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1. Longitudinal Patterns in ecological organization of Rivers •Patterns in species richness •Patterns in species composition •Patterns in functional organization •Patterns in habitats and environmental template 2. Processes and Mechanisms… Species area curves for Stream Fish in 356 Catchments: Lower Peninsula, Michigan 6 5.5 ln Fish = 1.42 + .23 * ln Area; R2 = .31 5 4.5 ln No. of Species 4 3.5 3 2.5 2 1.5 1 .5 3 4 5 6 7 8 9 Catchment Area (ln km2) ln No. of Species Species Diversity of Stream Fish Assemblages in 18 Major River Basins: Lower Peninsula, Michigan ln Fish = 1.25+ .36 * lnArea; R2= .83 4.75 4.5 4.25 4 3.75 3.5 3.25 3 5.5 6 6.5 7 7.5 8 8.5 Basin Area (ln km2) 9 9.5 10 (Sepkowski and Rex 1974) Bivalve [Unionidae] spp in Atlantic coastal rivers Longitudinal Zonation in species composition Observations •Carpenter (1928) •Huet (1949-1962) •Illies et al. (1955,1963) •Statzner (1986) Theories Huet’s fish-zones of Western Europe (1949-1962) Huet’s “slope rule” for western European streams Illies (1955) Major River Zones Crenon Rhithron Potamon Source areas: glacial meltwaters, springs, wetlands, lakes. small very cold, low to moderate slopes, fauna variable Mean monthly temp rises to 20 C; high oxygen concentrations flow is turbulent; erosional, gravel-cobble substrate predominate Fauna is cold stenothermal. No true plankton. Mean monthly temp above 20 C; oxygen deficits may occur. Flow is slower, tends towards laminar. Sand and finer substrates are dominant. Fauna is eurythermal and most species well-adapted to lentic settings. Plankton develops. Illies and Botosaneanu (1963) Latitude: high middle low Illies (1955) What causes Longitudinal variation in biological communities? Variables associated with longitudinal patterning •changes in biological community •temperature •substrate •hydraulics (slopes, velocities, power dissipation) Processes associated with longitudinal structure •changing landscape controls on carbon production [light, nutrs, alloch source] •demographic equilibria •changing temperatures •patterns in hydraulic stress and disturbance •increasing habitat diversity with hydrologic scale •population interactions (predation, competition, and disease) •{changes in water quality} The River Continuum Concept [RCC] Vanote et al 1980 Key ideas in the RCC Hydraulic gradients organize carbon sources for the food web Hydraluic gradients organize temperature variability Community composition equilibrates to carbon sources Species diversity reflects temperature variability emphasis on continua [gradients] rather than zones background concepts Sources and fate of organic carbon two general categories for sources allochthonous from “outside” soil water, leaves, woody debris, blown in insects,etc. autochthonous from “self” aquatic primary producers:vascular plants, algae, autotrophic bacteria •terrestrial versus aquatic origin •here versus there RCC background concepts Veg Edge/area allocthonous [terrestrial leaves, wood, DOC] autochthonous [algae+ macrophytes] Veloc Nutrients DETRITAL POOL Ldecomposers Bacteria & fungi L1 L0 L2 grazers shredders collector-gathers filter-feeders invert predators Light invertivorous fish /birds L3 L4 piscivorous fish L5 piscivorous birds /mammals NR411 River Food Web BASICS trophic role: decomposer food web position: trophic category: functional feeding designation: Common Name Principal Taxa ?? bacteria x ?? fungi x macro Algae Chlorophyceae and others diatoms Bacillariophyceae mosses Bryophytes aquatic plants Macrophytes sow Bugs Isopoda scuds Amphipoda snails Gastropoda clams Bivalvia mayflies Ephmeroptera stoneflies Plecoptera dragonflies Odonata damselflies Odonata bugs Hemiptera alder and dobson flies Megaloptera caddisflies