Coastal Flashcards
What are the key requirements of water bottles?
*Rapid exchange with surrounding water
*Reliable closures (so doesnt leak when taking out of ocean)
*Resistant to corrosion, no contamination
*Easy to handle
What is the niskin bottle?
*Most commonly used
*Simple and reliable
*Enters water open
What is the go-flo bottle?
Passes surface interface, before opening at ~10m and closing again at required sampling depth.
What is the deployment of bottles by a hydroline?
*A thin cable deployed from a winch system with bottles attached at set intervals with metal weights that slide down the line to close the bottles.
*It is simple however the line is unlikely to be vertical and does not provide knowledge of the water column structure
What is the deployment of bottles on a rosette?
*Bottles attached to rosette frame linked to the ship via a conducting cable
*Bottles can be closed individually by signal from the ship
*Other equipment can be attached to rosette, e.g. CTD
*Benefits include we can obtain a preview of the water column structure and can sample specific features (e.g. chlorophyll maximum)
What are the sources of particles in samples?
*Biology
*Dust
*Rivers and resuspension in coastal/ estuarine environments
How is the dissolved phase and particulate phase separated?
A 0.2mm filter
What makes a good filter?
*High mechanical strength
*Uniform particle cut off
*No contamination/ adsorption
How are different samples stored?
*macronutrients (N, Si, P) freeze
*trace metals (HCI) acidify to ph of 2
*DOC/DON freeze or add mercuric chloride
*cannot store ammonia
What are the 2 types of sediment traps?
*eulerian - fixed on the sea floor
*lagrangian - free drifting
What are the advantages of sediment traps?
*Direct influx measurments
*Time-series possible by rotating collectors
*aquire large mass of material
*aquire large particles
What are the limitations of sediment traps?
*potential for over and under trapping
*swimmers getting away
*microbial alteration of collected material
*expensive
*poor at collecting fine particles
What are the advantages of in situ pumps?
*rapid deployment and recovery
*Allows collection of fine particles
*Aquire large mass of material
What are the disadvantages of in situ pumps?
*Time series not possible
*Difficult to estimate particle fluxes
*large particles may be missed
What does autonomous mean?
Not connected to the ship
What are the disadvantages of ship based sampling?
*Limited spatial and temporal resolution (time of ship away and how far it can travel)
*restricted by ships capabilities (water depth, ice)
*Expensive & time consuming
*Cannot sample ‘small’ features
What are ROVs?
*Remotely operated vehicles
* operated from the surface and have no onboard crew
They are attached to the ship by a conducting cable.
*Allow precise sampling of small scale features
What are AUVs?
*Autonomous underwater vehicles
*Deployed from a ship
*Pre-programmed dive sequences
*Carry a wide variety of instruments
*Newest versions can operate down to 6 km depth, and in areas usually inaccessible to ships (e.g. under ice shelf)
What are argo floats?
*Global array of ~4000 free-drifting profiling floats that measure the temperature and salinity of the upper 2000 m of the ocean
*Allows continuous monitoring of the upper ocean, with data relayed and made publically available within hours after collection
What is the cycle of an argo float?
*Float deployment
*Descent to drifting depth
*Drifting for 10 days
*Descent to profiling depth (2000-6000m)
*Ascent - measutring ocean variables
*Data transmission
*repeat
What are the disadvantages of argo floats?
*Only last 2-5 years
*are just left on ocean floor
What are gliders?
*Can be deployed from a ship or from shore
*Can control buoyancy to move up and down
*Wings provide lift, rudder direction
*Covers long distances to provide T, S and other data (oxygen, fluorescence, nutrients, echo sounder) and data sent to home lab
*Missions can last from days to months
What are the advantages of gliders?
*Can operate independently of a ship
*High temporal and spatial coverage
*Data can be relayed remotely to shore
What are the disadvantages of gliders?
*Can be compromised in areas of strong tidal currents
*Ability for seafloor photos compromised in high turbidity
*Possible entanglement with fishing gear and collision with marine debris of shipping traffic
*Battery life
What is in situ chemical analysis?
sensors for dissolved oxygen, pH, redox potential (Eh), pCO2
how do rivers and streams change landscapes?
by meandering and eroding the land
What is the cycle of silicate and carbonate weathering?
*Chemical weathering regulates concentration of atmospheric carbon dioxide (CO2)
*weathering : CaSiO3 + 2CO2 + H2O -> Ca2+ + 2HCO3- + SiO2
*burial:
Ca2+ +2HCO3- -> CaCO3 + CO2 + H2O
*subduction:
CaCO3 +SiO2 -> CaSiO3 +CO2
What are atmospheric inputs to oceans?
- dry deposition of aerosols or wet deposition by rain
*inputs high in coastal areas due to dust generated by wind and anthropogenic inputs e.g. power plant emissions and fertilizers
How is the atmospheric inputs measured in Bermuda?
