Ecology of Lyme Disease

background

lyme diease occurance and prevalence is a results of food web interactions

Major organisms: Borrelia burgdoferi, deer tick, white-tailed deer, white-footed mouse, gypsy moth

*occurs in forest ecosystems, especiall north temperate forests*

Lyme Disease and Food webs:

Biodiversity and the Dilution Effect

Ticks have multiple hosts: some have better borrelia reserviors than other; mouse is a "good" host

Not as effective reservoir results:

1) Increased diversity of potential hosts species may decrease percentage of infected ticks (ie, those carrying the bacterium borrelia)

2) Relatively high host species richness may "dilute" the infection incidence

3)Therefore, less chance of humans getting disease

Ecosystem Ecology and the Ecosystem Concept

defintions

Ecosystem: biological community and all of the abiotic conditions that influence structure and function

Arthur Tansley: gave first defintion of ecosystem and proposed ecosystem concept

Ecosystem ecology: Examine the fluxes of energy, nutrients or other materials in an ecosystem and the biotic factos that affect those fluxes

-pools: quantities of matter or energy in a compartment

-flux: flow of energy or matter through the ecological system

Controls of Ecosystem Processes

5 independent factors

Climate: dominant on broad scales; weather of soild difference b/w desert/TRF

Parental Material: unique geologic history

Topography: directional etc

Biota: diversity and type of organisms with history of coevo

Time: Soil development + evolution of organisms

Primary Production and Energy Flow

Energy fixed via photosynthesis: supports plants and produces the organic matter that is consumed by animals and microbes

Primary production:Carbon fixation by autotrophs in an ecosystem

GPP = the sum of PSN by all leaves in the entire ecosystem; integrated over daily to annual tune scales, *impossible to measure net Carbon exhange for entire ecosystem - models are used

-models suggest that leaf-level studies can usually be extrapolated to larger ecosystem-scale measurements

Leaf Area Index (LAI): leaf area/ground area; can potentially determine C fixation rates; directional source

Increased LAI = Increased GPP

Duration of Photosynthetic Season: accounts for much of the differences in GPP among ecosystem types

Environmental Controls: over GPP suring the growing season are the same to those for PSN of indiv. leaves

Light Availability

Net Primary Production (NPP)

Net Primary Production: the net C gain by primary producers; balance b/w C gained via GPP and the C lost by plant RSP

NPP = GPP - R_plant

new biomass, Organic Matter exuded by roots and/or cells, any C transferred to symbiotic microbes, and volatile organic C compounds

Root and cell exudates are generall used quickly by microbes and are considered root and/or microbial RSP

Volatile emissions are not generally measured; minor

Some new biomass dies or is consumed before measurement, so NPP are often underestimates

Only 1% of solar energy captured by plants and converted to NPP

Forests tend to be more efficient than aquatic systems; Efficiency = energy fixed/energy in light

2-15% of NPP in consumed by herbivores

*low assimilation efficiency; <1%

20-50% of herbivore mass is consumed by predators

*Much higher assimilation efficiency (animal tissue converted to animal tissue

Temperature and moisture influence NPP in temperate systems

Highest NPP rates are predicted in warms, moist cimates

Lowest NPP rates predicted in low moisture/temp systems

Evapotranspiration- NPP relationship across a Diversity of Ecosystems

Trends:

*Terrestrial primary productions increases with actual evapotranspiration

*Actual Evapotranspiration increases with increased precipitation and temperature*

 x-axis: acutal evapotranspiration

y-axis: NPP

Terrestrial Ecosystems

other factors affecting NPP rates

Nutrient availability (soil fertility): Crops have increased yield under fertilization

Limiting Nutrient Concept:

1) a nutrient which limits the amount of PP in a system

2) Liebig's law of Minimum: states that PP is limited by the butrient most required relative to its supply; can only apply to 1 nutrient

Tundra fertilization experiment

*NPP increases when nutrients are added*

N+P increased PP in both dry and wet meadows

wet meadows had more because of hypothesis that moist systems will have higher PP

