COASTLINES ESTRARIES AND OCEANS COASTLINES Coastal Erosion Problems
COASTLINES, ESTRARIES AND OCEANS COASTLINES Coastal Erosion Problems Rise of the Oceans have been rising since the end of the last ice age, about 11, 000 years ago. The rate has accelerated in the last century. Over the last 100 years, global sea level has risen by about 10 to 25 cm (9. 8 ft. ). Some scientists believe the accelerated rate has been caused by the warming of the atmosphere resulting from increasing CO 2 levels from burning fossil fuels (greenhouse effect). Others disagree. Dam Construction Deltas and beaches may disappear when dams are built that block the flow of water that carries millions of tons of sediment to the river mouths.
Land Subsidence Extraction of oil in coastal regions, and water from aquifers in Louisiana, Texas, and California, have cause land subsidence. In Louisiana, the land has subsided 3 ft. in the past 100 years. Coastal Development Dredging and construction causes soil disturbance along coastlines and disruption of natural sedimentation and erosional processes. Control of Erosion Control Structures Piles of rocks and boulders (riprap) placed along the shoreline to intercept waves. Groins - Piers of stones placed about 100 ft. apart extending into the ocean at right angles to the shoreline. These trap sand moved by longshore currents. While they induce sedimentation in areas where they are constricted, they deprive shores located down current from them.
Beach Nourishment Sand may be trucked to eroded beaches. This can be very costly. In 1993, the US Army Corps of Engineers proposed to replenish a 34 -mile stretch of coastline in New Jersey with sand pumped from offshore. The price was an estimated $1. 8 billion and would form a beach 100 ft. wide that would last for an estimated 50 years. Vegetative Erosion Control Patches of the salt tolerant cord grass, Spartina, have been planted in the shallow waters near the coastline of Galveston Bay. The grass forms a living buffer against the erosive action of the waves. Restriction of Coastal Development One of the biggest human causes of coastal erosion is shoreline disturbance from extensive coastal development. A number of states have adopted legislation to control erosion-inducing construction. In North Carolina, new buildings must be located at least 120 ft. inland from the first line of dunes.
ESTUARINE ENVIRONMENT Features of Estuaries Transitional zones between rivers and oceans Influenced by river and tidal currents Salinities typically lower than the ocean and variable. Influenced by tidal bore and river flow. Water level rises and falls with tides DO 2 generally high because of turbulence Turbidity usually high (stirring action of tides and sediment load) Nutrient levels high “nutrient traps” Energy is supplied by phytoplankton, macrophytes, and detritus. The importance of phytoplankton depends on current velocity. Importance of Estuaries They are important to the marine fisheries industry Nursery grounds for commercially important fish and invertebrates. About 60% of marine fish harvested in America spend part of their time in the estuary. 98% of fish taken in Gulf of Mexico are estuarine and salt marsh dependant.
Food shelter and breeding sites for water fowl. Act as natural filtering systems for organics from industrial and domestic sewage (14 acres of estuary has the pollution-reducing effect of a $1 million waste treatment plant. Destruction of Estuarine Habitat and Coastal Wetlands Dredging and filling - to deepen channels for navigation and create waterfront for industrial, residential and industrial sites. Dams - block the intrusion of fresh water and raises salinity. Siltation - from mining, agriculture and lumbering. Industrial chemicals - from chemical plants and other industry. Organic pollution - from domestic and industrial sewage. Calefaction - from power plans and industry Restoration of Estuarine and Coastal Wetlands The Corps of Engineers has launched a project to divert fresh water from the Mississippi river into Louisiana wetlands and estuaries to check saltwater intrusion. They have also used sediment from river channels to create new marshes. They have created 3, 000 acres in the Gulf region. These gains are insignificant when compared to the current rate of destruction.
OCEAN ENVIRONMENT Serves Human Needs Limitless supply of water (32 million cubic miles) Phytoplankton contribute more oxygen to the atmosphere that all land plants. Oceans absorb 20 times more CO 2 than all the earth’s vegetation. Serves as a highway for international transport Provides important source of protein for many people. Ocean bottom is a valuable mineral resource. Major Ecological Features Extent - Covers 70% of the earth’s surface Depth - 11 kilometers (6. 5 miles) Salinity - Average in open ocean - 35‰ Circulation - Surface currents modify temperatures of adjacent coastlands and influence the distribution of marine biota. Vertical currents bring up nutrient-rich bottom waters replenishing surface waters for phytoplankton photosynthesis.
