The date indicates the season we’re in: spring (end of March to end of June), summer (end of June to end of September), fall (end of Sept to end of December), winter (end of December to end of March). The season makes a big difference in what you find in your plankton sample. Spring is a very windy season in the Monterey Bay. The winds cause an upwelling in the Bay. An upwelling happens when the warmer water on the surface of the ocean is pushed away by the wind and the colder water from deep in the Monterey Canyon is stirred up to the surface. Most zooplankton like to live in very cold water, while most phytoplankton need to live at the surface in order to be exposed to the sunlight. As a result, during the spring upwelling you will find more zooplankton mixed in with the phytoplankton near the surface of the water.
During the rainy winter season, the salinity of the water may change. Runoff from rivers and streams adds nutrients to the water that can affect the type of plankton you find.
Phytoplankton lives on the surface where there is lots of sunlight.
The kelp grows faster in the summer because the days are longer and the sun is warmer.
The surface water is warmer in the winter before the spring upwelling brings the cold water from the Monterey Canyon to the surface.