Chapter 10. Chapter 10.

Resources from the Ocean FloorResources from the Ocean FloorOutline Outline Types of Resources Types of Resources Petroleum beneath the sea floor Petroleum beneath the sea floor Raw Materials from shelves Raw Materials from shelves Heavy metals on the deep sea floor Heavy metals on the deep sea floor Dumping on the sea floor Dumping on the sea floor

10.1 Types of Resources 10.1 Types of Resources

Energy sources; petroleum and gEnergy sources; petroleum and gas as

Raw materials; sand and gravel, Raw materials; sand and gravel, phosphorite, heavy metal ores phosphorite, heavy metal ores

A dump site for waste A dump site for waste

Table 10.1 Sea- bed Resources [After J. M. Broadus, 1987, Science]

10.2 Petroleum beneath the sea floor 10.2 Petroleum beneath the sea floor

10.2.1 Economic background 10.2.1 Economic background more and more expensivemore and more expensive

Resources Resources Reserves (=producible petroleum Reserves (=producible petroleum

under prevailing economic and under prevailing economic and technological conditions) technological conditions)

10.2.2 Origin of Petroleum 10.2.2 Origin of Petroleum Petroleum is a complex of hydrocarbons and Petroleum is a complex of hydrocarbons and

other organic compounds originating from other organic compounds originating from organic matter produced both on land and in the organic matter produced both on land and in the sea, but sea, but largely from marine planktonlargely from marine plankton. .

Only about 0.01% of the organic matter in Only about 0.01% of the organic matter in sediments became concentrated in oil and gas sediments became concentrated in oil and gas fields fields

Why so little?Why so little?

Fig.10.1 Origin of petroleum. After burial of the organic0rich sediment containing the source material (black), carbon compounds (chains and rings) are produced. In the zone above 1 km depth, the numbers of C-atoms tend to be large within the organic molecules. In the oil zone, compounds with fewer C-atoms (and more H-atoms) are produced by a cracking process, due to elevated heat and pressure. Under a large overburden, gas is produced (CH4 = methane).

Reasons Reasons 1) The organic matter captured within the sediment must be converted 1) The organic matter captured within the sediment must be converted

to fluid petroleum by to fluid petroleum by thermochemical processesthermochemical processes, requiring a , requiring a blankeblanket of sediments more than 1000m thickt of sediments more than 1000m thick and temperatures of and temperatures of 50 to 1550 to 150 .℃0 .℃   If temperatures become too high, oil is cracked to natural gas.   If temperatures become too high, oil is cracked to natural gas.

2) Petroleum must migrate from organic-rich 2) Petroleum must migrate from organic-rich source-rocksource-rock sediment sediments to porous and permeable s to porous and permeable reservoir rocksreservoir rocks such as sandstones or such as sandstones or vuggy limestones in response to compaction pressure and gravity vuggy limestones in response to compaction pressure and gravity

Fig.10.2 a, b. Prerequisites for petroleum accumulation. a Basic ingredients of a petroleum reservoir system, showing migration from source beds (shales rich in organic matter) into reservoir (porous rock, e. g., vuggy reef limestone or sandstone). b Salt dome tectonics as an example for trapping conditions

Reasons – 3 & 4Reasons – 3 & 43) Reservoirs must be big enough to be of i3) Reservoirs must be big enough to be of i

nterest, and they must trap petroleum with nterest, and they must trap petroleum with impermeably cover rocks such as thick shimpermeably cover rocks such as thick shales or evaporites.  Otherwise the more voales or evaporites.  Otherwise the more volatile hydrocarboms escape to the surface. latile hydrocarboms escape to the surface. – – CaprockCaprock

4) These several petroleum-forming process4) These several petroleum-forming processes must take place within the es must take place within the correct time-correct time-frameframe: each process needs to complete its : each process needs to complete its turn in the proper sequence. turn in the proper sequence.

10.2.3 Where Offshore oil is found 10.2.3 Where Offshore oil is found The classic are of offshore oil fields; Gulf of Mexico The classic are of offshore oil fields; Gulf of Mexico Marine sediments overlie salt, which is gravitationally Marine sediments overlie salt, which is gravitationally

unstable, being less dense than the overburden. unstable, being less dense than the overburden.

It pushes up in It pushes up in plumes, making the plumes, making the so-called salt so-called salt domesdomes. .

