instructor lecture 1 2

7/31/2019 Instructor Lecture 1 2

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Lecture 1: Introduction to

Aquatic Environments


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Aquatic Environments

Aquatic environments

Oceans

Coastlines/Estuaries

Streams Lakes

Wetlands: bogs and fens


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Freshwater Ecosystems

Only 3% of the worlds water is fresh, and

99% of this is either frozen in glaciers and

pack ice or is buried in aquifers. The

remainder is found in lakes, ponds, rivers

and streams.


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Limnology: The study of freshwater

ecosystems, with anemphasis on

understanding thephysical, chemical andbiological processes thatare important instructuring andmaintaining freshwatersystems.


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Science of Limnology

embraces: Lakes (Lentic waters)

Rivers (Lotic waters)

EstuariesOther microhabitats such as springs and

streams


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Geology

By what processes arelakes and rivers formed?


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Geology

Physics

What are theimportantphysical properties of

water and watermovement?


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Geology

Physics Chemistry

How do thechemical propertiesof water and the

nutrients it containsaffect whichorganisms can livethere?


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Chemistry

Physics Geology

Biology

How do organismsinteract with each otherand their aquatic

environment?


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Geology

Origin of Lake Basins


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Physics

Physics and ionic content of water

Light and Heat in Lakes

Distribution of heat in Lakes

Water movement in Lakes


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Chemistry

Oxygen, carbon, alkalinity and pH

Nutrient Dynamics (P, N, Si)


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Biology

OrganismsPhytoplanktonZooplanktonAquatic Insects

Fish

Case StudiesAcid DepositionPaleolimnologyExotic Species

Cultural EutrophicationKiller Lakes

ConceptsPopulation dynamicsCompetitionPredationDiseaseLife-histories


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Freshwater is a major limiting resource

Why study limnology?

Lakes and ponds are great laboratories to studyecological and evolutionary processes

Water in the Biosphere: Volume (thousands of km3) % of totalOceans 1,370,000 97.61Polar ice, glaciers 29,000 2.08Ground Water 4067 0.295Freshwater lakes 126 0.009Saline lakes 104 0.008

Soil and subsoil moisture 67 0.005Atmospheric water vapor 14 0.0009Rivers 1.2 0.00009


15/137http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/aster_colorado_delta_lrg.jpg


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UN Report(2002)

suggeststhat by2025, two-thirds of

the worldspopulationmay facewater

shortages


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Brief History of Limnology

1600sLakes in Germany and the Netherlands are categorized

based on the presence/absence of stream inflows

van Leeuwenhoek describes algae and rotifers from aDutch lake

1700sH.B. de Saussure determines that deep waters in some

Swiss lakes are much colder than surface waters

Early studies of lakes flourished in the glaciated regions of Europe and North America

1800


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1800s

L. Agassiz uses a tin cup to measure turbidity in Lake Superior

Acid Rain is linked to coal burning in England (1852)

Development of the Secchi disk

1900s

First textbook of Limnology published (1901)

Linking of sewage inputs to algal blooms (1910)

First whole-lake manipulationwithout control lake (1938)


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What Now??

Shift from observation to experimentation Species interactions and food web dynamics

Ecosystem ecology

Acid rainCultural eutrophication

Exotic Species

Paleolimnology

Genomics


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Francois Alphonse Forel

1841-1912, Swiss

Defined limnology as oceanographyof lakes

1st textbook of Limnology published in 1901 Handbuchder Seenkunde. Allegemeine Limnologie, based on 30years of research on Lac Lman (Lake Geneva).


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Stephen Alfred Forbes

1844 - 1930, American

Chief of the Illinois Natural History Survey

Published Lake as a Microcosm in 1887

concept of a lake as a superorganism

www.inhs.uiuc.edu/cae/ ltrm/station.html


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August Thienemann

1882-1960, German

With C.L. Naumann started the International

Association for Theoretical and appliedLimnology (SIL) in 1922

Influential ideas on nutrient cycling and foodweb structure

http://www.limnology.org/news/25/thienemann.jpg


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Edward A. Birge and Chancey Juday

1851-1950 (Birge), 1871-1944 (Juday)

Founded Wisconsin School ofLimnology

Comparative limnological surveys ofhundreds of lakes

Major weaknesses of Birge & Juday andcontemporarieslack of a clearlyarticulated hypothesis, few statistics,lack of replication and controls

State Historical Society of Wisconsin

http://www.library.wisc.edu/etext/WIReader/Images/WER0032.html


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G. EvelynHutchinson

1903-1991, professor at Yale.