Zonation of Ocean Environments (see web site for “classification of marine environments”) Pelagic - water column Benthic - bottom Neritic - Water column over the continental shelf. It is a relatively warm, shallow-water region rich in nutrients supplied by upwellings and river discharges. In shallower zones there attached plants. There is great habitat diversity supporting a rich and diverse population of animals. The amount of biomass in the neritic is greater per unit volume than any other part of the ocean. Oceanic - The pelagic environment beyond the continental shelves, also called the “open ocean”. The upper photic zone overlies an immense zone where there is no light called the aphotic zone. The photic zone is divisible into the euphotic where there is sufficient light for photosynthesis, and the dysphotic where there is light, but not enough for photosynthesis. Oceanic waters of the euphotic are called the epipelagic and those of the dysphotic, the mesopelagic. The aphotic zone is divided into an upper bathypelagic (between 10 and 4°C isotherms) and a lower abyssopelagic. The abyssopelagic begins at the 4°C isotherm (2000 - 4000 M). Depths below 6000 meters are called hadal.
Subzones of the Continental shelf The continental shelf exists around the margins of land masses. It extends from low tide to a depth where there is a marked increase in slope. It usually occurs between 120 and 200 meters but may range from 20 - 550 M. The width of the shelf varies from almost nothing off southern Florida to over 800 km wide in the Arctic Ocean north of Siberia. The shelf is subdivided into three principal zones based on the tides. The supralittoral (supratidal), which is above the highest tides and the sublittoral (subtidal), which is never uncovered by low tide. The area of the shelf that is covered and uncovered by the tides is called the littoral, or intertidal zone. The littoral zone may be subdivided into three subzones according to the degree of tidal exposure. The midlittoral is the mid-tide zone that is covered and uncovered daily. The upper littoral that is covered only by the highest spring tides is called the supralittoral fringe zone, and the lower littoral that is only uncovered by the lowest spring tides is called the sublittoral fringe zone. These zones are characterized by specific communities of organisms that are zoned according to their ability to withstand different lengths of exposure and submergence. Zones are commonly named after the dominant community, or color. (Barnacle Zone, Laminarian Zone, Black Zone, Yellow Zone, etc. ).
Beyond the Shelf Most of the ocean bottom lies between 2000 and 4000 M (abyssal plains) Between the continental and the abyssal bottom is the continental slope (bathyal zone). The shelf and slope may be cut by submarine canyons. Organisms occupying abyssal depths must be adapted to withstand great hydrostatic pressures and extreme cold. Temperatures may be as low as 2°C. There is very little food on abyssal bottoms because of its distance from the photosynthetic zone. This results in very sparse populations of abyssal benthos except in areas of hydrothermal vents where the release of H 2 S provides a chemosynthetic base for a food web. Here chemosynthetic bacteria utilize the H 2 S, converting it to biomass which supplies an organic source to the community. Pollution of the Oceans Because of their vastness, oceans are the last reasonably uncontaminated environment on earth. In recent years, we have come to realize that the oceans are not infinite in their capacity to absorb wastes. Major ocean pollutants include: oil, sewage, garbage, chemicals, pesticides, radioactive wastes and dredge spoil. -
A. Oil Pollution Crude oil released into the ocean usually floats although some components may sink. Away from land it probably has little effect except on marine birds. Oil coats the feathers of birds and they loose their insulating qualities and birds die of exposure. Inshore oil spills may smother communities by coating shallow intertidal and subtidal areas. Initially devastation is nearly total, but recovery usually occurs with time. Sometimes the chemicals and detergents used to break up and disperse the oil can be more harmful to marine life than the oil. Sources of Oil Pollution Accidents Involving Tankers - Although these spills are the most dramatic, they account for only 5% of the oil that enters the ocean. It was the breakup of the Torrey Canon off the British Coast in 1968 that first alerted the general public to the problem (36 million gallons). One of the most published spills occurred on March 24, 1989, in Alaska’s Prince William Sound near the Port of Valdez. Exxon’s supertanker ran aground on a reef spilling 11 million gallons of oil. The oil spread quickly, and by the end of the summer had polluted 1400 miles of shoreline. This spill was not the largest, but will go down as one of the most costly both economically and environmentally.