The upturned The upturned sedimentary strata sedimentary strata butting against the butting against the salt provide traps for salt provide traps for petroleum petroleum

Fig.10.3 a, b. Salt plumes in the Gulf of Mexico. a Schematic profile of Pliocene-Pleistocene sediment wedge intruded by early Mesozoic salt deposits. Intrusion of salt in the Sigsbee Abyssal Plain produced the Challenger Knoll. (CK). b Seismic profiler record from Sigsbee  Knolls region. Challenger Knoll was drilled in Hole 2 of Leg  q of the Deep Sea Drilling Project, establishing its mature as a salt dome feature. Time scale is two-way reflection time (sea floor = 4.5 s 3400m). △

Where Offshore oil is foundWhere Offshore oil is found

Another area from which offshore oil has been Another area from which offshore oil has been produced for a long time is the produced for a long time is the Continental Continental borderland off Southern Californiaborderland off Southern California. .

Oil originates from Miocene organic-rich marine Oil originates from Miocene organic-rich marine strata originally formed under conditions of strata originally formed under conditions of upwelling and oxygen deficiency. upwelling and oxygen deficiency.

The oil is trapped in sandy layers abutting The oil is trapped in sandy layers abutting against faults. against faults.

Can this be applied to Korea?Can this be applied to Korea?

Fig.10.4 A-C. Structural cross-sections across Auk-Ekofisk and Forties-Maureen fields, North Sea vertical exaggeration 6.7×, Insert Map with national sgelf boundaries

A broad belt of gas fields stretches east-west Germany to southerA broad belt of gas fields stretches east-west Germany to southern England. n England.

Gas migrated from Gas migrated from Carboniferous coal measuresCarboniferous coal measures to to porous Lower porous Lower Permian sandstonesPermian sandstones and is sealed by and is sealed by overlying Zechstein (upper Poverlying Zechstein (upper Permian) evaporitesermian) evaporites. .

Oil fields, however, are Oil fields, however, are concentrated around a concentrated around a north-south rift in the north-south rift in the northern North Sea which northern North Sea which originated in the first states originated in the first states of opening of northern of opening of northern Atlantic. Atlantic.

Cretaceous Chalk Cretaceous Chalk reservoirs reservoirs

10.2.4 Present Oil Exploration 10.2.4 Present Oil Exploration

Prerequisites of petroleum formation and Prerequisites of petroleum formation and migration; elevated temperature and a cover of migration; elevated temperature and a cover of roughly 1 to 2 km of sediments roughly 1 to 2 km of sediments

Most of the ocean bottom, roughly 90% or even Most of the ocean bottom, roughly 90% or even 90%, offers no chances for exploration because it 90%, offers no chances for exploration because it is too young and the sediment carpet is too thin is too young and the sediment carpet is too thin

The The most promising prospects for petroleum most promising prospects for petroleum concentrations are continental shelves and concentrations are continental shelves and slopesslopes, and small ocean basins with thick , and small ocean basins with thick sediments produced by high accumulation rates sediments produced by high accumulation rates and which are rich in organic matter. and which are rich in organic matter.

Fig.10.5 Regions where Cenozoic Sediments are well over 1 km thick. Only areas where source beds are deeply buried will produce petroleum (see Fig.10.1).

Fig.10.6 Schematic section through the Baltimore Canyon Trough off New Jersey. Based on seismic profiles by the US Geological Survey. In the center, the "Great Stone Dome", probably and area of volcanic sills and dykes, intruding the sedimentary sequence. The oceanic/continental crust boundary is highly speculative

10.3 Raw Materials from shelves 10.3 Raw Materials from shelves 10.3.1 Phosphorites 10.3.1 Phosphorites

It is commonly found in shallow sea floor, belIt is commonly found in shallow sea floor, below former or present regions of ow former or present regions of upwellingupwelling. .

It is both of It is both of biogenicbiogenic origin (phosphatic hard p origin (phosphatic hard parts such as fish debris and crustacean carapacarts such as fish debris and crustacean carapaces), and of es), and of hydrogenoushydrogenous origin (replacement of origin (replacement of calcium carbonate, precipitation from interstiticalcium carbonate, precipitation from interstitial waters). al waters).

Weathering processes on land concentrate PWeathering processes on land concentrate P22OO55

up to 30% to 40%. up to 30% to 40%.

