Aquatic Ecology and our World of Water Lecture Notes PDF

Aquatic Ecology and our World of Water Lecture 1 What are we here to study Aquatic Ecology Def’n Ecology (noun) - branch of biology that studies with the relations of organisms to one another and to their physical surroundings Aquatic (adj.) – re...

Aquatic Ecology and our World of Water Lecture 1 What are we here to study Aquatic Ecology Def’n Ecology (noun) - branch of biology that studies with the relations of organisms to one another and to their physical surroundings Aquatic (adj.) – relating to water SO…. Aquatic Ecology is the study of ecology in water Water on Planet Earth It’s a Water World!! 1,386,000,000 km3 Salt Water vs Freshwater Aquatic Ecology includes all aquatic environments Marine Ecology Study of ecology in marine (Ocean) environments We aren’t covering that here (check out – BIOL 450) Freshwater Ecology Lakes t rivers Study of Ecology in freshwater environments That’s us!! Global Freshwaters Total Freshwater – 56 million km3 Glaciers – 68.7% Minimal ecology here Groundwater – 30.9% Lots of ecology but not our focus sur face water ecosystems : pretty small ( Lakes, Rivers and Wetlands – 0.4% We will focus on lakes and rivers Lakes, Rivers and Wetlands 3 ecosystem categories ) Lake def’n – a large body of water surrounded by land constant motion in gravitational force River def’n – body of flowing water in a defined channel Wetland def’n – areas where water covers the soil, or is present either at or near the surface of the soil Lakes and Rivers are Wetlands!! ↳ swamp Together make up Surface Waters  Freshwaters are Super Cool and Important!! Highest diversity per area of any ecosystem on Earth Essential resource to human society and all terrestrial life Also the most threatened of all ecosystems on Earth certain amount in there so ecosystem is maintained ecological flow - leaving Human Use of Freshwater Water use can be: making water inaccessible Consumptive - Use precludes future use (example irrigation  water is lost to evaporation), OR Non-Consumptive – water is still available for future use > - hydroelectric dams What is Water used for? Domestic Purposes Washing, drinking, watering lawns (includes municipal uses) Smallest % of water use in most developed countries ~ 8% of global water consumption What is Water used for? Industrial Purposes Fabricating, washing, diluting, cooling, and more Smallest % of water use in most developing countries ~ 23% of global water consumption What is Water used for? Agricultural Purposes Irrigation, Livestock Watering largest % of water use in most countries ~ 69% of global water consumption Is there Enough?? Is it Sustainable?? Total Freshwater Reserves ~ 25 million km3 So no problem, right?? The Water Cycle Replenishes Freshwater supplies Evaporation of salty ocean waters Precipitation of freshwater Runoff of freshwater back to oceans  Global Water Budget Estimated amount of water movement (‘000’s of km3) between compartments Runoff (water yield) is typically difference considered the portion of water between these that is renewable - RUNOFF So approximately 37,000 km3 That is more than 9 times what humans currently use… So we’re good?? distribution problem Water Stress Determined by the combination of water availability and water use Water Quality Value of water is dependent on quality Water use may require: high quality water (example drinking water), OR low quality water (example power generation) Human activities often impair water quality – inhibiting use Looking Ahead Why do Freshwater Ecosystems have so much diversity?? I can show up as a test question What does this usage and impacts on water quality mean for the ecology of freshwater ecosystems?? Why can’t we afford to impair/lose our freshwater ecosystems?? Mini Quiz Select the term that best completes the following statement "The renewable portion of freshwater resources is typically considered to be the amount of _____________." runoff Complete on LEARN page Summary of Key Points 1. Aquatic ecology is study of ecology in water 2. Freshwater makes up a very small portion of water on Earth 3. Humans use water for many things Uses can be consumptive or non-consumptive 4. Renewable freshwater is considered to be runoff portion of hydrologic cycle 5. Water Stress depends on availability and demand in a given area Properties of Water – A Unique Substance Lecture 2 A must remember about water throughout entire course Molecular Structure of Water physical + chemical structure 2 Hydrogen and 1 Oxygen Shared electrons  Covalent Bonds But electrons spend more time near O so slight charge (molecule is polar) just m a ke s it polar * Angle of attachment means + charge is to “sides” of molecule Water molecules “stick” together Hydrogen Bonding Specific Organization Water as a Solvent Best known solvents Solvent = substance capable of dissolving another substance > - good at sticking to other things that a re charged Dissolve both gases and solids Weathering of landscapes Solubility in water is temperature * dependent -very soluble in wate r Gases ↓ with ↑ Temp ↳ temp atoms spread apart less room for them Solids ↑ with ↑ Temp , Water Heat Relations Exists in 3 states at temperatures on Earth High latent heat of vapourization ∴ > - because o f t h e Hydrogen bonds , Water is a liquid water exists a t variety of temp liquid of high needed st a te because energy across a large range of temperatures  Water Heat Relations Specific Heat Capacity Amount of heat required to raise temperature of substance Water has a very high specific heat amount o f energy needed to raise temp of substance Changes temperature very slowly Aquatic environments are thermally stable no endotherms in aquatic environment Pressure Gravitational force on a body in a fluid Increases with depth Gases are more soluble at higher pressure gases more soluble at depth Density of Water – Or Why Ice Floats Viscosity and Buoyancy Viscosity Ability of water to flow Resistance of water due to hydrogen bonding Mixing of water is easier at higher temperatures Buoyancy dictated by density of water Related to density Highest at 4oC Greater with increased solute content ↳ float better in salty water Surface Tension and Capillary Action Hydrogen bonds make water highly cohesive Water “sticks” to itself Cohesion creates surface tension leading to a “surface skin” on water -sticks to other things Water is also adhesive Sticks to solids Allows water to “climb” narrow spaces like pores in soil Movement of Water both liquid andDipe determine flow Types of water flow Laminar Slow · orderly Flow Turbulent · faster all over the place flow , disorders transitional flow is a mix of both Turbulent flow increases with velocity and roughness Where water changes from turbulent to laminar flow is “flow boundary layer” - microdistant Forces that Move Water Solar Heating Leads to evaporation and atmospheric transport Energy of the sun becomes potential energy in the water Gravity flowing downhill Precipitation and flow of water down slope Release of potential energy to kinetic energy  Forces that Move Water Wind↳ translates down into water Causes surface waves due to friction at water-air interface Much of movement is rotational most predominant movement in lakes + ponds translate energy down ↓ energy of rotation 1 decreases don't mix very well as you go because of down rotational Forces that Move Water not important in small bodies of water Coriolis Effect Apparent Force caused by Earth’s Rotation Effects only largest water bodies Mini Quiz Which of the following properties of water is NOT because of the polar nature of the water molecule?? gases are more soluble in deeper water Cas you go deeper there is more pressure Complete on LEARN page Summary of Key Points 1. Polar nature of water molecule gives it unique properties 1. Strong solvent 2. High heat capacity 3. Density lower in solid (ice) than liquid (water) 2. Water flow is turbulent or laminar  related to roughness of surfaces 3. Solar energy and gravity generate downslope water movement Movement of Light, Heat and Chemicals in Water Lecture 3 Diffusion of Chemicals in Water not being tested on this Fick’s Law Sconcentration (concentration gradients concentration (𝐶1 −𝐶2 ) difference in in 𝐽= 𝐷(𝑥 −𝑥 ) bigger concentration , faster diffusion 1 2 ↳ space Where: Diffusion flux is a function of diffusion coefficient (D), concentration gradient and distance D is a function of the fluid, temperature, size of molecules, rate of mixing and obstructions ↳ higher temp faster diffusion , Diffusion of Chemicals in Water Molecular diffusion Caused by Brownian Motion Thermal movement of molecules causes random mixing Very Slow!! Dominant mode near solid surfaces or in fine sediments (diffusion boundary layer) flow of molecules mechanism o f distributing Transport diffusion Caused by Turbulent Flow Much faster than Molecular Diffusion Dominant mode if there is appreciable flow Light in Water Interaction