*BATS
*Tower 23 m above sea level
*Different instruments at the top; rain samplers (acid rain) filter towers, measure pollutants from US, Saharan Dust-iron supply
Sector field so only sampling when the wind blows from the ocean
What is the dissolved iron profile at BATS?
High in summer compared to april due to big plumes
What are the inputs of toxic metals to oceans?
*Measureable increase in surface ocean water lead concentrations due to combustion of leaded petrol - Now falling due to unleaded petrol
*Atmospheric deposition main source of mercury in the ocean
- Volatile element, mainly deposited as Hg2+ in rain. Global atmospheric burden has increased by factor of 5 in last 200 years as a result of human activities
How are trace gases inputted to oceans?
*Estuaries and coastal seas are an important source of some climatically active trace gases
*Most of these are directly or indirectly biological in origin
How is methane inputted to oceans?
*A trace gas
*Produced by anaerobic microbial processes
*Contributes ~15% global radiative forcing
*Mainly comes from sediments, but may be produced at pycnocline from decomposition of microbes
*Supplied by estuaries
How do ship plumes impact the ocean?
*Large increase in pollution from ship’s fuel
*Measure sulphur-dioxide which is now being decreased in ship diesel and levels have lowered reducing both atmospheric and ocean levels
What is N2O?
*Nitrous oxide
*contributes to ~6% global radiative forcing
*It is a by-product of microbial nitrification and intermediate during microbial denitrification
What is DMS?
*Dimethylsulfide
*produced by coccolithophores and dinoflagellates
*causing atmospheric acidity and condensation nuclei, influencing climate
What is submarine ground water?
*direct groundwater outflow across the ocean-land interface into the ocean
*water percolates into ground and becomes hypersaline as it dissolves minerals from rocks
*wide range in salinity as both fresh and saltwater components
What are the 3 components of SGD?
*meteoric waters (fresh)
*recirculated seawater (salt)
*connate waters (vv salty)
What are meteoric waters?
*Fresh
*driven by hydraulic gradient
*contributing factors: topography, *transmissivity, precipitation, evapotranspiration
What is recirculated water?
salt
*driven by hydraulic gradient, tidal pumping, wave set-up
*Contributing factors: tidal range, period, frequency, wind force and direction
What are connate waters?
*vv salty (36+)
*driving forces: density, thermal gradient
*contributing factors: geology, geothermal heating
How can we detect and quantify SGD?
*Infrared imaging - High latitudes, SGD warm relative to ocean. Low lats, cooler
*Direct measurments - Seepage meters
*Tracer techniques - Natural (radionuclides in uranium and thorium decay series). Artifical (dyes)
How is radium used to trace SGD?
*266Ra tracer
*1600years half life (long)
*Concentration very low in seawater, high levels in coastal ocean provide evidence for large SGD fluxes
What are the chemical reaction in subterranean estuaries?
*Oxidation of organic carbon adds CO2, and results in calcite dissolution
*High levels of nutrients due to water-rock interactions (P), and anthropogenic inputs (N, P)
*Removal of nitrate by denitrification in low oxygen groundwaters
*Removal of dissolved iron at freshwater-saltwater interface, and scavenging of other components (e.g. P)
What are glacial inputs to polar shelf seas?
*Inputs of iron from melting of glaciers
*Possibly due to the breakdown of iron oxyhydroxides by microbes under anoxic conditions
*produces bloom
What is the significance of estuaries?
*most river-borne material passes through
*important transition zones (“estuarine filter”)
*anthropogenic inputs, either directly or through river
What are the 4 types of estuarine mixing?
*highly stratified (salt wedge)
*partially mixed
*well mixed
*inverse estuary (negative circulation)
What is highly stratified (salt wedge) estuarine mixing?
*Large river input, weak tidal input of salt water
*River has higher impact than estuary
*Isohalines almost horizontal and close together. Position of salt wedge depends on river flow
What is partially mixed estuarine mixing?
*Small river input, large tidal input
*Inflow of salt water dominates. *Total energy sufficient to shear isohalines causing turbulence. *Salinity increases from head to mouth but two layers separated by zone of mixing can be identifies.
What is well mixed estuarine mixing?
*Small river input, very large tidal input
*e.g.Solent
*Tidal range large enough to mix estuary completely and isohalines nearly vertical
What is Inverse estuary (negative circulation) estuarine mixing?
*Salinity increases towards river mouth
*hot climates where evaporation exceeds freshwater input)
What is the concentration of Total dissolved solids (TDS) in river and seawater?
River = 20 – 400 mg/L
Sea = 35 g/L
What does the concentration of major ions vary with?
*Salinity
*Greatest changes in proportion of major ions occurs at salinity of 5 psu
*More major ions in seawater the freshwater river end
What is the dilution of seawater constituents in an estuary?