Never earned a PhD.

Published four volume Treatise of

Limnology(1957-1993)

Responsible for the introduction

of numerous ecological andlimnological concepts


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S f


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American Society of

Limnology and

Oceanographyhttp://aslo.org/

International

Association ofTheoretical andApplied Limnology

http://www.limnology.org/


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Lakes vs. Reservoirs

Lakes Natural Reservoirs Man made


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Streams

Open systems, constant input of water andnutrients

Precipitation flows into streams via 2 routes: Overland flow through surface runoff

Infiltrating soil surface, then flowingunderground and into streams as

groundwater


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Stream Classification

Based on flow

Permanent: constant above-ground flow

year-round

Intermittent/Ephemeral: flow aboveground

for parts of the year, not all (temporal)

Interrupted: flow aboveground for parts of

the stream, not all (spatial)


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Stream Classification

Based on order

1st: no streams

flowing into it

2nd: two 1st-order

streams joining

3rd: two 2nd-order

streams joining


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Physical features

Channel shape and pattern Changes with age

Pools and riffles

Velocities, microclimate differ

Rivers age

Young: little meanders, small floodplain,

fast velocity, V cross-sectional profile

Mature: many meanders, slower velocity,

oxbows form, U profile


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Watershed - the area that a stream drains,

a.k.a, drainage basin, or catchment area


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River Continuum Hypothesis

Predictable structure of river (physical

features, dominant organisms) from

upstream headwaters to downstream

high-order stream


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Headwaters/upstream:

Riffles/rapids predominant

Heavily shaded by riparian vegetation

Energy importedallochthonous material

High diversity of benthic fauna

Downstream

Pools of slow water dominant

Only banks shaded by riparian vegetation

Autochthonous input


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Lakes

May be created by a variety of geologic and

climatic events:

Movement of tectonic plates

Volcanic eruptions

Landslides

Fluvial processes

Glaciation


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Lake Zonation


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Lake Zonation

Littoral zone: shallow (


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Vegetation Zonation

Shrub &Trees

Mixe

dherbaceous

Grassstage

Shallow

emerg.

Deepwater

emergents

Floa

tingplants

Submerged

plan

ts

Open waterphytoplankton


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Lake Stratification

Different zones or layers due to water

temperature and water density Epilimnion: layer closest to surface of water; warmed

by the sun, least dense

Metalimnion: middle layer with thermocline;

transitional layer

Hypolimnion: deepest layer, generally coldest;

sunlight does not penetrate


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Lake Stratification


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Seasonal Changes

Summer:

Warm temperatures,

long days

Obvious vertical

stratification

Epilimnion saturated

with oxygen Hypolimnion anoxic


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Fall:

Air temperatures cool, surface water cools

fastest and sinks to the bottom

Complete lake turnover

Lake no longer stratified

Lake eventually becomes a uniform 4C


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Winter:

Surface water cooler

than rest of lake

water

Ice prevents mixing

Winter stratification,0C at surface, 4C

at bottom


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Spring:

Ice melts, water surface hits 4C and

again begins to sink

Spring turnover, process repeats itself


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Roach Lake in March


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Roach Lake in August


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Nutrients

Temperature not the only stratified element

of a lake

Oxygen: highest concentration near surface

(photosynthesis)

Nitrogen: NO3- at surface, NH4

+ at benthos

Sulfur: SO4-2 at surface, H2S at benthos

Iron: Fe+3 at surface, Fe+2 at benthos


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Marsh (Eutrophic)

Bog (Dystrophic)

Oligotrophic

Lake

Mesotrophic to Eutrophic Lake

Terrestrial

Sphagnum


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Crampton Lake (oligotrophic)

Bro n Lake


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Brown Lake

(mesotrophic - eutrophic)


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Northgate Bog (dystrophic)


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Ziesnis Bog (dystrophic)


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Wetlands: technical definition

Vegetation presence of hydrophytic (water-loving, flood-

tolerant) plants

Soils presence of hydric (flooded, reduced) soils

Hydrology water table at or near the surface for part of the

growing season


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Wetland history

Historically, wetlands have been drained to: Provide land for agricultural purposes

Reduce the incidence of mosquito-bornediseases, like malaria, yellow fever

Wetlands now recognized as havingcommercial, aesthetic, and ecologicalvalue


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Why are wetlands important?

