16:30 〜 16:45
[AHW22-20] Assessing the Influence of NO3-N in the Seawater on the Composition of Benthic Communities: Utilizing Remote Sensing Techniques
キーワード：Nutrient, Seawater, Landsat time series, Benthic community, Nitrate-nitrogen, Aero photo
Coral reefs play an important role in biodiversity and habitat, frequently referred as the "rainforests of the sea." Approximately a quarter of the fish population in the ocean rely on thriving coral reefs. Coral reefs provide a multitude of hiding places and food sources for fish and other species, as well as serving as a breeding and nurturing environment for their offspring. Nevertheless, there has been a progressive decline in the coral reef ecosystem globally. Multiple factors contribute to the decrease of coral reefs; coral reefs face continuous and unyielding pressure from a multitude of global and local factors, such as climate change, decreasing water quality, excessive fishing, pollution, and unsustainable coastal development.
Yoron island, located in Kagoshima Prefecture, has experienced a total depletion of coral community in lagoon of eastern part of island1. Significant transformations also took place in terrestrial regions, specifically the transition from cultivating rice to cultivating sugarcane. Utilization of chemical fertilizer is progressively rising, thus presenting significant potential for the transfer of nutrients into coastal environment. Additionally, El Niño–Southern Oscillation (ENSO) event characterized by abnormal sea surface temperatures (SST) took place in 1998, and reoccurred with less intensity in the period of 2014–2016. Exploring the diverse factors that impact the coral reef ecosystem is a fascinating endeavour.
This study utilized aerial photography and Landsat imagery. The adjustment of Landsat data for surface reflectiance includes the removal of solar glint and correction for the water column. Water column corrections mitigate the perplexing impacts induced by varying depths in sceneries, however, they do not entirely eradicate this phenomenon 2. Both aerial photo and Landsat data were employed with unsupervised classification techniques to categorize the benthic population into five classes: Sand, Rock/Coral, Sand-Rock/Coral, Seagrass, and Seagrass-Rock/Coral. The SST data were derived with utilizing thermal bands on several generations of Landsat satellites. The Chavez et al. (1996)’s approach was employed for Landsat 5, yet Landsat 7 and Landsat 8 utilized with Jin et al. (2015)’s method. The NO3-N concentration was determined using the SST value. The regression is utilized to determine the correlation between each parameter. The findings indicate a steady change in benthic population, while the concentration of NO3-N exhibited a similar pattern. The data on nitrate-nitrogen (NO3-N) levels indicate a strong impact on the composition of benthic species in the eastern section of Yoron Island. There is a clear correlation between the levels of NO3-N and the amount of rock/coral cover, which has a substantial impact on the benthic ecology. A similar phenomenon occurs in the correlation between NO3-N and temperature. The presence of NO3-N appears to have an impact on alterations in the benthic ecology. Nevertheless, it is potential that alternative variables might have a more significant influence on these alterations.
References
1 T. Nakano, I. Yamamoto, C. Nakamura, and K. Hata, Abstract of the 68th Annual Meeting of The Japanese Society of Irrigation, Drainage and Rural Engineering (2019)
2 M.L. Zoffoli, R. Frouin, and M. Kampel, Sensors, 14, 16881 (2014).
3 F.P. Chavez, S.K. Service, and S.E. Buttrey, J. Geophys. Res. Ocean. 101, 553 (1996).
4 M. Jin, J. Li, C. Wang, and R. Shang, Remote Sens. 7, 4371 (2015).
Yoron island, located in Kagoshima Prefecture, has experienced a total depletion of coral community in lagoon of eastern part of island1. Significant transformations also took place in terrestrial regions, specifically the transition from cultivating rice to cultivating sugarcane. Utilization of chemical fertilizer is progressively rising, thus presenting significant potential for the transfer of nutrients into coastal environment. Additionally, El Niño–Southern Oscillation (ENSO) event characterized by abnormal sea surface temperatures (SST) took place in 1998, and reoccurred with less intensity in the period of 2014–2016. Exploring the diverse factors that impact the coral reef ecosystem is a fascinating endeavour.
This study utilized aerial photography and Landsat imagery. The adjustment of Landsat data for surface reflectiance includes the removal of solar glint and correction for the water column. Water column corrections mitigate the perplexing impacts induced by varying depths in sceneries, however, they do not entirely eradicate this phenomenon 2. Both aerial photo and Landsat data were employed with unsupervised classification techniques to categorize the benthic population into five classes: Sand, Rock/Coral, Sand-Rock/Coral, Seagrass, and Seagrass-Rock/Coral. The SST data were derived with utilizing thermal bands on several generations of Landsat satellites. The Chavez et al. (1996)’s approach was employed for Landsat 5, yet Landsat 7 and Landsat 8 utilized with Jin et al. (2015)’s method. The NO3-N concentration was determined using the SST value. The regression is utilized to determine the correlation between each parameter. The findings indicate a steady change in benthic population, while the concentration of NO3-N exhibited a similar pattern. The data on nitrate-nitrogen (NO3-N) levels indicate a strong impact on the composition of benthic species in the eastern section of Yoron Island. There is a clear correlation between the levels of NO3-N and the amount of rock/coral cover, which has a substantial impact on the benthic ecology. A similar phenomenon occurs in the correlation between NO3-N and temperature. The presence of NO3-N appears to have an impact on alterations in the benthic ecology. Nevertheless, it is potential that alternative variables might have a more significant influence on these alterations.
References
1 T. Nakano, I. Yamamoto, C. Nakamura, and K. Hata, Abstract of the 68th Annual Meeting of The Japanese Society of Irrigation, Drainage and Rural Engineering (2019)
2 M.L. Zoffoli, R. Frouin, and M. Kampel, Sensors, 14, 16881 (2014).
3 F.P. Chavez, S.K. Service, and S.E. Buttrey, J. Geophys. Res. Ocean. 101, 553 (1996).
4 M. Jin, J. Li, C. Wang, and R. Shang, Remote Sens. 7, 4371 (2015).