THE NUTRIENT CYCLES AND HUMAN IMPACT THE CYCLING

THE NUTRIENT CYCLES AND HUMAN IMPACT

THE CYCLING OF CHEMICAL ELEMENTS IN ECOSYSTEMS BIOGEOCHEMICAL CYCLES KEY PLAYERS DECOMPOSERS – COMPLETE CYCLE TYPES OF BIOGEOCHEMICAL CYCLES: GLOBAL – ATMOSPHERE AND OCEAN REGIONAL – STUFF FOUND IN THE SOIL NUTRIENT RESEVOIRS: PAGE 1195

Reservoir a Reservoir b Organic materials available as nutrients Organic materials unavailable as nutrients Fossilization Living organisms, detritus Coal, oil, peat Respiration, decomposition, excretion Assimilation, photosynthesis Burning of fossil fuels Reservoir c Reservoir d Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Atmosphere, soil, water Weathering, erosion Formation of sedimentary rock Minerals in rocks

THE WATER CYCLE RESERVOIRS • THE OCEANS CONTAIN 97% OF THE WATER IN THE BIOSPHERE. • 2% IS BOUND AS ICE, AND 1% IS IN LAKES, RIVERS, AND GROUNDWATER. • A NEGLIGIBLE AMOUNT IS IN THE ATMOSPHERE. KEY PROCESSES • EVAPOTRANSPIRATION, CONDENSATION, PRECIPITATION

THE CARBON CYCLE - BASE OF BIOLOGICAL MOLECULES RESERVOIRS • THE MAJOR RESERVOIRS OF CARBON INCLUDE FOSSIL FUELS, SOILS, AQUATIC SEDIMENTS, THE OCEANS, PLANT AND ANIMAL BIOMASS, AND THE ATMOSPHERE (CO 2). KEY PROCESSES • PHOTOSYNTHESIS BY PLANTS AND PHYTOPLANKTON FIXES ATMOSPHERIC CO 2. • CO 2 IS ADDED TO THE ATMOSPHERE BY CELLULAR RESPIRATION OF PRODUCERS, CONSUMERS AND DECOMPOSERS. • VOLCANOES AND THE BURNING OF FOSSIL FUELS ADD CO 2 TO THE ATMOSPHERE.

THE CARBON CYCLE THE WATER CYCLE CO 2 in atmosphere Transport over land Photosynthesis Solar energy Cellular respiration Net movement of water vapor by wind Precipitation over ocean Evaporation from ocean Precipitation over land Burning of fossil fuels and wood Evapotranspiration from land Percolation through soil Runoff and groundwater Figure 54. 17 Carbon compounds in water Higher-level Primary consumers Detritus Decomposition

THE NITROGEN CYCLE • NITROGEN IS A COMPONENT OF AMINO ACIDS, PROTEINS, AND NUCLEIC ACIDS. BIOLOGICALLY AVAILABLE FORMS • PLANTS AND ALGAE CAN USE AMMONIUM (NH 4+) OR NITRATE (NO 3−). • VARIOUS BACTERIA CAN ALSO USE NH 4+, NO 3−, OR NO 2 -. • ANIMALS CAN USE ONLY ORGANIC FORMS OF NITROGEN (AMINO ACIDS)

RESERVOIRS • THE MAJOR RESERVOIR OF NITROGEN IS THE ATMOSPHERE, WHICH IS 70 -80% NITROGEN GAS (N 2). • SOILS AND THE SEDIMENTS OF LAKES, RIVERS, AND OCEANS. • DISSOLVED IN SURFACE WATER AND GROUNDWATER. • NITROGEN IS STORED IN LIVING BIOMASS.

