Abstract
Abstract. Seagrasses are marine flowering plants which are part of a highly productive coastal ecosystem and play key roles in the coastal processes. Unfortunately, they are declining in area coverage globally, and seagrass losses can be attributed to climate change such as sea-level rise, increase in sea surface temperature, and decrease in salinity, as well as human-related activities. The objective of this research is to assess the historical changes in the seagrass habitat and environment of Busuanga, Philippines using time series data available in the Google Earth Engine (GEE) platform. These include satellite data such as MODIS, Landsat 5, 7, and 8, and SeaWIFS. Reanalysis data such as HYCOM was also utilized in this research. Results from HYCOM data show that there has been a 0.0098 °C increase in the sea surface temperature per decade in Busuanga while MODIS data indicates an increase of 0.0045 °C per decade. Moreover, HYCOM data also shows an overall average of 0.76 mm in sea surface elevation anomaly and a decreasing trend in salinity values at 0.0026 psu per decade. Chlorophyll-a concentration has a minimal increase based on results from MODIS and SeaWIFS. Aside from changes in water parameters, changes in the land also affect seagrasses. Forest loss may cause increased siltation in the coastal ecosystem which can lead to seagrass loss. Based on the results of Landsat satellite image processing, there has been forest cover loss in Busuanga with the highest loss occurring in 2013 when super typhoon Yolanda ravaged the island. Lastly, results from the linear spectral unmixing of 778 Landsat images from 1987–2000 show that the average percent cover of seagrasses in Busuanga were declining through the years.
Highlights
Seagrasses are unique marine flowering plants that can live entirely submerged in water (Short and Coles, 2001)
Based on the HYbrid Coordinate Ocean Model (HYCOM) time series data from 1993-2019, an overall average of 0.76 mm in sea surface elevation anomaly occurs in Busuanga and it increases at the rate of 0.0027 mm per decade
It serves as shelter to a variety of marine species and provides valuable goods and services to humans (Koedsin et al, 2016; Roelfsema et al, 2009; United Nations Environment Programme, 2020)
Summary
Seagrasses are unique marine flowering plants that can live entirely submerged in water (Short and Coles, 2001) They serve as a nursery for juvenile fishes and as feeding grounds for various marine animals including endangered species such as sea turtles and dugongs (Koedsin et al, 2016; Roelfsema et al, 2009). They help in improving the visibility and water quality in their area and they act as buffers to reduce currents and erosion (Hemminga and Duarte, 2000), as well as increase oxygen levels in the water column. Studies predict more seagrasses will be lost if proper resource management will not be put into place (Borum et al, 2004; Turner and Schwarz, 2006)
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