between light and water is important: Light is needed for photosynthesis Light is a visual/sensory cue for organisms Light heats water Light in Water When light reaches the water surface: Depends on surface roughness Light entering water (e.g., waves, ice) refracts (“bends”) similar for ice and water flat no ripple water sur face better fo r more light to reflect Light in water is absorbed, reflected or transmitted by water, suspended and dissolved materials Light in Water Light intensity decreases with depth Attenuation  logarithmic molecule , bounce bigger the m o re Rate is determined by rate of reflection and absorption More productive waters attenuate light faster More particles, suspended particles/ organisms and dissolved coloured materials (productivity of the lake) L a ke Huron Light in Water Attenuation varies with wavelength selective to which colour they reflect particles a re Low productivity lakes appear blue Maximum transmission of blues high productivity Maximum absorption of reds lake, low productivity lake High productivity lakes appear green Maximum absorbance of reds and blues  chlorophyll a Maximum transmittance of greens ↳ plants h ave different types of chlorophyll that use different colours Heat Balance in Water ground water typically has a temp ° of 6 C eve n i f its cold outside. In the summer it will get higher Determines water temperature , never than 16 ° Controls biological activity Heat Energy in water is gained by: Solar radiation (light) Diffusion from atmosphere Warmer water source (e.g., precipitation, groundwater, streams) Heat distributed by diffusion and advection Differences in heating can lead to water currents Generate density differences Stratification Glayers forming i n the water Mini Quiz 873039 Based on the described attributes which of the following ponds should have the fastest rate of light attenuation? Complete on LEARN page Summary of Key Points 1. Movement of chemicals in water is by diffusion or turbulent mixing Turbulent mixing is faster 2. Light reach water surface is either reflected or absorbed Depends on angle of light and shape of water surface 3. Light availability decreases with depth  attenuation Function of prevalence of dissolved and suspended particles 4. Water heat balance is function of light absorption, heat from atmosphere and heat from other water sources  Hydrologic Cycle and Physiography of Groundwater Habitats Lecture 4 Aquatic Habitats Many types Groundwater, Wetlands, Streams, Lakes, etc Defined based on geology and hydrology Can be considered at a variety of spatial and temporal scales Habitat Time Range Distance Range Examples Microhabitat 1s–1y 1 um – 1 mm Fine particles of detritus, sand & clay particles Macrohabitat 1 d – 100 y 1 mm – 1 km Riffles and pools in streams, logs, pebbles, macrophytes Local Habitat 1 m – 1000 y 1 mm – 100 km Lake, regional aquifer, stream reach Watershed 1 y – 106 y 1 km – 10000 km Areas feeding small streams to basins of large rivers Landscape 10 y – 107 y 10 km – 10000 km Mosaic of local habitats and watersheds Continent 103 y – 109 y > 10000 km Composite of drainage basins & aquifers Hydrologic Cycle Dictates how water moves and its distribution around the planet Hydrologic Cycle Evaporation of seawater is major source of water to aquatic systems Powered by sun Hydrologic Cycle Precipitation falling on land generates and sustains aquatic ecosystems Global Precipitation Patterns Global air circulation patterns determine spatio- temporal distribution of precipitation Driven by temperature, topography and position of continents Results in varying types and numbers of aquatic ecosystems Hydrologic Cycle Not all precip reaches aquatic ecosystems Much is intercepted by plants and transpired Hydrologic Cycle Precip reaching Earth’s surface can: Evaporate, Infiltrate, or Runoff Water Yield Amount of P=Q+E+∆S precipitation that P=Precipitation ends up as runoff Q=Runoff Regionally impacted E=Evaporation by: ∆S=Change in Storage Temperature Precipitation Locally impacted by: Soils Hydrologic Cycle Water infiltrating soils can percolate the water table and/or move as subsurface flows Movement of Water Through Soil and Aquifers Water in soil creates a number of zones Unsaturated Zone Capillary Fringe Water Table Saturated Zone Unconfined aquifer Confined aquifer Percolation Downward movement of water through the unsaturated zone Determined by soil texture and composition Finer soils (clays and silts) have slower percolation than