A method for examining temporal changes in cyanobacterial harmful algal bloom spatial extent using satellite remote...

Cyanobacterial harmful algal blooms (CyanoHABs) have been observed to increase globally in recent decades. However, precise spatial data on their extent remains limited. Traditional monitoring methods are often site-specific and lack the ability to track changes across large areas. Remote sensing offers a scalable alternative for observing CyanoHABs across multiple regions. Prior research has shown that satellite imagery can detect algal blooms, but few studies have focused on quantifying temporal changes in their spatial distribution. This gap motivated the development of a standardized method for assessing CyanoHAB spatial extent using satellite data. Existing studies have used satellite data for bloom detection, but few have evaluated changes over time. No prior work had resolved how CyanoHAB spatial patterns evolve across different geographic regions. This study aimed to address that uncertainty by applying satellite remote sensing to track CyanoHABs in three U.S. states.

The study aimed to develop a method for quantifying temporal changes in the spatial extent of CyanoHABs using satellite remote sensing. The goal was to create a transferable approach applicable to different geographic regions. The researchers focused on Florida, Ohio, and California between 2008 and 2012. The motivation was to provide a scalable solution for monitoring CyanoHABs across multiple water bodies. The method needed to be adaptable to different spatial areas and satellite platforms. The study also sought to categorize CyanoHABs into risk levels using WHO guidelines. By analyzing satellite data, the researchers aimed to evaluate how CyanoHABs changed over time. The approach was intended to support future monitoring efforts using newer satellite instruments.

The researchers used MERIS satellite imagery to assess CyanoHAB spatial extent. The method was applied to three U.S. states—Florida, Ohio, and California—over a five-year period. Temporal changes in CyanoHAB surface area were evaluated for each state. The method involved identifying and quantifying CyanoHABs in inland waterbodies. The WHO’s recreational guidance levels were used to classify bloom areas into low, moderate, and high-risk categories. The study focused on transferability of the method across different geographic regions. The approach was designed to be compatible with future satellite missions like OLCI. The method included a systematic evaluation of satellite-resolvable waterbodies and their bloom status.

The results showed a significant increase in CyanoHAB surface area in Florida, primarily due to high-risk bloom expansion. California experienced a slight decrease in CyanoHAB extent, mainly in Northern California. In Ohio (excluding Lake Erie), there was little change in CyanoHAB spatial extent. The method successfully categorized bloom areas into three risk levels using WHO thresholds. The study demonstrated that MERIS imagery could detect and quantify CyanoHABs across multiple states. The spatial assessment revealed regional differences in bloom trends. The temporal analysis provided insights into how CyanoHABs changed over the five-year period. The method proved to be transferable and applicable to different geographic areas.

The study concluded that satellite remote sensing can effectively track temporal changes in CyanoHAB spatial extent. The developed method is transferable to different regions and compatible with future satellite instruments. The results highlight regional differences in CyanoHAB trends, with Florida showing the most significant increase. The use of WHO risk categories allowed for a standardized assessment of bloom severity. The method provides a scalable solution for monitoring CyanoHABs across multiple water bodies. The findings suggest that MERIS imagery is suitable for detecting and quantifying CyanoHABs. The approach supports future monitoring efforts using the OLCI instrument on Sentinel-3A/3B. The study demonstrates the potential of satellite data for assessing CyanoHAB risk at a regional scale.