Ala Wai Project: Ammonium Nitrate

Ala Wai Project: Ammonium Nitrate

Question: How does the concentration of NH4NO3 in water affect the growth rate of Rhizophora mangle in conditions resembling those of the Ala Wai Canal?

Darwin Kwok – Scott Marison – David Brown – Connor Buckland – Anne Heslinga

January 13, 2012

The Introduction

Systematic Breakdown of Laboratory Components and Variables

Rhizophora mangle (Origin and Structure)

Rhizophora mangle, or the red mangrove, is commonly found along coastal or brackish waters in climates above 20°C, and in water with salt concentrations ranging between 0 and 90 parts per thousand (Hill 2001). Rhizophora mangle is seen primarily around coastal regions in Florida, Louisiana, and Texas. It is native to the west coast of Africa and both west and east coast of America. In Hawaii, Rhizophora mangle is considered an invasive species as it covers area in large, dense, monospecific thickets. However, the intricate system in these thickets allow for symbiosis between the mangrove and the organisms that reside in the same environment. Usually, the relationship is a form of commensalism in which the diverse array of other organisms use the intricacy as nesting or hunting strategies. (Encyclopedia of Life, 2011)

Rhizophora mangle prosper in subtropical and tropical areas in regions of high water concentrations. They are able to endure environmental conditions containing high salinity and resultantly can survive in conditions that many other plants find unbearable. The roots of Rhizophora mangle are usually submerged underwater inside a sand-clay composition foundation. Their adaptability to estuarine shorelines, brackish water, and other hydro-environment allows them to become opportunistically invasive in environments with excessive water amounts.

Red mangroves are distinguished by their propagules, a long cylindrical fruit formed after fertilization has taken place in mangrove flowers. The propagule falls from the plant into the water underneath and floats often for months and many miles until it finds a good patch of wet soil to take root in. The propagule forms into a seedling and grows out of the mud. Then, aerial prop roots grow out of the trunk of the mangrove tree and down into the soil, stabilizing the plant. This is another distinctive feature of Rhizophora mangle (Marietta, 2008). Growing at slightly less than one meter per year, this mangrove can reach between 100 and 160 feet (50 meters) in height. (Hill, 2002)

Rhizophora mangle (Nutritional and Habitual Adaptations)

Mangroves require a number of physiological adaptations to overcome the problems of anoxia, high salinity and frequent tidal inundation. (All of the following from Hill, 2001)

Mangrove roots slow water flow, thereby enhancing sediment deposition in areas where it is already occurring. The fine, anoxic sediments under mangroves act as sinks for a variety of heavy (trace) metals which colloidal particles in the sediments scavenged from the water. Mangroves protect coastal areas from erosion, storm surge (especially during hurricanes), and tsunamis. The mangroves' massive root systems are efficient at dissipating wave energy. Likewise, they slow down tidal water enough that its sediment is deposited as the tide comes in, leaving all except fine particles when the tide ebbs. In this way, mangroves build their own environment. Because of the uniqueness of mangrove ecosystems and the protection against erosion they provide, they are often the object of conservation programs, including national biodiversity action plans.The unique ecosystem found in the intricate mesh of mangrove roots offers a quiet marine region for young organisms. In areas where roots are permanently submerged, the organisms they host include algae, barnacles, oysters, sponges, and bryozoans, which all require a hard surface for anchoring while they filter feed. Shrimps and mud lobsters use the muddy bottoms as their home. Mangrove crabs mulch the mangrove leaves, adding nutrients to the mangal muds for other bottom feeders.

Red mangroves, which can survive in the most inundated areas, prop themselves above the water level with stilt roots and can then absorb air through pores in their bark (lenticels). Black mangroves live on higher ground and make many pneumatophores (specialised root-like structures which stick up out of the soil like straws for breathing) which are also covered in lenticels. These "breathing tubes" typically reach heights of up to thirty centimeters, and in some species, over three meters. There are four types of pneumatophore—stilt or prop type, snorkel or peg type, knee type, and ribbon or plank type. Knee and ribbon types may be combined with buttress roots at the base of the tree. The roots also contain wide aerenchyma to facilitate transport within the plant.

Limiting salt intake

Red mangroves exclude salt by having significantly impermeable roots which are highly suberised, acting as an ultrafiltration mechanism to exclude sodium salts from the rest of the plant. Analysis of water inside mangroves has shown 90% to 97% of salt has been excluded at the roots. Salt which does accumulate in the shoot, concentrates in old leaves which the plant then sheds. Red mangroves can also store salt in cell vacuoles.

