yournotes.org: ENMU - Freshwater and Limnology Notes

Freshwater and Limnology Notes: Lecture One

Modern biologists study organisms in an ecological context
- i.e. the characteristics are often understood in terms of adaptation to a particular environment
thus to learn about "freshwater biology" we need to study some aspects of limnology
- a segment of aquatic ecology
  - limnology is to inland waters as oceanography is to marine water
Limnological Terms
- Lentic habitat refers to ponds or lakes
- lotic habitat refers to streams and rivers or moving water
with few exceptions lakes arise from geological phenomena
- once formed there is a continual process leading to their filling with sediments
  - patter of succession:
    - lakes to marshes
    - marshes to swampy meadows
    - swampy meadows to forest
Lake regions
- Benthic: indicates bottom
  - often used as an adjective, e.g. "benthic fish"
  - the term "benthos" refers to the community of bottom living organisms collectively
  - one benthic zone in a lake is the littoral zone
    - the marginal region of the lake
      - often defined by the band of rooted vegetation from shore
      - subject to fluctuating temperatures and erosion of shore material through wave action and grinding of ice in some locations
        results in relatively course sediments
        especially true for unprotected shores
    - the littoral community of organisms is composed of many species and taxonomic groups
      - characterized by having high productivity
        many primary producers (algae and rooted plants)
        shallow, well lit, high nutrient load

sublittoral zone: this region goes lakeward from the littoral zone
- finer-grained sediments: washed fromt he littoral zone
- dimly lit: lacks most of the macroflora of the littoral zone
- still well oxygenated
profundal zones: found in lakes deep enough to exhibit summer temperature stratification
- a cold region is formed
- light is very reduced
- minimal currents or mixing
- oxygen is low or depleted
- CO2 is abundant
- low pH
- characterized by decay rather than production
- very fine sediments

Open water or pelagic zones
- the limnetic or pelagic is found beyond the "pond weeds" defining the littoral zone
  - the habitat of the plankton
    - an assemblage of drift organisms:phytoplankton(photosynthetic algae) and zooplankton(other protists and animals)
    - epi is sometimes added to pelagic to refer to surface dwelling creatures
    - the upper layer of the pelagic zone is called the trophogenic zone
      - light penetrates enough for photosynthesis
    - note that the littoral zone is bathed in trophogenic water and adds to primary productivity
      - yet its part in primary productivity is small except in shallow lakes
    - below the trophogenic zone is the tropholytic zone
      - respiration and decomposition predominate
      - organic compounds in this zone are typically broken down rather than synthesized
lakes are also divided by temperature
- top water is warm, bottom water is cold
- during warm and/or calm periods lakes may stratify
  - the epilimnion is the upper, well mixed, well illuminated, nearly isothermal region of a stratified lake
  - the hypolimnion is the poorly illuminated, lower region of the lake. It has denser colder water that is protected from the wind
    - lies over the profundal zone
- as water cools, it becomes more dense, so it sinks: thus the different density bodies of water do not easily mix
- the region where the change in temperatuer (and thus density) is greatest is called the mesolimnion, metalimnion, or thermocline

Algae
- formaly classified as plants
  - i.e. Kingdom Plantae
  - one of the five Kingdoms of life recall:
    - Monera: prokaryotes, i.e. cells that lack nuclei; all bacteria and blue-green algae
    - Protista: eukaryotic microbes; i.e. they have a nucleus and cytoplasmic organelles
      - products of bacterial symbosis and their descendants
    - Fungi: nonundulipodiated (no cilia or flagella), spore forming, haploids or dikaryons (i.e. contains 2 nuclie, usually one from each parent after sexual fusion-typical of fungi)
    - Animalia: diploid bastula formers; gametes of unequal size-where a bastula is an embryo stage (a hollow ball of cells) that goes on to form a gastrula, an embryo with the beginnings of tissues
    - Plantae: maternally retained embryo formers, haplo-diploid life cycles
      - i.e. gametophytes are n and produce gametes sporophytes are 2n
- Algae are a heterogeneous group of eukaryotic, unicellular, colonial, or multicellular aquatic organisms that are photosynthetic at some stage in their life history
  - Phyla in Protista
  - except for the blue-green "algae" which are cyanobacteria in the Kingdom Monera
Phylum Cyanophyta
- prokaryotic algae
  - lack nucleus
  - no complex organelles (e.g. chloroplast, mitochondria, etc.)
  - do have thylakoids: flattened vesicles where photosynthetic systems are located
- no prokaryotic algae have cilia or flagella
- a very ancient group; has existed for over 3 billion years
  - still important in our ecology today
  - often problematic in the quality of drinking water
Green Algae
- Phylum Chlorphyta
  - usually bright green
    - pigments in chloroplasts
    - cells with well defined nuclei
  - occur in a variety of forms
    - single cells
    - round and/or flattened colonies
    - filaments
  - more abundant in ponds and lakes than all other algae groups combined
Lakes are put into one of two major categories: oligotrophic or eutrophic lakes
- oligo=few, scant, small
- troph=nurishment or food
- eu=good or well
- oligotrophic= small food or nourishment
- eutrophic= good food or well nurished
- yet classifing a lake as oligotrophic or eutrophic usually means much more
- know table 2.1 p.12
- general nutrient condition of water is often referred to as being due to edaphic effects
  - where edaphic is in reference to soil or ground conditions and their influence
    - e.g. soils rich in nutrients lead to eutrophic conditions
      - such a lake would be said to have primary eutrophy
- lake morphology may be more important than edaphic conditions in the determination of trophic state
  - e.g. the epilimnion/hypolimnion ratio
    - i.e. the E/H ratio
- given a large E/H ratio, the oxygen in the hypolimnion is rapidly depleted
  - thus even what might be considered oligotrophic water conditions (e.g. based on nutrient loading of the water) might lead to eutrophic conditions with a high E/H ratio
    - in this case the lake is said to exhibt a secondary eutrophy
  - low E/H ratio may cause classification of lake as secondary oligotrophy
finally there are dystrophic lakes
- dys=bad
- dystrophic= bad food or nutrients
- leads to bog lakes
- often found in northern waters
  - e.g. on the Canadian Shield
    - here edaphic conditions lead to water that is calcium poor, acidic, low in electrolytes, and has poor transparency
    - transparency due to humus
    - water is brown in color
    - such lakes are typically fringed with floating vegetation and mats
      - e.g. Sphagnum moss
    - dystrophy appears to be connected to the blocking of bacterial decomposition of vegetation by bacteria
      - calcium limited
  - strict classification of lakes is difficult because a lake may be a mosaic of oligotrophic and eutrophic conditions in space and time
  - lakes have been classified by annual productivity from 6CO2 + 6H2O >>solar energy>> C6H12O6 + 6O2
    
