Aquatic Ecology 2
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Measuring Algal Biomass:
4 techniques -
1) Filter water sample, put filter on nutrient agar - count colonies (only 10% grow)
2) Direct cell counts - Acradine Orange or hemocytometer
3) Chlorophyll measurements - spectrophotometer
4) Chlorophyll measurements - fluorometric - Measuring Bacterial Growth
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measure uptake of 3H (thymidine)
only gorwing cells incorporate, measure incorporation per unti time by scintillation counter -
Measuring Primary Production
2 techniques -
1) O2 consumption - meausre changes in dissolved O2 in light-dark bottles
2)14C method - provide 14C in bicarb, incubate, filter, count radioactivity on filter - Factors affecting photsynthesis
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1) Light
2) Nutrients -ammonium, nitrate, nitrite, phosphate, silicate, Iron - Light
- Varies w/: depth, season, affected by latitude, water transparency, compensation depth
- Nutrients & Photosynthesis
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Vary with: depth, season/ stratification of water column, affected by rates of "new nutrients" and regeneration of nutrients
*Requires transport molecules* - Iron - why critical for life?
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- Transport of e-
- Uptake of Nitrate
Enzymes:
- Ferredoxin
- Nitrate reductase
- Chlorophyll Synthetase
- Nitrogenase - Ironex Experiments - Ironex I
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1993 - area S of Galapogos ISlands, HNLC area
- added 2 - 200 pptril Fe to surface, followed patch w/ Drogue
- primary production increased 4 fold, stopped after 4 days
- why: iron became insoluble and sank - Ironex experiments - Ironex II
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- 3 Fe applications, 3 days apart, used more soluable Fe form
- w/in 1 week phytoplankton biomass increased 30 fold
- 2500 tons of CO2 taken up before patch dispersal
- Diatoms benefited most from Fe fert. - Implications of Ironex
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- Possible solution for atmospheric CO2 levels and Global warming
Remaining Q's:
- does Fe enrichment lead to transport of carbon to deep ocean?
- should we even consider fertilization of HNLC areas? - 3 lake regions
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Epilimnion - surface mixed layer
Metalimnion - thermocline region
Hypolimnion - lower lake region - Annual Circulation Patterns in Lakes - 3 major
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1) Amixis - no circulation
2) Holomixis - when mixing occurs, entire water column mixes
3) Meromixis - mixing does not include entire water column - Amixis lakes
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- no circulation - due to permanent ice cover
- found at very high latitudes / elevations - Holomixis Lakes - 4 kinds
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1) Oligomictic - irregular, short duration mixing
- usually low altitude, equatorial or very deep temperate lake
- mixing occurs when warm surface water is colled by cold evening or rain & wind
2) Monomictic - one regular mixing/ yr
- Warm: subtropical (and some deep temperate) lakes that stratify in summer but mix for much of the winter
- Cold: freeze over in winter; become isothermous and mix during the summer months
3) Dimictic - becomes isotherms - mix in spring & fall (typical temperate lake)
4) Polymictic - many overturns/ continuous mixing (often shallow/ unprotected lakes in subtropic & temperate regions) - Meromixis Lakes
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- dense bottom water remains stagnant & usually anaerobic
- water column divided into mixolimnion & monimolimnion separated by chemocline - Lakes classified by trophic status - 3 main
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1) Oligotrophic
2) Mesotrophic
3) Eutrophic - Oligotrophic Lakes
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- little or few nutrients (<300ug/L N, <10ug/L P)
- U-shaped, very deep; large,
- cold hypolimnion
- Chl a < 2 ug/L; Secchi > 5m - Mesotrophic Lakes
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- moderate nutrients(300-600 ug/L N, 10-30 ug/L P)
- V-shaped, moderately deep
- moderate - small hypolimnion
- Chl a 2-5 ug/L; Secchi 2-5 m - Eutrophic Lakes
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- high nutrients(> 600 ug/L N, > 30 ug/L P)
- V-shaped, shallow
- small to no hypolimnion
- Chl a > 5 ug/L; Secchi < 5 m - Eutrophication
- NATURAL process of organic enrichment of a body of water resulting from increased nutrient loading & subsequent increase in primary production
- Characteristics of a Lake undergoing Eutrophication
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- increased N & P conc.
