Mangroves and mangrove ecology

[Astronuc]

One of the more interesting families of plants are the mangroves.  There are a number of genus and species.  Mangroves are very important because they perform a number of critical functions in the tidal zones of many coastal areas between 32 N and 38 S latitude.

Magroves protect and preserve sensitive coastlines, including marshes and deltas.  The land is protected from waves that would simply wash land away.  In some areas, the mangroves provide nurseries for small coastal fish species and a variety of crustaceans.  The trees also provide a haven for sea birds.  Behind the mangroves forests are more conventional terrestrial forests that would be vulnerable without protection of the mangroves.

There are several programs around the world now dedicated to studying mangrove ecology and restoration of the mangrove forests that have been damaged by careless exploitation or simply destroyed for development of other industries.

From the Mangrove Action Project (http://www.earthisland.org/map/mngec.htm)

THE ECOLOGY OF MANGROVES

These complex ecosystems are found between the latitudes of 32 degrees north and 38 degrees south, along the tropical coasts of Africa, Australia, Asia, and the Americas. There are varying scientific classifications of what constitutes a mangrove plant. According to two reputable scientific studies, mangroves include approximately 16-24 families and 54-75 species. ((Tomlinson (1986) and Field (1995) respectively) The greatest diversity of mangrove species exists in Southeast Asia. For example, there are only twelve mangrove species in the New World and only four species of mangroves exist along portions of the coasts of the southern USA.

Mangrove forests literally live in two worlds at once, acting as the interface between land and sea. Mangroves help protect coastlines from erosion, storm damage, and wave action. The stability mangroves provide is of immense importance. They prevent shoreline erosion by acting as buffers and catch alluvial materials, thus stabilizing land elevation by sediment accretion that balances sediment loss. Vital coral reefs and sea grass beds are also protected from damaging siltation.

A primary factor of the natural environment that affects mangroves over the long term is sea level and its fluctuations. Other shorter-term factors are air temperature, salinity, ocean currents, storms, shore slope, and soil substrate. Most mangroves live on muddy soils, but they also grow on sand, peat, and coral rock. If tidal conditions are optimal, mangroves can flourish far inland, along the upper reaches of coastal estuaries.

Mangroves vary in height according to species and environment, from mere shrubs to 40 meter trees. The prop roots of some mangrove species, such as Rhizophora or "red mangrove", and the pneumataphores of others, such as Avicennia or "black mangrove" and "grey mangrove", contain many small "breathing" pores, called "lenticels." These allow oxygen to diffuse into the plant, and down to the underground roots by means of air space tissue in the cortex, called "aerenchyma." The lenticels are inactive during high tide.

Evolutionary adjustments to varying coastal marine environments have produced some astounding biological characteristics within mangrove plant communities. Certain species of mangroves exclude salt from their systems, others actually excrete the salt they take in via their leaves, roots, or branches. In salt excluding mangrove species , the mangrove root system is so effective in filtering out salt that a thirsty traveler could drink fresh water from a cut root, though the tree itself stands in saline soil.

Certain mangrove species can propagate successfully in a marine environment because of special adaptations. Through "viviparity," embryo germination begins on the tree itself; the tree later drops its developed embryos, called seedlings, which may take root in the soil beneath. Viviparity may have evolved as an adaptive mechanism to prepare the seedlings for long-distance dispersal, and survival and growth within a harsh saline environment. During this viviparous development, the propagules are nourished on the parent tree, thus accumulating the carbohydrates and other compounds required for later autonomous growth. The structural complexity achieved by the seedlings at this early stage of plant development helps acclimate the seedlings to extreme physical conditions which otherwise might preclude normal seed germination.

Another special adaptation is the dispersal of certain mangroves' "propagules" which hang from the branches of mature trees. These fall off and eventually take root in the soil surrounding the parent tree or are carried to distant shorelines. Depending on the species, these propagules may float for extended periods, up to a year, and still remain viable. Viviparity and the long-lived propagules allow these mangrove species to disperse over wide areas.

"Zonation" often characterizes mangrove forests. Certain tree species occupy particular areas, or niches, within the ecosystem. Some mangrove species occur close to shore, fringing islands and sheltered bays; others are found further inland, in estuaries influenced by tidal action.

THE GREATEST THREATS--AN ECOSYSTEM IN PERIL

Naturally resilient, mangrove forests have withstood severe storms and changing tides for many millennia, but they are now being devastated by modern encroachments. Today, mangrove forests are among the most threatened habitats in the world-- disappearing at an accelerating rate, yet with little public notice. Lenticels in the exposed portions of mangrove roots are highly susceptible to clogging by crude oil and other pollutants, attacks by parasites, and prolonged flooding from artificial dikes or causeways. Over time, environmental stress can kill large numbers of mangrove trees. In addition, the charcoal and timber industries have also severely impacted mangrove forests, as well as tourism and other coastal developments.

The rapidly expanding shrimp aquaculture industry poses the gravest threat to the world's remaining mangroves. Literally thousands of hectares of lush mangrove forests have been cleared to make room for the artificial shrimp ponds of this boom and bust industry. This highly volatile enterprise has grown exponentially over the last 15 years, leaving devastating ruin in its wake.

Until recently, mangrove forests have been classified by many governments and industries alike as "wastelands", or useless swamps. This erroneous designation has made it easier to exploit mangrove forests as cheap and unprotected sources of land and water for shrimp farming. The amount of mangrove forest destruction is alarming. Thailand has lost more than half of its mangrove forests since 1960. In the Philippines, mangroves have declined from an estimated 448,000 hectares in the 1920s to only 110,000 hectares by 1990. In Ecuador, estimates of mangrove loss range from 20% percent to nearly one half of Ecuador's once 362,000 ha. of mangrove forested coastline. The Muisne region of Ecuador alone has lost nearly 90% percent of its mangroves. Globally, as much as 50% percent of mangrove destruction in recent years has been due to clear cutting for shrimp farms.