    Conditions Productivity in grams C per m^2 per year
    
    oligotrophic 7-25gC/m^2/yr
    
    mesotrophic 26-74gC/m^2/yr
    
    eutrophic 75-250gC/m^2/yr
    
    polluted lakes 350-700gC/m^2/yr
  - specific sediments are also typical of trophic conditions
    - sediments may be allochthomous
      - which is derived elsewhere
    - sediments may be autochthomous
      - which are self-made
      - autochthomous sediments are usually made of diatom frusules (chrysophyta), sponge spicules, and calcium carbonate
  - oligotrophic lakes have small, mineralized deposits
    - organic content is small due to
      - low productivity
      - abuandant O2 in the hypolimnion promotes decomposition by bacteria
  - alternatively eutrophic lakes have organically rich sediment
    - mixture of humus, fine plant fragments, algal remains, diatom frustules, insect exoskeletons and fragments, spore and pollen remnants, feces from a large benthos that mixes the sediment
    - this sediment is referred to as copropal
      - color from gray to dark brown
    - long periods of anoxia lead to sapropel
      - glossy black and gives rotten egg odor (H2S)
      - sapropel may lay as a layer over copropel
    - environmental conditions specifically anoxia usually precludes the formation of a macrobenthic fauna
    - some lakes alternate in conditions such that they produce sapropel only during the most productive times of the year
    - sapropel can be a sign of pollution
    - sediments in dystrophic lakes are called dy(du)
      - yellow-brown, flocculant(fluffy), fibrous plant material
      - layering occurs
Phylum Chrsophyta
- diatoms, golden, and yellow-green algae
- unicellular or colonial
  - rarely filamentous
- pigments are found chloroplasts
  - yellow, brown, or golden-brown predominate
    - includes 3 chloroplasts, 3 carotenes, 7(possibly up to 16) xanthophylls
- food storage: oil or chrysolaminoran (leucosin)
  - starch test negative (this is positive with almost all green algae)
- thick walled
  - diatoms have a silicified frustule (shell)
    - frustule made of two valves
      - often fit together as a "pillbox"
    - may be penate or centric
    - predominate member of the plankton
    - benthic forms too
    - frustules with pits and lines so fine that they are often used to test microscopes
    - some diatoms are propelled by a band of cytoplasm streaming along a slit in the valve (often along a raphe)
- Reproduction has been studied best in the diatoms
  - diatoms undergo mitosis while encased in the frustule
    - forces the valves to seperate
    - new valves form inside older valves
  - results in a population containing smaller diatoms (down to half the size of the large sized individuals)
  - at the lower limit, small cells become sexual and produce gametes
    - diatoms are 2N (diploid), but the pattern of meiosis is species specific
      - some show oogamy
        oocytes (egg cells) are produced 3 of 4 meitic products discentigrate with the remaining product becoming an egg
      - some show isogamy
        produce isogametes
        2 of 4 products of meiosis discentigrate
        remaining 2 form equal sized flagellated (mobile) gametes (N)
        
        isogametes fuse with other isogametes and form a zygote(2N)
        called auxospore
        expands considerably before frustral formation
Origin of Lakes
- Depressions in the Earth's crust that fill with water
  - most are associated with geological phenomana
- Glacial Lakes
  - many lakes are recent
  - glaciers are very important in formation
    - during the last ice age approximately 31% of the worlds land area was covered with ice
      - only 17,000 YA (Years Ago) ended some 6,000-7,000 years later
  - lakes associated with exsisting glaciers
    - pools on top
    - pools beneath
  - lakes near glaciers
    - melted ice in premafrost areas form pools
    - pingo lakes: eskimo word for mound
      - mound forms
        water under pressure rises through the permafrost
        freezes and forms an ice dome
        the dome ruptures and exposes the ice which melts
        weight of the water forms a crater and lake
  - Lakes formed where glaciers were
    - lakes in ground moraine
      - moraine is drift materials desposited directly by the glacier
      - Kettle or pit lakes
        a huge block of ice sits in the moraine; when the block melts a lake is formed
        compression from the block forms the lake basin
    - Lakes formed by morainic impoundment
      - lateral moraine blocks a tributary
      - terminal moraine blocks river
      - both cause basin and eventually lakes to form
    - hydralic force lakes
      - melted ice under pressure from a glacier forms a trough in the ground moraine
        forms a basin
    - simple corrasion leaves depressions behind
      - e.g. Great Slave Lake
- Tectonic Lakes
  - depressions formed by movement of the earth's crust
    - Graben, fault-trough or Rift lakes
      - land between two faults sinks to form a graben lake
        e.g. Lake Tahoe
      - the two deepest lakes in the world are rift lakes
        Lake Baikal and Lake Tanganika
    - Uplift Lakes
      - epeirogenic lakes
        i.e. lifted
        e.g. Caspian Sea was once a submarine depression
        was lifted and subsequently freshened
        
