Ecosystem Functioning and the Importance of Biotic Control

1. “Monday is an awful way to spend 1/7 of your week…” “A clear conscience is usually a the sign of a bad memory” “I used to have an open mind, but my brains kept falling out”

2. U6220: Environmental Chem. & Tox.Thursday, July 07 2005 • Ecosystem functioning • Biological Oxygen Demand • Detergents and Phosphates • Phosphorus control: A US case-study • Coastal Hypoxia: From the Gulf of Mexico to the Chesapeake

3. Biotic Control over EcosystemsChapin et al (1997), Science, Vol. 277, p.500-503 • Ecosysts Processes: productivity and nutrient cycling • Regional Processes: trace gases and nutrient fluxes • Community Processes: competition and predation • Ecosyst Services: benefits to humans from above processes

4. Biotic Control over EcosystemsChapin et al (1997), Science, Vol. 277, p.500-503 • The number of species in a community is a measure of the probability of the presence of species with particularly important traits • Greater diversity allows a greater range of traits to be represented in the ecosystem providing opportunities for more efficient resource use in a variable environment • No two species are ecologically redundant, even if they appear similar in their ecosystem effects under one particular set of environmental conditions. “Changes in species composition are likely to alter ecosystem processes through changes in functional traits of biota”

5. Defining the Ecosystem Biology is not the sole subject of ecosystem studies  The flow of energy and materials (i.e. water, chemicals) into and out of biological communities defines the main theme of ecosystem studies

6. Defining the Ecosystem There exists an inseparable relationship between the flow of energy and the flow of nutrient elements (i.e. N, P, K, Ca, etc)

7. Required elt Required for some life forms Toxic elt Chemical Elements (the Periodic Table) and those essential for life • Of the 103 elements in the Periodic Table, only 24 arerequiredby organisms • Macronutrients: Required in large amount(“Big Six”: C, N, P, S, O, H) • Micronutrients: small or moderate amount

8. Chemical Elements - Essential for lifeCarbon • Carbon forms three-dimensional molecules of large size and complexity in organic (carbon-containing) compounds that form large molecules (amino acids, sugars, enzymes, DNA), and other chemicals vital to life on Earth.

9. Chemical Elements - Essential for lifeNitrogen Proteins contain up to 16% N • Nitrogen (along with carbon) is the essential element that allows formation of amino acids ( proteins) and DNA.

10. Chemical Elements - Essential for lifePhosphorus • Phosphorus is the “energy element” occurring in compounds called ATP and ADP important for energy transfer processes and DNA.

11. Chemical Elements - Essential for lifeCarbon:Nitrogen:Phosphorus Ratios • Organisms actively concentrate certain elements essential for life:  Algae concentrate Iron (Fe) 100,000 times vs. its concentration in the Ocean • Most organisms keep a rather constant chemical composition  Algae and plankton C:N:P ratio of 106:16:1 (Redfield Ratio)  Soil microbes maintain a relatively constant proportion of nutrients in their biomass (and at higher levels than the OM they decompose)

12. Chemical Elements - Essential for life • Availability of some elements (particularly N & P) is often limited and the supply of these elements may control the rate (or type) of primary production in terrestrial ecosystems. • External sources of nutrients are varied and depend of nutrient  Annual circulation dominates most inputs of limiting elements (N, P, K)

13. O2 solubility and ventilation O2 solubility is dependent on temperature of water: Usually oscillates between 6-14 mg/L in aerated natural waters. O2 diffusion in surface waters is a slow process aided by turbulent mixing of water (and cold temperatures) How much O2 do aquatic organisms need? • 8-15 mg/L: Excellent • 6-8 mg/L: OK • 4-6 mg/L: Stressed • 2-4 mg/L: Critical • <2 mg/L: Hypoxia

14. Dissolved O2 and Biological Demand In surface waters, microorganisms degrade and ultimately mineralize NOM (and organic wastes) consuming O2 and releasing CO2 and/or CH4. If DO is consumed at rate that exceeds replenishment rate of O2 from atmosphere (reaeration) or from photosynthesis  DO concentrations can decrease to < 1-2 mg/L generating hypoxia/anoxia. Biological Oxygen Demand (BOD):is a measure of the amount of O2 required by microorganisms to degrade dissolved and suspended organic matter in a volume of water. (loss of DO in water incubated in the dark at 20°C for 5 days) Water status? • BOD: <1 mg/L: Clean • BOD: >10 mg/L: Polluted

15. Dissolved O2 and Biological Demand The most important source of O2 for most water bodies is oxygen in the atmosphere (when photosynthesis is not considered). Increased BOD in the water can lead to a deficit below the saturation level (level at which DO is at 100% saturation). But, the reaeration of water (ventilation) is proportional to the O2 deficit (gradient between atmosphere-water interface): dD/dt = k1L - k2D L: BOD concentration; D: O2 deficit; k1: BOD decay rate constant (0.2/day); k2: reaeration coefficient However, this recovery calculation does not take into consideration the O2 consumption occurring in the bottom sediments, which can induce delays in the recovery time.

