Measuring abiotic components  Objectives  To make an exhaustive list of abiotic factors  To discuss the ways they are measured  To critically appraise the methods.

Abiotic components  TemperaturepH  HumidityNutrient availability  Oxygen concentrationSoil depth  Salinitydisturbance  Light exposure/turbiditypollution  Wind exposureflow velocity  Wave actionslope gradient  Sand blastingparticle size  drainage

Marine habitats  Very stable except for inter tidal  Intertidal habitats often experience extremes of change  Key factors:  Temp  pH  Dissolved oxygen  Salinity  Wave action  Turbidity

Oceanic temperatures

Temp  Measured with a thermometer or temperature probe  Temperature falls with depth  Influence of ocean currents greater than that of surface heating  Annual fluctuations greater in shallow  seas  Dramatic fluctuations in intertidal  habitats

salinity  Salinity measured by conductivity meter  pH very constant  Salinity constant over huge areas  Lower in polar areas due to melt waters  Lower in coastal areas where river waters empty into sea – freshwater may float on salt  Estuaries have salt wedge  Some seas have low salinity, e.g. Baltic  Some more saline due to evaporation e.g. Mediterranean.

Map of salinities

diagram of salt wedge

Dissolved oxygen  Measured oxygen sensitive electrodes or through Winkler titration  Highest near surface  Higher in day than at night due to input of photosynthesis  Falls in deeper waters  Cold currents from meltwater may be richer in oxygen

pH and nutrient concentration  pH measured by pH meter or data logging probe.  Nutrient concentration measured through chemical analysis  Varies  Low in open ocean  Higher in shallow seas, coastal areas and in upwellings of cold water.  Varies through year in temperate waters due to algal blooms.

Wave action  Measured by dynamometer  Result of prevailing winds  Impact affected by coastal morphology  Vary according to weather conditions  Affected by size of water body  Erosive powers amplified by material that the waves can carry

Turbidity  Measured with a secchi disc  High in nutrient rich coastal waters  Low in nutrient poor oceanic waters  Maximum depth of light penetration in oceans may be 100m  May be only a few cm in sandy shallow coastal areas such as the Gulf Coast  Varies in temperate regions due to algal blooms.

Changes in depth

FRESHWATER HABITATS  Temperature  pH  Dissolved oxygen  Turbidity  Conductivity/nutrients  Flow velocity

Temperature  Closely related to climate in rivers and lakes  Cooled by upstream waters  More stable in ground water fed rivers  Most lakes are stratified especially in summer/warm conditions  Impact of air temperature and sun related to volume and flow  Higher in slow rivers.

Lake stratification explained

pH  Dependent on underlying bedrock  Affected by soil  Varies daily and yearly due to impact of photosynthesis  Affects nutrient availability  Affects decomposition of organic matter  May be different at different levels in lake waters when the lake is stratified.

Dissolved oxygen  Higher in fast flowing rivers  Higher in colder water  Lower in slow flowing rivers and warmer waters  Decreases from surface in lakes  Stratified  Varies seasonally and daily due to impact of photosynthesis.

Turbidity  Poor in shallow disturbed waters  Poor in waters rich in humic acid  Better in nutrient poor lakes  Affected by water chemistry  Affected by mixing  Affected by algal blooms  Affected by animal action  Affected by sediment load

Conductivity/nutrients  Affected by bed rock and drift  Affected by depth of lake and stratification  Affected by plankton blooms  Affected by sediment load

Flow velocity  Affected by gradient  Affected by weather factors such as rainfall and snow melt  Varies dependent on position of channel  Laminar flow – flow near surface of rocks and river bed much less than in mid-water due to impact of friction.  Varies with season  Variation less in groundwater fed rivers than surface water fed  Varies with bed morphology – riffle pool.

Flow types  Upland fast flowing  Lowland slow flowing Riffle pool flows

Terrestrial factors  Temperaturehumidity  Soil pH  Light intensity  Wind speed  Particle size of soil  Slope  Soil moisture  Mineral content of soil  drainage

Temperature  Measured with a thermometer or a maximum minimum thermometer  Dependent on season, latitude, altitude  Dependent on exposure/shelter  Dependent on light intensity  Reduces with increased altitude and latitude  Varies daily

Humidity  % humidity measured with humidity sensors  Varies geographically. Low in deserts, higher in forests and near coasts and lakes  Varies with temperature – hot air can contain more water vapour  Varies daily, seasonally, with weather patterns  Varies with exposure  Is a very important factor limiting the distribution of many flora and fauna.

Soil  pH, drainage, nutrient concentrations and particle size are all linked  Soil comprises the mineral abiotic and organic biotic matter.  Particle composition affects drainage which affects soil moisture which in turn interacts with soil mineral composition to determine pH which affect nutrient availability. Underlying bedrock may strongly influence all these factors.  Soil analysis can include particle analysis dry and wet weight calculations and burning of organic matter plus chemical analysis.

Exposure and shelter  These affect  Light intensity and shade  Humidity  Wind speed and exposure to wind borne particles  Also affected by orientation. i.e. direction of slope  Slope or gradient affects drainage and light intensity