Phytoplankton MARE 444 Lecture 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).

Phytoplankton Group Phycological Terminology Diatoms Bacilliariophyceae Dinoflagellates Dinophyceae Microflagellates Haptophyta, Prymnesiophyta, Chrysomonadales, Cryptomonadales Picoplankton Photoautotrophs < 2μm Cyanobacteria Cyanophyta, photosynth bact. Prochlorococcus Photosynth bacteria Eukaryotic Pico Very small, struct. advanced

Phytoplankton 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 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 Diatoms Microalgae

Diatom Cellular Structure (chrysolaminarin) (chlorophyll a and c, fucoxanthin, etc)

The Diatoms

Planktonic diatoms Silica 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 Characteristics Typically 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 Armored plates (numbers, shapes) Naked size 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

Coccolithophores 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

Prokaryotic Picoplankton Prochlrophyta Often most abundant phtoplankton in oligotrophic, tropical waters Have traits in common with several taxonomic groups bacteria, cyanobacteria, green algae

Eukaryotic Picoplankton Typically green algae (Chlorophyta) Contain chlorophylls a and b, carotenoids, xanthophylls Starch is the food reserve 1, 2, 4, or 8 flagella