Plankton CommunitiesPlankton are free floating and weak swimmers whose position is determined by water movements- phytoplankton and zooplanktonNekton are strong swimmers who are able to determine the position regardless of the waters movements

Size Classification of Plankton

Femtoplantkon - < 0.2 m Picoplankton - 0.2 to 2 m Nanoplankton - 2 to 20 m Microplankton - 20 to 200 m Macroplankton - 200 to 2000 m Megaplankton - > 2000 m

Size Classification of Plankton Femtoplankton mostly viruses Picoplanktonphototrophic bacteria and cyanobacteriaprochlorophytesheterotrophic bacteriachemoautotrophic bacteriaeukaryotic picoflagellates Nanoplanktonheterotrophic nanoflagellates (HNANs)small prokaryotic and eukaryotic phytoplankton Microplanktonprokaryotic and eukaryotic phytoplanktonheterotrophic flagellates and ciliatesmost small zooplankton and larvaeNote 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 CompositionCome in all shapes and sizes (morphology and size limitations) single cells, chains, filamentssome are mixotrophic (both photo and heterotrophic)

Major GroupsNon-MotileMotile (flagella)CyanobacteriaChlorophytesPrasinophytesDiatoms PrymnesiophytesCryptophytesDinoflagellatesEuglenophytesChrysophytes (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) inestuarine and near-coastal waters

PhytoplanktonFrom Sverdrup et al. 2004

DiatomsFrom PhytopiaChaetoceros debilisChaetoceros socialisDitylum brightwelliiThalassionema sp.Phytoplankton

PhytoplanktonDinoflagellatesHave 2 flagellaMany species are mixotrophicMost harmful algal species are dinoflagellatesFrom Sverdrup et al. 2004

From PhytopiaPhytoplanktonDinoflagellatesDinophysis sp.Protoperidinim divergens

Pfiesteria piscicida

MicroflagellatesPhytoplanktonFrom Miller 2004ChlorophyceaeCryptophyceaeChrysophyceaeHaptophytaPrasinophyceae

PhytoplanktonPicoplankton Are some of the smallest primary producers (0.2 2 m dia.) Were not discovered until the early 1980s Important contributors to oceanic primary production Are usually most abundant at the chlorophyll max in the open ocean Major groups areCyanobacteria (Synechococcus)Prochlorophytes (Prochlorococcus)http://plantbio.berkeley.edu/~volkman/courses/MCB116Slides/Lec1Slide19.jpg

PicoplanktonDAPI DNA stainEpifluorescent MicroscopeUnder UV lightParticles contain DNADAPI DNA stainEpifluorescent MicroscopeUnder blue lightRed cells are ProchlorococcusYellow cells are SynechococcusBig yellow cell is a dinoflagellateFrom Kaiser et al. 2005

Prochlorophytes CryptophytesChl a + ca-carotenePhycobilinsChl a + bb-caroteneXanthophylls

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-1Very high biomass: 0.1(?) kg C m-2Turnover (P/B): ~20(?)

Dinoflagellates: Naked and ArmoredCell densities up to 104-106 l-1 (Blooms)Coastal PhytoplanktonProduction: up to 0.5 kg C m-2 yr-1Low biomass: 0.02 kg C m-2HIGH Turnover (P/B): ~25Chl a + cb-carotenexanthophylls (peridinin)

Blue-green algaeTrichodesmiumN2 fixationHeterocystCell densities up to 101-103 l-1 (Blooms)Shelf-Oceanic PhytoplanktonProduction: up to 0.1 kg C m-2 yr-1Very low biomass: 0.003 kg C m-2VERY HIGH Turnover (P/B): ~40Chl ab-carotenePhycobilins (phycocyanin)

~50% Production trapped on the continental shelf

Trends with distance

Species composition varies with distance from land. Near-shore waters dominated by diatoms. Offshore waters have much higher percentages of dinoflagellates and coccolithophorids.

Note: This picture can change with season and conditions.

CoccolithophoresCaCO3

~50% spread over vast ocean

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