1 Unit - 3. Estuaries and Coastal Zone management 3.1. Estuarine and coastal environment:
An estuary is a partially enclosed body of water along the coast where freshwater from rivers and streams meets and mixes with salt water from the ocean. Estuaries and the lands surrounding them are places of transition from land to sea and freshwater to salt water. Although influenced by the tides, they are protected from the full force of ocean waves, winds, and storms by such land forms as barrier islands or peninsulas. Estuarine environments are among the most productive on earth, creating more organic matter each year than comparably-sized areas of forest, grassland, or agricultural land. The tidal, sheltered waters of estuaries also support unique communities of plants and animals especially adapted for life at the margin of the sea. Many different habitat types are found in and around estuaries, including shallow open waters, freshwater and salt marshes, swamps, sandy beaches, mud and sand flats, rocky shores, oyster reefs, mangrove forests, river deltas, tidal pools, and sea grasses.
Why are Estuaries Important?
Estuaries provide us a lot of resources, benefits, and services. Some of these can be measured in terms of money, others cannot. Estuaries provide places for recreational activities, scientific study, and aesthetic enjoyment. Estuaries are an irreplaceable natural resource that must be managed carefully for the mutual benefit of all who enjoy and depend on them. Thousands of species of birds, mammals, fish, and other wildlife depend on estuarine habitats as places to live, feed, and reproduce. And many marine organisms, including most commercially-important species of fish, depend on estuaries at some point during their development. Because they are biologically productive, estuaries provide ideal areas for migratory birds to rest and re-fuel during their long journeys. Because many species of fish and wildlife rely on the sheltered waters of estuaries as protected spawning places, estuaries are often called the "nurseries of the sea." Estuaries have important commercial value and their resources provide economic benefits for tourism, fisheries, and recreational activities. The protected coastal waters of estuaries also support important public infrastructure, serving as harbors and ports vital for shipping and transportation. Estuaries also perform other valuable services. Water draining from uplands carries sediments, nutrients, and other pollutants to estuaries. As the water flows through wetlands such as swamps and salt marshes, much of the sediments and pollutants are filtered out. This filtration process creates cleaner and clearer water, which benefits both people and marine life. Wetland plants and soils also act as natural buffers between the land and ocean, absorbing flood waters and dissipating storm surges. This protects upland habitat as well as valuable real estate from storm and flood damage. Salt marsh grasses and other estuarine plants also help prevent erosion and stabilize shorelines.
Why Protect Estuaries?
The economy of many coastal areas is based primarily on the natural beauty and bounty of estuaries. When those natural resources are imperiled, so too are the livelihoods of those who live and work in estuarine watersheds. Coastal counties are growing three times faster than counties elsewhere in the nation. Unfortunately, this increasing concentration of people upsets the natural balance of estuarine ecosystems, threatens their integrity, and imposes increased pressures on vital natural resources like estuaries. What happens on the land affects the quality of the water and health of the organisms that live in an estuary. For example, if a river or stream flows through an agricultural area, it picks up fertilizer, manure, and pesticides from farming operations that run off the land after a rainstorm. As it passes
2
urbanized and suburbanized areas, it gathers fertilizers or pet waste that wash off lawns, untreated sewage from failing septic tanks, wastewater discharges from industrial facilities, sediment from construction sites, and runoff from impervious surfaces like parking lots.
3.1.1. Classification and physico – chemical parameters of estuaries. Classification based on geomorphology
Drowned river valleys: The width-to-depth ratio of these estuaries is typically large, appearing wedge-shaped in the inner part and broadening and deepening seaward. Water depths rarely exceed 30 m (100 ft). Examples of this type of estuary in the U.S. are the Hudson River, Chesapeake Bay, and Delaware Bay along the Mid-Atlantic coast, and Galveston Bay and Tampa Bay along the Gulf Coast. San Francisco Bay is another good example of a drowned river valley.
