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 PlanktonSize Classification of Plankton

• Femtoplantkon - < 0.2 μm

• Picoplankton - 0.2 to 2 μm

• Nanoplankton - 2 to 20 μm

• Microplankton - 20 to 200 μm

• Macroplankton - 200 to 2000 μm

• Megaplankton - > 2000 μm

Size Classification of PlanktonSize 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-Motile Motile (flagella)

Cyanobacteria Chlorophytes PrasinophytesDiatoms Prymnesiophytes

CryptophytesDinoflagellates EuglenophytesChrysophytes (coccolithophorids

and silicoflagellates)

PhytoplanktonPhytoplankton

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

PhytoplanktonPhytoplankton

From Sverdrup et al. 2004

DiatomsDiatomsFrom Phytopia

Chaetoceros debilis

Chaetoceros socialis

Ditylum brightwellii

Thalassionema sp.

PhytoplanktonPhytoplankton

PhytoplanktonPhytoplankton

DinoflagellatesDinoflagellatesHave 2 flagellaMany species are mixotrophicMost harmful algal species are dinoflagellates

From Sverdrup et al. 2004

From Phytopia

PhytoplanktonPhytoplankton

DinoflagellatesDinoflagellates

Dinophysis sp.

Protoperidinim divergens

Paralytic Shellfish Poisoning

Neurotoxic Shellfish Poisoning

Brown Tide Blooms

Amnesic Shellfish Poisoning

Pseudonitszia

Harmful Algal Blooms

Pfiesteria piscicida

MicroflagellatesMicroflagellates

PhytoplanktonPhytoplankton

From Miller 2004

Chlorophyceae

Cryptophyceae

ChrysophyceaeHaptophyta

Prasinophyceae

PhytoplanktonPhytoplankton

PicoplanktonPicoplankton• 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)

http://plantbio.berkeley.edu/~volkman/courses/MCB116Slides/Lec1Slide19.jpg

PicoplanktonPicoplankton

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 + ca-carotenePhycobilins

Chl 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

PhytoplanktonPhytoplankton

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 104-106 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 + cb-carotenexanthophylls (peridinin)

‘Blue-green algaeTrichodesmiumN2 fixation

Heterocyst

Cell densities up to 101-103 l-1 (Blooms)

Shelf-Oceanic Phytoplankton

• Production: up to 0.1 kg C m-2 yr-1

• Very low biomass: 0.003 kg C m-2

• VERY HIGH Turnover (P/B): ~40

Chl ab-carotenePhycobilins (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

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