Distribution of phosphorites

Fig.10.7 Phosphorites. Circles Shelf phosphorites 1 Holocene 2 late Tertiary 3 early Tertiary 4 Cretaceous; Triangles sea  mount phosphorites 5 late Tertiary 6 early Tertiary 7 Cretaceous. Continental phosphate deposits: A Precambrium; B Paleozoic: C Jurassic to Lower Cretaceous:  D Senon to Eocene; E Miocene to Pleistocene.

10.3.2 Shell Deposits 10.3.2 Shell Deposits Calcareous shell deposits were or are Calcareous shell deposits were or are

dredged in places as raw material for dredged in places as raw material for calcium carbonate. calcium carbonate.

coquinacoquina

10.3.3 Placer Deposits 10.3.3 Placer Deposits

Concentrations of heavy minerals and ore partiConcentrations of heavy minerals and ore particles on beaches and in estuaries are locally micles on beaches and in estuaries are locally mined for metals such as ned for metals such as titanium, gold, platinutitanium, gold, platinum, thorium, zirconiumm, thorium, zirconium, and valuable minerals , and valuable minerals such as such as diamonddiamond. .

Diamond, Magnetite, gold, ilmenite (FeTiODiamond, Magnetite, gold, ilmenite (FeTiO33), ),

platinum, chromite, titanium minerals. platinum, chromite, titanium minerals.

How do placers originate? How do placers originate? Water motion works on the Water motion works on the different settlingdifferent settling velocitie velocitie

s of the particles and on their different sizes, to separas of the particles and on their different sizes, to separate heavy from light, large from small. te heavy from light, large from small.

Terrigenous beach sands commonly consist of more tTerrigenous beach sands commonly consist of more than 95% quartz, tropical ones of calcareous grains. han 95% quartz, tropical ones of calcareous grains.

Volcanic rocks and other igneous sources supply minVolcanic rocks and other igneous sources supply minerals which are considerably heavier than quartz or caerals which are considerably heavier than quartz or calcite (density of 2.65 and 2.70). lcite (density of 2.65 and 2.70).

These minerals have densities of greater than 2.85 g/cThese minerals have densities of greater than 2.85 g/cm3. m3.

The back-and forth of the waves washing over the beThe back-and forth of the waves washing over the beach face can concentrate them greatly ach face can concentrate them greatly

Fig.10.8 A-D. Origin of heavy mineral placers, schematic.

A Suspended sediment particles are washed onshore, settle to the floor, large and heavy ones (shown solid) first.

B Resulting grain association shows enrichment of large and  heavy particles on the beach face.

C Backwash roll away large particle (greater velocity away from sediment interface. V, to the right).

D Resulting association consists of medium-size, well-sorted heavy minerals.

Fig.10.9 Beach placers. The beach south of Quilon (SW India) has a heavy mineral deposit on the top part (where the boat rests). During SW monsoon, High waves sort the sand as shown in Fig.10.8, and produce layers of "black sand" (inset). The inset profile is 20cm high.[Photo E. S.]

Ilmenite (iron-titanium oxide), rutile (titanium oxide), zircon (zircIlmenite (iron-titanium oxide), rutile (titanium oxide), zircon (zirconium silicate), monazite (phosphate, containing cerium and thorionium silicate), monazite (phosphate, containing cerium and thorium). um).

River deposits may contain heavy mineral concentrations. River deposits may contain heavy mineral concentrations.

Cassiterite (SnPCassiterite (SnP22) in ) in Thailand, Malaysia, Thailand, Malaysia, or Indonesia. or Indonesia.

10.4 Heavy Metals on the Deep Sea Floor 10.4 Heavy Metals on the Deep Sea Floor 10.4.1 Importance of Manganese Deposits 10.4.1 Importance of Manganese Deposits

The rich metal deposits on the deep sea floor The rich metal deposits on the deep sea floor have been a favorite topic of discussion among have been a favorite topic of discussion among marine geologists ever since the marine geologists ever since the manganese manganese nodulesnodules (better; (better; ferromanganese concretionsferromanganese concretions) ) were discovered by the Challenger Expedition. were discovered by the Challenger Expedition.

Shown to be rich in Shown to be rich in copper, cobalt, nickelcopper, cobalt, nickel and and other heavy metals. other heavy metals.

