The word "plankton" means drifter, and refers to plants or animals that aren't strong enough to swim against a current. These plants and animals are among the most numerous life forms on the planet. Because of their importance to all other life forms, plankton are an important part of the curriculum we provide to thousands of students who come to Rookery Bay Environmental Learning Center.
Phytoplankton, or plant plankton, is one of the major bases of the food web in the estuary. It is also responsible for producing more than 80% of Earth's oxygen!
Phytoplankton is typically too small to catch in our plankton nets although we occasionally encounter beautiful varieties of algae or diatoms. Our nets are specifically designed to catch zooplankton, or drifting animals.
Zooplankton consist of a wide variety of animals. Some remain in their planktonic state for their entire lives, like copepods or sea jellies (jellyfish), while others grow and change form to things we are much more familiar with like barnacles, crabs and many species of fish.
View the video below to see live plankton through a microscope!
Volvox is a freshwater phytoplankton (microalgae that contains chlorophyll) that takes advantage of the seasonal lower salinity in Henderson Creek – they perish in higher salinities. These colonial organisms are amazing in so many ways. They are remarkably light sensitive and will move in the direction of a light source (i.e. the sun).
When the light source is diffuse the volvox move in many directions and at varying speeds.
The volvox in the video with the black background seem beautifully synchronized as they all move towards a single light source. “Positive phototaxis” is the name for an organisms movement towards the light. Moving towards light is vitally important for algae so they can photosynthesize and produce that wonderful byproduct that we all depend on – oxygen! Volvox have cilia all over their bodies that help propel them through the water. They can be made up of tens of thousands of cells. They have cells with cilia all around the outside of their “globe.” They can reproduce sexually or asexually and appear to do more of the latter when conditions are ideal.
“Daughter cells,” or asexually produced offspring, are clearly visible as miniature versions of mature cells in these photos. The daughter cells will then emerge, grow, and disperse their own daughter cells and therefore the population can explode fairly quickly when conditions are optimal.
Rotifers get their name from the moving cilia (hair-like structures) located around their “corona” that make it look like a spinning electric razor head. This particular variety of rotifer is one that can form colonies in the shape of a ball whereas the majority of rotifers are individual animals. Each pulsing “suction cup” is the corona of one individual rotifer and the cilia set up the powerful (on a microscopic scale) currents that pull food and other objects towards their bodies.