Nov. 7 Nutrient cycling in wetlands: The diffusion of oxygen in saturated soils is 10,000 times slower than in unsaturated soils. A saturated soil will become anaerobic in a matter of hours (matter of days at the most) depending on 1) temperature 2) the amount of organic matter 3) the initial microbial community and 4) the amount of reducing compounds present (example: ferrous iron). The general reaction is [CH2O]n + nH2O nCO2 + 4ne- + 4nH+ , where [CH2O] is organic matter. As plant material decays, electrons (H+) will be available in excess to react with already released organic compounds (like nitrogen). This process moves to a state that is more acidic. O2 disappears the fastest, followed by NO3, and SO3. At the same time Mn, Fe, NH3, CH4 and HS are released from the system. Oxygen reacts with electrons to produce water: O2 + 4e- +4H+ 2H2O. In the anaerobic state, both biological and electrochemical activities are found. There is a gradient in soils with an aerobic zone on top, an oxidizing layer, and an anaerobic zone on the bottom. As plant material decays, the carbon in the aerobic zone is broken up by microorganisms into dissolved organic carbon. In the anaerobic zone fermentation occurs. In this process, microorganisms convert dissolved organic carbon into lactic acid or ethanol. Methanogenic organisms work in the anaerobic zone to convert dissolved organic carbon into methane. In both the aerobic and fermentation processes, CO2 is generated. This involves the bicarbonate cycle: H2CO3 HCO3 CO3-. This process also affects the pH of the water. The production of methane is much more common in freshwater systems. In saltwater less than <1mg C is converted to methane per day. In freshwater (especially marshes) this number can be up to 440. In the nitrification process, organic nitrogen becomes soluble and is converted to NH3 (ammonia) and then NH4OH (ammonium ion). This ion is used by plants or is washed away by runoff. Nitrosomonas is the species of bacteria responsible for the conversion of ammonia to nitrite, and Nitrobacter converts nitrite to nitrate. Rhizobia associations and algae also fix nitrogen to bring into the system. Plants can take up nitrate or ammonia forms of nitrogen. Denitrification is the process which produces N2 (N gas). This gas is released when soil is disturbed, or is released slowly into the atmosphere. Wetlands are one of the only places where N2 is produced, this is important for the ecosystem. The sulfur cycle involves the conversion of organic sulfur into H2S which is stored in soil. H2S can also be released into the atmosphere or oxidized to sulfate in the aerobic zone. Sulfate is taken up by plants or washed away by runoff. HS production is lower in saltwater and high in freshwater. The phosphorous cycle starts with the decomposition of particulate phosphorous and then its conversion into soluble phosphorous. Soluble phosphorous can be taken up by plants and algae or absorbed by clay particles. Compounds found bound to soil are CaP, AlP, and FeP. This chemistry in the soil is the reason that higher concentrations of P are found in effluent than in influent. Constructed wetlands are not very good at decreasing P levels. A big debate over wetlands concerns their role in the environment. Are they sinks, sources, or transformers? Nov. 12 The Florida Everglades: A Case Study The Everglades are often called a river of sawgrass. This area is almost completely monospecific. The restoration of the Florida Everglades has created a lot of jobs in hydrology and environmental fields. The cause of the problem is the 5 million people living around the area, and agricultural developments. The soil in the Everglades took over 5000 years to develop, and has depleted in less than 100. This natural ecosystem has developed around Lake Okeechobee and runs all the way down to Florida Bay. There is a Cyprus Swamp adjacent to the Everglades. 1881 - Gov. Bloxham sold $4 million of swamp land to Hamilton Viston. Viston did the first drainage and joined rivers and lakes by canals. Viston got about 50,000 acres of usable farmland. After severe flooding, Viston finally went bankrupt. 1905 - Gov. Napoleon Bon Broward spread the slogan drain the Everglades in response to the 1903 floods. This got him into office. Broward started the cut n try era which was not very scientific. 4 canals were cut, all draining to the Atlantic. 1926-1928 - Major hurricane, floods took out Lake Okeechobee. 1930 - Army Corp of Engineers took charge of the Everglades. The lake level was lowered and a ten foot levy was placed all around the bottom of the lake. This gave many a sense of security for farming and sugarcane agriculture started. (There are 500,000 acres of agricultural land, 300,000 is sugar cane.) 1934 - Sugar act - protected farmers from sugar imports. 1947 - Flood - the entire south region of Florida. All control was given to the Army Corp of Engineers who came up with 20 year plan. 1947 - The Everglade agricultural area was defined, along with the Water Conservation areas and water flow was delivered to the Everglades Park. 1981 - Gov. Graham - save our Everglades. There are now 5 million people living there and a huge system for flood control. 