Edna Patricia P. Mendoza
MS Environmental Science
2007-78411
A comparison of marine waters, fresh/terrestrial waters, and estuaries
The earth is an enormous ecosystem in which the living and nonliving worlds interact through four major subsystems: the atmosphere, hydrosphere, geosphere, and biosphere. In the hydrosphere where the planet’s waters are contained, three major types of water are connected and interact with each other: (1) the marine waters, (2) the freshwaters or terrestrial waters, and (3) the estuaries. They vary in their composition and their physical, chemical, and biological processes.
Marine Waters
Marine waters comprise the North and South Pacific, North and South Atlantic, Indian and Arctic Oceans, and the Antarctic waters or seas and covers 71% of the earth surface (See Table 1). The average salinity of seawater is 35 ppt where the dominant anion is chloride, 19 ppt by weight, and the dominant cation is sodium, 10.5 ppt by weight (Barnes & Hughes, 1982). Salinity is due to the gradual concentration of dissolved chemicals eroded from the Earth's crust and washed into the sea. Solid and gaseous ejections from volcanoes, suspended particles swept to the ocean from the land by onshore winds, and materials dissolved from sediments deposited on the ocean floor have also contributed to the salinity (Swenson, USGS).
The ocean floor is mostly covered with loose sediment from particles which settled down from higher regions. The sediments reach thicknesses of thousands of meters and the great pressure exerted by the weight of such masses of materials compresses the bottommost portion into sedimentary rock. The nature of the uppermost layer of benthic sediment will be determined by whether it is organic or inorganic in origin. The nature of the bottom will be affected (Reid & Wood, 1976) too, by the types of organisms of which it is composed.
Marine organisms that thrive in the ocean can be affected by some physical factors of the ocean such as tides, waves, circulation cells, and settling velocities. Tides have an effect on the shoreline species that have special adaptations to the semidiurnal changes in the environment. Organisms living here must be able to tolerate extended periods of immersion and exposure which can last for weeks or even months Waves affect marine organisms, both in the open ocean as well as near the shore, by alternately raising and lowering them. Waves are important primarily because (Reid & Wood, 1976) they circulate the upper layers of the water (mixing heat, dissolved nutrients, and oxygen), they cycle plankton in and out of the bright surface light, and they disperse the gametes and larval forms of many species. A circulation cell, a block of surface water where water cycles down and up beneath the surface, may affect marine organisms by changing its temperature while cycling and picking up nutrients and drifting organisms along the way; thus the rising current between cells is often cooler and richer in food than the surrounding water (Reid & Wood, 1976). Because of this, the distribution of autotrophic organisms in the surface layers may be affected. Settling velocity is the rate at which a particle settles toward the bottom of a body of water (Reid & Wood, 1976). They are important to the distribution of suspended particles and small organisms throughout marine waters.
Aside from physical factors, chemical and biological processes occurring in the oceans may affect marine organisms as well. Marine organisms can be categorized into two large groups (Barnes & Hughes, 1982) on whether they live in the water mass (pelagic) or in the bottom sediments or rock (benthic). A minor, third category is required for those who straddle the air-water interface (pleustic). Pelagic organisms occupy a large portion of the group and it includes the plankton and nekton. Plankton varies in sizes ranging from less than1μm in diameter to 0.5m (Table 2). Phytoplankton, with exception of the littoral zone, are the sole source of the food energy which fuels the entire oceanic food web (Barnes & Hughes, 1982). Phytoplankton utilize light to synthesize complex organic molecules by undergoing different processes; however, the most frequent process in the oceans as a whole (Barnes & Hughes, 1982) is the photosynthetic fixation of carbon by the phytoplanktonic protists using water as the hydrogen donor (Fig.1). Photosynthetic fixation is responsible for the primary generation of organic compounds in the sea. Clearly, therefore, all primary fixation of organic compound by photosynthetic organisms must be a phenomenon confined to the surface waters. There are factors limiting primary production. These are (Barnes & Hughes, 1982): (1) light, (2) turbulence, (3) nutrients, and (4) grazing. All can have an interruption on the magnitude of primary production.
Freshwater/Terrestrial Waters
Freshwaters, in layman’s term, are waters that have no salty taste. They are categorized into two: (1) lentic habitats, and (2) lotic habitats. Lentic habitats are “standing waters” or slow-moving waters such as lakes, ponds, swamps, and marshes; and lotic habitats are flowing-water habitats and are derived from the hydrologic cycle. Examples of lotic habitats are rivers, streams, brooks, groundwater, and channels of other sorts.
