Biota of Lakes and Reservoirs - Hydro-Environmental Analysis: Freshwater Environments - page 417

15.3 CHARACTERISTICS OF ORGANISMS BY ZONE

15.3.1 L IMnetIc z one

15.3.1.1 Phytoplankton
15.3.1.1.1 Ta xonomic Classiicat ion
Phytoplankton in general refers to the assemblage of plants (“phyto”) or autotrophic organisms,
typically microscopic, which are “planktonic” or loat, drift, or weakly swim in the water column
(including the pelagic zone). Various general schemes have been used to classify phytoplankton, one
example of which is that some models subdivide phytoplankton into blue-green algae, green algae,
brown algae, and diatoms. To understand the implications of this classiication, let us irst revisit the
system of the taxonomic classiication of organisms.
There are a variety of variations in taxonomic classiication systems, but most modern systems
are based on that irst established by Carl Linnaeus in his Systema Naturae (1735; Figure 15.6).
Today, most taxonomists organize organisms into ranks, based on similarities in their structure.
The highest rank is typically the domain, which is then further subdivided into lower ranks down

FIGURE 15.6 Systema Naturae by Carl Linnaeus (1735).