*All of the major ions (Na+, Cl-, Mg2+, SO42-, etc) and some of the minor ions (e.g. Br-) in seawater are simply diluted by mixing with freshwater in the estuary
*plot of salinity vs the concentration of that constituent is a straight diagonal line
Impact of concentations of major ions differing in riverwater on TDL?
*n seawater, major ions have same concentration (due to high residence times), but concentration of major ions in river water is highly variable
*However, little effect on mixing diagram except at very low salinity
*Same levels at high salinity (ocean) but different at low (river)
What is the TDL?
*Theoretical dilution line
*river water endmember to seawater endmember
*shows conservative behaviour in the estuary
What processes affect the concentration of minor or trace constituents in estuaries?
*Biological processes (photosynthesis/ remineralization)
*Adsorption/desorption on particle surfaces
*Coagulation/ flocculation/ precipitation
*Redox processes
What behaviour do minor/trace constituents show in estuaries?
*Non-conservative
*Possibly due to sinking and interactions with the sediment along the redox boundary
What is adsorption?
*binding of dissolved chemical species (solutes) to a mineral surface by formation of surface complexes
*the solute is incorporated into the mineral structure
What does mineral adsorption of solutes depend on?
*the mineral and pH
*Surface charge is a function of pH, reflecting the extent of protonation (H+) of oxygen atoms at the mineral surface
What is pHpzc
Where the surface charge is zero - nothing is absorbed or desorbed
What happens above the pHpzc?
the surface is negatively charged and will sorb cations
What is a cation?
Anything with a + e.g. Fe3+, Zn2+
What happens below the pHpzc?
the surface is positively charged and will sorb anions
What are anions?
Anything worth a - e.g.NO3-
What is the pH of river water?
pH of river water normally fluctuates from 6-8 in a healthy system
How do estuaries affect the flow of metals into the ocean?
*Sorption of metals onto iron (oxyhydr)oxides will occur in estuaries, and is a major control on dissolved concentrations of metals delivered to the coastal ocean
*Stops it being a source to the coastal zone
What are colloids?
Colloids are very small particles (nanoparticles) that remain suspended in aqueous solutions
What are the main colloidal phases in rivers?
*Clay minerals (kaolinite, montmorillonite)
*Iron (hydr)oxides (goethite, hematite, ferrihydrite)
*Humic/ fulvic acids associated with FeOOH
When do colloids fluctuate?
Colloids will flocculate when their surface charge = 0
when does flocculation of clays take place?
as soon as river water encounters seawater
when does flocculation of humic acids and FeOOH take place?
at salinities of ~5
how does flocculation affect the flow of ions to the sea?
Flocculation will incorporate colloids (and their sorbed metals) into estuarine sediments as they stick together and sink
Why is organic carbon concentrations high in estuarine sediment?
*in seawater - all material flocculates out (faster with turbulence)
*in river water - no flocculation
*means organic carbon gets trapped in estuaries -> big source of food for benthic invertebrates leading to high biological productivity
*little evidence that terrestrial organic matter contributes much to marine sediments beyond the continental shelf
What are redox processes in estuaries?
*Estuarine sediments are usually reducing
*Concentrations of some dissolved species may therefore be higher or lower in sediment pore waters than overlying estuarine water
*Leads to diffusion into/out of sediments
*eg. Fe and Mn
What impacts redox rates?
*Rate of exchange increased by sediment resuspension
*prescence of organisms e.g.tubeworms
What is non-conseravtive behaviour?
*addition or removal of solutes during estuarine mixing
*Biological processes, adsorption & desorption, coagulation/ flocculation and redox processes may add or remove solutes in the estuary
what is the limitation of mixing diagrams?
do not provide any information about the processes that cause the addition or removal
What are the assumptions for mixing diagrams?
*Estuary is in steady state, i.e. flux in = flux out
*Concentration of endmembers is constant on timescales longer than the residence time of water in the estuary
*Ƭres = Vf/R where Vf is the volume of freshwater in the estuary and R is the flux of river water into the estuary
*Only one river endmember and one seawater endmember
*No additional sources of material
What are the limitations of mixing diagrams?
*If residence time (flushing time) is short, nonconservative behaviour will not be detected if it happens so fast, may not be seen by measurements
*Mixing diagrams indicate apparently non-conservative behaviour:
*If residence time is long, and there is temporal variability in the endmembers
*If an estuaries receives input from more than 1 river
*If an estuary receives additional sources of material, e.g. sewage outflow
What are the characteristics of fluorine in estuaries?
*Conservative
*Higher concentration in seawater (the source)
What are the characterisitcs of iron in estuaries?
*non-conservative
*nearly all Fe from river source is coagulated and lost before it reaches the sea
how does the speciation of Fe affect coagulation?
most lost is Fe(III), the conc of Fe(II) can be high (stabilised by ligands)
how does salinity affect concentration of Fe(II)?
