Effect of hatchery and mariculture activity at the northwest coastal area of Bali on water quality and plankton community

The northwest coastal area of Bali is currently for the development of marine fish hatcheries and cage farming. This study aims to influence the hatchery and aquaculture activities of marine fish cages in the northwest coastal area of Bali on seawater quality and plankton community. The parameters observed on water quality were total suspended solids, temperature, transparency, pH, dissolved oxygen, Salinity, ammonia, nitrite, nitrate, phosphate, C-organic, total organic matter, and plankton community on diversity, similarity, and dominancy index. The results of water quality observations found that water temperature was 27.5-29.1°C, TSS 0.028-0.046 ppm, transparency 7.4-12.8 m, pH 8.1-8.3, DO 5.4-6.9, Salinity 33.2-34.1, ammonia, 0.01-0.04 ppm, nitrite 0.028-0.041 ppm, nitrate 0.018-0.036 ppm phosphate 0.026-0.038 ppm, C-Organic 0.65-0.74 ppm, TOM 0.75-1.23 ppm. Found 38 genera and 10 phyla of plankton, with an abundance was 258-26,546 ind/L, an index of the diversity of 0.89-2.15, an index of similarity of 0.22-0.64, and an index of dominancy 0.18-0.43. From these results, it can be concluded that the coastal waters of northwest Bali are in the criteria that have not been polluted and are good for marine fish farming. The northwest coastal area of Bali must be managed properly so that marine fish farming can be sustainable.


Introduction
Bali has many famous natural tourists with many beautiful natural conditions that have the potential for tourist destinations [1].The condition of the northwest coastal waters of Bali is generally influenced by the condition of the Bali Sea and activities on land [2].In the northwest coastal waters of Bali, a small part is affected by East Java Waters [3].For example, salinity in some locations around the mouth of the Mayangan River over the past 8 years has increased by about 0.2 ppt, and the last 6 years reached 0.03 ppt [4].Marine farming practices should be guided by a sustainable management system; Improving aquaculture technology must meet environmentally friendly production processes.The utilization of coastal waters for marine aquaculture must meet the carrying capacity of production and ecological carrying capacity [5].
The northwest coastal area of Bali is a potential area for nature tourism in the northern part of Bali.Coastal environmental conditions related to water quality management, domestic waste, and planning for the development of marine aquaculture concerning xero waste are of serious concern [6].The northwest coastal area of Bali is a tourist area with various types of coral reefs and ornamental fish.The water conditions are clear, with many coral islands, and decorated with coral slopes with mixed coral reef ecosystems and white sandy beaches.Indonesia's national aquaculture development concept is sustainable aquaculture without destroying natural resources.Aquaculture requires an environment with good water quality but this activity also produces waste that negatively impacts the waters; aquaculture activities need to be better managed and anticipated.The North-west coast of Bali is an area for the development of marine fish hatcheries and marine aquaculture in Bali.The activities of the marine fish hatchery and marine aquaculture in this region have developed rapidly.In the coastal areas of the mainland it is used for hatchery of milkfish, grouper, and snapper; while on the sea coast, it is used for marine aquaculture which includes floating net cages, pearl oyster culture, seaweed culture, and coral reef transplantation.The negative impact that can occur is the degradation of the coastal environment as a result of the high density of coastal cultivation activities that are over the carrying capacity of the environment.Hatchery and aquaculture activities can cause affect the quality of the coastal environment, including physical, chemical conditions and the abundance of plankton in the waters.The concentration of nutrients will affect the aquatic plankton community [7] [8].Plankton community significantly correlates with water ecological conditions; especially nitrite, salinity, transparency, TDS, TSS, and pH [9].Plankton community and species composition can be used as bioindicators of seawater quality [10].To determine the effect of hatchery and marine aquaculture activities on the quality conditions of the aquatic environment, it is necessary to observe the water quality and its plankton community.