TOWARDS SOLUTIONS--PROTECTING MANGROVE FORESTS

The failure of national governments to adequately regulate the shrimp industry, and the headlong rush of multilateral lending agencies to fund aquaculture development without meeting their own stated ecological and social criteria, are other important pieces to this unfortunate puzzle. The fate of remaining mangrove forests may now rest in the hands of the consumers from the wealthy nations that import these luxury shrimp products. Since a highly profitable and expanding market is the driving force behind the shrimp industry, a worldwide reduction in consumer demand for pond-raised shrimp is called for.

Meanwhile, stricter local governmental regulations and enforcement protecting mangroves are necessary. Also, involvement of local communities in sustainably managing and protecting their coastal resource base, including the nearby mangrove forests, is essential.

[Astronuc]

South Florida has a number of mangrove forests.

http://www.flmnh.ufl.edu/fish/southflorida/mangrove/Profiles.html#Red Mangrove

Growing along the edge of the shoreline where conditions are harshest, the red mangrove (Rhizophora mangle) is easily distinguished from other species by tangled, reddish prop roots. These prop roots originate from the trunk with roots growing downward from the branches. Extending three feet (1 m) or more above the surface of the soil, prop roots increase stability of the tree as well as oxygen supply to underground roots.

Under optimal conditions, this mangrove tree can grow to heights of over 80 feet (25 m), however, in Florida, red mangroves typically average 20 feet (6 m) in height. Habitat range in Florida is limited by temperature. Red mangroves occur from Cedar Key in the Gulf of Mexico and Daytona Beach in the Atlantic, southward through the Florida Keys. The smooth-edged, elliptical leaves have shiny, dark green uppersides and pale green undersides and occur opposite from each other along the branches. Trunks and limbs are covered with gray bark, over a dark red wood from which the common name originates. Clusters of white to pale yellow flowers bloom during the spring and early summer months.

Reproductive adaptations enable seedlings to germinate while still attached to the parent tree. Seeds sprout into 6 inch (15 cm), pencil-shaped propagules. Seed germination while still attached to the tree gives this mangrove a higher chance of survival. When the seedling falls into the water, it may either take root alongside its parent or be carried by the tides and currents to other suitable habitat.


Black Mangrove

Avicennia germinans, the black mangrove, is characterized by long horizontal roots and root-like projections known as pneumatophores. It grows at elevations slightly higher than the red mangrove where tidal change exposes the roots to air. The pencil-shaped pneumatophores originate from underground horizontal roots projecting from the soil around the tree's trunk, providing oxygen to the underground and underwater root systems.

The black mangrove reaches heights of over 65 feet (20 m) in some locations, however in Florida they are smaller with heights to 50 feet (15 m). Within Florida, they range from the Keys north to Cedar Key on the west coast and St. Augustine on the east coast. Leaves occur opposite of each other along the branches, with upper sides that are shiny and undersides densely covered with hairs. The bark of this mangrove is dark and scaly. Black mangroves blossom in spring and early summer, producing white flowers.

Reproductive adaptations enable seedlings to germinate while still attached to the parent tree. Seeds sprout into 1 inch (2-3 cm), lima bean-shaped propagules. Seed germination occurs while still attached to the parent tree, increasing the chances of survival in this adverse environment.


White Mangrove

Occupying higher land than the red and black mangroves, the white mangrove (Languncularia racemosa) has no visible aerial roots, unlike the black mangrove which has pneumatophores and the red mangrove with prop roots. However, when it is found in oxygen-depleted sediments or flooded for extended periods of time, it often develops peg roots.

White mangroves are the least cold-tolerant of the three mangrove species found in Florida, occurring from Levy County and Volusia County southward in Florida. This small tree or shrub grows rapidly in rich soils to heights of 50 feet (15 m). The light yellow-green leaves are broad and flat with two glands located at the base of the leaf where the stem originates. These glands excrete salts taken in through the underground root system. White mangroves produce greenish-white flowers in spikes, blooming from spring to early summer.


Buttonwood

Often found in the upland transitional zone, the buttonwood (Conocarpus erectus) is often associated with mangrove communities. Sensitivity to frost restricts its range to south Florida. The name buttonwood comes from the button-like appearance of the dense flower heads that grow in branched clusters, forming cone-like fruit. This plant does not reproduce via propagules, but instead producing seed cases. While the three mangrove species have leaves that occur opposite of each other, the buttonwood leaves alternate. The leaves are leathery with pointed tips and smooth edges. There are two salt-excreting glands located at the base of each leaf. Flowers appear in cone-like heads and are greenish in color.

[Astronuc]

In 1988, Dr. Gordon Sato initiated a project for Mangrove development in the small nation of Eritrea.  The objective was to significantly increase the supply of fish (silviculture) and eventually food for animals by developing mangrove forests along Eritrea's coastline.

--------------  The Manzanar Mangrove Initiative  -----------------

An economic, incentive driven approach to end global warming.

The object of the Manzanar Mangrove initiative is to create whole new forests of mangrove trees in vast areas of the world where mangrove trees do not grow at the present time. This will contribute to alleviating poverty in parts of the world and to diminishing the threat of global warming. Poverty would be alleviated by creating a renewable resource - mangrove trees which produce valuable timber, and by enriching the fish populations of adjacent seas. The mangrove forests would fix CO2 by photosynthesis into mangrove lumber and thus decrease the possibility of a catastrophic series of events - global warming by atmospheric CO2, melting of the polar ice caps, and inundation of the great coastal cities of the world.

How and where could this be achieved? The how is addressed by some simple considerations of hydroponics technology. Plants can be grown in an inert medium such as sand or even in water so long as certain conditions are fulfilled. The pH and salinity of the water must be at levels tolerated by the plant, the water must contain the mineral nutrients known to be required by plants, air must be provided to the roots, and the temperature range of the habitat must be tolerated by the plant. In short term experiments we have determined that mangrove trees can tolerate pH from 6 to 9. The pH of seawater is approximately 8. Mangroves grow in seawater, so obviously they can tolerate the salinity of seawater, and in fact can survive at salinity's a little higher than that of seawater. We have compared the composition of complex algae media to seawater and found that the only elements in short supply in seawater were nitrogen, phosphorus, and iron. If a flask of seawater is placed in the bright sun, algae grows slowly. If ammonium phosphate is added to the seawater, algae still grows slowly. If ammonium phosphate and iron are added to seawater, algae grow rapidly. This means that if a plant can grow in seawater, we only need to add ammonium phosphate and iron to satisfy its nutritional needs. This also means that mangrove trees can be grown where they now do not grow if the seawater is fortified with ammonium phosphate and iron.