        Lake Titicaca high in the Alps
    - Landslide Lakes
      - e.g. Mountian Lake in Virginia
        a landslide dams a mountain valley and water collects
- Lakes of Volcanic origin
  - Crater Lakes
    - lakes left in craters of dormant volcanoes
      - e.g. Crater Lake, Oregon and Zuni Lake, New Mexico
  - lakes in lava depressions
    - cauldron subsidence
      - e.g. Lake Atitlan, Guatamala
      - e.g. old lava tubes that fill with water
    - Coulee lakes
      - lakes formed by lava empoundment of a river valley
      - e.g. Lake Kiuv, Africa
- Solution Lakes
  - basins made by dissolution may later hold water and become lakes or ponds
  - the term karst characterizes surface and subsurface regions where carbonate rocks, particurally limestone, are exposed to water
    - many underground passages and channels
    - surface water is scarce
    - circulating water removes soluble materials
      - weakens surface layers
      - eventually makes depressions called sinking dolinas and swallow holes
  - salt-collapse basins
    - evaporites(e.g. salt pockets NaCl, Calcium sulfate) pockets
    - water entering a pocket causes expansion and cracking of rocks above
    - salt is carried away in solution
    - fractured rocks collapse leaving a nearly circular lake
      - e.g. bottomless lakes of New Mexico
- Lakes of Aeolian origin
  - EasternNew Mexico is in a lake district
    - 1,000's of shallow depressions in the panhandle of Texas and adjacent New Mexico
    - called buffalo wallows or playas
    - rain-filled depressions attract herds that trample the soil
    - stabilizing plant growth is destroyed and the basin deepened
    - when the depression is dry, wind then removes dry soil
      - called deflation
- Floviatile (River) Lakes
  - Impoundment of a stream can occur with a second river
    - Levee lakes
      - shallow elongate lakes lying parallel to a river
      - river deposits sediments creating a levee that forms a lake
    - Oxbox lakes
      - meanders are cut off from the main stream
        usually deeper than levee lakes because they are old segments of the main river channel
    - Evorsion (pot-hole) lakes
      - lakes formed under waterfalls
        e.g. Grand Coulee lakes, Washington state
      - erosion from water movement makes the basin
    - Shoreline Lakes
      - formed where barriers of sand are made and lagoons are cut off from the ocean
      - frequent along low elevation coastlines
- Basins impounded or excavated by organisms
  - Humans! (moranic)
    - other organisms
      - e.g. Castor - beaver impound streams and flood steram side vegetation
      - e.g. Sphagnum and other bog plants have been reported to form impoundments
    - various algae and mosses can trap CaCO3
      - results include the formation of plant-limestone barriers
- Extraterrestrial objects
  - astroblems (star scars)
    - impact makes a basin
      - e.g. New Quebec Crater Lake
      - e.g. Northern Arizona Meteor Crater
        remnants of a pluvial lake
        estimated to have existed approximately 11,000 ybp (years before present)
Phylum Rhodophyta
- predominately marine
- simple or branched filaments
- pigments in chloroplasts
  - 2 chlorophylls
  - 2 carotines
  - 3 (up to 14) xanthophylls
  - phycoerythrin and phycocyanin
    - phycoerythrin: red pigmented algae
      - erythrin: red
      - reduced in freshwater genera
      - the algae appear gray-green to tan in color
      - storage "floridean starch"
        iodine negative
      - walls are thick
        contain porcous connections which are intercellular
      - highly mucilaginous
      - thalli are often macroscopic
Phylum Pyrrhophyta
- unicellular (solitary)
- 2 flagella
  - usually lateral in attachment
    - one wraps around the cell in a transverse furrow
- cell walls usually in polygonal plates
  - e.g. armored thecae
- pigments in chloroplasts include
  - 1 chlorophyll
  - 2 carotenes
  - 4 (up to 6) xanthophylls
  - peridinin and dinoxanthin most abundant
- food reserve is starch
Phylum Euglenophyta
- cells solitary, unicellular
  - usually 1 flagellum (rarely up to 3)
  - gullet (cavity) at the anterior end is found in many
- pigments in chloroplasts
  - 1 chlorophyll
  - 4 carotenes - often has a red carotenoid heamatochrome
  - up to 5 xanthophylls
- food storage - insoluble starch
Phylum Sarcomastigophora
- flagella, pseudopodia, or both
  - i.e. both types of locomoter organelles
- unicellular or colonial
- one type of nucleus (unlike ciliates)
- Subphylum Mastigophora (flagellates)
  - one or more flagella
  - solitary or colonial
  - asexual reproduction by binary fission
  - may be photosynthetic, heterotrophic, or both
- Subphylum Sacrodina (amoeboid forms)
  - pseudopodia are present
  - flagella sometimes present, but only during developmental stages
  - cells are usually naked
  - asexual reproduction by fission
    - e.g. Amoeba
Streams and Rivers - Lotic Environments
- i.e. running water
- Classification - Stream Order
  - 1st order streams lack tributaries
    - headwaters; terminal twigs
  - At least two streams of any given order are required to form the next higher order
  - There are two problems two problems with classfication due to stream intermittency
  - A stream network occupies a catchment area
    - Catchment area usually equals a drainage area
      - catchment area is composed of falling water
      - drainage area is composed of other waters
        i.e. underground spring
      - sometimes groundwater is added to the stream network scuh that the drainage area is greater than the catchment area
Types of water flow
- Laminer flow: if you made a unit of water the units move together with neighboring units
  - i.e. mixing does not occur
  - characteristic of viscous fluids
  - only occurs in water when it moves very slow
- turbulent flow arises with increases in water velocity
- - neighboring liquid units may move in different directions
    - and at different velocities
  - water is erratically mixed
- discharge is the product of width times depth times velocity, anyone of which can in a stream over short distances
- river 200m wide times 4m deep flowing down a gradient of 0.5m/km would have a velocity 1.2x that of a river 20m wide times 0.5m deep with a gradient of 5m/km.
Velocity should be determined for most freshwater biology studies
- current at about 6/10 of depth is considered a close approximation to average velocity
Transport of Materials
- a stream's competence is the largest grain size that the current can barely move
  - the stream will have
    1. dissolved matter
      - e.g. inorganic ions
    2. washload
      - fine suspended material
        e.g. clay particles which settle slowly; usually visible as turbidity
    3. suspended load
      - larger suspended particles
        e.g. silt and sand
    4. bed load
      - larger particles
        e.g. coarse sand, pebbles, or larger
        too large to be suspended
        ocassionally skip, bounce, or slide
  - capacity of a stream is the theorical load that a stream can transport
- Longitudinal profile and the principle of grade
- - typical longitudinal profile: slightly concave line to the sky
    - gradient usually flattens to the sea where deposition takes on more importance
    - erosional features predominant in the upper reaches
    - description of erosion and deposition is a matter of scale
      - e.g. streams may be characterized by alternating pools and riffles in the middle reaches
  - size of alluvial grains transported decreases rapidly after the headwaters
  - deposition downstream smooths out the channel
- Grade
  - Load > capacity; a stream is aggraded (material is deposited)
  - Load < capacity; a stream is degraded (material is eroded)
  - a graded stream is in a dynamic equilibrium between erosion and deposition
- Patterns of Channels
  - If a river channel travels < 1.5x the linear distance between an upstream point and a downstream point, the reach is classified as straight
  - Otherwise if A > or equal to B times 1.5, the reach is said to meander
    - Meanders
      - complex loops or bands in streams
      - create diverse habitat for river biota
        A = concave bank
        location of greatest velocity
        water is slightly elevated
        bank is eroded
        
        B = convex bank
        alluvium is deposited
        opposite of A
      - the deep channel of a river, the "thalweg" is actually rather winding even for straight reaches
      - "braided streams" form when there is more than one channel
        have elongate bars and islands seperate channels
        appear to be a function of alluvial load
        high load streams often cut more than one channel
    - River's Mouth
      - most large rivers have a build-up of alluviam and form a delta
        delta is often cut up by distributaries
    - The river continuum - nominal
      - Headwaters: typically streams orders 1-3
      - Medium sized streams or rivers: typically orders 4-5
      - Large sized rivers: typically orders greater than 6
Phylum Ciliophora - ciliates
- have cilia or composite ciliary organelles
- two types of nuclei
  - macronucleus (large)
  - micronucleus (small)
- reproduce asexually through binary fission
- several types of sexual reproduction
  - conjucation
    - pairs unite along lateral edges
    - nuclear phenoma are species dependant
      - macronuclei disintergrate
      - micronuclei exchange materials then unite to form a single nucleus in each conjucate
        after seperation the macronuclei reappear
  - autogamy
    - macronucleus is absorbed
    - series of divisions of micronuclei
    - reformation of the macronucleus
  - both conjucation and autogamy give new genetic combinations