Swamps and marshes are relatively easy to distinguish from one another. The former are wet lowlands which support mosses and shrubs, together with relatively large trees such as cypress and gum while the latter are broad, treeless wetland areas, occupied by abundant grasses, rushes, and sedges (Reid and Wood, 1976). Neither of them is a completely aquatic habitat. They are also called “terrestrial” wetlands which are important to wildlife habitant because biogeochemical processes in wetland ecosystems are mediated by soils with low redox potentials (Class handouts). Net primary productivity in wetland ecosystems varies widely, depending upon nutrient supply (Brinson et al., 1981). Net primary production (NPP) is directly related to nutrient inputs in many swamp forests (Brown, 1981), and productivity is highest in wetlands that are seasonally dry, allowing for periods of rapid nutrient turnover when soils are exposed to oxygen.
Lakes and ponds are harder to distinguish from one another because neither term is necessarily restricted to any one kind of environment. They also usually change in character with the passage of time. For laymen and scientists alike, the term pond generally suggests a small, quiet body of water, shallow enough for rooted plants to grow from one shore to the other. For lakes, they are larger bodies of standing water and occupy distinctive basins. The shores and lake bottoms near shore of typical older lakes are composed of coarse gravel and rocks. Mud and fine materials occur in the deeper regions of the lakes and unconsolidated or soluble materials such as sands and limestone are rather quickly eroded to develop gently sloping lake shores of sand and near shore bottoms of fine sedimentary particles (Reid & Wood, 1976). The physical properties of water have a significant control on net primary productivity and nutrient cycling in lakes. Sunlight warms the surface waters, but light energy is rapidly appeased with depth. Since freshwater shows its greatest density at 4OC, stratification of water develops in deep lakes consisting of the epilimnion, warm surface waters; and hypolimnion, cooler, deep waters. During summer stratification, phytoplankton are confined to the surface layers that contain only a small portion of the total nutrient content of a lake (Class handouts). During these periods, NPP in the epilimnion depends on direct nutrient inputs to the surface waters (Schindler, 1978) and on nutrient regeneration in the epilimnion (Fee et al., 1994). Surface waters have high redox potential but low quantities of available nutrients are in the epilimnion as a result of rapid uptake by phytoplankton.
In terms of physical characteristics, fast-flowing streams differ from lakes in various ways as follows (Sigee, 2005): (a) the water body is transient (low retention time) at any particular site. It is also typically highly turbulent, with no thermal or chemical stratification. Both of these factors combine to limit the development of a planktonic community (phyto- and zooplantkton), which may be significant in larger rivers but does not normally make a major contribution to the stream community; (b) the substratum (bed) of streams is typically well aerated and exposed to light, and is the major site of algae and associated biota; (c) inflow from the catchment area is typically periodic, giving rise to marked fluctuations on water level and flow velocity (high and low flow periods). Concentrations of dissolved particulate matter, which are mainly derived from the catchment area, typically follow this periodicity in inflow. Because of this, stream ecosystems are dominated by benthic organisms. Some large rivers occupy an intermediated position between lotic and lentic environments, with limited movement of the water body, restriction of turbulence to the upper layers and sediments that are exposed to minimal water flow and are in permanent darkness (Sigee, 2005). In this situation, rivers may resemble lakes in showing chemical and thermal stratification and develop substantial phytoplankton and zooplankton.
Groundwater is the water contained in the rocks below the water table and usually is of more uniform volume than vadose water (water in the soil above the water table) (Reid & Wood, 1976). Many of the factors that influence the surface water composition also influence groundwater composition. Groundwater is always in contact with rocks and minerals and moves more slowly than surface water. Because of this, groundwater regularly contains more dissolved minerals than surface water. When water seeps below the surface, it passes through the soil where microbial respiration processes release CO2. As water encounters the CO2, the pH is lowered, and the water can dissolve more minerals. At higher temperatures, minerals dissolve more readily. Deep groundwater tends to be warmer and as a result, has higher mineral content. Ultimately, what controls the composition of groundwater is (waterencyclopedia.com): (1) the geologic materials groundwater is moving through; (2) the type of reactions taking place; and (3) the contact time, or length of time groundwater has been in contact with the rocks. The contact time may vary from a few days to more than 10,000 years. Knowledge of water–rock–organism reactions helps hydrologists unravel the origin of a specific water parcel. Carefully analyzing the water allows them to identify what types of reactions have affected the water, and to understand the geological and ecological history of the area.
