1. Nutrient Cycles in Marine Ecosystems

2. Objectives
Inputs and outputs to the reservoir of dissolved nutrients. The biological uses of nutrients. Nutrient availability and productivity.

3. Nutrient: chemical that an organism needs to live and grow (or a substance used in an organisms metabolism) which must be taken from the environment

4. Demonstrate an understanding that there is a reservoir of nutrients dissolved in the surface layer of the ocean
Algae require light for photosynthesis.
Light intensity decreases as the depth of the ocean increases and therefore photosynthesis is restricted to a surface layer in which there is sufficient light.
This layer (referred to as the ‘photic zone’) varies in depth from about 30 m to 150 m, although it is considerably less is turbid water.

6. Demonstrate an understanding that there is a reservoir of nutrients dissolved in the surface layer of the ocean

7. Demonstrate an understanding that there is a reservoir of nutrients dissolved in the surface layer of the ocean
The surface layer of the ocean contains many different ions, some of which are shown below

8. Nitrate and phosphate ions occur at low concentrations in seawater;
Demonstrate an understanding that there is a reservoir of nutrients dissolved in the surface layer of the ocean
These ions, together with nitrate and phosphate ions, form a reservoir of nutrients for the growth of algae and other primary producers.
Nitrate and phosphate ions occur at low concentrations in seawater;
the mean concentration of nitrate is 0.5 parts per million (ppm)
the mean concentration of phosphate in seawater is 0.07 ppm.

10. The Sea-Surface Microlayer
incredibly thin (few hundred µm)
important for the chemistry of the ocean
covers 71% of surface of the planet – therefore it is the largest single ecosystem
not well understood (difficult to sample such a tiny vertical section of the water column)
critical link between ocean and atmosphere

11. Receives and transmits
Energy/gases/solids
Collects matter transported by winds from above and by water below

12. The Sea-Surface Microlayer
Especially dense concentration of minerals, organic chemicals, protozoans and micro-organisms.
Upper 70 mm has dense concentrations of slightly larger organisms, including fish eggs, fish larvae, and crustaceans. Larger, floating jellyfish and seaweeds are found in the upper 30 cm. There are many transient creatures that move up and down in tune to the sunlight.

13. The plants and animals that live in the water excrete many organic compounds, such as amino acids, proteins, and fatty acids that serve as nutrients for bacterial growth. These rise to the surface where they are concentrated the thin organic skin of the water. This happens in fresh water as well as salt water.
When aquatic organisms die, the oils in their bodies may float to the surface before they completely decompose.
The thin layer of oily material on the surface of the sea is an important part of the water cycle as it helps control the rate of evaporation. It is also a highly nutritious food source for many species of microscopic plants and animals (ie plankton).

14. The Sea-Surface Microlayer
Wind pushes the oil into long ribbons of calm water known as "wind slicks" or "wind rows."
You can see these on most days when looking at the sea from an overlook or from a boat.
Samples show the plankton and nutrients are thousands of times more concentrated in the windrows than in water only a few cm deeper or in adjacent areas.
Unfortunately, the oily surface of the sea is also the first to receive pollutants from the atmosphere. Scientists believe more than 30 per cent of all ocean pollution comes from tiny particles of dust and smoke in the air - often called fallout.
This settles on the most sensitive and vulnerable part of the ocean - its skin.
The pollutants contain pesticides, heavy metals, and industrial and motor vehicle toxins such as sulphuric acid, chlorine, and dioxin.

15. Wind Slicks
Windslick research link

16. The Sea-Surface Microlayer
A polluted surface microlayer has the potential to poison much of the complex marine food web, including fish, crustaceans, whales, and seabirds.
Destruction of the microlayer may alter the exchange of materials between the atmosphere and the ocean, thereby affecting global climate.
Oil pollution also floats on the surface of the sea and quickly contaminates this fragile environment with chemical toxins.
Oil, even a very thin layer, spreading over the surface of the water at the same time fish are releasing their floating eggs can devastate their reproductive success

17. The Sea-Surface Microlayer
Heavy metals, and other toxins, are hundreds of times more concentrated in the surface windrows of the sea than in deeper water. Pesticides are found concentrated millions of times greater than in the rest of the water.
As the ozone layer in the upper atmosphere breaks down from air pollution, ultraviolet radiation increases. This has been shown to have a severe impact on the phytoplankton and the eggs of sea creatures when they concentrate at the surface.

