speed and direction, depth, dissolved oxygen, nitrate and orthophosphate were collected fortnightly in situ by means of diving gear. Dissolved organic matter was measured in the laboratory according to Walkley & Black (1934) and Gelman et al., (2011) .

Data Analyses

Chi square test with contingency table, coupled by correlation and regression analyses (Gomez & Gomez, 1995) were used to access the relationship between studied biota against the changeable physical and chemical factors in the area.

RESULT

Table 1 showed that, according to Gomez & Yap (1988) coral reef in Panjang Island is indeed not in a good condition when explained by its low coral coverage (<25%).

Table 1.

Coral Cover Percentages in Panjang Island, Jepara

In southward plain of Panjang Island, Acropora and Porites dominated a community comprise of Platygyra and Pocillopora. This community has a low diversity index, i.e., 1.12 and considered low in stability (Table 2). In southward slope however, among the genera found were Porites, Platygira, Pocillopora, Favites, Pavona, Goneastrea and Acropora, which again dominated by Porites, has a slightly higher diversity index, i.e., 1.52, yet still low stability (Table 2). These findings were 10 to 15 % lower than those of Hafiz (2012) and Wismaya (2012) in the previous year; means that one year has elapsed without meaningful recovery.

Table 2.

Number of Colonies and Diversity Index (H’) of Coral Genera in Panjang Island, Jepara

Having been collecting microbial samples from week III until week XVIII, results of total colonies in Table 3 showing the ups and downs of four microbial species growth with an inclination to totally decline both in south- and northward of the island, yet remained high eastwardly. It was also recorded the presence of pathogenic bacteria, i.e., Pseudomonas spp. and Phormidium corralyticum. The first is a fish pathogen (Hatmanti et al. 2009), whereas the latter is a pathogen causing Black Band Disease (BBD) in coral (Richardson, 1996; Frias-Lopez et al, 2003; Sabdono, 2009; Sabdono et al, 2015). Table 3 shown that two Pseudomonas spp. were found in all three stations, whilst P. corralyticum was only found north-south of the island. Moreover, growth in P. corralyticum showing a similar pattern north to south, for which during the first few weeks (week III to week IX) total number of cells in the south was not significantly different to that in the north. However, when in the south cell growth started to decline, i.e., from 7.4 x 103 to 3.9 x 103 cfu/ml/cm2 (week IX to week XII) to zero (week XV – XVIII); the one in the north soaring to its highest number 74 x 103 (week XII) prior to be also decreasing in week XV (11.2 x 103 cfu/ml/cm2) but not went down to zero (1.2 x 103 cfu/ml/cm2, week XVIII, Table 3).

Meanwhile, Pseudomonas bromoutilis started growing in a much higher cell density in the south (15 – 74 x 103 cfu/ml/cm2, week III to IX) than in the north (4.1 – 8.7 x 103 cfu/ml/cm2, week III to IX). After soaring to 87 x 103 cfu/ml/cm2 the one in the north following after growth pattern of the south (week XV to XVIII; Table 3). This density pattern is not the case for P. bromoutilis eastward of the island, which grew steadily toward its peak in week XVIII albeit less dense compared to both the north and the south; a pattern similar to its congeneric Pseudomonas fluorescens, which only found eastward of Panjang Island (Table 3).

Table 3.

Total Bacterial Growth along Time Gradient in Collector in Panjang Island Jepara

Floristic periphyton observed mostly is microorganisms, whereas the faunistic comprised of both micro- and macro-organisms. Community structure indices upon floristic and faunistic periphyton are shown in Table 4.

Table 4.

Community Structure, Indices of Floristic and Faunistic Macro- and Micro-periphyton Recorded from the Collector in Panjang Island (data available on request)

In general, the average figures for microalgal diversity and evennes indices were high (>2.8), indicating a relatively stable environment in balancing interspecific competition amongst various components. Indeed, albeit insignificant, eastward diversity index were slightly higher than both, the north- and southward of the island. Data observation starting from week XV revealed that in the south, some microalgae species disappeared in week XVIII, they were Chaetophora tuberculosa, Amphipleura micans, Cylindrotheca closterium, Diplopsalis lenticulata, Navicula membranaceae, Peridinium sphaericum and Zygnema insigne. Planulae found in these stations survived from week IX to week XVIII (data available on request). Toward the end of the course in week XVIII eastward community member of microalgae periphyton stayed relatively the same; whereas succession in southward was mingled by both filamentous and crustose macroalgae.

In northward stations, only 5 out of 11 species or 45% faunistic macro-periphyton survived toward week XVIII, i.e., Balanus improvisus, Cerithium rostratum, Macropipus arcuatus, Obelia dichotoma, Persicula minuta and Plumaria undulata. Some coral planulae were found in the substrate collector, albeit only stayed for 3 weeks (week VI to week IX); at week XII they were disappeared.