16. Dissolved O2 and lake trophic status Eutrophication and Cyanobacteria: Blue-green algae that generate “blooms” which induce hypoxia/anoxia and release of toxins (harmful algal blooms HAB).

17. Hardness and detergents The hard and soft appellation of waters reflect the fact that doubly charged Ca2+ and Mg2+ ions can precipitate detergents (molecules with long hydrocarbon chains and polar head groups) Detergents are excellent cleanser because of their ability to act as emulsifying agents (an emulsifier is capable of dispersing one liquid into another immiscible liquid). Disadvantages: As salts of weak acids, they are converted by mineral acids into free fatty acids: CH3(CH2)16CO2-Na+ + HCl  CH3(CH2)16CO2H + Na+ + Cl- Soaps form insoluble salts in hard water, such as water containing magnesium, calcium, or iron: 2 CH3(CH2)16CO2-Na+ + Mg2+ [CH3(CH2)16CO2]2Mg2+ + 2 Na+

18. Hardness and detergents Addition of chelating agents (builder) can bind with cations through multiple bonds. Particularly effective chelating agents: The first is a limiting nutrient, the other two biodegrade slowly (T dependent) and mobilize toxic chemical! EDTA Nitrilotriactetic acid (NTA) Sodium Tripolyphosphate (STP)

19. Source: USGS 1999 Phosphorus Control MeasuresA U.S. Case Study • As more States passed detergent-bans legislation, the industry was faced with maintaining duplicate inventories of detergent around the Nation and ultimately decided (cost effective) to phase out phosphorus use in domestic detergents • Phosphates are still permitted in dishwashing detergents and industrial cleaning agents.

20. Source: USGS 1999 Phosphorus Control MeasuresA U.S. Case Study • As more States passed detergent-bans legislation, the industry was faced with maintaining duplicate inventories of detergent around the Nation and ultimately decided (cost effective) to phase out phosphorus use in domestic detergents • Phosphates are still permitted in dishwashing detergents and industrial cleaning agents.

21. Source: USGS 1999 Phosphorus Control MeasuresA U.S. Case Study • Only about 15% of municipal waste-water treatment plants (~40% of total municipal waste-water discharge) were required to monitor phosphorus • Only 7% have phosphorus limitations (0.5-1.5 mg/L) through tertiary treatment!

22. Phosphorus Control Measures: A U.S. Case Study • Phosphate ban reduced annual loads to Lake Erie (86%) and Chesapeake Bay (55%) • Temporal trend in declining phosphorus levels in surface waters (except Southeast). However, at least one third of all hydrological units studied showed more than 1/2 of total phosphorus concentrations exceeding the EPA recommended limit in flowing waters (0.1 mg/L)

23. Non-Point Sources of Phosphorus Phosphorus from manure and commercial fertilizers

24. Coastal Hypoxia Nutrient over-enrichment from anthropogenic sources is one of the major stresses impacting coastal ecosystems. Generally, excess nutrients lead to eutrophic conditions and increased algal production which in turn increases the availability of organic carbon within the aquatic ecosystem. Both the near-coastal hydrodynamics that generate water column stratification and the nutrients that fuel primary productivity contribute to the formation of hypoxic zones. Human activities on land can add excess nutrients to coastal areas or compromise the ability of ecosystems to remove nutrients either from the landscape or from the waterways themselves.

25. Gulf Coast Hypoxia Nitrogen is the most significant nutrient controlling algal growth in coastal waters, while phosphorus is the most significant nutrient in fresh water (source: USGC)

26. Coastal Hypoxia Gulf of Mexico: a large area of the Louisiana continental shelf with seasonally-depleted oxygen levels (< 2mg/l). Most aquatic species cannot survive at such low oxygen levels. The oxygen depletion (hypoxia) begins in late spring, reaches a maximum in midsummer, and disappears in the fall. After the Mississippi River flood of 1993, the spatial extent of this zone more than doubled in size, to over 18,000 km2, and has remained about that size each year through midsummer 1997. The hypoxic zone forms in the middle of the most important commercial and recreational fisheries in the coterminous United States and could threaten the economy of this region of the Gulf.

27. Coastal Hypoxia Estimated areal extent of bottom water hypoxia from mid-summer cruise in the period 1985-1999 20 15 10 103 km2 5 0 (source: Louisiana Universities marine Consortium)

28. Gulf Coast Hypoxia Long-term record of drainage basin changes: a) annual amount of fertilizer application 106 metric tons/year b) area artificially drained 106 of acres 1900 1920 1940 1960 1980 2000

29. Gulf Coast Hypoxia Nitrogen yields from the Mississippi River Drainage Basin About 56% of the nitrate transported to the Gulf enters the Mississippi River above the Ohio River. The Ohio basin subsequently adds another 34% of the nitrate load.