18. Explain the process by which the reservoir of dissolved nutrients is replenished, including upwelling from land and dissolving atmospheric gases.
Upwelling is the movement of water from deep in the ocean to the surface layer, where the nutrients become available to primary producers.
brought about by several processes including the deflection of deep water currents upwards and the movement of water away from a coast by the action of wind.

19. Upwelling refers to deep water that is brought to the surface.
Areas of upwelling are created by surface winds that pull water away from an area. This deficit of water on the surface invites water to come up from deeper regions.

21. Explain the process by which the reservoir of dissolved nutrients is replenished, including upwelling, runoff from the land, and dissolving of atmospheric gases
Upwelling is the movement of water from deep in the ocean to the surface layer, where the nutrients become available to primary producers
Upwelling brought about by several processes
Deflection of deep water currents upwards
Movement of water away from the coast (due to wind)
Upwelling Animation

22. Mechanisms that create ocean upwelling
Wind
Coriolis Effect
Ekman Transport

23. Due to friction between the layers of water in the ocean and the Coriolis Effect, the net result of wind blowing across the surface of the water is transportation of a layer of water 90 degrees to the direction of the wind. This is known as Ekman Transport.

24. To understand upwelling, you must be familiar with how the Coriolis Force affects ocean surface currents. The Coriolis Effect acts on moving water, because it is not attached to the rotating Earth. As water flows over the rotating earth, it appears to deflect to the right in the Northern Hemisphere and the left in the Southern.

25. Coriolis Effect link
Coriolis Video

27. Seasonal upwelling
Wind
Wind
Onshore winds pile water up on shore, thus surface water will be forced downward. This is ‘downwelling’.
Offshore winds take water away from shore, thus water from depth will upwell to the surface.

28. Even though upwelling areas account for only 1% of the ocean surface, they support 50% of the worlds fisheries.

29. Productivity (phytoplankton growth) of an area is determined by the rate and the duration of upwelling.
Rate of upwelling determines phytoplankton cell size.
Duration of upwelling determines the total amount of phytoplankton.
small vs. large
few vs. many

30. -Moderate rates of upwelling for long duration (8 months or longer) provide the ultimate combination for a large fishery.
-With too low or too high a rate, phytoplankton are small, so there is a trophic level between the algae and the fish….therefore the fish receive less energy.

31. Classification of upwelling systems in terms of rate and duration:
Low Medium High
RATE
DURATION
Long Short
After Thurman, H.V. (1994)

32. Explain the process by which the reservoir of dissolved nutrients is replenished, including upwelling from land and dissolving atmospheric gases.
Run-off from the land is part of the hydrological cycle and the water may leach nutrients, including nitrates and phosphates, from the soil.
Carbon dioxide in the atmosphere dissolves in seawater forming hydrogen carbonate ions (HCO3–), making carbon dioxide available for fixation in the process of photosynthesis, by primary producers.

33. Show that each of the nutrient cycles listed below can be summarized as shown in Fig 4.1 and state the biological use of each nutrient
nitrogen: which is used to make proteins
carbon: which is used to make all organic materials
magnesium: which is used to make chlorophyll
calcium: which is used to make bones, corals, and shells
phosphorous: which is used to make DNA and bone

34. Figure 4.1 summarizes the ways in nutrients are cycled in marine ecosystems. Nutrients may be derived from both land and the atmosphere, forming a reservoir in the surface layer of the sea.
From here, nutrients are taken up by living organisms and incorporated into food chains. Nutrients may be removed by harvesting, sinking to the sea bed, or incorporation into coral reefs. Nutrients from the sea bed may be returned to the surface layer of the sea by the process of upwelling.