Material and Methods
In this study, the determination of stations based on activity zones in the water area where 11 water sampling stations were determined, as shown in Figure 1.The sampling position has been determined before the survey to the field and the coordinate position is carried out using GPS Map type 188/238.Parameters of aquatic environmental quality (physics and chemistry) methods used for water quality observation refer to APHA [11].Water sampling is carried out with a composite system where each station is taken 1 water sample from 5 sampling points.Water sampling using the Kemmerer Water Sampler tool and for plankton samples used plankton-net (mesh size 20 microns).The study was conducted by analyzing water quality in the form of transparency, temperature, salinity, pH, DO, ammonia, nitrite, nitrate, phosphate, C-organic, total organic matter (TOM) and it is plankton analysis which includes its composition, abundance, and diversity.Water sampling is carried out with a composite system where each station is taken 1 water sample from 5 sampling points.Water sampling using the Kemmerer Water Sampler tool and for plankton samples used plankton-net mesh size 20 microns.The study is carried out by observing brightness, temperature, salinity, pH, DO, ammonia, nitrite, nitrate, phosphate, C-organic, Total organic matter (TOM); and it is plankton analysis which includes its type, abundance, and diversity.Physio-chemical parameters of water, such as temperature, salinity, brightness, pH, and dissolved oxygen are carried out in the field.For other parameters such as the content of Phosphate, Nitrite, C-organic Ammonia Nitrate, and Total Organic Matter (TOM) in water, it was carried out in the laboratory of the Research and Innovation Agency, Gondol, Bali.
To calculate the plankton diversity index using the Shannon-Wiener formula, the similarity index uses the Simpson formula, and to determine the dominance index using the Simpson formula.Plankton sampling was carried out by water sampling, by filtering 25 liters of seawater using plankton-net mesh size 20 microns, net mouth diameter 30 cm; To be a sample volume of plankton 25 ml is put into the sample vial and given 2% formalin.Plankton observations include identification up to the genera level [12] and the number of individuals of each genus.To calculate the plankton diversity index using the Shannon-Wiener formula, the similarity index uses the Simpson formula, and to determine the dominance index using the Simpson formula.To determine the level of pollution between stations, an integrated comparison of measurement values from physical, chemical, and biological parameters consisting of suspended solids (TSS), DO, N-ammonia content, and plankton diversity index with the value of the degree of pollution [6].To determine the influence of activity waste on waters, a Multiple regression analysis was carried out; between physical quality parameters with water chemistry as the influencing variable and plankton diversity index as the affected variable, with SPSS software.

Physical quality of seawater
The results of measuring the coordinates of each observation point using the Garmin 60 GPS tool and the results of measuring the physical quality of seawater can be seen in Table 1.
The waters deep of the northwest coast of Bali (Station 1-11) have water depths ranging from 16.5-28.6m with an average of 21.64 m (Table 1) These depth conditions are relatively good for hatchery sites and aquaculture of marine fish and pearl oyster.The transparency values at each observation station (Table 1) ranged from 7.4-12.8m, with an average of 10.4 m.The waters brightness value on the northwest coast of Bali is still in a fairly good criterion, where according to the Government Regulation of the Republic of Indonesia number 22 of 2021 that the standard for seawater quality standards for marine life (aquaculture) for transparency is more than 5 m.In Table 1 it can be seen that the total suspended solids (TSS) in the study area is relatively very small, ranging from 0.028-0.046ppm with an average of 0.034.This value is still very low or very clear conditions/good for coastal waters; where according to the Government Regulation of the Republic of Indonesia number 22 of 2021 that the standard for seawater quality standards for marine life (aquaculture) for total suspended solids is < 20 ppm.Results of water temperature at each sampling station (Table 1) show that the water temperature at the 11 observation stations ranges from 27.5-29.1 o C with an average of 28.3 C.This may be due to local weather differences when sampling.The temperature difference at each observation station can also be caused by the difference in time (hours) when sampling, where the more days/evenings the sea water temperature tends to increase.The temperature of a body of water is influenced by the composition of the substrate, turbidity, rainwater, surface area that directly gets sunlight, and runoff water.

