 Aquatic and terrestrial ecosystems require essential nutrients to maintain rich and productive communities. These ecosystem functions and properties require several kinds of nutrients. Today we're going to focus on three major nutrients, carbon, nitrogen, and phosphorus. All biological systems require these three nutrients in large amounts, and therefore we call them macronutrients. The sources of carbon include the production that occurs within an ecosystem. We often call that plant production that occurs within an ecosystem autochthonous organic carbon. It also requires material from outside the ecosystem that comes into it, such as leaves and needles falling into a stream. We refer to these sources of organic material as aloxanous organic material or aloxanous carbon, and these sources of energy are very, very important for both aquatic and terrestrial ecosystems. Organic matter in an aquatic ecosystem can exist as either dissolved organic matter. Typically we have an operational definition of roughly about half a micron as our definition of dissolved organic matter. Anything less than that, we consider dissolved. Anything larger than half a micron is considered particulate organic matter. In aquatic ecosystems, the amount of DOC is usually much, much greater than the amount of particulate organic carbon. The dissolved material is a major source of energy in aquatic systems and in soil systems. In oligotrophic or very pristine or low nutrient waters, the DOC to POC ratio, the dissolved to particulate ratio, is roughly five. But in more eutrophic or highly productive systems, we see that the dissolved organic material is often 10 times the amount of particulate organic carbon. We can use the carbon to nitrogen ratio as a measure of the quality of the organic material as a food resource. In terrestrial ecosystems, we commonly see very, very high carbon to nitrogen ratios, CN ratios. Quite often they are anywhere from 20 to as high as 200. In aquatic ecosystems or aquatic plants, we often see that the carbon nitrogen ratios are much lower, often anywhere from 5 to 10 to as high as maybe 15 for vascular macrophytes. This indicates that the aquatic plants in general are a higher quality food resource than the terrestrial sources of energy. In terms of the breakdown or utilization of organic material, we use two major terms. One term is refractory. Refractory compounds are those that resist decay. They tend to be very large molecules with very high molecular weights. They tend to have low solubility, and they tend to have very strong structural components in the material that they are derived from. So these refractory materials are very difficult for organisms to assimilate or consume. An example would be this molecule of lignin from beach leaves. And you see it's a very complex molecular structure, and it's very difficult for microbes to break it down or for animals to break it down and use it for energy. The other term that we use besides refractory is labial. Labial compounds are utilized very, very rapidly. They tend to be low molecular weights as a result, and they tend to have a very high solubility, and they generally represent nonstructural compounds, things that come from the protoplasm or the cytoplasm within the cell, and leak out. And they tend to be much more readily used by organisms. An example would be something like the simple glucose molecule, the simplest sugar. It's very simple to break down this molecule and obtain the energy within it, and therefore it's used very, very rapidly. And glucose would be an example of a very labial organic compound. Now, when we look at the amounts of material that we find in ecosystems, we tend to see that the labial compounds are used very, very rapidly. The concentrations in organic carbon or dissolved organic carbon tend to increase as we go downstream, and generally that represents an increase in the amount of refractory organic material we see very slight seasonal fluctuations in these compounds as a result. This is an example of the utilization of organic material differently. A good analogy would be if I put out a buffet table here in front of you, and I piled it full of foods, some of which you dearly love. It could be your favorite cakes and pies and brownies and cookies, some food that's kind of in between, and then something you hate. I don't know what it is. Brussels sprouts is one I hate. Broccoli, something like that. Something lousy that isn't that good. And so if I let you all come up to the buffet table and eat all you want, and we started sampling how much material was present on that buffet table, we would find that there tends to be tons and tons of Brussels sprouts left around, and the brownies would be almost nonexistent. And it's almost the same way in aquatic and terrestrial ecosystems. The material that we measure there tends to be the material that organisms aren't using as rapidly. And so the amount of dissolved organic carbon that we find in water, for instance, tends to be the refractory material that things aren't using. The labile material is used very, very rapidly, just like those brownies were scarfed up so quickly. The nitrogen compounds are also very, very important because amino acids and proteins are formed from nitrogen. So all organisms require nitrogen for protein synthesis. Nitrogen can exist in many different forms, only some of which are available to the biota. Nitrogen gas is the most abundant form of nitrogen in the atmosphere. 