Lytic systems Flashcards
Physiochemical properties of water
High freezing and boiling temperature.
Polar covalent bonds within water molecule and intermolecular hydrogen bonds. Hydrogen bonds most closely associated at 4 ˚C, so liquid water denser than ice.
Ice can form barrier between air and water
Water retains heat well – releases heat in winter
Universal solvent for important inorganic molecules
Transport and reaction system; essential for cellular life
Physiochemical properties of water
High freezing and boiling temperature.
Polar covalent bonds within water molecule and intermolecular hydrogen bonds. Hydrogen bonds most closely associated at 4 ˚C, so liquid water denser than ice.
Ice can form barrier between air and water
Water retains heat well – releases heat in winter
Universal solvent for important inorganic molecules
Transport and reaction system; essential for cellular life
Freshwater
High turnover rate - divided and small
Low accumulation of salt as there is liquid outflow
Low species diversity as shorter time scale and more disrpution
Salt water
Low turnover rate
High accumulation of salt due to evaporation
High species diversity due to longer time scale and less disruption
Typical salt conc in fresh vs salt water
Continuity in lakes in Malawi
Lake Chilwra - shallow, fires out, limited biota, generalists, productive and important for fishery but alkaline at low levels so unstable
Lake Malawi - deep, doesn’t dry out, many endemic species of fish
UK rivers
Easter rivers of England more recently connected to continental Europe (due to glacial periods). Silver bream are fish found in most of continental Europe but only present in the UK in SE England
Ireland and Scotland were separated earlier - dominated by euryhaline and diadramous species. Some fish e.g. arctic charr can be either landlocked (Lake District) or move from sea to lake to spawn.
Freshwater composition
CO2 dissolves to form carbonic acid; rainwater pH about 5.6
SO2 can also dissolve further reducing the pH
Buffering capacity affected by underlying geology. Igneous rock (e.g. granite, basalt) – low buffering capacity. Sedimentary rock (e.g. limestone, sandstone) high buffering capacity.
Calcium needed for exoskeleton of molluscs/crustaceans – only present when enough Ca present (e.g. Asellus waterlouse)
Weathering supplies most of Ca, Mg, Na, K and P
Most N from fixation from air (cyanobacteria)
S from rain, snow, dry deposition
P usually limiting for plant growth
N can be limiting; abundance depends on nitrogen cycling, fixation, anthropogenic sources
Nutrient availability affects primary production
Further effects higher up the food chain through trophic cascading
Freshwater
High turnover rate - divided and small
Low accumulation of salt as there is liquid outflow
Low species diversity as shorter time scale and more disrpution
Salt water
Low turnover rate
High accumulation of salt due to evaporation
High species diversity due to longer time scale and less disruption
Typical salt conc in fresh vs salt water
How does agriculture affect freshwater composition?
Vegetation clearance, slurry from livestock, fertiliser loss
How do settlements affect freshwater composition?
Sewage – high organic matter leading to high BOD (Biochemical Oxygen Demand), increases in phosphate levels from domestic detergents (EU ban on dishwasher and laundry detergents from 2017
How does industry affect freshwater composition?
more regulations now e.g. heavy metal pollution controlled, organic pollutants e.g. hormones and hormone analogues (plastic industry, some herbicides etc.)
Oxygen solubility
Inversely related to temp
Eutrophication
Increase PP due to increased levels of nutrients
Oligotrophy
Upland, igneous rocks, upper part of catchment
Eutrophy
Lowland, sedimentary rocks, catchment increases downstream and eutophy increases with age
How does agriculture affect freshwater composition?
- Vegetation clearance, slurry from livestock, fertiliser loss
How do settlements affect freshwater composition?
- Sewage – high organic matter leading to high BOD (Biochemical Oxygen Demand), increases in phosphate levels from domestic detergents (EU ban on dishwasher and laundry detergents from 2017
Hypolimnion
Bottom layer of a water-column
Oxygen solubility
Inversely related to temp
Lotic
Flowing water
Unidirectional current
Variable size
Well mixed, isothermal circulation
Currents are eroding, leading to high amounts of suspended material
Allochthonous sources of organic matter - produced outside system
Lentic
Still water
Variable but slow current
Variable but can be deeper/wider size
Deep lakes show thermal stratification in summer - stagnation
Little suspended material, but seasonally variable. Higher if shallow and exposed body of water
AUtpchtonous sources of organic matter - produced within system
Why do lakes form?
