Transcript Biota of Aquatic Environemnts

Phytoplankton
• Photosynthetic autotrophs (algae) drifting
passively in aquatic environments
– Nanoplankton 2-20 um
– Net plankton 20-200 um
Some common phyla:
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Euglenophyta (euglenoids)
Pyrrhophyta (dinoflagellates)
Bacillariophyta (diatoms)
Chlorophyta (green algae)
Scenedesmus
Where are algae found?
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On the bottom (benthic or “epipelic” algae)
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Attached to aquatic macrophytes (periphyton)
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Good access to nutrients in sediments, but can only be
in shallow water due to light limitation
epilithic - rock
epipsammic - sand
Algae and animals form a community (the Aufwuchs) in
the “slime” on stems of aquatic plants
In the water column (phytoplankton)
Phytoplankton
• Pigments
– Often used to categorize phytoplankton
– All photosynthetic algae possess photosynthetic
pigments.
• Chlorophylls - Chla in all algae; also b and c (absorb blue, red)
• Carotenoids - carotenes, xanthophylls (absorb blue, green)
• Phycobilins - pigment – bonded to proteins (absorb green,
yellow, orange, red)
– Similar pigments usually indicates evolutionary
relationships
• Special adaptations
– Flagellae
• motility (slight)
Green Algae
Chlamydomonas
Absorption spectra for different algal pigments
Plankton sampling techniques
Plankton net
Water
sampler
Plankton counting techniques
Sedgewick-Rafter
Counting Cells
Palmer
Counting Cells
The number of species recorded from the
same water body depends on….
• Sampling method (net or water samples)
• Number and location of sampling stations
(littoral vs. pelagic; presence of floating
macrophytes, etc.)
• Time span of the investigation
• Time of the year (and time of the day)
Phytoplankton communities in the tropics
• Lack of comprehensive data on
phytoplankton communities in the tropics
(most citations deal with reef algae, toxins and control of algae in aquaria).
• Even so, there seems no trend towards
increased algal diversity towards the
equator (applies to lakes, rivers, wetlands
and reservoirs).
Euglenophyta
Euglena
Phacus
Dinoflagellates (Pyrrhophyta)
Ceratium
Red Tide: A bloom of dinoflagellates
Diatoms (Bacillariophyta)
Cyclotella
Navicula
Diatoms (Bacillariophyta)
Centric Diatoms
microbes.limnology.wisc.edu/outreach/images
protist.i.hosei.ac.jp/pdb/Images/Heterokont
ophyta/Centrales/Cyclotella/Cyclotella.jpg
Pennate Diatoms
dr-ralf-wagner.de/Bilder/Surirella
plantphys.info/organismal/lechtml/images/navicula.jpg
www.ansp.org/research/pcer/images/Eucocconeis
Diatom shell
Single celled, colonial and multicellular chlorophytes
Volvox
Pediastrum
Caulerpa
Periphyton growing along rocks in mesotrophic Lake Titicaca, Peru)
N is more frequently limiting to freshwater production in
tropical lakes and rivers.
Source: Downing et al. 1998
• N may be lost from aquatic systems more rapidly
in the tropics than the temperate zone (e.g. through denitrification)
• P erosion from tropical landscapes and P mobilization
in aquatic environments may be more rapid.
Species: Caulerpa taxifolia
Division: Chlorophyta; Class:Ulvophyceae
Native range: Hawaii, Brazil, SE Asia (i.e., tropical).
Now: Worldwide distribution with large outbreaks after accidental introduction
in the Mediterranean, Southern California and Australia.
Successful invader because: (1) rapid reproduction/spread with fragmentation, (2)
lack of natural grazers, (3) rapid growth, and (4) toxic to herbivores
Lewis, 1990
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