Trichoptera 2-winged flies [e.g. midges, Diptera blackflies] butterflies Lepidoptera crayfish Decapoda boney fishes teleost fishes birds various spp [kingfishers, mergansers, herons] mammals otter, mink, beaver, people producer primary consumer primary herbivore detritivore/omnivore grazer shredder filter-feeder collector secondary tertiary invertivore piscivore predator predator x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x Relative importance of autochthonous and allochthonous inputs often a matter of physical opportunity e.g. lakes versus small woodland stream auto>allo allo>auto CPOM allo?auto DOC sometimes a matter of human intervention-e.g.: organic pollution Death, Detritus and Decomposition allochthonous inputs are already usually dead or soon dead -> detrital carbon autochthonous carbon eventually dies -> detrital carbon because HOH is a solvent, the chemical nature of detritus rapidly diverges from that of living carbon role of the biota bacteria & fungi colonize detrital surface and enzymatically extract labile compounds larger macro-invertebrate shredders (caddisflies, craneflies, some stoneflies, amphipods etc.) mechanically breakup larger pieces (CPOM) while feeding on attached decomposers and in some cases on the CPOM itself… really feeding on the microbial community on the CPOM; like peanut butter on a cracker Carbon form Lipids Carbohydrates Deciduous leaf Deciduous wood bacteria fungi Aq. macrophytes 8 2-6 10-35 1-42 4-5 22 1-2 5-30 8-60 20-70 Cellulose/ structural polysaccharides 29 36-50 4-32 2-15 14-61 Protein 9 insig 50-60 14-52 8-35 Decomposition in an aquatic environment Decomposition Autolysis + leaching + mechanical breakdown + biochemical mineralization by respiration generally involves a serial reduction in both size and quality CPOM->FPOM->VFPOM<->DOM -> INORG C mediated by biology bacteria,fungi,shredders, fp detritivore % remaining Decomposition rates time masst = massinit * e -Kt Example plant White oak (Quercus alba) Dogwood (Cornus amomum) K (days -1) .005 or less .010-.015 T50 4.6 months 1.5-2.5 months T90 >15 months 8 months Cattail (Typha latifolia) Najas (N.flexilis) Pondweed (Potomogeton spp.) .01 .022 ~.1 2.5 months 1+ month 1 week 8 months < 4 months < 1 month •differential decomposition rates •Allochthonous: willow>alder>dogwood>maple>aspen>oak>pine&spruce •Autochthonous: algae> submersed aquatic macrophytes> emergent/terrestrial macrophytes • life cycle timing of shredders often cued to cued to leaf fall in temperate NA 2 sources: allochthonous and authochthonous 2 pathways: detrital and herbivorous allocthonous [terrestrial leaves, wood, DOC] autochthonous [algae+ macrophytes] DETRITAL POOL Ldecomposers Bacteria & fungi L1 L0 L2 P/R = Ecosystem Photosynthesis /Respiration grazers shredders collector-gathers filter-feeders invert predators invertivorous fish /birds L3 P/R ~ autoch /(autoch + alloch) P/R ~ total carbon produced/ total carbon respired L4 piscivorous fish L5 piscivorous birds /mammals P/R>1 autotrophic Photosynthesis Org Carbon Respiration P/R<1 Org Carbon heterotrophic Respiration Photosynthesis Photosynthesis Heterotrophic (dystrophic) P/R<1 Org Carbon Allocthonous inputs Respiration Advective transport “downstream” The River Continuum Concept [RCC] Vanote et al 1980 Caveats… Number of taxa Species- Area Relationships Observed: log-normal distribution Number of individuals Darlington 1952 Preston 1962 MacArthur and Wilson 1967 Sample size Log S = .263 J/m + 3.17 S …# of spp J …# of individuals in sample m …# of individuals in rarest spp if randomly dispersed J~ area sampled S = c AREA Z Z= theoretical = .26 insular fauna= .23-.35 non-insular = .12-20 Immigration rate larger Equilibrium Theory smaller [Island Biogeography 1967] Number of species harsher milder