freshwater streams pt 1 Flashcards
Freshwater biomes
○ Lakes (lentic)
○ Rivers (lotic)
○ Freshwater biomes can vary with climate and topography both of which impact nutrient input and oxygen availability
○ Freshwater biomes includes lakes and ponds, and rivers and streams
○ Turbulent flow of water ensures rivers are well oxygenated
○ Some lakes are stratified meaning that the density of the bottom waters them form mixing upward with shallow waters
○ Organic remains that sink to deep waters provide food for resipring bacteria which draws down oxygen levels
○ Seasonal cooling of surface waters can elimate temp differences from top to bottom causing the stratified water masses to mix and bring oxygen to deep waters and nutreints to the surfcae
In the frwshwater system we don’t use primary rpducers to classify them - we describe bioms looking at where the river feeds into etc
Rivers and streams
○ Rivers and streams are freshwater biomes characterized by moving water
○ Rivers and streams, like lakes, avry tremendosuly in size and chemistry
○ River basin is area of the continente drained by a network of rivers to a large river
○ Area of land that is drained to a stream, lakes of wetlends are watersheds
○ Water chemistry varies with types of terrain
○ Runoff is the primary input of nutrients and inroganics to a river - nutreints can be low or very high
○ Rain or groundwater inputs aslo contributes freshater to the rivers
○ Rivers/streams are characterized by mving water - they like lakes vary tremdosuly in size and chem
Bc of currents, rivers are generally well oxygenated although oxygen levels may be lower in slowly moving rivers on floodplains
Makeup of a river
○ How do conditions in a river differ?
○ Light: clarity can differ greatly depending on productivty or inorganic/organic inputs from surrounding terrestrial envrivnment
○ Flow of water mixes the sediment into the water column, further impacting turbidty
○ Bc rivers do not run in a straight line, microhabitats form:
§ Pools
§ Runs
§ Riffles
§ Rapids
§ Water column
§ Benthos
○ Riparian zone where transition occurs between river and terrestrial habitat surrounnding
○ Ripple zones are where there is fast water over rocks
○ Areas of bends in the river cause slow flow of water and a deeper area there - it can be less o2 there while more o2 in the ripple zone
○ Nutrient levels differ:
§ N and P - natrual sources: weathering of deposits or erosion
§ Oxygen - natrual sources: mixing, submerged plans or algae, high solubility in cool water
○ Human impacts or clmate change can signifcantly affect rivers:
§ N and P - other sources: runoff from cities, wastewater treatment plant effluent, fertlizers and agriculture runoff
§ Oxygen - limbited by: warm water, overly productive conditions, stratfictaion
○ The addition of the nutreints is helpful but as producers grow so much, they die and tehn the decompsoitin of the dead plants leeches oxygen out of the water - dissolved o2 in water becomes low - as water also gets wamred, less oxygen can dissolve so more problems arise in the water
○ This isnt much of a problem in rivers bc the water flows, but it is a problem in lakes especially ones that are fueled by river and agriculture runoff
○ Rivers receiving organic wastes from cities and industry can lead to oxygen stress
○ Such wastes have high biochemical oxygen demand or BOD
§ A measure of organic pollution defined as the amount of dissolved oxygen required by microbes, mainly bacteria and fungi to decompose the organic matter in a water sample
Whos who in the stream
○ In streams, producers include:
§ Plants and eukaryotic alage (both large and small) grow along river margins
§ Phytoplankton (small photosynteghtci microbes) photosyntheize throughout the water column
○ Insects are imprtant consumers, but other vertebrates (crustancea,s gastroprods, and bivalves), fish, turtnles and birds can all be abudnant and diverse
○ Many consumers are filter feeders
Some of the many types of microspic phytoplankton in the freshwater include: cyanobacteria, green algae and diatoms
domans of life
○ Life on earth falls into three groups or domains
○ Bacteria nad archaea or prokayrotes
The thrid domain includes cells with nuceli, eukaryota
Cyanobacterai - freshwater producer
○ Photosntehis is widepsprad in bacteria; all but one are anoxygenic
○ Cyanobacteria are oxygenic phototrophs
○ Often refefred to as blue-green algae
○ Chlrophyll a is the main photosyntehic pigemnt that absorbs light enegry to ultimatly form charged protons and e- (chemcial energy)
○ Accesory pigments expand the range of light wavelengths that can be absorbed: carotenoids (orange), phycocyanin, allophycocyanin (blue green), phyocoerythryn (red)
○ Photosyntehsi occurs on the thylakoid membranes
○ Thylakoids are surrounded by a membrane, where clhorphyll is found
○ Arranged as parallel sheets
○ Accesory pigemnts present along the surface of the memrbane
○ Like other bacteria tho, blue-green algae doesn’t have any organelles
○ Cyanobacteria can vary in size a lot
Single celled filaments to filaments of multiple cells - we focus on anobaena - sytings of undiferentiated cells at either end of the filanment flanking two elongated resting cells, and in the middle a hetereocyst specilized cell for nitrogen fixing
Freshwater filamentous algae - anabaena (cyanobacteria)
○ Some species form filaments of multiple indivdual cells
○ Filamentous mrophology - forming wool-like mats in freshwater
○ Indivdual cells may specilzie to perfom diff functions
○ Unspecilzied cells are for photosynthsis
○ Akinete:
§ Resting stage
§ Thick-waled