Lecture Two

Phylum Porifera (Sponges)
- -there are about 4500 species of sponges
  - -almost all are marine
- -a single family, spongillidae (~170 species(30 from the US)) is found in freshwater
- -usually found in clean waters
  - -both in lotic and lentic environments
- -often go unnoticed
  - -"fouling" or encrusting organisms
- -sessile
- -inconspicuous green, brown, gray, or yellowish
- -general characteristics of freshwater sponges
  - -size - highly variable
    - -depends of appropriate substrate, nutrition, current, different species, growth(age)
  - -range from thin, slimy and delicate mats of a few square centimeters to over 40 square meters
  - -thickness 1mm to 4cm
  - -growth forms range from mat-like (flat) to having numberous papillae (fingerl-like out growths) and branches or lobes
  - -growth form is not a good diagnostic character
    - -variation is intraspecific
      - e.g. Spongilla lacustris has every variation
        -simple encurstration to finger-like processess
  - -in general, particular species are more lobate and have more projections in lentic environments
    - -lotic environments select for encrusting forms
  - -the living portion of a sponge is only the outermost strata ~ 4 to 20mm thick
  - -living material is often growing in the remains of the previous years growth
    - -coloration - due to many factors
  - -most species found where direct light reaches them are some shade of green
    - -they often contain chlorella
  - -same species under objects or in deep water are tan, gray, or flesh colored
    - -sponges have a relatively simple construction
      - -no organs
      - -tissues are relatively unspecialized and loosely organized
      - -the external surface has openings of two general sizes
  - -ostia (ostium=singular): microscopic openings that are abundant everywhere in the epidermal membrane
  - -oscula (osculum=singular): relatively large � to 2mm in diameter openings
  - -a osculum is typically located at the distal end of a small chimmey-like projection
- -Water Pathway
  - -small currents of water run through a sponge
    - -pathway starts by going in ostia and ends by exiting oscular chimneys
    - -ostia open into an extensive subdermal cavity
      - -the floor of the cavity ahs incurrent canals
        -which lead more deeply into the sponge
    - -incurrent canals lead to spherical cavities, the flagellated chambers
    - -flagellated chambers are emptied by excurrent canals
    - -excurrent canals empty into a much larger, irregular central cavity
    - -central cavity has an osculum, which empties to the outside
- -Skeleton
  - -Freshwater sponges have needle-like microscopic spicules
    - -support flimsy tissues
    - -larger spicules are called mega-scleres
      - -form a reticulate network in a sponge
      - -some may be haphazardly found throughout tissue
      - -others are arranged in fascicles
      - -radiating fascicles orient from the base of the sponge to the surface
        -often poke through to the outside
        -give protection as well as support
      - -transverse fascicles run between the radiating fascicles
      - -smaller spicules are called micro-scleres
        -these are the so called "flesh" or dermal spicules
        -found in the epidermal portion of the sponge body
        -haphazard arrangement; rarely in fascicles
        -lacking in some species
      - -Mega and micro scleres may have sharp or blunt points, spines, etc, in species specific distributions
      - -Spicules are made of about
        -92% silicon dioxide
        -7% water
        -rest is small amounts of Mg/K/sodium oxides
      - -made in specialized amaebocytes called silicoblasts
- Nutrition
  - -sponges strain minute particles from the water
    - -usually to about 50microns
    - -drawn in the ostia, down the incurrent canals, to the flagellated chambers
    - -the opening of a flagellated chamber is called a prosopyle
    - -flagellated chambers are lined with "collar cells" called choanocytes
    - -each choanocyte has a distal collar of microvilli surrounding a single flagellum
    - -bacteria and detritus get caught on the collars
      - -food is phagocytized: i.e. engulfed by the choanocytes
      - -digestion is thus intracellular, but little takes place in the choanocytes
        -particles are passed to the mesoglea matrix surrounding the flagellated chamber
      - -later, the particles are picked up by amaebocytes in the mesoglea matrix
        -digestion is completed in the amaebocytes
      - -water leaves the apopyle
        -empties into the excurrent canal
      - -flat cells lining surfaces are called pinacocytes
        -they are capable of phagocytosis
        -food particles are also passed to them by amaebocytes
        -note that all the cell types are derived from totipotent archeocytes
        -note also that prosopyles often get clogged with debris
        -they are cleaned by amaebocytes
        -note also that many sponges contain zoo-chlorellae
        -these may live intra and/or intercellular, but are not essential to sponge metabolism
        -yet sponges have been shown to grow better in their presence
        i.e. they use the photosynthate from the algae
  - -Circulation : there are no special circulatory mechanisms
    - -materials move through diffusion and by transport by amaebocytes
  - -Respiration : simple diffusion
    - -all cells are in contact with water or just a few cells from it
  - Reproduction and Growth "Obscure and confused"
    - -In the spongillidae
      - -simultaneous hermaphroditism
        -both female and male functions at the same time
      - -sequential hermaphroditism
        -polarity is uncertian or even alternating
      - -gonochorism : separate sexes
    - -sperm and egg production occur mostly in July and August
      - -oogonia (egg cells) are produced from specialized amaebocytes that grown and injest adjacent amaebocyte "nurse cells"
        -by maturity the oocyte is large and lies loosely in the internal cavity of the sponge
      - -sperm develops from special choanocytes that lose their collars and flagella
        -they become amoeboid and migrate to the mesoglea matrix
        -here they are called spermatogonia
      - -sperm is released into the central cavity and out the osculum
        -eventually it is taken up by other sponges
        -fertilizes eggs
        -makes a flagellated embryo
        -release and swims for a few hours (days?) before settelment
        -metamorphoses into a young sponge
- -Most of the sponge dies in autumn
  - -sometimes reduction bodies are made during unfavorable conditions
    - -tissues shrink and collapse
      - -canals disappear
- -Gemmules : are left when a sponge goes through its annual "die off"
  - -spherical structures with a dead, secreted outer layer covered with spicules
    - -"resting stages" for over winter
      - -inside are undifferentiated, food filled, archeocytes
  - -150 to 1000 microns in diameter
  - -deposited in a compact basal layer in a sponge - or scattered throughout the sponge
  - -they withstand repeated freezing
    - -viable even after being dry for 1 to 2 years
  - -germinate when water 13 to 23C
    - -takes a few days in spring
    - -archeocytes differentiate
      - -spicules, channels, and subdermal spaces can be formed as early as the 3rd day
        -functional choanocytes by day 5
  - -sponges generally occur in waters <2m deep
    - -rarely on mud or silty water
  - -sponges are substrates for may animals
    - -e.g. insects (larvae) crustaceans, water mits, annelid worms, nematode worms, and mullusks
    - -even other sponges
      - -some sponges settle on others of the same species
        -fuse to form genetic mosaics
Significant differences in Science
- -What does a scientist mean when he/she says there is a �significant� difference between study areas, populations, means, etc.?
- -many of the problems we address cannot be qualitatively answered.
  - -i.e. there is no �common sense� solution; the answer is not obvious
    - -given this, we use a �statistical sense� solution
      - -that is, the answer is viewed as a probability
typical method to investigate hypotheses
- -design a study with an analysis in mind **
- -develop a null hypothesis and an alternative
  - i.e. a no relationship, no difference, or no influence hypothesis and its alternative
- -calculate a test statistic
  - -statistic will depend on the test(analysis) used which will in turn depend on the design of the study
- -compare the test statistic with a critical value in a table
- -determine P
  - -where P is the probability of obtaining the statistic value if the null hypothesis is correct
    - -p must be � 0.05 to be able to claim significant differences in science
- -conclusion
  - -if P greater than or equal to 0.05, reject Ho (null hypothesis)
  - -if P > 0.05, fail to reject Ho
There are two major groups of analyses
- -parametric analyses
  - -use distributions of parameters (actual measurements) in analyses
  - -assume bell shaped distributions
- -non-parametric analyses
  - -parameters (measurements) are ranked
  - -use distributions of the ranks (not the actual parameters) in the analysis
  - -benefit: no assumptions of normality
  - -cost: slightly less powerful than parametric analyses
    - -fewer analytical techniques available
Correlation vs. Regression
- -In correlation problems there are no independent variables
  - i.e. variables which clearly are not influenced by the other variable (graph below)
  - -correlation problems have four potential patterns with three results (graph below)
  - in regression problems there is an independent variable (graph below)
  - -a regression equation ^Yi = a + bXi determines the best fit line through the cloud of data (graph below)
    - ^Yi = predicted value of Y
    - a = y intercept
    - b = slope of regression coefficient
    - Xi = value of X in question
D�Agostino test for Normality
- -in order to use parametric tests we need to show that the data are not significantly different from a normal distribution
- -we can do this with a relatively simple test
  - -we calculate the statistic �D�
    - -then compare D to a table to give us P, the probability of getting a d value so extreme from a population with a normal distribution
- Ho: Our sample came from a population that is not significantly different from a normal distribution
- Ha: Our sample came from a population that is significantly different from a normal distribution
- -if Dcalc is greater than or equal to or less than or equal to Dcrit. Limits, reject Ho
  - -Dcrit Limits is a range which is used to test hypothesis
    - -n=10 0.2513, 0.2849
  - Hypothetical Data Set
    