Retreating glaciers forming basins, silt deposition or cut-off meanders in rivers, sinking valleys, extinct volcano crates, landslides, man-made reservoirs
Epilmnion
Surface layer of a water column
Metalimnion
Middle layer of a water column
Benthic
Bottom - all depths
Temperature/depth differences during different seasons
Water has high specific heat capacity so slow warming and cooling of surface
Seasonal stratification
Mixing (autumn, spring, winter if no ice)
Thermoclines in summer (stratification) – and in winter if ice (inverse stratification)
Oxygen
Cold water holds more than warm
In through atmosphere, mixing, photosynthesis
Out through inc temp, inc respire, aerobic decomposition
Stratified - oxygen near bottom is used up during aerobic decomposition of organic material - bottom may become hypoxic or anoxic
Except: good oxygen through summer in deep ologotriphic lakes and clear lakes
BOD
Biochemical oxygen demand measures oxygen depletion - incubate sample for 5 days at 20 degrees and calculate mgO2 consumed per litre
Pelagic
Open water
Littoral
High water level to euphotic depth - with light
Produndal
Zone below euphotic depth (no light_
Benthic
Bottom - all depths
High pelagic/littoral ratio
Deep, open lake, dominated by pelagic phytoplankton e.g. Windermere
Profundal benthos
Homogenous, cold, little oxygen, no intrinsic food, few microhabitats, low species richness, primary consumers = bloodworm, phantom midge and pea clams
Phytoplankton seasonality
Spring blooms in temperate lakes due to mixing (nutrients also mixed – more accessible); depletion of nutrients in summer due to stratification leading to drop in phytoplankton populations (although may get nitrogen fixing cyanobacteria in late summer); autumn – may get smaller peak due to mixing
Plant communities
Submerged, emergent, floating vascular plants
Colonisation depth related to light extinction coefficient
Littoral animal communities
Upper shore – more wave action and larger stones/gravel: algal protists and bacteria attached to rocks, caddis fly larvae (some tube dwelling), motile scrapers, mayfly and stonefly nymphs. Smaller invertebrate deeper under gravel to avoid getting crashed.
Lower shore – less wave action so finer sediment: bacteria and protozoans, invertebrates on emergent vegetation such as mayfly and stonefly nymphs, freshwater shrimps, snails, caddisfly larvae
Invertebrate predators e.g. Hydra, leeches, dragonfly nymphs
Larger predators: fish (e.g. tench) and birds (e.g. water rail) feeding on invertebrates
Piscivorous fish, birds, reptiles and mammals (e.g. pike, heron, grass snake, otter)
Pelagic animal communities
Zooplankton – some independent movement e.g. diurnal (=daily) vertical migration (spend day deeper down to avoid predators, migrating up to feed during the night)
Nekton; fish e.g. charr, perch roach
Profundal animal communities
Relatively simple community, e.g. Bacteria and Protozoa
If enough oxygen also invertebrates and fish
Low oxygen: bloodworms (midge larvae)
Also well oxygenated bottom waters have low diversity
Littoral benthos
Heterogenous, warm, plenty of oxygen, intrinsic food, many microhabitats, high species richness, primary consumers = insect larvae and molluscs, carnivores = fish, leech, insect larvae
Lotic systems
Dendritic channels with lower/higher order channels
Some areas braided or meandering
Velocity dipendendo on stizze, shape, gradient, roughness, depth, ppt
Substrate type dependent on velocity
Sediments in estuaries
formed from river delta and offshore sources (during winter storms); high loads of fine suspended sediment so poor light penetration and therefore poor phytoplankton growth. Arose from either materials brought down river when they encounter higher salinities (delta formation) or transport of mud/sand into river mouth from offshore sources
L
Lotic systems connectivity: river continuum concept
Longitudinal continuum upstream to downstream, e.g. higher proportion of shredders upstream (break up larger material such as leaves to smaller pieces e.g. nymphs of mayflies, stoneflies, damselflies), higher proportion of collectors midstream (filter or catch smaller particles – light levels higher here so more algal growth); more complex distribution in practice
Lotic systems connectivity
Longitudinal (mountain headwater) vertical and lateral (dominance in braided reach and meandering reach)
Estuary
Semi-closed coastal body of water with free connection to open sea - seawater diluted by freshwater from land drainage. Fluctuations in water temp and salinity due to tidal cycle
Types of estuary
Salt wedge - gentle slope and high river flow
Vertically mixed - sleep slope and high tidal flow. Has isohalines after mixing.
