PLANKTON

CONTENTS:

Introduction

Definations

Size Groups

Function Groups;

-Phytoplankton

-Zooplankton

-Bacterioplankton

Biogeochemical Significance of Plankton

Plankton Distribution

Role of Plankton in Aquatic Productivity

Reference

Plankton consist of any drifting organisms (animals, plants, archaea, or bacteria) that inhabit the pelagic zone of oceans, seas, or bodies of freshwater. Plankton are defined by their ecological niche rather than their genetic classification. They provide a crucial source of food to aquatic life.

DEFINITIONS
The name plankton is derived from the Greek word “planktos”, meaning “wanderer” or “drifter”. Although most of these organisms’ horizontal position is primarily determined by currents in the water bodies they inhabit; they cannot swim or move against currents, but some forms are capable of independent vertical movement in the water column and can swim up to several hundreds of meter vertically in a single day (a behaviour called diel vertical migration).
Based on the duration of their life cycle spend as being planktonic, plankton are in two forms:
Holoplankton- They are those organisms that spend their life cycle as part of the plankton e.g. most algae, copepods, salps, and some jelly fish.
Meroplankton- They are those organisms that are only planktonic for part of their lives (usually the larval stage), and then graduate to either the nekton or benthic (sea floor) existence e.g. sea urchins, starfish, crustaceans, marine worms and most fish.

SIZE GROUPS
Plankton are also often described in terms of size:
Picoplankton: smaller than 2mm; includes bacteria, prochlorophytes, and viruses.
Nanoplankton: between 2-20mm; includes diatoms, coccoliths, and silicoflagellates (pyrrophyta, chrysophyta, chlorophyta and xanthophyta)
Microplankton: between 20-200mm; includes most phytoplanktons; large diatoms, dinoflagellates and small zooplankton such as ciliates.
Macroplankton: between 200-2000mm; includes large zooplankton, copepods and invertebrate larvae.
Megaplankton: larger than 2000mm; includes fish larva and gelatinous zooplanktons such as jelly fish (ctenophores, salps, and pyrosomes).

FUNCTION GROUPS
Plankton are primarily divided into broad functional (or trophic level) groups as follows:
Phytoplankton- These are the autotrophic, prokaryotic or eukaryotic algae.
Zooplankton- They are the protozoans, metazoans or the eggs and larvae of lager aquatic animals
Bacterioplankton- These are the bacteria and archaea.
However, this scheme divides the plankton community into broad producer, consumer, and recycler groups. But, in the reality of it, the trophic level of some plankton is not straightforward; many species are mixotrophic depending upon their circumstances. For example, dinoflagellates are either photosynthetic bacteria or heterotrophic consumers. Even, the prokaryotic phytoplankton and the smallest ones among the zooplankton are bacterioplankton because they are also recyclers.

PHYTOPLANKTON
These are the autotrophic, prokaryotic or eukaryotic algae that live near the water surface where there is sufficient light to support photosynthetic activity. Phytoplankton fixed the inorganic carbon (as carbondioxide) utilized by marine and freshwater organisms into organic compound by their photosynthetic activity. And this makes the carbon available for higher trophic levels, thereby making them (phytoplankton) the primary producers; the base of the food web in oceans, lakes, rivers, and estuaries. They also absorb mineral elements such as nitrogen, phosphorous and iron and transformed these nutrients into organic matter using the light energy received by the chlorophyll they contain via the process of photosynthesis.
There are some major environmental factor influencing phytoplankton growths. They include temperature, light, nutrients availability. Phytoplankton growth is limited to the euphotic zone- the depth to which sunlight penetrates in the water. In the presence of nutrients such as nitrogen and phosphorous at desirable temperature, phytoplankton undergo rapid population growth making more food available to organism at higher trophic levels. But when this growth becomes very high i.e. phytoplankton bloom, this becomes harmful to the overall aquatic life. This is because most of the phytoplankton die and sink to the bottom where they decompose and this process depletes the dissolved oxygen of the water which is necessary for survival of other organisms in the water.
Among the more important groups of phytoplankton are the diatoms, cyanobacteria and dinoflagellates.
Diatoms
Diatoms are microscopic one-celled algae that have cell walls of silica and pectin. They may also occur as stalklike or branching colonies. Their cell walls consist of almost identical halves which are fixed together. Their cytoplasm contains the green pigment chlorophyll, but other pigment, especially the yellowish xanthophyll, gives the organism a golden-brown appearance. The reproduction is usually by cell division but periodical sexual reproduction by means of fertilization of haploid gametes may occur.
There are more than 8000 species of diatoms exist, mostly in freshwaters or on the surface layers of the oceans, where they are a major component of the plankton on which marine life depends.
Depending upon the classification system used, diatoms either make up Bacillariophyceae in the phylum Chrysophyta, or they make up the separate phylum Bacillariophyta.