    I Xi(g) Xi^2
    
    1 3 9
    
    2 5 25
    
    3 6 36
    
    4 9 81
    
    5 10 100
    
    6 11 121
    
    7 12 144
    
    8 12 144
    
    9 18 324
    
    10 19 361
    
    Sums 105 1345
  - D = T divided by the square root of (n^3 multiplied by SS)
  - SS = Sum of Xi^2 minus {(the sum of Xi)^2 divided by n}
  - T = Sum of {(I minus [(n plus 1)/2]) multiplied by Xi}
  - IN OUR SAMPLE:
    - SS = 1345 - (105^2)/10 = 1345 - 11025/10 = 1345 - 1102.5 = 242.5
    - (n + 1)/2 = (11)/2 = 5.5
    - T = Sum of (1-5.5)3 + (2-5.5)5 + (3-5.5)6 + ... = -13.5 + -17.5 + -15 + ... = 137.5
    - D = 137.5 / square root of (10^3 x 242.5) = 137.5 / square root of (242500) = 137.5 / 492.44289 = 0.27922
    - Since Dcalc is found within the critical range we fail to reject Ho
Simple Linear Regression Example
- e.g. biomass(g) as a function of depth of a lake(cm) for dredge samples
- Hypothetical Data Set
  
  Depth(cm):X X^2 Biomass(g):Y Y^2 XY
  
  95 9025 100 10000 9500
  
  190 36100 200 40000 38000
  
  310 96100 305 93025 94550
  
  400 160000 380 144400 152000
- Sum of X = 995
- Mean of X = 248.75
- Sum of X^2 = 301225
- Sum of Y = 985
- Mean of Y = 246.25
- Sum of Y^2 = 287425
- Sum of XY = 294050
- n = 4
- -remember the general regression equation:
  - ^Yi = a + bXi, where a= y-intercept; b= slope of the regression coefficient
  - Sum of x^2 = Sum of X^2 - (Sum of X)^2/n = 301225 - (995)^2/4 = 301225 - 247506.25 = 53718.75
  - Sum of xy = Sum of XY - [(Sum of X)(Sum of Y)]/n = 49031.25
  - slope = b = (Sum of xy)/(Sum of x^2) = 49031.25/53718.75 = 0.91g/cm
  - y-intercept = a = �y bar� - b�x bar� = 246.25 - (0.91g/cm)(248.75) = 19.89g
- Biomass (^Yi) = 19.89g + (0.91g/cm)(Xi cm)
  - What is the predicted biomass at 220cm?
    - -Biomass = 19.89g + (0.91g/cm)(220cm) = 19.89g + 200.20 = 220.09g

