Chlorophyll-a is a widely used proxy for phytoplankton biomass and an indicator for changes in phytoplankton production. As an essential source of energy in the marine environment, the extent and availability of phytoplankton biomass can be highly influential for fisheries production and dictate trophic-structure in marine ecosystems. Changes in phytoplankton biomass are predominantly effected by changes in nutrient availability, through either natural (e.g. turbulent ocean mixing) or anthropogenic (e.g. agriculture runoff) processes. This layer represents the standard deviation (STD) of 8-day time series of Chlorophyll (mg/m3) from 2002 - 2013. Monthly and 8-day, 4 km (0.0417 degree) spatial resolution data were obtained from the MODIS (moderate resolution imaging spectroradiometer) Aqua satellite from the NASA OceanColor Web (http://oceancolor.gsfc.nasa.gov/cms/). This layer was developed as part of a geospatial database of key anthropogenic pressures to coastal waters of the Main Hawaiian Islands for the Ocean Tipping Points project (http://oceantippingpoints.org/). Ocean tipping points occur when shifts in human use or environmental conditions result in large, and sometimes abrupt, impacts to marine ecosystems. The ability to predict and understand ocean tipping points can enhance ecosystem management, including critical coral reef management and policies to protect ecosystem services produced by coral reefs. The goal of the Ocean Tipping Points Hawaii case study was to gather, process and map spatial information on environmental and human-based drivers of coral reef ecosystem conditions. Please contact the Ocean Tipping Points project in advance of applying these data sets to project work so the PI can track and communicate data uses and ensure no duplicate efforts are underway. When applying these data for publication, please reference and cite the complete journal article, Wedding et al. 2017. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.