2 Physical Environment Flashcards
water cycles (earth and atmosphere)
- water/ hydrologic cycle is a process where water travels in a sequence from the air to earth and returns to atmosphere
- driving force: solar radiation that provides energy for the water-evaporation
hydrologic cycle
total water volume
1.4 * 10^6 cubic-kilometer
physical properties of water: basic structure
- covalent bonding of 2H + O atoms
- polar-covalent bond
- inter-molecule attraction
- H-bonds among water moleculars
- can be solid, liquid or gas
physical properties of water: specific heat
- also calles Heat Capacity
- 1 calorie is required to raise the temperature of 1g H2O by 1°C
effects:
- mitigated seasonal temperature fluctuations
- thermal regulation of organisms
physical properties of water: latent heat
- energy that is released or absorbed in the transformation of water from one state to another (e.g. from water to solid ice)
- 536 calories needed to change 100°C water to vapor
- 86 calories needed for ice to melt to 1°C water
effects:
- mitigated seasonal temperature fluctuations
- thermal regulation of organisms
physical properties of water: peculiar density-temperature relationship
- if T > 4°C: water density increases when temperature decreases
vice versa: decreasing water temperatures –> increasing density
but: - if T < 4°C > 0°C : water density decreases when water freezes (from highest density to lowest)
–> low density on surface (warm water)
–>lower density (ice) on top –> isolation that prevents underlying water from freezing
physical properties of water: Cohesion
- due to hydrogen bonding
- water molecules stick firmly to each other
- can resist external forces
–> surface tension
–> viscosity
–> buoyancy
–> high pressure changes with depth
classification of aquatic systems based on ____ ?
- depth (light, temp., density, oxygen)
- salinity
- still water or moving water
marine divisions in biozones and light zones
light gradient
(vertical gradient)
- effects on vertical temperature profile
- quantity and quality of light vary with depth of water
- effects on quantity and distribution of production
- adaptations in plant organisms (different batteries of photosynthetic pigments)
- adaptations in animal organisms (adaptations in the dark)
temperature gradient
(vertical gradient)
- temp. change as result of the exponential decline in solar radiation with water depth
- vertical profile of water varies seasonally
- Fall turnover: surface water cool and dense –> sinks, displaces the water below –> creates uniform temperature
Temperature varies with latitude
map of average Sea Surface Temperature (SST)
Horizontal Gradient (SST)
Ocean Surface Temperature
- often called Sea Surface Temperature (SST)
- strong correlation with latitude because of a high isolation at low latitudes and low isolation at high latitudes
- surface ocean isotherms (= lines of equal temperature)
SST overall pattern
- highest in tropics –> highest insolation
- decreases polewards –> with decreasing insolation
- negative temperatures in Arctic Ocean and around Antarctica
surface ocean isotherms
= lines of equal temperature
- have a general east-west trend
but
- they can be deflected by currents towards equator or poles
- warm water carried poleward on western side of ocean basins (Ozeanbecken)
- cooler water carried equatoward on eastern side of ocean basin
Chemical composition of water
- excellent solvent
- salinity measured in psu (Practical Salinity Units)
Horizontal gradients of water
- salinity
- density
- temperature
Global map of average sea surface salinity (SSS)
Horizontal gradient (SSS)
what determins water density? What is the [SI]?
density = mass/volume (g/m3, g/ml, kg/l)
determined by:
- Temperatur
- salinity
- pressure
relationship density + temperature
- inverse relationship
- lower temperature –> higher density
relationship density + salinity
- direct
- lower salinity –> lower density
relationship density + pressure
- at very high pressures (deep seas) pressure increases density
- sea level would be around 30-50m higher without pressure effect
Vertical gradient: salinity (density+temp)
- lower salinity water with less density will lie over higher salinity water of the same temperature
- as depth increases, salinity stays fairly constant (at just under 35 ppt)
- Salinity more variable on surface (rain e.g.)
Salinity gradients in transitional environments (estuaries)
- meeting of fresh and salt water
- not static: can vary a lot (e.g. on season)
Classification of aquatic environments based on salinity
-Hyperhaline very high salinity >40ppt
- Metahaline ranges from 36 to 40 ppt
- Euhaline between 30 and 35 ppt. The most in marine and oceanic waters!
- Polyhaline from 18 to 30 ppt
- Mesohaline between 5and 18 ppt
- Oligohaline between 0.5 to 5 ppt
- Freshwater <0.5 ppt
dissolving nutrients in the water originate from ___?