80% of our atmosphere is made up of nitrogen gas. But unfortunately, most organisms can't use nitrogen gas as a nitrogen source. And so we see compounds such as ammonia or ammonium being used very rapidly by these organisms. And so ammonium or ammonium are very important nutrients for plants and animals in aquatic ecosystems, and terrestrial ecosystems. Nitrite, an oxidized form of nitrogen in O2, is present in very, very low concentrations. And that's a good thing because nitrite is very toxic. It's quickly oxidized to nitrate, which is far less toxic and is an important nutrient. And so nitrate and ammonium tend to be the major nutrient sources for plants in both terrestrial and aquatic ecosystems. And then finally, the nitrogen that's formed from this nitrate anemonium, the nitrogen that's in the form of organic nitrogen is also present, either dissolved or particulate in streams, lakes, and terrestrial ecosystems. So the major forms of nitrogen are nitrogen gas, ammonia, ammonium, nitrite, nitrate, and organic nitrogen. We see here a nitrogen cycle. I realize it's very complicated, so I'm going to walk through it fairly slowly with you with a pointer. Now, first of all, we mentioned nitrogen gas is not used by most organisms. But luckily, there are a few organisms out there that are able to convert nitrogen gas to ammonia or ammonium through the process of nitrogen fixation. Nitrogen fixers are important organisms that get nitrogen into the food web through the process of nitrogen fixation. Examples in aquatic ecosystems would be the blue-green algae or cyanobacteria. Examples in terrestrial ecosystems would be things like clover and the legumes that are nitrogen fixers. So this part of the nitrogen cycle is a very important transfer of nitrogen gas to the form of ammonium. Once it's in the form of ammonium, it is quickly transferred into amino acids and proteins. And so we see this transfer of ammonium into amino acid through amino acid synthesis. And then those amino acids used to form proteins in the cells of plants and animals. This material will break down or lice out of the cell into the form of organic nitrogen, dissolved organic nitrogen. And so it leaks out of the cells or as the cells die, they release this material. The dissolved organic nitrogen is transferred by microorganisms or transformed by microorganisms through the process of a modification and is transformed back to ammonium. So we see a loop, a biological loop that goes from ammonium forming amino acids and proteins those leaking out of cells into dissolved organic nitrogen and that being modified again back to ammonium. The ammonium is also used by nitrifiers, nitrifying bacteria that are present and they oxidize the ammonium first to nitrite and then to nitrate. This is a two-step process with different microorganisms. It's critical that both of these sets of organisms are present in the environment so that the nitrification occurs all the way to the form of nitrate because the nitrite is very toxic. The nitrate can then be taken up by plants or assimilated by plants, bacteria, fungi and other organisms and re-entered into the biological cycle. It can also be used as an energy source in the process of denitrification in anaerobic environments. And so this transformation of nitrogen in the nitrogen cycle is very complicated and is mediated by organisms throughout the entire nitrogen cycle. And this is a very important cycle in determining the productivity of aquatic and terrestrial ecosystems. Phosphorous is another major compound. Phosphorous is required in many of the energy-containing compounds within organisms and it's also an important component of membranes in the phospholipids and allowing the transfer of particles across membranes. And so phosphorous is an important nutrient that's required by all living organisms, plants, animals, bacteria, fungi, the entire suite of organisms, living organisms require phosphorus. Phosphorous at first glance seems much simpler than nitrogen because there's two major forms. Inorganic phosphorus, we sometimes refer to this inorganic phosphorus as orthophosphate or we also refer to the same group of compounds as soluble reactive phosphorus based on our analysis for this form of phosphorus. Another form is organic phosphorus and so you might say well that's a lot better than nitrogen because it's so much simpler. But actually what we're calling orthophosphate or soluble reactive phosphorus is kind of a garbage can of terms because there's a lot of different phosphorus compounds that come out in that analysis and so there are literally hundreds of phosphorus compounds that we lump into that category so it is a very complex process and the form of those different forms of inorganic phosphorus determine the rates of biological processes but simply today we'll consider the inorganic and organic phosphorus. In general phosphorus in groundwater and surface waters are relatively low. Groundwater sources in particular are extremely low in phosphorus quite often we have concentrations that are far less than 20 micrograms per liter and quite often they're down around one to two or three