Limiting water loss

Because of the limited fresh water available in salty intertidal soils, mangroves limit the amount of water they lose through their leaves. They can restrict the opening of their stomata (pores on the leaf surfaces, which exchange carbon dioxide gas and water vapour during photosynthesis). They also vary the orientation of their leaves to avoid the harsh midday sun and so reduce evaporation from the leaves. Anthony Calfo, a noted aquarium author, observed anecdotally a red mangrove in captivity only grows if its leaves are misted with fresh water several times a week, simulating the frequent tropical rainstorms.

Nutrient uptake

The biggest problem that mangroves face is nutrient uptake. Because the soil is perpetually waterlogged, there is little free oxygen. Anaerobic bacteria liberate nitrogen gas, soluble iron, inorganic phosphates, sulfides, and methane, which makes the soil much less nutritious and contributes to mangroves' pungent odor. Pnuematophores (aerial roots) allow mangroves to absorb gases directly from the atmosphere, and other nutrients such as iron, from the inhospitable soil. Mangroves store gases directly inside the roots, processing them even when the roots are submerged during high tide.

Increasing survival of offspring

In this harsh environment, mangroves have evolved a special mechanism to help their offspring survive. Mangrove seeds are buoyant and therefore suited to water dispersal. Unlike most plants, whose seeds germinate in soil, many mangroves (e.g. red mangrove) are viviparous, whose seeds germinate while still attached to the parent tree. Once germinated, the seedling grows either within the fruit (e.g. Aegialitis, Avicennia and Aegiceras), or out through the fruit (e.g. Rhizophora, Ceriops, Bruguiera and Nypa) to form a propagule (a ready-to-go seedling) which can produce its own food via photosynthesis. The mature propagule then drops into the water, which can transport it great distances. Propagules can survive desiccation and remain dormant for over a year before arriving in a suitable environment. Once a propagule is ready to root, its density changes so the elongated shape now floats vertically rather than horizontally. In this position, it is more likely to lodge in the mud and root. If it does not root, it can alter its density and drift again in search of more favorable conditions. (Campbell, 2008)

Ammonium nitrate (NH4NO3)

Known as an effective chemical compound for explosives and agricultural fertilization, ammonium nitrate is a common compound that is found as a white crystalline solid at room temperature (with standard pressure that is). Ammonium nitrate is made from the acid-base reaction of ammonia and nitric acid (HNO3(aq) + NH3(l) → NH4NO3(aq)) There are many distinct properties of ammonium nitrate that makes it very diverse in its usability in both farming industries and explosive compounds. (Killpack, 1993)

One distinct trait of ammonium nitrate is its relative combustive property around a source of ignition. The chemical compound acts as a strong oxidant and reacts readily with any other reactive substances. For this reason, ammonium nitrate is use distinctively for catalyzing the detonation rate of other explosives by modifying the time in which it takes for them to react (in most cases shortening the time needed). Besides its relative explosive behavior, ammonium nitrate has relatively no long-term pernicious effects on the human health. It is neither a carcinogen nor a mutagen by any part, though there are some short-term hazardous and deleterious effects if contacted directly with the body. (Encyclopedia of Life, 2011)

The main effect ammonium nitrate has on biological species is its usage as a source of nitrogen. Being 27% nitrogen, it is a very beneficial aspect for plants to use because of its high concentration of usable nitrate. As a result, this compound has been a relative inexpensive fertilizer that is commercially sold across the world despite its relatively agitated behavior. Nitrate take-up will be explained in the following part of this background.

Nitrate Properties and Effects on Plant Organisms

Ammonium nitrate consists of a high percentage of usable nitrogen in the form of nitrate. Nitrate, in minuscule quantities, can pose no dramatic health problems to humans or other organisms. In water, nitrate can be separated from its ammonium nitrate compound, and resultantly, the surrounding environment’s nitrate levels can increase significantly. In estuarine systems that are relatively close to land, nitrate can cause the death of marine life if it reaches high enough levels. It can impair the immune system and halt growth in many marine species if remained unchecked. (Killpack, 1993)