Storm and floodwater

storage

Improved water quality:

filtration Rare or endangered

plants and animals

Waterfowl nursery

grounds

Migration stop-overs


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Wetland examples

Marshes

Swamps

Glades

Bogs

Fens


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Bogs

Acidic (pH < 4.1)

Nutrient-poor soils

Ombrotrophic:

precipitation-fed system

Dominant vegetation:Sphagnummoss,Vaccinium(cranberriesand blueberries), and

other low-lying species

Slightly less acidic (pH4.1-6.0)

Soil more nutrient-rich

Minerotrophic:

groundwater-fed system

Dominant vegetation:

sedges, rushes, and

grasses

Fens


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Black spruceSwamp alder

Tamarack Leatherleaf


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Cotton grassPitcher plant

Sphagnummoss

Cattail

Sundew


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Long Lake

Peter Lake

Paul Lake

Nutrients added/No Piscivores

Nutrients added/Piscivores

No Piscivores

Piscivores


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Physical Aspects

Light, heat, waves, and currents can

produce physically distinct zones that can

vary by day and season.


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Chemical Structure

Greatest cause of altered water chemistryin natural waters is now pollution fromhuman waste, agriculture and industry.

Without proper control, the increasedchemical loading can lead toeutrophication of lakes and reservoirs.


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Chemical Structure

Chemical composition of natural aquatic

ecosystems are dependent on rainfall,

erosion, evaporation and sedimentation.

Water contains a vast array of inorganicand organic compounds which are present

as dissolved solids and gases.


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Biological Structure

Viruses role usually associated with

public health problems (i.e.: hepatitis can

be transmitted by ingestion of natural

waters contaminated with the feces ofinfected people


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Bacteria unicellular organisms

responsible for recycling of organic and

inorganic materials.


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Fungi participate in the decomposition

and recycling of vegetable and animal

matter.

Phytoplankton - algae may be unicellular,colonial or filamentous in form

(Pediastrum)


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Macrophytes aquatic plants may

dominate shallow lakes and streams.

Zooplankton components are

protozoans, rotifers and crustaceans.


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Zoobenthos bottom feeders; includes

insect larvae, crustaceans and mollusks.

Fish

9-1

O H bit t


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There are two major marine provinces: thebenthic (bottom) and the pelagic (water

column).

The benthic environment is divided by depth intothe: Intertidal zone, Sublittoral zone, Bathyal

zone, Abyssal zone, and the Hadal zone

The pelagic environment is divided into the

Neritic Zone and the Oceanic Zone

Ocean Habitats


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The five major kingdoms in the ocean are:9-2


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The five major kingdoms in the ocean are:

Monera, Protista, Fungi, Metaphyta and

Metazoa. Monera are the bacteria and blue-green algae.

Protista are single-celled organisms with a

nucleus. Fungi are abundant in the intertidal zone and are

important in decomposition.

Metaphyta are the plants that grow attached tothe sea floor.

Metazoa include all multicellular animals in the

ocean.

Marine organisms can also


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be classified by lifestyle.

Plankton are the organisms which float in the water andhave no ability to propel themselves against a current.

They can be divided into phytoplankton (plants) and

zooplankton (animals).

Nekton are active swimmers and include marine fish,

reptiles, mammals, birds and others.

Benthos are the organisms which live on the bottom

(epifauna) or within the bottom sediments (infauna).

Some organisms cross from one lifestyle to another

during their life, being pelagic early in life and benthoniclater.

