Phytoplankton Photosynthetic autotrophs (algae) drifting passively in aquatic environmentsPhotosynthetic autotrophs (algae) drifting passively in aquatic environments –Nanoplankton 2-20 um –Net plankton um Some common phyla: –Euglenophyta (euglenoids) –Pyrrhophyta (dinoflagellates) –Bacillariophyta (diatoms) –Chlorophyta (green algae) Scenedesmus

 On the bottom (benthic or “epipelic” algae) Good access to nutrients in sediments, but can only be in shallow water due to light limitation Good access to nutrients in sediments, but can only be in shallow water due to light limitation epilithic - rock epilithic - rock epipsammic - sand epipsammic - sand  Attached to aquatic macrophytes (periphyton) Algae and animals form a community (the Aufwuchs) in the “slime” on stems of aquatic plants Algae and animals form a community (the Aufwuchs) in the “slime” on stems of aquatic plants  In the water column (phytoplankton) Where are algae found?

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 Watersampler

Plankton counting techniques Sedgewick-Rafter Counting Cells Palmer

The number of species recorded from the same water body depends on…. Sampling method (net or water samples)Sampling method (net or water samples) Number and location of sampling stationsNumber and location of sampling stations (littoral vs. pelagic; presence of floating macrophytes, etc.) Time span of the investigationTime span of the investigation Time of the year (and time of the day)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).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).Even so, there seems no trend towards increased algal diversity towards the equator (applies to lakes, rivers, wetlands and reservoirs).

Euglenophyta Euglena Phacus

Ceratium Dinoflagellates (Pyrrhophyta)

Red Tide: A bloom of dinoflagellates

Diatoms (Bacillariophyta) Cyclotella Navicula

protist.i.hosei.ac.jp/pdb/Images/Heterokont ophyta/Centrales/Cyclotella/Cyclotella.jpg microbes.limnology.wisc.edu/outreach/images dr-ralf-wagner.de/Bilder/Surirella plantphys.info/organismal/lechtml/images/navicula.jpg Centric Diatoms Pennate Diatoms

Diatom shell

Single celled, colonial and multicellular chlorophytes Pediastrum Volvox Caulerpa

Periphyton growing along rocks in mesotrophic Lake Titicaca, Peru)

Source: Downing et al N is more frequently limiting to freshwater production in tropical lakes and rivers. 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