56
fungi, algae, protozoa, and animals. Viruses and bacteria
(virio- and bacterioplankton) as well as archaea belong to
femto- and picoplankton, which range from 0.02 to 0.2 μm
and 0.2 to 2.0 μm in size, respectively. Mycoplankton (fungi)
can mostly be found within nanoplankton (2.0–20 μm).
Phytoplankton spans from picoplankton up to microplankton
(2–200 μm), whereas zooplankton, in rare cases, can reach
up to 200 cm (megaplankton).
The high diversity of phytoplankton extends from prokaryotes (cyanobacteria) to several groups of eukaryotes.
Classification of phytoplankton groups constantly changes
due to the increasing amount of molecular phylogenetic
studies and is under constant flux of opinion (e.g., Parfrey
et al. 2006). Cyanobacteria have been traditionally classified
using morphological features. However, due to the different
scientific communities, the bacterial classification is not easily comparable with the phycological taxonomy. In the last
decades, several new concepts have been introduced (see
e.g., Hoffmann et al. 2005; Komárek 2010; Komárek et al.
2014). With new approaches that are based on molecular
techniques and the arising problems to integrate this new
information into the classification, there have been several
approaches for reaching a consensus in both communities
(e.g., Komárek 2006; Palinska and Surosz 2014). So far, all
major cyanobacterial groups, even cyanobacteria that have
been categorized as freshwater species, can be found in the
marine environment (Burja et al. 2001; Paerl 2012).
Adl et al. (2005) revised the classification of protozoa
from Levine et al. (1980) and expanded it to other protists in
the name of the International Society of Protistologists. They
compared modern morphological approaches, biochemical
pathways and molecular phylogenetics data to create a new
classification. Only 7 years later Adl et al. (2012) revised this
classification. This new revision proposes a division into six
super-groups: Archaeplastida, Amoebozoa, Opisthokonta,
Excavata, and SAR (Stramenopila, Alveolata, and Rhizaria).
Throughout the last years, the concept of different supergroups has been applied for the eukaryotic phytoplankton.
Changes and uncertainties are still present in the supergroups that are named here. Additionally, several groups of
organisms exist, which do not belong to any of the supergroups, for example some groups of flagellates.
Phytoplankton Taxonomy and Morphology
Depending on area, season, and size class, different groups
can act as dominating organisms in the food web and, therefore, regulate the seasonality of the predators as well. The
most frequent dominating eukaryotic phytoplankton belong
to diatoms (Stramenopila), dinoflagellates (Alveolata) or
haptophytes (also called prymnesiophytes, no super-group)
(Fig. 1). Other groups include Chlorophyta (Archaeplastida),
Cryptophyta, Centrohelida and Telonemia, with the last three
not belonging to any of the super-groups (e.g., Paerl 1988;
Arrigo et al. 1999; Adl et al. 2012).
Diatoms (Bacillariophyta) possess a so-called frustule of
silica that consists of two overlapping valves (hypotheca and
epitheca) and a girdle (cingulum). Reproduction is mostly
asexual. The old cell divides and each daughter cell builds up
a new smaller theca inside the parent wall. If the theca gets
too small for further reproduction the cell dies. Prior to death,
the cell releases auxospores, which grow into new cells.
Another characteristic feature is the symmetry of diatoms.
They are either centric or pennate symmetric. They occur as
single cells or more often in colonies (Gross 1937). Diatoms
are mainly autotrophs, with several heterotrophic strategies
to survive during darkness (e.g., Tuchman et al. 2006;
McMinn and Martin 2013).
Dinoflagellates consist of thecate and athecate groups.
Thecate dinoflagellates possess a cover of cellulose plates in
contrast to athecate dinoflagellates, which are more variable
in shape. Both groups possess two characteristic parts: episome and hyposome. The cells also feature two grooves. A
a)
b)
c)
Fig. 1 Exemplary schematic drawings of three important phytoplankton groups. (a) Triangular diatom Trigonium sp., (b) dinoflagellate
Pyrodinium bahamense and (c) coccolithophorid Emiliania huxleyi
(prymnesiophytes). (Adapted from the open source Plankton*Net Data
Provider at the Alfred Wegener Insitute for Polar and Marine Research
(a) and (c), and from Landsberg et al. (2006) (b))
L. Käse and J. K. Geuer
fungi, algae, protozoa, and animals. Viruses and bacteria
(virio- and bacterioplankton) as well as archaea belong to
femto- and picoplankton, which range from 0.02 to 0.2 μm
and 0.2 to 2.0 μm in size, respectively. Mycoplankton (fungi)
can mostly be found within nanoplankton (2.0–20 μm).
