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The Global Water Cycle
28 January 2016

11:33

• The global water cycle is the sum of lots of variation
• Precipitation
○ Evaporation minus precipitation
○ Seasonal variation in precipitation
• The global water cycle is driven by the sun
○ Affected by the Earth's orbit and tilt
○ Milankovitch cycles
• Interactions with geology, vegetation, glaciation, animals, humans, etc
...
springer
...
1007/978-1
-4020-8259-7_61
#page-1

Impeded flow
Retainment
Residence time 1-103 days
Hole in the earth with standing water
Pond
○ Light throughout
○ Rooted plants
Lake
○ Aphotic zone without rooted plants
Change over time
Type and ecology
○ Catchment
○ Location
○ Humans
○ Size and shape
8 classifications

○

○ Dimictic
 Only mix 2 time a year
○ Discontinuous cold polymictic
 Mix at different times during the year, can be dimictic
○ Continuous cold polymictic
○ Discontinuous and dimictic stratify
Origins
• 4 general
• Tectonic
○ Major plate movements
○ Big and deep
○ Rift lakes - Lake Baikal
○ Seafloor uplift - Caspian Sea
○ Crustal warping - Lake Victoria
• Volcanic
○ Flooded craters, calderas
Crater Lake, Oregon - 50km2, 593m deep
Freshwater Biology Page 3

○ Crater Lake, Oregon - 50km2, 593m deep
○ Nicaraguan Crater Lakes - isolated cichlids
• Glacial
○ Scouring, damming, periglacial
○ Ribbon lakes
○ Continental depression - Great Lakes
○ Scour lakes - long, narrow, deep
○ Moraine dam lakes - glacial deposits dam rivers
○ Cirque lakes - glacial tarns
○ Kettle lakes - kettle holes, embedded ice melts
• Other
○ Karst lakes
 Percolating water dissolves limestone and it collapses
 Sinkholes
○ Oxbow lakes
 Meander pinched off
○ Animal lakes
 Beaver dams
 Dug wallows
 Reservoirs - dammed rivers, flooded valleys
Fate of Lakes
• Ephemeral
• Deposition
○ Flow from rivers or land
○ 0
...
) M > F > T
• Eukaryotes M>>F
• 37 phyla in FW, 58 in Marine (17 exclusive)
○ None exclusively FW
• Freshwater habitats are much smaller
○ 0
...

○ Crustacea
 Branchiopods
□ Shrimp and cladocera (daphnia)
□ Plankton and detritivores
 Ostracoda
□ Seed shrimp
 Omnivores
□ Copepods
□ Malacostraca
 Amphipods, isopods, decapods (crayfish, crabs)
○ Fish
 Actinopterygii
 Petromyozontiformes (lampreys)
 Sarcopterygii
• Marine and Terrestrial Origins
○ Mollusca
 Bivalves - marine
 Gastropods - terrestrial and marine
○ May have terrestrial parts of life-cycle
 Terrestrial stages = reduced isolation
 Insects with flying adult form - hemimetabolous
 Genetic flow
• Phyla of Terrestrial Origins
○ Insecta
 EPT
□ Ephemeroptera, plecoptera, tricoptera
 Diptera
 Coleoptera
 Neuroptera
○ Arachnae
 1 British species

Freshwater Biology Page 5

Adaptations to Freshwater
29 January 2016

13:53

• Highly variable
○ Hot springs
○ Seasonal ponds
○ Antarctic streams and ponds
○ Mud and sediments
○ Varied contents - salinity pH etc
...
0 H2O permeability
□ Eriocheir 0
...
g
...
6ppm
□ 25oC 8
...

○ Salinity alters temperature/density relationship
○ Max density at lower temperatures
○ Higher salinity = denser
...
density at lower temperature
...
g
...
055mg/cm2/d - eutrophic
○ Minimum hypolimnetic O2 depends on productivity and hypolimnion volume

Freshwater Biology Page 18

Freshwater Biology Page 19

Biogeochemical Cycles
05 February 2016

13:13

Nutrients in Freshwater
• Sources
○ Inflow
 Catchment area important
 Prolonged exposure to acid rain leaches nutrients
 Farming and urban areas may release high volume of nutrients
□ Eutrophication
 Rock weathering
 Sediments
 Anthropogenic (>50%)

Ions
• Soluble inorganic matter
• Major ions present:
○ Ca2+, Na+, Mg2+, K+
○ HCO3-, SO42-, Cl• Levels dependent availability
○ e
...
runoff
○ Concentrations can vary by huge degrees
• Conductivity
○ Dependent on ions present
○ Increases with ion concentration
 Can use to estimate
○ Temperature dependent (measured at 25oC)
Macronutrients, Micronutrients, and Bacterial Food Sources
Macronutrients

Micronutrients

Growth factors

Carbon (C)

Chromium (Cr)