The origin; still unexplained The origin; still unexplained

Fig.10.10 A, B. Manganese nodules. A View (~ 10 ㎡ ) of nodule-covered deep sea floor, central tropical Pacific (Photo Metallgesellschaft Frankfurk).

B Manganese nodules recovered on Challenger stations in the Central Pacific. a Nodule with upper smooth and lower uneven surface (Station 274, 5000m); b Sliced section (parallel to the sea bottom) showing internal layering and nuclei (Station 254, 57000m).

Manganese depositsManganese deposits The abundances of The abundances of these metals in seawaterthese metals in seawater are are

extremely extremely lowlow, so that their geochemical cycles , so that their geochemical cycles cannot be followed by measuring concentration cannot be followed by measuring concentration changes in seawater. changes in seawater.

Instead, their distributions have to be mapped on Instead, their distributions have to be mapped on the seafloor, and in the interstitial waters, to the seafloor, and in the interstitial waters, to obtain clues about their sources and paths of obtain clues about their sources and paths of migration. migration.

Pacific ocean floor; 100 to 200 billion tons Pacific ocean floor; 100 to 200 billion tons Too expensive; a potential value Too expensive; a potential value

10.4.2 Nature of Manganese Deposits 10.4.2 Nature of Manganese Deposits The appearance of the manganese deposits The appearance of the manganese deposits

varies. varies. Nodule come in sizes of 1 to 10cm. Nodule come in sizes of 1 to 10cm. Black Black The surface can be smooth or rough. The surface can be smooth or rough. Not all deposits are nodules: some are crusts Not all deposits are nodules: some are crusts

several centimeters thick, others are pavements several centimeters thick, others are pavements covering the sea floor in areas of active covering the sea floor in areas of active currents. currents.

The nodules are rather porous. The nodules are rather porous.

NatureNature On cutting nodules, one notes a On cutting nodules, one notes a

concentric structure. concentric structure. A core of altered volcanic material. A core of altered volcanic material. Fragments of older nodules, bones, or Fragments of older nodules, bones, or

shark teeth also can serve as core. shark teeth also can serve as core.

Fig.10.11 Areas from which ferromanganese concretions have been reported. The richest areas are in the north-equatorial Pacific.

The manganese nodules occur in areas of The manganese nodules occur in areas of low sedimentation rate. low sedimentation rate.

Sedimentation rate controls…Sedimentation rate controls… Because of their slow growth they would soon be Because of their slow growth they would soon be

covered up in regions of high sediment supply. covered up in regions of high sediment supply. Calcareous ooze accumulates at about 10 m per Calcareous ooze accumulates at about 10 m per

million years, 1000 to 10000x faster than million years, 1000 to 10000x faster than nodules; hence no nodules develop. nodules; hence no nodules develop.

Brown pelagic clay (Red Clay) accumulates at Brown pelagic clay (Red Clay) accumulates at less than 1 m, up to about 2,5m, per million less than 1 m, up to about 2,5m, per million years, the higher values applying in the Atlantic years, the higher values applying in the Atlantic Ocean. Ocean.

Surprisingly, nodules have time to grow at the Surprisingly, nodules have time to grow at the surface under these conditions. surface under these conditions.

Patchy Distribution …Patchy Distribution … The distribution of nodules is patchy. The distribution of nodules is patchy. The reasons for patchiness are not The reasons for patchiness are not

clearclear In part it may be due to alternating In part it may be due to alternating

burial and uncovering of nodules burial and uncovering of nodules below slowly moving clay carpets, below slowly moving clay carpets, somewhat akin to dune migration. somewhat akin to dune migration.

10.4 Origin of Manganese Nodules 10.4 Origin of Manganese Nodules How manganese nodules originate is not agreed upon. How manganese nodules originate is not agreed upon.

Questions about the origin of ferromanganese concretions. Questions about the origin of ferromanganese concretions. 1) the ultimate source - for example, weathering of 1) the ultimate source - for example, weathering of

continental or oceanic rocks or sediments or exhalations continental or oceanic rocks or sediments or exhalations from volcanic or hydrothermal vents. from volcanic or hydrothermal vents.

2) The immediate source, that is, the surrounding seawater 2) The immediate source, that is, the surrounding seawater or the mobilization of ferromanganese and other metals or the mobilization of ferromanganese and other metals (by reduction) within sediments and diffusion to the (by reduction) within sediments and diffusion to the interface. interface.

