Topic 4 - Water and aquatic food production

Domestic sewage

The most universal pollutant, consisting mainly of organic matter from households, including carbohydrates, proteins, fats, and pathogens.

Industrial discharge

Wastewater from industries that varies in composition and may contain organic matter, toxic metals, or synthetic non-biodegradable compounds.

Agricultural run-off

Water that carries pesticides, fertilizers, and organic material from farms, especially from intensive farming practices.

Urban run-off

Polluted water resulting from rainwater accumulating pollutants from urban areas as it flows into nearby water systems.

Landfill sites

Areas where waste is disposed of, potentially leading to leachates that contaminate groundwater or surface waters.

Acid mine drainage

Pollution resulting from rainwater interacting with iron pyrite in mines, leading to acidic water that dissolves toxic metals.

Eutrophication

The enrichment of waters with nutrients leading to excessive plant growth and subsequent depletion of oxygen in the water.

Synthetic compounds

Man-made substances, often non-biodegradable, which can accumulate in the environment and have harmful biological effects.

Bioaccumulation

The buildup of substances, such as toxic metals, within organisms over time.

Biochemical oxygen demand (BOD)

A measure of the amount of dissolved oxygen used by microorganisms in breaking down organic material in water.

Biotic index

A method used to assess water quality based on the diversity of living organisms in the water.

Pathogens

Microorganisms such as bacteria and viruses, often found in sewage effluent, which can pose health risks if water is consumed.

Suspended solids

Small particles in water that reduce light penetration and can smother aquatic organisms, affecting photosynthesis.

Toxic metals

Heavy metals that, at high concentrations, can be harmful to aquatic life and may accumulate through the food chain.

Organic pollution

Pollution resulting from organic materials like sewage and agricultural waste, which can deplete oxygen levels in water.

Outfall pipes

Pipes used to discharge material, such as sewage or wastewater, directly into the sea or water bodies.

Hot water discharge

Release of heated water from power stations that can elevate local water temperatures, impacting aquatic ecosystems.

Invasive species

Non-native species introduced to new environments, often disrupting local ecosystems and causing ecological harm.

Indicator species

Species used to assess the health of an aquatic environment based on their sensitivity to pollution levels.

Leachates

Liquid that has percolated through waste and leached out various substances, potentially contaminating groundwater.

Accidental discharges

Unintentional release of pollutants, such as oil or hazardous materials, into water systems.

what percentage of earth is covered by water

70%

what percentage of earths water salt water and fresh water

97% salt water, 3% fresh water

where is freshwater stored (+how much percent)

• 0.3% in lakes and rivers

• 2.7% ice caps, ground water, lakes, soil water, atmospheric water, biota

hydrological cycle

process whereby water is constantly recycled between sea, air and land

storages in the water cycle

• snow and ice

• groundwater

• lakes and rivers

• oceans

• atmosphere

  • gas = water vapour

  • liquid = water droplets

• soil

flows in the water cycle

• precipitation

• melting

• interception

• Infiltration

• surface run offs

• groundwater flow

• percolation

• evapotranspiration

• evaporation

• condensation

• discharge

Interception

process of interrupting the flow of water into streams

Infiltration

physical process of moving water into soil (accumulates minerals and nutrients)

percolation

movement of water through the soil (through gravity and capillary forces)

evapotranspiration

processes by which water moves from the land surface to the atmosphere via evaporation and transpiration

transpiration

the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers

discharge

the volumetric amount of water carried by a body of water

ocean currents play an important role in…

global energy distribution

how are surface currents moved?

wind

how are deep water currents moved?

oceanic conveyor belt

upwellings

• warm water can hold less salt than cold water

• therefore warm water rises

downwellings

• cold water rises to replace the rising warm water

• warm water replaces cold water

El nino

above-average sea surface temperatures that periodically develop across the east-central equatorial Pacific

La nina

periodic cooling of sea-surface temperatures across the east-central equatorial Pacific

why do el nino and la nina occur?