Where can mangroves be grown where they now do not grow? We will consider three general categories of sites: intertidal zones, deserts above the high tide line, and sites such as the Aegean islands where the tidal variation is small.

Let us first consider the intertidal zone of the desert shores of Eritrea. Fifteen percent of the intertidal zone contains mangrove trees. Why should this be so? On examination it is found that the mangroves grow in mersas where the scant seasonal rains are channeled to enter the sea. Is it possible that the reasons the trees survive are because they have water of a lower salinity a few days each year. Highly unlikely! It is difficult to think of a mechanism to account for the survival of a tree only if it has water of lower salinity a few days a year. The rains also bring clay so the mersas contain heavy mud with decaying organic material. Is it possible that mangroves only grow in mersas because they need mud? This is unlikely because as mentioned before plants can grow in an inert supporting material if conditions of salinity, pH, mineral nutrients, etc. are satisfied. Our explanation for why trees grow in mersas is that the rains bring the nutrients from inland, and the vital nutrients are nitrogen, phosphorus, and iron. To test this hypothesis, mangrove seedlings were planted in a section of intertidal zone where no mangroves existed. After about three months, all of these seedlings (20) were dead. Another five hundred were planted in intertidal zones lacking mangrove trees, including a barren, dead coral reef This time each tree was provided with slow release fertilizer, consisting of diammonium phosphate and iron oxide. This was accomplished by placing about two hundred grams of diammonium phosphate, and ten grams of iron oxide in a plastic bag that was tied shut and punctured ten times with a ten penny nail. The bag was buried a few inches from the tree. With few exceptions these trees have survived and flourished - some for up to a year. We conclude that intertidal zones of coastal deserts in tropical and subtropical climes, which now contain no mangrove trees, can be filled with mangrove trees if seedlings are planted and provided with slow release fertilizer.

Eritrea has an intertidal zone approximately 1000 kilometers long and one hundred meters wide. At a density of 1000 trees per hectare, we could plant 10 million trees in the intertidal zone of Eritrea. If the entire Red Sea intertidal zone were planted we could plant about fifty million trees. Other desert intertidal zones also show great promise. The gulf of California has a tidal variation of about 6 meters, and therefore has an enormous intertidal zone of about a kilometer in width. The shore line of the gulf of California is about two thousand kilometers long, so about two hundred million mangroves could be planted in the intertidal zone of the gulf of California,

What are the economic benefits, and what are the costs of planting desert intertidal zones in tropical and subtropical regions? First of all fish production would increase in adjacent seas. Secondly, if mangroves such as Rhizophera, which produce valuable lumber were planted, a valuable renewable resource would be established. Finally the economic benefit of averting global warming, melting of the polar ice caps, and flooding of the worlds harbor cities are enormous. The value of the tree after twenty years would be roughly 100 USD, and as lumber about 400 USD. Eritrea's ten thousand hectares of intertidal zone could produce four billion USD in twenty years or 200 million USD per year. Mexico's 200 thousand hectares of intertidal zone on the Gulf of California could produce four billion USD per year. This would be powerful economic incentive for such countries to do their share as world citizens to avert the global catastrophe threatened by global warming. The cost of such a program would be mostly labor. We calculate it would require about one man-hour per tree to plant and tend the tree for twenty years. This would include gathering the propagules, growing them in small plastic bags in a nursery, transplanting the trees, and applying once a year a slow release fertilizer. We calculate that the trees would require about ten kilograms of diammonium phosphate over the twenty years at a cost of about two USD per tree.

The Greek, Aegan and Adriatic islands, and the northern shores of Africa on the Mediterranean have no mangrove trees. Here the tidal variation is too small to bring air to the roots as the tides recede. A simple approach would be to plant trees inland, above the high tide line and irrigate by pumping seawater. The trees should be fertilized with slow release nitrogen, phosphorus, and iron and planted in such a way that good drainage assures that salt buildup does not occur. In Eritrea we have planted trees above the high tide line and irrigated them with seawater. They thrive if fertilizer is applied and drainage is adequate.

The great deserts of the world, such as the Sahara, the Arabian peninsula, and the Atacama could be converted to mangrove forests with seawater irrigation. Since these regions are so vast, the economic contribution of the trees would be very large, and such forests would banish the problem of global warming.

We believe that planting mangrove trees in areas where they do not grow is the only feasible and cost effective approach to global warming. In addition, the economic contribution of such a program diminishes the chances that a second catastrophe does not overtake the human race. This would be human overpopulation caused by its linkage to poverty. 

Dr. Gordon Sato  January 1998 Eritrea
http://www.tamu.edu/ccbn/dewitt/manzanar/default.htm

[Astronuc]

The Manzanar Project: Towards a Solution to Poverty, Hunger, Environmental Pollution, and Global Warming Through Sea Water Aquaculture and Silvaculture in Deserts

Gordon H. Sato, Tesfom Ghezae, and Samuel Negassi

Ministry of Fisheries, State of Eritrea, Box 923, Asmara, Eritrea

In recent memory, famine and poverty have plagued two countries with extensive coastal deserts—Eritrea (a former colony of Ethiopia) and Somalia. The premise of the Manzanar project is that such coastal deserts can be converted to rich agricultural fields through the culture of microscopic algae (blue green bacteria) in sea water ponds, and the cultivation of mangrove species valuable for their timber through sea water irrigation.

Conversion of algae biomass to salt water fish. Algae grow so vigorously that most algal spedrug spammerts are preoccupied with preventing its growth in swimming pools, reservoirs, and recreational lakes. We can deduce that algae are extremely efficient in scavenging nutrients and using sunlight for photosynthesis. The problem is then not how to grow algae but how to insure that only desired algae grow to any significant extent, and to convert its protein, carbohydrate, and vitamins to products useful to man.