*Concentration of Fe(II) decreases with increasing salinity
*perhaps due to loss of (organic) ligands via flocculation and/or effects of increased ionic strength
What are the characteristics of silicon in estuaries?
*Dissolved silicon can show both conservative and non-conservative behaviour
How does silicon concentrations impact biology?
*High levels of Chl a occours with very low levels of dissolved silicate
*promoting a diatom bloom
*If biological productivity is high, loss of dissolved Si due to uptake by diatoms
how does the residence time of silica affect its behaviour?
*low residence time - conservative
*high residence time - non-conservative
*Depends on river flow rate
*if residence time is short (riverwater flux is high) then any dissolved silicon used by diatoms with be rapidly replenished
how do saltmarshes affect seasonal flux of silica?
*Over the course of a year, marsh is a net sink of both dissolved and biogenic silicon
*summer - remineralisation so acts as a source
*winter - diatoms sink and so marsh acts as a sink
how are silica isotopes used to see the processes behind removal?
*Diatoms preferentially utilize lighter Si isotopes to form frustules, so the remaining dissolved silicon is enriched with heavier isotopes
*if heavier isotopes left, then removal is from a biological process
*can be used to study nutrient utilisation and remineralisation of biogenic silicon
*Any organism will always use the light isotope as it is easy to take up
How does turbidity impact silicon?
*Particle loading may affect light penetration in some estuaries
*River biological production is inhibited by turbidity
What are the characteristics of manganese in estuaries?
Manganese undergoes intensive cycling in many estuaries because its chemistry is linked to changes in redox conditions
What are the characteristics of manganese in oxidising conditions?
*Significant free O2
*Mn(IV) is thermodynamically stable
as MnO2 has low solutbility Mn(IV) forms particles or coats them
What are the characteristics of manganese i reducing conditions?
*oxygen defiicent
*Mn(II) is thermodynamically stable
*Mn2+ it is soluble and can diffuse and advect in solution
Impact of reducing sediment on manganese?
*In anoxic sediments, Mn(IV) is reduced to Mn(II), which is soluble
*Mn(II) may diffuse out of the sediments, and flux is increased by resuspension of sediments
*Maximum in concentrations of dissolved Mn is often seen at intermediate salinities
What are the kinetcs of Mn(II)
Kinetics of Mn(II) oxidation
are slow, so Mn(II) can persist
at concentrations higher than
predicted by thermodynamics
*High concentrations of Mn(II) can also be found in the water column if
circulation is restricted, e.g. fjord
What is habitat mapping?
*Produce info about seabed
*Substrate typoe
*Flora/fauna
*Inputs and outputs
*Energy and nutrients
Why do we need to map?
*Marine conservation and science
*Marine resources (e.g. carbon capture + oxygen cycling uses)
*Marine engineering (how it impacts organisms)
How can we collect data?
*Satellites
*Surface vessels / equipment
*Sub surface e.g. gliders, AUVs, ROVs, floats
What is a biotope?
*A combination of physical environment (habitat) and its distinctive assemblage of conspicuous species
*Controlled by substrate and sediment
What are biotopes controlled by in shallow water?
*energy from the sun and depth of water
*also the environment e.g. wind, waves, temp
What are classification schemes?
*used to classify types of sediment and its biodiversity
*Can include zonation, substratum, sediment types, wave exposures
Why is sedimentation rates high in estuaries?
*Reduction in river water flow
*Aggregation/ flocculation (deposition of fine sediments)
*High rates of biological activity
What are the characteristics of organic carbon in coastal waters?
*Decomposition of organic matter is mainly carried out by bacteria
*In contrast to the deep ocean, sediments in coastal waters and estuaries have very high levels of organic carbon (can be up to ~7 wt%), due to high rates of biological productivity
What is the trend in organic carbon in deep sea sediment?
1.6% at the surface, decreases rapidly then plateaus at 0.4%
due to bacterial decomposition
What is the most important oxidant in seawater?
*Oxygen
*it has a high concentration and is used in microbial cellular processes as it requires little energy to respire
*However, in sediments oxygen may be used up more rapidly than it can be re-supplied by diffusion, so other oxidising agents are used in sequence
What is the diagenetic sequence?
O2 (aerobic respiration)
NO3- (denitrification)
Mn(IV) as Mn oxide (Mn reduction)
Fe(III) as Fe oxide (oxyhydroxide) (Fe reduction)
SO42- (sulphate reduction)
CH2O (methane fermentation)
*This sequence is microbially catalysed
What is the sequence of bacterial decomposition processes?
*Aerobic respiration
*Manganese (IV) reduction
*Denitrification
*Iron (III) reduction
*Sulphate reduction
*Methanogenisis
How deep does O2 penetrate in different regions?
*open ocean = 10s cm
*estuaries/shelf seas = few mm to cm (as supply of organic material is much higher)
What are the characteristics of redox zones in estuaries and coastal sediments?
