Analysis of water quality status and water carrying capacity for the development of intensive technology vaname shrimp ponds in Bulukumba District, South Sulawesi Province, Indonesia

. With superintensive technology, Vannamei shrimp ( Litopenaeus vannamei ) farming can increase shrimp production. Shrimp production in superintensive ponds can reach 50 tons per hectare, equivalent to 60 years of production in traditional technology. However, high stocking density with feeding can result in the waste of organic matter into the environment at the time of water change. Sustainable intensive ponds can stand to achieve qualification since their development exists based on water carrying capacity. This study aims to analyze the status of water quality and determine the carrying capacity of waters for developing intensive ponds of vannamei shrimp in Gantarang and Bontobahari Districts, Bulukumba Regency. The results showed a change in water quality status based on distance from the beach and the season. In Gantarang District, intensive pond development can still be carried out based on the oxygen and nitrogen carrying capacity of waters of 56 ha and 110 ha, respectively, while in Bontobahari District, there are 55 ha and 109 ha, respectively.


Introduction
Shrimp farming is currently an overgrowing industrial sector because the demand for shrimp is getting higher in the global market to meet food needs due to the rapid growth of the world population.Acceleration of shrimp production increase can be done by applying intensive technology.To ensure the continuity of intensive pond cultivation activities in an area, it is necessary to know the environment's carrying capacity.[1] explained that the carrying capacity of the environment is the maximum biomass of cultivated species that can be supported without violating the maximum impact on the biomass and its environment, [2] Carrying capacity is the level of use of resources by either humans or animals that can be maintained in the long term.[1] explained that the carrying capacity of an area can decrease due to human activities that produce waste or natural damage, such as natural disasters.Nevertheless, the carrying capacity can be increased through proper area management.
The carrying capacity of the aquatic environment for intensive pond activities is very dynamic due to the continuous discharges of organic and other anthropogenic waste in the aquatic environment.Organic waste will directly affect the carrying capacity of water as a source of raw water for aquaculture activities in intensive ponds.[3] that environmental pollution by organic waste contains nitrogen (N) and phosphates (P) sourced from intensive and super-intensive shrimp ponds because the use of such feed is a severe problem in the development of intensive and super-intensive technology shrimp in Indonesia, [4] The amount of feed wasted into the environment can even reach 24,32% of the total feed used during the shrimp rearing period.[3] High organic waste from super-intensive ponds due to a large amount of feed wasted during cultivation due to unachieved feeding efficiency, the presence of feed that is not digested by shrimp that is wasted through feces, and shrimp excretion during maintenance.It illustrates the importance of determining the carrying capacity of water.[2] Explaining that carrying capacity is an essential concept for ecosystembased management that helps set the upper limit of aquaculture production.The carrying capacity for any sector can be defined as the level of use of resources by humans or animals that can be maintained in the long term by nature.[1] Defining carrying capacity is the maximum biomass of a cultured species that can be supported without violating the maximum impact on its biomass and environment.The carrying capacity of the aquatic environment can be calculated based on the approximation of oxygen concentration (DO) in the waters.[5] N-total and P in feed can be used to calculate the carrying capacity of waters for shrimp farming and their potential impact on the environment.
The environment has limited carrying capacity; therefore, improvement and management of resource systems are needed, along with conserving resources and economic change structures.[6], the environment's carrying capacity is not fixed, depending on technology, preferences, the structure of production and consumption, and the interaction between the physical and biotic environment.[7], the concept of carrying capacity includes four aspects: physical, production, ecology, and social carrying capacity.
[8], the flushing rate mainly controls the carrying capacity of water decided on areas with slow water circulation dispersal of waste from cultivation sites close to cultivation sites.In addition, cultivation expansion, stocking density, and poor environmental management will reduce the survival of cultivated commodities.It goes on to say that the carrying capacity of water depends on the capacity of water bodies to assimilate pollutants.It is also noted that dissolved oxygen is one of the most critical factors for the growth and livelihood of cultured organisms.
The carrying capacity of the waters will provide information on the optimum intensive pond area that can still be developed.In addition to carrying capacity, the distance factor of raw water intake from the superintensive pond inlet towards the sea affects the amount of operational costs in shrimp cultivation.Hence it is essential to identify the level of water quality based on the distance from the beach.The existence of data and information on the carrying capacity of waters and water quality levels based on distance from the coast will facilitate intensive pond development strategies in Bontobahari and Gantarang Kabuapten Districts, Bulukumba, South Sulawesi Province, Indonesia.
The importance of environmental carrying capacity should be the first aspect to consider in developing a sustainability strategy for intensive pond development in Bulukumba Regency.The cultivation practice in the Bulukumba Regency's coastal areas still ignores the aspect of environmental carrying capacity.Along with the rapid development of ponds in Bulukumba Regency, especially in Gantarang and Bontobahari Districts, research has been conducted that aims to analyze the status of water quality and determine the carrying capacity of waters for the development of intensive vannamei shrimp ponds in Gantarang and Bontobahari Districts, Bulukumba Regency.