Our first approach was to convert algae to fish. In 1987, during Eritrea's war of independence from Ethiopia, one of us (GS) went into rebel held areas to assist in food production. Simple ponds were dug along the shore to a depth of about one half meter below the low tide line and about two hundred square meters in area. The ponds were filled with sea water, fertilized with chemical fertilizers to grow algae and inoculated with mullet fingerlings at a rate of one fingerling per square meter. After four months, each fish weighed about one pound. Less than one percent mortality was detected among these algae eating fish, which are famous for their hardiness in resisting disease and low oxygen concentrations. This is equivalent to a rate of production of about fifteen tons per hectare per year and demonstrated that desert shores could produce enough food to justify cultivation on a large scale. This was not surprising. In Southeast Asia, fresh water ponds have been fertilized to grow algae and inoculated with algae eating fishes for centuries. Our only variation on this time proven practice was to substitute seawater for fresh water and marine fish and algae for fresh water fish and algae.

Artemia salina (brine shrimp) as an intermediate. Another of our approaches has been to use the brine shrimp, Artemia salina. The brine shrimp is a small brachiopod that reaches a length of about 1.5 centimeters and a weight of 10 milligrams. It is extremely salt tolerant. It is avidly eaten by fishes, shrimp, birds, aquatic insects, etc. For this reason, it would be an excellent food stock for most any aquaculture or agriculture venture. If it is preyed on by so many of its fellow denizens of the wild how does this hapless creature manage to survive as a species, and how can its strategy for survival be adapted to its large scale production? The survival strategy of the brine shrimp is simple and effective. It begins life as a cyst on the banks of a dry pond devoid of predators such as fishes, aquatic insects, and birds. The cysts remain viable in the dry state for many years. When the rains come, the cysts hatch in about 24 hours, and the hatchling begin to filter feed on the microscopic algae that grow in the pond. In about ten days they reach sexual maturity and reproduce at a rapid rate. The females produce about one hundred live young, nauplii, per day when the salinity is below eight percent. As the salinity approaches eight percent through evaporation, the females switch from producing live young to producing cysts that cannot hatch at high salinity. The cysts are washed onto the banks by the wind, and the pond evaporates to dryness. The strategy for survival of the species is: 1) begin life without enemies in a dry pond as cysts, 2) hatch quickly when the rains come and in a short time reproduce at a rapid rate, 3) live in water so salty as to exclude many potential predators, and 4) end the cycle as an unpalatable dry cyst that awaits the next rain. We have mass cultured brine shrimp using a strategy similar to the strategy of the brine shrimp in the wild.

Mass cultivation of brine shrimp. Brine shrimp cysts from the Great Salt Lake, Utah, were purchased from the Petco Corp. and were used to generate the initial brine shrimp populations. The work was carried out on Halib Island about thirty kilometers offshore from Assab, Eritrea on the Red Sea. Three ponds, each about two hundred square meters in area, were dug to a depth of about 0.5 meters below the low tide line. The ponds were situated about twenty meters from shore. Water seeped into the ponds through the soil. Tidal variation at Assab averages about 0.5 meters, and rainfall averages about two centimeters per year. Both conditions are favorable for brine shrimp production because rapid salinity changes are not effected by rain or exchange with ground water, and fertilizer losses through leaching are minimized.

When water first enters the pond, its salinity is about six percent, and rises to about eight percent after three weeks, the length of the production cycle. The cycle was initiated by pumping the ponds to near dryness leaving about one cubic meter in a depression. Five hundred grams of laundry detergent (Omo), were dissolved in the residual water, and with a pump the pond was washed with detergent. In some cases, three hundred grams of sodium hypochlorite were also added. Water re-entered the pond by seepage, and reached sea level in one day. At this point, two hundred grams of adult brine shrimp were added, and di-ammonium phosphate was added at a rate of 2.5 kilograms per three weeks or about 120 grams per day.

Within four days, the ponds were visibly green with algae, and the peak of algae density was reached in about ten days. At first the algae grew faster than they could be consumed by the brine shrimp, but the brine shrimp population overtook the algae at about day twenty of the cycle. The pond suddenly cleared of algae, and the brine shrimp were harvested, drained, and weighed. The bulk of the brine shrimp were harvested by attracting them to the light of flashlights suspended over the edge of the pond. The aggregated brine shrimp were easily harvested with a scoop net. The remainder of the brine shrimp was harvested by pumping out the pond through a chiffon filter. The pond was washed with detergent, and the cycle repeated.

Brine shrimp yields were 17.6, 13.0, 12.8, and 11.7 kg. wet weight per twenty one day cycle per two hundred square meters. The results extrapolate to the equivalent of 10 to 15 metric tons per hectare per year. This has great promise for rendering desolate desert land productive. Brine shrimp can serve as food for a diversity of marine organisms such as fish and shrimp, and could serve as a major source of protein for chickens, cattle, and goats. This work was carried out without benefit of electricity or pumps for aeration. With proper equipment, we predict that much higher yields can be routinely achieved.

Predators and parasites. When the ponds were first established, aquatic beetles were observed momentarily surfacing to take air, and quickly diving to covert positions on the bottom. When one beetle, approximately 1.0 cm. in length was placed in a sea water jar with twenty adult brine shrimp, the brine shrimp were all consumed within a few hours. The beetles were attracted to the light of a flashlight at night. A trap was constructed with an inverted glass funnel illuminated by a flashlight. The beetles would enter the large opening of the funnel, and drown in a submerged chamber. When such a trap was deployed for three successive nights, many beetles were caught, and beetles could no longer be observed surfacing during the day. Dead immature beetles were also observed in the detergent wash water.

Contamination by wild or toxic algae. The predominant algae in our ponds were identified as Synechococcus (about 80%), and Dunaliella (about 20%). They are obviously appropriate food for brine shrimp. This observation draws attention to the unpleasant possibility that the ponds could be overtaken by toxic algae. To test the possibility that some degree of control could be exercised over the composition of the algae population in the ponds, one pond was washed with detergent and the other pond was washed with detergent and hypochlorite. The ponds were fertilized in the usual manner. The pond washed with detergent was dark green after ten days while the pond washed with detergent and hypochlorite was not even faintly green. This indicates that when ponds are washed with chlorine they are virtually devoid of a starting population of algae, and that in the future we can control the algae population by controlling the inoculum.