Physical and chemical variables of the water and sediments were within the optimum range for planulae, juveniles and grown up coral. yet some other within the range of direct and indirect destruction. Water temperature 28.5-300C were optimum (Supriharyono, 2009), salinity were at 31-32.5‰ of the optimum range of 31-36‰, clarity were up to the bottom and dissolved oxygen were at 3.61-6.53 ml/l. All these results support the aerobic conditions for optimum coral growth, periphyton respiration, as well as decomposition by the obtained aerobic bacteria. However, high-pressure variables for corals arising from both potential sedimentation and sedimentation rate (Table 5), organic content of the sediment, nitrate and orthophosphate as shown in Table 6.

Table 5.

Potential Sedimentation and Sedimentation Rate in Surrounding Water of Panjang Island

Table 5 depicted a stable potential and relatively high rate of sedimentation in each of study sites, for which the lowest was southward and the highest, was eastward. In turn, stable potential of sedimentation correlated to the organic carbon of the sediment, nitrate and phosphate.

Table 6.

Dissolved Organic Matter in the sediment, Nitrate and Orthophosphate in the water of Panjang Island every 3 weeks (21 d) during the study

Table 6 further indicating significant correlation between sediment organic content and nitrate, i.e., Y = 0.0478 + 0.0095 X (R = 0.89) southward; Y = -0.0916 + 0.0081 X (R = 0.88) northward and Y = 0.1423 + 0.0041 X (R = 0.98) at the eastward of Panjang Island. These simple linear regressions suggesting the continue supply of nitrate resulting from decomposition of dissolved organic matter into the water column.

Present study reported that nitrate in the southward ranged from 0.276 – 0.414 mg.l-1, in the northward 0.291 – 0.410 mg.l-1 and in eastward stations were from 0.375 – 0.530 mg.l-1 subsequently (Table 6), which according to Parson et al (1984) considered very high. Active decom-position of organic matter that yielding in nitrate as nutritive product presumably gave rise to stable periphyton growth in three study sites as sampled from the collectors (Figure 3).

Figure 3. Juveniles of Pocillopora, Acropora, Porites and Platygira from the Collector in Panjang Island. Scale bar 1cm

DISCUSSION

Coral colonisation occurred through several stages depend on several environmental factors. First is reproductive success to produce ample planktonic larvae. Secondly is larval capability to identify and to attach to suitable substrates. Furthermore, settlement urged certain physical and biological requirements, such as substrate type, current speed and direction, adequacy of light, sedimentation load and availability of biofilm covering surface of the assorted substrate, which normally consisted of bacteria and diatom (Sorokin, 1993; Richmond, 1997).

In this study, all ingredients to produce such a biofilm are available from the bacteria community (Table 3). Kioerboe (2003) stated that as an important biological feature, biofilm establishment in corals commenced when organic materials is adequate to support firm attachment of bacteria and other microorganisms upon immersed solid materials, which then grow and reproduce to yield in layer of extracellular polymer called biofilm. In this work, organic material from sedimentation as nutritive source for microorganisms is abundant. At the first week of collector settlement, it brings in organic 1.38 mg.DOM-1.d-1 southward, 2.48 mg.DOM-1.d-1 northward and 3.74 mg.DOM-1.d-1 eastward of the Panjang Island (Table 6). The presence of microorganisms inevitably acts to trigger active process of decomposition, as such that the blanket attracts various periphytonic microalgae to attach. In turn, periphyton produces exudate, excrete and secret which along the decomposition process transformed into nitrate (NO3) and orthophosphate (PO4).

Coral community is a fragile ecosystem, it thrives in low-nutrient environment, so high-level nutrient inevitably jeopardies the coral animals, since its space competition are weaker than macroalgae. Accordingly, Muller-Parker & D’Elia (1997) demonstrated that nitrogen directly affected coral growth, under high nitrogen concentration growth of zooxanthellae population increased. Yet, in excessive amount, nitrogen may cause inverted impact, i.e., declining the coral growth due to competition with macroalgae expansion (Paonganan, 2008).

Bacterial function is imperative in ripening process of this habitat. In the present study, eight heterotrophic bacteria species belong to six genera were identified, i.e., Pseudomonas fluorescens, Pseudomonas bromoutilis, Nocardia spp., Bacillus firmus, Bacillus licheniformis, Desulfomonas pigra, Micrococcus luteus and Phormidium corallyticum (Table 3). They are able of degrading dissolved organic complex and inorganic matters to yield in short and simple materials, e.g., nitrite, nitrate and ammonia, which have important role in commencing biofilm succession (Romeo, 2008). In turn, the biofilm triggered the attachment course of recruited planulae.