Water Quality Sampling
Water sampling was conducted in the waters of Gantarang District and Bontohahari District.Water sampling was based on intensive pond beds in the two sub-districts.In the waters around Gantarang District, water sampling points are made transects parallel to the coast in as many as 15 points.Each point's position is arranged to represent the actual state of the entire water.Furthermore, each transect was made of three perpendicular repetition points of the beach with distances of 100 m, 300 m, and 600 m; hence 45 water samples were obtained from the waters of Gantarang District (Figure 1).Meanwhile, in the waters of Bonto Bahari District, 12 points were made parallel to the coast with a repeat of 3 points perpendicular to the beach with a distance of 100 m, 300 m, and 600 m with a total of 33 water samples (Figure 2).[9], determination of distance from shore by transect approach following instructions English.
Water quality parameters measured directly in situ using YSI Pro Plus are dissolved oxygen (DO), salinity, and pH.While the collection of water quality samples is used for ammonia concentration analysis (NH3-N), nitrate (NO3¬-N), phosphate (PO4), total organic matter (TOM), and Total suspended solid (TSS).The methods and tools used for water quality analysis are presented in Table 1.The results of the quality analysis were then carried out by the Kruskal Wallis Test (H-Test) to determine the difference in water quality at a distance of 100, 300, and 600 m from the water coast around Gantarang and Bontobahari Districts.Furthermore, the Mann Whitney Test (U-Test) was also carried out to determine the difference in water quality of the waters of Gantarang and Bontobahari Districts.[15], water quality data is also analyzed to determine water quality levels by station.The results of the water quality level analysis are analyzed descriptively.Determination of water quality levels by station and distance using Rating Index analysis namely: IRi = 100 Xi / Xs (If the value of the water quality factor is higher than the standard value, the better).IRi = 100 Xs / Xi (If the water quality factor value is lower than the standard value, the better).Where: IRi = Water Quality Rating Index (i) Xi = Water Quality Factor Values (i) Xs = Standard value of water quality factor (i) Value IRi >100 good category and <100 bad category.

Carrying Capacity of Waters c.1 Carrying Capacity Based on Total Nitrogen
Total nitrogen data is obtained by calculating organic waste load during the shrimp production process (internal loading) and anthropogenic (external loading).Waste from aquaculture activities results in nutrient enrichment (hypernutrification) in waters.[16], the degree of hypernutrification is determined by the water body's volume, flushing rate, and tidal fluctuations.The approach uses 4 equations.Each of these approaches is: The following calculation is to calculate the concentration (N1p) of the nutrient enrichment results associated with the nitrogen value (Ammonia, NH3-N) water quality standards for aquaculture (Kep-51/MENLH/2004) to obtain the optimum capacity value of aquaculture production (Prod-opt) with the understanding that the concentration value (N1p) comes from shrimp production waste (per ha of superintensive shrimp ponds).Anthropogenic does not exceed quality standards.[17], optimal production can be estimated by the equation as follows: Prod-opt (ton) = (Nbm)/( N1p) Information : (Nbm) = (N) Water Quality Standards for Aquaculture (0.3 -1 mg/L) ammonia (NH3-N) Required.(N1p) = Concentration (N) anthropogenic shrimp production waste from nutrient enrichment.[18], determination of the carrying capacity of waters based on the availability of dissolved oxygen is the difference between the minimum dissolved oxygen concentration (O) desired by organisms (Oin) and the concentration of oxygen available in the waters (Oout).Minimum desired dissolved oxygen level for marine life (Oout) = 4 mg/L.If the volume of water (Qo m 3 ) is known, then the total oxygen (O2) available in the waters for 24 hours (1.440 minutes/day) is :

c.2 Carrying capacity based on total oxygen
= Qo m 3 /min x 1.440 min/day x (Oin -Oout)g O2 / m 3 = A g m 3 /day/1.000= B kg O2 Information: Qo = volume water (m 3 ) Qin = concentration of dissolved oxygen in water bodies (mg/l) Oout = minimal oxygen concentration required by fish (mg/L) 1.440 = number of minutes in a day The oxygen concentration needed to decompose 1 kg of organic waste is 0.2 kg O2.