Chemical quality of seawater
The results of measuring the coordinates of each observation point using the Garmin 60 GPS tool and the Chemical quality of seawater are presented in Table 2.The fluctuation in the pH value of the water at each observation station was very small, ranging from 8.1-8.3 with an average of 8.21 (Table 2).The results of water pH in the research area are still within the limits of the quality standard from Government Regulation number 22 of 2021 is 7-8. 5.
In Table 2 it can be seen that the fluctuation in the salinity value of the water at each observation station is very small, with the salinity value of water in the sampling results ranging from 33.2-34.1.The results of water salinity in the research area are still within the limits of the quality standard from Government Regulation number 22 of 2021 is 33-34 ppt (natural).The sea-level increase is more influential than changes in the coastlines or bathymetry of river mouths.Generally current in the waters south of Bali to East Java most of the wind moves to the east under the influence of the west monsoon.Simulated that particles from East Java waters only 3.47% reach the waters of the Bali Strait [3].The results of salinity observations in several locations around the mouth of the Mayangan River for 8 years have increased by about 0.2 ppt, and in the last 6 years reached 0.03 ppt [4].
In Table 2 it can be seen that fluctuations in the value of dissolved oxygen (DO) levels of water at each observation station are relatively small, ranging from 5.4-6.9 with an average of 5.85 ppm.The value of DO in the research area is still within the limit of quality standards according to Government Regulation number 22 of 2021, which is > 5 ppm.Water-dissolved ammonia fluctuation levels at each observation station were small relatively, ranging from 0.01-0.04 with an average of 0.017 ppm (Table 2).The value of ammonia content in the research area is still within the threshold of quality standards according to Government Regulation number 22 of 2021, which is > 0.3 ppm.The fluctuation in nitrite levels at each station (Table 2) is relatively small, ranging from 0. 028-0.041 with an average of 0.0342.The fluctuation in the value of nitrate levels at the station (Table 2) is relatively small, ranging from 0. 018-0.036with an average of 0.0278.The value of nitrate levels in water is still within the range of quality standards of Government Regulation number 22 of 2021 that the standard for seawater quality for marine life (aquaculture) nitrate is 0.06 ppm.Fluctuation in the value of phosphate levels at each station (Table 2) is relatively small, ranging from 0. 026-0.038ppm with an average of 0.0288 ppm, but when compared to the Government Regulation number 22 of 2021, it has exceeded the standard for seawater quality standards for marine biota, which is 0.015 ppm.The results of observations of C-organic levels at each station (Table 2) showed relatively small fluctuations ranging from 0.65-0.74ppm with an average of 0.673 ppm.The results of observing the total value of total organic matter levels at each station (Table 2) showed relatively small fluctuations ranging from 0.75-1.23 ppm with an average of 1.081.Oceanographic conditions, such as the physical and chemical aspects of seawater, determine aquatic productivity [6].