The severity of the damage can be attributed to four key factors: 1. 2. 3. 4. The spill occurred in relatively protected waters close to land. Cleanup was delayed for several days. The cold water retarded biological degradation of the oil. The pristine waters were extraordinarily rich in marine life. Offshore Well Accidents - In 1969, faulty drilling techniques resulted in the release of thousands of gallons of oil off the coast of Santa Barbara, Calif. In 1979, an oil well blowout occurred in the Bay of Campeche, off Mexico’s East Coast. Oil escaped from the well for several months threatening marine life along Texas shores. Inland Sources - 30 -40% of the oil that enters the ocean comes from inland sources. Major contributors are service stations, motor vehicles, and factories. Until recently much of the oil from service station was discharged into sewers and eventually found its way to the ocean. Airborne hydrocarbons from factories and vehicles are washed from the air into the ocean. About 20 million metric tons of airborne petroleum hydrocarbons inters the sea annually. Deliberate Pollution by Lunatics - In 1991, There was a deliberate oil spill in the Persian Gulf by the Iraqi army releasing stored Kuwaiti crude oil.
Effects of Oil Pollution Effects vary according to: 1. 2. 3. 4. 5. 6. Amount and type of oil (crude, refined, etc. ) Proximity to the organisms Season of the year Weather Ocean currents Wind velocity Common Effects are: 1. Reduction of photosynthesis (disruption of food and O 2 prod. ) 2. Mortality of marine animals. Most spills are in the neritic zone where virtually all of our shellfish (oysters lobsters, shrimp), and half of our commercial fish crop is produced. 3. Food chain contamination with carcinogens. Crude oil is a complex of many different hydrocarbons, such as, benzopyrene, a reported cancer-producing material. 4. Disruption of chemical communication in marine mammals. Several of the hydrocarbons in crude oil mimic chemicals used by marine mammals to guide them during mating, feeding, homing, and migrating.
5. Devastation of resort beaches and boat basins Even after the more obvious effects of a spill are cleaned up, oil residues continue to spread through the ocean floor sediments for months, and the toxic effects may last for years. Tar balls can form from the heavier components and also tiny spherules of plastic, known as suspension beads. Control of Oil Pollution Input Controls • Upgrading of oil tankers and offshore wells. • More thorough inspections of tankers and offshore wells. • Stricter laws for dumping. Output Controls 1. Use of fingerprinting to determine source of the spill. 2. Soaking up oil with straw and absorbent material. 3. Decomposing oil with bacteria. 4. Using oil skimmers.
B. Sewage and Garbage The discharge of human sewage and garbage into coastal waters is practiced throughout the world. The sewage may or may not have had treatment before discharge. In small volume and with adequate diffusion pipes, it is difficult to detect any long-term effects on the animal communities of the open coast. In large volume and in semi-enclosed bays, the effects can be devastating. In the US, one of the worst polluted sites is the New York Bite. The Bite is a relatively shallow area over the continental shelf opposite New York Bay. It was used for a dumping ground for sludge and other wastes for more than 60 years. In the early 70’s, more than 1. 8 billion gallons of sewage sludge was discharged through 130 pipes into the Bite each year. More than 16% of this sewage had received no treatment. Raw sewage from 23 New Jersey towns also entered the bite. The bottom was covered with a thick layer of black sludge 40 square miles in area. The blanket was contaminated with toxic metals, organic compounds (PCB’s), viruses, and pathogenic bacteria. In 1988, The US Congress agreed to ban all ocean dumping as of Jan. 1, 1992.
C. Chemicals Many toxic chemicals produced by industrialized nations find their way into the oceans. These chemicals are often transferred through the food chain and exert their effects on animals in places far removed from the source. Some chemicals, because of their long half-life, may concentrate as they move through the food chains by “biological magnification”. This process can lead to significant levels in the “top carnivore”. There has been many documented cases of poisoning from heavy metals (mercury) and pesticides (DDT) concentrated through biomagnification in food chains. Chemicals can also be transported long distances via food chains. DDT has been found in the tissues of penguins of the Antarctic even though this pesticide has never been used on the continent. D. Radioactive Wastes Since 1944, the world’s oceans have been receiving an input of radioactive wastes generated from the production of nuclear weapons and electric power. Major sources have been fallout from nuclear weapons tests, dumping of wastes from nuclear fuel systems, and certain accidents.