Water Quality
Water quality conditions based on their distance from the coast A = 100 m, B = 300 m, and C = 600 m Gantaran and Bonto Bahari sub-districts are presented in Table 2 and Table 3.
The tables show that temperature, salinity, pH, and dissolved oxygen are still in natural conditions.Nitrate and phosphate concentrations at distances of 100 m, 300 m, and 600 m in the waters of Gantarang and Bonto Bahari sub-districts have shown higher values than concentration standards for marine life.The concentration of BOT concentration has been above 60 ml/L.The water temperature in the waters of Gantarang District fluctuates, where the highest temperature is at a distance of 100 m and low at 300 m and 600 m from the coast.Things are different in the waters of Bonto Bahari District, where the highest temperature is 300 m, decreasing at 600 m and 100 m distances.Although there are differences at each station, the Kruskal-Wallis test shows no temperature difference between the waters of Gantarang and Bonto Bahari sub-districts at 100 m, 300 m, and 600 m from the coast.The highest salinity of the waters of Gantarang District at a distance of 300 m decreases at a distance of 100 m and 600 m from the coast.While in the waters around Bonto Bahari District, the lowest salinity at a distance of 100 m increased at 300 m and 600 m from the coast.Although there are fluctuations in salinity values at every distance from the coast, the Kruskal-Wallis Test shows no difference in salinity values at all distances from the coastal waters of Gantarang and Bonto Bahari Districts.
The distribution of pH values based on distance from the coastal waters of Gantarang District obtained the lowest value at 100 m from the beach and continued to rise at distances of 300 m and 600.The same pattern also occurs in the pH distribution in the waters around Bonto Bahari District.Although it has the same pattern, the pH of the Bonto Bahari District waters is higher than that of the Gantarang District.The results of the Kruskal-Wallis analysis show no significant difference in pH values at any distance from the coast both around the waters of Gantarang District and in Bonto Bahari District.
The distribution of ammonia waters in Gantarang District is highest at 100 m from the coast, then successively decreased at 300 m and 600 m from the coast.The same pattern is also shown in the waters around Bonto Bahari District.The results of the Kruskal-Wallis analysis showed that ammonia concentrations did not differ markedly at distances of 100 m and 300 m; nevertheless, there was a noticeable difference between distances of 100 m and 300 m with a distance of 600 m from the coastal waters of Gantaran District.Furthermore, there was a significant difference in ammonia concentration at a distance of 100 m with a distance of 300 m and 600 m, but there was no real difference in ammonia concentration at a distance of 300 and 600 m from the coastal waters of Bonto Bahari District.
Nitrate concentrations at all distances from the coast around Gantarang District and Bonto Bahari District have been above the threshold for marine life (>0.008mg / L).The highest distribution of nitrate concentrations is found at a distance of 100 m, decreasing at 300 m and 600 m in the waters of Gantarang District.The same pattern is also shown in the waters around Bonto Bahari District.Based on the Kruskal-Wallis test showed that there was no significant difference in nitrate concentration between the distances of 100 m, 300 m, and 600 m from the coast in the waters of Gantarang District and Bonto Bahari District.The nitrate concentration is higher in the waters of the Gantarang District.
The highest phosphate distribution in the waters of Gantarang District at 100 m from the coast decreased successively at 300 m and 600 m.While in the waters around Bonto Bahari District, the highest phosphate concentration was found at a distance of 300 m from the coast, then decreased at 100 m and 600 m with the same concentration.The results of the Kruskal-Wallis analysis showed no significant difference in phosphate concentrations at distances of 100 m, 300 m, and 600 m in the waters of Gantarang District.Whereas in Bonto Bahari waters, there is a noticeable difference between phosphate concentrations at a distance of 300 m with a distance of 100 m and 600 m from the coast, although there is no noticeable difference between a distance of 100 m and 600 m.Furthermore, phosphate concentrations are higher in the waters of the Gantarang District.Phosphate concentrations in both waters have been above > 0.015 mg/L.
The highest distribution of TOM concentrations in the waters of Gantarang District is 300 m from the coast, decreasing at 600 m and 100 m distances.The concentration of TOM in the waters of Bonto Bahari District is found at a distance of 600 m from the coast and then decreases at a distance of 300 m and 100 m.The results of the Kruskal-Wallis analysis showed no significant difference in TOM concentration at distances of 100 m, 300 m, and 600 from the coast in the waters of Gantarang District and Bonto Bahari District.The distribution of TOM concentrations in both waters is still safe as raw material for intensive shrimp farming activities because it is still below the concentration of 90 mg / L.
The distribution of the highest TSS concentration in the waters of Gantarang District at a distance of 100 m from the coast further decreases from the coast (300 m and 600 m).While in the waters of Bonto Bahari District, the highest TSS concentration is found at a distance of 300 m from the coast, then decreases at 600 m and 100 m.The results of the Kruskal-Wallis analysis showed no significant difference in TSS concentrations at distances of 100 m, 300 m, and 600 m in the waters of Gantarang District and Bonto Bahari District.
The results of the Mann-Whitney test analysis show that 3 water quality variables are not significantly different between the waters of Gantarang District and Bonto Bahari District, namely ammonia, phosphate, and TOM.Furthermore, there is a noticeable difference in temperature, nitrate, and TSS, where the value is higher in the waters of the Gantarang District.Another variable that has a real difference is DO and pH, with higher concentration in the waters around Bonto Bahari District.