1983 - El Nino floods. This caused the release of huge amounts of water to the Water Conservation areas and the Everglades Park. A mess was created down to Florida Bay. Major Environmental Concerns: The water conservation areas are not really holding the water, almost all of it is drained to the Atlantic Ocean. The flow needs to be re-adjusted to the Water Conservation areas. The construction of wetlands to treat agricultural runoff has increased phosphorous concentrations. The Everglades agricultural area has lost almost all of its soil. What is left is limestone and coral reef. Oxidation from drainage has composed the substrate that was almost completely organic matter (98%). The Water Conservation areas were meant t preserve the Everglades. An Australian tree, Melaluca, has invaded along canal banks and greatly increased evapotranspiration rates. There has also been a cattail invasion because of excess phosphorous. Wading birds are disappearing. A lack of freshwater has caused changes in Florida Bay. This is now a hypersaline area because it acts like an evaporation basin (50-80 ppt). An increase in salinity has caused the mangroves to die off. The loss of mangroves has led to the loss of seagrasses in the 1980s (80% formerly covered). This change in habitat has decreased the manatee, crocodile and bird populations. Nov. 14 Vegetation in the Everglades: There are 830 species in the swamp from Lake Okeechobee to Florida Bay. (This is not including Cyprus swamp or Everglades park.) 17% are exotic species which have been introduced by man. 8% are endemic species, native to an area and only found there (51 species). These are mostly relics of the old forest. The rest of the species are tropical or temperate plants from nearby ecosystems (the Caribbean and up north). Grasses, Cyprus and orchids are common families found in the Florida Everglades. I. Upland Species (upland is only 1-2 m higher in the Everglades) A. Rockland Pine Forest - low understory and high understory. This area is covered with pine, the understory is where all of the unique species live. B. Tropical Hardwoods II. Wetland Species (these are what make a productive ecosystem) A. Forests (aquatic trees) - Bayheads, Willowheads, Cyprusheads, and some Pond Apple. A head is started where there is a small rise and soil can gather for trees to start growing. B. Sawgrass Marshes - Common species is Cladium jamaicense which is adapted to grow in a cycle of fire about every 5 years. This species takes 2 years to grow back. Melaluca tree also grows here, this was introduced by J.C. Gifford in the 1920s. C. Wet Prairies and Sloughs (wettest areas) - Sloughs are the main water courses through the Everglades park. The southern part is dominated by grasses and submerged aquatic plants. Periphyton is the base of the food chain. Submerged plants are collecting points for silt and algae which stick to plant stems to create periphyton. Periphyton is a mixture of algae and bacteria which floats in large mats. This is the key to productivity because little fish feed on the mats, which are eaten by big fish, zooplankton, etc. Larger species like birds and crocodiles are disappearing because periphyton is not able to grow. Periphyton can now only be found in the wettest areas. Disturbances: 1) Extra P from sugarcane farms - original conditions were oligotrophic (.03 ppm P) and the only input of P was from rainfall. Historic loading of P (tons/year) Current loading of P (tons/year) WCA: Rain 118 Rain 118 Overland 11 Overland 258 Total 129 Total 376 E Park: Rain 78 Rain 78 Overland 10 Overland 11 Total 88 Total 89 Phosphorous is picked up by the soil and stored, this is bad because it promotes continued vegetation change for many, many years into the future. Phosphorous promotes cattail growth and eliminates periphyton mats. Cattail has now penetrated into the canals to Everglades Park. 2) Hydrology - The water is not managed the same way. Sheet flows are diverted to canals and releases do not follow natural cycles anymore. 3) Fire - Sawgrass is killed by intense fires and open water areas are created. 4) Exotic plants Fauna problems: 1) Upland animals are suffering from water fluxes (panthers, deer). 2) Small fish are giving way to larger fish in Water Conservation areas, this is hard for wading birds that feed on small fish. 3) Snail kite (bird) has had good luck in the Water Conservation areas. There are perfect conditions for this endangered species. 4) Wading birds have suffered a nesting decline due to loss of periphyton mats. 6 Principles of Restoration: 1) Reverse the reduction of size and compartmentalization of all Everglade ecosystems. These are now artificially levied off and the only water flow is through canals. All areas need to be hydrologicaly connected. 2) Restore natural fire and hydrological cycles (let fires burn). A Natural Hydrology Model has been designed based on antecedent rainfall. Researchers predict the natural flow from rainfall measurements and try to restore with pumps and levees. 3) Restore flows, volumes, and distributions using antecedent rainfall. 4) Restore depth patterns. 5) Mimic extended floods. 6) Agricultural areas should begin to grow wetland crops because of the lack of soil.