*tend to be compressed
* may even occur simultaneously (e.g. due to the presence of microenvironments, such as burrows/ root tubes, and ‘organic hot-spots’)
What is bioturbation?
Exchange of solutes between pore waters and overlying seawater driven by diffusio
What impacts the rate of bioturbation?
May be enhanced by:
*Sediment re-suspension
*Bioirrigation
Theses supply oxygen deeper into the sediment but increases the movement of other nutrients up to the surface
how are sediment profiles measured?
pore water sampling
- take cores
- chemical tests capture the capture the gradient in organic carbon supplied to surface sediments between the cape shelf and cape basin
What causes accumulation of metals occur in the the sediment?
*Metals adsorped on Fe/Mn oxyhydroxides (e.g. Cu, Ni, Zn, Cd, Co) will also be released into sediment pore waters if these phases are reduced
*Leads to cycling of metals at the oxic/anoxic boundary
*can lead to accumulation of metals in sediments
How are estuarine sedimentation rates calculated?
*Primordial radionuclides (derived from rocks) can be used to assess:
*Sediment accumulation rates & mixing (234Th & 210Pb)
*Dating techniques (e.g. shell growth rates using 228Ra, 210Pb & 210Po)
*Bioturbation (234Th)
What is the cycle to the formation of 210Pbxs?
*226Ra in soils and rocks decays to 222Rn, a noble gas
*222Rn escapes and decays to 210Pb
*210Pb removed by precipitation and incorporated into accumulating sediment
What does the total concentration of 210Pb in sediments show?
*sum of excess activity and ‘supported’ activity from decay of 226Ra in the sediment itself
*Once incorporated in sediment, 210Pbxs decays at known rate, allowing sediment accumulation rate to be estimated
why is it important to discard the data points from the top cm of sediment when measuring the sedimentation rate?
210Pb activity is affected by bioturbation - will affect results massively
What is the sedimentation rate equation?
S = z/t
(where z is depth and t is time)
What is the radioactive decay equation?
lnA1 / A2 = λ(t2 - t1)
How do you calculate a sedimentation rate?
1.Identify the background (“supported”) activity AB - the value of A at greater depths where it is not changing with depth.
2.Subtract the background activity from the observed activities at shallower depths
3.Take the natural logarithm to get ln(A) = ln(Ameasured - AB)
4.Plot depth z against ln(A).
5.Ignore in the points in the surface mixed region where ln(A) does not change with depth.
6.Ignore points in the background region at depth (Ameasured ≈ AB).
7.Measure the slope in the middle region. It will be negative.
8.Multiply the minus the slope by the radioactive decay constant (λ = 0.0311 yr-1 for 210Pb) to get the sedimentation rate.
where is sedimetntation rate highest?
*Continetal margins - upper gulf of thailand up to 1100 cm/1000yr
Where is sedimentation rate slowest?
Deep-ocean sediments - deep sea clays as slow as 0.03 cm/1000 yr
What are the different forms of carbon in estuaries in orde of unput per year?
*Dissolved inorganic carbon (DIC)
*Dissolved organic carbon (DOC)
*Particulate organic carbon (POC)
*Total organic carbon (TOC) = DOC + POC
*Particulate inorganic carbon (PIC)
How is DIC formed?
(CO2(aq) + H2CO3 + HCO3- + CO32-)
Carbonic acid is formed when CO2 diffuses into sea but breaks down extremely quickly into carbonate and then bicarbonate
What are allochthonous inputs of carbon to estuaries?
*Rivers
*Bordering wetlands (mangroves and fresh water/ salt marshes)
*Seawater
*Submarine groundwater discharge
What are autochthonous inputs of carbon to estuaries?
*Plankton
*Emergent and submergent aquatic vegetation in the estuary (e.g. seagrasses)
*Secondary production (e.g. zooplankton, fish, benthic animals)
What is the carbon flux equation?
carbon flux = carbon concentration x discharge
how much carbon do rivers export?
1 Gt of carbon annually
what regulates flux of carbon from the river?
*primarily discharge
*DOC affected by temperature
how do hydrologic events affect river discharge?
*have a disproportionate effect
*tropical storms can be responsible for >40% of annual average riverine DOC export
*single large flood events can export 80-90% of POC from mountainous regions
where are terrestrial DOC sources derived from?
terrestrial vegetation and soils
what are terrestrial DOC sources composed of?
*Largely composed of aromatic carbon (lignin inputs from vascular plant materials)
*Plants decay and the carbon is locked away within the sediment
What are terrestrial POC sources?
*Plant biomass
*Physical erosion of catchment rocks.In rivers, clay particles tend to be negatively charged, preventing flocculation. In estuaries, increasing abundance of cations reduces repulsive forces and coagulation occurs
which phases of plant biomass are most easily leached (converted to DOC)?
low MW carbohydrates, proteins and fatty acids
which phases of plant biomass are most refractory?
lignin and cellulose
what is black carbon?