Most partially mixed, some intermittent - connect with the sea only during periods of high river flow. Can be sealed off by a sand bar.
Ionic composition of estuary
Sea water higher in Na+, Cl-, sulphate
River water higher in Ca2+, HCO3- and silicate
Characteristic features of estuaries
interactions between tidal movements and variable rover flow high loads of fine suspended sediment, light penetration poor so phytoplankton growth is low, high levels of productivity based upon detritus carrying sediments down river or from the sea, or from decaying plant material from fringing salt-marshes.
Detritus in estuaries
(dead organic matter) from river and salt-marshes leading to high levels or organic matter. Detritus feeding animals include Hydrobia snails, Corophium mud shrimps and grey mullet (fish). Deposit and filter-feeding tellin clam Angulus tenuis less common than in marine systems.
Suspension feeding invertebrates in estuaries
Much less common in marine systems
Nursery areas in estuaries
For commercial fish e.g. herring
Wading birds in estuaries
e.g. dunlin, oyster catcher, redshank feed on invertebrates at low tide, for short periods of the year. High numbers.
Species diversity in estuaries
From middle tends to be lower than for either the river or marine environment, indicating the distribution of organisms is controlled by physiochemical (abiotic) factors rather than biological.
How does temperature affect surface dwelling and free swimming animals in estuaries?
More variable than in marine environment
How does salinity affect surface dwelling and free swimming animals in estuaries?
Minimum salinity at low tide and maximum river flow – restricting upper limit of marine species; maximum salinity at high tide and minimum river flow – restricting lower limit of freshwater species.
How does oxygen affect surface dwelling and free swimming animals in estuaries?
Saturation at a lower conc in the sea than in freshwater
How does sediment distribution affect distribution of benthic (bottom dwelling) species?
Coarsest sediments in subtidal channels; particle diameter decreases with depth. In the subtidal zone this relationship is complicated by wave action.
Intersital oxygen
Subtidally diffusion via interstitial water (in pores between sediment grains). Only top layers are oxygenated in this way – bacteria remove oxygen further down to give a black anoxic layer.
Intertidally oxygen is transported through water movement between grains.
Organic matter deposition in estuaries
mostly deposited in areas with little water movement, e.g. mud. Finer sediment grains also have larger surface area so more bacteria adsorbed, and therefore higher N content (from bacterial proteins). Therefore, negative correlation between median grain size and 1) proportion (%) of organic matter and 2) N content.
Productivity of benthic organisms
High
Density high – biomass and numerically e.g. 40 g dry weight per m2 of the polychaete Arenicola (found in worm casts) equalling 2 tonnes of wet weight per ha (higher than stocking rate for typical field of cattle).
Standing crop
organisms present at a specific moment of time. Many benthic species have short lifespans so high turnover of individuals – annual productivity higher than standing crop. Explains why wading birds visit estuary mudflats.
Marine zones
littoral (make up negliblie proportion of marine habitats but his productivity), neritic waters (above continental shelf), oceanic waters
Layers of water
Epipelagic 6000m underworld
Tidal power plants
make use of difference in potential energy between high and low tide by storing the water in dams with sluices that are closed when tide changes from high to low tide (difference in height). Water released through rotating turbines, generating electricity.
Potential environmental impact of tidal power plants
reduced mixing / increased stratification leading to reduced salinity and build-up of contaminants and eutrophication. Loss of habitats (mudflats, saltmarshes). Change in benthic habitats, affecting feeding birds. Damage to migratory fish and mammals.