Vitamins

Hydrogen (H)

Cobalt (Co)

Amino acids

Oxygen (O)

Copper (Cu)

Purines

Nitrogen (N)

Manganese (Mn)

Pyrimidines

Phosphorus (P) Molybdenum (Mo)

Sulphur (S)

Nickel (Ni)

Potassium (K)

Selenium (Se)

Magnesium (Mg)

Tungsten (W)

Calcium (Ca)

Vanadium (V)

Silicon (Si)*

Zinc (Zn)

Iron (Fe)

Freshwater Biology Page 20

From
...
co
...
2-2 micrometres
• 20 minute generations
○ Or resting for centuries
• Bacteria are major contributors to phenotypic, genetic, and molecular diversity
• Main aquatic heterotrophs
○ 105/ml of freshwater
• Diverse roles in lake ecosystem
○ Planktonic
○ Benthic biofilms

Important roles
• CO2 fixation
○ Photoautotrophs
○ Chemoautotrophs
 Boundary layer between aerobic and anaerobic
○ Heterotrophs carry out most CO2 fixation under dark conditions
• Nitrogen fixation
○ Nitrogenase enzyme
○ Combine N2 with H into useful nitrogen, e
...
ammonia
• Majority heterotrophic
○ Key component in microbial loop, recycling
○ Outcompete algae for N and P under limiting conditions
○ Often first colonisers of benthic habitats
Bacterial Identification
• Only some grow in a lab medium
• Epifluorescent technique
• Molecular techniques
The Microbial Loop
• Classical aquatic food chain
• Limitations may be bottom up (nutrient availability) or top down (predation)

Freshwater Biology Page 28

Dormancy
• Bacteria may be present in inactive form
○ Still get counted
• Low O2
• Low nutrient
• Low light
Bacterial Counts
• Viable and non-viable
• Viable in epilimnion, high DOC
• High levels of non-viable bacteria account for main count in hypolimnion

Bacterial Growth Efficiency

• Early studies suggested 50% in photic zone
○ Very high
• Recent studies show <10-25%
Freshwater Biology Page 29

• Recent studies show <10-25%
• Closely linked with phytoplankton productivity
○ In photic ~20%
○ Below photic zone is linked to C content of sediment
• Bacterial productivity is higher in eutrophic lakes
Out of Control Bacteria
• Cyanobacteria
• Cyanotoxins
• Efficient light harvesting
• High CO2, low pH
• Resistant to radiation
• Extreme temperatures
• Some fix N, can grow in low nutrient conditions
• Buoyancy mechanisms
• Resistant to removal by filter feeding zooplankton
Phytoplankton and Bacteria
• Antagonistic interaction
○ Phytoplankton
 Production of acrylic acid
 Antibiotic production
○ Bacteria
 Algal lysing by antimicrobial compounds
 Parasitic/predators
 Epiphytic effects
○ Bacterial competition is most limiting when nutrients are limited, but C is not
 Allochthonous
• Bacteria breakdown DOM, make N and P available to phytoplankton
• Phytoplankton increase DOC available to bacteria
• Cooperation?
○ Epiphyte interaction may be beneficial for both parties

Freshwater Biology Page 30

• Bacteria play a key role in the breakdown of POM and DOM in lakes
• In humic lakes bacteria dominate where phytoplankton are prevented from flourishing
• They are competitive with phytoplankton and toxic blooms may be harmful to other aquatic
life

Freshwater Biology Page 31

Phytoplankton Introduction
12 February 2016

12:58

• Many not true plants
• Green algae
○ Paraphyletic groups
○ Sometimes grouped with true plants
•
•
•
•

small - usually microscopic
Eukaryotic
Freshwater and marine
Highly diverse
○ Nutrient requirements
○ Life strategies
○ Seasonal variation
○ Lake type
• Found globally
• Diversity and variability suit them to every environment
○ Chlamydomonas grows in snow

Survival Features
• Positioning
○ Buoyancy
 Oil droplets
 Air filled vacuoles
○ Flagella
 Motility
○ Phototaxis
 Movement to the surface in daylight
○ Small size
 SA:V
 Drag
 Projections
• Sinking
○ Low energy cost water movement
○ Prevents microzone development
• Mixotrophy
○ Switch between heterotrophy and autotrophy, or both at once
• Dormancy
○ Can survive desiccation for long periods
Variable Growth Forms
• General structure
○ Unicellular
○ Colonial
○ Filamentous
• Cell walls
○ Cellulose
○ Pectins
○ Minerals
• Flagella
○ Insertion, length, fine structure
Timing
• Follow lake cycles
Freshwater Biology Page 32

• Follow lake cycles
• Small blobs first
○ R selected
 Fast growth
 Short life cycle
○ Low SAO:V
 Rapid nutrient uptake

