446 Aquatic Ecology Flashcards
why study aquatic ecology
aquatic ecosystems & resources critical to human survival, health, well being
ecosystem processes
hydrologic flux, storage biological productivity biogeochemical cycling, storage decomposition maintenance of biological diversity
ecosystem “goods”
food construction materials medicinal plants wild genes for domestic plants and animals tourism and recreation
ecosystem “services”
maintain atmospheric gaseous composition regulate cimate cleanse water/air pollinate crops generate/maintain soils store/cycle nutrients absorbe/detoxify pollutants maintain hydro. cycles provide beauty, inspiration, research
human disturbances affecting coastal ecosystems
- Fishing, Pollution, Mechanical habitat destruction, introductions, climate change
(fishing always preceded other disturbances, others change in order)
inputs and concerns
organic (livestock), fertilizer, rain, pollutants, pathogens, pharma-care, invasive species, nitrate leaching
adverse effects of eutrophication
increased biomass of plankton shifts in phytoplankton (may be to toxic) increased epiphytes coral reef loss decreased water transparency oxygen depletion increased fish kills loss of desirable fish species reduction in fish/shellfish harvest decreased aesthetic value
chemical characteristics of aquatic ecosystems
nutrients
biological characteristics of aquatic ecosystems
foodweb
limnology
the study of inland waters - lakes (both freshwater and saline), reservoirs, rivers, streams, wetlands, and groundwater - as ecological systems interacting with their drainage basins and the atmosphere.
algal biomass vs nutrient
chl vs. Total phosphorus (TP)
increasing on log scale but large variation above/below the line
why measure TP as nutrient load?
most limiting resource
high nutrient, lower than expected Chl (algae)
more large fish, preying on large grazers
small algae
larger, efficient grazers
larger biomass
larger planktivorous fish
system is more efficient
system with lots of small planktivorous fish
prey upon small grazers
larger algae
high density of small fish
low density of large zooplankton
higher Chl (algae)
greener water, lower O2
small grazer, shallow lake, Chl vs. TP
high productivity, but less than small grazer system in med-large lake- less O2, less insolation, less space…
empirical data
observational
experimental data
manipulate variable
response of lake ecosystem to nutrient loading experiment
same [nutrient], #large fish vary
w/o large fish = small zooplankton = more algae
epilimnion
the upper layer of water in a stratified lake, ~constant T, mixed layer
lakes with high grazing, low TP
clear water, more light penetration, more heat deeper, larger metalimnion, less steep T gradient, deeper O2 max, photosynthesis can occur throughout metalimnion
metalimnion
thermocline, T changes more rapidly with depth than it does in the layers above or below, highest density, layer of ‘stuck’ algae
indicator of water transparency
secchi depth
lake with low grazing, high TP
high Chl = low transparency = low O2, higher and smaller metalimnion, less light penetration, steeper T slope in metalimnion, light just barely penetrates meta., photosynthesis cannot occur throughout metalimnion, O2 goes to 0, system is reducing (like saanich inlet)
zooplankton size under high fish density
~80% less than 0.2mm
zooplankton size under low fish density
~40% less than 0.2mm
hypolimnion
the lower layer of water in a stratified lake, typically cooler than the water above and relatively stagnant, ~constant T, O2
algae biomass with time
low grazing= increased biomass w/ t
intense grazing = very low slope, barely increasing
TP with time
low grazing = increased TP w/ t
intense grazing = very low slope, barely increasing
low grazing = more algae = more TP
dissolved P with time
low grazing = very low slope, barely increasing
intense grazing = high slope, increasing
why is there higher dissolved P with intense grazing
high grazing = lots of dissolved P b/c not being taken up by algae
size of fish controls [algae] which controls [dissolved vs. particulate P]
length of algae as a function of biomass of algae in large grazer system
as biomass increases, size increases (more removed = more nutrients available to the fewer)
length of algae as a function of biomass in small grazer system
increased biomass = smaller size (more biomass means higher quantity means less nutrients available to each)
algae size and phosphate turnover time
small algae (large grazer system) = slower nutrient turnover = long phosphate turnover time large algae (small grazer system) = faster Phosphate turnover time
when you have large particles, the overall particle load
is made up of more large particles, median is higher
large particles = less small particles
add nutrients
overall particle size shift to larger particles
= long phosphate turnover time
add nutrients and fish
shift to more smaller particles
= shorter phosphate turnover time
so… as average size of plankton declines..
