Estuaries And Nutrients

Estuaries are eternally enriched. Their positions at the foot of watersheds and their convenience as receiving bodies for the wastes of cites, towns and farms results in continuous addition of nutrients - those elements and compounds which are essential for organic production. Such materials must be added to these complex bodies of water to sustain production, since there is a net loss of water and its contents to the oceans. Enrichment from land and the ocean and the subsequent cycling of the original chemicals or their derivatives contribute to the extraordinarily high values of estuaries for human purposes. Many estuaries are able to assimilate large quantities of nutrients despite the great fluctuations which occur with variations in the flow from tributaries. The nutrients can be stored, incorporated in standing crops of plants, released, cycled and exported - and the system frequently achieves high production of plants and and animals without creation of any undesirable results of enrichment. Excessive enrichment with the same elements and compounds can, however, be highly detrimental to estuaries and their uses. Coastal cities are usually located on the estuaries which provided a harbor for the- and which now receive partially treated sewage and other wastes from the expanding population and industrial activity. Conversion of woodlands to agricultural use and the extensive application of fertilizers have resulted in the flow of large quantities of nutrients down the hill or slopes and eventually into the estuary.

This volume focuses on the nutrient and organic matter inputs in estuaries and other coastal ecosystems, their effects on geochemistry and community structure and possibilities for recovery of the systems to a trophic state that is beneficial for man and nature. The book provides many examples of the effects of the enhanced supply of nutrients and organic matter on the chemical features of the water and on the structure, metabolism and trophic pathways of the biological communities. Also included are several case studies providing considerable insight into the response of the different coastal ecosystems to long term changes in the trophic state of the water. Current knowledge on modeling as a tool to manage the trophic state of the coastal ecosystems is also dealt with, making this book one of interests to scientist and students as well as managers.

Environmental problems in coastal ecosystems can sometimes be attributed to excess nutrients flowing from upstream watersheds into estuarine settings. This nutrient over-enrichment can result in toxic algal blooms, shellfish poisoning, coral reef destruction, and other harmful outcomes. All U.S. coasts show signs of nutrient over-enrichment, and scientists predict worsening problems in the years ahead. Clean Coastal Waters explains technical aspects of nutrient over-enrichment and proposes both immediate local action by coastal managers and a longer-term national strategy incorporating policy design, classification of affected sites, law and regulation, coordination, and communication. Highlighting the Gulf of Mexico's "Dead Zone," the Pfiesteria outbreak in a tributary of Chesapeake Bay, and other cases, the book explains how nutrients work in the environment, why nitrogen is important, how enrichment turns into over-enrichment, and why some environments are especially susceptible. Economic as well as ecological impacts are examined. In addressing abatement strategies, the committee discusses the importance of monitoring sites, developing useful models of over-enrichment, and setting water quality goals. The book also reviews voluntary programs, mandatory controls, tax incentives, and other policy options for reducing the flow of nutrients from agricultural operations and other sources.

It is a well-known fact that eutrophication of coastal waters causes significant changes in the species composition of the primary producers. Usually a shift from an ecosystem dominated by sea grasses or large brown algae to an ecosystem dominated by fast-growing green algae or phytoplankton is observed. While this shift has been documented in a number of research papers and books, the consequences of this shift are less well known. This book focuses on the consequences of such changes for nutrient cycling. The aim is to investigate how different types of primary producers influence nutrient cycling in coastal marine waters, and how nutrient cycling changes qualitatively and quantitatively as a consequence of the changes in the primary producer community caused by eutrophication. The various chapters address specific ecological processes such as grazing, decomposition, burial and export of biomass from the ecosystem. The book is intended for researchers and professionals working in the field of coastal marine ecology and estuarine ecology and for advanced students in this field.