• Diatoms
○ Important in freshwaters
 Bioindicators
○ Planktonic and attached
 Dominant algae in biofilms
○ Unicellular or colonial
○ Cell wall (frustule) almost entirely composed of silica
○ Centric diatoms (radial symmetry, typically planktonic) or pennate (bilateral, many
benthic)
○ Reproduction
 2 valves separate
 Hypotheca have progressive size decrease
 Sexual reproduction restores original size
• Silicon becomes limiting and bloom dies off
• Cryptomonads
○ R selected
○ Accessory pigments
 Vary in colour
○ Unicellular
○ Starch storage in cytoplasm
○ 2 unequal flagella
○ No cell walls
• Green algae/chlorophyta
○ Diverse class of algae
○ >250 UK genera
○ Planktonic and attached forms
○ Unicellular and complex colonies
○ Some macroscopic members look like macrophytes
○ Grass green chloroplast and starch reaction (in chloroplasts)
• Chlamydomonas
○ Eye spots
○ Very basic photoreceptors
○ Phototaxis
• Yellow-green Algae
○ Diverse group in wide range of habitats
○ Many are small coccoid forms
• Nutrients become generally limiting in the epilimnion
• Blue-Green Algae
○ Cyanobacteria
Not algae
Freshwater Biology Page 33

•

•

•
•

○ Not algae
○ Prokaryote
○ Fix their own nitrogen
Dinoflagellates
○ Relatively infrequent
○ Large
○ K selected
 Slow, long
 Low reproduction rates
○ All with 2 flagella
 High motility
○ Walls firm or plated cellulose
Chrysophyceae (Golden Algae)
○ Unicellular/simple colonial
○ Planktonic
○ Golden
○ Mixotrophic
○ One or 2 flagella
○ Naked or enveloped
○ Oil storage
Autumnal mixing makes nutrients/silicon available
○ New small bloom of diatoms and green algae
Euglenids
○ Specialist
○ Standing and nutrient rich water
 Sewage
○ Microscopic
○ Flagella
○ Phagotrophic
○ No cell wall - protein strips for form

Location

• Different regions due to different requirements
Seasonal Lake Variation
• Seasonal light and temperature conditions
• Changing growth conditions and stratification
• Primary productions depends on
○ Temperature
○ Light
○ Nutrients

Freshwater Biology Page 34

Seasonality and Competition
16 February 2016

10:52

Temperate Zone Succession
• Winter
○ Small flagellates adapted to low light and temperature
• Spring-summer
○ Burst of diatom activity and biomass
○ Followed rapidly by smaller green algae development
• Summer-Autumn
○ Increases in N-fixing cyanobacteria in eutrophic lakes
○ Another diatom development in less productive lakes by late summer/early autumn
Succession
• Seasonally differs in temperate vs
...
Rapid uptake
 At high nutrient availability A may outcompete B
...


Freshwater Biology Page 36

• Phosphorous
○ P/Si increases, cyclotella wins
○ P/Si decreases, Asterionella wins

• Diatom vs Cyanobacteria
○ Cyanobacteria fix their own N
 Outcompete diatoms at low N
○ High P requirements for cyanobacteria
 50C:10N:1P vs 106C:16N:1N
• Nutrient Availability
○ Supply vs uptake
○ Rapid nutrient sequestering prevents outcompetition
○ r-selected vs
...
Facultative/obligatory C source
...
Organisms or POM
...

 Raptorial feeders select and seize prey
...
Facultative
...
g
...

○ Micro-aerophilic ciliate
○ Low O2 concentration (too much is damaging)
○ Careful sampling of whole water column (metalimnion)

• Paramecium bursaria
○ Ciliate has mutualistic symbiosis with Zoochlorella
○ Algae provide food
○ Ciliate provides movement and protection
○ Some ciliates are green while they digest ingested phytoplankton - not mutualistic
• Roles of protozoa
○ In the microbial loop, bacteria are consumed by protozoa, which are in turn consumed
by zooplankton
○ Links between organic debris and higher organisms
○ Top-down control of algal populations and bacteria
○ Recycle organic nutrients

Viruses
• Femtoplankton
○ DOC
• Non-cellular
• 2 main states
○ Free infective - not alive
○ Intracellular viruses within hosts
• Viral Counts
○ Bergh et al
...
2-2mm
○ Bivalved carapace
○ Compound eye and ocellus
○ Enclosed thoracic limbs
○ Abdomen with hook
○ Broad pouch

• Reproduction

• Feeding
○ Water drawn between valves
○ Particles collected on setae
 1-50mm
○ Some predatory
 Leptodora
• Locomotion
○ 2nd antennae

Freshwater Biology Page 44

Planktonic Rotifera
• Multicellular
• <0
...
2-20mm) presence decreases phytoplankton abundance

○ Daphnia in unsieved mesocosms prevents large response to enrichment in
phytoplankton