micrograms per liter. Surface runoff tends to have slightly higher concentrations of phosphorus particularly where soil or erosion is coming into surface waters. These soil particles often carry phosphorus adsorbed onto the particles and release it into the water and so one of the major sources of input is the movement of soil into aquatic systems and so whether it's lakes streams ponds the introduction of soil through erosion is a major addition of phosphorus as well as the addition of soil. The amount of phosphorus that we find in streams and lakes and rivers and ponds is related to the topography the uptake by the vegetation the amount of runoff how much water there is pouring across the land the land uses that are occurring any kinds of direct pollution and as we mentioned before erosion of soil. In lake systems the phosphorus content of the parent geologic material tends to vary quite a bit many areas it can be quite low but if you're in volcanic areas basalt tends to have relatively high concentrations of phosphorus so the parent geologic material can vary quite a bit as a supply of phosphorus. Pollution from fertilizers is a major source of phosphorus in lakes streams and rivers the pollution from detergents in particular back in the late 60s was a major debate but quickly resolved that the high phosphate detergents were a major source of pollutants. Now you may have remembered the advertisements for the whiter whites and brighter brights. Phosphates were used to get clothes clean. Basically the detergents bind with soil and then they're washed out of your clothes and that cleans your clothes but if there are too many compounds around in the water that could bind with the soap you don't get your clothes clean so what manufacturers did was they added phosphate is a strong negative ion and it binds with these strong positive ions to make the clothes cleaner let the soap do its work but unfortunately the phosphates that they were adding to help get the clothes clean were making the the waters extremely rich in phosphorus increasing the primary production and leading to the pollution or the eutrophication of our surface waters and so the control of phosphates in detergents and other sources has been one of the major ways that we have tried to decrease the eutrophications of the nation's surface waters the control of fertilizer application from farmlands is another major way that we try to reduce the phosphorus loading to our surface waters the phosphorus concentrations tend to increase as you get closer to the sediments as I mentioned the phosphates tend to be bound to the soil particles so as you get close to that sediment interface you tend to get more phosphorus coming out of those sediments and into the overlying surface waters the other thing that happens is you have low oxygen concentrations near the anaerobic zones and with those low oxygen concentrations you get low redox potentials that makes many of the compounds the metallic compounds soluble and they release phosphorus when they become soluble so where you have very very low oxygen you tend to have conditions that favor soluble metals and they release the phosphorus so areas around anaerobic habitats with in close proximity to the anaerobic sediments tend to have low oxygen and relatively high concentrations of phosphorus now both nitrogen and phosphorus are required by plants for production how would you know which is going to be more important in determining the level of production nitrogen or phosphorus they're both required but scientists found out in the 1800s that the amount of production is generally controlled by that substance that is in least supply in the environment relative to the demands of the organism and so you tend to have one nutrient that tends to limit production at a time one of the ways we decide whether nitrogen or phosphorus is limiting production is something called the redfield ratio redfield was a notionographer working in open oceans and he figured that the concentrations of nitrogen to phosphorus in the cells was probably a good indication of how much nitrogen they needed and then the nitrogen to phosphorus ratio in the environment indicated how rich the supply was of either nitrogen or phosphorus now most cells contain somewhere between 15 to 20 times as much nitrogen as phosphorus on a molar basis and so we can use this ratio of roughly 15 to indicate whether it's nitrogen limited or phosphorus limited if you have a nitrogen to phosphorus ratio in the surrounding environment that is less than 15 that means that it is fairly rich in phosphorus and fairly poor in nitrogen so a low nitrogen to phosphorus ratio less than 15 would indicate that the system is probably nitrogen limited if the nitrogen to phosphorus ratio is high on the other hand say greater than 15 and definitely by the time you get up to an NP ratio of 30 it's an indication that you have lots of nitrogen relative to the phosphorus that's required and so phosphorus will be limiting because you have more than enough nitrogen to meet the needs of the organism so this redfield ratio can be a good first rule of thumb about what might be limiting in an aquatic or terrestrial environment based on the ratio of nitrogen and phosphorus now in running water systems we have an issue with the typical nutrient cycle that