Phytoplankton = PP

.5% of light energy converted to PP

20-30% of NPP eaten by zooplankton

20-30% of herbivore prod eaten by zooplanktivorous fish

20-70% of zooplanktivorvous fish eaten by fish eaters

*assimilation efficiencies are much higher and is fairly consistent across trophic levels; around 75-82%

PP in freshwater systems

limiting factors

Solar Radiation: PAR extinguishes rapidly with depth

Temperature: water temp linked with amount of solar radiation

Nutrients: P, N, Si, Ca, S, K etc

Higher P concentrations are associated with greater algal biomass

As algal biomass increases, rate of Primary Production increase

Phosphorus has shown to cause increased algal levels thus increased rate of PP

Indicated Phosphorus as a major cause of Cultural Eutrophication

Bluegreen algae are often strongly P-limited b/c they have the ability of fix atmospheric Nitrogen

Management of water quality = phosphorus management in many lakes

*can vary seasonally*

Productivity is lower than many terrestrial systems

trend of higher productivity in coastal areas opposed to open ocean

Continental Margins: River discharges, runoff, nutrient pollution, disturbance of bottom sediemnt

Upwelling Zones: deeper, more nutrient rich waters come up to surface and stimulate production

Thermal Stratification and Vertical Mixing: in open ocean; sediementation and nutrient depletion, equitoral regions may have permanent thermocline

Bottom-up: physical and chemical factors determine the amount of PP in a system; temp, moisture, nutrients

Top-Down Control: Consumer influences dictate the amount of PP in a system

Trophic Cascade Hypothesis

Food web structure will affect how much primary production occurs in a system

Specifically: predation effects of top consumers

Can potentially affect productivity of the system by manipulating biomass of top carnivores

*Hypothesis proposes that feeding by piscivores and planktivores affects the rates of PP.

Implications:

-Biomanipulation: manipulation of lake biota to improve water quality (decrease algal biomass and productivity); **stock piscivores, remove planktivores, predation refuges for large zooplankton**

much cheaper to use biomanipulation than institute large-scale nutrient abatement programs

Simple trophic-level concept of complex food webs: community complexity or diversity may dampen pred effects

Systems must be strongly recipient controlled: few refuges from preds/limited omnivory

Must have limited spatial and temporal complexity

Context dependent consumers effects

most examples are from freshwater systems

Nutrient Processor: indivduals transform and move nutrients from one place to another

Biogeochemical cycles: Biological exchanges of nutrients interact with chemical/physical exchanges in the env.

-Global Nutrients Cycles are Closed: atoms cannot be destroyed

Ecosystems are open: externally-derived nutrient inputs

Compartments: nutrients reside within a group or groupings of biotic or abiotic things

-pool of nutrients

-uptake and outflow

-flux rate: amount of nutrients/area/time

Nutrient cycle=flux rates+pool sizes

Addition of a tracer element

radioactive: carbon14, Phosphorus32/33

stable isotope: Nitrogen15, Carbon13

used to infer carbon sources and trophic position of consumers

Methods for examining nutrient cycle

Hubbard Brook Forest Study

System budget: measures the inputs, outputs, pool sizes and nutrient forms for an entire system

2nd growth hardwood forest

solid bedrock- all water in systems goes out in streams

Methods for examing Nutrient cycle

Hubbard forest study variables

Inputs: Precipitation, Gaseous inputs

Outputs: streamflow, gaseous outputs, 60% stream output to 40% evapotranspiration output

Hubbard Forest Results

clear cut forest had 10x more nitration run off than control forest.

Reason?

The clear cut forest didn't have enough hardwoods to consume the Nitrogen in the soil.  And because bedrock underlies the forest, the soil cant absorb much Nitrogen, thus during run off events, more nitrogen is carried down stream

Meterological: Dissolved matter in rain and snow, atmospheric gases, wind-blown dust, sea spray

Geological: surface and subsurface drainage

Biological: Animal movement between habitats

Decomposition is the major process the recycles nutrients in ecosystems

-Rates of nutrient supply to primary producers in nutrient-limited systems are dependent upon the conversion rates of organic nutrients to inorganic.

-Decomposition: physical and chemical breakdown of organic matter

-Mineralization: during decomposition