Biology Now, 2e

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distinctive ways in which it functions, especially

the means by which energy and nutrients are

acquired and distributed by the biotic community.

The activity of primary producers, in partic-

ular, profoundly influences the characteristics

of an ecosystem. Ecologists often describe an

ecosystem according to the types of producers it

contains and the consumers that the producers

support. A duckweed-covered pond, a tallgrass

prairie, and a beech-maple woodland are all

examples of ecosystems that can be defined by

the specific types of producers that capture and

supply energy to consumers.

To see how overfishing was affecting food

chains in the ocean, Boyce first looked to the

primary producers of the ocean ecosystem:

phytoplankton. These small, floating microal-

gae come in a fantastic array of shapes and sizes,

from smooth orbs to segmented spirals to pointy

crescents (Figure 21.2). Phytoplankton are

primarily microscopic, but in large groups they

form the green color often seen in water. The

more phytoplankton in the water, the greener the

water is; the less phytoplankton, the bluer it is.

Phytoplankton are green because they are

photosynthetic: they convert light energy from

the sun into chemical energy using chloro-

phyll, the green pigment critical to the process

Figure 21.2

Phytoplankton bloom

The turquoise area in this aerial photo is a phytoplankton bloom occurring off the coast of Norway.

When a population of phytoplankton (inset) increases rapidly, it discolors the water in which it resides.

Daniel Boyce (left) is a postdoctoral researcher

at Queen’s University in Ontario, Canada. As a

graduate student with Boris Worm (right),

he studied the amount of phytoplankton

biomass in the ocean. Boris Worm is a

marine biologist at Dalhousie University

in Nova Scotia, Canada, studying global

marine biodiversity.

DANIEL BOYCE AND BORIS WORM