Estuaries
At and near the region where the freshwater from the land meets the salt water of the sea, a distinct aquatic environment occurs – the estuary. It is defined (Dionne, 1963) as follows: an inlet of the sea reaching into a river valley as far as the upper limit of tidal rise, usually being divisible into three sectors: (a) a marine or lower estuary, in free connection with the open sea; (b) a middle estuary, subject to strong salt and freshwater mixing; and (c) an upper or fluvial estuary, characterized by fresh water but subject to daily tidal action. The estuary is an ecotone, a rather complex “buffer zone”, sharing some characteristics of both types of aquatic ecosystems, but identical to neither (Reid & Wood, 1976). It is an ephemeral feature in a long-term, geologic history and must be regarded as a dynamically evolving land-form that will go through a life cycle from valley creation (by fluvial or ice erosion), followed by the drowning phase (eustatic rise of sea level, with or without vertical crustal motion), and ending with the progressing infilling (mainly deltaic, but some offshore sedimentation, aided by eustatic drop with or without vertical crustal motion) (Fairbridge, 1961).
There are some physical, chemical, sedimentological, and biological features of the estuarine environment that are potentially important controls of the nutrients, dissolved gases, and the general biogeochemistry in estuaries. These controlling influences may be summarized as follows (Aston, 1978): (a) the tidal mixing of fresh and seawaters on a semi-diurnal or diurnal time scale, with corresponding changes in the volume of water in an estuary, produce temporal changes in the contributions of nutrients and dissolved gases from marine and fresh water sources; (b) the circulation, and especially the stratification of some estuaries, generates the possibility of vertical and horizontal variations of the concentrations of nutrients and dissolved gases within an estuary; (c) estuarine topography may give rise to particularly restricted calculations where the mixing of external seawater with the estuarine waters is greatly reduced, and the restricted mixing leads to unusual chemical environments; (d) the current regime on coastal waters and estuaries leads to the deposition of various types of sedimentary material. The deposition and resuspension of sediments in estuaries may influence the budgets of dissolved constituents in estuarine waters, including nutrients and gases; (e) chemical reactions occurring during the mixing of river water with seawater may lead to the removal or addition of the dissolved nutrients. Also, the changes in temperature and salinity during estuarine mixing influence the solubility of dissolved gases and thus influence their removal or addition in an estuary; and (f) biological production and metabolism have significant influences on the occurrence and distribution of nutrients and some gases, e.g. CO2 and O2 in estuarine waters. Estuaries are environments with special problems for biological organisms, so that there is a tendency to a decrease in species diversity in estuaries. This decrease does not, however, imply that productivity is low.
MS Environmental Science
2007-78411
A comparison of marine waters, fresh/terrestrial waters, and estuaries
The earth is an enormous ecosystem in which the living and nonliving worlds interact through four major subsystems: the atmosphere, hydrosphere, geosphere, and biosphere. In the hydrosphere where the planet’s waters are contained, three major types of water are connected and interact with each other: (1) the marine waters, (2) the freshwaters or terrestrial waters, and (3) the estuaries. They vary in their composition and their physical, chemical, and biological processes.
Marine Waters
Marine waters comprise the North and South Pacific, North and South Atlantic, Indian and Arctic Oceans, and the Antarctic waters or seas and covers 71% of the earth surface (See Table 1). The average salinity of seawater is 35 ppt where the dominant anion is chloride, 19 ppt by weight, and the dominant cation is sodium, 10.5 ppt by weight (Barnes & Hughes, 1982). Salinity is due to the gradual concentration of dissolved chemicals eroded from the Earth's crust and washed into the sea. Solid and gaseous ejections from volcanoes, suspended particles swept to the ocean from the land by onshore winds, and materials dissolved from sediments deposited on the ocean floor have also contributed to the salinity (Swenson, USGS).
The ocean floor is mostly covered with loose sediment from particles which settled down from higher regions. The sediments reach thicknesses of thousands of meters and the great pressure exerted by the weight of such masses of materials compresses the bottommost portion into sedimentary rock. The nature of the uppermost layer of benthic sediment will be determined by whether it is organic or inorganic in origin. The nature of the bottom will be affected (Reid & Wood, 1976) too, by the types of organisms of which it is composed.