Extirpation rate Immigration rate Extirpation rate MacArthur and Wilson’s Number of species Demographic equilibrium applied to river networks upstream Number of species Harsher-less storage Milder-more storage- Extirpation rate Immigration rate Extirpation rate Immigration rate Downstream-larger upstream species pool Dowbstream equilib. Upstream equilib. Number of species Temperature its’ effect on biology is profound Zonation and temperature Some thermal changes are more important than other SHORTWAVE RAD. BLACKBODY CONVECTION LONGWAVE RAD. EVAPORATION Ground water ADVECTION CONDUCTION Tributaries ADVECTION Proximate mechanism:heat Budget Water temp = heat units/volume * 1/specific heat Heat Balance Equation: dheat/dt = S Radiation (short-wave) Radiation (long-wave) Back Radiation Convection Conduction Evaporation Advection f(SA,sunlight) f(SA,air temp) f(SA, water temp) f(SA,temp diff,wind) f(Perim,soil temp) f(SA,humidity,wind) f(source temps) Proximate mechanism:heat Budget dheat = Radiation (short-wave) Radiation (long-wave) Back Radiation Convection Conduction Evaporation Advection f(SA,sunlight) f(SA,air temp) f(SA, water temp) f(SA,air-water temp diff, wind) f(Perim,soil-water temp diff) f(SA,water temp, humidity,wind) f( confluing source temps) when dheat = 0, temperature equilibrium (constant) Temp equil = T0 e-kt Proximate mechanism:heat Budget Longitudinal effects: Runoff routing Velocity? Volume (Q) ? Te GW routing Ultimate mechanism:landscape dheat/dt = S Key modifying factors Radiation (short-wave) Radiation (long-wave) Back Radiation Convection Conduction Evaporation Advection f(SA,sunlight) f(SA,air temp,riparian structure) f(SA, water temp) f(SA,air-water temp diff, wind) f(Perim,soil-water temp diff) f(SA, temp, humidity diff,wind) f( confluing source temps &vol) riparian shade,climate riparian shade,climate water temperature channel shape,climate channel shape,climate wind, riparian conditions Stratification effects f(lentic volume,SA,strat) lakes,wetlands,reservoirs hydro-geology,landuse heat content proportional to volume heat flux proportional to surface area July mean Co 30 25 20 15 10 5 0 0 2000 4000 6000 8000 10000 Watershed Area km2 12000 14000 16000 Proximate mechanism:heat Budget Diel effects: Te_day Te_night Velocity? Volume (Q) ? 2899 2738 2577 2416 2255 2094 1933 1772 1611 1450 1289 1128 967 806 645 484 323 1 2917 2755 2593 2431 2269 2107 1945 1783 1621 1459 1297 1135 973 811 649 487 325 163 -2 162 1 18 16 14 12 10 8 Upper Cedar April, 2003 6 4 2 0 16 14 12 10 8 Lower Cedar April, 2003 6 4 2 0 20 July mean Co Daily flux Co 18 16 14 12 10 8 6 4 2 0 0 2000 4000 6000 8000 10000 12000 14000 16000 0 2000 4000 6000 8000 10000 12000 14000 16000 30 25 20 15 10 5 0 Watershed Area km2 20 Daily flux Co 18 16 14 12 10 8 6 4 2 0 0 2000 4000 6000 8000 10000 12000 14000 16000 Longitudinal Gradients in depth, velocity, substrate, shear stress, Catastrophic disturbance Velocity Position and movement shear Habitat utilization substrate Diffusion, Reaeration & metabolism A Lotka-Volterra 3 species simulation dx/dt = rX - (kxX - ayxY - azxZ) 1/kx dy/dt = rY - (kyY - axyX - azyZ) 1/ky dz/dt = rZ - (kzZ - ayzY - axzX) 1/kz axx ayx azx .5 .75 .5 axy ayy azy .3 1 .7 axz ayz azz .1 .1 1 xr .01 kx yr .007 ky zr .05 kz 600 red 1000 blue 500 green Disturbance frequency = 0 Disturbance frequency = 2 Disturbance frequency = 4 Disturbance frequency = 0 Disturbance frequency = 7 Disturbance frequency = 13 Disturbance frequency = 0 Disturbance frequency = 20 Disturbance frequency = 100 Number of species Total population size Intermediate Disturbance Hypothesis Log Frequency of Disturbance Geomorphic effects on Biology Nutrient gradients and the regional structure of stream communities C.H.Riseng, M.J Wiley and R.J. Stevenson2 