Lecture Three

Phylum Rotifera
- -This phylum occurs almost entirely in freshwater
  - -about 2500 species are described
    - -less than 5% are marine or brackish water species
  - -most are microscopic
    - -range in length from ~40microns to 3mm
      - -but most are between 100microns and 500microns
  - -they get their name from the disc-like ciliated anterior end
    - -illusion of a revolving wheels
  - -they live in many environments
    - -damp soil & vegetable debris
    - -interstices of sand on beaches
    - -benthic in lentic or lotic environments
    - -planktonic in lentic or lotic environments
    - -small rock depressions
  - -vast majority of rotifers are female
    - -males are known for only a few species
      - -where known, they are smaller than females, and often short lived (e.g. 2-3 days)
  - -Rotifera is divided into two classes:
    - -Class Digononta - paired ovaries
      - -in turn divided into two Orders
      - -Order Seionidea: marine
      - -Order Bdelloidea: almost entirely freshwater
        -males are unknown
        -reproduction is through parthenogenesis
        -body is highly contractile
        -rotifer creeps about
    - -Class Monogononta - single ovary
      - -90% of known rotifers belong to this class
  - -Rotifers are morphologically diverse
    - -elongated, saccular body
    - -three main body regions
      - -head, trunk, and foot
        -foot is usually a narrow region
        -telescopic in bdelloid rotifers
        -2 to 30 syncytial masses called pedal glands
        -foot terminates in toes or spurs
  - -rotifers lack true body segmentation
    - -body is covered by a cuticle
      - -part of the epidermis
        -called a lorica if highly thickened over the trunk
  - -rotifers have a peculiar structure found no where else among animals: the mastax
    - -used in food processing(tearing, sucking, grinding, etc)
    - -seven hardened parts (trophi)
      - -vary in form and function depending on the species
  - -anterior discs on rotifers are called a corona
    - -creates currents that move water (with food, oxygen, etc)
      - -may concentrate small plankton & detritus
- -majority of species are omnivores
- -some species are predatory and feed on other rotifers
- -some species that feed primarily on algae can be considered herbivores
- -a mouth opens to a narrow, ciliated, pharynx
  - -leads to the mastax, then to a ciliated stomach (most digestion and absorption), to an intestine (distinct or indistinct), to a cloaca (at the base of the foot)
- Respiration
  - -generally, plankton often have high oxygen requirements
    - -especially littoral species
  - -some rotifers can withstand hypoxic conditions 0.1 to 1.0 mg/L DO
- Reproduction
  - -the monogononta have a sac-like reproductive system
    - -the ovary is small and consists of developing oocytes
      - -it rests atop a vitelarium, which is a syncytium with large nuclei
      - -egg mature one at a time
      - -vitelarium contributes yolk to the egg
        -egg becomes large
        -passed down a short oviduct
        -exits out the cloacal aperature
- -the largest order of the class monogononta is the Ploima
  - -ploimate rotifers have two types of females
    - -morphologically indistinguishable
  - -amictic females - reproduce most of the year
    - -always by parthenogenesis
    - -diploid (2N)
    - -produce amictic eggs that are diploid(2N)
  - -mictic females - reproduce only during short times of the year
    - -diploid (2N)
    - -produce haploid (N) eggs
      - -often called "winter" or "resting" eggs that are 2N after fertilization
  - -if mictic females are not fertilized by a male, they produce "male eggs"
    - -that are haploid(N) and quickly hatch into males
  - -if mictic females are fertilized, they will produce the winter or resting eggs that over winter and hatch into amictic females
- Typical Sequence of Generations
  - -usually only 1 or 2 mictic generations per year and about 20-40 amictic generations
  - -amictic eggs (2N, sometimes called summer eggs) usually hatch in a day or two
  - -mictic - resting or winter eggs - are heavy, thick shelled, often sculptured
    - -require several weeks to months before they hatch
  - -hatching stimulated by temperature change, osmotic pressure, even the presence of algae
Phylum Arthropoda
- -a vast assemblage of animals
  - -more than 3 times the number of all other animals combined
- Class Crustacea
  - -Classification: Pennak, R.W. 1989. Freshwater Invertebrates of the United States(3rd ed.) Wiley, NY
  - -four obvious features
    - -aquatic arthropods(with terrestrial isopods; an exception)
    - -respiration is through gills and body surfaces
    - -all have two pairs of antennae
    - -most body segments have paired, jointed appendages(at least the anterior body segments)
      - -body segments are often fused
      - -appendages are usually biramous(forked or branched)
    - -there are about 36000 species of crustaceans(number continues to grow)
      - -13 Orders are strictly marine
      - -12 Orders have representation in freshwater
        -5 of these Orders are found exclusively in freshwater
- -the primitive body plan includes a segmented trunk and a head with completely fused segments
  - -the trunk is usually divided into a thorax and an abdomen
    - -results in three general body regions: head, thorax, and abdomen
  - -yet more derived conditions often include fusion of body segments
    - e.g. one or more thoracic segments may be fused with the head
      - -results in a cephalothorax
    - -in many crustaceans, the cephalothorax is partially or wholely covered by a shield-like carapace
    - -also note that the most posterior division of the body(bearing the anus) is not considered a true body segment
      - -usually referred to as a telson
        -often adapted for locomotion
      - -in other groups the telson resembles other body segments
        e.g. may have caudal rami(ostracod), may have cercopods(ferry shrimp), or claws(cladocera)
      - -in groups such as the Orders Cladocera(water fleas) and Podocopa(seed shrimps) body segmentation has disappeared
- Subclass Branchiopoda
  - -Division Eubranchiopoda(true branchiopod)
    - -Fairy, Tadpole and Clam Shrimps
    - -Characteristic inhabitants of temporary ponds and pools
      - -especially during spring and early summer
    - -often found near the bottom
      - -swim, often with the ventral surface upward
    - -absent from lotic environments
    - -Order Anostraca
      - -fairy shrimps
      - -includes Artemia salina: common brine shrimp
    - -Order Notostraca
      - -tadpole shrimp
    - -Order Conchostraca
      - -clam shrimp
  - -Division Oligobranchiopoda (few branchiopods)
    - -contains the Order Cladocera
      - -water fleas
      - e.g. Daphnia
      - -swim by a rapid movement of two large antennae
      - -thorax is covered by a shell-like carapace
        -fused dorsally
        -open ventrally
      - -feed by filtering food particles with 5 pairs of thoracic appendages
        -appendages are covered with setae
      - -captured food is collected in a median ventral groove (between the appendages)
      - -passed forward to the mandibles before entering the mouth
      - -locomotion
        -primarily through antennae strokes
        -locomotion is intermittent
        -characterized as "hopping"
        
        -locomotion varies with circumstance
        -fewer, stronger beats are used in the presence of predators(chemicals) in Ceriodaphnia
        -it covers more distance per stroke in the presence of predators
      - -feeding
        -algae and protists are important food sources
        -but detritus is also ingested
        
        -selectivity is largely by size rather than substance
        -mechanisms of selection are:
        
        spacing of setae on thoracic appendages
        spines at the base of the 1st pair of appendages
        -they remove larger masses or "undesirable" materials
        
        the spacing of valves
        -the valves close in Daphnia when the concentration of pelagic algae is high
        
