1. STA1033 Aquatic Science & Daily Life Lecture 1 Introduction to Aquatic Habitats & Water as an Environment

3. 1. Types of aquatic environment
Freshwater:
Rivers, streams, ponds, lakes, reservoirs, ices (icebergs, snows), wetland areas, and groundwater
E.g. Mekong River, Kenyir Lake.
lake
waterfall

4. The term watershed refers to the geographic boundaries of a particular water body, its ecosystem and the land that drains to it.  A watershed also  includes groundwater aquifers that discharge to and receive discharge  from streams, wetlands, ponds, and lakes.  Large watersheds are sometimes referred to as river basins. 
Everyone lives in a watershed.  You and everyone in your watershed are part of the watershed community.  The animals, birds, and fish are too.  You influence what happens in your watershed, good or bad, by how you treat the natural resources, the soil, water, air, plants, and animals.  What happens in your small watershed also affects the larger watershed downstream.

5. BRACKISH WATER
Estuaries, mangroves, brackish seas & lakes, brackish marsh
E.g. Thames Estuary, Southampton Water, Chesapeake Bay, Caspian Sea (world’s largest lake).
Brackish water is water that has more salinity than fresh water, but not as much as seawater:

6. Estuary:
Definition: “An inlet of the sea reaching into a river valley as far as the upper limit of the tidal rise”.
During high tide, salt wedge move upstream & retreat at low tide
Mudflats and tidal marshes exposed during low tide
High productivity of plankton & benthos
Tides mixed soluble nutrients & food particles  increase the growth of plants & animals
Important as nurseries for fishes, birds, and shellfishes, e.g. salmon, trout, crocodile.
Human impact: 22 (60%) largest cities in the world are located on estuaries, e.g. New York City (Hudson River Estuary) and London (Thames River Estuary).

7. MARINE (SEA-OCEAN)
Marine is frequently associated with seas and oceans
Cover ~71% from Earth’s surface
World Oceans:
Pacific Ocean (155 million sq km)
Atlantic Ocean (76 million sq km)
Indian Ocean (68 million sq km)
Southern Ocean (20 million sq km)
Arctic Ocean (14 million sq km)
The term "marine" is most frequently associated with seas and oceans. It may thus reflect water that contains high salt concentration like as in seas and oceans.

9. Marine-Sea:
Sea is often assigned to saltwater areas on the margins of the oceans, such as:
the Mediterranean Sea is a sea connected to the Atlantic Ocean
the South China Sea is a marginal sea that is part of the Pacific Ocean.
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by theMediterranean region and almost completely enclosed by land; The South China Sea is a marginal sea that is part of the Pacific Ocean,
Langkawi Beach
Cornwall Coast

10. What’s different about oceanic seawater?
2. Seawater Properties
What’s different about oceanic seawater?
Salty
How?
Why?

11. Surface Ocean Salinity
From Levitus Ocean Atlas

12. Saltiest Freshest High evaporation, low precipitation
E.g. Red Sea or Eastern Mediterranean
Freshest
High precipitation, low evaporation
High fresh water input
E.g. coastal waters, Gulf of Bothnia (Finland)

13. Measuring Salt Content
There are two main ways of measuring the salt content:
Salinity
Total number of grams of dissolved salt in 1kg of seawater
Chlorinity
The chloride content of seawater.
Both are proxies for the total salt content and assume that the ions present are in constant proportions.

14. Salinometer
Compares conductivity of sample to that of standard KCl solution.

15. Refractometer
Refraction of lights by seawater

16. Ocean Salinity Ranges Salinity Units
Salinity used to have units of parts per thousand, (‰), [g/kg]
As is now measured as a ratio it is not given any units!!
Often written as S= 37
Ocean Salinity Ranges
Normal ocean water
S= 32-37
Areas with higher salinity
e.g. Mediterranean: S= 37-39, Red Sea: S= 40-42
Areas with lower salinity
Close to land e.g. Gulf of Bothnia (Off Finland) S=5.