80,000.0 60,000.0 40,000.0 30,000.0 20,000.0 Benthic Biomass (mg m -2 ) 10000.0 6,000.0 4,000.0 3,000.0 2,000.0 1000.0 600.0 400.0 300.0 200.0 100.0 60.0 40.0 30.0 20.0 10.0 6.0 4.0 3.0 2.0 1.0 0.0 2 3 4 5 6 7 8 0.1 2 3 4 5 6 7 8 (Critical SS for d84 / gRS) bankfull 1.0 2 3 What kinds of Disturbances might potentially shape stream insect communities? High Flow events (Floods) Low flow events (Droughts) Pathogen outbreaks (Disease) Catastrophic disturbance Velocity Position and movement shear Habitat utilization substrate Diffusion, Reaeration & metabolism Because the rate of molecular diffusion is faster in air than in water all organisms that take dissolved oxygen from the water to support their metabolism face a fundamental physical constraint related to diffusion rate: Fick’s Law again provides a basic description of this diffusive process diff rate = K (saturation - concentration) diff rate = kA/L (pO2 inside - pO2 outside) k=rate constant characteristic of the type of tissue oxygen must diffuse across (gill, cell wall. etc.) A= exchange surface area where diffusion can occur L= diffusion distance (how far molecules must travel) (pO2 inside - pO2 outside)= gradient in partial pressure of oxygen (pO2 inside - pO2 outside) gradient in oxygen concentration effectively depends on the external oxygen concentration since internal oxygen levels almost always low for a simple imaginary organism resp rate time time 1 begins with resp rate set by kA/L and the external O2 concentration but rate of resp decreases with time occurs because of O2 depletion immediately around exchange surface resp rate average diffusion distance time 2 time average diffusion distance Intrinsic problem with diffusion in water due to relatively low diffusion coeff in water time 3 solution: ventilate replace water at exchange surface average diffusion distance Stenacron As the environmental O2 concentration declines, the concentration gradient in Fick’s eq, also declines... regulators must compensate by ventilating more rapidly in order to decrease the diffusion distance and offset the gradient decline. Many aquatic animals actively ventilate exchange surfaces ventilation periodically replaces spent water controlling deterioration of diffusion distance animals which manipulate diffusion distance or other parameters of Fick’s law are called respiratory regulators animals ventilate by different methods e.g. mayflies, fish, dragonflies Not all aquatic animals invest energy and tissue in diffusion regulation organisms which let their respiration rate vary with ambient O2 levels are called respiratory [ metabolic] conformers conformers respiration rate regulators oxygen concentration Concentration-velocity tradeoffs For conformers current velocity can act as a substitute for O2 concentration in terms of regulating respiration rates. For regulators reduced velocity requires more work and therefore energy Heterotroph oxygen requirements Even regulators have a concentration below which they can not further compensate by ventilation, below that critical concentration metabolic rate declines with declining oxygen. For regulators, this critical concentration represents a concentration threshold below which an organisms energy supply rapidly declines. When respiration rates are only sufficient meet current maintenance costs, there is no excess eenergy to invest in foraging, growth or reproduction. The concentration of oxygen which provides only this level of respiration is known as the incipient lethal level, since an organism/population (although it may live for some time) cannot achieve reproductive below this level. At some low concentration (the acute lethal level) respiration rate is so far below immediate maintenance needs that rapid death follows. Respiration