Impact Test Size and Type of Echinometra mathaei as Agent of Bioerosion on Reef Flat

Bioerosion is an activity of various organisms such as erosion and destruction of coral calcium carbonate and become a major factor influencing coral reefs morphology. Bioerosion is influenced by three variables: type of species, size of species and abundance. Seventyfive percent of bioerosion caused by sea urchin. Differences on size and type of sea urchin gave a significant impact to the bioerosion area. This study aimed to examine the influence of the size and the type of sea urchin E. mathaei (type A and type B) on the composition of CaCO3 in the gut content and feces as bioersion agent on the reef flat in Minatogawa Coast, Okinawa-Japan. The organisms used were E. mathaei type A and type B with each type distinguished by size ≥ 30 mm and < 30 mm with three replications. The maintenance was carried out at laboratory for 3 days by observing analysis of the composition of CaCO3 on feces and gut content. It indicates that the composition of CaCO3 as daily bioerosion was caused by E. mathaei. The results showed E. mathaei with diameter ≥ 30 mm was more active than those with diameter of < 30mm and type B was more active than type A in each of the same size. Percentage of CaCO3 in the gut during maintenance in the laboratory was 73% and the other 27% consist of organic and inorganic materials. Daily bierosion E. mathaei type A ≥ 30 mm 166.70 mg.day-1 , type A < 30 mm 77.78 mg.day-1 , type B ≥ 30 mm 126.30 mg.day-1 , type B < 30 mm 116.17 mg.day-1. Daily bioerosion rate E. mathaei was influenced by the type, species, speed of grind, and the size of the sea urchin.


Introduction
Coral reef ecosystem is well known for its biological and genetic diversity.Various activities of the organism as a cause of coral reef structure and constituent coralline algae experiencing bioerosion.Bioerosion is the activity of various organisms that cause calcium carbonate erosion and destruction the building of coral animals (Holmes, 2000).Bioerosion is the process of calcium carbonat removal from reefs or coral colonies by biological processes (Tomascik et al., 1997) and as a major factor that affects the reef building and its morphology.
Organisms that cause frame-building coral reef limestone eroded and broken through the activities were refered to bioeroder (Glynn, 2001).Bioerosion activity on reef structure affects the abundance of carbonate structures from the Precambrian and Cambrian period (Vogel, 1996).This process occurs both mechanically and chemically (Zundelevich et al., 2007;Nava and Carballo, 2008).The rate of bioerosion is also influenced by nutrient concentration related to trophic level (Lescinsky et al., 2002;Pari et al., 2002;Hutchings et al., 2005), substrate density (Schönberg, 2002) and ocean acidification (Wisshak et al., 2012).
Bioerosion on coral reefs is generally caused by the activity of the three groups of organisms, i.e.Parrot fish (Scaridae), sponge (Clionidae), and also sea urchin (Carreiro-Silva and McClanahan, 2001;Brown-Saracino et al. 2007).Although other animals like chiton also has similar activity (Barbosa et al., 2008).Peyrot-Clausade et al. (2000) reported that fish and sea urchin are the most important grazers both at two reefs of La Saline on La Réunion Island (Indian Ocean) and of Tiahura on Moorea Island (French Polynesia).
In addition, microborers, grazers, and macroborers have been reported to contribute in bioerosion rate (Tribollet et al., 2002;Tribollet and Golubic, 2005).However, seventy five percent of the total bioerosion caused by sea urchin therefore, the major bioeroder on coral reef ecosystems is sea urchin.Bioerosion that caused by sea urchin has many aspects, one of significant aspects is the biological and geological aspect, including abrasion activity that make up the holes and caves in the coral (Bak, 1994).
Bioerosion caused by sea urchin usually ranges from 3-9 kg m 2 .year - , it depends on the type of species, the speed of erosion, the size of the sea urchin, and population density of the animals (Mokady et al, 1996;Herrera-Escalante et al., 2005).Significant differences in the size and species of sea urchin will give different impact on the bioerosion area.The rate of bioerosion of sea urchin can be calculated by analysiing gut contents and also feces of the animals (Milss, 2007).
Echinometra mathei is one of bioeroder which are easily found in the Indo West Pacific and live in a way that boring during his life as an adult individuals remain relatively rare in the hole and out of the hole.According to Russo (1980), E. mathei is one of the important bioerosion agents that contributed about 2 to 8% of the total product of bioerosion.In Hawaii, an estimated weight about 4000 grams total weight.m - .year - bioerosion product.Where E. mathei give contribution about 80-325 grams of dry weight.m - .year - .Daily erosion velocity of each individual sea urchin ranged from 0.1 to 0.2 grams in dry weight.m - .year - .According to Downing and El Zahr (1987), from gut contents analysis of E. mathei obtained velocity erosion.day - that ranged from 0.9 to 1.4 grams dry weight.day - .
Sea urchin with a size 30-40 mm has great potential to causing bioerosion 5-10 times higher in populations with half the size.E. mathei has a size of about 19.5 to 40.8 mm and has the ability to perform the erosion of approximately 0.11 to 0.7 mm (Bak, 1994).Along the coastline of Okinawa Island can be found various of sea urchin E. mathaei.This species is divided into 4 types (type A, type B, type C, and type D) based on differences in morphology, ecology, and the characteristics of the embryo (Uehara, 1990;Setyawan et al., 2013).These four types of differences can also be seen from the formation of bioerosion.Suzuki (2005) reported that bioerosion by E. mathaei is an agent that dominates on the island of Okinawa, the difference in size and type affect bioerosion formation, extent, and rate of erosions.E. mathaei type A and type B are dominating Minatogawa coast where the second type has bioerosion rate higher than other types.