*Oxidation products of fossil fuel and biomass combustion (e.g. soot, charcoal)
*Direct aerosol deposition in rivers and estuaries
How much carbon does SGD supply to estuaries?
SGD can be a significant source of DOC to coastal waters (up to 20-30% of river flux)
Where are salt marshes and mangroves located?
*Salt marshes: mid-high latitudes
*Mangroves: low latitudes
What are the characteristics of Intertidal salt marshes and mangroves?
*Among most productive ecosystems on Earth (400 – 2250 g C m-2 yr-1)
*Some of this carbon is exported to estuaries
*POC flux may be 4-5 times higher than the river flux
*DIC flux may be as large as the river flux
What is the key role estuaries play in the cycling or carbon?
cycle of carbon by modification of organic matter delivered from land to the coast → can be a sink or a source, depending on whether it locks up carbon or releases it.
What leads to interchange between DOC and POC?
Mineral sorption and desorption and photochemical dissolution
how is OC lost in estuaries?
microbial degradation and photochemical oxidation, scavenging, sedimentation & salinity-induced flocculation of DOC and POC
what is outgassing of CO2?
in productive estuaries, the concentration of CO2 is higher than in the atmosphere, so it diffuses out
when does DOC act conservatively in estuarine mixing?
*Riverine DOC is non-reactive
*Estuarine residence time short relative to DOC reactivity
*Estuarine sources of DOC are small
What are additional sources
of DOC to estuaries?
*Mangroves, salt marshes
*Resuspension events
How is DOC removed from estuaries?
Flocculation (e.g. HMW humics)
How do estuaries and the atmosphere interact with CO2?
*Estuarine waters are significant sources of CO2 to the atmosphere (~0.25 Pg C yr-1)
*Estuaries are heterotrophic: they respire more organic carbon than they produce, and there is a DIC/CO2 excess
*CO2 loss is likely largely supported by microbial decomposition of OC produced in coastal wetlands
What are the characteristics of continental shelves?
Continental shelves occupy 7-10% of global ocean area, but contribute 10-30% of global marine primary production, 30-50% of inorganic carbon and ~80% of organic carbon burial in sediments. Could contribute up to ~50% of OC supplied to deep ocean
why are only very small amounts of terrestrial organic matter detected in oceans?
a large fraction must be chemically altered (photoreactions, bacterial alteration), rather than completely oxidized on shelves
how does latitude affect the productivity of estuaries?
*Shelves located between ~30˚ and 90˚ latitude tend to be sinks of CO2
*Shelves located between the equator and 30 ˚ latitude tend to be sources for CO2
what are the theories for the affects of latitude on estuary productivity?
Higher river DOC fluxes at lower latitudes and high temperatures = higher respiration?
or
River dominated margins are CO2 sinks (high 1° productivity/ net DIC consumption), whereas ocean dominated margins are CO2 sources due to transport of high DIC waters into surface waters with low nutrients?
how has estuarine productivity changed over time?
*In pre-industrial times, continental shelf was probably heterotrophic
*Today, shelves are a CO2 sink (autotrophic)
what are the theories for why coastal estuaries are now a sink of CO2?
Result of enhanced biological uptake of CO2 due to stimulation of shelf primary production by increased anthropogenic inputs from land
or
Increased physical uptake of atmospheric CO2 as atmospheric CO2 levels have increased more than those of shelf waters
How will climate change influence estuarrine carbon cycles?
*Will influence organic matter derived from primary production through changes in precipitation, freshwater delivery and stratification leading to changes in nutrient delivery, primary production and species composition
*Additional changes to biogeochemical processes in estuaries will likely arise from:
(a) warming and associated changes in metabolism
(b) increased alkalinity and associated reductions in pH
(c) a lowering of dissolved oxygen concentrations
What are oligotrophic waters?
low nutrient status aquatic environment (e.g.gyres)
What are eutrophic regions?
nutrient rich region
What are mesotrophic waters?
intermediate nutrients
What causes hypernutrification?
Excess nutrients in estuaries
What is eutrophication?
Eutrophication is the enrichment of the environment with nutrients and associated production of undesirable effects
What is an undesirable disturbance?
a perturbation of a marine ecosystem that appreciably degrades the health or threatens the sustainable human use of that ecosystem
What are the stages of eutrophication?
1.Excess Nutrients
2.Excess Algal Growth- can lead to Harmful Algal Blooms (HAB)
3.Reduction in Sunlight (
4.Algal Death
5.Bacteria digest the dead plants, using up remaining oxygen, and giving off carbon dioxide.
6.If they can’t swim away, fish and other wildlife become unhealthy, or die without oxygen.
What are the consequences of increased algal production?
*changes in species composition
*abnormal blooms of algae
*toxic algal species
*deoxygenation
*adverse effects on fish and invertebrates
*changes in structure of benthic communities
What are the sources of nutrients to the sea?