Water Quality Levels Based on Distance from the Beach
The results of the RI value analysis show that the variable water quality of Gantarang District waters is best at a distance of 300 m, then at a distance of 100 m and 600 m from the coast (300 m > 100 m > 600 m) (Figure 3).Thus, it is recommended for intensive cultivators to enter the cultivation of raw water from a distance of 300 m from the beach.Three water quality variables cause a distance of 300 m better quality due to low ammonia, TSS, and TOM values.Based on IR values, the variable water quality of Bonto Bahari District is best at a distance of 600 m, then at a distance of 300 m and 100 m from the coast (600 m > 300 m > 100 m) (Figure 4).Thus, intensive cultivators are recommended to enter raw water for cultivation from 600 m from the beach. 2 water quality variables cause a better distance of 600 m due to low ammonia and TOM values.

Carrying Capacity of Waters
The geomorphological form of the coast around the Gantarang District sloping the more resounding the sea is (Figure 5).The results of direct bathymetric measurements show that the depth of the waters up to a distance of 600 m from the shore ranges from 7 -10 m.In contrast, the morphological shape of the coast around Bonto Bahari District is steep (Figure 6).The results of bathymetric extraction directly show that the depth of the water at a distance of 600 m from the shore ranges from 40 -55 m. Figure 5. Profile of beaches around Gantarang District, Bulukumba Regency In Table 4, it can be explained that the intensive pond development cluster in Gantarang District, based on the oxygen-carrying capacity, can naturally be developed at 91 ha.Existing intensive ponds have been operated in Gantarang District, covering an area of 35 ha.Thus, based on the oxygen-carrying capacity in Gantarang District, it is still possible to develop an intensive pond covering an area of 56 ha.Furthermore, the natural nitrogencarrying capacity in the Gantarang sub-district can be developed into intensive ponds of as much as 145 ha.In Total, there are 35 ha.Thus, based on the nitrogen-carrying capacity in Gantarang District, it is still possible to develop intensive ponds covering an area of 110 ha (Table 5).The number of ha that is still possible to develop 56 In Table 6, it can be explained that the intensive pond development cluster in Bonto Bahari District, based on the oxygen-carrying capacity, can naturally be developed at 90 ha.Existing intensive ponds covering an area of 25 ha have been operated.Thus, based on the oxygen-carrying capacity in Bonto Bahari District, it is still possible to develop intensive ponds as widely as possible.65 ha.Furthermore, the natural nitrogen-carrying capacity in the Bonto Bahari sub-district can be developed into intensive ponds of as much as 144 ha.In Total, there are 35 ha.Thus, based on the nitrogen-carrying capacity in Gantarang District, it is still possible to develop intensive ponds covering an area of 109 ha (Table 5).The number of units that are still possible to develop 109 In sustainable aquaculture practices, the carrying capacity of water must be higher than the utilization level.[19] the ratio between carrying capacity and utilization rate is 5:1.The development of intensive ponds above the carrying capacity of the aquatic environment will impact aquaculture's failure.Such failures can occur due to changes in the ecological structure of aquatic communities, especially phytoplanktons, and macrozoobenthos.[7] the decrease in the carrying capacity of waters can be observed from their impact on ecology, such as a decrease in phytoplankton abundance, organic enrichment in sediments, and changes in aquatic nutrients whose intensity is unacceptable to aquatic biota.[20], especially in areas around river mouths and waters that contain much organic waste, phytoplankton with potential HABs are found.[21] there will also be high total Vibrio harveyi bacteria in coastal areas with high intensive pond activity due to massive organic waste discharge.In contrast, the total concentration of Vibrio harveyi bacteria is low in coastal areas with no intensive pond activity.High organic waste in waters disrupts the balance of water quality and biota in water ponds and changes the ecological index of macrozoobenthos and the presence of bioindicators of organic waste.[22] explains the presence of macrozoobenthos Nassarius absconditus, Tenagodus sp., Nassarius sp., Tellina sp., Pinna sp., Vexillum sp., Arenicola sp, Cerithium sp.In a body of water is a bioindicator that the bottom of the water has longaccumulated organic waste.

