L15 - Haptophytes and Diatoms Flashcards
(47 cards)
What is the phylum haptophyta?
Haptophytes (Primnesiophytes), kingdom Chromista. Diverse array, primarily marine phytoplankton. A few freshwater and terrestrial forms. Unicellular and colonial flagellates, non-motile single cells and colonies. 300 species in 80 genera but more being discovered. Highest diversity in tropics.
What is the phylum haptophyta pt2?
Haptonema most distinguishing feature. ‘Hapto = to fasten’. Threadlike structure extends from cell along with 2 flagella of equal length.
What is Haptophyte haptonema?
Haptonema bends and coils. Does not beat like a flagellum. Swims in a lop-sided fashion. Can catch prey like a fishing rod. Also helps avoid obstacles. P. parvum causes HABs and fish die offs. Pymnesium parvum with 2 flagella and haptonema thread.
What are Haptophyte scales?
Small, flat scales on outer surface of cell. Composed of organic or calcified organic material. Calcified scales = coccoliths. 2 types - one produced in golgi vesicles and transported to cells exterior. Other is generated outside cell. 12 or more haptophyte families have coccoliths - the coccolithophorids
What are the coccolithophorids?
E.g. Emiliania huxleyi. Coccoliths of CaCO3 cover cell in layers of discs. Highly reflective - water discoloured; visible from space. Can cover 1000’s of km2. Basis of continuous fossil record to their first appearance, 230ma. White cliffs of Dover
What are coccolithoviruses and E. huxleyi?
Large E. huxleyi blooms attacked and destroyed by viruses. Recycling inorganic CaCO3 and organic C. Coccoliths expelled and sink down into marine sediments. Downward carbon flux
What is Haptophyte photosynthesis?
Most are photosynthetic. Chlorophyll a and a variation of chlorophyll c. Some have acessory pigment fucoxanthin (in common with brown algae). Plastids are surrounded by chloroplast endoplasmic reticulum, continuous with nuclear envelope. Evidence that plastids acquired by secondary endosymbiosis.
What are haptophyte life histories?
Sexual reproductive cycle. Flagellated stages, alternation of heteromorphic gens. Chromosome levels and life histories of many forms as yet unknown.
What is the ecological significance of Haptophytes?
Significant components of food webs. Most autotrophic producers. Also, consumers, grazing on particles such as cyanobacteria or dissolved organic carbon (DOC). Transport organic C and 66% of the oceans’ CaCO3 to deep ocean. Important for global carbon cycling.
What is the ecological significance of Haptophytes - DMSP?
Algal osmolyte dimethylsulfoniopropionate (DMSP) is precursor of marine dimethylsulphide (DMS). DMS is a volatile sulpur compound that affects atmospheric chemistry and global climate. Its emission to the atmosphere contributes about half of the global biogenic sulphur flux. After UV degradation forms cloud condensation nuclei (CCN) - cloud formation.
What is the ecological significance of Haptophytes - Phaecystis?
Gelatinous, colonial stage of Phaeocystis sp. dominates phytoplankton of marginal ice zone in polar regions. Contributes 10% of atmospheric phytoplankton sulphur compounds. Polysaccharide mucilage - foam clogs fishing nets but adds organic carbon to the water.
What is the ecological significance of Haptophytes - Chrysochromulina and Prymnesium?
Two genera notorious for forming harmful algal blooms (HABs). Kill fish and other marine life. Blooms encouraged by eutrophication.
What are some important haptophytes?
Pavlovophyceae (Pavlova, Isochrysis) outstanding food for various bivalve larvae now widely cultured for use in the bivalve aquaculture industry. Isochrysis high amount of pigment fucozanthin, extracts have cosmetic and hair-growth properties.
What are the phylum Bacillariophyta (Diatoms)?
Kingdom Chromista. Heterokont = different flagella. Paired, differ in length & ornamentation. One tinsel, one whiplash. Unique heterokont flagella of diatoms, chrysophytes and brown algae suggest they are related.
What are the phylum Bacillariophyta (Diatoms) pt2?
Unicellular or colonial. Exceedingly important components of phytoplankton. 25% of primary production on earth. Greatest biomass and species diversity of phytoplankton in polar waters.
What are the phylum Bacillariophyta (Diatoms) pt3?
Estimated 9,000 species, maybe as many as 200,000. Thousands of extinct species. First appeared 250Ma, became abundant 100ma. Many fossils identical to extant species. Unusual persistence through geological time. Also called Stramenopiles.
What are the phylum Bacillariophyta (Diatoms) pt4?
Tremendous nos of individuals in small areas. E.g. 30 to 50 million individuals of the freshwater genus Achnanthes on 1cm2 of submerged rock in streams. Large no of species may occur together. E.g. 369 species identified in 2 small samples of mud from the ocean floor. Most planktonic, but some are benthic or grow on other algae or submerged plants.
What is unique about Diatoms walls?
They are silica walls of 2 halves, unique as cell wall (frustule) in two overlapping parts. Fits together like a laboratory petri dish. Frustule made of silica (glass-like). Minute, intricate depression, pores and pathways connect living protoplasm within to outside enviro. Species distinguished by frustule ornamentation.
What are the two major types of diatom symmetry?
Pennate - bilaterally symmetrical
Centric - radial symmetry
Centric have larger surface to volume ratio = float more easily. Thus more abundant than pennate diatoms in large lakes and marine habitats.
What are Diatom life histories?
Reproduction mainly asexual - occurs by cell division. Each daughter cell receives half of the frustule of the parental cell and constructs a new half. One of two new cells is smaller so size of diatoms in pop eventually declines. Critical size level induces sexual reproduction. Sexual reproduction of zygote regains max size. Mass sexual reproduction forms layers of silica in southern ocean sediments.
What are Diatom life histories - unfavourable conditions?
Unfavourable conditions e.g. low mineral nutrients. Form resting cells - heavy frustules sink readily to bottom. Germinate when conditions improve. Diatoms most abundant in Spring and Autumn. Upwelling in oceans or wind driven turnover of stratified lakes re-suspends Si. When Si low, other phytoplankton become dominant. Diatoms bloom under ice in cold season when herbivores are not feeding.
What are diatom plastids?
Contain chlorophyll a and c. Masked by golden-brown carotenoid pigment, fucoxanthin. Pennate 2 large plastids. Centric numerous discoid plastids. Reserve storage material = lipids and water soluble polysaccharide, chrysolaminarin. Stored in vacuoles. Similar to laminarin found in brown algae.
What are Diatom feeding mechanisms?
Most are autotrophs. Some are heterotrophs, absorb organic C. Heterotrophs usually pennate and live on sea bottom in shallow habitats. A few diatoms are obligate heterotrophs, lack chlorophyll, cannot produce own food. Other lack frustules and live symbiotically in large marine protozoa (Foraminiferans). These provide organic C to their hosts.
What are diatoms in marine and freshwater habitats?
Primary food source. Rich in carbs, fatty acids, sterols, and vitamins. Bivalve mariculture - oysters. Diatomaceous earth - abrasives, filtering and insulation. E.g. california oil fields, diatomaceous earth deposit 900m thick, wiuth 270,000 tons quarried annual;y for industrial use. Some diatoms produce a neurotoxin (domoic acid) causing amnesiac shellfish poisoning.