Marine organisms that thrive in the ocean can be affected by some physical factors of the ocean such as tides, waves, circulation cells, and settling velocities. Tides have an effect on the shoreline species that have special adaptations to the semidiurnal changes in the environment. Organisms living here must be able to tolerate extended periods of immersion and exposure which can last for weeks or even months Waves affect marine organisms, both in the open ocean as well as near the shore, by alternately raising and lowering them. Waves are important primarily because (Reid & Wood, 1976) they circulate the upper layers of the water (mixing heat, dissolved nutrients, and oxygen), they cycle plankton in and out of the bright surface light, and they disperse the gametes and larval forms of many species. A circulation cell, a block of surface water where water cycles down and up beneath the surface, may affect marine organisms by changing its temperature while cycling and picking up nutrients and drifting organisms along the way; thus the rising current between cells is often cooler and richer in food than the surrounding water (Reid & Wood, 1976). Because of this, the distribution of autotrophic organisms in the surface layers may be affected. Settling velocity is the rate at which a particle settles toward the bottom of a body of water (Reid & Wood, 1976). They are important to the distribution of suspended particles and small organisms throughout marine waters.
Aside from physical factors, chemical and biological processes occurring in the oceans may affect marine organisms as well. Marine organisms can be categorized into two large groups (Barnes & Hughes, 1982) on whether they live in the water mass (pelagic) or in the bottom sediments or rock (benthic). A minor, third category is required for those who straddle the air-water interface (pleustic). Pelagic organisms occupy a large portion of the group and it includes the plankton and nekton. Plankton varies in sizes ranging from less than1μm in diameter to 0.5m (Table 2). Phytoplankton, with exception of the littoral zone, are the sole source of the food energy which fuels the entire oceanic food web (Barnes & Hughes, 1982). Phytoplankton utilize light to synthesize complex organic molecules by undergoing different processes; however, the most frequent process in the oceans as a whole (Barnes & Hughes, 1982) is the photosynthetic fixation of carbon by the phytoplanktonic protists using water as the hydrogen donor (Fig.1). Photosynthetic fixation is responsible for the primary generation of organic compounds in the sea. Clearly, therefore, all primary fixation of organic compound by photosynthetic organisms must be a phenomenon confined to the surface waters. There are factors limiting primary production. These are (Barnes & Hughes, 1982): (1) light, (2) turbulence, (3) nutrients, and (4) grazing. All can have an interruption on the magnitude of primary production.
Freshwater/Terrestrial Waters
Freshwaters, in layman’s term, are waters that have no salty taste. They are categorized into two: (1) lentic habitats, and (2) lotic habitats. Lentic habitats are “standing waters” or slow-moving waters such as lakes, ponds, swamps, and marshes; and lotic habitats are flowing-water habitats and are derived from the hydrologic cycle. Examples of lotic habitats are rivers, streams, brooks, groundwater, and channels of other sorts.
Swamps and marshes are relatively easy to distinguish from one another. The former are wet lowlands which support mosses and shrubs, together with relatively large trees such as cypress and gum while the latter are broad, treeless wetland areas, occupied by abundant grasses, rushes, and sedges (Reid and Wood, 1976). Neither of them is a completely aquatic habitat. They are also called “terrestrial” wetlands which are important to wildlife habitant because biogeochemical processes in wetland ecosystems are mediated by soils with low redox potentials (Class handouts). Net primary productivity in wetland ecosystems varies widely, depending upon nutrient supply (Brinson et al., 1981). Net primary production (NPP) is directly related to nutrient inputs in many swamp forests (Brown, 1981), and productivity is highest in wetlands that are seasonally dry, allowing for periods of rapid nutrient turnover when soils are exposed to oxygen.
Lakes and ponds are harder to distinguish from one another because neither term is necessarily restricted to any one kind of environment. They also usually change in character with the passage of time. For laymen and scientists alike, the term pond generally suggests a small, quiet body of water, shallow enough for rooted plants to grow from one shore to the other. For lakes, they are larger bodies of standing water and occupy distinctive basins. The shores and lake bottoms near shore of typical older lakes are composed of coarse gravel and rocks. Mud and fine materials occur in the deeper regions of the lakes and unconsolidated or soluble materials such as sands and limestone are rather quickly eroded to develop gently sloping lake shores of sand and near shore bottoms of fine sedimentary particles (Reid & Wood, 1976). The physical properties of water have a significant control on net primary productivity and nutrient cycling in lakes. Sunlight warms the surface waters, but light energy is rapidly appeased with depth. Since freshwater shows its greatest density at 4OC, stratification of water develops in deep lakes consisting of the epilimnion, warm surface waters; and hypolimnion, cooler, deep waters. During summer stratification, phytoplankton are confined to the surface layers that contain only a small portion of the total nutrient content of a lake (Class handouts). During these periods, NPP in the epilimnion depends on direct nutrient inputs to the surface waters (Schindler, 1978) and on nutrient regeneration in the epilimnion (Fee et al., 1994). Surface waters have high redox potential but low quantities of available nutrients are in the epilimnion as a result of rapid uptake by phytoplankton.