coarser soils (sands and gravels) with larger pores Rate at which water percolates into the saturated zone (groundwater) is called recharge Hydraulic Conductivity Rate of flow of water through a medium (soil in this case) Dependent on permeability Associated with grain size Material Particle size (mm) Hydraulic Conductivity (m/d) Clay 0.004 0.0002 Silt 0.004 – 0.062 0.08 Coarse Sand 0.5 – 1.0 45 Coarse Gravel 16 - 32 150 Porosity Amount of water that can be held in sediment Volume fraction of pores and fractures As pore size increases Water drains faster More water can be held at saturation Not always positively related with hydraulic conductivity if pores are not connected Groundwater Habitats Homogeneous Groundwater flowing through regions of continuous substrata Water flows in predictable directions E.g., well sorted sand/gravel glacial outwash E.g., permeable sandstone Heterogeneous Groundwater flow is impeded by obstructions or changes in substrate Water flows in variable directions and speeds E.g., heterogenous till moraines E.g., fractured impermeable granite Groundwater Habitats Karst Landforms Interaction of Ground and Surface Waters Hyporheic Zone Transitional zone (ecotone) at bed of aquatic ecosystems Interface for exchange of materials and organisms between ground and surface water habitats Location and size varies over space and time Mini Quiz Select the following description of a landscape that is most likely to generate the greatest amount of runoff. Complete on LEARN page Quiz answer : D? answer - bu Summary of Key Points 1. Hydrologic cycle dictates how water moves around planet 1. Key processes: evapotranspiration, precipitation, infiltration, runoff 2. Runoff is greatest where precipitation is much greater than evapotranspiration 3. Water that infiltrates soil becomes groundwater 4. Movement of groundwater dependent on hydraulic connectivity and porosity 5. Hyporheic zone is interface between groundwater and surfacewater habitats Hydrology and Physiography of Wetland Habitats Lecture 5  area that is wet most of the time Introduction to Wetland Habitats a re a s that accumulate runoff Difficult to define and delineate Often transitional habitat between terrestrial and aquatic ecosystems Delineation based on presence of: -Black Ash tree Hydrophytes - water loving plants want their roots to be wet Hydric soils – high organic soils overlying gray, anaerobic mineral layers material builds up lower in well and saturated organic , more l a c k of oxygen - different vertical zon e s - soil profile mineral layer unoxidized , State (greyblue), Oxidized state Cred) Wetland Functions > - the wate r i s not a good indicator if its a wetland Critical and unique habitats for many plants and animal species > - have a dry and wet cycle Dampen flood events, process and purify runoff biodiversity Hotspots of many biogeochemical cycles E.g., carbon storage and processing leads to m o re animal diversity Draining of Wetlands Draining and filling of wetlands is/has been common in many parts of the world Mostly for agriculture wetland loss ↳ swamp wetlands ~ prarie pothole region  Types of Wetlands wetlands Glow evaporation , m o re Diverse array of wetland types Distributed worldwide Largest complexes associated with large rivers or high latitude glacially influenced areas Broadly classified based on > - coasta lands geomorphology, hydrology, climate, nutrient input and vegetation Two general types – Inland and Coastal Four broad geomorphic classes – riverine, depressional, coastal and peatlands ↳ when they a re wet and dry Types of Wetlands Eastern coast Canada of Coastal (Fringe) Wetlands Fresh or saline Important buffers of storms Include Tidal Salt Marshes Mangrove Swamps Floating Marshes great lakes had coastal wetlands Tidal Salt Marsh storms Extreme environments , Brackish waters – influenced by ocean tides > - wa te r inland m o re saltier Dominated by grasses and rushes Harsh habitats with: Wet dry cycles Large temperature fluctuations Abundant but limited diversity of biota Further inland may be freshwater Higher diversity Mangrove Swamps Coastal wetland Dominated by halophytic trees Occur in areas with: Minimal wave action Sediment accumulation Anoxic sediments Many trees have pneumatophores roots that breathe Species exhibit zonation m o re Inland ↑ 02 Floating Marshes Vegetation forms thick mats of roots that float on water Common in river deltas and other areas that do not experience > - flooding areas that don't