E i t l f t i9-4


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Environmental factors in

the marine environment include:

Temperature

Salinity

Pressure

Nutrients Dissolved gases

Currents

Light

Suspended sediments

Substrate (bottom material) River inflow

Tides and waves


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Ecosystem is the total environment including

the biota (all living organisms) and non-living

physical and chemical aspects. Temperature can control distribution, degree of

activity and reproduction of an organism.

Salinity can control the distribution of organisms

and force them to migrate in response tochanges in salinity.

Hydrostatic pressure is the pressures exerted

by a column of water surrounding an organism.

More than 90% of marine plants are algae


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More than 90% of marine plants are algae

and most are unicellular and microscopic.

To photosynthesize (produce organic material

from inorganic matter and sunlight) plants must

remain within the photic zone. Diatoms are single cells enclosed in a siliceous

frustrule (shell) that is shaped as a pillbox.

Dinoflagellates are single cells with two whip-like

tails (flagella).

Zooplankton include the


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Zooplankton include the

copepods and foraminifera.

Copepods are small herbivores (plant-

eating organisms) that filter diatoms fromthe water.

Foraminifera are single-celled,

microscopic organisms which build shells

of calcium carbonate.


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Marine Ecosystems

Ecosystems (or ecological systems) are systems ofcommunities in a large geographical area.

In order for an ecosystem to be successful, fourthings are required:

An energy source

Organisms capable of capturing this energy in the

form of organic molecules

.Organic material must be available to all other

organisms

Cycling of nutrients must occur between the abiotic

and biotic portions of the system

A ti E l A li ti


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Aquatic Ecology Application

Compliance with water quality standardsand permits

Fish population and bioaccumulation

studies

A ti E l A li ti


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Aquatic Ecology Application

Biomonitoring studies for toxicity ofeffluent


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Lecture 2: Major Ions and Nutrients

Water chemistry:


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y

Gases, major ions & nutrients

Gases

Oxygen (O2)

Carbon dioxide (CO2)

Nitrogen (N2)

Hydrogen sulfide (H2S)

Major ions (anions and cations)

Nutrients (phosphorus and nitrogen)

W t h i t


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Water chemistry: gases

What are the ecologically most importantgases ?

O2

CO2

N2

H2S

Gas sol bilit


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Gas solubility

The maximum amount of gas that can be dissolved inwater (100% saturation) is determined by temperature,

dissolved ion concentration, and elevation

solubility decreases with temperature

warm beer goes flat

solubility decreases with higher dissolved ion content

(TDS, salinity)

DO saturation is lower in saltwater than freshwater

(for the same temperature, solids drive out gases)

Water chemistry: O


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Water chemistry: O2

~ 21% of air

Very soluble (DO)

Highly reactive and concentration is dynamic

Involved in metabolic energy transfers

Major regulator of metabolism (oxic-anoxic)

Aerobes (fish) vs anaerobes (no-fish, no zoops)

Types of fish

Salmonids = high DO (also coldwater because ofDO)

Sunfish, carp, catfish = low DO (also warmwater)

Major sources of O2


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j 2 Sources

Photosynthesis (phytoplankton, periphyton,macrophytes)

Air from wind mixing

Inflows tributaries may have higher or lower DO

groundwater may have higher or lower DO

Diffusion (epilimnion to hypolimnion and viceversa)

Major sinks of O


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Major sinks of O2

Sinks Respiration

bacteria, plants, animals; water and sediments

Diffusion to sediment respiration Outflow (tributary or groundwater)

Gases: N


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Gases: N2

~ 78% of air Concentrations in water usually saturated because it is

nearly inert

Supersaturation (>100 %) can occur in reservoirtailwaters from high turbulence

May be toxic to fish (they get the bends) N2 -fixing bacteria and cyanobacteria (blue-green

algae) convert it to bio-available NH4+

Denitrifying heterotrophic bacteria convert NO3- to N2

and/orN2O under anoxic conditions

Gases: CO2


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2

Only about 0.035% of air (~ 350 ppm)

Concentration in H2O higher than expected based onlow atmospheric partial pressure because of its high

solubilityGas

(at 10oC)

Concentration @

1 atm (mg/L)

Concentration @

normal pressure (mg/L)

N2 23.3 18.2

O2 55.0 11.3

CO2 2319 0.81

How long does your soda pop fizz after shaking it?

