Aquatic Environments Overview

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Questions and Answers

What is the main characteristic of freshwater environments?

Is devoid of any vegetation

Is primarily found in oceans

Contains high levels of salinity

Includes rivers, streams, and ponds (correct)

What does a watershed encompass?

Geographic boundaries of a water body and the land that drains into it (correct)

Only surface water sources

The animals living within the water bodies

Only the water bodies it contains

Which of the following is an example of a brackish water environment?

Mekong River

Pacific Ocean

Hudson River Estuary (correct)

Lake Kenyir

Which of the following correctly describes a marine environment?

Associated with actual seas and oceans Signup and view all the answers

What is the primary factor determining the difference between seawater and freshwater?

Salinity levels Signup and view all the answers

Which ocean is the largest by surface area?

Pacific Ocean Signup and view all the answers

Which of the following is NOT a type of aquatic environment mentioned?

Volcanic water Signup and view all the answers

How much of the Earth's surface is covered by oceans and seas?

Approximately 71% Signup and view all the answers

Which component of the hydrological cycle involves the release of water vapor from plants?

Evapotranspiration Signup and view all the answers

What is the primary effect of urbanization on the hydrological cycle?

Decrease in soil evaporation Signup and view all the answers

How does deforestation impact runoff in the hydrological cycle?

Increases runoff discharge Signup and view all the answers

What human activity is most likely to lower the groundwater table?

Irrigation withdrawal Signup and view all the answers

What is a consequence of increased inland evaporation from man-made reservoirs?

Lowering water levels in lakes Signup and view all the answers

What is the standard salinity range for seawater?

32 – 37 ppt Signup and view all the answers

What is the primary reason the ocean is salty?

Decay of biological organisms Signup and view all the answers

At what temperature does pure water reach its maximum density?

4 °C Signup and view all the answers

What is the typical density range for seawater?

1.022-1.030 g/cm³ Signup and view all the answers

What is the pH level of freshwater?

7.0 Signup and view all the answers

Which component is crucial for photosynthesis in seawater?

Carbon Dioxide Signup and view all the answers

How does the boiling point of seawater compare to that of freshwater?

Seawater has a slightly higher boiling point Signup and view all the answers

What is the freezing point of seawater typically around?

-1.9 °C Signup and view all the answers

Study Notes

Aquatic Environments

Freshwater Environments: rivers, streams, ponds, lakes, reservoirs, ice (icebergs, snows), wetlands, and groundwater.
Brackish Water Environments: estuaries, mangroves, brackish seas & lakes, brackish marsh.
Marine Environments: seas and oceans.
- Oceans: Pacific, Atlantic, Indian, Southern, Arctic. Oceans cover ~71% of the Earth's surface.
- Salinity: measured as parts per thousand (ppt), (‰), [g/kg] and ratio (no unit-often written as S=37).
  - 'Normal' Salinity range: 32 – 37 ppt.
Seawater Salinity:
- Why is the sea salty?
  - Decaying biological matter
  - Weathering and erosion processes
  - Rains and streams transport minerals to the sea
  - Dissolved rocks and sediments from the ocean floor
  - Solid and gas material from hydrothermal vents
- The proportion of salt + its content in ALL the oceans remains the same!
Dissolved Gases in Seawater:
- Dissolved gases are very important in the oceans.
- Involved in biogeochemical cycling e.g.CO₂ used in photosynthesis to produce O₂, O₂ used in respiration to produce CO₂, N used in the nutrient cycle.
Density of Seawater:
- Pure water density: 1.000 g/cm³ at 4°C
- Seawater is usually more dense: 1.022-1.030 g/cm³
- Difference in Seawater densities create deep ocean currents.

Freshwater vs. Saltwater Properties:

Property	Freshwater	Seawater
Odour	Odourless	Distinctly marine
Taste	Tasteless	Salty
pH	7.0 (neutral)	8.1 (alkaline)
Density (4°C)	1.000 g/cm³	1.028 g/cm³
Freezing point	0 °C	-1.9 °C
Boiling Point	100 °C	100.6 °C

Watersheds

Geographic boundaries of a water body, its ecosystem and the land that drains to it.
Includes groundwater that receives discharges from streams, wetlands, ponds, and lakes.
Can be as small as a backyard or as large as the land that drains into the Great Lakes.

Hydrological Cycle

Continual exchange of water between the Earth and the atmosphere.
Pathways of water movement and distribution.
Components:
- Precipitation (amount, frequency, intensity, type)
- Evapotranspiration (evaporation plus transpiration from plants)
- Soil moisture
- Runoff, streamflow and river discharge into the oceans
- Atmospheric moisture flows (e.g. by wind) and divergence
- Atmospheric moisture storage
Related issues:
- Co-variability of temperature and precipitation
- Forcings of the hydrological cycle, such as solar energy.

Impacts of Human Activities on the Water Cycle

Deforestation: Run-off discharge increases.
Land Clearing: Soil evaporation is high, transpiration is low.
Urbanization: Retain run-off, inland evaporation increases, groundwater input decreases, wetland areas dry out.
Man-Made Reservoirs: Withdrawal for human usage & irrigation
- Lowering the groundwater table
- Reduction of water in streams and lakes
- Land subsidence
- Saltwater intrusion

Sustainability

Consider how daily water usage may not be sustainable.

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Description

Explore the diverse types of aquatic environments, including freshwater, brackish, and marine ecosystems. Learn about the significance of salinity, the factors contributing to seawater's saltiness, and the importance of dissolved gases in ocean environments. This quiz will enhance your understanding of the complex interactions within aquatic habitats.