experience much change in water levels Inland Wetlands the collects water on edge Depressional and Fringe formations Marshes, Swamps, riverine/riparian, and peatlands size difference in lakes Depressional wetlands form in similar process as lakes Marshes and Swamps most abundant wetland types Highly variable in timing frequency and magnitude of inundation Swamp vs Marsh Defined by vegetation: most swamps do not have standing water Swamps are dominated by trees Trees may have specific growth forms to adapt to inundation Marshes are dominated by herbaceous plants Riparian Wetlands Wetlands (often forested) adjacent to rivers Permanent to ephemeral inundation Flooding is essential Exchange of nutrients and energy between river and forest ↳ organic material Spawning of some fish species linked to flooding Heavily affected by human activities in many areas Pothole Wetlands Marsh ecosystems dry prarie area G Depressions formed by retreating glaciers Common in the Prairies Highly variable in size and water permanency Can be highly saline (evaporation) Very important to many types of waterfowl Peatlands Depressional wetlands that accumulate organic matter Production exceeds decomposition Due to: Low temperature (arctic and subarctic areas) High acidity or alkalinity (Bogs and Fens) Critical global carbon sinks Mined for peat Bogs versus Fens Bogsdependant on precipitation Fens No significant water inflow Receive runoff or groundwater Nutrient poor inputs Acidic (release of humic acids) Neutral to alkaline Lower diversity Higher nutrient concentrations Greater diversity “Smaller Wetlands” Small depressions serve as highly ephemeral wetlands E.g., vernal pools Mostly fed by precipitation Can be seasonal hotspots of diversity Can be created by animals! Wetland Hydrology Hydrologic regimes vary among wetlands Key characteristics: - is italways there at the same time Permanence, Predictability, Seasonality Permanence influences presence of predators Influences lower trophic levels Regional variability in permanence is important Increases diversity More permanent wetlands are source of colonizers to less permanent wetlands Wetland Hydrology Sources of Water Precipitation, Surface water, Groundwater Precipitation sourced wetlands often highly ephemeral Surface waters can provide constant or ephemeral water supply Often directional  downslope Groundwater provides more constant supply, but can be seasonal based on water table position > balance between precipitation and evapotranspiration is important fo r Wetland - Hydrology Evapotranspiration is particular important in wetlands with no inflows Tides are important to coastal wetland hydrology Wetland Hydrology Many subhabitats can exist in a single wetland Different chemistry and hydrology Wetlands and Global Change Wetlands are at risk from warming temperatures Increase evaporation Changing precipitation patterns Increased decomposition rates (peatlands) Will affect plants and animals Impacts will depend on type of wetland Mini Quiz Dr. Yates is doing a tour of a forest with some students when one asks if the forest is a swamp. Which of the following attributes should Dr. Yates NOT use to determine if the area is a swamp? 485776 Complete on LEARN page Summary of Key Points 1. Wetlands are: 1. defined by presence of hydrophytic vegetation and hydric soils 2. classified by location, hydrology, geomorphology, vegetation 2. Perform many ecosystem services 3. Coastal vs Inland wetlands 4. Receive water from precipitation, runoff, groundwater and in some cases tides 5. Can have subhabitats based on water permanence Physiography of Flowing Water Lecture 6 Characterization of Streams Recall: Stream def’n – body of flowing water within a defined channel Also called – rivers, creeks, brooks, etc Why do we have Rivers? Answers: Gravity & Thermodynamics Hydrologic Cycle  Precipitation Gravity cause water to flow down hill Coalescence of water in “low “ areas causes formation of channels A river is born! River Stats Comprise only 0.006% of total freshwater cm to km in scale Longest river system Nile River (Africa) = 6853 km Largest discharge Amazon (South America) = 219,000 m3/s Largest drainage Amazon (South America) = 7,050,000 km2 Characterization of Streams Drainage Area Land area drained by all tributary systems above a chosen point on main channel AKA Catchment Watershed Nested Characterization of Streams Discharge Def’n - Volume of water passing through a channel per unit time Usually positively related