17. Ocean Why is the sea salty? Ocean Chemistry
Decaying/decayed biological matter
Weathering and erosion processes
Rains & streams transported their minerals to the sea
Dissolved from rocks & sediments below ocean’s floor
Solid & gasses material from hydrothermal vents or atmosphere
The ocean is not 'diluted' by the addition of fresh water through rain and rivers because the saltiness of the ocean is the result of several natural influences and processes, the salt load of the streams entering the ocean is just one of these factors. In addition, salts become concentrated in the sea because the sun's heat distills or vaporizes almost pure water from then surface of the sea and leaves the salts behind (this process is part of the continual exchange of water between the Earth and the atmosphere that is called the hydrologic cycle).
Ocean
Rivers
Atmosphere
Seafloor
Others
Ocean Chemistry

18. The ocean is not 'diluted' by the addition of fresh water through rain and rivers because the saltiness of the ocean is the result of several natural influences and processes, the salt load of the streams entering the ocean is just one of these factors.
Salts become concentrated in the sea because the sun's heat distills or vaporizes almost pure water from then surface of the sea and leaves the salts behind (this process is part of the continual exchange of water between the Earth and the atmosphere that is called the hydrologic cycle).

19. Principle of Constant Composition
For seawater while the total concentration of dissolved salts varies from place to place, the ratios of the more abundant components remain almost constant (Millero, 1996).

20. Dissolved gases in the oceanic seawater
Dissolved gases are very important in the oceans. They are heavily involved in biogeochemical cycling eg CO2 used in photosynthesis O2 produced, O2 used in respiration CO2 produced.

21. Dissolved gases are very important in the oceans
Dissolved gases are very important in the oceans. They are heavily involved in biogeochemical cycling e.g. CO2 used in photosynthesis O2 produced, O2 used in respiration CO2 produced.

23. pH of Seawater
Where { } represent activity or concentration, sometimes written [ ]
Seawater has a pH of ~8.0

24. Density of seawater Pure water: 1.000 g/cm3 at 4°C
SW: g/cm3 (depending on Salinity)
SW density until it freezes at -1.9°C then rapidly
Difference in SW densities create deep ocean current
Effect of temperature (T), salinity (S) & pressure (P) on density (D):
T ↑ D ↓
S ↑ D ↑
P ↑ D ↑

26. 3. Hydrological Cycle

27. Components of the hydrological cycle studied include precipitation (amount, frequency, intensity, type), evapotranspiration (evaporation plus transpiration from plants), soil moisture, runoff, streamflow and river discharge into the oceans atmospheric moisture flows and divergence, and atmospheric moisture storage.  Related issues are the co-variability of temperature and precipitation, and forcings of the hydrological cycle, such as solar radiation.   

28. Components of the hydrological cycle studied include:
 precipitation (amount, frequency, intensity, type), 
evapotranspiration (evaporation plus transpiration from plants),
soil moisture,
runoff, streamflow and river discharge into the oceans
atmospheric moisture flows and divergence,
atmospheric moisture storage.  Related issues are the co- variability of temperature and precipitation, and forcings of the hydrological cycle, such as solar radiation.   

29. 5. Human Impacts on Hydrological Cycle

30. 4. Global Water Budget Global water budget:
~ 2.5% of global water is fresh water
Of the fresh water,
~ 69% is permanent ice / snow
~ 30% is ground water
the balance is available in soil, lakes, rivers, etc.
~ 1% of the fresh water fuels life on Earth
Large variability in fresh water availability due to:
latitude and topography
weather and climate
human influences
How will the availability of fresh water change as climate changes???

31. 4. Temperature and Dissolved Oxygen in Lakes
Dissolved oxygen and temperature are two fundamental measurements of lake productivity. The amount of dissolved oxygen in the water is an important indicator of overall lake health.
The temperature of water determines how much oxygen can be held in solution. Cold water contains more oxygen than warm water. As temperature increases, dissolved oxygen decreases (see THERMAL STRATIFICATION).
Oxygen is produced during photosynthesis and consumed during respiration and decomposition. Because it requires light, photosynthesis occurs only during daylight.
Other sources of oxygen include the air and inflowing streams.

32. Putting the Squeeze on Fish
When strong thermal stratification develop in lake – pressure on fish.
How??