Novelty of the approach. Our approach to the mass culture of brine shrimp and algae differs in basic respects from current practice. Mass culture of brine shrimp is usually carried out in expensively constructed concrete raceways elaborately equipped with air and water pumps. The refinement of raceways has gone so far as to include elaborate traps for sequestering and eliminating brine shrimp feces. For lack of mass cultures of algae, due to the conventional belief that large outdoor ponds are not feasible due to contamination, brine shrimp are fed artificial diets such as finely milled rice bran (1). In contrast, we have employed simple ponds taking advantage of the vast area and abundant sunlight of coastal deserts to mass culture algae and brine shrimp. Clearly, extensive use of the large areas of coastal deserts is indicated if algae and brine shrimp are to make a significant contribution to the food supply and wealth of impoverished regions of the world.

Batch versus continuous culture. We use batch culture as opposed to conventional continuous culture to minimize the time and opportunity for the entry, establishment, and eventual domination by unwanted algae, pathogens, and predators. Our batch cycle time of three weeks is short, and our ponds are effectively disinfected by washing between cycles. We envision having considerable control over the composition of our algae populations by maintaining stock cultures in the laboratory, expanding them in moderate sized open cultures under selective conditions, and inoculating them into ponds that have been washed with chlorine. It should also be borne in mind that sea water microorganisms are removed as the water filters into the ponds through the soil. Currently we are employing selection techniques for the improvement of algae stocks to obtain thermophilic algae that will withstand the highest temperatures possible and herbicide-resistant algae in the presence of herbicides (2,3).

Mangrove forests as alternative for decreasing rain forests. Theories of global warming, polar cap melting and coastal flooding have been linked to global rain forest destruction and consumption of fossil fuels. Remedies under consideration related to rain forests and reduction of consumption of fossil fuels are unlikely to be adequate for economic and political reasons. During the course of our work we planted mangroves around the periphery of ponds to stabilize banks and at sites well above sea level where the trees are irrigated with sea water. We noted that in almost all cases the trees grew as well as in their natural habitat.

Our observations on the growth and function of mangroves in that context leads us to suggest that a replacement approach, e.g. to convert the great deserts of the world to mangrove forests, might be a more positive and politically, even economically, acceptable approach to counter de-forestation. Mangrove trees grow in sea water, and in nature they grow in the inter-tidal zone. Growth is limited too far above the high tide line because they need sea water and too far below the low tide line because their roots need the air available at low tide. The need for tidal movement to bring air to roots is the probable explanation for the lack of mangroves in the Aegean Sea region where tidal variation is small. This suggests that mangroves could be cultivated on barren Greek islands if planted well above sea level, and irrigated with sea water.

The growth requirements of plants are well known. Any plant can be grown on an inert substrate such as sand so long as it is watered with a solution at the right pH containing the known mineral nutrients, and the roots are provided with air. Mangrove swamps contain a dark mud in which organic material is continuously oxidizing and providing organic acids which slightly lower the pH below that of sea water. We propose that vast deserts such as the Sahara can be planted with mangroves and irrigated with slightly acidified sea water. In addition we propose that sewage sludge can be incorporated in the soil around the trees to provide nutrients, mimic the rich organic muds of mangrove swamps and solve the problem of sludge disposal. Some mangroves, such as some of the Rhizophora species make good quality timber, which could be farmed as a renewable resource. The cost of moving sea water for irrigation will not be prohibitive. In fresh water agriculture, it is not uncommon to pump water from deep aquifers or to bring water from great distances through canals. Preliminary success has already been observed with growing mangroves in deserts with sea water irrigation (4). Barth and Leith made extensive plantings above sea level alongside a channel for water from a reverse osmosis plant.

Conclusion. Vast areas of the world are barren deserts with access to the sea, usually in impoverished countries. If brought into useful production, they would make a major contribution to breaking the cycle of poverty and overpopulation, one of the most urgent problems facing the human race. Taken together, the results we have achieved, the techniques developed, and the considerations raised all suggest that some of the most urgent and vexing problems of the world can be approached through application of simple technology applying the scientific method.

Acknowledgements. This paper is dedicated to Shingo Nomura of the Centre for Global Action whose aid enabled GS to start the Manzanar Project with Eritreans during their war for independence and to materially aid their efforts. The Manzanar Project is named after a relocation camp in central California where GS was interned during the Second World War and first began thinking of producing food in the desert. GS expresses gratitude and admiration to the current and former members of the Manzanar committee; Stanley Cohen, Lawrence Grossman, Niels Jerne (deceased), Tom Maciag, Rita Levi-Montalcini, Shingo Nomura, Jesse Roth, Martin Rodbell, Jonas Salk (deceased), Howard Schneiderman, Lewis Thomas (deceased), Susumu Tonegawa, Gary Trudeau, and Jim Watson for their courage and public spirit in lending their prestigious names in the endorsement of a project with high intentions, but uncertain prospects for success. We thank Richard Petterson of the Hydro Corp. for donating cargo ship spillage of di-ammonium phosphate. GS thanks Charles Crocker, David Rammler, and the Mary A. Crocker foundation for enabling him to start brine shrimp culture on the Salton Sea. We thank Petros Solomon, Eritrean Minister of Fisheries, for encouragement and support. Currently, the ministry of fisheries is supporting the development of a ten hectare site for algae, brine shrimp, and mangrove production.

References

1. Lavens, P., and Sorgeloos, P. (eds.) (1996) FAO Fisheries Technical Paper 361.

2. Shinohara, K., Zhao, Y., and Sato , G.H. (1983) Advances in Gene Technology: Molecular Genetics of Plants and Animals, Downey, K., Voellmy, R.W., Ahmad, F., and Schultz, J., (eds.), Academic Press, San Diego, pp. 327-332.

3. Zhao, Y., Qian, K., and Sato G.H. (1983) Advances in Gene Technology: Molecular Genetics of Plants and Animals, Downey, K., Voellmy, R.W., Ahmad, F., and Schultz, J., (eds.), Academic Press, San Diego, pp. 333-347.