Conclusions
Nitrate and phosphate are two water quality variables with high concentrations and the potential to reduce water quality in waters in Gantarang District and Bonto Bahari District.There are differences in water quality based on distance from the beach.The best water quality in Gantarang and Bonto Bahari sub-districts is 300 and 600 m from the beach.The main variables that cause good water quality at that distance are high DO and low ammonia, TSS, and BOT.In the waters of Gantarang District, intensive pond development can still be carried out based on the carrying capacity of oxygen and nitrogen, as much as 56 ha and 110 ha, respectively.In Bontobahari District, intensive pond development can still be carried out
Waste concentration/hypernutrification level (mg/L) N = Daily output of dissolved nitrogen waste (internal and external waste) F = flushing time of water bodies (days) BIO Web of Conferences 74, 01009 (2023) ISFM XII 2023 https://doi.org/10.1051/bioconf/20237401009V = volume of water body (L) Flushing time is determined using the formula: F = 1 / D The rate of dilution D can be calculated by the pair change method, namely: D = (Vh -V1) / T.Vh Information: (Vh -V1) = Tidal switching volume Vh = volume of water in a body of water at high tide (m 3 ) V1 = volume of water in a body of water at low tide (m 3 ) T = Tidal period in days Calculation of the volume of water bodies, measured at the highest tide MHWS (Mean High Water Spring) and at the lowest low tide MLWS (Mean Low Water Spring) using the following equation: Vh = A.h1 and V1 = A.h0 Information : A = Water area (m 2 ) h1 and h0 = water depth at highest tide and lowest low tide Vh = The volume of water at high tide V1 = The volume of water at low tide Vh -V1 = Volume change due to tidal effect.

Figure 3 .
Figure 3. Rating Index (RI) of water quality status based on distance from the coast, waters of Gantarang District

Figure 4 .
Figure 4. Rating Index (RI) of water quality status based on distance from the beach, waters of Bonto Bahari District

Table 1 .
Water quality analysis methods and tools.

Table 2 .
The water quality concentration in the waters around Gantarang District is based on distance (A = 100 m, B = 300 m, and C = 600 m) from the coast.DO the highest Gantarang waters at a distance of 300 m, experiencing a decrease at 600 m and 100 m from the coast.The same pattern also occurs in the waters around Bonto Bahari District.The Kruskal-Wallis test obtained no significant difference in DO concentration in the Gantarang and Bonto Bahari District waters.

Table 3 .
The concentration of water quality in the waters around Bontobahari District based on distance (A = 100 m, B = 300 m, and C = 600 m) from the coast

Table 4 .
Variables in determining the oxygen-carrying capacity of waters for developing intensive ponds in the Gantarang District, Bulukumba Regency cluster.

Table 5 .
Variables in determining the nitrogen-carrying capacity of waters for intensive pond development in the Gantarang District cluster, Bulukumba Regency

Table 6 .
Variables in determining the oxygen-carrying capacity of waters for intensive pond development in the Bonto Bahari District cluster, Bulukumba Regency

Table 7 .
Variables in determining the nitrogen-carrying capacity of waters for intensive pond development in the Bonto Bahari District cluster, Bulukumba Regency