○

○ Less impact in non-enriched environments
○ Increasing nutrients available to phytoplankton increases zooplankton
Drop in phytoplankton due to increases in copepods

Freshwater Biology Page 47

○ Drop in phytoplankton due to increases in copepods
 Delay cycling
 Lynx/hare
○ Evidence for bottom up
 Zooplankton abundance impacts phytoplankton abundance
 Strong herbivory impact
 Adding nutrients that benefit phytoplankton increases zooplankton abundance
○ Zooplankton and planktivores
 Planktivores
□ e
...
copepods, insect larvae, white fish, fish fry
 Impact on population growth

Nt = N0ert
 R = growth rate
 B = fraction reproducing, brood size
• Behavioural Responses
○ DVM - Diurnal vertical migration
 Visual predation by fish (and some invertebrates)
 Physiological - avoid UV damage
 Dispersal
 Food availability

 Differs depending on light availability in the lake
□ Turbidity and humic levels effect daytime depth
• Morphological responses
○ Cyclomorphis in multivoltine (multiple annual generations) zooplankton
 Induced morphologies in response to predation threat

Freshwater Biology Page 48

 Also increased substrate attachment

○ Also plasticity in other traits
 Dependent on source population and fish kairomon exposure
○ Alternate hypothesis
 Reduction in sinking
 Swimming ability - antennal muscle
 Gas exchange SA

○

Freshwater Biology Page 49

 Size efficiency hypothesis
□ Brooks and Dodson
□ Large grazers outcompete small
 Food particle size range
 Collection efficiency
 Metabolic efficiency
□ Vertebrate predators size selective
 Detection
 Energy return

□

□

Freshwater Biology Page 50

Aquatic Macrophytes
25 February 2016

11:49

Why Be Aquatic?
• Not dependent on climate for water supply
• Viscosity gives support
○ Fast growth
○ Rainforest 2500kgCm-2y-1
○ Macrophyte 3750kgCm-2y-1
Classification
• Charophyta
○ Macroalgae
• Bryophyta
○ Mosses
○ Liverwort
• Angiosperms
○ Flowering plants
• Functional Classification
○ Based on attachment and growth form
○ Submerged rooted
○ Submerged unrooted
○ Floating unattached
○ Floating attached
○ Emergent
Lotic (flowing water) macrophytes
• Few adaptations
• Mostly slow currents
• Tough, flexible stems and leaves
• Attachment by roots, rhizomes, and stolons
○ Stolon = modified horizontal stalks at or above sediment surface
○ Rhizome = modified horizontal or vertical stalks below sediment surface
• Vegetative reproduction typical
Longitudinal Succession in Slower Currents
• Harder water, lower shear stress
• Bryophytes decline
• Angiosperms establish
○ Ranunculos sp
...

• Slowest sections
○ Emergent and floating leaved plants

Freshwater Biology Page 51

Factors Affecting Development
• Depth

○ Fewer species with depth
• Light
○ Photosynthesis
○ Requirements vary
 Angiosperm 13% > Charophytes 5% > bryophytes 2%
○ Maximum depth of angiosperms typically <12m
○ Bryophytes >100m in clear water
• Pressure
○ Vascular macrophytes <10m (1atm)
○ Xylem and phloem vessels
○ Gas trabsport
• Nutrients
○ N and P through roots and shoots
○ Sediment vs water concentrations
○ Hardness (HCO3-) may affect carbon balance
• Inorganic Carbon Utilisation
○ Adaptation to low CO2
○ Aerial leaves
○ Utilisation of CO2 in pore water of sediments
 Bacterial respiration
○ Utilisation of HCO3○ Temporal decoupling of light reaction
 Crassulacean Acid Metabolism
○ Low CO2 compensation point
• Sediment
Freshwater Biology Page 52

• Sediment
○ Texture
 Fine sand, silt, or clay
 Coarse sand, cobbles, boulders, not suitable
○ Stability
 Cannot establish on moving sediment
Emergent Macrophytes
• Sagittaria
○ Arrow Weed
• Phragmites
○ Common reed
• Typha
○ Reedmace
• Water saturated or submerged soils
• Aerial reproductive organs
• Thickened cell walls
○ Slow decomposition
• CO2 and O2 for air
• Young foliage may respire anaerobically
○ Anoxic sediments
• Nutrients can be derived from sediments via roots
Floating Leaved Rooted
• Nuphar - water lily
• Potamogeton - pondweed
• 0
...
g
...
g
...
Movement and connectivity are not like the sea
...
J
...
4-1
...