larger slope, uptake efficiency increases, turnover time is shorter
AND transparency declines
how changes in biology = changes in physics
thermal structure, penetration of light, accumulated energy/heat content
fetch
longest open length of a water body through which wind can blow
change in epilimnion with fetch
increased fetch = increased depth of epilimnion (more wind = more wind mixing)
downward heating intensity vs. penetration of solar radiation
increasing surface area of water body (fetch) vs. increasing water transparency
increasing fetch & transparency
deeper epilimnion, more heat, more energy, greater depth for photosynthesis, more O2
role of biology on mixing rate
affects clarity of lake which affects insolation absorption which affects stratification
sedimentation, total phosphorus rates highest in
+N (nutrients added, no small fish, large zooplankton)
secchi depth highest in
control then +N
deepest when no small fish
chlorophyll highest in
+NF (nutrients, small fish, small zooplankton grazers, larger algae)
summer O2 profile, control vs. +F
+F higher O2 in epilimnion
lower O2 in metalimnion and hypolimnion
O2 max is higher in water column in +F and goes to 0 with depth
summer O2 profile, +N, +NF
+N higher O2 at all depths
+NF goes to 0 in hypolimnion
lake St. George
large # planktivorous fish low secchi depth smaller daphnia shallower epilimnion depth higher TP higher Chl strongly eutrophic
Haynes lake
less planktivorous fish deeper secchi depth deep epilimnion depth larger daphnia length lower TP lower Chl
Julian days
continuous count of days since the beginning of the day starting at noon on January 1
hypolimnetic oxygen changes with season
oxygen depletion from spring – summer (lowest O2 with +F)
hypolimnetic oxygen chantes in Haynes lake and lake StGeorge
both reach min. in June, S.G. stays at ~0 for rest of summer, H. increases to second max in late July-early August. Lake H. never goes to 0
algae size and relative sedimentation rate
small grazer system = short phosphate turnover time = lower relative sedimentation
why larger grazer system has higher relative sedimentation
large things sediment more, greater proportion sink, heavier, less efficiently used (P turnover)
absolute sedimentation rates
would be higher in small grazer system because there’s so much more
toxic algal groups
cyanobacteria, dinoflagellates, diatoms
problems with algal blooms
toxins, anoxia, habitat loss, recreational loss, health risks
anthropogenic P, N to aquatic systems lead to
eutrophication algal blooms fatal algal toxins anoxia- loss of diversity/habitat proliferation of waterborne pathogens increased chlorination byproducts in drinking water
waterborne pathogens especially important in
tropical/subtropical regions, can be related to cholera
forms of land-use
agriculture farming waste disposal fertilizer harvesting hydrology
effects of N,P loading are different
depending on structure of system
shallow vs. deep
large vs. small fish
population growth
increasing pop., more mouths to feed, more land-use required, world fertilizer growth, more N,P loading,
obtaining N, P for fertilizer
N atmospherically available, easier to obtain. P not atmospherically available, geological nutrient, limited
problem with speed of population growth
available, cultivatable agricultural land is NOT increasing, need GMOs to keep up with pop. increase
GMOs to keep up w/ pop. increase
rices that can grow through floods - multiple crops/year
problem with GMOs that allow us to increase agricultural yield
leaching soil nutrients, more and more fertilizer
population growth and water shortage
water hungry plants and animals (and nutrient loading)
examples of water hungry crops
70L/apple 3400L/kg rice 140L/cup of coffee 120L/glass of wine 15,500L/ kg of beef
changes in atmospheric NH4
30% increase in urea use as fertilizer (1960-1990)
observed relationship between N,P and Chl
positively correlated
nitrogen more tightly correlated
eutrophication defined as
excessive growth of algae, often associated with bluegreen and other harmful algal blooms
determines types of algal bloom
amount of nutrients, composition of nutrients (TN:TP)
N:P ratios for different runoff types
unfertilized field N:P 250 forests 75 rainfall 25 manure seepage 9 sewage 5
nutrient composition ratio
dependent on where nutrients come from
