L13 - Ecology of the Algae Dinoflagellates

Question 1

What is the ecology of algae?

Answer 1

Biosphere - 3 life zones. Open sea, shore and land. Open sea and shore more ancient. Here, algae play a role comparable to that played by terrestrial plants. Algae often dominate freshwater habitats e.g. ponds, streams and lakes. Important contributors to ecosystem productivity

Question 2

What are rocky shores home to?

Answer 2

Larger, complex seaweeds. Red, brown, and green macroalgae. At low tide, zonation reflects positions of species in relation to their ability to survive exposure.

Question 3

What is the intertidal zone?

Answer 3

Large, fluctuations of humidity, temperature, salinity and light, twice a day.

Question 4

What do seaweeds face in extreme environments?

Answer 4

Physical and biological challenges, their complex biochemistries, structures and life histories reflect adaptations to these challenges. Polar seaweeds endure months of darkness under sea ice. Seaweeds are also prey to a host of herbivores and microbial pathogens.

Question 5

What are kelp forests (brown algae)?

Answer 5

Offshore, beyond the wave zone, brown kelps form forests. Provide shelter for a diversity of fish and invertebrate animals. Large carnivores find food and refuge here. Including tuna and sea otters e.g. in california. Humans harvest these kelps for food and industrial products

Question 6

What are plankton (‘wanders’)?

Answer 6

Minute photosynthetic cells and tiny animals. Occur in all bodies of water as suspended plankton. Phytoplankton = photosynthetic microalgae plus cyanobacteria. Base of the food web for heterotrophic organisms in oceans and freshwater. Zooplankton = heterotrophic plankton. Mainly tiny crustaceans, the larvae of many different animal phyla, heterotrophic protists and bacteria

Question 7

How are plankton nourishment?

Answer 7

An important source of nourishment for heterotrophic organisms. Whales, mostly small and some large fish, feed on plankton (mostly zooplankton), small fish & crustaceans (e.g. krill, copepods). Marine: unicellular or colonial haptophytes, dinoflagellates and diatoms are the most important eukaryotic members. Freshwater: single-celled or colonial chrysophytes, diatoms, green algae and dinoflagellates. Not all microalgae are planktonic

Question 8

Humpback whale food cycle?

Answer 8

Whales eat iron-rich krill and other prey at depth, defecating, which yields nutrients for phytoplankton occurs only at the surface because of water pressure. These microscopic plants (phytoplankton) use photosynthesis energy and are krill’s main food.

Question 9

Phytoplankton populations?

Answer 9

In unpolluted waters, pop levels held in check by: seasonal climate changes, nutrient limitation, predation. Human disturbance (fertiliser run-off) releases algae from these constraints. Populations grow to undesirable ‘bloom’ proportions. Red tides or brown tides: large numbers of algal cells containing red or brown accessory pigments.

Question 10

What are Harmful algal blooms (HABs)?

Answer 10

Sometimes correlate with the release of large quantities of toxic compounds. These have evolved as anti-predatory defence against animals and protists. Can be toxic to wildlife and humans. Cause massive die-offs of fish, birds and aquatic mammals. Globally the frequency of harmful algal blooms (HABs) is increasing. May be associated with declining water quality on an over-populated planet.

Question 11

Productivity and carbon cycling pt1?

Answer 11

We live on a watery planet, algae are abundant. Transform CO2 into carbohydrates by photosynthesis. Transform CO2 into CaCO3 by calcification. Large amounts of organic C and CaCO3 transported to ocean bottom. Today marine phytoplankton absorb half of the CO2 resulting from human activities.

Question 12

Productivity and carbon cycling pt2?

Answer 12

Some phytoplankton decrease atmospheric CO2 by favouring formation of CaCO3 as they fix CO2 during photosynthesis. CaCO3 is deposited as tiny scales covering the phytoplankton. CO2 removed from water replaced by atmospheric CO2, creates a flux effect CO2 drawdown. Calcified phytoplankton sink to the sea floor = white cliffs of dover and north sea oil deposits. Red, green and brown algae can also become encrusted with CaCO3

Question 13

What is sulphur cycling?

Answer 13

Haptophytes and dinoflagellates, some produce significant amounts of a sulphur-containing organic compound. Aids in regulating osmotic pressure in cells. Volatile compound is excreted and converted into SOx in the atmosphere. These increase cloud cover and hence reflect sunlight away from the planet.

Question 14

What was the evolution of algae?

Answer 14

Eukaryotic algae evolved membrane bound organelles from ingestion of purple bacteria (mitochondria) and cyanobacteria (chloroplast)

Question 15

Algal classification?