 Measured everything (except fish)

 Catchments differ in gradient, chemistry, physical habitat

 Coarse benthic organic matter decrease with increasing stream order

Freshwater Biology Page 71

 Clear switch from large amounts of coarse organic material entering the system, to primary productivity with increasing order
□ Net metabolism overall primarily heterotrophic
□ Uppermost section (1) always heterotrophic
□ Autotrophy more likely downstream than upstream (PP/R>1) but could be heterotrophic at lowest stations (PP/4<1)

□

 Invertebrate communities
 RCC vs Reality
□ "the postulated gradual change in ecosystem structure and function along a stream is supported by this study"

□ Deviations due to
1
...
Riporia vegetation
3
...
Local geomorphology (bedrock, debris, etc
...
5 cages
 No fish
 3, 6, 12 sculpins
 Open cage
○ Sculpins had some effect on invertebrate colonisation

 CPOM had more
○ Top down effects

○ 5 enclosures (3 riffle, 2 pool)
○ Bottom split- fish/no fish
○ Tiles and gravel baskets in each

○ Effects of predation on S, M, and L inverts differed between pools and riffles

 Greatest on tiles, riffle algae higher
○ Birds

Freshwater Biology Page 75

○
○
○
○
○

Steep 2nd order stream
3
...
, flow, O2)
□ Densities periodically reduces - abiotic dominated
 Benign (relatively constant conditions)
□ Competition and predation control
○ Patch dynamics view
 Shifting mosaic of conditions
 Dispersal of benthic organisms between patches
 Local variation but predictability at larger scales
○










Garden paving stones
3x2 design (and controls)
7 blocks
N=63
Intensity high/low
Area 50/100%
Frequency 1/2 per week
Disturbance reduced invertebrate abundance at high and low frequency
Disturbance increases invertebrate diversity at high and low frequency

Stream-Terrestrial Linkages

Freshwater Biology Page 76

•
•
•
•
•

2-5m wide, <1% gradient
4 treatment
30m reach
4 replicates
Control, greenhouse, rainbow trout, trout and greenhouse
○ Greenhouse and trout reduce the number of terrestrial food in native charr diet
○ Charr shift to benthic herbivores - periphyton biomass goes up, emergent aquatic insects
go down

Freshwater Biology Page 77

Fish
10 March 2016

11:09

Assemblages
• All species in a define area, whether they interact or not
• 27000 species of fish
○ 40% are freshwater (0
...
Trout Zone
○ Erosional - slopes >4
...
Grayling Zone
○ 1‰ for width up to 100m - 4
...
Barbell Zone
○ Increased tributaries, increased nutrients, and lower gradient
○ 0
...
5-3
...
Bream Zone
○ Gentle gradient, high turbidity and nutrients
○ Lower courses, high stream order, high summer temperatures
○ Fine substrate
○ Decreased O2 at depth
○ Similar to man-made waterways - canals and drains
○ Carp, tench, roach, bleak, pike, zander, perch, eels
○ Common Bream (Abramis brama)
□ Nutrient rich, slow moving rivers
□ Clay or muddy bottom
□ Tolerate low O2
□ Feed on benthic invertebrates, crustaceans, and larvae
□ Spawn in shallow May to June 12-20oC
○ Tench (Tinca tinca)
□ Spawn May to August, 18-24oC
□ Weedy shallows, adhesive eggs
□ Warm, quiet water, slow moving areas of large rivers, lakes, ponds
□ Invertivore and herbivore - strong pharyngeal teeth
○ Roach (Rutilus rutilus)
□ Frequent lowland rivers and still water, even brackish
□ Spawn during spring 14oC
□ Sticky eggs laid in shallow dense vegetation
□ Feed on algae and invertebrates
○ Gudgeon (Gobio gobio)
□ Spawn May to June on gravel and macrophytes in shallows
□ Fast flowing stream with sand/gravel, also still slow waters
□ Benthic feeders - molluscs, inverts, larvae

Freshwater Biology Page 81

Biotic Influences
11 March 2016

13:05

• Temperate streams are complex communities
• Most fish show a high degree of behavioural plasticity to avoid negative interactions
• Evolved behavioural and morphological adaptations and life history traits to suit environments
Competition
• Intraspecific competition on niche characteristics
○ Fish can be very restricted in requirements and reduce competition - specialist

○ Fish can reduce competition for special resources by being generalist

Spawning Habits of River Fish
• Low order stream
○ High O2
○ Low deposition
○ Risk of being carried downstream
○ Egg burying and guarding (trout males develop kype)
• High order
○ Variety of strategies
○ Sticky eggs for attachment
○ High fecundity - high predation risk in complex environment
○ Nest building and guarding

Migration
• Movement between widely separated and well-defined areas
Freshwater Biology Page 82

•
•
•
•
•

Movement between widely separated and well-defined areas
Distinct from local foraging or diel migrations
Cyclic, unlike dispersal
Only 1% of species (Hardin-Jones 1980)
Advantages
○ Increased feeding potential
○ Avoidance of adverse conditions e
...
weather
○ Improved reproductive success
• Costs
○ Energetic costs
○ Increased predation risk
○ Energetic and developmental cost
○ Decreased lifetime reproductive effort
• Benefits > costs to have evolved
• Diadromy (to move between)
○ Anadromy (ana = up)
 Reproduce and early growth in freshwater
 Most feeding and growth in sea
○ Catadromy (cata = down)
 Reproducion and early growth in sea
 Most feeding and growth in freshwater
○ Amphidromy
 Reproduction in freshwater
 Early feeding and growth in sea
 Most feeding and growth in freshwater
River Engineering
• Dams, sluices etc
...