Phytoplankton spans from picoplankton up to microplankton
(2–200 μm), whereas zooplankton, in rare cases, can reach
up to 200 cm (megaplankton).
The high diversity of phytoplankton extends from prokaryotes (cyanobacteria) to several groups of eukaryotes.
Classification of phytoplankton groups constantly changes
due to the increasing amount of molecular phylogenetic
studies and is under constant flux of opinion (e.g., Parfrey
et al. 2006). Cyanobacteria have been traditionally classified
using morphological features. However, due to the different
scientific communities, the bacterial classification is not easily comparable with the phycological taxonomy. In the last
decades, several new concepts have been introduced (see
e.g., Hoffmann et al. 2005; Komárek 2010; Komárek et al.
2014). With new approaches that are based on molecular
techniques and the arising problems to integrate this new
information into the classification, there have been several
approaches for reaching a consensus in both communities
(e.g., Komárek 2006; Palinska and Surosz 2014). So far, all
major cyanobacterial groups, even cyanobacteria that have
been categorized as freshwater species, can be found in the
marine environment (Burja et al. 2001; Paerl 2012).
Adl et al. (2005) revised the classification of protozoa
from Levine et al. (1980) and expanded it to other protists in
the name of the International Society of Protistologists. They
compared modern morphological approaches, biochemical
pathways and molecular phylogenetics data to create a new
classification. Only 7 years later Adl et al. (2012) revised this
classification. This new revision proposes a division into six
super-groups: Archaeplastida, Amoebozoa, Opisthokonta,
Excavata, and SAR (Stramenopila, Alveolata, and Rhizaria).
Throughout the last years, the concept of different supergroups has been applied for the eukaryotic phytoplankton.
Changes and uncertainties are still present in the supergroups that are named here. Additionally, several groups of
organisms exist, which do not belong to any of the supergroups, for example some groups of flagellates.
Phytoplankton Taxonomy and Morphology
Depending on area, season, and size class, different groups
can act as dominating organisms in the food web and, therefore, regulate the seasonality of the predators as well. The
most frequent dominating eukaryotic phytoplankton belong
to diatoms (Stramenopila), dinoflagellates (Alveolata) or
haptophytes (also called prymnesiophytes, no super-group)
(Fig. 1). Other groups include Chlorophyta (Archaeplastida),
Cryptophyta, Centrohelida and Telonemia, with the last three
not belonging to any of the super-groups (e.g., Paerl 1988;
Arrigo et al. 1999; Adl et al. 2012).
Diatoms (Bacillariophyta) possess a so-called frustule of
silica that consists of two overlapping valves (hypotheca and
epitheca) and a girdle (cingulum). Reproduction is mostly
asexual. The old cell divides and each daughter cell builds up
a new smaller theca inside the parent wall. If the theca gets
too small for further reproduction the cell dies. Prior to death,
the cell releases auxospores, which grow into new cells.
Another characteristic feature is the symmetry of diatoms.
They are either centric or pennate symmetric. They occur as
single cells or more often in colonies (Gross 1937). Diatoms
are mainly autotrophs, with several heterotrophic strategies
to survive during darkness (e.g., Tuchman et al. 2006;
McMinn and Martin 2013).
Dinoflagellates consist of thecate and athecate groups.
Thecate dinoflagellates possess a cover of cellulose plates in
contrast to athecate dinoflagellates, which are more variable
in shape. Both groups possess two characteristic parts: episome and hyposome. The cells also feature two grooves. A
a)
b)
c)
Fig. 1 Exemplary schematic drawings of three important phytoplankton groups. (a) Triangular diatom Trigonium sp., (b) dinoflagellate
Pyrodinium bahamense and (c) coccolithophorid Emiliania huxleyi
(prymnesiophytes). (Adapted from the open source Plankton*Net Data
Provider at the Alfred Wegener Insitute for Polar and Marine Research
(a) and (c), and from Landsberg et al. (2006) (b))
L. Käse and J. K. Geuer