        -most genera are filter feeders
        -some genera are raptorial predators
        -thoracic appendages are modified for seizing prey
        e.g. Polyphemus and Leptodora
      - -cladocerans are largely energy maximizers, in that they have nearly continuous feeding
        -the gut is usually full
  - -digestive system is relatively unspecialized
    - -esophagus opens to a stomach that is hard to distinguish from intestine
      - -few genera have intestinal caecae
      - -blink pockets
        -often enzymatically active
    - -ingested algae can be passed, undigested, from the digestive system
      - -some cladocerans exhibit "anal drinking"
  - -respiration
    - -cladocerans have an open circulatory system
    - -they have a simple, oval-shaped heart
      - -behind the head on the dorsal side
      - -its beating distributes blood throughout a hemocoel
    - -no blood vessels, but thin mesenteries that help guide the blood
      - -blood plasma is colorless or faint yellow
        -contains numerous colorless formed elements, corpuscles
      - -populations with high concentrations of hemoglobin are selected for in hypoxic environments
    - -gas exchange occurs through general body surfaces
    - -especially the inside surfaces of the carapace valves and through
    the thoracic appendages
  - -reproduction
    - -gonads are only easy to identify in mature individuals
    - -ovaries lie ventral and lateral to the intestine
      - -dense and granular
        -or contain large pigmented granular yolked eggs
    - -testes are smaller
      - -similar location, but contain granular sperm
    - -most reproduction is by parthenogenesis
      - -only females are produced
      - -eggs are released from the ovary into the brood chamber
      - -number of eggs(zygotes) per clutch varies
        -most frequently 10-20
      - -eggs develop in the brood chamber
        -hatch into young similar in form to adults
    - -under adverse or changing conditions, haploid eggs are produced
      - -these need fertilization by a male
    - -males are also produced parthenogenetically
      - -no clear proximate control mechanism for the production of males has yet been identified
        -rough correlations with:
        crowding
        decrease in available food
        low temperature e.g 14-17C
      - -haploid egg production occurs at the same time
        -only one or two sexual(haploid) eggs are produced at a time
        -fertilized eggs pass to the brood chamber
        -brood chamber becomes thickened, pigmented, and forms the ephippium
        -these usually sink to the bottom(some float, species specfic)
        -those that float may form small wind rows on lake shore
        -ephippium can withstand drying and freezing
        -even viable after ingestion by some fishes
  - -seasonal abundance
    - -some general patterns of abundance can be characterized for cladocerans
      - -Early spring: few cladocerans
        -populations consists of the few females that survive winter
        -also recently hatched females from ephippia
        -water warms and results in asexual reproduction
        -begins at temperatures 6-12C
        
        -results in large populations later in spring
        -as high as 200/500 individuals per liter
    - -monocylic - spring pulse (population maximum)
    - -dicyclic - spring and fall maxima
    - -acyclic - no pronounced population maximum
      - -some large, cold lakes
  - -life span (and generation time) is highly variable
    - -depends on species
      - -temperature is also very important
    - -Daphnia magna
      
      Degrees C 28 18 8
      
      average life span(days) 26 42 108
  - -Cladocerans have four distinct periods in their life history;
    - -egg, juvenile, adolescent, adult
    - -eggs (parthenogentic or fertilized) are deposited into the brood chamber
      - -development has already begun
    - -juveniles are released from the brood chamber in about 2 days
      - -juveniles are in their first instar
      - i.e. life history periods may consist of one or more instars
        -at the end of an instar, the hard exoskeleton is shed and the animal grows
      - -the greatest growth occurs during juvenile instars(yet they are few in number)
        -2 to 5 juvenile instars
        -species and environment dependant
        e.g. Moina 2 instars
        Daphnia magna 3-5
    - -adolescent period is a single instar
      - -between juvenile and adult periods
      - -occurs when the first clutch of eggs reaches full development in the ovary
      - -after molting, the individual is an adult
    - -the first parthenogenetic clutch of eggs is deposited into the brood chamber
    - -adult instars are the most variable in number
      - e.g. D. pulex 18-25
      - D. magna 6-22
    - -at the end of an instar 4 events occur in rapid succession(few minutes to a few hours)
      - -young are released from the brood chamber
      - -molting occurs
      - -growth
      - -a new clutch is released to the brood chamber
  - -Cyclomorphosis: seasonal changes in morphology
    - -some Daphnia develop a "helmet"
      - -most bizarre forms occur in mid summer
        -by fall, populations are back to "normal" morphology
        no single factor explanation for the phenomenon
        -shown to be temperature dependant
        e.g. higher temperatures produce greater helmet size
        -shown to be genetic
        -divergent strains cluster despite environmental changes
        