Cyanobacteria (Blue-Green algae)
Cyanobacteria make up the phylum Cyanophyta in the kingdom Prokaryotae. This phylum contains about 150 genera and 2000 species. They are the blue-green algae. They are photosynthetic prokaryotes which are single-celled and lack enclosed nucleus and other specialized cell structures like mitochondria and chloroplasts. Cyanobacteria contain only chlorophyll “a” which is located in the chromatophores (not both chlorophyll “a” and “b” in the chloroplasts like green plants), where photosynthesis is carried out. The chromatophorebs are the infoldings of the plasma membrane. Cyanobacteria are distinguished from bacteria by the presence of internal membranes, called thylakoids (chromatophores). Cyanobacteria colour varies from blue-green to red or purple and is determined by the proportions of two secondary pigments which are; c-phycocyanin (blue) and c-phycoerythrin (red), which tends to mask the green chlorophyll present in the thylakoids.
Reproduction in cyanobacteria is by simple cell division, spore production or fragmentation of the filaments; forming singular cells, colonies, filaments or gelatinous masses. Although, most lack flagella and are non-motile, filamentous form such as Oscillatoria rotate in a screw-like manner, and the gelatinous forms glide along their slimy mucus.

Dinoflagellates
Dinoflagellates are unicellular aquatic organisms of phylum Dinoflagellata and they are always being covered with stiff cellulose plates that resemble armored helmets. Many species have unusual ornamentation, such as horns, spines or wings like. The armor is encircled by a narrow groove and there is a second groove that runs perpendicular to this narrow groove. Dinoflagellates are with two uneven flagella (for locomotion) that beat within these grooves, causing the dinoflagellates to spin like tops as they move through the water.
Several thousand species of dinoflagellates are known, most of which but not all contain chlorophyll and are photosynthetic. Most of the 130 genera and 2000 species in this phylum are planktonic and live in saltwater, although many are found in freshwater. Dinoflagellates show traits of both protozoans and algae because of their ability to photosynthesize and also absorb nutrients by being parasitic, or by ingesting organic particles. They are believed to second diatoms in contributing to primary production in aquatic ecosystem. Reproduction is by cell division.
However, certain species of the genera Gymmodinium and Gonyaulax produce a strong nerve toxin and responsible for the blooms called red tides. These blooms lead to the deaths of large number of fish and contamination of clams and mussels, which may be lethal to humans who eat them. Many species of dinoflagellates produce bioluminescence (i.e. emitting a pale-blue glow seen at night).

ZOOPLANKTON
Zooplanktons are planktonic free-floating animals of fresh and marine aquatic systems and are the major consumers of the organisms in the microbial food web. These organisms possess a wide range of feeding strategies. From nematocysts (sting cells) of cnidarians (e.g. jellyfish) to the complicated mouth path of copepods. Some are carnivorous (animal-eaters), some are herbivorous (plant-eaters), and some are omnivorous (eaters of plants and animals). The smallest zooplankton can be characterized as the recyclers of aquatic systems nutrients. The larger ones are food for forage fish species. These animals (zooplankton) can move by means of cilia, flagella, jointed appendages, jet propulsion, or tailed larva (as in tunicates to larval fish). Reproduction varies from asexual, to fission and fragmentation, to sexual reproduction; where some gametes are released into the water and fertilized, yet others retained and fertilized internally.
Zooplankton include many phylum; some live their entire life cycle in the water (holoplankton), whereas, some like the larval stages of fish and other benthic organisms (such as starfish) are only planktonic for part of their lives (meroplankton). The major zooplankton phyla include:
Protozoa- This group includes ciliates, dinoflagellates, foraminifera, and radiolarian.
Coelenterate (cnidaria) - They are typically known as jellyfish, the major group are Hydrozoa, Scyphozoa, and Anthozoa. The medusae of the hydrozoa group are the prominent members in zooplankton and the most common forms are aurelia, pelagia and siphonophores. They are gelatinous and are the major consumers of smaller zooplankton and some of the microbial food web.
Ctenophore- They are otherwise referred to as comb jellies, these posses eight “combs” rows of fused cilia. These animals consume phytoplankton and zooplankton and when they are abundant they can clear the water of food for other zooplankton.
Chaetognatha- They are the arrow worms and the common member of deep-water plankton. They are predacious carnivores that grasp their prey and paralyze them before ingesting them.
Annelida- This includes many species of marine polychaetes. Many of these organisms shed their gametes on the surface of water for sexual reproduction. Their larvae are abundant in the zooplankton community.
Mollusca- This includes gastropods larvae, pteropods and cephalopods (squid and octopus). They are consumers of larger zooplankton.
Echinodermata- This includes starfish, brittle stars and sea cucumbers. They are all meroplankton. Their larvae are a major presence in the zooplankton community.
Athropoda- This includes copepods, shrimps, crabs, lobsters and crustaceans. They are considered the major consumers of most of the organisms in the microbial loop. They can consume a wide range of food particles from nanoplankton to microplankton, as they mature. Copeopods are responsible for much of the carbon energy transferred from phytoplankton to larger zooplankton.
Chordates- They are the urochordates (tunicates), they include sea squirts and salps. Tunicates are now realized to be major consumers of phytoplankton and smaller zooplankton and can contribute to the entire food web dynamics as much as or even more than copepods.