3) The mode of extraction from the source; for example, 3) The mode of extraction from the source; for example, differential weathering or hydrothermal reactions. differential weathering or hydrothermal reactions.

Origin of Manganese NodulesOrigin of Manganese Nodules4) The mode of transport into the ocean - that is, whether 4) The mode of transport into the ocean - that is, whether

delivery is as solute, mineral, or coating on mineral. delivery is as solute, mineral, or coating on mineral. 5) The transport and migration processes within the ocean 5) The transport and migration processes within the ocean

– i.e., the question of how ferromanganese gets to its pl– i.e., the question of how ferromanganese gets to its place of deposition, as colloid or other suspensate, in soluace of deposition, as colloid or other suspensate, in solution, or locked up in organic matter and plankton shells. tion, or locked up in organic matter and plankton shells.

6) The physicochemical and biochemical methods of preci6) The physicochemical and biochemical methods of precipitation and their variation through time. pitation and their variation through time.

7) The processes of redeposition, physical and chemical, i7) The processes of redeposition, physical and chemical, including movement of nodules, scouring of paved sea flncluding movement of nodules, scouring of paved sea floor, as well as dissolution and reprecipitation of ferromoor, as well as dissolution and reprecipitation of ferromanganese. anganese.

Origin of Manganese NodulesOrigin of Manganese Nodules

The problem is that we do not know what to expect, aThe problem is that we do not know what to expect, and to what degree the distributions depend on the ultind to what degree the distributions depend on the ultimate origin at all. mate origin at all.

There is, however, an unusually There is, however, an unusually high ratehigh rate of sediment of sedimentation of (disseminated) iron and manganese in the ation of (disseminated) iron and manganese in the regregion of the East Pacific Riseion of the East Pacific Rise, centered on the crest. , centered on the crest.

This suggests that input of Fe and Mn from the This suggests that input of Fe and Mn from the hydrohydrothermal activitythermal activity at the crest is indeed important. at the crest is indeed important.

Note that the Note that the Mn/Fe ratio is greater in the PacificMn/Fe ratio is greater in the Pacific than than in the Atlantic. in the Atlantic.

Also, the content of trace elements in Pacific nodules, Also, the content of trace elements in Pacific nodules, on average, is about twice that of Atlantic ones. on average, is about twice that of Atlantic ones.

The The Mn/Fe ratio increases with the degree of oxidatioMn/Fe ratio increases with the degree of oxidation and with depthn and with depth - the more "deep sea" character the n - the more "deep sea" character the nodules have, the more manganese they contain. odules have, the more manganese they contain.

Shallow water ferromanganese concretions are generaShallow water ferromanganese concretions are generally iron-rich. lly iron-rich.

High manganese content appears to be favored by botHigh manganese content appears to be favored by both high biogenous sediment supply and low rates of ach high biogenous sediment supply and low rates of accumulation. cumulation.

Under these conditions, presumably, the carrier materUnder these conditions, presumably, the carrier material dissolved but leaves its content of trace elements. ial dissolved but leaves its content of trace elements.

Also, in the "manganese zone" in the Pacific, tAlso, in the "manganese zone" in the Pacific, the underlying sea floor consists of dissolving bhe underlying sea floor consists of dissolving biogenous sediment rich in trace metals. iogenous sediment rich in trace metals.

The sediment was originally formed underneatThe sediment was originally formed underneath the Equator, then moved northward and dowh the Equator, then moved northward and downward due to plate motion. nward due to plate motion.

This motion brought the calcareous sediment fThis motion brought the calcareous sediment from a zone of accumulation into a zone of dissrom a zone of accumulation into a zone of dissolution. olution.

Thus, one way to concentrate manganese and tThus, one way to concentrate manganese and trace elements is to have organisms precipitate race elements is to have organisms precipitate the metals, bring them to the sea floor in shells the metals, bring them to the sea floor in shells and fecal matter, and dissolve or oxidize these and fecal matter, and dissolve or oxidize these carriers to obtain a more nearly pure concentracarriers to obtain a more nearly pure concentrate. te.

10.4.4 Ores from Spreading 10.4.4 Ores from Spreading Ridge Crest Ridge Crest OresOres: East Pacific Rise. : East Pacific Rise.