One of the most significant contributions was the 1964 incident involving an aerospace nuclear generator that reentered the atmosphere when the launch malfunctioned. It deposited a quantity of plutonium 238 in the ocean equal to half the total oceanic deposits. There are two categories of radioactive wastes: high level and low level. Low-level wastes contain less than 1 X 10 -8 curies of radioactivity per gram, and high-level wastes contain more than 1 X 10 -8 curies per gram. Presently, dumping high-level wastes is prohibited by international agreement, but dumping low-level wastes is permitted. Low-level dumpsites have been designated at various oceanic sites. Currently, the only active site in the US is off the East Coast. There is currently much debate over what to do with high-level nuclear wastes. Since they remain toxic to humans for thousands of years, it is necessary to find a disposal site that will be stable for an equivalent period of time, and beyond the reach of human tampering. One such place is the deep ocean, well away from the edges of the tectonic plates. The abyssal plains of the deep ocean is beyond regular current human activity. Other lesser pollution problems in the ocean include calefaction, dredge spoil, and plastics.
E. Thermal Pollution (Calefaction) Calefaction is a usually a localized problem. It affects coastal regions and estuaries. Calefaction is particularly important in estuaries since they are breeding and nursery grounds for many species that are important to humans. Elevated temperatures can disrupt spawning and breeding cycles and may exceed tolerance and ranges for developing larva and juveniles. F. Plastics can cause wildlife mortality by blocking digestive tracts, entanglinginduced drowning, and entangling-induced starvation. A US law that helps control plastic pollution is The Ocean Dumping Act, which bans plastic dumping from trash ships. G. Dredge Spoil Dredge spoil is sediment dredged from river bottoms to deepen channels for navigation. About 52 million cubic yards are dredged annually. There are few suitable sites for dumping dredge spoil. Unfortunately, about one in every three tons of dredge spoil is contaminated with urban and industrial wastes as well as wastes form agricultural runoff (PCB’s, heavy metals, organics, etc. ).
Under terms of the Marine Protection and Sanctuary Act, The US Army Corps of Engineers, which does most of the dredging, was charged with finding suitable disposal sites beyond the continental shelf where adverse effects on marine ecosystems would be minimized. Human Impact on Marine Fisheries The earliest use of the ocean by humans was probably for food. As late as the 1880’s, scientists such as T. X. Huxley believed that the major fisheries were inexhaustible. Since that time, technology has drastically improved the amount of fish that can be harvested by such things as: more powerful ships, more effective nets and traps, and electronic devices for detecting fish. The results has been the significant reduction of many fish populations and the disappearance or overexploitation of others at a time when increasing human populations are demanding more food. Major Fishing Areas The major fisheries are concentrated in neritic waters. The only major fisheries that operate in oceanic regions are those for tuna and whales.
Fisheries are concentrated in neritic waters because: 1) Inshore waters are much higher in primary productivity 2) It is more accessible for nets and traps because of its shallowness. 3) The lack of food in the deep sea precludes a large fish population. Could not sustain a fishery for very long. There is unequal distribution of fish over the continental shelf areas. The most productive are the shelf areas of northwest Europe, the coast of western South America and off Japan. The southern oceans and the tropics (except west coast of South America) contribute much less. Major Commercial Species Four Groups of Commercially Important Marine Animals. 1) Bony and cartilaginous fish 2) Marine mammals (whales, seals, sea lions) 3) Molluscs (mussels, clams, snails, squid, octopus) 4) Crustaceans (shrimp, crabs, lobsters)
Fish constitute the greatest tonnage and only a few make up the majority of the catches: herrings, sardines, and anchovies. SUSTAINABLE YIELD AND THE FUTURE In 1988, the total world fishery catch was 98. 4 million metric tons. Of this, 84. 6 million metric tons were marine fisheries. The total fish caught for human consumption represents about 1% of all human food, but 10% of the protein intake. Increases since 1983 have resulted from heavy fishing for certain unexploited fishes such as pollock and hake that are used mainly for fish meal. pollock Pacific hake What are the facts regarding the potential amount of food from the sea? 90% of the present fishing effort is concentrated on 7% of the world ocean area represented by the continental shelves.
The tremendous growth in world fisheries in the 1950’s and 60’s was due primarily to the introduction of modern fish-capturing and fish-handling gear, including factory ships, larger nets, and more accurate methods of handling fish. At the present time, most of the productive continental shelf areas have been fully exploited for existing fish stocks and many areas have been overfished. In recent years, there have been many examples of the decline in fish stocks of all types in all areas of the world. Some of these declines are clearly due to over exploitation. Signs of overfishing are normally a decline in average fish size and an increase in effort needed to produce the same amount of catch. What about the remaining 93% of the ocean? Whales are depleted. Currently the major oceanic fishery is for various tunas, swordfish, bill fish, etc. In 1987, these groups made up only 4% of the total fishery, and the tonnage (3. 44 million tons) was not a significant increase over previous years, suggesting that we are approaching the limit of tuna that may be caught without depleting the stocks.