In terms of physical characteristics, fast-flowing streams differ from lakes in various ways as follows (Sigee, 2005): (a) the water body is transient (low retention time) at any particular site. It is also typically highly turbulent, with no thermal or chemical stratification. Both of these factors combine to limit the development of a planktonic community (phyto- and zooplantkton), which may be significant in larger rivers but does not normally make a major contribution to the stream community; (b) the substratum (bed) of streams is typically well aerated and exposed to light, and is the major site of algae and associated biota; (c) inflow from the catchment area is typically periodic, giving rise to marked fluctuations on water level and flow velocity (high and low flow periods). Concentrations of dissolved particulate matter, which are mainly derived from the catchment area, typically follow this periodicity in inflow. Because of this, stream ecosystems are dominated by benthic organisms. Some large rivers occupy an intermediated position between lotic and lentic environments, with limited movement of the water body, restriction of turbulence to the upper layers and sediments that are exposed to minimal water flow and are in permanent darkness (Sigee, 2005). In this situation, rivers may resemble lakes in showing chemical and thermal stratification and develop substantial phytoplankton and zooplankton.
Groundwater is the water contained in the rocks below the water table and usually is of more uniform volume than vadose water (water in the soil above the water table) (Reid & Wood, 1976). Many of the factors that influence the surface water composition also influence groundwater composition. Groundwater is always in contact with rocks and minerals and moves more slowly than surface water. Because of this, groundwater regularly contains more dissolved minerals than surface water. When water seeps below the surface, it passes through the soil where microbial respiration processes release CO2. As water encounters the CO2, the pH is lowered, and the water can dissolve more minerals. At higher temperatures, minerals dissolve more readily. Deep groundwater tends to be warmer and as a result, has higher mineral content. Ultimately, what controls the composition of groundwater is (waterencyclopedia.com): (1) the geologic materials groundwater is moving through; (2) the type of reactions taking place; and (3) the contact time, or length of time groundwater has been in contact with the rocks. The contact time may vary from a few days to more than 10,000 years. Knowledge of water–rock–organism reactions helps hydrologists unravel the origin of a specific water parcel. Carefully analyzing the water allows them to identify what types of reactions have affected the water, and to understand the geological and ecological history of the area.
Estuaries
At and near the region where the freshwater from the land meets the salt water of the sea, a distinct aquatic environment occurs – the estuary. It is defined (Dionne, 1963) as follows: an inlet of the sea reaching into a river valley as far as the upper limit of tidal rise, usually being divisible into three sectors: (a) a marine or lower estuary, in free connection with the open sea; (b) a middle estuary, subject to strong salt and freshwater mixing; and (c) an upper or fluvial estuary, characterized by fresh water but subject to daily tidal action. The estuary is an ecotone, a rather complex “buffer zone”, sharing some characteristics of both types of aquatic ecosystems, but identical to neither (Reid & Wood, 1976). It is an ephemeral feature in a long-term, geologic history and must be regarded as a dynamically evolving land-form that will go through a life cycle from valley creation (by fluvial or ice erosion), followed by the drowning phase (eustatic rise of sea level, with or without vertical crustal motion), and ending with the progressing infilling (mainly deltaic, but some offshore sedimentation, aided by eustatic drop with or without vertical crustal motion) (Fairbridge, 1961).