Answer 15

There is a conundrum of classification. As they fit into bacteria, protozoa, chromista, plantae. Scientists still use the convenient term protist informally to refer to eukaryoties that are not plants, animals, or fungi.

Question 16

Algal classification? pt2

Answer 16

15 divisions (phyla) and 54 classes. Difficult to define a species. Estimated from 30,000 to >1 millions species. New classes are being found and taxonomy is subject to name changes. Algae can have high degree of phenotypic plasticity. Phenotype versus genotype for classification. Molecular techniques are starting to provide clues as to what constitutes a valid taxonomic grouping.

Question 17

Algae 15 phyla (divisions), 54 classes - Cyanophyta?

Answer 17

Cyanobacteria 5000 species.

Question 18

Algae 15 phyla (divisions), 54 classes - Rhodophyta?

Answer 18

Red algae 6000 species
Euglenophyta (eugleniods)
Cryptophyta (cryptomonads)

Question 19

Algae 15 phyla (divisions), 54 classes - Dinophyta?

Answer 19

Dinoflagellates 2000 species
Raphidophyta

Question 20

Algae 15 phyla (divisions), 54 classes - Haptophyta?

Answer 20

Primnesiophytes 300 species
Chrysophyta (golden/golden brown algae)
Xanthophyta (= Tribophyta; yellow-green algae

Question 21

Algae 15 phyla (divisions), 54 classes - Chlorophyta?

Answer 21

Green algae 7000 species
Eustigmatophyta

Question 22

Algae 15 phyla (divisions), 54 classes - Phaeophyta?

Answer 22

Fucophyta; brown algae 1500 species

Question 23

Algae 15 phyla (divisions), 54 classes - Heterokontophyta/Bacillariophyta?

Answer 23

Diatoms 9000 species
Prasinophyta
Glaucophyta

Question 24

What can classification on phenotype lead to?

Answer 24

Polyphyletic classification (bad) - they look the same but the are not (convergent evolution). Classification based on DNA barcoding is more accurate. Prasinophyta is a paraphyletic group, includes Ostreococcus

Question 25

What is cryoET?

Answer 25

Cryogenic electron tomography, Ostreococcus tauri, works well on small cells

Question 26

Evolution of algae?

Answer 26

Cyanobacteria, (primary endosymbiosis) -> Chlorophyta -> Heterotrophic eukaryote, dinoflagellates, (secondary endosymbiosis) -> Euglenoids, chlorachniophytes. Glaucophyta. rhodophyta + chlorophyta -> Heterotrophic eukaryote, (secondary endosymbiosis), cryptophytes, haptophytes, heterokontophytes, dinoflagellates. Cryptophytes, haptophytes, heterokontophytes -> tertiary endosymbiosis -> dinoflagellates

Question 27

What is the phylum Dinophyta?

Answer 27

Dinoflagellates (dino = whirl, flagellum = whip), most are unicellular biflagellates (2 dissimilar flagella). Flagella beat within 2 perpendicular grooves. Spins like a top as it moves. 2000 species, marine (1700 species) and freshwater (200 species). Live in phytoplankton/benthic environments/sea ice

Question 28

What are dinoflagellate chloroplasts?

Answer 28

Pigmented forms contain chlorophyll a and c. Masked by carotenoid pigments, including peridinin. Peridinin is similar to fucoxanthin. Dinoflagellate chloroplasts derived from ingested chrysophytes by endosymbiosis. Others have green or blue-green plastids from ingested green algae or cryptomonads. Carbohydrate food reserve = starch stored in cytoplasm

Question 29

What is an example of Phylum Dinophyta: Dinoflagellates - Peridinium?

Answer 29

Peridinium spp. - freshwater and marine. Carotenoid peredinin masks colour of chl a and chl c

Question 30

What is kleptoplasty in dinoflagellates?

Answer 30

Is the process where heterotrophic dinoflagellates, after consuming algae, temporarily retain and utilise the algal chloroplasts (kleptoplasts) for photosynthesis, potentially representing and early stage in the evolution of permanent endosymbiosis. It relates not to digesting them

Question 31

What is an example of Phylum Dinophyta: Dinoflagellates - Gonyaluax polyredra?

Answer 31

2 flagella in grooves, responsible for red tide harmful algal blooms (HABs) along the coast in california

Question 32

What happens in dinoflagellate reproduction?

Answer 32

Unusual in having permanently condensed chromosomes, initially thought a primitive group. Now though to be highly derived. Reproduction is by longitudinal cell division. Each daughter cell receives one flagella and a portion of the wall (or theca). Then reconstructs the missing parts in an intricate sequence

Question 33

What is dinoflagellate structure?