30. 2.5 30 Streamflow 25 2.0 Organic N 20 1.5 15 1.0 Nitrate 10 0.5 1950 1960 1970 1980 2000 Gulf Coast Hypoxia On average, 61% of the nitrogen load is nitrate; 24% is dissolved organic nitrogen. The most significant nutrient trend has been nitrate loads, which have almost tripled from 0.33 million metric tons per year during 1955-70 to 0.95 million metric tons per year during 1980-96

31. Factors Potentially Contributing to Hypoxia in the Gulf: • Landscape changes in the drainage basin: Wetlands and riparian zones can improve water quality and reduce nitrogen flux down the Mississippi River by enhancing denitrification (the conversion of nitrate to nitrogen gas, with subsequent loss from the aquatic system) and incorporating nitrogen into vegetation. However, the natural capacity of the river basin to remove nutrients has diminished. • Many of the original freshwater wetlands and riparian zones that were connected to streams and rivers are gone. Ohio, Indiana, Illinois, and Iowa have had over 80% of their wetlands drained. Indiana, Illinois, Iowa, Minnesota, Missouri, and Wisconsin collectively have lost the equivalent of 14.1 million ha (35 million acres) of wetlands over the past 200 years.

32. Factors Potentially Contributing to Hypoxia in the Gulf: • Organic loading from the Mississippi River: Suspended sediment in the river has declined by about half since the 1950s, so the POC load that can settle on the Louisiana shelf has also most likely decreased since then. Also, nutrient cycling affords nitrogen the ability to stimulate production of organic carbon at rates that far surpass that supplied by the river. Whereas decomposition of river-supplied organic carbon consumes oxygen only once, river-supplied nitrogen can be recycled and thus provides a continuous source of comparatively easily decomposed organic carbon.

33. Factors Potentially Contributing to Hypoxia in the Gulf: • Channelization of the delta and loss of coastal wetlands: Coastal wetland loss rates exceeded 100 km2 (about 40 square miles) per year between 1950 and 1980. Recent wetlands protection and restoration programs helped reduce losses in the 1990s to 65-90 km2 (about 25-35 square miles) per year. Both the loss of wetland filtering capacity and the direct contribution of organic matter eroded from wetlands and carried to the Gulf may contribute to the problems of hypoxia; however, the total contribution is relatively small compared with the nitrogen-related factors. • Intrusion of deeper offshore waters: Flow of nitrate from deeper waters may be important at the shelf edge (at depths of approximately 100 meters); however, all data indicate that the Mississippi and Atchafalaya Rivers contribute substantially more nutrients to the inner shelf and hypoxic region.

34. Factors Potentially Contributing to Hypoxia in the Gulf: • Short- or long-term climate changes: On that time scale, there is no indication that climate factors override the impacts of human activities in the basin. Average annual flow in the Mississippi River increased 30% between 1955-70 and 1980-96, compared to the 300% increase in nitrate flux over this period. Episodic events, such as the 1993 flood, can nearly double the nitrate flux to the Gulf in a given year as a result of both higher-volume flow and increased leaching of nitrate from the drainage basin. There are indications that the future climate for this basin may be wetter and may include more extreme events, leading potentially to increased water and nitrate fluxes.

35. Long Island Sound Hypoxia Hypoxic conditions during the summer are mainly confined to the Narrows and Western Basin of Long Island Sound (from Stratford, CT to Port Jefferson, NY). The maximum extent of the hypoxic condition typically occurs in early August and affects ~472 km2. The summer of 2003 LIS experienced one of its most severe hypoxic events.  The duration was merely average due in large part to a strong wind event on September 2, 2003.  The areas affected by low dissolved oxygen were some of the largest recorded.  The summer of 2003 had the second largest area DO below 2 mg/L (186 sq. miles) and 3 mg/L (345 sq. miles), second only to 1994.  The area affected by DO levels below 1 mg/L (62 sq. miles) was the largest recorded since the monitoring program began in 1991.

36. Chesapeake Bay Program • Streamflow, loads, and trends • Stressors to the Bay ecosystem and watershed • Flow • Loads • Health of the Watershed • Status and observed concentration • Restoration “progress” • Flow-adjusted trends in concentrations • Effectiveness of restoration actions

37. Nitrogen Loads

38. “Total” Nitrogen Load to the Bay

39. Nitrogen in the Susquehanna • Flow-adjusted trends in concentration • ESTIMATOR model used to help compensate for natural variability in stream flow and season • Compute trends in “flow-adjusted” concentration • Estimate of change due to sources and management actions

40. Phosphorus in the Susquehanna

41. Factors Affecting Delivery and Trends • Stream flow variability • Source changes and BMPs • Watershed properties • Soils • In-stream loss • Ground water • “Lag Time” • New USGS Report in 2006 “The destiny of ecosystems is driven by their legacy”

42. Education is an admirable thing, but it is well to remember from time to time that nothing that is worth knowing can be taught. - Oscar Wilde