There are some physical, chemical, sedimentological, and biological features of the estuarine environment that are potentially important controls of the nutrients, dissolved gases, and the general biogeochemistry in estuaries. These controlling influences may be summarized as follows (Aston, 1978): (a) the tidal mixing of fresh and seawaters on a semi-diurnal or diurnal time scale, with corresponding changes in the volume of water in an estuary, produce temporal changes in the contributions of nutrients and dissolved gases from marine and fresh water sources; (b) the circulation, and especially the stratification of some estuaries, generates the possibility of vertical and horizontal variations of the concentrations of nutrients and dissolved gases within an estuary; (c) estuarine topography may give rise to particularly restricted calculations where the mixing of external seawater with the estuarine waters is greatly reduced, and the restricted mixing leads to unusual chemical environments; (d) the current regime on coastal waters and estuaries leads to the deposition of various types of sedimentary material. The deposition and resuspension of sediments in estuaries may influence the budgets of dissolved constituents in estuarine waters, including nutrients and gases; (e) chemical reactions occurring during the mixing of river water with seawater may lead to the removal or addition of the dissolved nutrients. Also, the changes in temperature and salinity during estuarine mixing influence the solubility of dissolved gases and thus influence their removal or addition in an estuary; and (f) biological production and metabolism have significant influences on the occurrence and distribution of nutrients and some gases, e.g. CO2 and O2 in estuarine waters. Estuaries are environments with special problems for biological organisms, so that there is a tendency to a decrease in species diversity in estuaries. This decrease does not, however, imply that productivity is low.
Phytoplanktons, like in marine and fresh waters, are present in estuaries too. They reside for a short period of time in estuaries usually coming from adjacent seas and rivers. Phytoplankton development in estuaries differs from that in coastal waters in that estuarine phytoplankton shows a continuous high productivity between spring and autumn, whereas coastal waters a spring peak is usually followed by a second peak in late summer (Riley, 1967; Cadee and Hegeman, 1974). Phytoplankton growth is one of the main biological processes affecting the chemistry of estuaries, since photosynthesis results in the decrease of the concentrations of CO2, SO42-, NH3, NO3-, and silicate as well as the range of micronutrients. At the same time, O2 is increasing, often to supersaturation. At nighttime, these processes are reversed.
The main features of estuaries are not its biotic aspects but the chemistry and biogeochemistry of it. However, there are biotic transports in and out of estuaries. Many species of animals move actively between the sea and its adjacent estuaries and they have been reported to occur in seals, whales, fishes, crustaceans, mollusks, polychaetes, and other organisms. There are also animals migrating between estuaries and freshwaters, such as the anadromous fish (salmon, sturgeon, sea lamprey). They spawn in fresh water and live as adults in estuaries or in the sea (Wolff, 1973).
REFERENCES:
Barnes, R.S.K., and Hughes, R.N. 1982. An introduction to marine ecology. Blackwell Scientific
Publications, London
Class handouts, may be obtained from NIGS library at reserved section (I don’t know the title)
Drever, James I. 1997. The Geochemistry of Natural Waters: Surface and Groundwater
Environments 3rd ed. Prentice Hall, New Jersey
Olausson, E., and Cato, I. (editors) 1980. Chemistry and biogeochemistry of estuaries. John Wiley & Sons
Ltd., Brisbane
Reid, G.K., and Wood, R.D. 1976. Ecology of inland waters and estuaries 2nd ed. D. Van Nostrand
Company, New York
Sigee, D.C. 2005. Freshwater Microbiology. John Wiley & Sons Ltd., England.
Swenson, H. Why is the sea salty? http://www.palomar.edu/oceanography/salty_ocean.html
The main features of estuaries are not its biotic aspects but the chemistry and biogeochemistry of it. However, there are biotic transports in and out of estuaries. Many species of animals move actively between the sea and its adjacent estuaries and they have been reported to occur in seals, whales, fishes, crustaceans, mollusks, polychaetes, and other organisms. There are also animals migrating between estuaries and freshwaters, such as the anadromous fish (salmon, sturgeon, sea lamprey). They spawn in fresh water and live as adults in estuaries or in the sea (Wolff, 1973).
REFERENCES:
Barnes, R.S.K., and Hughes, R.N. 1982. An introduction to marine ecology. Blackwell Scientific
Publications, London
Class handouts, may be obtained from NIGS library at reserved section (I don’t know the title)
Drever, James I. 1997. The Geochemistry of Natural Waters: Surface and Groundwater
Environments 3rd ed. Prentice Hall, New Jersey
Olausson, E., and Cato, I. (editors) 1980. Chemistry and biogeochemistry of estuaries. John Wiley & Sons
Ltd., Brisbane
Reid, G.K., and Wood, R.D. 1976. Ecology of inland waters and estuaries 2nd ed. D. Van Nostrand
Company, New York
Sigee, D.C. 2005. Freshwater Microbiology. John Wiley & Sons Ltd., England.
Swenson, H. Why is the sea salty? http://www.palomar.edu/oceanography/salty_ocean.html
