Quantifying Recent Trends in Seagrass Cover and Biomass in a Stressed Environment, Pulau Semakau, Singapore

Abstract

Globally seagrass habitats have experienced sharp declines over the past century, with an annual loss of seagrass cover of 7%yr-1 since 1990. Despite the attention to seagrass this decline has brought, little research has been directed towards trends of seagrass habitats in Singapore. Using satellite imagery and novel methods to quantify seagrass and mitigate error, this study partially fills this gap by examining Singapore?s second largest seagrass meadow on the island Pulau Semakau. From 2001 to 2013, seagrass bed extent declined over 45%, with an average rate of decline of 5.1%yr-1. Despite a 17% decrease in extent between 2011 and 2013, total above-ground biomass decreased only 5% from 41.6 to 39.6 Mg, indicating an increase in average biomass density within the remaining seagrass meadow. A novel method was also developed to remotely quantify seagrass density without the destructive sampling required to measure biomass.