*Atmospheric inputs
*Submarine groundwater
*Weathering / land runoff
*Benthic inputs
*Plant and animal decomposition
*Excretion
What are anthropogenic inputs of nutrients to sea?
*Fossil fuel burning / industrial input
*Sewage discharge
*Farming runoff - fertilizer and animal waste
*aquaculture
Is eutrophication reversible?
Is reversible in almost all cases if you get rid of the source of excess nutrients
What is in sewage?
*a mixture of all liquid domestic wastes and is an oxygen demanding pollutant
*Includes:
human body waste
faecal matter
Urine
domestic household wastes
chemical/industrial wastes
How many moles of O2 does sewage use?
6
What are the stages of sewage treatment?
*preliminary treatment
*primary treatment (sedimentation)
*secondary (biological) treatment
*tertiary treatment (only when high quality is required)
What is preliminary sewage treatment?
screening large objects, maceration and grit removal. Iron bars 5-10cm spacing, removes wood, paper, bottles
What is primary sewage treatment?
(sedimentation): suspended solids separated out as sludge
What is secondary sewage treatment?
biological - dissolved and colloidal organics are oxidised in presence of micro-organisms
What is tertiary sewage treatment?
used when high quality effluent is required. It may involve removal of further BOD, bacteria, suspended solids toxic compounds and nutrients
what is a dry spill?
when untreated wastewater spills straight out into rivers and seas when there is no rain which is illegal
what are legal spills?
when there is heavy or prolonged rainfall, water companies are allowed to spill untreated wastewater
How are sewage discharge spills recorded?
*Spill counting starts when the first discharge occurs. A discharge occurs when the sewer level exceeds the threshold level.
*Any discharge(s) in the first 12-hour block is counted as 1 spill.
Any discharge(s) in the next and subsequent 24-hour blocks are each counted as 1 additional spill per block.
*This counting continues until there is a 24-hour block with no discharge
What are dead zones?
areas of hypoxia where there is a reduced level of oxygen in the water
What is a natural example of hypoxia
Baltic Sea due to upwelling causing phytoplankton blooms which then completely deplete the oxygen when they die and sink
At what depth are oxygen minimum zones found in the ocean?
intermediate depths
Why are the impacts of oxygen minimum zones far reaching?
important mobile macro-organisms avoid or cannot survive in hypoxic zone
What are the impacts of hypoxia?
*Alter fish diets
*growth rates
*reproduction
*habitat use
*availability of commercially harvested species such as shrimp
Why might southampton waters be eutrophic?
*Potential due to industry nearby
*Lots of sewage output
Is Southampton water eutrophic?
no, bloom is seasonal and happens only for short periods of time
What is the link between cyanobacteria and eutrophication?
Cyanobacteria can thrive in diverse conditions and sometimes form harmful blooms, especially in warm, nutrient-rich waters. These blooms can produce toxins, posing health risks to humans and animals, and disrupt aquatic ecosystems by depleting oxygen levels
What are eutrophication catchment solutions?
*Water-friendly Agricultural Practices
*Urban Runoff & Sewage Management
*Wetland Restoration
*Community Engagement
*Real-time Monitoring
What are Water-friendly Agricultural Practices?
*Work with Farmers
*Install livestock fencing along water courses
*Reducing use and safe handling of pesticides
*Soil testing
*Tree Planting
*Buffer zones
What are Urban Runoff managment solutions?
*Enhance stormwater management and sewage treatment
*Soft engineering solutions with sustainable urban drainage systems
*Install reed beds and wetlands to reduce urban run off
How does wetland restoration work?
*Wetlands will establish a buffer zone
*Filter pollutants such as excess nutrients
*Provide wildlife habitats
What is blue carbon?
carbon stored on the biomass and sediments of blue forests
What are blue forests?
*the coastal and marine ecosystems that sequester carbon and provide a multitude of ecosystem services
*e.g. mangroves, seagrass, saltmarshes
Where are mangroves found?
restricted to tropical/subtropical regions
Where are saltmarshes found?
dominate UK coasts, and europe / temperate climates
Where is seagrass found?
temperate hot environments, Australia, east coast US
What is the sequestration rates of blue forests to terrestrial forests?
10x more than into terrestrial forests
how is carbon removed in estuaries?
trees up the estuary
tidal marshes and biological pump
What are ecosystem services?
benefits that humans derive from healthy ecosystems or ‘natures contributions to people’
What are the positives of blue forests?
*shoreline protection from storms/flooding
*store carbon
*food security
*biodiversity
What are the characteristics of mangroves?
*Host high biodiversity of fish, invertebrates, reptiles and mammals
*Able to grow in saltwater or brackish environments
*Exposed and submerged with the ebb and flow of the tide
what were the leading drivers of deforestation of mangroves?
*shrimp farms
*forest use
*fish culture
What are the consequences of mangrove loss
*decrease in species diversity and abundance
*coastal erosion
*decrease in water quality
What are causes of decline in seagrasses?