Recruitment process in Panjang Island was very poor. In average, colonisation rate was 4 colony.m-2.mo-1 southward, even lower, only 1.0 colony.m-2.mo-1 northward and none in the eastward of the island. Among the recruited juveniles found in the south, composition of the community was comprised of Porites (31.25%), Platygira (12.5%), Acropora (25 %), Pocillopora (31.25%). Acropora (2 colony.m-2.mo-1, 50%) and Pocillopora (2 colony.m-2.mo-1, 50%) were the only found northward of the Panjang Island. Taking into account the dominance coverage of the two species in the north, each was 50%, in comparison to Kisworo et al., (2012) whose highlighting Pocillopora attachment in Panjang Island, this result was significantly low. According to Kisworo et al., (2012), in average Pocillopora has 10-12 colony.m-2.mo-1 excluding the two dominant species in their area of study, i.e., Acropora and Porites.

Rani & Suharsono (2002) in Barrang Lompo, Spermonde Island, Makassar reported that peak reproduction season for A. nobilis ranged from August through October. Similarly, Oliver (1988) suggested that coral breeding occurred ca. 6 months within a year. Moreover, McGuire (1998) stated that coral species occupying areas with less varied annual temperature might reproduce the whole year. Therefore, low colony recruits at the beginning of collector placement (June-August 2013) suggesting that collectors might have yet ready as habitat for settlement due to the lack of time during assignation rather than the lack number of recruits in the water, besides, the high sedimentation rate (Table 5).

Broadcast-spawning corals like Acropora expel eggs and sperm, and the fertilised eggs develop into planulae in the water column. As these sessile corals generally disperse during the planktonic larval stage, their larval characteristics (e.g., survival and settlement rates) are thought to be important for their dispersal. Some studies of coral larval dispersal have focused on the maximum time that larvae can remain viable and settle. Richmond (1997) reported that after spawning, Acropora has only 20 days (3-4 weeks) to live their planktonic competence, whereas Pocilloporidae, which lead a different reproductive strategy, i.e., brooding and has zooxanthellae, performed a longer planktonic stage, ca. 100 days. Nishikawa & Sakai (2005) work in Japan waters recorded that the maximum settlement competency period was lower in planulae of A. digitifera (54 days) than in A. tenuis (69 days); both are much longer than the result of Richmond (1997), despite, for some species like Acropora, time needed for larvae to lead their planktonic life limit their competence.

Diaz-Pulido and McCook (2002) recorded that substrate in coral reef environment might be colonized quickly by filamentous algae, yet succession from filamentous algae to CCA (Crustose Corraline Algae) could take weeks even years to accomplished. Further, they stated that new substrates take 3 months to be suitable for larval attachment. On the other hand, Glynn et al. (1991) reported that as a pioneer, members of the family Pocilloporidae capable of colonising new substrate very quickly. Besides, it spawns all year long, ample to dominate mature coral community.

Brown & Bythell (2005) suggested that mucus on the polyps’ surface is vital for various matter, such as stress resisting, avoiding predation and sediment cleaning. Lenhoff (1974) identified it as high amino acid coral secretion rich in glutathione which coming into contact with organic and inorganic materials in surroundings, decomposed certain compounds that attract planulae to attach (Wilson et al, 2012, Aeby & Santavy, (2006) and these bacteria enriched biofilm continued to function in the polyp metabolism until post spawning and planulae replacement (Ceh, et al, 2012). This phenomenon is common in Acropora tenuis, Pocillopora damicornis dan Tubastrea fulkneri.

In general, this study suggested that planulae recruitment is limited by various environmental factors, which in this case were the dissolved organic matters coupled by high sedimentation rate. In the sampling sites of this study, sedimentation rate ranged between 3.28 mg.cm-2.day-1 in the south to 14.6 mg.cm-2.day-1 in the east. Following Babcock & Mundy (1996), the high rate of sedimentation in their area of study, i.e., 3.1 mg.cm-2.day-1 may halt the recruitment process, either through the decomposition as well as the biological response of the planulae. Positive sign of biofilm formation was also prevented by the presence of pathogenic bacteria, Pseudomonas spp. and Phormidium corallyticum. Hatmanti et al (2009) revealed that Pseudomonas spp is pathogenic in grouper, whereas Phormidium corallyticus is causing BBD (Black Band Disease) in corals (Richardson, 1996; Sabdono, 2009).

Acknowledgements. We are grateful to the Faculty of Fisheries and Marine Science Diponegoro University for funding and logistic support in this study, also our sincere grateful extends to anonymous reviewers for this manuscript improvement.

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