KEY PROCESSES • NITROGEN ENTERS ECOSYSTEMS PRIMARILY THROUGH BACTERIAL NITROGEN FIXATION. • SOME NITROGEN IS FIXED BY LIGHTNING AND INDUSTRIAL FERTILIZER PRODUCTION (HABER PROCESS) • AMMONIFICATION BY BACTERIA FORMS NH 4+ • IN NITRIFICATION, BACTERIA CONVERT NH 4+ TO NO 3−. • IN DENITRIFICATION, BACTERIA USE NO 3− FOR METABOLISM INSTEAD OF O 2, RELEASING N 2. - IMPORTANT SYMBIOSIS: LEGUMES AND NITRIFYING BACTERIA

THE PHOSPHORUS CYCLE THE NITROGEN CYCLE N 2 in atmosphere Rain Geologic uplift Runoff Assimilation NO 3 Nitrogen-fixing bacteria in root nodules of legumes Decomposers NH 3 Nitrogen-fixing soil bacteria Figure 54. 17 Denitrifying bacteria Nitrification Ammonification Plants Weathering of rocks Consumption Sedimentation Soil Plant uptake of PO 43 Leaching NO 2 NH 4+ Nitrifying bacteria Decomposition

PHOSPHORUS CYCLE • PART OF NUCLEIC ACIDS, PHOSPHOLIPIDS, AND ATP • BONES AND TEETH. BIOLOGICALLY AVAILABLE FORMS • PHOSPHATE (PO 43−), PLANTS ABSORB AND USE TO SYNTHESIZE ORGANIC COMPOUNDS. RESERVOIRS • SEDIMENTARY ROCKS OF MARINE ORIGIN. • SOILS, DISSOLVED IN THE OCEANS, AND IN ORGANISMS. KEY PROCESSES • WEATHERING OF ROCKS GRADUALLY ADDS PHOSPHATE TO SOIL. • ABSORBED BY PRODUCERS AND INCORPORATED INTO ORGANIC MATERIAL. • IT IS RETURNED TO SOIL OR WATER THROUGH DECOMPOSITION OF BIOMASS OR EXCRETION BY CONSUMERS.

THE PHOSPHORUS CYCLE THE NITROGEN CYCLE N 2 in atmosphere Rain Geologic uplift Runoff Assimilation NO 3 Nitrogen-fixing bacteria in root nodules of legumes Decomposers NH 3 Nitrogen-fixing soil bacteria Figure 54. 17 Denitrifying bacteria Nitrification Ammonification Plants Weathering of rocks Consumption Sedimentation Soil Plant uptake of PO 43 Leaching NO 2 NH 4+ Nitrifying bacteria Decomposition

3. DECOMPOSITION RATES LARGELY DETERMINE THE RATES OF NUTRIENT CYCLING. • DECOMPOSITION TAKES AN AVERAGE OF FOUR TO SIX YEARS IN TEMPERATE FORESTS, WHILE IN A TROPICAL RAIN FOREST, MOST ORGANIC MATERIAL DECOMPOSES IN A FEW MONTHS TO A FEW YEARS. • THE DIFFERENCE IS LARGELY THE RESULT OF WARMER TEMPERATURES AND MORE ABUNDANT PRECIPITATION IN TROPICAL RAIN FORESTS. • THE RATE OF DECOMPOSITION INCREASES WITH ACTUAL EVAPOTRANSPIRATION – WET AND WARM

Consumers Producers Decomposers Nutrients available to producers Abiotic reservoir Figure 54. 18 Geologic processes