Plankton composition
In general, plankton found in the waters of the station on the northwest coast of Bali can be grouped into phytoplankton and zooplankton.Found 10 phylum which includes 3 phyla of phytoplankton namely Bacillarophyta, Cyanophyta, Chlorophyta, and 7 phylum zooplankton namely Protozoa, Coelenterata, Chaetognatha, Annelida, Arthopoda, Mollusca and Protocordata.The dominant Phylum are Protozoa, Bacillarophyta, Chlorophyta and Arthopoda (Table 3).
The results of research in Lake Siombak found 66 genera including 54 genera of phytoplankton and 12 genera of zooplankton [6].The increase in the plankton population is generally caused by a high concentration of nutrient load in the study area.[7].The results of the study on the Mediterranean coast have a potential diversity in assessing regional influences and producing plankton diversity as an ecological indicator; plankton diversity can be used for significant environmental assessment [8] [9].The plankton dominance index at each observation station ranged from 0.13-0.46,indicating there is no specific species-dominated plankton in the waters because almost all of them included the low partial dominance criterion (<0.4) (Lee et al., 1978) (Figure 5) except at station 1 which had a mean dominance index value of 0.43 and station 2 with a dominance index of 0.46.The plankton dominance index can be used to see whether or not certain species dominate a plankton community in these waters.The results of research in Bengal Bay showed 7 water parameters, related to plankton communities.The abundance of Acartia tonsa is related to salinity value, water transparency, total dissolved oxygen, total suspended solids, precipitation, and water exchange.The increase in the population of Bahai americamysis is triggered by a decrease in salinity, transparency, and TDS values and an increase in water discharge.Furthermore, the increase in the population of Grandidierella megnae is influenced by an increase in water temperature that is negatively correlated with pH value and water exchange.[10].
The results of the study of maximum distribution in the Bali strait exceeded water quality parameters and its effect on biota was the value of BOD was 83.031 mg / L, Nitrate was 0.924 mg / L, phosphate was 0.176 mg / L and TSS was 27.574 mg / L. BOD made water polluted, Nitrate and Phosphate are triggers of algae boom, and TSS is not suitable for corals and seaweed [13].The water quality of Muara Perancak from January to March shows heavy pollution and poor for mangrove tourism; Chemical parameters (nitrates, phosphates, ammonia) contribute most to pollution levels [14].In intensive shrimp farms, Chrysophyta divisions are found which are more abundant in intensive and traditional ponds.Appeal on EMI shrimp ponds is intensive and traditional [14].Intensive shrimp ponds are dominated by Halosphaera viridis (3143.88ind/m3), while traditional ponds are dominated by Rhizosolenia stolterfothi (1414,746 ind/m3) [13].In intensive ponds with a phytoplankton diversity index (H') of around 1.95 while in traditional ponds around 2.17 [14] The dominance index value in intensive ponds is 0.18 and in traditional ponds is 0.15; the high abundance of phytoplankton will disturb and can threaten the failure of Vanname shrimp production in intensive ponds [15].Milkfish can be used as a biofilter in inlet and outlet maintenance plots, which can control phytoplankton populations and can improve the survival of Vananame shrimp in ponds [16].Phytoplankton blooms are influenced by nutrient inputs from the external environment, while internal interactions between phytoplankton and zooplankton are still difficult to predict [17].
The results of an integrated assessment of physical, chemical, and biological parameters obtained a pollution index value of <2, all of which are included in the criteria of not being polluted.From multiple regression analysis, it can be seen that the twelve physical-chemical variables of water (temperature, TSS, brightness, pH, DO, salinity, ammonia, nitrite, nitrate, phosphate, C-organic, and TOM) have an insignificant influence on plankton diversity index.The magnitude of the value of the multiple regression coefficients (R 2 ) obtained a value of 0.485; this means that the amount of contribution given by the 12 variables X (physical-chemical parameters of water) to variable Y (plankton diversity index) is 48.5%,While 51.5% is caused by other unknown factors; This shows that in addition to the physical and chemical parameters of water, many factors are unknown.
In Florida's case, global urea use, including slow-release fertilizers, has great potential in nitrogen input into bay waters; furthermore, it can have an impact on changes in phytoplankton diversity and nutrient cycles [18].In planktonic communities there are seasonal and spatial variations; Where the composition of the plankton community and diversity are influenced by several parameters of water quality including transparency, dissolved oxygen, nitrates, phosphates, and silicates (p < 0.05).The development of ecotourism and fisheries agritourism needs to be carried out together; where ecotourism and fisheries agritourism activities are interdependent; Ecotourism activities, community activities, fisheries agritourism, and agriculture, indirectly affect each other [19].Coastal areas are prone to tsunamis, abrasion, storms, and tidal waves [20].Aquatic environmental conditions correlate significantly with species distribution and plankton community structure [21].Marine aquaculture activities, mining, and extreme weather such as drought and rain can cause nutrient enrichment that can affect plankton diversity and changes in coastal water quality [22].A tidal of wind-driven waves and three-dimensional flow in coastal areas around the north coast of Bali has already been carried out [23].The accumulation of waste products on coastal land can also enrich nutrients in coastal waters by intermediating rainwater flows and rivers that flow into coastal waters by carrying waste material [24].The total alkalinity and distance of settlements from coastal areas constitute Environmental actors that have a significant influence on plankton diversity.Overall, the main pattern of community formation is the limitation of dispersal where about 83% of the community formation process is the assembly of eukaryotic plankton communities in coastal areas [25].
The same decrease in ammonia and nitrate levels can cause diatoms to bloom among phytoplankton biomass towards the end of the culture period.Changes in water quality such as increasing temperature, salinity, and phosphate levels, can lead to the development of diatom blooms, the appearance of dinoflagellates, and mixotrophic flagellates.The proliferation of herbivorous ciliates can inhibit the development of unwanted phytoplankton, which can promote shrimp growth, survival, and a better feed conversion ratio.Absorption of ammonia and nitrates by maximal growth of diatoms, It can absorb nutrients that reach toxic levels, so that the discharged aquaculture wastewater is exposed to the environment [26].Zooplankton is an important factor in the food chain and is closely related to the function of pelagic ecosystems.Therefore, an understanding of the functional diversity of zooplankton and its response to water quality change is essential for an aquatic system [27].The composition and dynamics of plankton communities in Maryland coastal lagoon have changed water quality in the last two decades [28].The diversity of nanoplankton, micro plankton, and mesozooplankton can be used to determine the ecological function of drained swamps and the impact of replenishment in catchment areas.Nanoplankton, micro plankton, and mesozooplankton have high seasonal variations due to environmental fluctuations [29].Phytoplankton is an indicator of the quality of the aquatic environment in coastal areas [30].
Environmentally conscious marine tourism can prevent water quality degradation for mariculture, geographical indications of grouper aquaculture, and coastal marine ecotourism.The degradation of marine waters on the northwest coast of Bali hasn't yet, but integrated management must continue to be carried out to maintain integrated marri culture.Grouper seed and commercial-size production on the northwest coast of Bali, are still relatively good.This is largely due to the good water quality on the west coast, which is suitable for marine fish farming as it is constantly maintained by the local community.This potential strongly supports geographical indications and increases grouper production for local, national, and international markets as well as supports coastal marine ecotourism.Village government management in issuing aquaculture business permits and monitoring fish health and aquatic environment.Arrangement of the west coast of Bali agritourism, and marine fish hatchery center.
Marine ecotourism management arrangements should follow suit to grow areas that refer to living structures, spaces, and patterns that are in harmony with the local culture [ 31] [32].Observations at 11 stations showed high diversity index values at all stations.Found types of plankton that cause predominantly seasonal and dangerous algal blooms, namely the genera Cochlodinium sp., Alexandrium, Dinophysis, and Gymnodinium.The dominant genera are relatively different at each station according to their geographical conditions and aquatic environment.Community dinoflagellates are more precise and faster than microscopic analysis for community analysis [33].The effects of pollution in coastal water areas can last for many years on benthos and plankton communities that do not show permanent disturbance due to their high spatial dynamics [34].The maximum abundance of zooplankton and phytoplankton is generally reached at the height of the rainy season.From multivariate analysis, it was found that the pattern of species distribution of zooplankton and phytoplankton communities depends on the season.From the related analysis, it was found that variations in the distribution of species and community structure of zooplankton n phytoplankton depend on the conditions of the aquatic environment.The results of the BEST matching analysis show that NO2-N along with salinity, rainfall, transparency, TDS, TSS, and pH are major components of variations in species distribution and composition of zooplankton and phytoplankton communities.The correlation analysis shows that the similarity and diversity of genera are significantly correlated with salinity, transparency, and total dissolved solids.The results of this study show that the distribution pattern of zooplankton and zooplankton is influenced by the ecological conditions of these waters and can be used as a bioindicator of the quality of marine waters [10].