○ Increased predation pressure
○ Physical damage - turbines, steep weirs, propellers
• Diadromous species
○ e
...
brown trout and salmon
○ Return to home stream, matured at sea
○ Locks, sluices, and dams may impact migration
○ Changes in temperature profile
○ Changes in seasonal pattern of water flow
• Fish passes
○ Ramps, terraces, fish lifts
○ Easier passage

Freshwater Biology Page 83

Invasive Fish Species
17 March 2016

11:02

Alien Species
"A species, subspecies, or lower taxon introduced outside its normal past or present distribution"
Invasive Alien Species
"An alien species whose establishment and spread threaten ecosystems, habitats, or species with
economic or environmental harm"
Invasive Species in the UK - Winfield, Fletcher, and James 2011
• Assessed introduced fish in Loch Lomond (Scotland), Loch Neagh (Ireland), Windermere, Llyn
Tegid
• All but Windermere contain rare whitefish of the genus Coregonus
...
lavaretus
...

○ Loch Neagh - Pollan C
...
Breed October
○ Llyn Tegid - Gwyniad C
...
Breed Jan/Feb in
shallow gravel
...
May be one species
○ Feed on benthic invertebrates
• Loch Lomond
○ Supports 15 fish species (Adams 1994)
○ Gudgeon, ruffe, dace, chub, crucian carp introduced in 1970s as live-bait
○ 1998/9 Whitefish 40% to ruffe 24%
○ 1991 64% of whitefish eggs predated by ruffe
...
001 (Winfield 2008)
• Loch Neagh
○ Commercial eel, perch, pollan fishery
○ Roach introduced in the late 19th centure, rapid increase in 1980s
○ Pollan doing ok
• Llyn Tegid
○ Single eutrophic basin
○ Local cultural eutophication (fertilisers etc
...
2010
○ Assessed the response of introduced species in UK waters and used modelling to predict
outcomes of warming on fish communities
○ 2 approaches
1
...
Modelled climate predictions for 2050 to climatch data
□ Score <7 = no constraint to reproduction
○ Results
 High Fish Invasiveness Score Kit (FISK) scores and extreme propagule pressure
assigned to carp and catfish
 38 non-native species introduced to UK
 15 have establish self-sustaining populations
 Of 6 in >100 water, 5 had FISK >19

Freshwater Biology Page 85

 Predictions for catfish
□ 3oC increase will markedly increase reproduction
□ 22oC minimum requirement
• Topmouth Gudgeon
○ Highly invasive
○ Cyprinidae, native to orient
○ Uisance species and once introduced rapidly establish and dominate numerically
○ Healthy host for intracellular fish parasite, suppresses growth of other species

Freshwater Biology Page 86

Mammals, Reptiles, and Birds
11 March 2016

13:15

• Rivers and riversides provide a variety of vertebrate niches
• Obligate riparians
○ Rely fully on river to survive
• Generalists
○ Utilise river resources and refuge but not entirely dependent
Birds
• Dipper (Cinclus cinclus)
○ Forages underwater
○ Fast flow, large cobbles, water clear - low order
○ Waterproofing by preening and spreading diester waxes from uropygial gland at base of
tail
○ Nictating membranes protect eyes when submerged
• Pied wagtail (Motacila alba)
• Grey wagtail (M
...
g
...

○ Effect: varied, including pesticides, endocrine disruptors, pharmaceuticals, anti-fouling
agents
• Radioactivity
○ Source: nuclear power and weapons
○ Effect: toxicity (chromosome damage), chronic toxicity (cancer, genetic abnormalities)
• Oil
○ Source: oil spills, industry leakage, motor vehicles
○ Effect: physical (suffocation, blocking light, clogged limbs), water soluble components
toxic
Changes To River Courses
• Longitudinal fragmentation (dams)
• Lateral fragmentation (connection with surrounding flood plain)
• Changes to riparian zone
• Flow modification
Tackling
Freshwater Biology Page 89