While hydrothermal reactions undoubtedly play a role While hydrothermal reactions undoubtedly play a role in producing metalliferous sediments on top of the Easin producing metalliferous sediments on top of the East Pacific Rise, the process of enrichment with heavy mt Pacific Rise, the process of enrichment with heavy metals other than iron is still poorly understood. etals other than iron is still poorly understood.

Many elemental and isotopic ratios within the deposits Many elemental and isotopic ratios within the deposits are similar to those in seawater and in deposits from nare similar to those in seawater and in deposits from non-Ridge areas. on-Ridge areas.

Just how much of the material is delivered from the baJust how much of the material is delivered from the basalt, how much from seawater? salt, how much from seawater?

One possibility is that part of the metal enrichment on One possibility is that part of the metal enrichment on the East Pacific Rise - especially the very high iron cothe East Pacific Rise - especially the very high iron content - is derived from hydrothermal activity, while thntent - is derived from hydrothermal activity, while the rest is scavenged by the freshly formed hydroxide. e rest is scavenged by the freshly formed hydroxide.

Fig.10.12 Hydrothermal circulation model for a sediment-starved spreading ridge. The more important factors for reactions between seawater and hydrothermal fluids are illustrated. In addition, precipitates near vents act as scavengers - as iron oxides do for vanadium.

Fig.10.13 " La Dame Blanche", a chimney made of anhydrite at an active hydrothermal site with fluids of 285 ℃and active animal colonies. North Fiji Basin axis, 1900 m water depth.

10.4.5 Red Sea Ore Deposits 10.4.5 Red Sea Ore Deposits In the central Red Sea, there are several enclosed In the central Red Sea, there are several enclosed

basins, the "deeps" basins, the "deeps" The Atlantic II Deep is more than 2000m deep, The Atlantic II Deep is more than 2000m deep,

and only 6 by 15 km in area. and only 6 by 15 km in area. The bottom is filled with a hot salt brine with a The bottom is filled with a hot salt brine with a

temperature of about 60 and a salinity of 25%, ℃temperature of about 60 and a salinity of 25%, ℃seven times that of seawater.  seven times that of seawater. 

Iron is 8000 times more concentrated in the brine Iron is 8000 times more concentrated in the brine than in seawater, zinc 500 times, copper 100 times. than in seawater, zinc 500 times, copper 100 times.

A variety of minerals; A variety of minerals; sulfidessulfides

How did these deposits originate? How did these deposits originate?

Two kinds of processesTwo kinds of processes We are here in the volcanic region, that is, the axis of We are here in the volcanic region, that is, the axis of

a spreading center.  Basaltic lavas form the basement, a spreading center.  Basaltic lavas form the basement, and temperatures increase rapidly downward.  Hot, mand temperatures increase rapidly downward.  Hot, metalliferous solutions may develop from reactions of setalliferous solutions may develop from reactions of seawater with the fresh basalt. eawater with the fresh basalt.

Thick sedimentary deposits of Tertiary age are nearbThick sedimentary deposits of Tertiary age are nearby, abutting against the newly forming sea floor. These y, abutting against the newly forming sea floor. These contain several-hundred-meter-thick salt and gypsum contain several-hundred-meter-thick salt and gypsum layers.  Hot water circulating through such sediments layers.  Hot water circulating through such sediments can dissolve out metals and salt and hence produce mcan dissolve out metals and salt and hence produce metalliferous brine issuing into the brine pools. etalliferous brine issuing into the brine pools.

10.5 Waste Dispersal and Pollution10.5 Waste Dispersal and Pollution10.5.1 A change in pace10.5.1 A change in pace

The increased delivery of sediments to The increased delivery of sediments to estuaries and harbors caused by increased estuaries and harbors caused by increased erosion on land from working the soil and erosion on land from working the soil and from deforestationfrom deforestation

This should accelerate the filling-in of This should accelerate the filling-in of estuaries and affected lagoons.estuaries and affected lagoons.

Conversely, the building of large dams upriver Conversely, the building of large dams upriver has led to interception of sediments, and the has led to interception of sediments, and the starvation of beaches, which promotes the starvation of beaches, which promotes the erosion of coastline.erosion of coastline.