36. Biological
Processes
Geological
Ecology

37. The Carbon Cycle Key role in Earth’s thermostat
Absorbed by ocean, utilized by plants in photosynthesis, humans in digestion
Sinks (storage) in lithosphere (largest reservoir – limestone and other sedimentary rock), hydrosphere (ocean), atmosphere (CO2) and in the biosphere (dead animals, wood, plants…)
Released by fires, decomposition, volcanoes, and human respiration

39. The Oxygen Cycle Essential for animals Taken in during respiration
Released by plants in photosynthesis
Disrupted by the same factors that disrupt the carbon cycle
Clear cutting of trees
Increased burning of fossil fuels
Pollution to phytoplankton containing water

40. The Nitrogen Cycle
78% of troposphere is N2, 0% utilized in respiration
Present in proteins, moves through food chain
Most complex cycle
Disrupted by
Burning fuel (releases nitric oxides)
Increased use of fertilizer
Removal from topsoil
Addition to aquatic ecosystems

41. Nitrogen Cycle
N2 gas is modified by nitrogen fixing bacteria into ammonia (NH3) (nitrogen fixation)
Bacteria turn nitrogenous waste and detritus into ammonia (ammonification)
NH3 is converted into nitrite (N02) which is used to produce nitrate (N03) (nitrification)
Other bacteria convert nitrite into gas which enters the air (denitrification)

43. The Phosphorous Cycle Very slow process
Found only in sedimentary rocks and water (not in atmosphere)
Released as rocks erode
Travels through food chain
Released by decomposition

45. The Sulfur Cycle Most stored underground
Released by volcanoes and swamps
Plants assimilate the sulfur
Bacteria break it down
99% of all that reaches atmosphere is by humans (industries, burning fuel, refining petroleum)

49. Explain the process by which the reservoir of dissolved nutrients is replenished, including upwelling from land and dissolving atmospheric gases.
Atmospheric nitrogen gas is fixed by blue-green algae in Intertidal zones, resulting in the formation of nitrogen-containing organic compounds. In this way, nitrogen can enter marine ecosystems.

50. Explain the process by which the reservoir of dissolved nutrients is replenished, including upwelling from land and dissolving atmospheric gases
Some nutrients, including nitrates and phosphates are also recycled in the surface layer of the ocean as a result of excretion from zooplankton.

51. Demonstrate an understanding that the reservoir of dissolved nutrients is depleted by uptake into organisms in food chains.
One of the ways in which nutrients are removed from the surface waters of an ocean is by their uptake by primary producers, (phytoplankton) and their use for the synthesis of organic substances.
EX, nitrate ions are used in the synthesis of amino acids and proteins. If the phytoplankton is eaten by zooplankton, the proteins will pass to the next trophic level.
Zooplankton may subsequently be eaten by small fish and, in this way, nutrients are passed along a food chain.

53. Explain how productivity may be limited by the availability of dissolved nutrients.
Inorganic nutrients, such as nitrate ions and phosphate ions are essential for the growth of primary producers. Since consumers depend on these primary producers for food, either directly on indirectly in food chains, the productivity of the primary producers will influence the productivity of higher trophic levels. In water where the nutrient levels are high, for example as a result of upwelling, the productivity is correspondingly high. One of the most productive ecosystems is the Benguela upwelling system, off the west coast of southern Africa.

54. Phytoplankton photosynthesize using specialized color pigments called chlorophyll. Thus, “Ocean Color” maps are another way to identify areas of upwelling. Where on this ocean color map are high phytoplankton concentrations?

55. Demonstrate an understanding that the nutrients taken up by organisms in food chains may sink to the sea floor in faeces or after death, may be incorporated into coral reefs, or may be removed by harvesting
Detritus (decaying organic materials), feces and dead organisms may gradually sink to the sea floor. This represents a loss of nutrients from the surface water. In deep water, these nutrients will tend to remain on the ocean floor, unless returned to surface waters by upwelling.
The growth of corals involves the deposition of calcium carbonate; this represents another way in which nutrients may be removed from water.
Harvesting fish and other marine organisms, also results in the loss of nutrients from marine ecosystems.

