Ecology 13 Ralph Kirby

All nutrients follow biogeochemical cycles Two types of cycle –Gaseous Major reservoirs are atmosphere and oceans Global in nature –Oxygen –Nitrogen –Carbon of carbon dioxide –Sedimentary Major reservoirs are soil rock and minerals Rock and salt solution phases Salt solution is the available form –Phosphorus –Metals, eg Calcium, Magnesium, etc Some cycles are hybrid –Sulphur Nutrients enter the ecosystem via inputs –Gaseous cycle from atmosphere –Sedimentary from rocks and minerals Nutrients are recycled within the ecosystem –Internal recycling important within ecosystem –Some systems have large amount of short term recycling Lakes –Other have most stored as biomass Forests –Long term storage in water systems is in the sediment System dependent on primary production and decomposition –Without latter, everything will become locked up

Each ecosystem varies in balance of primary production and decomposition There is feedback between the two High primary production –High level of nutrients in leaves –High return to litter –High mineralization –High nutrient availability Low primary production –Converse Thus climate, plants, etc affect nutrient recycling

There are also outputs to the biogeochemical cycles –Carbon to carbon dioxide –Nitrogen to ammonia –Loss of organic matter from ecosystem by washout –Herbivores between aquatic and terrestrial MooseHippopotamus

See effect of logging in above two systems Primary production and decomposition are usually in two separate zone –Can be linked in terrestrial systems –Usually not linked in aquatic systems Note that all ecosystems such alink

Link for terrestrial systems –Plants bridge systems and move minerals Link for aquatic systems –Shallow Plants –Deep Physical separation Need for a transport system

Static deep water forms three layers –Surface warm oxygen rich layer –Deep cold oxygen poor layer –Narrow transition zone or thermocline Mixing from weather does not affect hypolimnion However in winter, thermocline disappears Mixing vertically –Thus winter replenishes the Epilimnion’s nutrients –While summer depletes the Epilimnion’s nutrients

Seasonality those affects productivity and decomposition in open water Effect is called turnover

Flowing systems are different –Inputs from terrestial systems are significant Leaves, seepage, etc –Spiralling Varies with speed of water Varies with biological system holding nutrients –Retention of detritus can results in tighter spiral –Woodland stream P moves 10.4 m/d P cycles once every 18.4 d One spiral was 190 m

Where terrestrial and open water system join –Influenced by both systems Meeting of fresh and salt water –Creates nutrient trap –Limits release of nutrients into sea Coastal areas –Upwelling Equatorial –Coriolis force causes by counter currents at equator –Upwelling between Coastal –Coriiolis force wind causes offshore currents and upwelling at continental edge

Carbon Cycle Tightly linked to energy flow Thus different between production and loss –Net ecosystem productivity Varies daily Varies seasonally Note storage –Carbonates Coral reefs Limestone –Coal –Oil –Gas –Peat

Note temporal cycles –Daily –Annually Involvement –Land –Sea –Air Most general Note size of pools Note size of fluxes

Nitrogen cycle Nitrogen is essental to life Starts with nitrogen fixation from atmosphere Plants can only utilize nitrate or ammonia –Atmospheric deposit –Nitrogen fixation High energy Biological –Bacteria –Nitrification –Bacteria –Denitrification –Bacteria –Loss by washout

Phosphorus cycle

No atmospheric reservoir Permanent loss of phosphorus to oceans Input limited to weathering of rocks Terrestrial systems can be limited by phosphorus availability Phosphorus is more abundant in marine and freshwater systems –Particular –Dissolved organic phosphorus Rapidly utilized by zooplankton\ Secrete inorganic –Dissolved inorganic phosphorus Rapidly utilized by phytoplankton Phosphorus can sink as particulate phosphorus and become locked in botomn sediment –Depletion of surface layers

Sulphur cycle

Gaseous and Sedimentary Poorly understood

Oxygen cycle Created by biology Under biological control Inputs –Breakup of water –Photosynthesis –Now in balance –Not always Many other forms –Carbonates –Nitrates –Sulphates –Oxides Thus all cycles are linked –Chemically –Energetically –Biologically

Humans have changed and are changing the biogeochemical cycles Carbon –Burning of fossil fuels –Clearing of forests –Greenhouse effect Nitrogen –Agriculture Clearing of forests Fertilizers –Industry –Motor cars –Increased nitrogen in nitrogen poor areas Algal blooms Sulphur –Natural 60% –Human 40% Fossil fuels

Acid rain from excess depositing of sulphur and nitrogen as acids Some systems are more acid sensitive than others Reduction in available phosphorus Reduction in nitrogen fixation

New cycles established for xenobiotics Effect on ozone layer of chlorohydrocarbons –Increased skin cancer Effect on bird reproduction of DDT –Loss of birds of prey Effect on shellfish consumption of heavy metals –Mercury poisoning in Japan Effect on human reproduction of non-ionic detergents (Triton) –Form compounds similar to human reproductive hormones on breakdown