to drainage area also affected by climate and geology Characterization of Streams Stream Order Measure of classifying a streams position in the network 1st order is smallest permanent stream Related to - drainage area, width, discharge Strahler Order Problems with stream order Hard to identify 1st order stream not always related to stream properties Characterization of Streams Rivers Network have variable patterns Patterns generated by land forms E.g., Rectangular = transform faults E.g., Trellis = parallel ridgelines Characterization of Streams Hydrograph Continuous record of discharge plotted against time Shape of hydrograph depends on soils and rain event Biome specific Impacted by land use Surface versus Groundwater Pathways 3 major pathways rain and meltwater can reach stream Overland Flow Subsurface Flow Groundwater Depends on: Gradient Soils Antecedent moisture Height of water table Characterization of Streams Flow permanence Perennial, Intermittent, Ephemeral PERENNIAL Perennial - flow at all times except during most severe drought and receive groundwater all the time Intermittent - flow some of the time and receive some groundwater (seasonal) Ephemeral – flow rarely (storm INTERMITTENT events) and receive no groundwater Stream Characterization Effect of Flow Regulation Dampens amplitude of peaks and troughs Impacts stream organisms The Stream Channel Cross-section shape determined by Discharge and sediment Also: vegetation, erodability of bed and banks, barriers Shape and area varies within reach Discharge the same at all cross- sections The Stream Channel Pool-Riffle Features Regular pattern of shallow faster moving areas alternating with deeper slower moving areas Higher slope in riffles Found in moderate to low gradient, unconfined, gravel bed streams The Stream Channel Meanders S-shaped pattern that streams tend to form Unless confined or braided Caused by alternating areas of erosion and deposition associated with changes in velocity The Stream Channel Other channel forms Braided - high slopes and noncohesive sediments Confined – unerodable sediments The Floodplain Level area near the channel that is flooded during moderate flow Constructed from materials deposited by the river during over bank flows and by meandering Most developed in lowland rivers – restricted in confined rivers Movement of Material by Streams Bed Material Control of channel form Grain size Determined by sources, abrasion and sorting Measured using “pebble counts” or sieving Composition determines materials available for transport – coarser at bed surface Bank and Bed Erosion Erosion is process of adjustment towards equilibrium imposed by stream conditions Erosion of banks key source of sediment Natural process  meanders Caused by progressive erosion of “toe” of bank Steepening banks eventually fail Failed sediments transported downstream Vegetation and soil cohesion resist erosion Grass more effective than trees Most bank erosion occurs during high flows Bank and Bed Erosion Bed material transport occurs when discharge is sufficient to move particles Erosion dependent on bed shear stress Threshold of movement called critical shear stress Small non-cohesive particles easiest to move Sediment Load Amount of sediment passing a point over some time interval Sediment concentration x water discharge Three components Dissolved Suspended Bed } Washload Dissolved Load Materials dissolved in water – will not “fall out” even if water stops flowing Suspended Load Fine material that is suspended in water under normal flows Bed Load Larger particles that move along the bed by sliding, bouncing and rolling Bed Load Larger particles that move along the bed by sliding, bouncing and rolling Factors Influencing Sediment Concentrations and Loads Load capacity: ↑ with velocity  extreme events Effective discharge is when peak transport is reached Usually around bankfull discharge Sediment supply Varies with size of sediments Biome/land use Mini Quiz Select the following river catchment description that is most likely to have the LARGEST annual discharge. Complete on LEARN page Summary of Key Points 1. Definition: body of flowing water in a defined channel 2. River discharge function of catchment size, climate and soils/vegetation Can be permanent, ephemeral or intermittent 3. Channel form determined by discharge and sediment Maintained and altered by sediment erosion and transport 4. Rivers transport sediment from headwaters to oceans Carried as dissolved, wash