% Earth covered by ocean
61% n hemisphere
80 south
Pacific is deepest and largest
Sea floor
• average depth just over 4000 m but great variety in depth. Continental shelf, abyssal plain, seamounts, mid-ocean ridge
Marine zones
littoral, neritic waters (above continental shelf), oceanic waters
Layers of water
Epipelagic
Light wavelenth and red algae
Blue light perpetrated deepest in clear oceans, green the deepest in coastal and red the least, so red algae found at greater depth, absorbs green and blue, but reflects red
Waves
Crests and troughs – water particles move in circles. Massive forces generated by waves (1 m3 of water has a mass of 1 tonne)
Spring tide
Moon and sun along same line
Neap tide
Moon at right angle from the sun
Ocean climate
Warm currents move towards poles and cold towards the tropics = giant thermostat
Kelp forest
In temperate sublittoral
o main kelp species in British waters belong to Laminaria
o seaweed structure: holdfast, stipe and blade
o one of the most productive habitats on Earth
o refuge for invertebrates (e.g. crustaceans, snails, brittle stars), fish (e.g. rockfish), mammals (e.g. seals, sea otters)
o kelp forest has 3-D structure: substrate-understory-canopy
Coastal upwellings
Important for nutrient transport, especially in tropics
ENSO and trade-winds
El Nino Southern Oscillations - atmospheric and oceanic processes linked
Normally trade-winds in tropical Pacific from east to west. Removal of warm water causes upwelling in the east, near the coast of Peru
Weakened trade-winds during El Niňo years – rainfall patterns etc. change globally
Temperature profiles at different latitudes
High - Well mixed, temperate regions
Mid: seasonal thermoclines, tropics
Low: permanent thermoclines
Global primary productivity highest at
continental shelves, as rivers add nutrients, and in temperate and polar seas including the North Sea, the Baltic and the North Atlantic. In tropical areas only areas with upwelling have high productivity, e.g. off west coast of South America
Antarctic food web
Relatively simple; short food chains possible due to high abundance of nutrients and plankton, e.g. phytoplankton → krill → baleen whale
Kelp forest
In temperate sublittoral
o main kelp species in British waters belong to Laminaria
o seaweed structure: holdfast, stipe and blade
o one of the most productive habitats on Earth
o refuge for invertebrates (e.g. crustaceans, snails, brittle stars), fish (e.g. rockfish), mammals (e.g. seals, sea otters)
o kelp forest has 3-D structure: substrate-understory-canopy
Rocky intertidal zone
o Upper limit determined by physical stress (temperature, desiccation)
o Splash zone (lichens, limpets), high tide zone (barnacles, limpets, spiral wrack Fucus spiralis), mid tide zone (hermit crabs, mussels, sea anemone, bladder wrack Fucus vesiculosus and saw wrack Fucus serratus), low tide zone (kelp forest, benthic invertebrates)
o Studies by Robert Paine (1966, 1974) identified cushion star Pisaster as a keystone species in the rocky intertidal of the Pacific coast of North America
o Pisaster are predators of blue mussel Mytilus
o Removal of Pisaster: Mytilus outcompeted other species by attaching themselves to the rock surface; leading to a vast decrease in the biodiversity of algae and invertebrates (28 species lost)
Coral reefs
o Wide range of niches; very high biodiversity e.g. 25 % of marine fish species found here
o Different forms of corals depending on exposure, e.g. high wave action – encrusting species, moderately exposed – branched, sheltered – finely branched
o Corals are anthozoan cnidarians
o Colonial – individual polyps are connected
o Hard hermatypic (=reef-building) corals secrete calcium carbonate skeletons – mostly in warm, shallow waters
o Most hermatypic corals contain symbiotic zooxanthellae (photosynthetic, unicellular, dinoflagellate protists) which contribute to nutrition by fixing carbon. The protist can in its turn utilise nutrients captured by polyp
o Distribution limited by temperature, water clarity, salinity and nutrient level. Optimal conditions e.g. around Australian coast, Red Sea, Pacific islands.
o Coral bleaching due to increased temperatures, acidification, deposition etc. Zooxanthellae expelled as these conditions change – carbon fixation stops and polyp dies leaving only calcium carbonate skeleton
Fringing reef
Close inshore
Barrier reef
Separated from land by lagoon
Atolls
Annular (ring forming) reefs round volcanic islands