BIOGEOCHEMICAL SIGNIFICANCE OF PLANKTONS
Aside from representing the bottom few levels of a food chain that lead up to commercially importance fisheries, plankton ecosystems play a role in the biogeochemical cycles of many important chemical elements. They play a significance role in the ocean’s carbon cycle. Phytoplankton fix carbon in sunlit surface waters via photosynthesis and through zooplankton grazing, this carbon enters the planktonic food web, where it is either respired to provide metabolic energy or accumulates as biomass or detritus. This tends to sink and in open ocean ecosystem away from the coasts, these lead to the transport of carbon from surface water to the deep. This process is known as the Biological pump, and is one of the reasons that oceans constitute the largest carbon sink on earth.
Also, plankton are often used as indicator and aquatic pollution because of their high sensitivity to water quality and environmental changes. They respond to low dissolved oxygen, nutrients levels and toxin contamination.
A good picture of current condition in any water body can be derived by studying the zooplankton indicator such as biomass abundance and species diversity.

PLANKTON DISTRIBUTION
Plankton are found in oceans, seas, lakes, and ponds. However the abundance and distribution of planktons varies horizontally, vertically, and seasonally.
(a) The primary cause of this variability is the availability of light. All plankton ecosystems are driven by the input of solar energy and this confines primary production to surface waters, and to geographical regions and seasons when light is abundant.
(b) The availability of nutrients is a secondary cause of the variability in the distribution of plankton. Large areas of the tropical and sub-tropical oceans have abundant light, but they experience relatively primary production due to poor availability of nutrients such as nitrates and phosphates. This is a result of large scale ocean circulation and stratification of the water column. Some regions of the oceans are unproductive despite significant concentration of macronutrients in them. Fields studies have found that the mineral nutrients are deficient in these regions, and that adding them can lead to the formation of blooms many kind of phytoplankton.
(c) Also, physical state of the water column and abundance of other plankton affect the variability of plankton distribution and abundance. Temperature changes may cause some plankters to migrate vertically to the cooler deeper water during the day light hour and then at night they migrate back to the surface (diel vertical migration). Also, for example, plankton such as jellyfish may migrate upward to the surface to locate food (protozoan) during the day light and downward to deeper water at night for bacteria.
However, all this above factors governing distribution of plankton may also responsible for diel vertical migration of plankton.
Plankton are found in the greatest abundance in surface water, they occur throughout the water column. Even at depth where no primary production occurs, zooplankton and bacterioplankton instead make use of organic material sinking from the more productive surface waters above.

ROLE OF PLANKTON IN AQUATIC PRODUCTIVITY
Plankton are the basis of biological productivity in the aquatic ecosystem. They are the major factor that biological processes in the aquatic system depend on. As the phytoplankton increase due to their ability to source energy (solar energy) from the sun to manufacture their food through the process of photosynthesis, the primary productivity for the food web in the aquatic system increases. High photosynthetic activity also contributes to increase in the water column pH by removing carbon dioxide and hydrogen ion from the water body thereby creating quality system for biological process in the aquatic system. At the same time, there will improvement in the addition of dissolved oxygen for aquatic animals, like fish. The phytoplankton also absorbs mineral elements such as nitrogen, phosphorous and iron, and transformed them into organic matter using the light energy received via photosynthesis thereby making more food available to organisms at the higher trophic levels. Consequently, increasing aquatic productivity. However, when the growth of these phytoplankton become very high, most die and sink to the bottom thereby increasing organic matter in the water column for increased microbial activities; leading to dissolved oxygen depletion in the system for aquatic life. This may also result in release of toxin to the water body. These reduce aquatic productivity.
Phytoplankton are consumed by zooplankton which are eaten by aquatic insects and small fishes and these small organisms serve as food for the larger animals in the water. Zooplankton are the sole prey items for almost all fish larvae as they switch to external feeding for nutrition and also adult fish and other large aquatic organisms. Even, they are the major source of nutrition for some larger like some whales and shark. The zooplanktons link the primary producers (phytoplankton) with the larger or higher trophic level organisms of aquatic world. Fish species rely on the density and distribution of zooplankton to coincide with first-feeding larvae for good survival of fish larvae and improve fish productivity and aquatic productivity at large.



