Monitoring of the impact of water quality environment and mariculture in the bay - Marine Aquaculture&Impact

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Research Background

Offshore bays which have weak water exchange capacity are affected by strong human activities. After entering the bay, nutrient pollutants accumulate easily, but not easily diffuse, resulting in the ecological environment in the bay being threatened. In order to build a green and ecological environment and achieve the harmonious development of man and nature, it is necessary to carry out corresponding protection, governance and restoration of the bay. Among them, the monitoring of the water quality of the bay is a necessary part of long-term tracking, defining the status quo and making corresponding decisions.

Based on the remote sensing technology with high spatial coverage and long time series traceability, the monitoring topic of water quality environment and marine aquaculture impact monitoring in the bay was constructed. Machine learning algorithms are used to establish inversion models for the concentration of total inorganic nitrogen (C_DIN) and orthophosphate-phosphorous (C_{PO4_P}), and the accuracy is verified. Then, the model is applied to the remote sensing image, and the spatial distribution characteristics and long-term temporal changes of nutrient in the bay are obtained. On this basis, we focus on the mariculture area in the bay, dynamically monitors the number of aquaculture and the water quality changes in the aquaculture area, and explores the impact of mariculture on the water quality in the bay.

The special topic of monitoring the impact of water quality environment and marine aquaculture in the bay provides a special map of C_DIN and C_{PO4_P} in the bay, which provides a new data source for the governance of the ecological environment in the bay, and makes up for the shortcomings of other monitoring methods that are scattered, low frequency, and cannot achieve large-scale simultaneous coverage.

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Figures

Fig 1 The concentration of total inorganic nitrogen in Shenzhen Bay
Fig 2 The concentration of orthophosphate-phosphorous in Shenzhen Bay

Scientific Progress

The bay water quality parameter data sets includes the concentration of Dissolved Inorganic Nitrogen (DIN) and Active Phosphate (PO4_P), measured in milligrams per liter (mg/L). This dataset features a high spatial resolution of 10 meters × 10 meters and a temporal resolution of 16 days, covering Shenzhen Bay from November 1988 to February 2020. Validation against actual measurements indicates an overall root mean square error of 0.45 mg/L for the DIN product and 0.057 mg/L for the PO4_P product.

This dataset employs remote sensing reflectance data from Landsat 5-TM and Landsat 8-OLI as input. Utilizing empirically derived relationships from laboratory research (constructing single-band/multi-band indices through sensitive bands) and employing algorithms such as the Backpropagation Neural Network (BPNN) and Support Vector Machine (SVM), models have been developed to inversely estimate the concentration of DIN and PO4_P. As a result, concentration products for DIN and PO4_P in Shenzhen Bay from 1988 to 2020 have been produced. This work lays the foundation for further research on changes in nutrient concentration in the bay and the impact of anthropogenic activities on the ecological effects of the bay.

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References

Huang, Jingjing, Difeng Wang, Fang Gong, Yan Bai, and Xianqiang He. 2021. "Changes in Nutrient Concentrations in Shenzhen Bay Detected Using Landsat Imagery between 1988 and 2020" Remote Sensing 13, no. 17: 3469. https://doi.org/10.3390/rs13173469.

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Research Background

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Scientific Progress

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