Phytoplankton

MARE 444Lecture 2

Phytoplankton

the majority of the plants in the ocean are planktonic unicellular algae called phytoplankton.

some can be caught be nets, others can only be collected by filtering or centrifugation (e.g., nano- and picoplankton).

PhytoplanktonGroup Phycological TerminologyDiatoms BacilliariophyceaeDinoflagellates DinophyceaeMicroflagellates Haptophyta, Prymnesiophyta,

Chrysomonadales,Cryptomonadales

Picoplankton Photoautotrophs < 2μmCyanobacteria Cyanophyta, photosynth bact.ProchlorococcusPhotosynth bacteriaEukaryotic Pico Very small, struct. advanced

Vital role in marine food chain

4000 species of phytoplankton have been described, new species are continually being described

At least 13 classes of marine phytoplankton are distinguished, representing a wide variety of organisms

Phytoplankton

Phytoplankton

Phytoplankton account for about half of global primary production

Types of Phytoplankton

Bacteria and cyanobacteria

Diatoms

Dinoflagellates

Others

Photosynthetic Bacteria and Cyanobacteria

Photosynthetic Bacteria

Prokaryotic (Kingdom Monera)

Contain bacterial chlorophyll (different from the other chlorophyll molecules)

Cyanobacteria

Prokaryotic (Kingdom Monera)

Contain chlorophyll-a (like eukaryotic autotrophs)

Cyanobacteria

Important primary producers

Small size (1-2μm)- large SAV ratio

Sink or rise very slowly

Maximize nutrient absorption

Reduces grazing loss

Cyanobacteria

Distribution

A cyanobacteria bloom

The DiatomsMicroalgae

Diatom Cellular Structure

(chrysolaminarin)

(chlorophyll a and c, fucoxanthin, etc)

The Diatoms

Planktonic diatomsSilica shell and lack of flagella = sinking

diatoms evolved various strategies to counter sinking

chains

spines

oil droplets

ionic regulation - internal ion concentration is lower than external seawater = reduction in density

Diatoms with elaborate spines and processes

Functions:

The Dinoflagellates

Dinoflagellate CharacteristicsTypically 2 flagella

Large nucleus (looks like a fingerprint)

Chlorophylls a and c

Accessory pigments (ß-carotene, peridinin, xanthophylls)

Food reserve is starch

Dinoflagellate Characteristics

Some have:

Dinoflagellate Characteristics

Some are autotrophic, others are auxotrophic, others are mixotrophic, others are heterotrophic

Dinoflagellate Taxonomy

Armoredplates (numbers, shapes)

Nakedsize and shape

cingular position, displacement, and overhang

sulcal placement and intrusion

presence/shape of apical groove

Dinoflagellate Ecology

Dinos tend to occur in the summer and early fall when nutrients are more depleted and seas are calmer

Microflagellates

Some (e.g., coccolithophorids) are very common

Unicell containing a haptonema between two smooth flagella

Haptonema - a coiled appendage that is used for feeding and sensory purposes

Chlorophylls a, c1, and c2, carotenoids

Chrysolaminarin

Coccolithophores

Single regular calcareous plates

Coccolithophores

Prokaryotic PicoplanktonProchlrophyta

Often most abundant phtoplankton in oligotrophic, tropical waters

Have traits in common with several taxonomic groups

bacteria, cyanobacteria, green algae

Eukaryotic PicoplanktonTypically green algae (Chlorophyta)

Contain chlorophylls a and b, carotenoids, xanthophylls

Starch is the food reserve

1, 2, 4, or 8 flagella