Plankton Communities Plankton are free floating and weak swimmers whose position is determined by water movements- phytoplankton and zooplankton Nekton are strong swimmers who are able to determine the position regardless of the water’s movements

Size Classification of Plankton Femtoplantkon - < 0.2 μ m Picoplankton to 2 μ m Nanoplankton - 2 to 20 μ m Microplankton - 20 to 200 μ m Macroplankton to 2000 μ m Megaplankton - > 2000 μ m

Size Classification of Plankton Femtoplankton – mostly viruses Picoplankton phototrophic bacteria and cyanobacteria prochlorophytes heterotrophic bacteria chemoautotrophic bacteria eukaryotic picoflagellates Nanoplankton heterotrophic nanoflagellates (HNANs) small prokaryotic and eukaryotic phytoplankton Microplankton prokaryotic and eukaryotic phytoplankton heterotrophic flagellates and ciliates most small zooplankton and larvae Note that the size relationship between bacteria and a ciliate is like krill is to a whale!

Plankton are usually separated into categories based on their size.

Community Composition Come in all shapes and sizes (morphology and size limitations) single cells, chains, filaments some are mixotrophic (both photo and heterotrophic) Major Groups Non-MotileMotile (flagella) CyanobacteriaChlorophytesPrasinophytes Diatoms Prymnesiophytes Cryptophytes DinoflagellatesEuglenophytes Chrysophytes (coccolithophorids and silicoflagellates) Phytoplankton

Diatoms have heavy silicified (pectin and amorphous silica) frustules Are heavy than water, sink rapidly Usually the most abundant group (>80% of biomass) in estuarine and near-coastal waters Phytoplankton From Sverdrup et al. 2004

Diatoms From Phytopia Chaetoceros debilis Chaetoceros socialis Ditylum brightwellii Thalassionema sp. Phytoplankton

Phytoplankton Dinoflagellates Have 2 flagella Many species are mixotrophic Most harmful algal species are dinoflagellates From Sverdrup et al. 2004

From Phytopia Phytoplankton Dinoflagellates Dinophysis sp. Protoperidinim divergens

Paralytic Shellfish Poisoning Neurotoxic Shellfish Poisoning Brown Tide Blooms Amnesic Shellfish Poisoning Pseudonitszia Harmful Algal Blooms Pfiesteria piscicida

Microflagellates Phytoplankton From Miller 2004 Chlorophyceae Cryptophyceae Chrysophyceae Haptophyta Prasinophyceae

Phytoplankton Picoplankton Are some of the smallest primary producers (0.2 – 2 µm dia.) Were not discovered until the early 1980’s Important contributors to oceanic primary production Are usually most abundant at the chlorophyll max in the open ocean Major groups are… Cyanobacteria (Synechococcus) Prochlorophytes (Prochlorococcus)

Picoplankton DAPI DNA stain Epifluorescent Microscope Under UV light Particles contain DNA DAPI DNA stain Epifluorescent Microscope Under blue light Red cells are Prochlorococcus Yellow cells are Synechococcus Big yellow cell is a dinoflagellate From Kaiser et al. 2005

Prochlorophytes  Very recently discovered, prochlorophytes are extremely small photosynthetic organisms that are the most abundant plants (by cell #) on earth.  These tend to live in deeper waters near the base of the sunlit layer.

Prochlorophytes Cryptophytes Chl a + c a-carotene Phycobilins Chl a + b b-carotene Xanthophylls

In most estuaries, Nanoplankton have the highest biomass and primary production In oligotrophic habitats, Picoplankton have the highest biomass and primary production Occasional blooms of microphytoplankton occur under nutrient enriched conditions Phytoplankton

Benthic Microalgae (microphytobenthos ) Production: up to 2kg C m -2 yr -1 Very high biomass: 0.1(?) kg C m -2 Turnover (P/B): ~20(?)

Dinoflagellates: Naked and Armored Cell densities up to l -1 (Blooms) Coastal Phytoplankton Production: up to 0.5 kg C m -2 yr -1 Low biomass: 0.02 kg C m -2 HIGH Turnover (P/B): ~25 Chl a + c b-carotene xanthophylls (peridinin)

‘Blue-green algae Trichodesmium N 2 fixation Heterocyst Cell densities up to l -1 (Blooms) Shelf-Oceanic Phytoplankton Production: up to 0.1 kg C m -2 yr -1 Very low biomass: kg C m -2 VERY HIGH Turnover (P/B): ~40 Chl a b-carotene Phycobilins (phycocyanin)

23 Feb 1997 ~50% Production trapped on the continental shelf

Abundances General trends: Phytoplankton most abundant near coasts, decreasing with distance Where seasonal effects are important (higher attitudes), highest abundances in springtime

Coccolithophores CaCO 3

~50% spread over vast ocean