rate maintenance rate critical concentration incipient lethal level acute lethal level Oxygen concentration ----> } scope for activity Sublethal affects of low oxygen When [O2] lies between the critical concentration and the incipient lethal level, an organisms ability to do physiological work is diminished. reduced oxygen can have important sublethal affects on feeding, growth, locomotion and even survival Lethal Limits Acute lethal levels of oxygen vary considerably between organisms •Concentrations below 1-2 ppm are lethal to a wide array of aquatic organisms. •Concentrations below 4 ppm are lethal to many, a common regulatory water quality standard. •Some organisms can survive <1 ppm (are especially tolerant) and dominate low oxygen environments. Acute lethal [O2] ppm •Velocity - [O2] tradeoffs can be important here too, especially for conformers. 1 2 3 4 5 current velocity cm sec-1 6 What determines Oxygen concentrations? ATMOSPHERE Henry's law for gases dissolved in water [c]=solubility * partial pressure [c] is the equilibrium saturation conc = the concentration the system reaches if left alone note it is independent of starting concentration Henry's law ATMOSPHERE [c]=solubility * partial pressure [c] is an important benchmark if water conc > henry's saturation value then atm is a sink if O2 is less than saturation concentration: atmosphere is a source Henry's law applies to all gases in the atmosphere Different partial pressures and different solubility lead to different concentrations in aqueous solution. Partial pressure% CO2 0.03 02 20.99 N2 78.0 ppm solubility at 0 C solubility at 10 C solubility at 20 C solubility at 30 C 3350 ppm 2320 ppm 1690 ppm 1260 ppm 69.5 ppm 53.7 ppm 43.3 ppm 35.9 ppm 28.8 ppm 22.6 ppm 18.6 ppm 15.9 ppm saturation at 0C saturation at 10C saturation at 20C saturation at 30C 1.005 ppm 0.70 ppm 0.51 ppm 0.38 ppm 14.5 ppm 11.1 ppm 8.9 ppm 7.2 ppm 22.4 ppm 17.5 ppm 14.2 ppm 11.9 ppm ATMOSPHERE How long does it take Oxygen to reach saturation? Fick’s Law provides a basic description of the rate at which diffusive processes occur. diffusion rate = K ([Saturation] - [O2 ] ) k = rate constant, sometimes called the diffusivity Bulk reaeration rate k = f[molecular diffusivity and eddy diffusion (turbulence)] ATMOSPHERE Fick’s Law implies that Oxygen concentration approach equilibrium asymptotically When [saturation-DO] is large, rates of exchange with the atm are high When [saturation-DO] is small, rates of exchange are small The direction of oxygen exchange depends on Henry’s law •if over-saturated (supersaturated) water will lose oxygen to atmosphere •if under-saturated, water will gain oxygen from the atmosphere diffusion rate = K ([Saturation] - [O2 ] ) Saturation diffusion 0 rate time Output 2 Using a Mass Balance Approach Boxes = mass storage arrows = rates of flux Mass Input 1 Output 1 Input 2 then Dmass in storage per unit time = Sinputs - Soutputs For the example diagram above d/dt Mass=[ (Input 1 + Input 2) - (Output 1 + Output 2)] ATM Mass balance for O2 diffusive aeration photosynthesis O2 respiration DO2 = Photosynthesis - Respiration diffusion d/dt O2=[ P - R k([saturation]-[O2])] ATM Streeter-Phelps Model diffusive aeration O2 Respiration due organic pollution Carbon and nitrogen (ss +diss) DO2 = Respiration diffusion d/dt O2=[R k([saturation]-[O2])] predicts an temporary oxygen sag downstream form sewage plant effluents Diffusion is a constant process, but biological activity is not. Photosynthesis varies in a regular diel fashion following the availability of light. The O2 mass balance 100% Saturation equation can be thought of as having two distinct forms: during the day DAY NIGHT DAY supersaturated 100% Saturation DDO=P-R± k[saturation-DO] but during the night