Answer 33

Many bizarre in appearance. Stiff cellulose plates of the wall form the theca, in open ocean dinoflagellates have sail-like theca plates which aid in floatation (cellulose). Others have thin or no cellulose plates - do not appear to have a theca.

Question 34

What are dinoflagellates feeding strategies?

Answer 34

About half lack photosynthetic apparatus. Ingest solid food particles or absorb dissolved organic compounds. Even pigmented (photosynthetic) and armoured forms feed in this way (mixotrophy). Some exude a tubular process (peduncle) to suck organic materials into cell. Other use a cytoplasmic veil (pallium) to envelope prey.

Question 35

What are pigmented dinoflagellates as symbionts?

Answer 35

Occur as symbionts in many kinds of organisms. Sponges, jellyfish, sea anemones, tunicates, corals, octopus, squid, snails, flatworms and certain protists. Then mantle of some giant clams appears chocolate brown due to presence of symbiotic dinoflagellates. When symbiotic, lack armoured plates and appear as golden spherical cells - zooxanthellae

Question 36

What is dinoflagellate zooxanthellae: coral?

Answer 36

Responsible for photosynthetic productivity that allows corals to grown in nutrient poor tropical waters. Coral tissues (polyps) contain up to 30,000 symbiotic dinoflagellates per cubic mm.

Question 37

What is dinoflagellate zooxanthellae: coral? pt2

Answer 37

Amino acids produced by polyps stimulate dinoflagellates to produce glycerol (not starch). Glycerol used directly in coral respiration. Dinoflagellates need light, so corals do not grow below a depth of 60m. Coral shapes due to light gathering properties of geometric arrangements (tree branches).

Question 38

What are dinoflagellate resting cysts?

Answer 38

Produced under favourable conditions such as low nutrients. Non-motile, resting cysts drift to lake or ocean bottom and remain viable for years. Ocean currents transport benthic cysts to other locations.

Question 39

What are dinoflagellate resting cysts? pt2

Answer 39

When conditions become favourable will germinate reviving population of swimming cells. Explain many aspects of dinoflagellate blooms: why blooms are associated with nutrient run off. And move from one location to another from year to year

Question 40

What is the dinoflagellate life cycle?

Answer 40

Sexual reproduction intitiated under deteriorating conditions. Resting stage (cyst) excysts when conditions improve.

Question 41

What is dinoflagellate: sexual reproduction?

Answer 41

Found in a number of species. Zygotes form distinctive, chemically inert, ornamental cell walls. Resemble ancient fossil acritachs. Laboratory cultures reveal that morphologically different individuals belong to same species. Important to undertsand life histories in order to understand role of phytoplankton (including dinoflagellates) in food webs and bloom formation

Question 42

What are dinoflagellate toxic compounds?

Answer 42

20% of species produce >1 highly toxic compounds. Economically and ecologically significant. May provide protection from predation. Pfiesteria piscicida uses its deadly compound (a glycoside) in a 'hit and run' feeding strategy. Presence of fish stimuates benthic cysts to germinate into swimming Pfiesteria cells. These produce a toxic substance that paralyses the fish respiratory system = suffocate.

Question 43

What is Pfiesteria piscicida?

Answer 43

Scanning electron micrographs (SEM) of two common stages. Fish subject to Pfiesteria's 'hit and run' feeding strategy. As fish decay, dinoflagellates extend peduncles and feed on fish flesh. Then return to benthic cyst stage (2 hours)

Question 44

What is Dinophysis acuta?

Answer 44

Armoured, marine, planktonic dinoflagellate. Mixotrophic. Commonly found in cold and temperate neritic waters (shallow). Red tides (HABs). Toxic species associated with DSP (diarrhetic shellfish poisoning from okadaic acids).

Question 45

What other toxins are there?

Answer 45

Brevetoxins (Karenia brevis), toxic to fish, marine mammals, birds, humans (not shellfish). Toxic aersols (asthma) and neurotoxins. Saxitoxin - paralytic shellfish poisoning. 2000 annual cases, 15% mortality

Question 46

What is dinoflagellate Bioluminescence?

Answer 46

Attractive sparkling of waters observed at night as boats or swimmers agitate water. When disturbed, a series of biochemical events results in a chemical reaction. Luciferin and enzyme luciferase plus O2. As in fireflies creates a brief flash of light. Serves as an anti-predatory mechanism against species e.g. copepods (crustacean zooplankton). Two hypotheses: light flashes startle predators. Or copepods become visible to their fish predators.

Question 47

Example of dinoflagellate bioluminescence?

Answer 47

Noctiluca scintillans, predatory, non-toxic, bioluminescent