- increased turbidity
- decreased Secchi depth
- decreased depth as lake fills
- loss of D O2 in hypolimnion during stratification
- decreased species diversity in most habitats
- eventual filling of lake to form semi-aquatic, finally terrestrial habitat - Cultural/ Artificial Eutrophication
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-Process greatly accelerated by human activities:
- clearing land (inc runoff & nutrient input)
- agriculture (manure & fert application)
- release of untreated/ partially treated sewage into lake
- release of organic wastes (milk processing wastes) - Times scale of Eutrophication
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Natural: 1,000's to 10,000's yrs
Artificial: yrs to decades - Microzooplankton - overview
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- smallest & most abundant organisms
- many consume by phagocytosis
- some osmotrophic
- usually consume bacteria (50% of all produced)
- marine & freshwater - Radiolarians
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- only marine
- amoeba w/ glass/silica skelton & spines
- eat bacteria & phytoplank.
- up to 2mm in diameter
- very fragile - killed by nets - Foraminifera
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- only marine
- CaCO3 skeleton w/ spines
- consume bacteria & phyto
- some have symbiotic algae
- found in tropical oceans - Rotifers
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- almost entirely freshwater
- multicellular
- 2 cilliated disks on anterior end: beat for feeding & motility
- eat bacteria & phyto - Ciliates
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- feed on bact, phyto, some mixotrophic
- elongate, ranging from size from about 50 um to over 1 mm in length
- covered with rows of cilia
- Some "Tintinnids" - have "lorica" (shell)
- some "Aloricate" - soft bodied - Nauplius
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- larval crustaceans
- mostly immature copepods
- omnivorous - Bacteria & Biomass
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- bacteria usually make up 1/2 or more of the bacterio- /phytoplankton biomass
- bacterial production is about 20% of primary production
- if bacterial growth efficiency is ~ 50%, bacteria consume about 40% of primary production.
- bacterial populations are stable; therefore bacteria are being grazed at he same rate as they grow - Bacteria & food chain
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- traditional oceanic food chain disproven
- replaced by microbial loop
- tiny cells eating other tiny cells
- mesoplankton not built for filtering particles from water
- major bacteria consumers must be microplankton - Microbial Loop Overview
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DOM -> Heterotrophic Bacteria->
Zooplankton <- Phytoplankton
Zooplankton --> Fish & Higher - Nekton - Class Crustacea
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Ex: Antarctic Krill
- important commercially - Nekton - Class Cephalopoda
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Ex: squid, octapus, cuttlefish
- very fast, move by expelling water from siphon - Nekton - Reptiles
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Ex: Crocodiles (alligator is fresh)
- sea turtles
- sea snakes (Indian & Pacific Oceans)
- evolved from land snakes
- young born live
- very poisonous, not
aggressive - Nekton - Order Cetacea
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Ex: whales, dolphins, propoises
- Mysticeti: Baleen whales - 2 blowholes
- Odonticeti: Toothed whales - 1 blowhole
- make sounds from nasal area
- sounds focused by melon & sent out
- returning sounds received - allows whale to echolocate - Nekton - Order Pinnipedia
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Ex: Seals, sea lions, walruses
- 4 fins
- All but 1 species marine
- eat primarily fish & squid
- exploited commerically for oil, fur, etc. - Nekton - Order Sirenia
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Ex: manatees & dugongs
- exploited for meat, oil, & hide
- Steller's Sea Cow
- First described 1741;
Extinct 1768 - Nekton - Fish: Class Agnatha
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Jawless Fishes: Lapreys & hagfish
- circular mouth always open
- rows of conical teeth
- cone shaped tongue
- often parasitic, some predatory (size dependant) - Lampreys vs hagfish
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Lampreys:
- series of holes/ gil slits on body
- single median nostril
- certilagenous skeleton
- certilage "cup" for brain case