we think about you probably all learned about nutrient cycles early in your education as nutrients are cycled within a system and you tend to think of it as being circular and a kind of a closed loop with nutrients being used in that system released taken up used taken up and so forth by all the organisms within the ecosystem but in a stream we have a different circumstance because the stream is moving unilaterally downstream and so with that flow there is kind of an opening of the cycle in what we would call a nutrient spiral the nutrient spiraling concept originated in the early 1980s and represented a way of looking at nutrient cycling in flowing water systems one of the things we use in the nutrient spiraling concept is something called the spiraling length or the symbol for s in this equation the spiraling length is determined by the flux of nutrients going by and the rate of uptake that's occurring and so you can simply think of it as flux divided by uptake now even more simply we see with the pointer that the flux can be represented as the standing stock of material how much nitrogen you have per distance of stream times its velocity so how fast is it moving by and so that will give you the flux of nutrients moving by a section of stream at any point in time but that's divided by the uptake how fast things are being taken out of the water which is a product of the amount of material or the standing stock times the uptake rate the instantaneous uptake rate and so if we divide the flux in terms of grams per meter of stream divided by the uptake which is grams per meter per second we end up with units of meters the length of a spiral that's the distance that the average atom or molecule will travel in transport before it's taken up we can see in this graph the consequences of different spiraling lengths if you have a very long spiraling length and nutrients are not taken up very rapidly we see that the concentration in the surface water decreases very slowly as we move downstream in contrast if you have a short spiraling length and nutrients are taken up very rapidly we see that the concentration of nutrients decreases very very rapidly as we move downstream this can be used as a measure of the efficiency of an ecosystem to retain nutrients we use this equation for a simple measure this is a negative exponential model or a negative exponential equation and we can calculate the amount of nutrient that would be present at any distance downstream it's simply a function of the original amount of nutrient material times the natural exponent raised to the power of the distance times the instantaneous retention coefficient or the k value this is this k value is the slope of the lines that you saw in the previous graph and that will determine the amount of material that we find at any point downstream so if you know the amount of material that you're starting with and the instantaneous rate of uptake or the instantaneous retention coefficient and the distance you can calculate the amount of nutrients that will be present at any point downstream we can use this equation also to measure the efficiency of uptake by adding nutrients to a stream so that we know this amount we measure the concentration downstream at different distances and we solve for the rate of retention and so this k value can give us a measure of the different efficiencies of retention in different ecosystems so if we take a look at this equation the average travel distance of an atom or molecule is equal to the reciprocal of this retention coefficient so 1 over k is the same as the average travel distance of the average molecule or atom in transport and so we can use that as a way of expressing how many meters the average molecule of nitrite or nitrate or ammonium or or orthophosphate might travel before it's taken up and this average travel distance is roughly equal to the spiraling length that we discussed earlier so we can use this as a measure of how efficient our systems are at retaining nutrients now in the real world we face many challenges in nutrients the natural ecosystems have a transport of nutrients inherently within them and these nutrients are taken up by the plants the trees the soil the microbes but human activities either alter those practices those processes or they can also add or load nutrients into those systems and so as a result of our land use practices we see both alteration of the natural processes that take up nutrients or we see a change in the loading or the amount of material that gets into our ecosystems one of the concerns that we have in agricultural uses are animal wastes animal waste can get into streams either from the direct addition by the animals to the streams when they're given direct access to streams and rivers and lakes and ponds and the animal waste going directly into it such as we see here with these pigs in the stream animal waste can also get into streams and rivers indirectly from sources like animal feeding operations where you have large numbers of animals in a small area and their waste running off into the soil and into the streams or being sprayed onto the land to help take up those waste and those waste entering the surface waters and increasing the eutrophication or pollution of those surface waters any animal that obviously gets directly