• result from interactions between the ocean surface and the atmosphere over the tropical Pacific

• changes in the ocean surface temperatures affect tropical rainfall patterns and atmospheric winds over the Pacific ocean

• which impacts the ocean temperatures and currents

how often do el nina and el nino occur?

every 3-5 years

water stress

when demand exceeds the available supply over a certain time period or when the quality of water restricts its use

parameters of water stress

when supply is less than 1700 cubic meters/person/year (m³/person/year)

water scarcity

water supplies fall below 1000 m³/person/year

water scarcity issues

• Growing population increases need for water and food

• Climate change affecting precipitation rates and changing monsoons

• Agricultural practices can produce high evaporation rates

• Low water levels in many surface water sources

• Aquifers being exhausted due to over pumping

water scarcity large scale solutions

• Build dams

• Desalination

• Rainwater harvesting

• Artificially recharged aquifers

water scarcity small scale solutions

• More efficient domestic use (low flow applications and faucets)

• Grey water recycling

• Rainwater harvesting

• Drought resistant crops

• Drip irrigation

water degredation issues

• Contamination of aquifers with arsenic, salt and other substances

• Salinization of top solid due to high evaporation rates

• Use of fertilizers and pesticides

• Industrial release of pollutants

Water Degradation Solutions

• Using organic farming methods

• Use highly selective pesticides

• Industry must remove pollutants from wastewater

• Regulate the temperature of water being released from cooling towers

Main goal of a dam and reservoir system

• Capture and store runoff

• Release runoff as needed to control

• Flood control

• Fisheries

• Hydropower

• Supply irrigation water

• Recreational, aesthetic and scenic value

• Navigation

What drives the hydrological cycle

solar radiation

How does deforestation impact the hydrological cycle?

• Reduces interception, allowing rainfall to directly impact the soil, increasing erosion

• Speeds up surface run-off, reducing infiltration and percolation

• Decreases transpiration, reducing local air moisture and rainfall, potentially causing drier climates

• increasing evaporation

How does urbanisation affect the hydrological cycle?

• Replaces permeable surfaces with impervious materials, preventing infiltration and increasing surface run-off

• Channels water into drainage systems, leading to higher river flow and flood risks

• Polluted run-off from streets and roofs degrades water quality and aquatic ecosystems

How does agriculture affect the hydrological cycle?

• Excessive irrigation uses up water and makes soil salty due to evaporation.

• Farm run-off carries fertilizers and pesticides into water, causing eutrophication

• Livestock waste adds nutrients and organic matter to water, lowering oxygen levels and harming aquatic life

what is the relationship between the hydrological cycle and ecosystem

Precipitation patterns determine ecosystem distribution and agricultural potential

water security

The ability to ensure sustainable access to adequate quantities of safe, clean water for people, ecosystems, and agriculture

what are the 2 types of water scarcity

• physical scarcity

• economic scarcity

what factors impact water security?

• Population growth

• climate change

• pollution

• overuse

• infrastructure

• political/economic factors

what is a water footprint

• blue water (surface and groundwater)

• green water (rainwater for crops)

• grey water (water to dilute pollutants)

what causes water stress?

• Rapid urbanization

• industrialization

• overextraction of groundwater

• pollution

what are domestic water conservation techniques?

• fixing leaks

• using greywater for irrigation

• rainwater harvesting

What are some industrial water conservation techniques?

• recycling water

• adopting water-efficient technologies

• implementing zero-liquid discharge systems

What role do phytoplankton play in aquatic ecosystems?

form the foundation of aquatic food webs by converting sunlight and nutrients into organic matter

What are the areas of highest aquatic productivity?