REFERENCES
Barnes, R.S.K., and K.H. Mann. (1980): fundamentals of aquatic ecosystems. Oxford, U.K: Blackwell Scientific Publications.
Deidre, M.G. (2007): Plankton.http:www.waterencyclopedia.com/oc-po/plankton.html.
Martin, J.H., and S.E. Fitzwater. (1988): Iron-deficiency limits phytoplankton growth in the Northeast Pacific Subartic. Nature 331:341-343.
Valiala, Ivan. (1995): Marine Ecological Processes, 2nd ed. New York: Springer Verlag.

IMPORTANCE OF AQUATIC RESOURCES TO NATIONAL ECONOMY

Water is essential to life and is arguably our most precious resources. Water resources made up of various resources like: the water itself, animals and plants in it, and the minerals in it. These are referred to altogether as aquatic resources. These resources over the years have been tapped into in various ways to improve the standard of living of man. And the amount of the aquatic resources use in a country by its people keep increasing due to the population growth and profitable earnings got from them. The exploitation of aquatic resources increase in response to the growing of some developmental activities which include agricultural, industrial, recreational, domestic, fisheries and aquaculture, and navigation developments. All these developmental activities are what a nation can depend on for a sound outcome for her economy.

1. Agricultural importance:
Aquatic resources are of great use in agriculture for many decades, aquatic resources have been given a paramount contribution to agriculture such that it increases its contribution to the present day economy. Agricultural importance of aquatic resources depends on the types of agricultural operation: cropping or livestock practices in the area. However, on a generalized basis, aquatic resources have become helpful in agriculture in various ways which include:

Irrigation -: of the large amounts of water used by agriculture, by far the greatest percentage is used for the growth of crops. Even in some of the world, the grow of any crop is dependent solely on irrigation, while in other areas it permits more profitable crops to be grown or enhances crop yield. In most countries of the world, rainfall is inadequate for cropping and boost in agricultural yield therefore for improved cropping and agricultural outputs to cater for a country population throughout the year and to encourage and improve foreign earnings. Farmers are now being encouraged to supplement water supply from rainfall by providing artificial irrigation for their crops.

The key to the development of many countries lies in agriculture yield and to this irrigation has been of a great boost to agriculture yield; consequently improved standard of living. This is because there will be availability of food for household consumption and agricultural output for income generation. However, irrigation is worthwhile only where the costs of application over a period of time are covered by the increased return from the crops so grown. Also in the overview of it, irrigation serves as a source of employment either directly or indirectly for those that constructs the irrigation system and those that monitor the operation on the farms.

Source of fertilizer-: Aquatic plants accumulate large quantities of nitrogen and phosphorus in their tissues. These will therefore make them improve soil if applied as soil additives, thereby improving crop yield. The concept of biofertilizer; the growing of a minor crop that provides nutrients to a major crop, though relatively new to aquatic science; is already becoming popular. Azolla sp; a free floating fern which fixes nitrogen in a symbiotic relationship with the cyanobacterium Anabaena azollae, is widely use as a biofertilizer for rice. This has been extensively used in China to fuel rice production in waterlogged areas (Malby, 1986). Also, Ratchance (1972) describes the successful use of dried water hyacinth as a bedding material for cultivating mushroom, Volvaria sp.

Source of livestock food-: The primary value of livestock in agriculture is to convert plant materials which are unsuitable for human food into meat, hides and wools, dairy and other products. Livestock is a means of employment to those that engage in it. It also serves as a source of food such as meat, milk e.t.c. livestock improves market earning in the areas of production of meat, hides and wools, and dairy. For instance in Nigeria, the Housa people which are into cattle rearing greatly depend on this for their living and working out some international market participation for Nigeria in this area. Although in a country like Nigeria, livestock production system is predominantly nomadic and traditional yet its contribution to economy cannot be overemphasized. However, the animals depend on the natural forage legumes and grasses for sustenance but these are usually unavailable in the dry season. Thus the animals are been moved to the wetter region for suitable grazing. Also, some aquatic plants can be processed as animals’ feeds. For example, water hyacinth can be used in limited quantities in a mixture with other feeds by cattle, sheep, goats and other ruminants. Aquatic macrophytes used as fodder includes: Vossia cuspidata, Leersia hexandra, Bracharia mutica, Echinochloa pyramidalis. Also aquatic plants such as Lemna sp are fed into poultry to boost yield in Egypt.