4. Barth, H., and Lieth, H., (1982), Studies on Aquatic Vascular Plants, Symoens, J.J., Hooper, S.S., (eds.), Royal Botanical Society of Belgium. Brussels, pp. 235-239.

Published in In Vitro Cell. Dev. Biol.-Animal, Volume 34, No. 7, July-August 1998.  Reprinted without permission.

[Astronuc]

Planting Mangroves In Non-Native Environments

Simon Tecleab, Millien Ghermai, Samuel Negassi, Tesfom Ghezae, Robert Riley and Gordon Sato (2000)

The Manzanar Project*, Ministry of Fisheries, P.O. Box 18, Massawa, Eritrea

The world population of human beings reached six billion in 1999. By mid century ten to eleven billion humans will inhabit this earth. To predict the consequences, we need only look at present day problems and estimate how they will be worsened by the increased population.  The poor countries of the world, about 80% of the world’s population, will be even poorer. The desperate poverty will result in ever increasing chaos, disorder, crime and violence. Military dictators will emerge, and they will be corrupt. Their coterie of thugs will administer the corruption, share in the profits, and effectively suppress any disssension. The population problem will grow worse. Poor people do not have knowledge of contraception, are too poor to purchase the paraphernalia, and want more children to keep them from starving in their old age. The hope of ever emerging from this desperate situation will be small. 

Six billion people are pretty effective in despoiling the earth’s environment. How much more effective will ten or twenty billion people be? At the present time we add three and a half billion tons of CO2 to the atmosphere each year. Scientific opinion is divided as to what the consequences will be, but if global warming occurs, and the polar ice caps melt, countries like Holland and Japan will disappear, and all the great coastal cities of the world will be under the sea. Despite our uncertainty as to whether or not this catastrophe will result, we must pay close attention to this problem. We are growing mangrove trees where they do not naturally occur, and developing seawater agriculture and mariculture as one possible contribution to averting the problems we have mentioned. We are hopeful that with the passage of time more and more people will turn their attention to these urgent, practical problems.

Mangroves occur in nature in the intertidal zones of tropical countries. They provide nursery grounds for fishes, and shrimps. Their falling leaves, through a complex food chain, provide food for a multitude of marine animals. The leaves of Avicennia, the most common mangrove in Eritrea, are more nutritious than alfalfa, ( their dry weight is fifteen percent protein). It is excellent fodder for camels, goats, and cattle. We can estimate their economic value from the observation that a hectare of Avicennia drops up to ten tons of litter per hectare per year. It is reasonable that a hectare of Avicennia produces about twenty tons, dry weight, of leaves per hectare per year, or three tons of protein. If converted directly into beef with 100% efficiency, we could produce ten tons of beef per hectare per year. Cattle are notoriously inefficient in food conversion so a hectare of trees would produce one ton of beef per year. This has a value of about 3000 USD, or equivalent to four times the annual salary of a fully employed Eritrean worker at this time. One worker could manage up to five hectares with a helper to manage the cattle. There are many ways to convert mangroves to valuable products, but this example is sufficient to demonstrate the economic feasibility of growing mangroves. The cost of establishing, and maintaining a hectare of mangrove trees is presented in Table 1. The cost is a small fraction of the value produced. Depending on the density of planting, fodder cannot be harvested for two or three years after planting. This delay is a relatively small factor in assessing the cost/benefit value of planting mangroves.


-------------------------------------------------------------------------------
Table 1. 

Cost of planting one hectare of trees in the intertidal zone

Cost of establishing 1000 trees in the nursery 20 USD

Cost of planting seedlings in final site 20 USD

Cost of fertilizer 50 USD

Cost of Fences for one hectare 50 USD

Cost of guard per hectare per year 50USD

The cost of labor in Eritrea at the present time is 2.00 USD per man per day. We estimate it will require at most ten man days to gather 1000 seeds and plant them in plastic bags in the nursery. It will require no more than ten man days to plant 1000 trees in each hectare. At the initial planting each tree will be provided 500 grams of Diammonium phosphate, or 0.5 tons per hectare. This fertilizer should last two years when the trees are small. After the second year we will provide about one and a half tons of diammonium phosphate per year. Because of the layout of the plots, each hectare of plot will require about 100 meters of barbed wire fence. The duty of the guards who can care for about twenty hectares will be to prevent camels from breaking in and destroying trees, and at certain seasons to remove encircling wrasse from young trees.


-------------------------------------------------------------------------------

Only fifteen percent of the coast of Eritrea contains mangroves. The mangroves typically grow in mersas where the seasonal rains are channeled to enter the sea. We reasoned that the rains must be bringing needed mineral nutrients from land. When we compared the composition of sea water to that of a complete algae medium, we found three elements in short supply in sea water-----nitrogen, phosphorus, and iron. To test our explanation for the occurrence of mangroves in mersas, we planted trees in intertidal areas where trees had never grown before, and provided them with a slow release fertilizer. We place five hundred grams of diammonium phosphate, DAP, and a few grams of iron oxide in a plastic bag. seal it shut, and punch two holes on one side of the bag with a small nail. The bag is buried next to the tree with the holes facing the tree. The fertilizer diffuses out through the nail holes over a period of years.

Many negative control experiments were inadverdently performed. Before we knew the importance of DAP and iron, hundreds of trees were planted and failed to become established. With the provision of DAP and iron the trees are routinely established.

Near the city of Massawa, the Italians built a jetty. Before the jetty was built mangrove trees grew on both sides of the jetty. After the jetty was built trees on one side of the jetty died out. We reasoned that the jetty prevented the flow of water carrying the nutrients in the seasonal floods from reaching the area. To test this hypothesis, we planted trees in the area where they had died out and provided them with DAP and iron.  After one year they are approximately one meter tall.

Where trees do grow in the intertidal zone in Eritrea, they typically form a narrow fringe no more than 100 meters wide. Often beyond this fringe mud flats extend as much a kilometer out to the low tide line. The reason for the restriction of trees to the first hundred meters from the high tide line is that as nutrients are brought by the seasonal rains they are too dilute after the first hundred meters to nourish the trees. To test this idea, we have planted trees several hundred meters from the high tide line in areas where trees had never grown before, and they grow well if fertilized by our methods.