or bedload  depends on grain size and velocity up to this deck for term test 1 Lakes and Reservoirs: Physiography Lecture 7 What is a Lake?? Definition a very slowly flowing or nonflowing body of water in a depression and not in contact with the ocean c a n be very big very small (not defined by size - or Can be fresh or saline Can include very slow moving wide spots in rivers and small ponds Distribution of Lakes Permanent Lakes Most common in areas where there is: More precipitation/Less evaporation Geology that allows formation of water-retaining basins Intermittent Lakes Less common Occur in arid areas Lake Formation: Geological Processes plates pulling apart (rip) creates deeper holes and fills with water and secement , Tectonics Basin formed by movement of Earth’s crust Examples Graben Lakes – multiple faults allow block of crust to slip down and form a depression (Lake Baikal and Lake Malawi) Horst Lakes – block of crust tilts and leave a depression Very deep lakes Lake Formation: Geological Processes Damming Deposition of rock and debris dams a stream or river Caused by Lava flows, land slides, glacial ice, glacial retreat, beavers, and more ↓ dumpsediments off glacier Usually small lakes but not always Lake Formation: Geological Processes for m depressions due to the mass glaciers Glacial Activity Most common mechanism Formed most lakes in temperate regions Several Processes Scour ice Cirque lakes – N.A. Great Lakes Sura > - lakeS formed from Glacial Till – glaciers advancing Kettle Lakes ~ chunksoficea building Moraine lakes Cros left when ice melts + common in canada except lake eerie Lake Formation: Geological Processes Other formation processes Volcanic activities Caldera lakes > - afte r volcano errupts Karst processes Sinkhole lakes for ms a f te r limestone - Fluvial Processes Oxbow Lakes > - rivers flow c a n be n at u re around intermittent in Meteors Wind Erosion 7 m o re r a re that create lakes Lake Habitats and Morphometry most lakes have this structure Lakes can be divided into subhabitats: really small lakes Pelagic Profundal Littoral Occurrence and extent of zones dependent on size and shape of lake Lake Morphometry Measures of lake shape and size Surface area (A) Depth (z) maximum depth (zmax) mean depth (𝑧)ҧ Volume (v) Taken from a Bathymetric Map Lake Properties Retention Time Average length of time water stays in lake 𝑣 𝑅 = 𝐿 Volume divided by water loss (evaporation & outflows) Shoreline Development Irregularity of shore 𝐿 𝐷𝐿 = 2 π𝐴0 L is shore length and A0 is surface area Lake Productivity Influenced by morphometry and properties Shallow lakes usually more productive More mixing of nutrients by wind More shallow areas for plant growth Greater shoreline development more productive More interaction with landscape  more nutrients Reservoirs Human made lakes By damming rivers Shaped by topography of river valley Fill drainage basins of rivers and streams to height of dam High shoreline development index Shallow depth (usually) Productive River to Lake continuum as move from inlet to dam Velocity slows; depth and width increases Species change Sediments deposited (fill from inlet to dam) Impacts of Reservoirs Outflow of water is usually Sediment outputs to oceans has highly managed decreased Alters downstream flow Reservoirs capture large amounts Large fluctuations in water levels of sediments in reservoirs common Reduced global output despite Impact littoral communities increased erosion and sediment loads to rivers Fills reservoirs Impacts deltas and estuaries  temp and salinity Stratification causes stratification Formation of distinct layers of water in a lake Caused by density differences Usually associated with temperature Three layers Epilimnion Metalimnion Hypolimnion Thermocline Several types of Stratification Varies with climate Types of Stratification Monomictic Stratification occurs once a year summer Common in warm temperate and subtropical lakes No freezing in winter Types of Stratification Dimictic Stratification occurs twice a year summer and winter Common in cold temperate lakes Freeze in winter Types of Stratification Others Amictic (a.k.a Meromictic) Always stratified Occur in tropics or polar regions Polymictic Stratify several times a year Occur in Tropics Stratification can also occur because of salinity gradients Effects of Stratification Low oxygen in hypolimnion Release of nutrients from benthic sediments Lack of exchange of nutrients between zones Cold water taxa restricted