2. Fisheries and Aquaculture:
The rearing of fish is an important and expanding part of the economy, particularly as far as the production of protein is concerned. Fish farming is carried out mainly in freshwaters or occasionally in brackish water in some tropical areas but marine fish farming is also now of importance in some parts of the world. With efficient methods and suitable conditions extremely high rates of production are possible compare with other forms of protein production.
Fisheries and aquaculture have been of great importance to a nation economy in the areas of fish production, raw materials to industries, employments, household and other purposes. Fish production in the recent years has been of importance in strengthening international relationship in terms of trade and other purposes. Nigeria Imports numbers of tons of fish annually to supplement her own domestic production. This has improved foreign income for those countries which Nigeria imports from and also allows Nigeria to be able to market her own products to those countries.

Many industries of the world today depend on the various raw materials from fisheries and aquaculture for finished products. Industries such as those into leather work also make use of fish skin and other water animals’ skin for products like drums, shoes, bags, wears materials. Some industries also process and canned fish products. All these are put into household usage and market to earn domestically and internationally.

Fisheries and aquaculture sector of a nation also make use of some finished products from small and large industries like those that manufacture boats, ships, nets, and other fishing equipments. These industries have greatly provided employment opportunities for those that work in them and they have contributed greatly to the improvement of both domestic and foreign earnings thereby improving the per capita income and standard of living of a country.

Also, through fisheries and aquaculture a great deal of employments has been generated for those involved either directly or indirectly. Those into fishing gear fabrication, canoe building, also those local fishermen are gainfully employed through fisheries. For example in Nigeria those in River Niger area involve themselves in activities like canoe building, net fabrication, and fishing and fish sales to earn a living thereby reducing unemployment in the area. Also those that involve in the construction and operation of cold rooms get pay from it. Through all these and more exploitation of aquatic resources through fisheries and aquaculture have been able to contribute greatly to the reduction in the level of unemployment and to the improvement in income earnings.

Also, those involve in shrimps, corals e.t.c. production help in food production and also earn living from it. In the USA and Japan, oysters are provided on a considerable scale. Also, in Europe the husbandry of mussels in the bay of Vigo, Spain, is of economic importance. In Japan, 230,000 tons of marketable oysters are produced annually (Meixer, 1977). All these also provide employment and income thereby boosting economy.

3. Industrial Importance:
The location of many industrial areas in the world depends on the availability of suitable water supply. Those supplies are from reservoirs, canals, lakes, rivers, estuaries or even the seas. Hopthrow (1963) estimated that in Great Britain about 35% of the public is utilized by industries, but much more than this is obtain from other sources. It is also estimated that 15% of world water use is industrial. However, major industrial users include power plants, which use water for cooling or as power source (i.e. hydroelectricity), ore and oil refineries, which use water in chemical processes, and manufacturing plant which use water as solvent. All these industries develop national economy by providing employment for both skilled and unskilled labours, producing products such as building materials, household materials, and other products for domestic and international trade. For instance in Nigeria, Kanji dam supply energy i.e. electricity at low cost to most if not all industries in Nigeria for their various operations, although, the electricity supply still need to be improved on. In Scotland, more than 30% of the electricity use is generated by hydroelectricity station (after Aitken, 1963). These hydroelectric dams also generate energy for household consumption and employment for their workers. Also in the case of Kanji dam in Nigeria, hydroelectric power supply has strengthened international relationship between Nigeria and country like Benin republic and these also yield some benefits monetarily for Nigeria.

Oil refineries, like petroleum; different grades of petroleum and natural gas exist and lots of these come from the sea. Varieties of raw materials are got from petroleum to serve various industries like agro-allied, household, construction e.t.c. industries. Also, jobs for those refineries workers. In a country like Nigeria petroleum and its products have been the dependent of its economy.

Aquatic plants are of a wide range of materials that could serve the needs of innovative industries. These materials could be use for construction, matting, bedding, and pulp/paper making. In Nigeria the mature silky inflorescences of the spike of Typha australis for example, are used in stuffing pillows and mattresses and the fragrant dry tuber of Cyperus maculates is sold in northern Nigeria as perfume. In some countries mangroves are being exploitated and shipped for pulp and particle board. Also, aquatic plants like Nypa fruticans yields alcohol, sugar and vinegar (Maltby, 1986). Ola-Adams (1990) affirmed the use of Phoenix rectinata in the weaving of mats, sieves and bags and these are now gaining internationally recognition in the area of art and culture. Aquatic plants also make available alternative raw materials to industries, for example; Laguncularia racemosa yields timbers, tannin and dyeing materials for paper, hides and textile industries.