The surface runoff of ammonium nitrate serves as an effective source of nitrate fertilization for agricultural areas. Eutrophication causes growth of different vegetation including algae, and this encourages growth of plants and related species. The reason for this is the form in which nitrogen is given in. Nitrogen is essential for the production of amino acids and nucleic acids in all organisms, yet eukaryotes (which include plants) can only obtain nitrogen from a limited group of nitrogen compounds. Nitrate is a common compound that can be found in runoff water that plants can utilize in their amino acid and nucleic acid production. (Coleman, 2010)

Ammonium Properties and Effects on Plant Organisms

As with nitrate, ammonium serves as a parallel efficient source of nitrogen for amino acid and nucleic acid composition and construction in plant species. Both forms, ammonia and ammonium, can be used as a effective source of nucleic acid and amino acid construction. Though they prove to be hazardous to many species of animals in high amounts of exposure, it is effective as a suitable fertilizer for plants due to its nitrogen composition. It is less likely to be found in runoffs, but it is found in the form of ammonium nitrate in which we are testing in this laboratory. (Wikipedia, 2012)

Data

Statistics on Growth of Rhizophora mangle in Varying Environments

Data for the laboratory will be shown in tables and graphs near the end of this laboratory report.

Materials and Method

Step-by-Step Process in Studying Rhizophora mangle Growth in Variables

Materials:

● 8 Buckets

● Water

● Stand apparatus

● NH4NO3

● NH4NO3 concentration measuring strips

● 7 Mangrove plants

Method:

1. Collect 8 small mangrove stems past the sprouting stage of growth. Mangrove stems will be roughly the same height and from the same plant if possible.

2. Weigh and measure the height of the entire plant and measure root radius

3. Fill 8 buckets to the same level with water, and mark this level.

4. Record NH4NO3 levels in the Ala Wai.

5. Add magnesium to the water.

6. Set up experimental apparatus to hold each plant upright.

7. Add levels of NH4NO3 on the same magnitude as ammonium nitrate in the Ala Wai, starting with 0%, then 50% of the Ala Wai concentration, 100%, 150%, 200%, 250%, 300%, and 350%.

8. Place buckets in sunlight or similar environment to the Ala Wai.

9. Check water level on a daily basis, making sure that it stays the same.

10. Record mangrove height, root radius, and weight on a weekly basis, checking NH4NO3 levels to keep them constant.

Controls:

-Amount of water

-Location

-Sunlight

-Temperature

-Type of water

-Soil

-pH

-Salinity

-Humidity level

Real Time Adjustments and Monitoring

1. Propagules of Rhizophora mangle L. (Red Mangrove) were taken from the Ala Wai. Propagules ranging from 7 - 9 inches (17.8 – 23.0 cm) in length were used in this study.

2. Before the experiment, all propagules without leaves and roots were washed and rinsed with distilled water, blotted dry, and then weighed on an electronic scale of 0.001 precision. The exact lengths of the stems were measured.

3. While planting the propagules into the culture solutions, the bottom 2-in of each propagules were embedded in a plastic pot of sand/gravel. The pot is made of the bottom portion of a 2-liter coke bottle, approximately 3 – 3.5 in (8-9 cm) in height.

4. One propagule was placed in each plastic pot. A total of 15 propagules were planted and cultivated in water.

5. The propagules were kept in freshwater in greenhouse for 1 week before adding in any salt water.

6. The greenhouse temperature was adjusted to 82°F (27.7°C).

7. Illumination using 40-Watts lighting was placed in the greenhouse to supplement sunlight after day hours, from 7 pm – 11 pm every evening.

8. A week later after the propagules were placed in the greenhouse, prior to ammonium-nitrogen (N) and phosphorous (P) nutrient treatments, salt water of three different salinities (0, 85, or 342 mM, or equivalent to 0, 5, 20 ppt) were added into the plastic pots for a month to induce the development of cotyledons and roots.

9. Solutions of five NH4+(N) and PO43- (P) combinations were prepared and mixed with each of the three NaCl solutions to form the fifteen basic culture solutions for this experiment.

3 concentrations of NaCl

(salinity test)

0 ppt or 0 mM

5 ppt or 85 mM

20 ppt or 342 mM

5 combinations of NH4+ (N)

& PO43- (P)

0.10 mM-N 0.10 mM-N 0.50 mM-N 2.00 mM-N 2.00 mM-N

0.05 mM-P 0.50 mM-P 0.10 mM-P 0.05 mM-P 0.50 mM-P