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Results and Discussion.
This study have recorded four sources of wastes which worthy to be considered as main possible causes of the failure in seaweed culture in Tablolong and Bolok, namely agricultural run-offs, domestic waste from Kupang city, port and industrial waste and damages on seagrass beds and corral reefs.
Agricultural run-offs
As reported elsewhere, the recent occurence of seaweed culture failures has been associated with the influx offloating mud from agricultural run-offs. More spesifically, Hartoko and Kangkan (2009) pointed that nitrate and phosphate are possible factors responsible for seaweed growth in Kupang Bay.Current field observations showed that more than 40% of northern shoreline of Kupang Bay was heavilly affected by floating mud from agricultural run-offs during rainy season. As a result,brown colored sea shorebelts and spots were displayed from Pit’ay village seashore area untill Noelbaki seashore area. Interestingly, although the rainy season in this particular area only lasted 4 moths,this brown coloured belts and spots were remained there along the yearbecause continuous wave actions makefloating mud in shallow seawater difficult to settle into the bottom of the sea. Rais (1994) related sea surface and sea bottom dynamics to extreme temperature dynamics in respected atmosfeer.
It seems that some of floating muds eventually flows to the southern part of Kupang Bay along with sea water current and caused relatively high turbidity of sea water just in front of Kupang city (midle part)and also in the southern part of Kupang Bay including Tablolong and Bolok. Corral reefs, seagrass bed and seaweed alongthis seawater currentis probably affected by the floating mud as confirmed by moderate to severa condition of seagrass bedsfound in Tablolong and Bolok(Amtiran et al., 2017) as well as corral reef condition in all areas of Kupang Bay (Sine et al., 2013).
Effects of influx floating mud from agricultural run-offs on local seaweed in Kupang Bay is poorly understood due to lack of availableinformation. Umar (1999) reported a list of local seaweed along with their seasonal abundance. Those grows and abundant during rainy season were Acanthophora muscoides, S. spicifera, Anadyomene wrightii, Caulerpa certulariodes, C. racemosa, C. serrulata, Dyctyota cervicornis, Enteromorpha spp., Sargassum spp., Turbinaria ornata, Turbinaria spp., Ulva lactuca and Ulva reticulata. Sato et al. (2010) reported that seaweed beds perform the role of fixing carbon dioksideand absorber of nutrients in theseawater and by this way keeping the water clean and preserving the marine environment.The facts of seasonal distribution of local seaweed as described by Umar (1999) and absorbtion of nutrient and carbon diokside as explained by Sato et al (2010) explains in part why E.
cotonii grows well after rainy season until august in Kupang Bay as compared to it’s growth after august until november.Recent observation of seaweed culture in Sulamu (northest part of Kupang Bay) between april and august showed that seaweed grows well in low floating mud areas.
It is also widely recogized that herbicide and pesticide were commonly used in agricultural areas, mostly in the low and up land area close to northern part of Kupang Bay. However, noscientific reports have been produced so far. The possible effects ofchemicals used inagricultural practices still a question to be answered in the next future.
Domestic waste loading
The possible significant waste loading from industry and domestic sources was observed along the shorelinejust in front of populated area. Kupang city is located to the seaward side, on the southern coast of the bay. On 2011 population of Kupang city was 349.344 people. Accordingly, potential exists ofhazardous waste loadings from industry and domestic sources as well in forms of solid and liquid waste.
Some speculate that domestic and industrial waste loadings are moderate, whereas loading from agricultural sources are relatively high as described above.
The most recognized domestic wasteare food debris from household and solid matterials made of plastic and paper. Observations showed that most of household disposed their waste at community bins and sites followed by the collection of waste by government agencies. In this way public in municipalities and also marine environment of Kupang Bay are prevented and exposed to harmful effects of the waste.
Thus, so far this preliminary study recorded no clues to uncover the possible negative effects of domestic waste on marine environment in general and on seaweed culture failures phenomenon in Tablolong and Bolok.
However, some investigator still implicitly pointed human act through unwise domestic and industrial waste disposal has indirect effect on failure phenomenon of seaweed culture in Tablolong and
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Bolok.The failure was probably caused by seagrass and corral reef ecosystem function performace, whereas seagrass and corralreef degradation caused directly by human actions. Pirzan and Utojo (2017) reported that there is an association between the growth of seaweed culture in Kupang Bay to seagrass beds and corral reef condition. Similar attitude has been shown by Amtiran et al (2017).
Sea transport and port waste
Bolok and Tablolong are considerably close to Tenau and Bolok ports. Accordingly, wastes from ships were susceptible as cause of seaweed culture failure. Characteristic for ship waste is the fact that many different types of waste occur in relativelly small area. Waste from ships were dominated by oily and greasy from engines. Other hazardous waste originated on board including bilge water, paints and varnish. Besides solid and liquid waste, carbon dioxide and other gases are emitted by the vessels engines.
Broad observations around Tenau, Bolok, Namosain and nearby ports gave insights that the shorelinesclose to harbour are dead zones. No mangroves in the beach, no local seaweeds, and no seagrasses. We concluded that the dead zone closer to harbour are most probably caused by greasy and oily substancescome from ships together with bilge water, paints and varnishes.When these substances spilled into the water, they may undergo a variety of weathering phenomena as explained by Prince (1995) including floating,evaporating or dissolve in the underlying water, and some polymerizing.
Substances dissolved in the underlying water together with the new formed polymers can be transported by water current far away from harbour and eventually setled in some marine area such as in Tablolong and Bolok and cause damages on seaweed cultures. More studies are needed to know the negative effects of wastes spilled from ships entering Tenau, Bolok, Namosain and nearby ports in order to expand and strengthen the seaweed industry in Kupang Bay, research to find out the causes of seaweed culture failure observed recently in Tablolong and Bolok is considerably important. The causes could be physical, chemical or biological.
Acknowledgement
The authors wish to gratefully acknowledge Ministry of Research, Technology and Higher Education of the Republic of Indonesia for funding Pengembangan dan Penerapan Teknologi Produksi Rumput Laut Setengah Jadi Skala Industri Untuk Meningkatkan Nilai Tambah dan Ekonomi Masyarakat Research Project.
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