We conclude that the entire 1200 kilometer coast could be planted with mangrove trees with an average width of about 500 meters in the intertidal zone. This could increase the economic productivity of the country by about 50%.

We have also planted trees in the desert away from the sea. Here we dig a hole one meter deep and fill it with sand to provide drainage. The trees are planted in the sand, fertilized as described, and irrigated by a pump with sea water every few days. Drainage is important for preventing the accumulation of salt and providing air for the roots. Between the trees we have planted a grass, Distichlis spicata, which can grow with sea water irrigation, and is good fodder for ruminants.

We conclude that large areas of the Eritrean desert could be converted into lawn covered forests, with trees and grasses that would provide food for cattle, goats and camels. If the area to be irrigated were only 10 kilometers wide, the economic production of Eritrea could be increased ten fold.

Planting mangroves in areas where they do no naturally occur can do much to alleviate the poverty of much of the developing world. It can also relieve much of the tensions that develop over competition for fresh water. In addition if large deserts such as the Sahara, the Arabian peninsula, and the Atacama were planted with mangroves and irrigated with sea water, these forests could fix all the CO2 produced by burning fossil fuels. The cost of such a program could seem daunting but is miniscule compared to the economic devastation caused by the melting of the polar ice caps.

By August, 2000, we have forty thousand mangroves established in our nursery, and these will all be planted by the end of the year in four hectares of the intertidal zone at one thousand trees per hectare. We calculate that this will provide a full canopy by the time the trees are mature. In the year 2001, we will plant one million trees to occupy one thousand hectares of intertidal zone near the village of Hargigo about ten kilometers from Massawa.

This work can be carried out in Eritrea because of the special conditions found in the country. The leaders of the country are men and women dedicated to the well being of the people. There is no corruption. The international business community knows that Eritrea is a country where business is conducted without payment of bribes to government officials. The government is enthusiastically supporting work to develop the work of the Manzanar project and the program of the Seaphire corporation to develop shrimp farming and Salicornia farming in Eritrea. Salicornia is a succulent shrub that can grow with sea water irrigation, produces seed oil of high quality, and its stems when dried can be used as cooking fuel. These unconventional approaches are encouraged by the government because the country is poor in known natural resources, and conventional agriculture is insufficient to feed the nation. In contrast to Eritrea, two neighboring countries, Ethiopia and Sudan, do not even develop their known resources for the benefit of their people. Eighty percent of the arable land of Ethiopia is not farmed, and the country suffers from famine. The Sudan has forty six million acres of potential farm land and the waters of the Blue and White Nile. If farmed, the Sudan could feed all of Africa. The Sudan suffers from famine. In Eritrea there are nine ethnic groups, and two main religions, Christianity and Islam. All live together in harmony, and share in the power of governance. Eritrea has all the conditions favorable for development-----dedicated, and competent leadership, no corruption, and remarkable national unity in an ethnic and religiously diverse society.

*Manzanar is the name of the camp where GS was interned during WWII.  GS expresses gratitude to the current and former members of the Manzanar committee; Stanley Cohen, Lawrence Grossman, Niels Jerne (deceased), Tom Maciag, Rita Levi-Montalcini, Shingo Nomura, Jesse Roth, Martin Rodbell (deceased), Jonas Salk (deceased), Howard Schneiderman (deceased), Lewis Thomas (deceased), Susumu Tonegawa, Gary Trudeau, and Jim Watson for their support and encouragement.

[Astronuc]

From Jim Metzner's Pulse of the Planet.

You'll find them [mangroves] in the warmer climates of our planet, like a living filter between land and sea. Whether they're made up of trees, grasses, or salt marshes, mangroves are a crucial part of the world's coastal environments.

According to Ivan Valiela, a professor of biology at Boston University's Marine Program at the Marine Biological Laboratory in Woods Hall, Massachusetts, "Coastal mangrove forests provide a really important ecological role, in that they act as filters for a number of land-derived materials and not only that, they're also so rich in terms of potential food for other organisms - shellfish and juvenile fish."

"Fish that live offshore in reefs or elsewhere use these coastal forests as places in which the young can grow. They're nursery areas. So there's a whole bunch of environmental reasons why these environments need to be conserved because they play a really significant role in conserving the kinds of populations that we're interested in a larger sense, whether it's economic because shrimp fishery depends on them. In fact, the more wetlands there are in a coastline, the larger the shrimp fishery will be offshore. There's a recent paper that confirms that in fact a significantly large proportion of fish from coral reefs use mangroves as nursery areas. So you can accumulate a large set of arguments that this thin strand of mangrove that's set between land and sea play really significant ecological roles."


They may look like salt marshes, grasslands, or tangled masses of trees. Mangroves are the ecosystems which line coastal areas in temperate climates around the world. Among the important roles that mangroves play is to act as a kind of 'biotransformer' of the organic materials that pass between the land and sea.

"They're transformers. They transform what comes in from land - they change it in ways that make it more possible and more accessible for marine organisms to make use of them."

Around the world, mangroves are being destroyed to make room for shrimp farms, housing, and other forms of urban expansion. But the loss of a mangrove can have serious environmental consequences.

"What happens is that first of all, more of the land-derived materials - whether its sediment, or whether it's heavy metals, or whether it's nitrogen and phosphorus- will make it to the sea. And that means that probably water quality will be lower. In fact, in many places in the Australian Great Barrier reef, people are beginning to be concerned about the survival of certain coral species because of the changes going on, from not only urban sprawl, but also the destruction of mangroves forests on the shore. So there's connections there that will certainly have consequences if we have reduced the subsidies that mangrove forests provide us."

[Astronuc]

Mangroves Are Nurseries for Reef Fish, Study Finds

John Roach
for National Geographic News, February 4, 2004

Mangroves—forests of tropical trees and shrubs rooted in saltwater sediments between the coast and the sea—are crucial nurseries for coral reef fish, according to a new study.

The finding highlights the importance of the rapidly dwindling habitats to reef communities.

"Beyond showing they are important, we showed they are much more important than even assumed," said Peter Mumby, a marine biologist at the University of Exeter, England.

