TOPIC 4: Water & Aquatic Food Production Systems & Societies

4.1 Introduction to Water Systems

4.2 Access to Fresh Water

4.3 Aquatic Food Production Systems

4.4 Water Pollution

4.4 Knowledge & Understanding

• There are a variety of freshwater and marine pollution sources.
• Types of aquatic pollutants include floating debris, organic material, inorganic plant nutrients (nitrates and phosphates), toxic metals, synthetic compounds, suspended solids, hot water, oil, radioactive pollution, pathogens, light, noise and biological pollutants (invasive species).
• A wide range of parameters can be used to directly test the quality of aquatic systems, including pH, temperature, suspended solids (turbidity), metals, nitrates and phosphates.
• Biodegradation of organic material utilizes oxygen, which can lead to anoxic conditions and subsequent anaerobic decomposition which in turn leads into formation of methane, hydrogen sulfide and ammonia (toxic gases).
• Biochemical oxygen demand (BOD) is a measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity. BOD is used indirectly to measure the amount of organic matter within a sample.
• Some species can be indicative of polluted waters and can be used as indicator species.
• A biotic index indirectly measures pollution by assaying the impact on species within the community according to their tolerance, diversity, and relative abundance.
• Eutrophication can occur when lakes, estuaries and coastal waters receive inputs of nutrients (nitrates and phosphates), which results in an excess growth of plants and phytoplankton.
• Dead zones in both oceans and fresh water can occur when there is not enough oxygen to support marine life.
• Application of Figure 3 to water pollution management strategies includes:
1. Reducing human activities that produce pollutants (e.g. alternatives to current fertilizers and detergents).
2. Reducing release of pollution into the environment (e.g. treatment of wastewater to remove nitrates and phosphates).
3. Removing pollutants from the environment and restoring ecosystems (for example, removal of mud from eutrophic lakes and reintroduction of plant and fish species).

Vocabulary

• flotsam
• jetsam
• nurdles
• direct measurement
• indirect measurement
• indicator species
• macroinvertebrates
• biotic index
• BOD₅
• DO
• turbidity (TSS)
• nitrates
• phosphates
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• anaerobic
• hypoxia
• anoxia
• hydrogen sulfide
• eutrophication
• oligotrophic
• algal bloom
• buffer zone
• dead zone
• slurry
• dredge
• brackish
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Pollution

“the addition to the biosphere of a substance or an agent (such as heat) by human activity, at a rate greater than that at which it can be rendered harmless by the environment.”

– Rutherford, pg. 276

4.4.1 Sources of Marine Pollution

1.5.3 Review

Point or nonpoint?

Biodegradable or persistent?

Acute or chronic?

4.4.1 Nonpoint Sources

4.4.2 Types of Pollutants

4.4.2 Types of Pollutants

4.4.2 Marine Debris

flotsam - wreckage from a ship

jetsam - parts of the ship discarded when under duress

ghost nets - fishing nets lost at sea

Plastic (nurdles)

VIDEO NatGeo: Strange Days-Plastic Plague

Who Owns the Caspian Sea?

4.4.3 Direct Measurement

• pH - probe
• Temperature - thermometer
• Total Suspended Solids (TSS) - Secchi disk
• turbidity
• Metals - precipitate
• Nitrates (NO₃^-) - precipitate
• Phosphates (PO₄^3-) - precipitate

4.4.4 Indirect Measurement

• Biochemical Oxygen Demand (BOD)
• Dissolved oxygen (DO)
• Respiration/photosynthesis
• Aerobic/anaerobic
• Biotic index
• Indicator species
• Macroinvertebrates
• Generalize health
• Kick sampling

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What is a pellet?

4.4.4 Oxygen Demand

Aerobic decomposers need O₂

Leading to hypoxic

4.4.4 Hypoxia & Anoxia

O₂ deficiency (hypoxia)

• Absent O₂ (anoxia) conditions
• PO₄^-2 + H⁺¹ → H₂S +H₂O + chemical energy
• No fish
• Anaerobic decomposition
• fermentation
• reduction in DO
• Increased methane, ammonia, hydrogen sulfide
• Loss of biodiversity
• shorter food chains

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4.4.5 Biochemical Oxygen Demand

A measure of the amount of DO required to break down the organic material in a given volume of water through aerobic biological activity.

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BOD₅ - measures the mass (mg) of O₂ used (during respiration) by one liter of effluent in darkness for 5 days at 20 ºC

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4.4.6 Indicator Species

Species resistant (or not) to low oxygen levels

Presence of species is good, although absence isn’t always an indicator of aquatic health

4.4.7 Biotic Index - Macroinvertebrates

Aquatic macroinvertebrates have some general characteristics that make them very useful to assess stream health:

1. They are abundant & found in water bodies throughout the world.
2. They are not extremely mobile (as compared to other aquatic organisms such as fish).
3. They carry out part or all of their life cycle within the stream or river.