Lagoon-type or bar-built: These estuaries are semi-isolated from ocean waters by barrier beaches (barrier islands and barrier spits). Formation of barrier beaches partially encloses the estuary, with only narrow inlets allowing contact with the ocean waters. Bar-built estuaries typically develop on gently sloping plains located along tectonically stable edges of continents and marginal sea coasts. They are extensive along the Atlantic and Gulf coasts of the U.S. in areas with active coastal deposition of sediments and where tidal ranges are less than 4 m (13 ft). Barrier beaches form in shallow water and are generally parallel to the shoreline, resulting in long, narrow estuaries. The average water depth is usually less than 5 m (16 ft), and rarely exceeds 10 m (33 ft). Examples of bar-built estuaries are Barnegat Bay, New Jersey; Laguna Madre, Texas; and Pamlico Sound, North Carolina.
Fjord-type: Fjord-type estuaries are formed in deeply eroded valleys formed by glaciers. These U-shaped estuaries typically have steep sides, rock bottoms, and underwater sills contoured by glacial movement. The estuary is shallowest at its mouth, where terminal glacial moraines or rock bars form sills that restrict water flow. In the upper reaches of the estuary, the depth can exceed 300 m (1,000 ft). In estuaries with very shallow sills, tidal oscillations only affect the water down to the depth of the sill, and the waters deeper than that may remain stagnant for a very long time, so there is only an occasional exchange of the deep water of the estuary with the ocean. If the sill depth is deep, water circulation is less restricted, and there is a slow but steady exchange of water between the estuary and the ocean. Fjord-type estuaries can be found along the coasts of Alaska, the Puget Sound region of western Washington State, British Columbia, eastern Canada, Greenland, Iceland, New Zealand, and Norway.
Tectonically produced: These estuaries are formed by subsidence or land cut off from the ocean by land movement associated with faulting, volcanoes, and landslides. Inundation from eustatic sea level rise during the Holocene Epoch has also contributed to the formation of these estuaries. There are only a small number of tectonically produced estuaries; one example is the San Francisco Bay, which was formed by the crustal movements of the San Andreas fault system causing the inundation of the lower reaches of the Sacramento and San Joaquin rivers.
3 3.1.2. Physico-Chemical Parameters
The most important variable characteristics of estuary water are the concentration of dissolved oxygen, salinity and sediment load. There is extreme spatial variability in salinity, with a range of near zero at the tidal limit of the tributary river(s) to 3.4% at the estuary mouth. At any one point the salinity will vary considerably over time and seasons, making it a harsh environment for organisms. Sediment often settles in intertidal mudflats which are extremely difficult to colonize. No points of attachment exist for algae, so vegetation based habitat is not established. Sediment can also clog feeding and respiratory structures of species, and special adaptations exist within mudflat species to cope with this problem. Lastly, dissolved oxygen variation can cause problems for life forms. Nutrient-rich sediment from man-made sources can promote primary production life cycles, perhaps leading to eventual decay removing the dissolved oxygen from the water; thus hypoxic or anoxic zones can develop.
3.1.3. Distribution of estuarine plankton, nekton and benthos.
Estuaries provide habitats for a large number of organisms and support very high productivity. Estuaries provide habitats for many fish nurseries, depending upon their locations in the world, such as salmon and sea trout. Also, migratory bird populations, such as the black-tailed godwit, Limosa limosa islandica make essential use of estuaries. Two of the main challenges of estuarine life are the variability in salinity and sedimentation. Many species of fish and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed osmoconformers and osmoregulators. Many animals also burrow to avoid predation and to live in the more stable sedimental environment. However, large numbers of bacteria are found within the sediment which have a very high oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions, which can be further exacerbated by limited water flux. Phytoplankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with the tides. Their productivity is largely dependent upon the turbidity of the water. The main phytoplankton present are diatoms and dinoflagellates which are abundant in the sediment. It is important to remember that a primary source of food for many organisms on estuaries, including bacteria, is detritus from the settlement of the sedimentation.