Mumby and his colleagues found that mangroves serve as a vital, intermediate nursery as coral reef fish journey from their cribs in seagrass beds to the large coral reef ecosystems that fringe coastal communities.

Coral reef fish were up to twice as abundant on reefs adjacent to mangrove forests compared to reefs that weren't, researchers found. They also learned at least one species, the rainbow parrotfish (Scarus guacamaia), depends on mangroves for its very survival.

The study will appear in tomorrow's issue of the science journal Nature and was supported by a grant from the National Geographic Society's Committee for Research and Exploration.

Mangrove Conservation

Mumby and his colleagues believe that conservation efforts are necessary to protect connected corridors of mangroves, seagrass beds, and coral reefs to maintain the resiliency of coral reef ecosystems—and their productivity for fisheries.

Ivan Valiela, a marine biologist with Boston University's Marine Biological Laboratory in Woods Hole, Massachusetts, agrees. He said the research reinforces the concept that individual ecological units—mangroves, reefs, land—are crucially intertwined.

"Maintenance of these important environments therefore has to be done from a wider perspective," he said. "This whole set of concepts bears on the issue of setting up coastal reserves, national parks, maintaining commercial stocks, and a host of other management issues."

Nursery School

Mangrove forests are home to an abundance of wildlife. Above water, butterflies, birds, and mosquitoes zip around the canopy. Snakes, crocodiles, and crabs scurry and swim about the forest floor. And in India, Bengal tigers (Panthera tigris) laze in forest branches.

"You tend to find mangroves form this very dense network of channels and creeks that are very, very calm and peaceful but also [teem] with all sorts of life," said Mumby.

Researchers have long known that fish often mature in the murky saltwater amid the tangled labyrinths of roots created by mangroves. But according to Mumby, the importance of these nurseries to reef fish communities had never been quantified.

Factors such as fishing pressure and larval supply were thought to be more important to the structure and abundance of reef fish than the presence or absence of mangrove forests.

Since juvenile fish are known to hang out in other habitats like seagrass beds and small, protected patch reefs before venturing out to large reefs, researchers sought to answer a key question: In the absence of mangroves, wouldn't these other habitats suffice?

To find out, they sought coral reefs so isolated from mangroves that it would be impossible for fish from mangrove habitats to reach them. They found such reefs in Belize.

"In Belize, we have the unusual situation of offshore reef atolls with massive amounts of mangroves as well as atolls with nothing at all," said Mumby.

The researchers contrasted the populations of 164 fish species in the two different habitats. They found that mangroves serve as an intermediate nursery, making for much healthier and robust coral reef fish communities.

Mumby explained that the fish start out in seagrass beds, but once they grow two to three inches (five to eight centimeters) they are too big to hide from predators there. At that point they move into mangroves, which offer murky hiding spots and abundant food.

"They survive well in the mangroves until they are a bit larger," said Mumby. "But at some point they need to move to the reef. We are not sure why they move to the reef, but [we] suspect it's a good place to reproduce."

Once they grow big enough in the mangrove, the fish swim out to patch reefs in the lagoon. There, they co-exist with thousands of other juvenile fish, packing on girth in order to reach and survive on the larger, fringing reef.

In the absence of mangroves, fish swim directly from the seagrass beds to the patch reefs. But because they are smaller, predators catch them more easily, said Mumby.

Mangrove Destruction

Previous research by Valiela indicated mangroves are being destroyed more than twice as quickly as the well-publicized destruction of tropical rain forests. "We, by no means, expected to find the rates we in fact calculated," he said.

In the past, mangroves were deemed a mosquito-infested nuisance to waterfront home development and razed. Today, they are mostly cleared to make way for shrimp farms.

Mangroves provide important functions, including processing land-derived nutrients, serving as a buffer against pollution runoff, and filtering food for marine mammals.

The finding that mangroves serve as crucial nurseries for coral reef fish highlights another reason to conserve these rapidly disappearing habitats. "To really sustain fish, one thing you should aim to do is conserve a certain amount of mangroves," said Mumby.

According to Valiela, this is easier said than done. "We are dealing with Third World, marginal economies. There are few choices for these people. We are sure they do not want to damage the very environment in which they live, but there are few other crops that yield as much [as shrimp farms]," he said.

Mumby said he hopes the findings will strengthen the importance of mangroves to fishermen who have a key political voice in many tropical regions. Valiela is calling on the international community to better understand the ecology of these connected ecosystems and pose conservation incentives and sustainable development alternatives for affected local communities.

[Astronuc]

Good article on mangroves and mangals.

http://en.wikipedia.org/wiki/Mangrove

http://en.wikipedia.org/wiki/Avicennia

http://en.wikipedia.org/wiki/Avicennia_marina (white, grey mangrove)

http://en.wikipedia.org/wiki/Avicennia_germinans (black mangrove)

http://en.wikipedia.org/wiki/Rhizophora_mangle (red mangrove)

Edit 2007-04-08: Avicennia is now considered in the family Acanthaceae based upon its molecular phylogenies which show a relationship.
http://en.wikipedia.org/wiki/Acanthaceae

[Astronuc]

IMPORTANCE OF MANGROVES
http://www.flmnh.ufl.edu/fish/southflorida/mangrove/Importance.html

See also posts above.  Mangrove vegetation can be an important source of forage.

Geographical distribution
http://www.flmnh.ufl.edu/fish/southflorida/mangrove/Distribution.html

Forty species of mangroves dominate approximately 75% of the world's tropical coastlines between 25° N and 25° S. In certain locations, this range extends beyond these limits due to the movement of unusually warm waters from the equator. These areas include the east coast of Africa, Australia, and New Zealand where mangroves occur 10-15° farther south. In Japan, Florida, Bermuda, and the Red Sea, this range extends 5-7° farther north. Mangroves in the Indo-West Pacific are more diverse, consisting of more than 30 tree species, than those in Florida.

http://www.flmnh.ufl.edu/fish/SouthFlorida/mangrove/Habitat.html

Mangroves are tropical species, surviving at temperatures above 66° F (19° C), not tolerating fluctuations exceeding 18° F (10° C) or temperatures below freezing for any length of time.