DDO=R± k[saturation-DO] since P=0 The shape of this diel oxygen curve is determined by the relative magnitude of the component rates [diffusion, photosynthesis and respiration]. When diffusion rates are high due a high reaeration coefficient (k) and biological rates are relatively low, almost no diel sag is detectable-- diffusion swamps the P-R term in the mass balance. diffusion +++++++++++++++++++++----------------------------------++ P-R ++++++++++------------------------------------++++++++ DAY DAY supersaturated 100% Saturation 100% Saturation diffusion -+++++++++++++++++------------------------------- P-R +++++++++++------------------------------------++++++++++ DAY When biological rates are high (e.g., nutrientrich systems like agricultural streams) or diffusion rates are relatively slow (e.g. stagnant ponds), biological processes can swamp diffusion rates and lead to widely fluctuating diel curves NIGHT NIGHT DAY supersaturated 100% Saturation 100% Saturation diffusion ---++++++++++++++++++-------------------------------------- P-R +++++++++-------------------------------++++++++ Catastrophic disturbance Velocity Position and movement shear Habitat utilization substrate Diffusion, Reaeration & metabolism Mapping approaches to Longitudinal Structure Where Homogeneous longitudinal units [ geomorphic/ecologic] data Landscape (GIS) data Registered field data Model projections Scale Valley segments Reaches Basins Current examples: MRI-VSEC (IL,WI verions); TNC Macrohabitat Classifications USGS Aquatic GAP program Geomorphic Valley Segment Classifications [Hupp] Geomorphic Reach Classifications [Rosgen] What is Ecological Unit Mapping? “Identifying the basic [structural] units of nature” (Rowe 1991) Geomorphic character Biological character Integrated Ecological Character of a River Segment Hydrologic character Chemical character Raisin River mainstem units Central role of GIS Michigan Rivers Inventory VSEC units MAP 10 km 270 main river segments and 400 tributary units [mri-vsec v1.1] Grazers: Animals that feed on living algae or macrophyte tissue. Some are free roaming, others are central-lace foragers making short excursions out from some central tube or burrow.Specialization by growth form common but not by plant species. Food types: algae, vascular plant tissue (rare) examples: many mayflies, many midges, many cased caddisflies, some stoneflies Shredders: Animals that feed on large allochthonous organic carbon fragments (e.g.leaves) which have been colonized by bacterial and fungal communities. Some shedders have commensal gut flora to assist in the digestion of cellulose. A few have specialized enzymes to assist in the same task.. Food types: coarse particulate carbon (CPOM), and associated microflora examples: Cranefly larvae (Tipula), Giant stoneflies (Pteronarcys), many cased caddisflies, scuds Filter Feeders: Animals that feed by filtering suspended Organic material from the water column. Filtering mechanisms can be anatomical [e.g. blackflies] or more elaborate constructions involving silk capture nets [e.g. some Caddisflies and midges] Food types: animal, algae, detritus examples: blackflies, net-spinning caddisflies, burrowing mayflies Collector-gatherers: Omnivorous animals that feed by moving around the substrate in search of fine particulate organic matter (FPOM) which is either ingested on the spot, or retrieved and accumulated at some central tube or burrow. Often includes embedded algae and even small animals. Food types: algae, detritus examples: some mayflies, many midges and worms (tubificids), scuds Predators: Animals that feed on other animals. An invertivore feeds principally on invertebrates. Food types: animal tissue examples: dragonflies, many stoneflies, water scorpions and other bugs, most smaller fishes