        -shown to be induced by predators
        -pop. Under heavy fish predation develop larger helmets and even tail spines
    - -cyclomorphosis is a complex phenomenon that is influenced by environmental, genetic, and predation pressure relationships
- -Vertical Migration
  - -common for limnetic (pelagic) cladocerans
    - -usually on a diel scale (daily)
      - e.g. DVM Daily Vertical Migration
    - -commonly upward at dusk, and back down at dawn
      - -amplitude of about 2 to 10 meters
Subclass Ostracoda
- -Order Podocopa - seed shrimps
  - -although abundant and widely distributed, there have been relatively few studies on ostracods
  - -they occur in lentic and lotic environments
    - -on rooted plants
    - -algal mats
    - -debris
    - -mud, sand, and rubble
    - -even in stagnant pools and underground
  - -have an opaque bivalve carapace
  - -identification to species is difficult
    - -usually involves dissection
  - -more than 300 described U.S. freshwater species
  - -to 3mm in size(carapace length)
  - -most <1mm
  - -color: chalky white to black
  - -valves may be smooth, pitted, papillate, or setose
    - -each valve has an inner and outer plate
      - -thin skin fold in-between secretes the valve material
  - -locomote using 1st and 2nd pairs of antennae
    - -also kicking of caudal rami
    - -motion ranges from creeping, to scurrying or even swimming
      - -those that swim typically have plumose (i.e. hairy, many setae) antennae
    - -Cypridopsis vidua moved more, and swum higher off the bottom, in the presence of crayfish odor
  - -Ostracods eat mostly bacteria, molds, algae and fine detritus
    - i.e. they are omnivorous scavengers
  - -respiration occurs over general body surfaces
  - -ostracods have a hemocoel, but no heart has every been described for a freshwater species
  - -reproduction is species specific
    - e.g. parthenogenetic only in species Candona
    - e.g. parthenogenesis + sex in species Cypridopsis
    - e.g. sex usual in species Candona, Cyprois
  - -most ostracods are oviparous
    - -lay spherical eggs
      - -double walled
      - -layed singly or in clumps, or in rows on
        -rocks
        -twigs (or other aquatic vegetation)
        -debris
      - -eggs remain viable after drying
        -up to 20 years (Pennak, 1989)
      - -eggs hatch in a few days to several months later
    - -ostracod larva is called a nauplius
      - -the adult occurs at the ninth instar
        -sexual maturity
      - -usual life span is several weeks to 7 or 8 months
      - -single generation per year common, but a few species have 2-3 per year
Subclass Copepoda
- -more than 10,000 described species
  - -most of these are marine
  - -yet still an important freshwater group
  - -almost universally distributed in the plankton, and the benthic and littoral regions of freshwaters
- -Order Eucopepoda - copepods
  - -planktonic, benthic, or parasitic
  - e.g. Lernaea
- -Order Branchiura - fish lice
- -Body segmentation is easily seen in most copepods
  - -each segment is a sclerotized cylinder that has loose attachments to adjacent cylinders
- -most copepods are less than 2.0mm (range from 0.3 to 3.2mm)
- -fusion of body segments is species dependant
  - -body is divided into head, thorax, and abdomen
    - -head and some thoracic segments are fused and form a cephalothorax
      - -this in turn, is covered with a carapace
- -the body has one particularly flexible articulation
  - -anterior to the joint is the metasome
  - -posterior is the urosome
    - -urosome has all the abdominal segments, plus one or two thoracic
- -head has five pairs of appendages
- -next five thoracic segments each have a pair of swimming legs
  - -swimming legs are biramous
    - -basipod, exopod, and endopod
- -there are no abdominal appendages
- -Reproduction
  - -both parthenogenetic and sexual
    - -varies with species and environmental conditions
  - -generation time ranges from one to several per year
  - -the antennae of males (and modified 5th legs) are used to clasp females
    - -males usually clasp and mate with a female after she has her final molt (when she reaches adulthood)
    - -clasping lasts from a few minutes to several days (up to 10!)
    - -male transfers sperm to the female while clasping
      - -passes sperm packets, spermatophores to her genital pore
        -she then stores the sperm in her genital segment
  - -fertilization occurs later
    - -few minutes to two months later
    - -occurs as eggs travel to the ovisacs
      - -ovisacs are attached to the genital segment
        -each contains 5-40 eggs(developing zygotes)
      - -incubation (for some copepods, e.g. cyclocpoids) ranges from twelve hours to 5 days
  - -larval copepods are called nauplii (nauplius=singular)
    - -start life with 2 pairs of antennae and the mandibular appendages
      - -others come later
      - -nauplius for six molts
      - -copepodid for 5-7 molts
      - -adult
P30 Hemiptera Odonata Ephemeroptera Diptera Trichoptera Coleptera Plecoptera
Mosquitoes
Order Diptera; Family Culicidae
- -Mosquitoes are prominent freshwater organisms
  - -great annoyance to humans
  - -females bite, some species by day, others by night
  - -vectors of disease
    - -malaria
    - -yellow fever
    - -encephalitis
  - -great swarms can be produced, even from small bodies of water
    - -breed in varied locations and habitats
      - e.g. freshwater, salt marshes, stagnant water, reservoirs, tin cans, stock tanks, tree holes, hoof prints, etc.
- -with few exceptions, mosquitoes are small
  - -3-6mm in body length
    - -fragile
- -they have mouth parts formed for piercing and bloodsucking in females
  - -males often feed on nector from flowers or on other plant liquids
- -gender is easily identified in most mosquitoes
  - -antennae
    - -males have plumose(hairy) antennae
    - -females have few hairs by comparison
  - -larvae of all mosquitoes, without exception, are aquatic
- Life History
  - -Mosquitoes go through a life history consisting of egg, larvae, pupa, and adult
    - -eggs are deposited singly or in rafts
      - e.g. Culex - raft; Anopheles - single floating eggs
    - -some eggs are deposited in the ground
      - -along the edges of depressions
      - -may survive desiccation for several years
      - -hatch upon re-flooding of the depression
    - -incubation lasts several days to years
      - e.g. Aedes dried eggs - several years
    - -larvae molt 4 times
    - -duration of the larval stage is temperature dependant, but about 7 days is average under optimal conditions
      - e.g. Culex
    - -at the 4th molt the pupa or "tumbler" appears
    - -non-feeding stage
    - -now has a cephalothorax with breathing "trumpets"
      - -quiescent stage for most insects
        -mosquitoes are unusual in that pupae move
        -if disturbed, they tumble toward the bottom and rise after a few moments
    - -papae usually last only 2 to 3 days
      - -metamorphose into adults
    - -zoophilous: animal feeding; anthrophilous: human feeding

Spearman Rank Correlation (A Non-parametric Simple Linear Correlation) -Hypothetical Data:

X	Rank	Y	Rank	di	di^2
15.3	2.5	20.0	1.5	1	1
16.0	6.0	20.3	3.0	3	9
15.8	4.0	21.0	5.0	-1	1
15.2	1.0	20.9	4.0	-3	9
15.3	2.5	23.1	6.0	-3.5	12.25
15.9	5.0	20.0	1.5	3.5	12.25
					Sum of di^2=44.50

X: Distance from lake(meters)

Y: Parameter

di: difference between the ranks (rank X - rank Y)

di^2: difference between the ranks squared

Ho: There is a significant positive correlation or no correlation between the distance from the lake and the color rank

Ha: There is a significant negative correlation between the distance from the lake and the color rank.

-if the absolute value of Rs calc is greater than Rs crit, reject Ho
-where
- Rs=1- (6 (sum of di^2)/(n^3-n))
- Rs=1-((6*44.5)/(6^3-6))
- Rs=1-(267/216-6)
- Rs=1-(267/210)
- Rs=1-1.2714
- Rs=-0.2714 (without ties)

With ties

Rs= {(n^3-n)/6 - (sum of di^2) - (sum of Tx) - (sum of Ty)} / square root{(n^3-n)/6 -2 (sum of Tx)}{(n^3-n)/6-2 (sum of Ty)}

Where Sum of Tx = (sum of(Ti^3-Ti)/12) and the sum of Ty=(sum of(Ti^3-Ti)/12)

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Conditions	Productivity in grams C per m^2 per year
oligotrophic	7-25gC/m^2/yr
mesotrophic	26-74gC/m^2/yr
eutrophic	75-250gC/m^2/yr
polluted lakes	350-700gC/m^2/yr

	Hypothetical Data Set
I	Xi(g)	Xi^2
1	3	9
2	5	25
3	6	36
4	9	81
5	10	100
6	11	121
7	12	144
8	12	144
9	18	324
10	19	361
Sums	105	1345

Hypothetical Data Set
Depth(cm):X	X^2	Biomass(g):Y	Y^2	XY
95	9025	100	10000	9500
190	36100	200	40000	38000
310	96100	305	93025	94550
400	160000	380	144400	152000

Degrees C	28	18	8
average life span(days)	26	42	108