A few words about plankton

Plankton comes from the Greek word planktos meaning “wanderer” or “drifter”. As a group, plankton are an eclectic collection of organisms adrift in the oceanic waters. The classification of an organism as ‘plankton’ has nothing to do with its biological grouping, but rather with its inability to swim actively against oceanic currents.

Plankton vary widely in size from thousandths of an inch (0.05 mm) or less to several feet in length (> 1m) or more. Most are less than an inch (~ 2.5 cm). Some organisms spend all their life as plankton and drift along with the ocean currents, while others are only temporary passive passengers until they reach a certain size and age, allowing for movement in the open ocean or settlement into a coastal habitat.

There are two main types of plankton: phytoplankton (plants) and zooplankton (animals). We are most interested in the zooplankton because our underwater camera system is optimized to capture the image of larger planktonic organisms, ranging from a few mm to a few centimeters which includes a wide variety of different organisms.

Why study plankton?

Planktonic organisms are a critically important food source in the ocean. Small phytoplankton form the beginning of the food supply which are consumed by larger plankton, then those plankton by larger organisms all the way up to fish and the largest species of whales found in the sea. No plankton: no life in the ocean.

Plankton also play an important role in the global carbon cycle capturing the sun’s energy and the atmosphere’s CO2 at the surface of the ocean and releasing it, via the above food chain, to other organisms and other areas of the ocean from shallow coastal areas to the deep ocean basins.

Understanding where and when plankton occur at different depths in the ocean allows scientists to get a global understanding of the function and health of the ocean from small to global scales.

Plankton are also fascinating in their diversity of intricate and beautiful shapes. The weightlessness of life in the ocean environment allows for very delicate and complex body designs, which are almost impossible to keep intact with normal means of collection. Imaging systems provide a first glimpse of these amazing animals in their natural environment, and may even lead to discovery of new species.

How do we get the images?

The In Situ Ichthyoplankton Imaging System (ISIIS) is one of a few systems in the world capable of improving the way we study plankton to better understand their life and function in the marine environment. ISIIS is, in some ways, a “virtual net” which captures the images of the organisms and information about their immediate surroundings. By sampling continuously, the result is a collection of digital images that record the exact location of the various plankton organisms in relation to each other and the environment in which they live. Further, the images are recorded onto a simple hard drive instead of slurry of plankton all mixed together in a sample jar with formaldehyde (yech!).

ISIIS is composed of a macro-camera system with its own illumination and is integrated into an underwater vehicle with a variety of additional sensors to measure the depth, salinity and temperature of the water, as well as such properties as dissolved oxygen, light level, and even how much chlorophyll a (measure of primary production) is present. Together, the camera and sensors provide detailed profiles and tracks of what plankton are where and what the ocean environment around them is like.