• coastlines

• shallow seas

• upwellings

aquaculture

The farming of aquatic organisms to meet increasing demand for seafood

pros of aquaculture

• increased food supply

• economic benefit (job opportunities)

• efficient use of resources (max sustainable yield, less water and land than lifestok farming

• reduces overfishing of wild species

cons of aquaculture

• loss of habitat

• pollution

• spread of diseases

• introduction of non-native species, that competes with wild species

fishing methods

• trawler fishing

• purse-seine net

• long-lining

• drift net

Trawler fishing

fishing vessel drags a trawl through water behind one or more trawlers

trawler fishing evaluated (selectivity, sea bed damage, yield)

• selectivity = medium

• sea bed damage = high

• yield = high

purse-seine net evaluated (selectivity, sea bed damage, yield)

• selectivity = low

• sea bed damage = none

• yield = high

long-lining evaluated (selectivity, sea bed damage, yield)

• selectivity = high

• sea bed damage = none

• yield = medium

long-lining evaluated (selectivity, sea bed damage, yield)

• selectivity = high

• sea bed damage = none

• yield = low

what is water pollution?

water pollution occurs when harmful substances contaminate water, degrading the quality of the water

types of water pollution

• inland and coastal pollution

• marine based

inland and coast polution

• domestic sewage

• industrial discharge

• agricultural run off

• urban run off

• land development

• landfill sites

• accidental discharges

• acid mine drainage

• atmospheric input

marine based

• materials dumped at sea

• shipping activities

• exploitation of resources

effects of water pollution

• organic pollution

• inorganic plant nutrients

• eutrophication

• toxic metals

• synthetic compounds

• inert suspended solids

• thermal pollution

• oil

• pathogens

• plastic debris

• light pollution

• noise pollution

• invasive species

assessing water quality (physical and chemical parameters)

• Ph

• temperature

• suspended solids

• total dissolved solids and conductivity

• dissolved oxygen (DO2)

• Biochemical oxygen demand (BOD)

• Nutrients

• Metals

assessing water quality (biological parameters)

• kick sampling of macro-invertebrates

• biotic index

• microbial test

measuring suspended solids

• filtering known volume of water sample using pre-weighed filter paper

• drying out the filter paper and collected residue

• weighing the dried filter paper and residue

• calculate the weigh of the dried residue (final weigh of filter paper - initial weight of the filter paper) in mg/l

total dissolved solids (TDS) what does it measure?

indicates the amount of salts present, geology and type of effluent

total dissolved solids (TDS) how is it measured?

measured indirectly using conductivity meter

increasing levels of TDS …

higher conductivity readings

turbidity meter what does it measure?

amount of light scattered by particles in the water

secchi disk what does it measure?

water transparency

the greater the amount of suspended solids …

the lower the light transparency of the water

Dissolved Oxygen (DO2) how is it measured?

• filling bottle with water sample

• add reagents to sample to fix oxygen by converting it to acid

• titrating the sample in which reagent is gradually added to neutralize the acid

• amount of reagent used to neutralize the acid is used to calculate the amount of dissolved oxygen levels

biochemical oxygen demand (BOD) what does it measure?

the amount of dissolved oxygen used to breakdown the organic material in a given volume of water through aerobic activity

biochemical oxygen demand (BOD) how is it measured?

• initial dissolved oxygen reading of the sample is taken in mg/l

• one litre bottle is filled with the sample and sealed

• bottle is incubated in the dark at 20C for 5 days

• dissolved oxygen levels are measured again

• difference between the initial and final oxygen readings is BOD5

BOD5 < 2 mg/l

unspoilt water

BOD5 = 20mg/l

badly polluted water

nutrients test what does it measure

measures amount of nutrients such as nitrates, phosphates and silica

nutrients test how is it measured

• measured using chemical analysis methods

• on-site testing kits differ but rely on nutrients reacting with reagents to produce a color change

limitations to testing for physical and chemical parameters

• provides information for that specific sample at that particular time

• does not indicate whether the water is safe for drinking

why is examination of only physical and chemical parameters not sufficient to determine if the water is safe to use

• pathogens may be present in the water

• pollutants may be washed away even though they may have severely damaged ecosystem

why are macro-invertebrates used for biological monotoring

• stationary, representative of the environment they are found in

• relatively long life history providing summary of conditions over time

• abundant

• relatively easy to sample

• consists of diverse groups of organisms

biological monitoring what is it?

using biological organisms to indicate whether water quality decline and whether there have been episodes of pollution between samples

kick sampling

bottom of stream is agitated by kicking the riverbed, organisms are swept into net for analysis