CO reactions in water


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CO2 reactions in water


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Inorganic - C equilibria

Note 100% CO2 for pH< ~ 4.5; 100% bicarbonate for pH ~ 8

and 100% carbonate for pH > ~12

H2CO3 HCO3- CO3-2

pH

Inorganic - C: Major sources andsinks


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sinksSources:

Atmospheric CO2

Respiration and other aerobic and anaerobic

decomposition pathways in the water and sediments

Groundwater from soil decomposition products

Groundwater from volcanic seeps

Sinks:

pH dependent conversions to bicarbonate and carbonate

Precipitation of CaCO3 and MgCO3 at high pH

Photosynthesis


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Soda pop chemistry


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www.saddleback.cc.ca.us/faculty/thuntley/ms20/seawaterprops2/sld013.htm

Soda pop chemistry

CO2 and the inorganic carbon


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2

system

Carbon dioxide diffuses from the atmosphereinto water bodies and can then be incorporated

into plant and animal tissue

It is also recycled within the water with some

being tied up in sediments and some ultimately

diffusing back into the atmosphere

Fixed carbon also enter the water as

allocthonous particulate and dissolved material

CO2 and the inorganic carbon


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2

system - 2

Alkalinity, acid neutralizing capacity(ANC), acidity, carbon dioxide (CO2), pH,

total inorganic carbon, and hardness are

all related and are part of the inorganiccarbon complex

CO2 chemistry: Alkalinity


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2

Alkalinity the ability of water to neutralize acid; a measure of buffering

capacity or acid neutralizing capacity (ANC)

Total Alkalinity (AlkT) = [HCO3-] + 2[CO3

2-] +[OH-] - [H+]

Typically measured by titration with a strong acid. The units are in mg

CaCO3/L for reasons relevant to drinking water treatment

Can be used to estimate the DIC (dissolved inorganic carbon)

concentration if the [OH-]

Conversely, direct measurements of DIC by infrared analysis or gas

chromatography, together with pH and the carbon fractionation

schematic can be used to estimate alkalinity

Alkalinity and water treatment


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Advanced wastewater treatment (domestic sewage) Phosphorus nutrient removal by adding lime (Ca(OH) 2) or

calcium carbonate (CaCO3)

As pH increases >9, precipitates adsorbed PO4-3

Settle and filter the effluent to obtain 90-95% removal

Used for particle (TSS) removal also

Drinking water treatment

For TSS removal prior to disinfection

Acid-rain mitigation to whole lakes Lime or limestone added as powdered slurry to increase

impacted lake pH

Also broadcast aerially to alkalize entire watersheds

CO2 chemistry: Hardness


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Hardness - the total concentration of multi-valent (i.e. >2) cations

Ca+2 + Mg+2 + Fe +3 (when oxic) + Mn+4 (when oxic); all other multivalent

cations are typically considered to be negligible

Sources-

Minerals such as limestone (Ca and Mg) and gypsum (Ca)

Water softeners and other water treatment processes such asreverse osmosis and ion exchange

Evaporation can increase hardness concentration

Drinking water effects (no real health effects)

Soap scums and water spots on glasses and tableware

Deposits (scaling) can cause clogging problems in pipes, boilersand cooling towers

Water chemistry Major ions


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Water chemistry Major ionsIon balance for typical fresh water

Anions Percent Cations Percent

HCO32- 74 Ca2+ 63

SO42- 16 Mg2+ 17

C1- 10 Na+ 15

K+ 4SiO2 < 1

Note: plant nutrients such as nitrate, ammonium and phosphate that cancause algae and weed overgrowth usually occur at 10s or 100s of parts-

per-billion and along with other essential micronutrients usually represent


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Nutrients phosphorus


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Essential for plant growth Usually the most limitingnutrient in lakes

Derives from phosphatic rock abiotic, unlike nitrogen

No gas phase, but can come from atmosphere as

fugitive dust

Adsorbs to soils

Naturally immobile unless soil is eroded or excess

fertilizer is applied

Phosphorus moves with sediments



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Not toxic

Algae have physical adaptations to acquire

phosphorus

High affinity (low k) Alkaline phosphatase activity

Storage

Luxury uptake Single redox state

Phosphorus cycle is closely linked to the iron

(Fe) cycle

Phosphorus basic properties


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Phosphorus basic properties

No redox or respiration reactions directlyinvolved (organisms are not generating energyfrom P chemistry)