4. Navigation importance:
Inland water systems have always been of importance for human transport from earliest times, now adequate navigation channels for large vessels coming from sea to inland ports are of great importance to industries and commerce of a nation. Transport via waters is important economically in the area of importation and exportation of goods and international relationship. Unlike before, now substantial investments are being directed to water ways to expand the natural navigable systems, thus, enabling ships to pass from sea port right into inland industrial areas. These development and canalization of water ways have proved successful in many countries. For example in North America, the St. Lawrence sea way, with only seven locks, developed traffic of over twenty million tonnes per year within three years (Marsh, 1963). Also water ways have helped in the haulage of some goods and industrial products that are difficult to be transported by road or air to various destinations in the world. Ports are also built on seas to facilitate foreign trades and generate income for the government. Also those ports provide employments for enormous number of people.

5. Recreational/Tourism Importance:
The increasing human population and their affection for leisure and pleasure have placed an enormous demand on natural resources for recreational purpose. This is especially true for water bodies which are often the focus for variety of recreational activities such as sailing, power-boating, water skiing, general picnicking, relaxation and angling.

However, among these recreational activities, angling (i.e. sport fishing) is highly economical in terms of domestic and foreign earnings. Sport fishing attracts tourists from all over the world. Moreover, today fishing for fun is of continental focus and even great investments are put into it by individuals and government for better income yield. For example, in Nigeria the Argugun fishing festival of Kebbi state attracts tourists from all over the world to Nigeria. This does not only strengthen international relationship, it also attracts foreign investors and even the anglers win laurels which are of monetary value.

Some water bodies are used as tourist centers to generate income, for example in Nigeria, we have Ikogosi warm spring in Ekiti state, Wikki spring in Bauchi e.t.c. and at the same time, those water bodies help in the attraction of investors and national development. Natural tourist centers like these are accepted as having a wide variety of uses including nature study, photography, fishing, camping, and picnicking, as well as economic pursuits. While the primary interest in these areas may be wildlife or recreation; economic operations yield substantial financial returns and even increase the value of the area for the wildlife or recreational activity concerned.

Some fishes are of aesthetic value and they are the target in aquarium trade and ornamental fishing. Fishes like the Peacock cichlid, Cichla ocellaris are used in ornamental fishing in Florida, yellow perch (perca flaviscens) of North America are of good reputations as panfishes.

More so, there are aquatic plant species of great potential in horticulture and recreation. Of greater potential are some members of the Family Ordiidaceae such as Eulophia caricifolia, E. hosfalhi, and E. angolensis. The presence of aquatic plants has favoured the possibilities of most water bodies being developed into recreation centers that include bird-watching and nature photography. In Kenya (MENR, 1981) the annual income from visitors to Amboseli National park was estimated as US$1.3million in 1979, where the aquatic system are one of its principal attractions.

6. Household and Health importance:
It is estimated that 15% of world-wide water use is for household purposes this include drinking, bathing, cooking, sanitation and gardening (Peter Gleick, 2001). Aquatic animals are use as food for human consumption, among which fishes are of high quality supply. In about 25,000 species of fish that are caught regularly in water, about 200 species are used as food. Among fishes used for food include herines, sardines, sharks e.t.c. Other animals such as crustaceans, molluscs and mammals make supplement source of food available to man. In Asia, according to Pillay (1976) 15,000 tons of shrimps and prawns are harvested annually for household consumption. In Korea phytoplankton production has reached 20,000 metric tons annually for food. In some part of East Africa fish oil are extracted to burn lamp to produce light.

Aquatic resources have been of great importance in the health sector as it serves so many functions which directly or indirectly generate revenue for individuals and government. Some aquatic products are used in the production of modern drugs and pharmaceuticals. For example fish oil which is reach in vitamin is used in the manufacture of drugs like “seven seas” popularly called cod liver oil, omega H3; both drugs are used as supplements to give vitamins and are being produced by pharmaceutical industries for private and public hospitals. This directly or indirectly generates income for the government and individuals through tax and sales. Also antibodies are extracted from sponges to fight penicillin resistant bacteria. Some pharmaceutical industries also extract body fluid of certain snails and oysters and processed it into medicine as their finished product to fight viral diseases. Greatly, aquatic resources have helped in the improvement of health of people and “health is wealth” they say. Aquatic plants are used in curative therapy in traditional communities. Kio and Ola-Adams (1987) reported that Polygonum senegalense is pounded with native hydrated sodium carbonate and rubbed on the limbs for rheumatic and other swellings. Obot and Ayeni (1987) also reported that Pistia stratiotes is used as parts of concoction for the treatment of flu.


