Aquatic ecosystem

About: Aquatic ecosystem is a research topic. Over the lifetime, 6658 publications have been published within this topic receiving 247899 citations.

Nonpoint pollution of surface waters with phosphorus and nitrogen

Abstract: Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes. Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by overenrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems. If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters. From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow.

Limnology: Lake and River Ecosystems

Abstract: Preface 1 Prologue 2 Water as a Substance 3 Rivers and Lakes - Their Distribution, Origins, and Forms 4 Water Economy 5 Light in Inland Waters 6 Fate of Heat 7 Water Movements 8 Structure and Productivity of Aquatic Ecosystems 9 Oxygen 10 Salinity of Inland Waters 11 The Inorganic Carbon Complex 12 The Nitrogen Cycle 13 The Phosphorus Cycle 14 Iron, Sulfer, and Silica Cycles 15 Planktonic Communities: Algae and Cyanobacteria 16 Plantonic Communities: Zooplankton and their Interactions with Fish 17 Bacterioplankton 18 Land-Water Interfaces: Larger Plants 19 Land-Water Interfaces: Attached Microorganisms, Littoral Algae, and Zooplankton 20 Shallow Lakes and Ponds 21 Sediments and Microflora 22 Benthic Animals and Fish Communities 23 Detrirus: Organic Carbon Cycling and Ecosystem Metabolism 24 Past Productivity: Paleolimnology 25 The Ontogeny of Inland Aquatic Ecosystmes 26 Inland waters: Understanding is Essential for the Future References Appendix Index

Light and photosynthesis in aquatic ecosystems

Abstract: Preface to the third edition Part I. The Underwater Light Field: 1. Concepts of hydrologic optics 2. Incident solar radiation 3. Absorption of light within the aquatic medium 4. Scattering of light within the aquatic medium 5. Characterizing the underwater light field 6. The nature of the underwater light field 7. Remote sensing of the aquatic environment Part II. Photosynthesis in the Aquatic Environment: 8. The photosynthetic apparatus of aquatic plants 9. Light capture by aquatic plants 10. Photosynthesis as a function of the incident light 11. Photosynthesis in the aquatic environment 12. Ecological strategies References and author index Index to symbols Index to organisms Index to water bodies Subject index.

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget

Abstract: Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.

The Chemistry of Submerged Soils

Abstract: Publisher Summary This chapter discusses the chemistry of submerged soils. The chemical changes in the submerged materials influence: (a) the character of the sediment or soil that forms, (b) the suitability of wet soils for crops, (c) the distribution of plant species around lakes and streams and in estuaries, deltas, and marine flood plains, (d) the quality and quantity of aquatic life, and (e) the capacity of lakes and seas to serve as sinks for terrestrial wastes. The single electrochemical property that serves to distinguish a submerged soil from a well-drained soil is its redox potential. The redox potential of a soil or sediment provides a quick, useful, semiquantitative measure of its oxidation–reduction status. Two recent developments have stimulated interest in the chemistry of submerged soils: the breeding of lowland rice varieties, with a high yield potential, and the pollution of streams, lakes, and seas, by domestic, agricultural, and industrial wastes. The chemistry of submerged soils is valuable: (a) in understanding the soil problems, limiting the performance of high-yielding rice varieties, and (b) in assessing the role of lake, estuarine, and ocean sediments as reservoirs of nutrients for aquatic plants and as sinks for terrestrial wastes.