Chlorophyll Map

Chlorophyll is the green pigment inside phytoplankton, the microscopic plants that form the base of the ocean food web. Where there's more chlorophyll, there's more phytoplankton, which usually means more small fish feeding on it, more bigger fish feeding on those, and sometimes more algae than anyone wants. This map shows chlorophyll concentration in color, built from the same satellites that watch the whole ocean every day.

Reading the Color Scale

The scale on this map is fixed from 0.01 to 100 milligrams per cubic meter, and it runs on a logarithmic curve rather than a straight line, because chlorophyll in the real ocean spans that entire range. Deep blue and purple mean very little chlorophyll — clear, nutrient-poor water. Green, yellow, orange, and red mean progressively more: water rich in phytoplankton, sometimes rich enough to be an algae bloom. Coastal water along the Gulf of Mexico, for example, can swing from clear blue to a visible red tide within days, and that shift shows up in the chlorophyll color before you'd necessarily notice it from shore.

Why Chlorophyll Shows Up Where It Does

Phytoplankton needs sunlight and nutrients to grow, and those two things don't line up everywhere in the ocean. Nutrients tend to sit in deeper water, out of reach of the sunlight phytoplankton needs at the surface. Where wind or currents pull that deeper, nutrient-rich water up toward the surface — a process called upwelling, common along parts of the California coast and a handful of other coastlines worldwide — phytoplankton blooms, and chlorophyll readings climb. It's the same reason those upwelling zones tend to support more baitfish, and in turn more of the bigger fish that eat them.

Where the Data Comes From

The color you see by default is a composite, blended from multiple satellite instruments and published once a day by NASA and NOAA. For a closer look, the map can also show one individual pass instead of that blend — a single snapshot from VIIRS, which flies on three NOAA polar-orbiting satellites (S-NPP, NOAA-20, and NOAA-21; S-NPP stands for Suomi National Polar-orbiting Partnership), or from MODIS, an older sensor NASA still operates aboard its Aqua satellite. Nothing in a pass is smoothed over — cloud gaps and all, it's exactly what that satellite saw at that moment.

What Your Account Sees

Account tier controls how current this map is. Skip signing in and you're looking at composites held back at least 48 hours. A free account removes that delay — the composite is fully current the moment it's published. A paid plan adds individual satellite passes on top of that, plus buoy readings and alerts for the region or regions your plan covers.

Who This Is For

Anyone curious about ocean color and productivity will get something out of this map — students, coastal residents watching for algae blooms, researchers doing a first-pass look at a region. Offshore anglers and divers read the same chlorophyll data for more specific reasons: chlorophyll edges concentrate baitfish, and chlorophyll concentration is also the basis for estimating underwater visibility, which we cover in detail on our ocean water clarity page, which draws on the same conversion we cover in full in our article on estimating dive visibility from satellite data. The upwelling behavior described above shows up clearly along Central California and the western Gulf of Mexico, two regions worth watching if you want to see this pattern in practice.