to hypolimnion Water Movement and Currents Wind is main cause of waves in lakes Waves cause mixing and shore erosion Wave height determined by strength of wind and lake fetch Wind strength – speed and duration Lake fetch is distance of lake wind moves over Wave Types Small Scale Waves Rotation movement of water in place Langmuir cells Alternating zones of upwelling and downwelling Wave Types Large Scale waves Seiche Waves Mini Quiz Select the respective phrases that best complete the statement below. Stratification is the formation of _____________ and occurs when __________. Complete on LEARN page Summary of Key Points 1. Lakes are slow to non-flowing water bodies in depressions Formed by geological processes Mass movements, plate tectonics and glaciers most common 2. Reservoirs are managed lakes formed by damming a river 3. Lake stratification Formation of thermally distinct layers in a lake Classified based on number of times in a year a lake stratifies Influences oxygen and nutrient availability in lake 4. Wind is main cause for movement and mixing of water in Lakes Small scale waves and Seiche waves Types of Aquatic Organisms Lecture 8 The Species Concept Species – fundamental unit of taxonomic division “Defining” criteria 1. genetically distinctive group of populations 2. members are able to interbreed freely under natural conditions 3. Reproductively isolated from all members of other such groups But… because of liquid environment -see m o re hybridization Many aquatic organisms (especially microbes) don’t reproduce sexually Some aquatic species can reproduce with others (i.e. form hybrids) Major Taxonomic Groups Three Major groups Eukarya, Bacteria, Archaea Most known about Eukarya PROKARYOTES But new methods are making clear diversity of Bacteria and Archaea far exceeds that in Eukarya Classification of organisms In addition to taxonomic classification can classify aquatic organisms by: 1. Function 2. Habitat > - parts o f lakes 3. Interactions > - how species relate to each other For example, Organisms can be autotrophic (self-feeding) or heterotrophic (other-feeding) Autotrophs can be photoautotophic or chemoautotrophic Heterotrophs can eat living organisms (herbivores, carnivores, parasites) or eat “dead” organisms (detrivores) Food Web Based Classifications consumers predators , etc Y primary , Can classify based on trophic position ie. what an organism eats Related to ecosystem process E.g., nutrient cycling, energy flow Often used for fish & macroinvertebrates For example, - can be broken down into Chow they eat scrappers to categorize further - eating bigger organic matter Grazers, shredders, collectors, predators Spick up small Schew but members of the same functional group on leaf organic material to consume o n e go may use different resources E.g., some shredders specialize on leaves others on wood Habitat Classifications Aquatic organisms often classified based on habitat they occupy Linked to an organisms environmental preferences For example, lotic taxa prefer flowing waters and lentic taxa prefer non-flowing waters Habitat Description Habitat Description Benthic On the bottom Pelagic In open water Lotic In flowing water Lentic In still water Emergent Emerging from the water Submergent Under the water Epiphytic On plants Epilithic On rocks Interspecific Interactions Classification based on how a species interacts with others Direct versus Indirect Direct – interactions occur between individuals of two species and involve no others E.g., minnow species predating on a insect species larvae Effect of A on B Effect B on A Interaction Type Positive Negative Exploitation - for o n e , Chunting) - fo r another Negative Negative Competition uncommon in freshwater Positive Positive Mutualism None Positive Commensalism None Negative Amensalism None None Neutralism Indirect – interaction between two species is mediated by a third E.g., presence of piscivorous fish reduces predation of minnow species on insect species larvae Mini Quiz Select the term that best completes the following statement. "An organism's trophic classification is based on ____________." Password: Trophic 704651 Complete on Learn page Summary of Key Points 1. Species are fundamental taxonomic unit that are genetic distinct, free to interbreed, and reproductively isolated 2. Organisms are classified based on: 1. Trophic position – what the organism eats 2. Habitat – where the organism lives 3. Interactions – how a species interacts with others