3.1.4. Estuarine birds, estuarine food web. Mangroves, sea-grasses, marine fungi.
Salt marsh species rely on the decay of marsh plants to supply a steady source of food in the form organic material, or detritus, resulting from the decomposition of plants and animals. Most marsh plants flourish in the spring and summer, growing taller and more abundant. In the fall, they begin to decay and are distributed within the same marsh or into other marshes and mudflats where they become the first level of the food chain. Microscopic organisms like bacteria, small algae, and fungi help decompose the detritus resulting from salt marsh plants. These microorganisms and the remaining decomposing plant material become an ideal source of food for bottom-dwellers in salt marshes like worms, fishes, crabs, and shrimps. The cycle continues when the feces of the bottom-dwellers is cleaned up by microorganisms. Anything left over is great fertilizer for the next spring, when the marsh plants fill the marsh with green lush leaves.
As with many food webs, microorganisms at the most primary level on the food chain are responsible for more than one role. The same microorganisms feeding on detritus cover the mud surface, stabilize sediments, feed larger animals, and add nutrients to the sediments. They feed on a variety of food sources in the marsh environment such as insects, seeds, fishes, fiddler crabs, and shrimps. It is common
4
to see these birds guarding the tide pools for any splash indicating a fiddler crab or other marsh delicacy. As with all of the marsh residents, birds contribute to the cycle by breaking down detritus and discarding organic material (feces) to fertilize marsh grass and be used by microorganisms. The leaves, stems, and roots of salt marsh plants provide a vital shelter from predators and nourishment for young fish, shrimps, and crabs. Without this environment, only a handful would survive. Among young salt marsh species are blue crab, spot tail bass, and white shrimp. Larger predators live in creeks waiting for the fish to come out of the marsh when the tide changes. Some marsh shrimps and fishes, including the mummichogs and grass shrimp, stay in potholes or standing pools of marsh water after the tide goes out. Several reptiles reside in the salt marsh habitat, including the most commonly found diamondback terrapin, a turtle that searches for food and lays its eggs when the tide comes into the marsh. Occasionally, American alligators can be found in the less salty waters of brackish salt marshes.
3.2. Marine and coastal living resources and their management.
Coastal wetlands and shallow near shore waters play an important role as nursery areas for shrimp and fish, and act, on the one hand, to moderate the impact of terrestrial activities on enclosed aquatic systems activities commonly manifested as pulses of nutrients, suspended sediments and toxic materials entering coastal and inland seas. At the same time, wetlands and near shore waters reduce the impact of the marine environment on terrestrial systems; this impact is manifested through such processes as storm surges, tsunamis and consequent coastal erosion. New tools and approaches, remote sensing and Geographic Information Systems (GIS) in particular, make the investigation of cross-boundary processes more feasible than ever before and deserve wide promotion since they help to provide a sound, geographically based, foundation for decision-making in the management of a complex environment. Estuaries play a major role in the life cycle of many economically important fish species by providing breeding, nursery and feeding grounds from which about 95% of the world's marine production is currently obtained. The accelerated degradation of these critical habitats by indiscriminate trawling, by land reclamation, drainage, coastal construction and mining and accompanying sediment deposition, threatens marine fisheries and wildlife and, in many areas, has already had destructive effects.
The following actions (in boldface), in some cases supported by complementary text (in lightface), were proposed in FAO (1991c) with respect to sustainable development of nearshore and estuarine areas: i. Classification and mapping of nearshore and estuarine areas in a Geographical Information System (GIS), showing their current multiple usage.
ii. Establishment of an inventory of particularly sensitive areas or critical habitats, which should be given special recognition in national legislation.
iii. The conservation of coastal wetlands and other areas of marine vegetation, as critical habitats for many commercial and non-commercial species, and as a means of maintaining biodiversity.
iv. Classification of proposed new developments and their consideration for approval only in the context of an Integrated Coastal Area Management (ICAM) Plan, according to an assigned priority of use, or mix of uses, with local inputs which can be shown to co-exist without damaging mutual impacts.