§ Filled with food resources - many carbs are stuffed into here
○ Heterocycst:
§ Anaerobic cell
§ Make useable N; the enzyme (nitrogenase) cannnot function in presence of o2
§ Shares resources (carbs) with neighboruing (vegetative) cells (the akinetes)
§ Lack chlrosphyll to prevent formation of inetrnal oxygen
Anerobic nitregn fixers
toxic cyanbocatrria
○ These toxins can kill fish
Alagal blooms in freshwater are suually cyanobacterai - not always creating toxins but when they do it’s a prob
Eukaryotic algae (green and diatomes)
○ Opisthakonta was animal
○ Photosyntehic alagae are in the archaeplastida - green algae and plants specifically
Diatomes are in the SAR
Archaeplastida
○ Land and aquatic plants and green alage are all pretty clsoely related
○ Green alage and land plats in the virdiplnatae
○ Not monophyletic group if u disclude land plants
○ Within the supergroup is the viridiplantae (green plants)
○ This clade includes all land plants, along with the green algae
○ These organisms have cellulose within their cell walls, chrlophyll a and b and lack phycobilins (stacks of pigemnts or chlorophyll in an area)
Green algae are not a monophyletic groups, icnldung a number of taxa and eclduing the land plants
Green algae
○ (in the archaeplastida)
○ Green alage general characetrics:
§ Eukaryotic
§ Chlorphyll a and b; carotenodis (diff than cyanobacteria)
§ Primary chlrosplast - 2 memrbanes
§ Starch and storage molecule
§ 2 or 4 apical whiplash type flagella that are smooth
§ Cellulose and pectin in cell wall;simetimes calcified
§ Mostly freshater
§ 7000 species
§ Can be unicellular or colonial
§ Unciellular example is chlamydomonas
§ Ex. Of clonial is volvox - flagelate. Colonial genera isogamy to oogamy (sperma nd eggs)
○ Life of chlamydomonas:
§ unicellular
§ Asexual and sexual cycles
§ Vegetative cells haploid
§ Forms haploid gametes; two mating types (mt+ and mt-)
□ Have to find eachotehr to fuse
§ Isogamy = gametes look idnetical no spemr or egg
§ Zygote is not flagelated
□ Overwintering dormant stage in the benthos
□ In the spring, meiosis releasing four flagelated haploid cells
○ Life of volvox:
§ Colonial
§ Cells on outside of colony undergo multiple mitotic divisions
§ Form invagination, first with flagella on the inside - need to flip
§ Eventually they break out of mother colony - genetically dientical
□ They eventually get so big that they rupture relasing the new colonies
§ Sexual reprodution alos happens, often following envrinmental stress
§ Oogamy = egg and sperm as gametes
§ Egg NOT formed by meisos; vegetative outer cells haploid
§ Sperm with two flagella by mitosis; swim over to fertlize the egg
§ SPERM AND EGGS FORMED FROM VEGETATIVE HAPLOID CELLS
§ Diploid zygote is thickwalled and durable; resting stage; overwinters on lake bottom
§ In spring zygote moves up, undergoes meisosi and form meisospores; mitosis; new colonies may form
§ Unlike us - meisosi in the zygotes
○ Chlorpcoccales: non-flagellate uniells and colonial genera
○ Morpholgical trends in green algae:
§ Unicellular
§ Colonies
§ Filamnts
§ Multicellular
§ Filamentous algae form long strands, filanents
§ Filamentous chlrophycease are uninucleate (ex. Ultotrhix)
Sar - diatomes
○ Stramenopile algae:
§ A synapomorphy is the morphology of their biflagelate motile cells (zoospore/es and gametes):
§ One whiplash-type flagellum (the end is slightly modified)
§ One tinsel type flaggelum with lateral appendeges
§ Ofte are yellow bc of the corotenoids
§ The tisnel type if basically hairy
§ (green alage only had two whiplash)
○ Diatoms: bacillariphyta
○ Diatoms are the most diverse stramenophiles
○ Recognized by tehri distinctive skeletons of silica, diatoms are responsible for 25% of all photosyntehsis on earth
○ Known diatom species thrive in envirnments that range from wet soil to the open ocean
○ More found in lakes than rovers
○ Since in the bottom and live in benthos epsically in winter when tehres no sun for them to photosynetize
○ Chlroplast source: secondary capture
○ Chlorphylls a, c; carotenoids
○ Chrysolaminarin storage prodcut
○ Flagella in sperm only, 2 then 1 tinsle type
○ Silica and pectin in cell wall
Marine and freshwater; benthic or pelagic
Morphology of Diatoms
§ Diatoms live in glass boxes called frustules made of nearly pure silica (glass)
§ Each frustrule consist of two valves or thecae
§ Surfaces of the thecae are finely sculptured
§ There is a bigg glass on top of a small one and the cell is found insdie
§ There are holes for material to pass in and waste out
§ They can move along surfaces
§ Corotenoids give them the straw like colour
Diatoms: Thecae Sculpturing
§ Two thecae make up the frustrules (glass box)
§ Surfaces sculturing is finely detailed
§ The patterns are visinle under the light microscope
§ The finest details are revealed only with the SEM
§ The number of holes will tell u the species
§ You can arrange diatoms into many patterns like diatoms and butterfly scales
Diatom Reproduction
§ Diatoms mostly reproduce asexually
§ Hypotheic becomes new epitheca (bottom lid becomes top lid)
§ Size will start to decrease bc the bottom valvae is smaller and that becomes a top valve so the new one it grows is gonna be smaller - after many generations there becomes a huge size difference
§ After they get so small, they cant reproduce asexually so they reset and form a new house by sexual reproduction
The diploid cell goes through meisosi for a haploid cell that loeses the house - they pump out gametes which will have the two flagella (they lose it quickly) and then fusion happens and zygote is formed to a vegetative cell
