1Habitats, resources,conditions, and niches2Winds displace ocean water off the west coast of North andSouth America, causing upwelling: cold, nutrient rich waterpulled up to replace displaced surface water.upwellingRichfisheriesCalifornia: summer winds blowfrom the north, curve west, creatingupwelling along coast, enhancingnutrient supply to phytoplankton.Winter winds blow from the south,curve east favoring downwellingalong the coast.3Rain shadows and Mediterranean climates (e.g. California): ifthe land is warmer than the ocean, moisture in marine air isnot dropped until adiabatic cooling over mountains) !summer droughtIf land cooler than ocean, moisture is dropped ! winter rainsRain shadowEastern Sierra4Rain shadowEastern SierraWater ends up in lakes, rivers, or ground water…Rain forest Alpine lakes Desert5Lakes that experience seasonal freezing…6Seasonal mixing regimes: water is densest at 4oC ! winterand summer stratification, spring and fall overturn.Thermocline = stratum of rapid temperature change. Canseparate oxygenated from hypoxic habitat.Mixingreplenishesnutrientsfor algae inphotic zone7Eutrophic (river, lake estuary): nutrient rich, likely toproduce noxious or harmful algal blooms (cyanobacteria, toxicdinoflagellates)Mesotrophic – intermediate nutrient concentrationsOligotrophic – low nutrient concentrations, very clear water(“good” water quality for humans and fish)Easier for wind tostir nutrients inshallow basin,making such lakesvulnerable toeutrophicationDavid Schindler’s experimental lakes8River networks• Downstream (concentrative)fluxes of water, sediment, solutes,detritus, and passive organisms• Upstream and upslope (dispersive)backflows of mobile organisms• Systematic downstream increasesin discharge, channel width, solarradiation. Sediment sizedecreases, and disturbance frombed scour is more frequent• Confluence nodes– pulses of enrichment– adjacency of contrastinghabitats (refuges)910Terrestrialdetrital carbon,e.g. dead leavesthat fall intostreamsAttachedalgaeFine particulatedetritus* andphytoplanktonDetritus = dead organic matterEnergy(carbon)sources changedownstream11Cover down drainage networks• Headwaters:– woody debris– forest cover• Meandering middle reaches– clean gravel beds; hyporheic(under the stream bed)habitat– undercut rooted bankvegetation– off river habitat• Lowland floodplain rivers– floodplain marshes or forests– off channel water bodiesA < 5 km212Estuary: whererivers empty intooceans, fresh water(0 % salt) meetssalt water (3 %salt): tidal prismswith heavier saltywater underneathImportant nurseries foroffshore fisheriesTidal prism—wedge offresh water overlies densersalt water13Vertical and onshore-offshorezonation14Intertidal vertical zonationAbiotic stressBioticinteractions15Neritic: nearshore subtidalBenthos: life on substrate orbed of sea, lake, spring, orrivers and streamsPlankton: passive driftersNekton: active swimmerszooplanktonphytoplanktonBenthic infauna16PelagicOffshore, beyondContinental ShelfStructure? Cover? Food?Bill Hamner17Resources, conditions, andResources, conditions, andthe fundamental nichethe fundamental niche• What determines the distribution andabundance of species?– In part, their tolerance of conditions,and their need for certain resources*condition: abiotic environmental factor thatvaries in space and time and affects theperformance of organism**resource: all things consumed (used up) byorganisms (space, nutrients, water, prey, holesfor refuge, etc)18How do conditionsHow do conditionsand resourcesand resourcesinfluence theinfluence thedistribution anddistribution andabundance ofabundance oforganisms?organisms?19Macan’s filter (similar to Fig. 50.6, Campbell):If a species is absent from a habitat, is it because of:1. DispersalYes: hasn’t arrived yet (barriers, insufficient time)No: propagules* have arrived, but don’t persist*propagule: a dispersing unit capable ofestablishing a new population (e.g., one asexualspore, Adam and Eve, a pregnant female fish,or a fragment of a plant that can reproducevegetatively)2. BehaviorYes: colonists avoid habitatNo: colonists select habitat, but don’t persist20Macan’s filter, continued3. Abiotic factors?Yes: temperature, salinity, pH, moisture conditions*etc. are outside the range that the species cantolerateNo: abiotic conditions are tolerable.4. Biotic interactions?Yes: species is excluded by predators, pathogens,competitors, or the lack of prey resources** ormutualistsNo: ?2122Example: Africanized bees may havebeen selected in tropics to withstand oravoid predation by army ants--aggressive defensive stinging--bees disperse at small colony sizeEuropean bees shiver to warm hives duringwinter. Will small colony size limit thenorthward spread of Africanized bees?(Don’t build up large enough colonies towarm hive by collective shivering.)23Performance is generally nonlinear across a range of intensities of anabiotic condition: some is good, more is better, even more is very bad …Condition (e.g., temperature)coldhotPerformance ofspeciesReproductionGrowthSurvivalssggr r24A resource can become a condition at highor low levels, e.g., light. Water.Distributions of organisms determined by co-occurrence of a number of critical (potentiallylimiting) resources and conditions:PhosphorusNitrogengrowsdiesNitrogenLightgrowsdiesInteractiveNon-interactive25••Niche: Range of conditions, resource levels, andNiche: Range of conditions, resource levels, anddensities of other species within which andensities of other species within which anorganism or species can survive and reproduceorganism or species can survive and reproduce(persist over time). (An N-dimensional(persist over time). (An N-dimensionalhypervolumehypervolume, if each condition, resource, or, if each condition, resource, orother species seen as a dimension (Hutchinson))other species seen as a dimension (Hutchinson))––Fundamental Niche: the largest niche in which aFundamental Niche: the largest niche in which aspecies could persist in the absence of (adverse)species could persist in the absence of (adverse)interactions with other speciesinteractions with other species––Realized Niche: the (generally smaller) nicheRealized Niche: the (generally smaller) nichevolume actually occupied by a species in thevolume actually occupied by a species in thepresence of presence of interspecific interspecific
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