HUMAN IMPACT ON ECOSYSTEMS AND THE BIOSPHERE THE HUMAN POPULATION MOVES NUTRIENTS FROM ONE PART OF THE BIOSPHERE TO ANOTHER. HUMAN ACTIVITY INTRUDES IN NUTRIENT CYCLES. 1) REMOVE NUTRIENTS IN THE FORM OF BIOMASS: CROPS, LUMBER - CAN EXHAUST THE NUTRIENTS OF A SYSTEM 2) INTRODUCE EXCESS NUTRIENTS: FERTILIZERS AND SEWAGE - EXCESS NITRATES IN AIR ATMOSPHERIC PROBLEMS (OZONE DEPELETION, GLOBAL WARMING, ACID DEPOSITION) - EXCESS NITRATES IN WATER EUTROPHICATION OF WATER WAYS, FISH KILLS , TAINTED GROUND WATER, METHEMOGLOBINEMIA 3) EXCESS CONSUMERS: LIVESTOCK – DEPLETES STANDING BIOCROPS 4) INCREASE CO 2 , NITRATE AND SULFUR OUTPUT – FOSSIL FUELS

ACID PRECIPITATION: • THE BURNING OF FOSSIL FUELS RELEASES OXIDES OF SULFUR AND NITROGEN THAT REACT WITH WATER IN THE ATMOSPHERE TO PRODUCE SULFURIC AND NITRIC ACIDS AND RETURN AS RAIN, SNOW, SLEET OR FOG WITH A PH LESS THAN 5. 6. • ACID PRECIPITATION IS A REGIONAL OR GLOBAL PROBLEM, RATHER THAN A LOCAL ONE. • ACID PRECIPITATION LOWERS THE PH OF SOIL AND WATER AND AFFECTS THE SOIL CHEMISTRY OF TERRESTRIAL ECOSYSTEMS. • WITH DECREASED PH, CALCIUM AND OTHER NUTRIENTS LEACH FROM THE SOIL. • THE RESULTING NUTRIENT DEFICIENCIES AFFECT THE HEALTH OF PLANTS AND LIMIT THEIR GROWTH. • FRESHWATER ECOSYSTEMS ARE VERY SENSITIVE TO ACID PRECIPITATION – AFFECTS SPECIES DIRECTLY

Field p. H 5. 3 5. 2– 5. 3 5. 1– 5. 2 5. 0– 5. 1 4. 9– 5. 0 4. 8– 4. 9 4. 7– 4. 8 4. 6– 4. 7 4. 5– 4. 6 4. 4– 4. 5 4. 3– 4. 4 4. 3

CLIMATE CHANGE: ENHANCED GLOBAL WARMING • SINCE THE INDUSTRIAL REVOLUTION, THE CONCENTRATION OF CO 2 IN THE ATMOSPHERE HAS INCREASED GREATLY AS A RESULT OF BURNING FOSSIL FUELS AND WOOD REMOVED BY DEFORESTATION. • THE AVERAGE CO 2 CONCENTRATION IN THE ENVIRONMENT WAS 274 PPM BEFORE 1850. • MEASUREMENTS IN 1958 READ 316 PPM AND HAVE INCREASED TO 370 PPM TODAY. • INCREASED PRODUCTIVITY BY VEGETATION IS ONE CONSEQUENCE OF INCREASING CO 2 LEVELS. • RISING ATMOSPHERIC CO 2 LEVELS MAY HAVE AN IMPACT ON EARTH’S HEAT BUDGET.

• WHEN LIGHT ENERGY HITS THE EARTH, MUCH OF IT IS REFLECTED OFF THE SURFACE. • CO 2 CAUSES THE EARTH TO RETAIN SOME OF THE ENERGY THAT WOULD ORDINARILY ESCAPE THE ATMOSPHERE. • THIS PHENOMENON IS CALLED THE GREENHOUSE EFFECT. • IF IT WERE NOT FOR THIS EFFECT, THE AVERAGE AIR TEMPERATURE ON EARTH WOULD BE − 18°C.