57. Stormwater Runoff
the most common pollutant of streams, rivers, and oceans.
Stormwater runoff is the rain or snowmelt that flows over streets, parking lots, parks, as well as agricultural and urban areas, into a water body.
By the end of the workshop we hope that
You will have a better understanding about the sources and impacts of stormwater pollution.
You will know more how your actions can affect stormwater pollution.
You will be motivated to seek and share information with others.
I will be speaking about actions that not only you can take, but that you can also tell your neighbor about.
Introductions
Picture courtesy of Microsoft ClipArt

59. Demonstrate an understanding that the reservoir of dissolved nutrients is depleted by uptake into organisms in food chains

61. General Marine Productivity
Primary production is the total amount of carbon (C) in grams converted into organic material per square meter of sea surface per year (gm C/m2/yr).
Factors that limit plant growth and reduce primary production include solar radiation and nutrients as major factors and upwelling, turbulence, grazing intensity and turbidity as secondary factors.
Only 0.1 to 0.2% of the solar radiation is employed for photosynthesis and its energy stored in organic compounds.

62. Macronutrients and micronutrients are chemicals needed for survival, growth and reproduction in large and small quantities, respectively.
Upwelling and turbulence return nutrients to the surface.
Overgrazing of autotrophs depletes the population and leads to a decline in productivity.
Turbidity reduces the depth of light penetration and restricts productivity even if nutrients are abundant.

63. Productivity varies greatly in different parts of the ocean in response to the availability of nutrients and sunlight.
In the tropics and subtropics sunlight is abundant, but it generates a strong thermocline that restricts upwelling of nutrients and results in lower productivity.
High productivity locally occurs in areas of coastal upwelling, in the tropical waters between the gyres, and in coral reefs.

64. In temperate regions productivity is distinctly seasonal.
Polar waters are nutrient-rich all year but productivity is only high in the summer when light is abundant.

65. Variations in Primary Productivity

66. Mixing plays an important role in the limitation of primary production by nutrients.
Inorganic nutrients, such as nitrate, phosphate, and silicate acid are necessary for phytoplankton to synthesize their cells and cellular machinery.
Because of gravitational sinking of particulate material (such as plankton, dead or fecal material), nutrients are constantly lost from the photic zone, and are only replenished by mixing or upwelling of deeper water.
Summer: increased solar heating, reduced winds leads to vertical stratification (thermocline) – which makes it more difficult for upwellings

67. Mixing plays an important role in the limitation of primary production by nutrients.
Between mixing events, primary production (and the resulting processes that leads to sinking particulate material) constantly acts to consume nutrients in the mixed layer
In many regions, this leads to nutrient exhaustion and decreased mixed layer production in the summer
Even in the presence of abundant light – not always a limiting factor!
As long as the photic zone is deep enough, primary production may continue below the mixed layer where light-limited growth rates mean that nutrients are often more abundant

68. Primary productivity varies from 25 to 1250 gm C/m2/yr in the marine environment and is highest in estuaries and lowest in the open ocean.
In the open ocean primary productivity distribution resembles a “bull’s eye“ pattern with lowest productivity in the center and highest at the edge of the basin.
Water in the center of the ocean is a clear blue because it is an area of downwelling, above a strong thermocline and is almost devoid of biological activity.

69. Continental shelves display moderate productivity between 50 and 200 gm C/m2/yr because nutrients wash in from the land, and tide- and wave- generated turbulence recycle nutrients from the bottom water.
Polar areas have high productivity because there is no pycnocline to inhibit mixing.
Equatorial waters have high productivity because of upwelling.
Centers of circulation gyres, which occupy most of the open ocean, are biological deserts.

70. The Sargasso Sea and Vertical Profiles

71. Remember….
Although rate of productivity is very low for the open ocean compared to areas of upwelling, the open ocean has the greatest biomass productivity because of its enormous size.

72. DETRIVORES AND DETRITUS
Some heterotrophs (e.g., earthworms, flies, beetles, crabs, sea cucumbers, ants, vultures, hyenas, etc.) depend on detritus (dead organic material/biomass), rather than live organic material.
Note: animals can be both a herbivore and a detrivore, or a carnivore or omnivore and a detrivore, i.e., they eat both living and dead organisms.

73. DECOMPOSERS
Decomposers play a very important role in mineralisation by breaking down organic substances into inorganic compounds that are again available for reuse by producers.