*Physical disturbance
*Turbidity
*Nutrients / Eutrophication
*Wasting disease
*Sea level rise and coastal erosion
*Habitat loss
what happened to seagrass in the Caribbean?
*Loss of seagrass
*smaller leaves
*invasive species
how much seagrass has been lost?
*Global loss of 0.9% yr-1 pre 1940
*Global loss 7% yr-1 since 1990
*Estimated 84 - 92% loss of seagrass in the UK
how did exclusion experiments help seagrass?
excluded megaherbivore using cages (big fish)
allowed seagrass growth
What needs to be considered when proposing a MPA?
*organisms
*ecosystems
*movement (how do organisms move from out to inside the MPA?)
*vertical distribution
*fish stock population
Why are oyster reefs important?
*Important fisheries resource
*Excellent filters-important for water quality
how much oyster reefs have been lost?
85% of oyster reefs were lost globally and oyster reefs were functionally extinct
What are the causes of oyster reef loss?
*Losses due to overfishing, *Eutrophication
*coastal development sewage inputs
*sedimentation
*habitat disturbance
*large scale industries
What are the impacts of oyster reef loss?
*impact on communities that relied on the harvest of bivalve habitats for employment and food
*Reduced water quality
What are the benefits of oyster reef restoration?
*Boost local fish and crustacean fisheries = more fishing
*Improve water quality, a single oyster can filter 200 litres of water every day
*Protect shorelines by reducing coastal erosion-have similar coastal defence as dykes
*Improve estuary condition
increased biodiversity
how do oysters improve water quality?
Particles are drawn from the water column and deposited to the benthos, a process which both decreases turbidity in the water and which enriches the sediments with bioavailable carbon and nitrogen
what were the implications of Australian reef restoration?
used non native species from new zealand
short term success
but introduced exotic diseases, competitors and predators
what are strategies for reintroducing bivalves?
use shells as settlement surface for larvae- needed to be done over and over again- ‘’ - not sustainable - put and take
what is the biggest barrier to oyster restoration?
the lack of oysters, so we need to breed more oysters, but in a way that preserves genetic diversity, harnesses disease resistance, but doesn’t spread disease
What is bioavailability of plastic
how available the plastic is to the organism / how likely are they to take it up and what effect will it have
what % do plastics make up of marine litter?
80% - estimates of 5.2 trillion pieces to 15-51 trillion pieces
how does marine plastic affect marine species?
ingest or are entangled by plastic debris -> injury and death
what are the threats of plastic pollution?
*threatens food safety and quality
*human health
*coastal tourism
*contributes to climate change
What are the main sources of ocean plastics?
*tyres (48%)
*pellets (28%)
*textile laundering (8%)
where does the majority of the ocean plastic end up?
remains by the coast or on beaches, it isn’t swept out to sea and diluted
What are primary microplastics?
*those which enter the environment micro in size
*e.g.microbeads, pellets, film, fiber
What are secondary microplastics?
*resulting from the breakdown of larger plastics in the environment
*fragments -> ragged, irregular in shape and strong
*derived from the larger plastic waste
what happens to microplastics as they move from freshwater to saltwater?
*variation in buoyancy -> most sink in freshwater but float in seawater and estuaries
how do microplastics affect marine life?
*accumulate up the food chain
*nurdles - mistaken for fish eggs
*microplastics attract and adsorb toxins (like DDT) from the surrounding marine environment -> hazardous to higher trophic levels
What factors influence Micro Plastic Bioavailability?
*Size- small size=mistaken by predators during feeding and consumed passively by zooplankton species
*Colour-Euphausiids and copepods are black, red and blue in colour-so plastics in these colures consumed more
*Abundance-greater the abundance=greater chance of consumption by organisms
What impacts marine plastics?
*Degrade under high exposure to ultraviolet (UV) light, coupled with physical abrasion due to wave
action and sediment movements
*Weakens the polymer bonds of plastics and they fragment, which leads to secondary microplastics, adding to the microplastic load
What are the impacts of ingestion by marine organisms
*aggregation in soft tissues
*swelling of liver and aggregation in liver
*toxicity symptoms
*impact on metabolic rate
*decreases in feeding and reproduction
where does plastic accumulate in the open ocean?
*In sub tropical gyres due to ocean currents
*plastic is buoyant so stays at the surface
*e.g. east pacific garbage patch
where plastic from SE Asia accumulates
What are strategies to reduce plastic pollution to the oceans?
*Ban microbeads
*economic incentives
*co-management and voluntary initiatives
*technological innovation and infrastructure (nets blocking mouth a river)
What is the great pacific garbage patch?
*patch of solid waste the size of *Texas floating in the currents of the North Pacific gyre, mostly consisting of plastics.
*1.6 miilion square kms
*1.8 trillion pieces of plastic