into a stream or a lake has the potential to add nutrients directly to that system and so direct access is one of the biggest challenges in animal waste management and one of the simplest and most direct to control the indirect release of animal waste into these systems is more complicated when we see operations such as this and with a pointer you can see that the animals being confined near a stream with direct access to the stream we can see that the riparian area around the stream has been essentially obliterated and waste are going directly into those surface waters leading to a very degraded ecosystem characteristics and these when we get situations in the stream where either soil or animal waste are going directly into the stream the nutrient loading is increased tremendously and the system is degraded and the system has little potential to assimilate or take up all the nutrients that are being loaded to it in a situation like this i'm going to show you a few real world examples today of the consequences of nutrient loading on ecosystems we'll start with the mississippi river basin where land use practices have led to increased amounts of nutrients in the streams and rivers of the mississippi river basin and have led to conditions in the Gulf of Mexico that have affected other industries and we see this area right here where the mississippi river enters the Gulf of Mexico leading to a condition that is known as hypoxia hypoxia is a term for low oxygen concentrations and has created an area of extremely low oxygen in the Gulf of Mexico this area of low oxygen has been termed the dead zone because the concentrations of oxygen are so low that most of the aquatic life that is typically found there can no longer exist the hypoxia in the Gulf of Mexico is defined by dissolved oxygen concentrations that are extremely low in general it has been referred to for dissolved oxygen concentrations less than two milligrams per liter aerobic organisms require more oxygen than two milligrams per liter the factors that lead to this low oxygen concentration are stratification of the water column a natural process the decomposition of organic material that requires oxygen in the decomposition or respiration of that organic material and it's a result of nutrients that increase the production of this organic material and then when it decomposes leads to low oxygen or hypoxia an example or a cartoon of this process is the Gulf of Mexico with the plankton the microscopic plants growing in the surface waters of the Gulf of Mexico the loading of nutrients leads to increased production of the plankton the nitrate coming in from terrestrial sources through the Mississippi River leads to a bloom of plankton or an abrupt increase in the production of plankton this plankton settles out to the bottom where it consumes oxygen as it decomposes as a result of the decomposition and the low oxygen we start to see fish shrimp oysters and other organisms that require oxygen dying in 1999 this area was more than 7,000 square miles this area of very very low oxygen it was roughly the size of the state of new jersey in 2000 it was smaller but it was still a very very large area more than 1500 square miles where the oxygen levels were too low to support aerobic organisms and this depth this condition of low oxygen would extend to depths of as much as 100 feet the economic implications for the Gulf of Mexico were severe the spawning grounds the migration pathways and the feeding habitat for many of the organisms of the Gulf of Mexico were eliminated through the low oxygen concentration a fishery that annually produced almost three billion dollars was threatened and so the solutions for this condition of hypoxia in the Gulf of Mexico require management of the entire land base of the Mississippi drainage the Mississippi drainage covers approximately 41 percent of the land mass of the United States so it's a huge portion of the United States in this area more than half of it is in cropland so agricultural practices have a very direct bearing on the supply of nutrients to the surface waters of the Mississippi River the central portion of the Mississippi drainage produces the majority of the U.S corn soybean wheat cattle hog and poultry production so it's an important agricultural producer these agricultural practices while providing important resources for the nation also deliver nutrients to the ecosystems they also add other chemicals that are used in agricultural activities and so the Mississippi River basin receives large amounts of nutrients from the agricultural practices we can see here in this graph with the pointer that the concentrations of nitrate as we go from the 1950s through 2000 have roughly tripled and so the concentrations of nitrate have increased very very sharply this leads to this condition in the Gulf of Mexico as the waters come down the Mississippi River system and into the Gulf and spread into this near shore zone where we have very very high nitrate concentrations in the Gulf of Mexico they have more than tripled since the 1950s and during that same time we've had a six-fold increase in the use of nitrogen fertilizers and so the increase in the amount of nitrogen that we see in the Gulf of Mexico is related to the use of nitrogen and the increase in the use of nitrogen from