HUMAN ACTIVITIES ARE DEPLETING ATMOSPHERIC OZONE. • LIFE ON EARTH IS PROTECTED FROM THE DAMAGING AFFECTS OF ULTRAVIOLET RADIATION (UV) BY A LAYER OF O 3, OR OZONE, THAT IS PRESENT IN THE LOWER STRATOSPHERE. • STUDIES SUGGEST THAT THE OZONE LAYER HAS BEEN GRADUALLY “THINNING” SINCE 1975. • THE DESTRUCTION OF OZONE PROBABLY RESULTS FROM THE ACCUMULATION OF CFCS, OR CHLOROFLUOROCARBONS —CHEMICALS USED IN REFRIGERATION, AS PROPELLANT IN AEROSOL CANS, AND FOR CERTAIN MANUFACTURING PROCESSES.

• THE BREAKDOWN PRODUCTS FROM THESE CHEMICALS RISE TO THE STRATOSPHERE, WHERE THE CHLORINE THEY CONTAIN REACTS WITH OZONE TO REDUCE IT TO O 2. • SUBSEQUENT REACTIONS LIBERATE THE CHLORINE, ALLOWING IT TO REACT WITH OTHER OZONE MOLECULES IN A CATALYTIC CHAIN REACTION.

1 Chlorine from CFCs interacts with ozone (O 3), forming chlorine monoxide (Cl. O) and oxygen (O 2). Chlorine atoms O 2 Chlorine O 3 Cl. O O 2 3 Cl. O Sunlight causes Cl 2 O 2 to break down into O 2 and free chlorine atoms. The chlorine atoms can begin the cycle again. Cl 2 O 2 Sunlight 2 Two Cl. O molecules react, forming chlorine peroxide (Cl 2 O 2).

RESULTS: INCREASED LEVELS OF UV RADIATION INCREASES IN SKIN CANCER AND CATARACTS DAMAGE TO PLANTS • EVEN IF ALL CHLOROFLUOROCARBONS WERE BANNED GLOBALLY TODAY, CHLORINE MOLECULES ALREADY PRESENT IN THE ATMOSPHERE WILL CONTINUE TO REDUCE OZONE LEVELS FOR AT LEAST A CENTURY.

5) ADD TOXINS AND TOXICANTS TO ENVIRONMENT - TOXINS CAN BECOME CONCENTRATED IN SUCCESSIVE TROPHIC LEVELS OF FOOD WEBS. BIOLOGICAL ACCUMULATION AND MAGNIFICATION - TOXICANTS INGESTED AND METABOLIZED BY ORGANISMS CAN ACCUMULATE IN THE FATTY TISSUES OR MUSCLES OF ANIMALS AND BECOME MORE CONCENTRATED IN SUCCESSIVE TROPHIC LEVELS OF A FOOD WEB • MAGNIFICATION OCCURS BECAUSE THE BIOMASS AT ANY GIVEN TROPHIC LEVEL IS PRODUCED FROM A MUCH LARGER BIOMASS INGESTED FROM THE LEVEL BELOW. • THUS, TOP-LEVEL CARNIVORES TEND TO BE THE ORGANISMS MOST SEVERELY AFFECTED BY TOXIC COMPOUNDS IN THE ENVIRONMENT.

- MANY TOXINS CANNOT BE DEGRADED BY MICROBES AND PERSIST IN THE ENVIRONMENT FOR YEARS OR DECADES. - OTHER CHEMICALS MAY BE CONVERTED TO MORE TOXIC PRODUCTS BY REACTION WITH OTHER SUBSTANCES OR BY THE METABOLISM OF MICROBES. EX: MERCURY WAS ROUTINELY EXPELLED INTO RIVERS AND OCEANS IN AN INSOLUBLE FORM. • BACTERIA IN THE BOTTOM MUD CONVERTED IT TO METHYL MERCURY, AN EXTREMELY TOXIC SOLUBLE COMPOUND THAT ACCUMULATED IN THE TISSUES OF ORGANISMS, INCLUDING HUMANS WHO FISHED IN CONTAMINATED WATERS.

Concentration of PCBs Herring gull eggs 124 ppm Lake trout 4. 83 ppm Smelt 1. 04 ppm Zooplankton 0. 123 ppm Phytoplankton 0. 025 ppm