Sample collection
Sea urchin, Echinometra mathaei were collected from tide pool on the coast of Minatogawa, Okinawa Island ( N 260 0 07'10.6';E127 0 45'21.5'')on July 2013.This study use type A and type B of of the animals which are commonly found in the area.The samples were brought to the laboratory of the Faculty of Science, University of the Ryukyus, Okinawa, Japan for further experiment.

Laboratory treatment
Laboratory experiments carried out to see the content of calcium carbonate on the gut and feces.Aquarium were made as natural as possible with a range of 30-33 ‰ of salinity, 28 0 C of temperature, 250 lux Fluorescent illuminated for 12 hours, and the water in the aquarium were circulated.Observations were conducted for 5 days.Dead coral that has holes were taken from Minatogawa and dead coral habitats such as E. mathaei (type A and type B) in aquarium.There are four aquariums (three aquarium contained with E. mathaei with different types and sizes), namely: Aquarium A1 (E.mathaei type A ≥ 30 mm), aquarium type A2 (E.mathaei type B ≥ 30 mm), aquarium B1 (E.mathaei type A < 30 mm), and the aquarium B2 (E.mathaei type B < 30 mm ).According to Uehara and Hiratsuka (2007), Echinometra adult size has a diameter of 30-35 mm and feed demand is higher than the size of < 30 mm, while the size of < 30 mm is a condition in which E. mathaei still the Juvenile stage to adulthood and feed consumption is still small.

Gut content analysis of CaCO3 and feces
Analysis of the gut contents and feces CaCO3 compared by type and size.Gut contents and feces were taken and placed in a sample bottle.Then the samples were rinsed with Double Distilled Water (DDW) three times to remove NaOH contained in the sample.Then the samples were dried in oven at 60 o C temperature for 24 hours.Once weighed, given a sample of 2N HCl to remove CaCO3 contained in the sample.After that, the sample were rinsed with DDW three times, dried and then weighed again.Initial weight before HCl is treated with dry weight of feces produced by E. mathaei.The difference between the weight before the treatment with HCl after being given an estimate of CaCO3 contained in the gut contents.