agricultural systems the amount of nitrogen in the Gulf of Mexico has been related to several land use and environmental factors first of all the annual use of fertilizer within the basin over the two previous years can account for 68 percent of the variation in nitrogen that we see in the Gulf of Mexico this means that basically fertilizer use in the basin accounts for about 70 percent of the nitrogen that we see in the Gulf of Mexico the current years stream discharge would be expected to also contribute nitrogen because it would be flushing fertilizers and nutrients from the terrestrial ecosystems and we see that stream discharge or the river flow of the Mississippi River accounted for approximately 20 percent actually 18 percent of the variance in nitrogen in the Gulf of Mexico and so these two major factors the use of fertilizers through land use and the flow of the Mississippi River can account for the majority of the nitrogen in the Gulf of Mexico and we can see that these predictors can account for the patterns that we see from year to year in the amount of nitrogen present in the Gulf of Mexico the fertilizer use is related to the agricultural uses and so we see that the areas of extremely high fertilizer use are located in the central portion of the Mississippi River drainage the pointer here will show that this central area that you see in red is one of the areas of highest fertilizer use this also happens to be one of the areas of highest production of of corn and other crops and the central area also where we see high fertilizer use tends to have the highest concentrations of nitrate in stream water and surface waters and so the highest fertilizer use is also the same area that we see the highest concentrations of nitrate in the streams and rivers of the Mississippi River drainage so how can we manage for such a huge land use problem the management of the Mississippi alluvial valley that we see here along the main stem of the Mississippi River is one of the ways that we can help reduce the amount of nitrogen loading into the Gulf of Mexico there have been many many changes in the Mississippi River system over the last several hundred years we've seen levees being formed putting the stream in a narrow pipeline we see wing dams preventing the stream from moving off into its banks and floodplains we see other structural improvements for the river channel that are intended to control the channel and protect the land but actually at the expense of the river and floodplain function we see cutoffs uh of the main of the meandering Mississippi River system so that basically the river has been straightened and simplified and so we see that the Mississippi River system has lost approximately 150 miles of its length by cutting through its meanders and straightening the river and so we've taken a river that was once complex and meandering and braided and a major nutrient uptake feature of the landscape and turned it into a pipe so that it conveys those nutrients rapidly without taking them up and that we've seen the clearing of the forest associated with this floodplain approximately 80 percent of the forest that once existed on the floodplain of the Mississippi River system has been harvested or converted to other land uses and so we've lost forested wetlands and and floodplain forest one of the ways that we can manage for nutrients in the alluvial valley of the Mississippi River is to protect the good stuff the good habitats and so we maintain the intact habitats and systems rather than trying to put them back together after we've altered them so in a system like this we find conservation easements and other practices that will help us restore or maintain the important parts of the system that are still functioning the restoration of wetland plants and hydrology to conditions prior to conversion is one of the major ways for increasing the ability of these floodplain systems to take up nutrients and so as we get flooded floodplain forests we get a tremendous ability of that biological system to take up the nutrients that are moving down the Mississippi River system also in our agricultural practices we can do things to keep the soil on the land and maintain natural processes of nutrient uptake this has been done in the Mississippi River system particularly through some of the rice farmers through maintaining flooded fields so that the flooded conditions of these flood plains and wetlands is maintained providing habitat for wildlife and also providing for retention of nutrients and keeping the soil in place on the land so instead of it being dry and then having range occur across it and eroding it we maintain the flooding conditions so that the soils are not being eroded away constantly by these sudden storms and so we see as a result of these practices in the winter of 1999 and 2000 more than 50 000 tons of soil were conserved by maintaining the floodplain processes on these agricultural systems this has direct bearing on water quality in these receiving waters now the Gulf of Mexico is not the only place in the United States where we have problems with hypoxia or low dissolved oxygen we see that all of our coastlines from the east coast to the Gulf of Mexico to the west coast have areas of widespread low dissolved oxygen concentrations that are related to