PO43 highly adsorptive to cationic sites (Al+3,

Fe+3

, Ca+2

) Concentration strongly affected by iron redoxreactions

Ferric (+3) insoluble floc, adsorb PO43

Ferrous (+2) soluble so PO43

becomessoluble, too, unless Fe2+ reacts with sulfide,causing FeS to precipitate

Phosphorus levels in the


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environment

Major factors affecting phosphorus levels,cycling, and impacts on water quality

include:

Soil properties Land use and disturbance

Transport associated with runoff

Where does phosphorus come

f ?


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from?

Phosphorus external sources


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Phosphorus external sources

Nonpoint sources Watershed discharge from tributaries

Atmospheric deposition

Point sources Wastewater

Industrial discharges

Phosphorus nonpoint sources


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Phosphorus nonpoint sources

Watershed discharges from tributaries Strongly tied to erosion (land use

management)

Stormwater runoff (urban and rural)

Agricultural and feedlot runoff

Atmospheric deposition

Often an issue in more pristine areas

Arises from dust, soil particles, waterfowl On-site domestic sewage

Phosphorus point sources


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Phosphorus point sources

Wastewater Municipal treated wastewater

Combined sewer overflows (CSOs)

Sanitary sewer overflows (SSOs)

Industrial discharges

Phosphorus internal sources


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Phosphorus internal sources

Mixing from anoxic bottom waters with high phosphatelevels is closely tied to iron redox reactions

O2 > 1 mg/L Insoluble ferric (+3) salts form that

precipitate and settle out, adsorbing PO4-3

O2 < 1 mg/L (anoxic) ferric ion reduced to solubleferrous ion (Fe+2) allowing sediment phosphate to

diffuse up into the water

Wind mixing (storms and fall de-stratification) can re-

inject high P water to the surface, causing algal blooms

Phosphorus Lake budget


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Phosphorus Lake budget

Nutrients phosphorus cycle


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Nutrients phosphorus cycle

Major pools andsources of P inlakes Natural inputs are

mostly associated with

particles P as ortho-p, Pi, soluble

reactive P

Wastewater is mostlydissolved phosphate

P is rapidly removedfrom solution by algal-bacterial uptake or byadsorption to sediments

Phosphorus cycling major


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sources Sewage

Dissolved

Tributaries and

deposition

Particulate

Erosion

Particulate

Sediments

Particulate and

dissolved

Phosphorus cycling internal

li


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recycling

Rapid PO4-3recycling

Bacterial uptake

Algal uptake

Adsorption to

particles

Detritus

mineralization

Zooplankton

excretion

Fish excretion

Phosphorus cycle major

t f ti


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transformations

Modified from Horne and

Goldman, 1994.

Limnology. McGraw Hill.

The whole

phosphoruscycle

Nitrogen basic properties


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Nitrogen basic properties

Nitrogen is relatively scarce in somewatersheds and therefore can be a limiting

nutrient in aquatic systems

Essential nutrient (e.g., amino acids,nucleic acids, proteins, chlorophyll)

Differences from phosphorus

Not geological in origin Unlike phosphorus, there are many oxidation

states


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Nitrogen general properties


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t oge ge e a p ope t es

Essential for plant growthNot typically limiting but can be in:

Highly enriched lakes

Pristine, unproductive lakes located inwatersheds with nitrogen-poor soils

Estuaries, open ocean

Lots of input from the atmosphere Combustion of NO2, fertilizer dust

Nitrogen general properties


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g g p p

Mobile in the form of nitrate (soluble), itgoes wherever water flows

Ammonium (NH4+) adsorbs to soil particles

Blue green algae can fix nitrogen (N2) fromthe atmosphere

Nitrogen has many redox states and is

involved in many bacterial transformations

Nitrogen sources


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g

Atmospheric deposition Wet and dry deposition (NO3

- and NH4+)