Results and Discussion
Total dry weight of CaCO3 increased by the large size of the E. mathaei.Greatest CaCO3 contained in E. mathaei with a diameter ≥ 30 mm.There are significant differences in the content of CaCO3 in E. mathaei size ≥ 30 mm in size <30 mm.
CaCO3 content of the hull during maintenance in the laboratory is 73% of the amount of gut contents and 25% are other (organic and other inorganic materials).Total CaCO3 in sea urchin gut area bioerosion predictable levels caused by sea urchin.It is of course also linked to the type, sizes, and sea urchin habitat.
CaCO3 content of the feces was 79% of total dry weight and 21% is organic and the other inorganic materials.CaCO3content of the feces is a daily bioerosion caused by E. mathaei.The data showed that the content of CaCO3 in the gut more than in feces.CaCO3 content of gut E. mathaei size ≥ 30 mm had a significant difference to the content of CaCO3 on the feces at the same size, while the size <30 mm CaCO3 content in the gut was not significantly different to the CaCO3 content of the feces.
CaCO3 content of gut E. mathaei type A and type B ≥ 30 mm in diameter greater than the diameter of < 30 mm.Mills et al. (2000) states that the content of the feed on sea urchins increased according to the size of the diameter.In addition, the size and extent Aristotelarn also affects the speed to grind a hole in the reef.This allows for interspecific differences in feeding rate as a limiting factor on the gut of each species variation due to differences in the size and shape of the lanterns are different depending on the species and age of sea urchin (Appana, 2003).Dry weight of CaCO3 on E. mathaei type A and type B with a diameter of each ≥ 30 mm and <30 mm during the observation in the laboratory at an average of 73% of the total dry weight of the gut and the other 27% including organic and other inorganic materials.Research by Milss et al. (2000) in Tiahura reef (French Polynesia) reported that the percentage found in the gut contents of E. mathaei consisting of 73% CaCO3, 20% and 7% of organic material dissolved organic material.Milss et al. (2000) found a similar proportion is 73% CaCO3 and 27% organic matter in the gut contents Echinometra spp.collected from Rottnest Island, Western Australia.The results showed that the rate of daily bioerosion of E. mathaei type A ≥ 30 mm 166.70 mg.day -1 , type A < 30 mm 77.78 mg.day -1 , type B ≥ 30 mm 126.30mg.day -1 , type B <30 mm 116.17 mg.day -1 .Differences bioerosion rate is influenced by the type and size.Bioerosion the rate is almost equal to the rate of bioerosion in previous studies.The rate of E. mathaei bioerosion in the Arabian Gulf is estimated at 90 to 140 mg CaCO3.day - (Dowing and El -Zhar, 1987).Bak (1990) found that erosion caused by E. mathaei of 140 mg.day - on Tiahura.Kukubo (1993) estimate the rate of erosion caused by E. mathaei Mizugama on Okinawa Island reef flat at 109.3 mg.day -1 with an average maximum diameter of 25.3 mm.Meanwhile, Makody et al. (1996) mentions bioerosion by E. mathaei activity in the Red Sea coral ecosystems by 120 mg.day -1 .
The percentage of fecal dry weight content of CaCO3 in type A and type B at an average of 79% of the total dry weight, 21% other materials including organic and inorganic.E. mathaei issued feces with high intensity at night, but during the low intensity (Milss et al., 2005).Inorganic compounds in the feces can be water, gas, mineral salts, and acidbase, while the organic compounds in the feces is in the form of proteins, fats, and carbohydrates (Hiratsuka and Uehara, 2007).The content of the dry weight of CaCO3 in daily feces bioerosion illustrate the magnitude of the daily rate.Measurement of the content of CaCO3 in the feces and gastrointestinal tract as an indicator of sea urchin on the reef bioerosion (Mokady et al., 1996).

Conclusion
Observations and discussion can be concluded that E. mathaei generally E. mathaei size ≥ 30 mm more potential as bioerosion agents compared to the size of < 30 mm.E. mathaei type B with a diameter of ≥ 30 mm as an bioerosion agent highest compared with the type A and the same size.This is evident in the content of CaCO3 contained in the gut and feces.Daily Bierosion E. mathaei Minatogawa Coast namely: type A ≥ 30 mm 166.70 mg.day -1 , type A <30 mm 77.78 mg.day -1 , type B ≥ 30 mm 126.30mg.day -1 , type B < 30 mm 116.17 mg.day -1 .Bioerosion rate differences is influenced by the type, grind speed, and the size of the sea urchin.

Figure 1 .
Figure 1.Total and percentage of CaCO3 during observation in the laboratory.Note : : gut, : feses

Table 1 .
Dry weight ratio of CaCO3 in the gut and feces