- Breed in freshwater: Ammocetes larva
- burrow into sediments &
filter feed
Hagfish
- deepwater scavangers - Nekton - Fish: Class Chondrichthyes
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Ex: Sharks, skates, rays
- cartilagenous skeleton
- descended from bony fish
- complete brain case
- heterocercal tail (spine continues into upper fin of tail)
- 5 to 7 gil slits
- Sexes very evident (both have cloaca)
- males have extension of pectoral fins (claspers) - Nekton - Fish: Class Osteichthyes
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Bony Fishes
- bony skeleton
- one gill slit
- paired moveable fins
- non-homocercal tail
- 20,000 species
- commercially important - Bony fish feeding habits
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- Piscivorous: prey on other fish
- Plankivorous: prey on plankton
- few scavangers
- few herbivorous - Perciform body type
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- ctenoid scales
- 1 or 2 dorsal fins
- 1 or 0 ventral fins
- 2 paired fin sets (pecs and pelvics)
- pectoral fins almost even w/ pelvic
- spiny rayed fins
- found in slow flowing water
- pectoral - Salmonid body type
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- cycloid scales
- pelvic & pectorals distant
- trout & salmon
- found in fast flowing water - Oceanic Depth Zones 3
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1) Epipelagic Zone: <200m
2) Mesopelagic Zone: 200-1000m
3) Bathplelagic zone: >1000m - Epipelagic Zone
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- <300 species
- where most common fish from
- tuna, mackrel, bill fish, snapper, eels, bass
- Large, active predators
- associated w/ areas of high primary production - Mesopelagic Zone
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- Lantern fish, cyclothones, lanset fish
- small aprx. 15 cm
- plankton feeders
- diurnal migration
- have bioluminescent spots on bottom on body for camoflaugue - More on Bioluminescent spots and Camoflague
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- allows for camo from preds below
- breaks up outline of body against lighter water
- dots are aggregates of bacteria (vibrio-fisherii)
- colony grows when sufficient size & adaquate energy
-fish have "blinds" to open/close spots
- some put "filters" on spot to adjust wavelengths of light emitted - Bathopelagic Zone
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- fish have very large mouths to engulf large peices of food if found
- Gulper-eel, angler-fish, Rattail, Halosaur, cyclothones
- diversity great, density low - Planktivores
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Ex: Menhaden
- use gill rakers to entrap plankton
- all fish have gil rakers - used for protection on other species
- can filter 6-7 gals water/ min
- large commercial fish, most important in bay
-fished using purser seine
- used in fish & poultry food, dietary supplements, cosmetics industry - Shark Prey Detection
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Lateral Line:
- sensitive to water movement
- movement send vibration, forces water into lateral line
- sense of smell also very good
Ampullae of Lorenzini:
- on snout, detects electrical field
- Have taste buds on body surface - Temp Regulation types
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Poikilotherms: body temp dictated by environment
Homeotherms: body temp independant of environment
-Ex: Tuna
- Has Rete Mirablile - Rete Mirabile
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- keeps inner body blood warm by counter current exchange
- outgoing blood continuously cooled by incoming cold blood
- Incoming blood warmed by already warm outgoing blood
- Can keep core body temp 20 degs. above water temp - Bouyancy
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Sharks: lipids - stored in liver as oil
Fish: swim bladders - 2 kinds:
Physoclist: bladder independant, gas gland secretes gases from blood to fill bladder
Physostome: connected to esophagus, fish can gulp air to fill bladder in addition to gland - Catadromous migration
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Ex: American Eeel
- live in freshwater as adults, spawn & spend juvenile stages in marine habitats - Anadromous migration
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Ex: Atlantic Salmon
- live in marine habitat as adults, travel to freshwater to spawn & spend juvenile stages - Oceanadromous migration
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Fish migrate from one portion of ocean to another
- young need food source in different location