dictates algal bloom
bluegreen algae associated with what nutrient composition
low N:P ratio (towards the manure, sewage deposits)
differential response to increased [P] in N limited vs. P limited ecosystem
N limited systems does not respond as strongly to increased P
increasing phosphorus concentration =
increased dominance of cyanobacteria
other controls on levels and types of algal biomass blooms
seasonality of nutrient inputs (coastal and freshwater ecosystem)
physical properties of receiving system
structure of foodweb
N:P ratio as a control in number of red tides
as N:P decreases, #red tides increases, highest below 16
duration of blooms longer when N:P
redfield ratio
N:P
16:1
increasing nutrient, increasing algal biomass
responses are not proportional in all systems, dependent on structure of foodweb (small vs. large grazers) and physical structure of ecosystem
physical lake structure and response to changes in nutrients
deeper lakes can take more ‘abuse’ before showing response (less likely to become eutrophic)
algae harmful to animals, humans
cyanobacteria (bluegreen)
dinoflagellates
some diatoms
types of algal toxins
neurotoxins
hepatotoxins
lipo-polysaccharides
neurotoxins
alkaloids, b/g algae
cause neurodegenerative symptoms through disruption in communication between neutrons and muscles
neurotoxin examples
anatoxin-a, saxotoxin, neosaxotoxins, Nostoc, Anabaena, Oscillatoria, Aphanizomenon
hepatotoxins
peptides
affect liver, cause weakness, vomiting, diarrhea, respiratory blockages
hepatotoxin examples
Anatoxin-a, saxotoxin, neosaxotoxins, Nostoc, Anabaena, Oscillatoria, Microcystis
Lipo-polysaccharides
cause skin irritation (dissolve skin)
neurotoxin bioaccumulation
accumulate in nervous system (cerebral), show up with age
fertilizer use and red tides
increased fertilizer use tightly correlated with increased # of red tides
TP, TN and toxin forming algae concentration
both positive correlations
steeper increase in toxin forming algae with increased TP then increased TN
concentration of microcystin vs. toxigenic biomass
increasing. the more biomass present, the more of the toxic variety
microcystin
class of toxins produced by certain freshwater cyanobacteria
ubiquity of cyanobacteria
terrestrial, freshwater, brackish, marine, widespread = potential for widespread human exposure
β-N-methylamino-L-alanine
BMAA- novel neurotoxic amino acid from cyanobacteria (and many algal taxa around the world), ubiquitous, accumulate and slowly release through time, found in brain tissues of people who die of ALS and other neurodegenerative disease
BMAA in guam
high concentration in coralloid roots of cycad trees– concentrated in fleshy seed– flying fox forage on seed– accumulate– Chamorro people eat them– die of ALS-PDC. 50-100X incidence rate anywhere else
BMAA biomagnification
free BMAA–cyanobacteria 0.3µg/g— cycad 37µg/g – flying foxes 3556µg/g – Chamorro people
Chamorro people
highest rate of neurodegenerative disease in the world
water categories based on nutrient richness
Oligotrophic- nutrient poor
Mesotrophic- good clarity, average nutrient
Eutrophic- enriched with nutrients, good plant growth, possible algal blooms
Hypertrophic- excessively enriched with nutrients, poor clarity, devastating algal blooms
lake Taihu
went from oligotrophic (1960) to eutrophic-hypertrophic in 90’s
population growth, livestock growth
toxins produced
ALS
amyotrophic lateral sclerosis
BMAA exposure in desert dust
soldiers found to have high levels of BMAA, suffering from neurodegenerative disease from Iraq desert pools. dormant until rain season. inhaled, especially around Gulf War.
sporadic ALS in Annapolis, Maryland
found to come from Chesapeake Bay blue crabs, BMAA in Chesapeake Bay food web common risk factor
fa cai, Mandarin; and fat choy, Cantonese
Nostoc grown and harvested to make soup during New Years celebration. Banned now, mostly artificial, but some still contain Nostoc (BMAA).
driving force in aquatic system
foodweb
changes to food web have cascading effects
ecosystem productivity depends on
transfer efficiency of nutrients and energy along foodweb- affected by changes in predators and prey- any affects = cascading changes
shifts in food web structure and function, implications for
predator/prey effects
contaminant transfer
biodiversity
productivity