A massive increase of waste off rapidly A massive increase of waste off rapidly growing cities; source of pollutiongrowing cities; source of pollution

Dangerous level of pathogenic bacteriaDangerous level of pathogenic bacteria Bursts of growth (blooms) of noxious dinoflagBursts of growth (blooms) of noxious dinoflag

ellatesellates Potent and long-lived industrial poisons at low Potent and long-lived industrial poisons at low

concentrationsconcentrations Oil spills and the introduction of radioacitive Oil spills and the introduction of radioacitive

materialsmaterials

Fig.10.14 Benthic biota changed drastically between 1951/52 and 1985 in the Central North Sea (Doggerbank about 20m waterdepth). Mussels and sea urchins were increasingly replaced by the less sensitive brittle stars and worms. This type of monitoring is useful in identifying change in stressed environments.

How can we monitor environmental How can we monitor environmental changes and detect possible causes?changes and detect possible causes?

Biological Biological monitoringmonitoring

10.5.2 Sewage and Sludge10.5.2 Sewage and Sludge Industrial man produces waste; Industrial man produces waste;

sewage sludgesewage sludge The amount introduced must not The amount introduced must not

exceed what the ocean can absorbed exceed what the ocean can absorbed by dilution and bacterial action.by dilution and bacterial action.

Under these conditions sludge mainly Under these conditions sludge mainly acts as fertilizer.acts as fertilizer.

When dumping of sludge proceeds on a When dumping of sludge proceeds on a grand scale in a limited area, problems arise.grand scale in a limited area, problems arise.

Diseased benthic organisms; lobster fishing is adDiseased benthic organisms; lobster fishing is adversely affectedversely affected

Even deep dumping can cause problems; affecteEven deep dumping can cause problems; affected benthic food webd benthic food web

Much greater problems in confined water bodiesMuch greater problems in confined water bodies The influx of sewage and agricultural fertilizer rThe influx of sewage and agricultural fertilizer r

esults in large-scale eutrophication; a shortage oesults in large-scale eutrophication; a shortage of oxygen; massive fish killing f oxygen; massive fish killing

Where sewage contains dangerous Where sewage contains dangerous bacteria and where solids settle out in bacteria and where solids settle out in bays close to cities…bays close to cities…

Stirring up such material by stormsStirring up such material by storms Fouling of heavily used recreational areasFouling of heavily used recreational areas A prime example is the MediterraneanA prime example is the Mediterranean Up to 25% of coastal waters is unfit for Up to 25% of coastal waters is unfit for

swimming.swimming.

10.5.3 Oil Spills10.5.3 Oil Spills High media visibilityHigh media visibility In most cases, however, even In most cases, however, even

massive spills have had limited massive spills have had limited impact in terms of area and impact in terms of area and time period.time period.

10.5.4 Chronic Hydrocarbon Pollution10.5.4 Chronic Hydrocarbon Pollution

The steady leakage from shipping and The steady leakage from shipping and other industrial activities receives much other industrial activities receives much less attentionless attention

In 1985, the annual petroleum input to the In 1985, the annual petroleum input to the sea was estimated to reach about 3 million sea was estimated to reach about 3 million tons – with 12.5% of it from tanker tons – with 12.5% of it from tanker accident.accident.

Additional risks arise from the operation Additional risks arise from the operation of more than 600 offshore oil production of more than 600 offshore oil production platforms globally.platforms globally.

10.5.5 Radioactive Pollution10.5.5 Radioactive Pollution

The principal source of artificial radioThe principal source of artificial radionuclides used to be nuclear weapon-tesnuclides used to be nuclear weapon-testing.ting.

This source produced a very low-level This source produced a very low-level contamination with no obvious ill effecontamination with no obvious ill effects.cts.

High-level radioactive wasteHigh-level radioactive wasteFig.10.15 Investigation  of risks associated with sub-seabed disposal of high-level nuclear waste. The diagram shows hypothetical pathways of contaminants from postulated leaks from waste repositories. These pathway (and others) have to be assessed before subsea disposal con be considered as low-risk option. vitrification lf canister packages, circulation driven by high temperatures generated by radiation, diffusion through sediments of erosion by deep-sea storms, all these might provide for escape in to bottom waters and uptake by benthic organisms, resulting in physical of biological transport to surface waters.

EpilogEpilog

Fig.E.1 Major components of the climate system and central role of the ocean as mediator between the various elements