- rivers and water runoff
- decompositions of organic matter (mostly at sea bottom)
Effectsof depth on the dynamics of nutrients in the ocean
- different dynamics due to the depths
- more light at the surface, less in depths
- composition of the bottom in deep areas, where nutrients are needed
- upwelling areas
- cold water: full of nutrients from bottom
- water circulates and nutrients are more available
- in lakes you can have two areas that are almost separate bec. Of missing circulation
Vertical gradients
- Light: quick decrease and then dark areas
- temp.: same as light, more or less constant decrease
- nutrient limitation: more abundant in depth
- DCM (Chl. A) has a max productivity NOT on surface but a bit lower (ca. 100m depth) –> light still efficient and abundance of nutrients higher
Gas solubility
influenced by
1) temperature
2) salinity
3) pressure
relationship gas solubility + temperature
gas solubility decreases with increasing temperature
relationship gas solubility + salinity
gas solubility decreases when salinity increases
–> gas solubility increases with decreasing salinity
–> better solubility in fresh water (at the same temperature)
relationship gas solubility + pressure
- direct releationship
- when atmospheric pressure increases –> gas solubility increases
Oxygen concentration in aquatic environment
- oxygen dissolved in water
- it’s concentration is determined by solubility and diffusion
-follows more or less the temperature
- differs in seasons:
1) Static in fall due to fall turnover (temperature uniform)
2) winter:
- high oxygen concentration on surface due to diffusion
- decline in depth due to demand and uptake by decomposer organisms on bottom zone
3) summer: decline in depth due to demand and uptake by decomposer organisms on bottom zone
Vertical profile of oxygen in the Atlantic Ocean
- oxygen concentration declines to a minimum in the zone of 500-1000m depth
-then: O2 concentration increases to max. and stays more or less constant
-increase caused by influx of O2 rich cold water that sank in the polar water
Anoxia
- condition of no, or at times very little, dissolved oxygen in marine or freshwater systems
- has drastic consequences to normal ecosystem functioning including biogeochemical cycling
Hypoxia
- condition of low dissolved oxygen concentrations in marine or freshwater systems
- has adverse (neg.) consequences to normal ecosystem functioning including biogeochemical cycling that range from mild to severe disruption
Dead zone
area of hypoxia or anoxia that is related to anthropogenic activity
anoxic zones
- Certain depth can become anoxic
- Typical for lagoons/ estuaries
(- e.g. Black sea always in anoxic state)
Why are anoxic zones increasing?
- Eutrophication
(= Anreicherung von Nährstoffen in einem Ökosystem oder einem Teil desselben bezeichnet. Im engeren Sinne ist meist die durch den Menschen bedingte (anthropogene) Erhöhung des Nährstoffgehalts von Gewässern durch gelöste Nährstoffe) - warming waters due to climate change
effects of warming waters
- increasing stratification of ocean –> weakens the overturning circulation of the water
- decreases oxygen solubility
- warm waters combined with excess nutrients from land causes a harmful algal blooms
- algal blooms drain (zersetzen) oxygen as they die and decompose
Carbon dissolves in water. how?
CO2 + H2O <-> H2CO3 <-> HCO3(-) + H+ <-> CO3(2-) + 2H+
Carbondioxide + Water <-> Carbonic acid <-> Bicarbonate + H+ <-> Carbonate + 2H+
CO2 in relation to pH
- distilled water: pH=7 (neutral)
- sea water: pH= 7,5 - 8,4 (slightly alkaline)
- carbonated water: pH= 3,6 (acidic)
- CO2 additions or losses affect the pH
- changes in pH determine the prevailing form of CO2
-the more CO2 dissolves, the more H+ gets free –> acidification
- trend of pH: downwards –> less CaCO3 which shells and corals are made of
Panta rei - Water movements (due to?)
water movements due to
- waves
- curerents
- tides
what are the direct or indirect effects of water movements?
- size and shape of organisms
- movement, dispersal, recruitment
- nutrients, oxygen, food availability
- habitat characteristics (e.g. sediment size)
horizontal wave gradient: Refraction
- the change in direction of a wave passing from one medium to another
- refraction happens when waves travel from deeper parts of the ocean to the shallower coastlines.
-focus on rocky peaks
-on shore the sides are less wavy
horizontal wave gradient: Diffraction
- a sudden change in the direction and intensity of waves after passing by a coastal feature or offshore obstruction
- obstacle blocks a portion of the wave’s energy, forcing it to spread into the sheltered area behind the obstruction
-interaction of the rock with the front of the waves
vertical wave gradient
- offshore: wave-interaction with the bottom
Destructive Wave
- coastal erosion takes place
- destructive waves are very high in energy and are most powerful in stormy conditions
- swash, when a wave washes up onto the shoreline (here: weak)
- backwash, when the water from a wave retreats back into the sea (here: very strong)
- strong backwash pulls material away from the shoreline and into the sea resulting in erosion
Constructive Wave
- low energy waves
- result in the build-up of material on the shoreline
- stronger swashes than backwashes –> any material being carried by the sea is washed up and begins to build up along the coastline
- material that is deposited by constructive waves can most often be seen by the creation of beaches.
hydrodynamic forces of waves
- horizontal: the drag force in the direction of the wave impact the inertial force of region
- vertical: a lifting force from bottom to top
–> organisms experience lift and drag as a result of how their shapes interact with fluid flow
–> organisms as seaweed or crabs adopted to some of the forces
water movements
(coriolis force)
- equatorial upwelling
- coastal upwelling
Oceanic Currents
upwelling areas
- have high nutrients and productivity
- many western sides have upwelling areas
tides
= periodic motion of large masses of water that
-rises (flow, high tide)
and
lowers (ebb, low tide)
combination of factors regulating tides
1) gravitational attraction that is exerted (ausgeübt) from other bodies of solar system (mainly moon and sun) on the earth
2) centrifugal force, due to rotation of Earth-Moon system around it’s center of mass
what Is the greatest tide?
spring tide
tidal cycles
three basic tidal patterns
1) semidiurnal
- two high + two low tides each day
- about same height
2) mixed semidiurnal
- two high + two low tides each day
- differ in height
3) diurnal
- only one high and one low tide each day
tidal ranges
- macrotidal > 4m (up to 7m)
- 2m < mesotidal < 4m
- microtidal < 2m
influence of environmental conditions (tides)
- especially in micro tidal environments
- weather conditions can make a huge difference in certain areas
- influence by e.g. spring tides and winds from south eastern, or pressure
Challenges from physical factors on marine organisms
- the tidal circulation can force organisms to move
- together with other components (picture), ecological environments are formed