4.4.7 Biotic Index - Lichen

Grow in exposed places (substrates such as rocks or tree bark)

Require absorption of water and nutrients

Rainwater contains just enough nutrients to keep them alive

Air pollutants dissolved in rainwater (especially SO₂) can damage lichens and prevent growth

Natural indicators of air pollution

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4.4.8 Eutrophication

The process of nutrient enrichment of an ecosystem. Normally:

• Freshwater
• Nitrates (NO₃^-) & phosphates (PO₄^3-)
• Natural processes
• sedimentation → succession

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4.4.8 Anthropogenic Acceleration

4.4.8 Eutrophication Process

• Nutrients into the H₂O
• feed & breed organisms
• live & die, adding organic matter
• decay & recycle
• From oligotrophic...
• clear, deep, cold, nutrient poor
• few & small organisms with short food chains
• high O₂ content
• ...to eutrophic
• turbid, shallow, warm, nutrient rich
• increased productivity

Great! Right?

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4.4.8 Eutrophication - Aesthetics & Health

Ugly

• algal blooms
• duckweed
• harmful algal blooms
• Cyanobacteria
• Alexandrium & Karenia
• pseudo-nitzschia diatoms
• red tide

Smelly

• hydrogen sulfide (H₂S)
• Jellyfish Lake (Palau)
• Kai Lake (Kagoshima, Japan)
• Onandaga Lake (N.Y.)

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CASE STUDY: Onandoga Lake

• Most polluted lake in the U.S.

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• Nutrients, toxins, mercury

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• Superfund site

4.4.8 Eutrophication Impacts

Sediment becomes rich in ammonia, reduced absorption of N₂

Increased turbidity creates shallower photic zone

4.4.9 Oceanic Zones

Catchment area: the area from which rainfall flows into a body of water

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• Littoral zone
• shoreline
• diverse & abundant life
• warm & nutrient rich
• photosynthesis
• plant life
• Benthic zone
• low/no light
• cold
• decaying organic matter
• decomposers
• insect larvae
• shellfish

4.4.9 Dead Zones

4.4.9 Dead Zones

At a concentration of 2-5 ppm, fish and other marine life have trouble breathing and will swim away towards a more oxygen rich area. This movement forces them to crowd with other local species where they are also more prone to attack by different predators. Animals that live on the seafloor cannot escape the hypoxic zone as easily and begin to die at 1.5 ppm.

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-from Portland State University

4.4.9 Dead Zones

Click on the picture to zoom in

CASE STUDY: Lake Erie Dead Zone

• 12^th largest lake in world

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• 1960’s issues
• Cuyahoga River

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• Picture from 2011
• largest algal bloom in decades
• green is algae

4.4.10 Pollution Management Strategies for Nutrient Enrichment

The infamous Figure 3

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4.4.10.1 Replace Production: Reduce, Reuse, Recycle

Domestic solutions

• Buy phosphate-free detergents & shampoos
• Wash only full loads
• Dry composting toilets
• Compost organic waste
• Native plants/drought-tolerant gardens
• Education & awareness campaigns

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4.4.10.1 (5.2.9) Replace Production: Reduce, Reuse, Recycle

Agricultural solutions

• Time fertilizer use by rainfall
• Reduce fertilizer, rotate crops
• Contour ploughing/graze slopes
• Stop leaching of animal slurry/sewage
• Maintain crop cover outside growing season (autumn crops)
• Do not plough grass/incorporate straw (releases N & captures P)
• Education & awareness campaigns

4.4.10.2 Regulation of Release

Domestic solutions

• Ban or limit detergents containing phosphate
• Used in hard H₂O
• Why PO₄^3-?
• Stricter sewage treatments
• Phosphate stripping
• Separation of black and greywater for reuse

4.4.10.2 Regulation of Release

Agricultural solutions

• Plant buffer zones between fields & catchment areas
• Minimize fertilizer dosage
• Reduce animal access to waterways
• Contain/divert animal slurry & sewage

CASE STUDY: Baltic Sea

• 800% more P than 100 years ago

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• Global warming contributor

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• 80% of nutrients come from land sources

4.4.10.3 Restoration

Much harder & more expensive

• Dredge sediments from targeted rivers/lakes
• mud-pumping
• Remove biomass
• excess weeds (hyacinth)
• thatch or fuel use
• fish (2^nd consumers)
• then reintroduce later
• physically/herbicidal
• Precipitation
• Al or Fe salts to precipitate PO₄^3-
• Introduce N & P capturing plants
• Sunken barley bales

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