Combustion gases (power plants, vehicle

exhaust, acid rain), dust, fertilizers Streams and groundwater (mostly NO3

-)

Sewage and feedlots (NO3- and NH4

+)

Agricultural runoff (NO3- and NH4+)Regeneration from aquatic sediments and

the hypoliminion (NH4+)

Nitrogen - toxicity


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g y

Methemoglobinemiablue baby syndrome > 10 mg/L NO3

--N or > 1 mg/L NO2--N in well water

Usually related to agricultural contamination of

groundwater

NO3- possible cause of stomach/colon cancer

Un-ionized NH4+ can be toxic to coldwater fish

NH4OH and NH3 at high pH

N2O and NOx contribute to smog, haze, ozone layer

depletion, acid rain

Nitrogen many oxidation

t t


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states

Unlike P there are many oxidation statesOrganisms have evolved to make use of

these oxidation-reduction states for energy

metabolism and biosynthesis

-3 0 + 1 + 3 + 4 + 5

NH4+ N2 N2O NO2- NO2 NO3-

Nitrogen bacterial transformations


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Organic N NH4+-N Heterotrophic ammonification or

mineralization. Associated with oxicor anoxic respiration.

NH4+-N NO3

- Involves oxygen (oxic). Autotrophicand chemosynthetic ("burn NH4

+-N

to fix CO2).

NO3- N2 (gas) Anoxic process. Heterotrophic.

("burn" organic matter and respireNO3

-, not O2).

N2 (gas) Organic N Some blue green algae are able to dothis.

Decomposition

Nitrification

Denitrification

Nitrogen fixation

Nutrients- The Nitrogen Cycle


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g y

modified from Horne and Goldman. 1994. Limnology. McGraw Hill.

Chemical forms

of nitrogen in aquaticsystems


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OrgN

N2 = largest reservoir

but cannot be used by

most organisms

Fixedoravailable-N

organism-N + detrital-N+ dissolved organic-N

NH4+

NO2-

NO3-

-3 +5+4+3+2+10-1-2Oxidation state

NO2N2ON2

gases

y

NH4+

NO2-

NO3-

Dissolvedinorganic-N (DIN)Ammonium:

basic unit forbiosynthesis Nitrite:

usuallytransient

Nitrate: majorrunoff fraction

Functionally in the lab using

filters


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filters

Total-N = particulate organic-N + dissolved organic-N

+ particulate inorganic-N + dissolved inorganic-N

TN = PN + DON + DIN

Dissolved inorganic-N = [Nitrate + Nitrite]-N + ammonium-N

DIN = NO3-N + NO2-N + NH4-N

Notes: Nitrate+nitrite are usually measured together.

Nitrite is usually negligible.

Assimilation Assimilation

Main N-cycle transformations


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Assimilation

(algae + bacteria)

Assimilation

-3 +5+4+3+2+10-1-2Oxidation state

Denitrification

NO2N2ON2

NH4+

NO2-

Mineralization

Org-N

N2 - Fixation- Soil bacteria- Cyanobacteria- Industrial activity

- Sulfur bacteria

Denitrification(anoxic bacteria)

Nitrification 1(oxic bacteria)

Nitrification 2

NO3-

Ammonification

gases

Anammox(anoxic bacteria)

N2 AmmoniaTribs, GW, Precip

Whole lake N-budget


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Surficial Sediments

N2

Algae

oxicanoxic

NO3- NH4

+

Nitrification

Assimilation

Mineralization

NH4+

NitrificationNO2

-, N2ONO

Sedimentation

DINPONDON

Sedimentation

DeepSediments BurialBurial

Ammoniavolatilization

Tribs, GW, PrecipDON, PON, NO3

-, NH4+

NO3-

Outflow

diffusion

N2-fixation

Mixing

Mineralization

Nutrients summer vertical profiles


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Oligotrophic Eutrophic

TT

O2 O2

NO3

NO3

PO4

PO4 NH4

NH4

0 0

anoxia

anoxia

Sulfide and iron summer vertical profiles


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TT

O2

O2

Soluble Fe

H2SH2S

Soluble Fe anoxia

anoxia

0 0EutrophicOligotrophic

instructor lecture 1 2

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