v. The formal control of access to coastal resources and environments, with mechanisms ranging from seasonal and permanent closure of areas to exploitation, to assignment of specific and carefully
5
delimited user-rights to individuals or coastal communities whose livelihoods depend on the health of these resources.
vi. Definition and establishment of user-rights and responsibilities with respect to living marine resources, whether for harvesting or recreational purposes, including the right to legal redress in the event of adverse impacts on these resources and environments by third parties, and, if appropriate, a mechanism for transfer of user rights between bona fide users.
vii. The setting up of a management and consultative framework for users of the coastal resource and environment, within a legal context, subject to government guidelines.
viii. Severely restricted and controlled use of inshore waters and incoming rivers as points of dumping or discharge of unwanted materials.
ix. Governmental recognition and addressing of the impact on the marine resources and environment of human activities outside the immediate marine context is called for, and there is the need for specifically addressing these impacts.
x. Explicit recognition is needed, with respect to estuarine, anadromous and catadromous resources, of the impact of land-and water-use practices throughout each marine catchment basin (MCB).
xi. The separation and, to the extent possible, individual treatment of discharges of biodegradable organic material and nutrients, and of non-biodegradable and toxic wastes, into the aquatic and marine environments, should be allowed for. The discharge of toxic wastes into the aquatic environment directly, or via the atmosphere, should be forbidden.
xii. Reduction in the loss of nutrients and topsoil to aquatic systems requires the adoption of riparian measures along watercourses, by evaluating the role of flood plains, by preventing deforestation of the upper reaches of MCBs, and by conservation of wetlands in deltas.
xiii. Recognition that the normal estuarine or lagunar fauna and flora, flourishing runs of diadromous fishes, and coastal wetlands and wildlife, are the best indicators of the health of the aquatic system as a whole.
3.3.1. Coastal Zone Management:
Most of the material that is dumped in oceans today is dredged material (sediments) removed from the bottom of waterbodies to maintain the nation's navigation system for commercial, transportation, national defense, and recreational purposes. Several hundred million cubic yards of sediment are dredged from waterways, ports, and harbors each year for this purpose, and approximately 20 percent of this material is disposed of in the ocean. The remainder of the sediments are disposed of in inland waters, upland areas, or confined disposal areas adjacent to shorelines, or used beneficially. Other materials that are currently ocean disposed include fish wastes, human remains, and vessels.
Invasive species means an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. Invasive species are one of the largest threats to our terrestrial, coastal and freshwater ecosystems, as well as being a major global concern. Invasive species can affect aquatic ecosystems directly or by affecting the land in ways that harm aquatic ecosystems.
6
Invasive species represent the second leading cause of species extinction and loss of biodiversity in aquatic environments worldwide. They also result in considerable economic effects through direct economic losses and management/control costs, while dramatically altering ecosystems supporting commercial and recreational activities. Effects on aquatic ecosystems result in decreased native populations, modified water tables, changes in run-off dynamics and fire frequency, among other alterations. These ecological changes in turn impact many recreational and commercial activities dependent on aquatic ecosystems. Common sources of aquatic invasive species introduction include ballast water, hull fouling, aquaculture escapes, and accidental and/or intentional introductions, among others.
Discharges of sewage into our water bodies can come from many sources, including wastewater treatment facilities, runoff from livestock operations, and vessels. Nutrients, metals, solids, toxics, endocrine disrupters, and pathogens are among the types of pollutants present in sewage discharges, and, as such, these discharges have the potential to impair water quality, adversely affect aquatic environments, and increase risks to human health. While sewage discharges have potentially wide-ranging impacts on all aquatic environments, the impacts may be especially problematic in marinas, slow moving rivers, lakes, and other bodies of water with low flushing rates.
