Spring officially started with last week’s vernal equinox. Now, we will start to tilt more toward the sun, meaning more light and warmer temperatures. You may have noticed shoots poking up from the softening ground – bright purple crocus even blooming on the south-facing sides of some lots. There are now buds on trees that have looked brittle and lifeless for so many months.

While you might not notice colorful signs of spring in the ocean, things are beginning to shift underwater as well. As the ice melts and the sun’s radiation increases, things start to get a bit unbalanced. Conditions on the surface become quite different from those beneath. The warmer and often fresher water floats on top of the colder saltier water and becomes an incubator for new life. Here, the tiny plants called phytoplankton absorb the sun’s energy and multiply like crazy. This is known as the spring phytoplankton bloom.

The spring phytoplankton bloom in the Gulf of Maine typically occurs sometime in April. Sometimes it is so strong that you can see it locally – the water taking on a slightly spring-y yellow-green color. in the Gulf of Maine, some of the common species found during the spring phytoplankton bloom are diatoms. Diatoms are amazingly varied and beautiful single-celled living things that are housed in clear glass shells of myriad shapes and sizes, sometimes even linked together to form bizarre communities. Dinoflagellates are another common occurrence in plankton blooms. They have tiny tails that propel them through the water. There’s an amazing guide to plankton in the Gulf of Maine with great photos here.

When plankton blooms aren’t always visible close-up, you can see them clearly via satellite. The University of Maine has images of chlorophyll concentration, a measure of plant growth, that let you see the color difference between March and April (www.seasurface.umaine.edu) when the concentrations skyrocket.

Satellites aren’t the only way to monitor the changes in the water that happen in the spring. There is also an array of ocean buoys that collect information on temperature, salinity, and ocean currents. Similar to the ocean exploration technology I wrote about last week – deep sea rovers similar to that on Mars,

these ocean buoys are floating tech-wizards equipped with sensors of all types, including the ability to record temperatures at different depths in the water column. The 10 buoys in the Gulf of Maine are a part of what is known as GoMOOS, the Gulf of Maine Ocean Observation System, which are part of the larger NERACOOS (Northeastern Regional Association of Coastal and Ocean Observing System) system. You can look up real-time data from any of these buoys on the website (www.neracoos.org). There’s even a buoy close enough to shore that you can see it in Harpswell Sound off of Bowdoin’s Schiller Coastal Studies Center on Orr’s Island (bowdoin.loboviz.com). This information can be helpful for anyone heading out on the water.

While we haven’t hit the bloom yet, keep watching for signs of spring along the coast and check out some of the technology and information being collected out and over the water to help better understand these seasonal shifts.