I. Marine Microbes

B. Marine Bacteria1. Autotrophic

a. Photosynthetici. Cyanobacteria• Nitrogen fixation - IMPORTANT• Contain chlorophyll + phycocyanin & phycoerythrin• Occur in a variety of habitats

- Polar bear hair- Endolithic (inside calcareous rocks, coral skeletons)- Epiphytic (on algae or plants)- Endophytic (inside algal or plant cells)

• Some form filaments or mats (aids N fixation)• Some similarities to eukaryotic algae: - Contain chlorophyll a - Produce gaseous O2

• May have been first photosynthetic organisms on earth• Fossil stromatolites from 3 billion years ago - Calcareous mounds: sediment + cyanobacteria

Fig. 6-10

Stromatolites

http://www.fossilmall.com/Science/About_Stromatolite.htm

I. Marine Microbes

B. Marine Bacteria1. Autotrophic

b. Chemosynthetic• Obtain energy from chemical compounds• Ex: Hydrogen, hydrogen sulfide, ammonium ion• Often anaerobic, may be symbiotic• Carry out primary production without sunlight

Fig. 6-11

I. Marine Microbes

B. Marine Bacteria2. Heterotrophic

• Most are decomposers (break down organic material)• Important in nutrient cycling (microbial loop)• May be symbiotic

Fig. 6-14

I. Marine Microbes

B. Marine Bacteria2. Heterotrophic

• Most are decomposers (break down organic material)• Important in nutrient cycling (microbial loop)• May be symbiotic

Fig. 6-14

I. Marine Microbes

C. Archaea• Resemble bacteria superficially but may be

more closely related to eukaryotes than bacteria• Includes extremophiles and mesophiles; may

comprise up to 40% of microbial biomass in open ocean

• Biochemically distinct from Eubacteria and Eukarya

• Structure of membranes, cell walls, etc.

• Bacteriorhodopsins to capture light• Pigments similar to eukaryotic rhodopsins

San Francisco Bay salt ponds

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I. Marine Microbes

D. Eukarya2. Stramenopiles (Heterokonts)

a. Diatoms• Unicellular; some may form chains, which then

may form mats • Important open-water primary producers,

especially in temperate and polar regions• Prefer well-mixed, nutrient-rich conditions (Why?)• Explosive population growth --> Bloom

- May deplete nutrients locally• Important food source for planktonic grazers• Sediments beneath areas where diatoms are

abundant may contain many tests- Diatomaceous oozes (>30% diatom tests)

• Life cycle includes sexual & asexual reproduction

Fig. 6-20

I. Marine Microbes

D. Eukarya2. Haptophytes

a. Coccolithophores• Very small (typically less than 20 μm)• Usually in warm water at relatively low light

intensities

- Most abundant at depths of ca. 100 m in clear,

tropical, oceanic water• Blooms may cover extensive areas

Ex – Bloom covering 1000 x 500 km of sea

surface in North Atlantic (area ~Great Britain)• Coccoliths may be important components of

sediments

I. Marine Microbes

D. Eukarya3. Alveolates

• Membranous sacs (alveoli) beneath cell membranes

a. Dinoflagellates

b. Ciliates

Fig. 6-25

I. Marine Microbes

D. Eukarya3. Alveolates

a. Dinoflagellates• Important open-water primary producers, especially in

tropical regions• More tolerant of low nutrients and low light than diatoms

- Advantage under post-diatom-bloom conditions- Often abundant in summer/autumn following spring and summer diatom blooms- Motility allows individuals to maintain position in water column under low-turbulence conditions

• Motility also allows individuals to spend daylight hours in surface waters and night hours in deeper waters (Why?)

• Most abundant phytoplankton in stratified, nutrient-poor tropical and subtropical waters

• Blooms can produce harmful algal blooms (HABs), aka red tides or brown tides

blogs.scotland.gov.uk

Ceratium furca

http://www.whoi.edu/redtide/

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Blue Surf - YouTube

I. Marine Microbes

D. Eukarya3. Alveolates

a. Dinoflagellates• Red tides typically visible @ densities >2-8 x 106 cells l-1

- Cell densities may exceed 108 cells l-1

• Nutrient depletion + viral effects (if any) bloom breakdown

- Bacteria decompose senescing cells O2 depletion

• Red tides may not be toxic; HABs are• Toxin (Saxitoxin) may be

1) Released into water

2) Transmitted directly to higher organisms, esp. suspension feeders (e.g. clams, mussels, scallops, oysters), which may be eaten by larger animals

• Consuming tainted fish or bivalves can Paralytic Shellfish Poisoning (PSP)

I. Marine Microbes

D. Eukarya3. Alveolates

b. Ciliates• Present in all parts of ocean • May be extremely abundant in some areas• Cilia may be used for both locomotion and feeding • Typically prey on small phytoplankton,

zooplankton, bacteria• Tintinnids

- Vase-shaped, proteinaceous external shells- Relatively small (20-640 μm); may be important because of wide distribution- May consume up to 60% of primary production in some coastal waters

I. Marine Microbes

D. Eukarya5. Amoeboid Protozoans

a. Foraminiferans• Test (shell) made of calcium carbonate (CaCO3) or

agglutinated sediment particles- Fossil tests used to age geological deposits

• May have multiple chambers- Tests increase in size as organism grows

• Feed by extending pseudopodia through pores in test- Trap bacteria and other small organisms/detritus- Some have bacterial symbionts

• Pelagic forms (calcareous)- Often have spines- Especially abundant in surface waters b/w 40oN and 40oS- Tests may form foraminiferan oozes, esp. in shallow waters beneath tropics

• Benthic forms (calcareous or agglutinated)- Calcareous tests can be important sources of beach sand

Homotrema rubrum www.bios.edu

www.travelimg.org

http://www.ucl.ac.uk/GeolSci/micropal/foram.html

Fig. 6-29

Globigerinoides ruber

III. Marine Microbes

D. Eukarya5. Amoeboid Protozoans

b. Radiolarians• Common in all oceanic regions, especially in cold

waters, including deep sea• Test made of silica (SiO2)

• Tests may form radiolarian oozes, esp. in deep water in temperate and polar regions

• Feed by extending branched pseudopodia (axopodia) through pores in test

• Trap bacteria, protists, detritus, other small organisms including diatoms (Why diatoms?)

• May form gelatinous colonies up to 1 m across

Fig. 6-30