3.3.2. Impact of dredging, mining and pollution on coastal habitats and their management methods. In 1972, the Marine Protection, Research, and Sanctuaries Act came into being to prohibit the dumping of material into the ocean that would unreasonably degrade or endanger human health or the marine environment. Virtually all material ocean dumped today is dredged material (sediments) removed from the bottom of waterbodies in order to maintain navigation channels and berthing areas. Other materials that are currently ocean disposed include fish wastes, human remains, and vessels. Ocean dumping cannot occur unless a permit is issued under the MPRSA.
WHAT TYPE OF MATERIAL IS PERMITTED TO BE DUMPED INTO THE OCEAN? : Virtually all material ocean dumped is uncontaminated dredged material (sediment) removed from the bottom of waterbodies to maintain navigation channels and docks. Other materials that are dumped include vessels, fish wastes, and human remains.
HOW IS OCEAN DUMPING REGULATED? Ocean dumping cannot occur unless a permit is issued by the Govt.
HOW ARE MATERIALS EVALUATED FOR OCEAN DUMPING?
Dredged materials, as well as other materials proposed for ocean disposal, must undergo a series of tests and evaluations to determine whether they meet environmental criteria for ocean dumping.
The testing and evaluation procedures are designed to protect against toxicity and bioaccumulation that may adversely impact the marine environment or human health, and to produce information about the potential for these effects efficiently and reliably.
No permit may be issued unless there is enough information to make a scientifically sound determination that the ocean dumping will not unreasonably degrade human health or the environment.
7
HOW ARE OCEAN DUMPING SITES MANAGED AND MONITORED?
Ocean dredged material disposal sites are required to have a site management and monitoring plan.
Sites are monitored to ensure that dumping will not unreasonably degrade or endanger human health or the environment, to verify that unanticipated adverse effects are not occurring from past or continued use of the site, and to ensure that permit terms are met.
HOW CAN WE REDUCE THE AMOUNT OF DREDGED MATERIAL DUMPED IN THE OCEAN? Decreasing the amount of material produced is one approach.
Removing the need for disposal is another approach. Dredged material is a valuable resource that can be used for a variety of beneficial uses, including wetland restoration, beach nourishment, shoreline construction, and habitat creation.
3.4. Remote sensing application in coastal zone management. Coastal zone regulations.
Significant environmental impacts to coastal and ocean ecosystems occur via direct pollution from vessels, and as a vector for the invasion of non-indigenous species. Pollution from recreational, commercial, and military vessels emanates from a variety of sources, and include: gray water, bilge water, black water (sewage), ballast water, anti-fouling paints (and their leachate), hazardous materials, and municipal and commercial garbage and other wastes. The coastal zone represents varied and highly productive ecosystem such as mangroves, coral reefs, sea grasses and sand dunes. These ecosystems are under pressure on account of increased anthropogenic activity on the coast, as a result of rapid urbanization, more industrial and recreational activities. It is necessary to protect these coastal ecosystems to ensure sustainable development. Remote sensing data, especially from IRS series, in conjunction with Geographical Information System (GIS) could generate data required for micro and macro-level planning of coastal zone management. RS and GIS could be used in creating baseline inventory of mapping and monitoring coastal resources, selecting sites for brackish water aquaculture, detecting shoreline changes, studying coastal land forms, estimating suspended sediments concentration and in assessing changes in coastal environmental conditions. Satellite based maps provide information on status of wetlands, mangroves, sea coast and coral reefs which has been useful in further planning conservation measures. The combination of moderate and high-resolution data provides a detailed land use maps at different scales for implementing coastal regulation measures. The paper describes on the development of an information system that could be used as a regulating, management and decision-making tool vis-à-vis development activities along the coastal stretches of India. GIS based Coastal Information System (CIS) could be developed using high resolution CARTOSAT or Resourcesat LISS III and PAN merged products for specific dates and other non-spatial data like topographical maps, IN charts, revenue maps, census records etc. Management and regulation in coastal stretches could be greatly aided by this CIS, if made available for general use or on internet, it can immensely help central as well as state government organizations to plan their activities properly and efficiently thus avoiding delays in project implementation.