Twenty years ago tuna stocks were considered nearly impossible to overfish, but the advent of purse seines dramatically changed that view in a few years. There is considerable concern today regarding the fish’s ability to sustain the current fishing pressure. Fishing abyssal depths in the ocean is not feasible since diminished food supplies would not allow the existence of sustainable fish stocks. OVEREXPLOITATION OF WHALES The most dramatic example of the demise of a fishery as a direct result of human overfishing is the whaling industry. Large scale whaling began in the North Atlantic in the 16 th century. At first methods were primitive and refuges from whalers existed for most species. However, the advent of long-ranged vessels and especially the harpoon gun with an explosive charge spelled the end of the whale stocks in the N. Atlantic and N. Pacific by 1900.
Attention then turned to the large stocks of baleen whales in the Antarctic region, where most whaling in the 20 th century has been concentrated. More technological advancements included huge factory ships, and airplanes, helicopters and radar to aid in locating the whales. These advances led to a greater slaughter in the first 60 years of this century than had been achieved by all the whaling efforts in all preceding centuries. The whaling industry is now dead.
Tragedy of Commons In 1968 Garrett Hardin published an article in Science called the “Tragedy of Commons” in which he pointed out that freedom of access to a common resource ultimately brings ruin. Whenever a resource is held in common by a large number of individuals, or political entities, each will try to maximize its own gain from that resource, ultimately depleting that resource. Open ocean fisheries lie in international waters and are held “in common” for the good of the world’s people. Countries that can, exploit these areas because it serves their own interests. They figure that if they don’t catch the fish another nation will. It was this type of short term greed that destroyed the whaling industry and the tuna industry may be next. Regulation The decline of fisheries due to the tragedy of common access and increased demand for food has led to friction among nations and handicapped attempts to regulate fisheries resources. Nations can only regulate the fisheries along their own continental margins. In the past, an individual nation’s jurisdiction was 12 miles. In recent years, some countries unilaterally acted to extend their limits out to 50 or 200 miles. This has caused confrontations such as the seizure and fining of many US tuna boats by Ecuador and Peru.
Recently, through the actions of the United Nations, a standard 200 -mile fishing zone was established for coastal nations. International agreement between nations for fishing regulations is more difficult to bring about, but there have been some that have worked. The oldest, is the International Fur Seal Treaty, established in 1911, between the US, Russia, Japan, and Canada to regulate the exploitation of the northern fur seal. Another success has been the International Halibut Commission, established in 1924 between Canada and the US to regulate the declining halibut industry. This was the first fish species to be conserved internationally. After establishing the Commission, the halibut stocks recovered. New Fisheries? There a few prospects for new fisheries but they may not be able to contribute significantly to the human food supply. Now that the numbers of baleen whales have been reduced to the point of extinction in the North Atlantic, a new fishery has developed for the “krill” (euphausiids) that constituted the food for the whales. Krill are large enough to be caught without resorting to small-mesh plankton nets. The most conservative estimates for stocks of krill are 50 million tons/year, but other estimates range up to 100 million tons/year, making this the largest of any unexploited fishery. euphausiid
In summary, it appears that, although the catches of marine fish have been increasing, it would appear that many current world fisheries are reaching a maximum and show signs of overexploitation. There are only limited amounts of increase to be expected from unexploited fisheries. Mariculture (marine aquaculture) There is evidence that culturing of marine organisms existed as far back as ancient Rome, but mariculture has never been a significant contributor to human food. Only in the last century has mariculture received wide recognition and undergone significant development. Mariculture is more technologically advanced in the industrialized nations of the northern hemisphere. At present, mariculture is confined to shallow coastal embayments or artificial ponds. Few marine species are cultured, and most either fetch a premium price or produce large amounts of biomass under intense culture. Shrimp and abalone, cultured in Japan fit the first category. The latter is oysters and mussels. Fish that are successfully cultured include several species of Pacific salmon. Currently, about six million tons of food per year are produced by aquaculture methods. Brackish water and marine fish constitute about 66% followed by seaweeds (17. 5%), molluscs (16. 2%) and crustaceans (0. 3%).
Farming and fishing the oceans will increasing have to compete with other aspects of exploitation that may not be compatible, such as, underwater mining and oil drilling. Most fisheries are in shelf areas close to land where they are subject to maximum influence of pollution and habitat alteration.
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