land use activities so this is not just a problem for the Mississippi River system in Oregon for example in the Willamette Basin we can see that nitrate concentrations in groundwater are extremely high and with the pointer you'll notice that in this is the Willamette River basin which and the Willamette River flows north toward Portland into the Columbia River and it flows on out to the Pacific Ocean in the northern end of the valley near Portland we see very high concentrations of nitrate in groundwater and some of the highest concentrations that are observed are in the areas very close to Portland where we have high production of crop lands and high use of fertilizers so what are the solutions to the nutrient loading that we see throughout the United States related to all of our land use practices one of the solutions is to manage for better own farm practices the application rate of fertilizers is an important component of reducing nutrient loading to lower the application rates to the amount that's necessary for the crop production but not in excess of the crop production is one of the ways to maintain productive farms but lower the amount of water pollution so the idea of having the added insurance of well if it needs a little bit of fertilizer twice as much must be that much better avoid that because it costs the farmer money and it results in excess nutrients going into the surface waters the other is to account for the residual fertilizer the amount that's input by legumes and other natural sources or other agricultural sources and so consider the amount of fertilizer that's already present within the system in your management and consider the amount of fertilizer that's being applied with manure management or waste applications and so by lowering the amount of fertilizer application considering the amount of residual fertilizer and considering the amount that's coming in to mature in manure or animal waste are one of the ways that we can start to reduce the amount of nutrient loading in the Mississippi River system though this accounted for only about 15 to 20 percent reduction in nitrate coming out of the Mississippi River system as they modeled the nutrient dynamics of the Mississippi River so the own farm practices are very important but it's only a part of the solution another major solution for the nutrient loading problems in the Mississippi River system has been the conservation and restoration of wetlands and riparian areas one of the most effective nutrient filters or barriers in agricultural regions are the wetlands and riparian forests along streams and rivers and lakes in the Mississippi River Valley more than five million acres of wetland have been restored and more than 19 million acres of riparian forests have been restored these two sources of riparian restoration provide an additional 40 percent reduction in the nitrate that is going into the Gulf of Mexico so both the reduction of application of fertilizers and the management of nutrients on the croplands the own farm processes and the protection and restoration of wetlands and riparian areas can reduce the amount of nitrogen going into the Gulf of Mexico by approximately 60 percent so we see that under cropland systems in the Mississippi River as rain hits the land it washes fertilizers into the streams and rivers delivering increased nutrients to the Gulf of Mexico but where we reconnect the complex channels of the flood plains and restore the wetlands and forests of the Mississippi River system to their functional ecological conditions we can see that this process changes as the rain hits it is soaked up into the soil the nutrients are taken up by the natural vegetation and the amount of nitrogen that reaches the Gulf of Mexico is far less and so as we see our landscapes we see that the supply of nutrients into our terrestrial and aquatic ecosystem is a major determinant of the biological characteristics of these ecosystems you cannot understand the biological communities of a stream a lake a river a grassland a forest a woodland unless you understand the nutrients that support all of those living organisms and so it's the management of both the natural processes that cycle nutrients and the loading of nutrients into these systems through both natural and human related processes that determines the productivity of the lands that we see this is true in forested lands uh it's also true in urban lands and it's true in agricultural lands now where we have intact systems conserving those lands and conserving those functions can maintain higher water quality and help maintain the nutrient dynamics that will provide the ecosystems that we desire in agricultural systems providing for riparian buffers along streams and rivers and trying to conserve wetlands and riparian features and flood plains where possible will provide both natural resources and the potential to take up nutrients along these agricultural lands and so we see that the water quality of our nation's surface waters and the productivity of our terrestrial ecosystems is directly related to our land use practices understanding nutrients and their dynamics is essential for developing land use practices that will be effective in maintaining the productivity of the land protecting water quality and conserving our natural resources