References
1. Wortley, J. (1995): Recreational fisheries. In K.T. O'Grady (ed.) Review of inland fisheries and aquaculture in the EIFAC area by subregion and subsector. FAO Fisheris Report 509, Suppl. 1, 60-72.
2. MacLock, B. and J. Thompson. (1996): Characterization of Aquatic Uses within the Peace, Athabasca and Slave River Basins. Northern River Basins Study Synthesis Report No. 7.
3. Bocek, A. (2005):Water harvesting and aquaculture for rural development. http.www.ag.auburn.edu/fish/icae/transport.htm
4. Online cited. (2005): Aquatic Plant Resources of Nigeria. http.www.fao.org/DOCREP/005/T3660E/T3660E03.htm
5. Online cited: Water Resources.http.en.wikipedia.org/wiki/water_resources.htm

Aquatic Resources; Renewable or Non-renewable

Aquatic resources are fundamental to livelihood of man and they are a vital component in the well being of all living organisms be it plants or animals. Aquatic resources are the resources that take their source from water. They are useful or potentially useful to humans, which may be in agricultural, industrial, household, recreational, research, navigation, health and environmental activities. Virtually all of these human uses require freshwater. About 97.5% of water on the earth is salt water, leaving only 2.5% as freshwater. Water resources demand and already exceed supply in the world and as world population continues to rise at an unprecedented rate, many more imbalances should be expected in the supply of aquatic resources.

Aquatic resources can be grouped into two categories; renewable and non-renewable. A renewable resource is one that may be replaced over time by natural processes, such as fish populations or water vegetation, or is inexhaustible. Non- renewable resources are those in limited supply that cannot be replaced or can be replaced only over extremely long periods of time. Non-renewable aquatic resources include fossil fuels and mineral deposits, such as petroleum, iron ore and gold ore. Whether renewable or non-renewable aquatic resources are faced with over exploitation by man and measures should be taken to ensure a sustainable use and protection of these aquatic resources. This type of measure of ensuring sustainable use and protection of aquatic resources is referred to as conservation and management of aquatic resources.

However, the goal of conservation and management of aquatic resources for renewable resources is to ensure that resources are not consumed faster than they are replaced. While conservation and management activities for non-renewable resources focus on maintaining an adequate supply of these resources well into the future. Aquatic resources are conserved and managed for their biological, economic and recreational values, as well as their natural beauty and importance to local cultures.

The challenge of conservation and management of aquatic resources is to understand the complex connections among aquatic resources and balance resources with protection to ensure an adequate supply for the future usages. In order to accomplish this goal, a variety of conservation and management methods are used. These include reducing consumption of resources; protecting them from contamination or pollution; recycling resources when possible; and fully protecting, or preserving resources.

The water as aquatic resource critically needs to be taking into consideration when it comes to conservation and management of aquatic resources. Clean freshwater resources are essential for drinking, bathing, cooking, irrigation,, industry and for plant and animal survival. Unfortunately, the global supply of freshwater is distributed unevenly and even these freshwater are under severe and increasing environmental stress because of over use, water pollution and ecosystem degradation. Over 95% of urban sewage in developing countries is discharged untreated into surface waters such as rivers and seas. These sewages destroy the water for house use and adversely affect the fresh and other aquatic animals in the water. Fertilizers apply to crops in the areas around water body find their way into the water through runoffs also pollute the water body and affect the organisms in the water and may eventually leads to deaths of fish and other water organisms. Pollution in water body reduces biodiversity of organisms in the water leaving only those organisms that can tolerate the pollutants and their effects. Therefore, water conservation requires a reduction in wasteful practices like inefficient irrigation, reforms in agriculture and industry, strict pollution controls should be embarked on. Law should be made by the government to these effects. Farmers should be trained through seminars and workshops on how to practice efficient agricultural practices that will support water conservation. And industrial personnel should also be trained on the proper ways of disposing their wastes. Punishment should be attached to improper disposal of waste into water body.

Also, water supplies can be increased through effective management of watersheds. By restoring natural vegetation to forests or fields, communities can increase the storage and filtering capacity of these watersheds and minimize wasteful flooding and erosion.

The aquatic organisms (plants and animals) most especially fishes are affected by the above mentioned problems (i.e. inefficient agricultural practices like inefficient irrigation, and dumping of industrial waste). Aquatic plants are very important in aquatic system in so many ways which include:
- Production of oxygen for the water organisms through photosynthesis
- Provision of food for aquatic organisms (primary producers)
- Direct or indirect provision of shelter for fish and invertebrates
- Consolidation of river bed and banks
- Marginal plants provide resting sites and food source for waste birds
- Provision of aesthetic appeal to water body
- Provision of spawning medium for some fishes.