Conclusion
The results and discussion of this study can be concluded as follows: 1.The physical, chemical, and biological condition of coastal waters at every station on the northwest coast of Bali is still suitable for biota/marine aquaculture 2. Found as many as 38 genera of plankton from 10 phylum with abundance ranging from 258-26.546 ind./L. 3. The index of diversity plankton ranges from 1.06-2.44ind./L; index similarity 0.27-0.63 and Dominance Index 0.13 -0.46, which indicates most waters are still relatively good.4. The results of an integrated assessment of physical, chemical, and biological parameters obtained a pollution index value of <2, all of which are included in the criteria for not being polluted.5.There was no significant correlation between the parameters of physical and chemical water and the plankton diversity index.

Advice
Based on the conclusions of the research results, several suggestions can be submitted as input in the context of utilization and management of aquatic resources on the northwest coast of Bali: 1. To immediately arrange the layout and waste management system for pond activities, seaweed cultivation, pearl shells, and fish farming in floating net cages, so that aquaculture activities done in northwest Bali do not cause a decrease in the quality of the aquatic environment.2. It is recommended to relevant agencies together with local communities be more intensive in management and restrictions should be placed on aquaculture business permits if they have exceeded the carrying capacity of the land 3.For aquaculture in waters (floating net cages, pearls, seaweed) to limit stocking density so as not to exceed the carrying capacity of the land, feeding efficiency, layout arrangement according to the direction of the current, not cleaning cage nets or other facilities in the middle of the sea that can pollute the waters, routine and environmentally friendly disease monitoring, and control, simultaneous countermeasures if a disease outbreak arises to break the disease cycle.

Figure 2 .
Figure 2. Plankton abundance at every station on the northwest coast of Bali.

3. 5 .
Plankton diversity, Similarity, and Dominance indexFluctuations in the value of the plankton diversity index at each station are relatively small, ranging from 1.06-2.44ind./L.The calculation of the diversity index of each station, shown (Figure3), has not shown too much of the tendency of ecological pressure and deterioration in water quality, as well as the instability of plankton communities which is reflected in the diversity index that is almost close to or greater 2, except at station 1 (1.06) and station 2 (1.46).

Figure 3 .
Figure 3. Plankton diversity index at every station on the northwest coast of Bali.We see the results of type Similarity index values at observation stations (Figure4) which results are relatively good (0.27-0.63) in most stations with medium to high similarity index (0.44-0.63) except at stations 1 (0.27) and 2 (0.35).

Figure 4 .
Figure 4. Plankton similarity index at every station on the northwest coast of Bali.

Figure 5 .
Figure 5. Plankton dominancy index at every station on the northwest coast of Bali.

Table 1 .
Station location, sampling coordinates, and the physical quality of seawater on the northwest coast of Bali.

Table 2 .
The chemical quality of seawater at every station on the northwest coast of Bali.

Table 3 .
Grouping of plankton found in the coastal waters of the northwest coast of Bali.