Tackling
• Catchments important
• Land use strongly influences lakes and river
• Very interconnected
○ Pollution from factory in one area will prevent salmon spawning upriver, less nutrient
input from salmon corpses
• Human population increasing, land use will change
• Policy for Protection: The Water Framework Directive101 1992
○ Natura 2000 meeting
○ Habitats maintained or, where appropriate, restored at a favourable conservation status
○ Maintenance of biodiversity
○ "water is not a commercial product, … but a heritage which must be protected"
○ Delivered at water body scale
 Coherent subunit
○ The "good status" challenge
 Good surface water chemical status - meet environmental objectives
 Ecological status expression of quality and functioning of aquatic ecosystem
○ "One out all out"
 Lowest classified element = final classification
○ ~1000 surface water bodies in Wales
 67% below "good status"
 Reasons: rural agriculture, barriers, mining, forestry, pH, sewage, reservoirs

Freshwater Biology Page 90

Organics
15 April 2016

13:00

• Organically enriched effluent
○ Domestic
 Mainly faecal
○ Industrial
 Brewing
 Food processing
 Papermaking
 Abattoirs
 Livestock
 Silage
○ Rainwater drainage
 17gm-2y-1 dog faeces
 Rubbish tips
○ Organic material from farm land (fertiliser mostly)
Nitrogen From Anthropogenic Sources
• Millions of tonnes per year
• Reactive nitrogen
• Fossil fuels
• Natural
• Industry
• Haber Bosch N fertiliser
• Cultivated BNF (biological nitrogen fixers)
• Effects

Effects
• Turbidity/sedimentation
○ Affects light and substratum
○ Turbidity = phytoplankton - Lake Tåkern, Sweden, shade, cyprinid fish
○ Clear = macrophytes, stabilise sediment, piscivores and herbivores
• Algal nutrient source
• Microbial energy source
○ Sphaerotilus uses O2 and blooms in N rich areas
High Nutrient Conditions
• Hyp/anoxic
• Eutrophic
• Stratified and productive
BOD

•
•
•
•

Biological Oxygen Demand
Amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present
High BOD = low O2 saturation
Dissolved Oxygen Deficit (DOD) is the difference between the amount of oxygen that "should" be in the water vs
...
aber
...
uk/bbcswebdav/pid-726037-dt-content-rid-1073001_1/courses/BR22020_AB0_
2015-16/Thames%20estuary
...
25mn/y)

Case Study: Eutrophication of Lake Washington
• Lake Washington is a monomictic lake in Seattle (one mixing during year, cooling during winter, otherwise
stratified)
• Residence time ~3 years
• Seattle population 300 in 1865 to 1
...
3m by 1955 - Oscillatoria cyanobacteria
○ Daphnia replaced by Diaptomus (Daphnia breathing apparatus blocked by Oscillatoria)
• Switch in primary producers
○ Cyanobacteria can fix their own N
○ High P demand supplied by influx
• Changes for the better
○ Sewage diversion from 1963 - no more effluent after 1968
○ In 1962 72% of P was from sewage
○ By 1967 P input down to 26%
○ Mid 70s Daphnia returned - Secchi depth to 12 metres (Daphnia grazing)
Treatment Effective but Costly

• Primary treatment
○ Screening

Freshwater Biology Page 92

○ Screening
○ Settlement
• Secondary treatment
○ Trickling filter
 Bacteria, fungi, protists, rotifers, nematodes, oligochaetes, diptera, coleoptera)
○ Activated sludge
 Bacteria, protists
• Tertiary treatment
○ Nitrification (NH 2 to NO32-) and denitrification (NO 32- to N2)
○ Phosphate removal (chemical stripping)

Freshwater Biology Page 93

Metal Pollution
21 April 2016

11:01

Sources

•
•
•
•
•
•
•
•
•

Domestic waste water
Manufacturing
Atmospheric fallout (Pb before unleaded petrol)
Copper pipes
Selenium from power plants
Sewage
Dumping
Leaks
Mines (ceredigion)
○ Metals stored in sediments for a long time
○ Slag heaps
○ Water run through and leaching
○ Localised but large impact
○ Ceased in ceredigion in 1900
 Lead poisoned cattle 2012
 Lead in clarach
○ Flood and channel sediment many above safe
 More floods happening

Heavy Metals
• Arsenic, lead, mercury
• Now any metal that can cause harm at low concentrations
○ Hg, Cd, As, Cr, Th, Pb
• Some necessary as traces, but toxic at high levels
○ Cu, Zn, Se
Effects

Freshwater Biology Page 94

• Optimal range of light metals
○ Up to toxic down to deficit
• Heavy metals tolerable
○ Toxic
○ Lethal at highest

Measuring
• LC50
○
○
• LT50
○
○
• EC50
○
○
• HC50
○
○

Lethal concentration
50% dead within time
Lethal time
50% dead at concentration
Sub-lethal effect seen
50% show effect at concentration
Any environmental impact
50% show at concentration

Factors
• Species highly variable
• Population variability (adaptation)
• Size (SA:V) and developmental stage
• Environment (temp
...
2002
• Water hardness effecs toxicity and bioavailability of some metals
○ Criteria for Ce, Cu, Pb, Zn modified