These important plants species are often exploited by man activities like encroachment, navigation, construction, boating and even fishing and cultural purposes. When this problem of poor exploitation occur the animals depending on those plants species are affected due to the low production of primary producers to produce food for the animals and eventually result in low aquatic productivity (fish kills may result). Also plants population increases in some aquatic environment due to their proximity to sewage effluent and agricultural practices (fertilization) that release nutrients (nitrogen and phosphorous) to the water through runoffs. This causes increase in the growth of aquatic weeds and algae bloom that often cause fish kills and inhibit the growth of other animals in the water. Means of controlling these weeds and blooms to desirable level in the aquatic body to provide better survival for endangered animals’ species should be put in place. Control can be by mechanical measures i.e. by hand picking.

Aquatic animals such as fish, crustaceans (crabs, crayfish) e.t.c are important for man livelihood. They are rich in protein. These animals are good means of recreation, industrial, mechanical and household purposes. Due to their enormous usefulness man over exploit them for their own use. Fish population is in a drastical decline and this may be a attributed to:
- Over harvesting as a result of human population growth and economic importance.
- The use of modern, more efficient gear such as monofilament nets.
- Environmental degradation.

Today scientists consider many fisheries to be fished beyond the capacity of the resources. Current harvest rates are thought to be unsustainable-that is, unable to be maintained year after year without depletion of the fish stock. Experts believed that increase in world fish supply will require better management of the resources as well as the increased use of fish farming or aquaculture. Fisheries management includes:
i. Setting policies and objectives for each fishery or stock to be managed.
ii. Determining and implementing the measures necessary to reach the objectives.
iii. Consulting and negotiating with other users of the resources or area.
iv. Reviewing management objectives and measures to ensure adequacy and adoption.
v. Accessing by government, users and the public on management performance.

In conserving fisheries dams, ponds can be constructed for aquaculture purpose to rear fish and other aquatic animals like crabs, crayfish e.t.c. Also those constructed reservoirs, dams, and ponds are means of conserving water itself. Laws should be made by government on gear usage; gear that catch bigger fish and leave the smaller ones should be used for echo-sounders, light to attract fish to gear, electric fishing gear to catch large population of fish which is posing a big threat (decline) to fish supply and some species are even going into extinction. In this case government should make laws that will control the quantity of fish caught and the size of fish to be caught. Also, endangered species should be collected from the wild for aquaculture to prevent them from going into extinction. For example, in Japan, the salmon fishery and several other fisheries depend upon hatcheries- where fish reproduction and survival is enhanced- to provide the young fish (Anderson, 2007). Infact, now aquaculture production is becoming an essential part of the world’s fish supply, aquaculture has steadily increased over the past two decades and now accounts for nearly 20 percent of world harvest (Anderson, 2007). Another, greatest challenge in fisheries management is the control of bycatch; the unintentional killing of species not intended to be caught, such as low value fish, immature fish or even marine mammals. Although measures such as controlled use of gear have been employed, the wasteful harvest of bycatch animal is still a major problem world wide.

The world energy supply depends on many different resources including aquatic resources; water is significant in generating hydroelectric powering many countries like Nigeria. Fossil fuels (petroleum, coal) account for more than 90 percent of global energy production (Hartman, 2007). They are non-renewable, therefore, there is need to increase their conservation and the use of renewable energy resources. Renewable alternatives such as solar energy (using the energy from the sun), wind energy (using the energy of the wind or air currents), and geothermal energy (using energy contained in hot-water deposits within the earth crust) which have found to be efficient and practicable by experts should be diverted to for energy supply for proper conservation of those fossil fuels. Laws to guide exploitation of these fuels should also be made.

Minerals deposits in aquatic environment such as iron, and gold ore are quickly running off and they are non-renewable. Therefore, drastical measures must be taking to conserve them. Recycling of products made from these minerals should be employed by industries. Recycling is the collection, processing and reuse of materials that would otherwise be thrown away; this process reclaims the original materials and uses it in new products; by this exploitation of ore will be reduced, thereby conserving these ores deposits.

However, these (aquatic resources mentioned in this paper) and many more are essential for humans livelihood therefore all hands must be on desk; including the government, users and the masses, to conserve the non-renewable aquatic resources and manage the renewable ones for continuous optimum supply to meet humans demands.






References
Anderson, J.L. (2007); Fishery management. Microsoft student 2008 DVD.

Redmond, W.A. (2007): Endangered! Exploring a world at risk. http://www.amnh.org/ exhibition.

Online cited: Water Resources.http.en.wikipedia.org/wiki/water_resources.htm

Steven, C. and S. Susk (2007): Conservation of aquatic resources through the use of freshwater
protected areas: Opportunities and challenges. Biodiversity and Conservation, vol. 16, No.7, pp2015-2029(15).

Thanks for time

©Thomas Idowu