Freshwater Biology Page 95

○

• Recorded diatom and macroinvertebrate species and abundance at 51 sites
• Overall increased metal concentration leads to a decline in diversity, richness, abundance of macroinvertebrates,
but an increase in evenness - less dominance
• No reduction in diatom diversity or richness, but altered species composition
Bioaccumulation
• Accumulation via
○ Respiration
○ Adsorption across membranes
○ Ingestion of contaminated food

Mercury in Lake Päijänne varies at trophic levels

• Not all metals bioaccumulate
○ Different mechanisms to remove
○ Metallothioneins bind heavy metals
Impact of Environment
• Lower pH = more metals in solution, more toxicity
• Increased hardness can incrase pH
• Calcium may block metal uptake
Differences Across Species
• Varying calcium and heavy metal uptake
• Sensitive species uptaking more
• Adaptation - Salmo trutta in Cornwall
Hayle river vs less contaminated Teign
Freshwater Biology Page 96

○ Hayle river vs less contaminated Teign
○ Fish in Hayle surviving contamination that would kill in Teign
• Snails in Canada
○ Behavioural avoidance of contamination
Responses
• WFD
• Environmental quality standards to protect aquatic life from exposure via water column, through food chain, and
from contaminated sediments

•
•
•
•

Identify catchments potentially impacted
Assess extent and magnitude of contamination
Carry out risk assessments
Develop and implement monitoring and remediation programmes

• Most measures very expensive
○ Liming
 Add CaCO3 and other alkaline material to raise pH
○ Bonemeal
 Insolubl metal phosphates form
○ Iron oxides
 Induce sorption of metal contaminants on iron hydroxide surfaces
 Electrokinetic generation of iron-rich barriers
□ Sub-surface barriers
○ Phytoextraction
 Use of plants to uptake contaminants

Freshwater Biology Page 97

Acidification
21 April 2016

11:24

Acid Rain
• Statues and buildings dissolved - recognised as acidity of rain 1660s by John Evelyn
• Rain pH ~5
...
3, as low as 2
...
g
...
5
 Increased food availability
 Macrophyte growth - shelter for juveniles
 Reduced inorganic nonorganic aluminium

Leaching
• Increased ion leaching from surroundings
• Toxins, heavy metals, mining
• Reduction in ions surrounding lakes
• Increased solubility with low pH
• Neutralising capacity CaCO3 reduces metal ions in blood/haemolymph
Freshwater Biology Page 98

• Neutralising capacity CaCO3 reduces metal ions in blood/haemolymph
• Non-toxic metals - Mg, Ca
○ Decline of Ca in freshwater systems in north America
○ Leached out of catchment
○ Net loss of available Ca
○ Decreased crayfish survival - Edwards et al
...
2016)

Case Study 1: Invasive Signal Crayfish Pacifastacus leniusculus
• Largest freshwater invertebrates in most systems

Freshwater Biology Page 100

• Largest freshwater invertebrates in most systems
• Keystone species in lotic and lentic environments
• Negative impacts on macrophyte growth
○ Direct consumption/destruction
○ Reduced grazers = more shading periphyta
○ Increased turbidity - sediment disturbance
• Negative impacts on benthic inverts
○ Snails
○ Consumption
○ Habitat destruction
• Negative impacts on fish and amphibians
○ Direct consumption
○ Loss of habitat
○ Competition for prey
• Impacts on native crayfish
○ Not clear cut but tendency to negative
○ Direct effects of consumption
○ Resource competition
○ Disease carriers - main impact
• Benefits of crayfish removed - citizen science, CA, USA
○ Increased overall abundance
○ Changed community structure - relative abundance altered
○ Enhanced functional diversity of other invertebrates

Case Study 2: Topmouth Gudgeon Pseudorasbora parva
• Asian species
• Small, fast growing, early and rapid reproduction
• Highly tolerant of poor conditions
• High density
• Category 5 species (greatest risk) Import of Live Fish Act 1980
• Broad diet - competes with many fish
• Preys on fish eggs
• Carries parasites to which native species are susceptible
• Gozlan et al 2005
○ Total inhibition of sunbleak spawning, loss of condition, death
○ Pathogen transmitted by topmouth
○ Local sunbleak extinction
• Mass Topmouth Gudgeon Eradication in British Waters
○ Remove as many other species as possible
 Tench Tinca tinca
 Roach Rutilus rutilus
 Carp Cyprinidae
○ Piscicide - Rotenone 2

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Title: Freshwater Biology
Description: Notes from the 2nd year 20 credit Freshwater Biology module at Aberystwyth University, taught by Sarah Dalesman. This module covers all scales, including rivers, tributaries, invertebrate diversity, macrophytes, phyto and zooplankton, mixotrophy, and biogeochemical cycles.

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