Plankton in the Sea (M.Sc (1). course) Autumn 2017-2018 for students.ppt
1. Plankton
in the Sea
A part of the course “ Marine Biology”
for M. Sc.
Professor Mohamed M.
Dorgham
Oceanography Department
Faculty of Science
2. Plankton
in the Sea
A part of the course “ Advanced Marine Biology”
MS 701
for M.Sc. Degree
Professor Dr. Mohamed M. Dorgham
Oceanography Department
Faculty of Science
Alexandria University
4. • 1- Why we study plankton?
• 2- Plankton composition
• 3- Plankton importance
• 4- Plankton distribution
• 5- Factors affecting plankton distribution.
• 6- Water stability.
• 7- Plankton and climate changes.
• 8- Biogeochemical significance of plankton.
• 9- Global warming: causes and impacts.
Plankton in the Sea
Contents
5. Plankton in the Sea
• 10- Plankton indicators.
• 11- Iron Hypothesis.
• 12- Algal secretions.
• 13- Alien plankton species.
• 14- effect of ocean acidification on plankton
• new trends in plankton research
• 14- genetic mapping of plankton
6. What are plankton ?
• Plankton comprise drifting organisms (plants
and animals in the water mass which can not
move actively.
• Plankton include numerous forms in the oceans,
such as microbes (bacteria and viruses),
microscopic plants (phytoplankton) and animals
(zooplankton).
• Plankton exist everywhere in about 1.5 x109 km3
living space of the world’s ocean.
7. • The ocean’s food web depends crucially upon
plankton, since phytoplankton as simple
primary producers and zooplankton as
secondary producers form the functional base of
all marine ecosystems.
• Annual Primary production = 48 x 1015 tonnes C
(Field et al 1998)
= 240 million metric tonnes of fish.
• Give annually= 80 million metric tonnes of fish
through fisheries.
Why study plankton biodiversity?
14. The importance of phytoplankton can be summarized as
follows:
- A major source of oxygen,
- Primary producers of organic matter,
- Food for numerous marine animals and in aquaculture.
- their hard shells form bottom sediments (Diatoms,
Silicoflagellates, Coccolithophores)
- Play a role in climate change.
- Contain essential elements for sustaining life (Amino
acids, fatty acids (Omega 3 & 6), vitamins A,B,C,D ,
macro and trace minerals.
- Numerous species can be used in the biofuel production.
Plankton Importance
15. - Essential food for most of the economically important
fishes, and the whales in the northern hemisphere.
- An important link between the phytoplankton and
higher trophic levels such as fish.
- The fecal pellets of copepod contribute greatly in
accelerating the flow of nutrients from surface waters to
the bottom of the seas.
- Copepods constitute the biggest source of protein in
the oceans.
- Copepods can be used as bio-indicator water cleanness,
since some copepods consume tiny ocean particles, which
often contain toxins.
Plankton Importance
The zooplankton importance:
17. Plankton distribution
• Horizontal distribution
– Neritic
– Oceanic
• Vertical distribution
- Relative to light
- Relative to thermocline
18. The neritic area is usually shallow, where the action of wind,
waves, tides and current in mixing of sea water is clearly
observed. This mixing causes mostly more or less
homogeneity in the chemical characteristics of the water,
particularly the nutrient content. Due to the land-based
effluents from rivers, agricultural, industrial and domestic
origins salinities are usually lower, sometimes, markedly and
undergo seasonal or sporadic fluctuations. The shallowness of
water make the possibility of higher water temperature in the
neritic area and also its faster changes. The terrestrial
effluents may carry nutrients and exert a stabilizing influence
on the turbulent motion, being at times, therefore, instrumental
in initiating plant growth in the upper layers, where light
penetrates mostly to the bottom or near the bottom.
Plankton in the neritic area
19. Plant nutrients (nitrate, phosphate) and others are more readily
available in the shallower inshore water because of their
return to the surficial layers by vertical currents after they
have been regenerated from dead organisms on the bottom or
in the deeper water.
Therefore, the neritic province is far more productive than the
oceanic province and is consequently the region of greatest
economic importance to marine life in general. The neritic
plankton are mostly euryhaline and eurythermic forms, that is
able to endure wide ranges of salinity and temperature
variations. The primary productivity of neritic areas is some
ten times higher than adjacent oceanic waters.
Plankton in the neritic area
20. The oceanic waters, due to the great depths, are very
transparent, with little or no detritus of terrestrial origin. They
are mostly blue in color. The effective solar radiation is
restricted only to the euphotic zone, the depth of which varies
at different latitudes. The oceanic waters are characterized by a
relatively stable chemical composition. Salinity is uniformly
high, with only small fluctuations at different latitudes and
with times. The nutrient salts are generally relatively low in
the upper layer and only slowly replaced except at the
upwelling areas. Therefore, with the exception of the
upwelling areas, phytoplankton production is often low in the
oceanic waters, and the species are mostly stenohaline and
stenothermic.
Plankton in oceanic area
21. Although there is no distinct border between the neritic and
oceanic waters, each of which has it own planktonic species,
which are not found in the other, however, some species may
be observed in then mixing area. The neritic phytoplankton
often include benthic species which are brought up to the
plankton by the mixing processes.
Plankton in oceanic area
22. Horizontal distribution
Characteristics of neritic plankton
• Usually found in the coastal waters over the
continental shelf.
• Highly diversified
• Mostly eurythermic and euryhaline forms.
• Highly productive.
Plankton distribution
23. Horizontal distribution
Characteristics of oceanic plankton
• Found in the water mass that cover the
continental slope and the deep sea floor.
• Low diversified as compared to the neritic.
• Mostly stenothermic and stenohaline forms.
• Low productive, except at the upwelling
areas.
Plankton distribution
24. • Phytoplankton along the water column are
partly dependent on the stability of the water
column and the light attenuation.
• The phytoplankton may extend downwards
below the euphotic zone to the hypophotic
zone (light intensity 1% - 0.0001% at the
surface).
• Clear differences in the vertical distribution
of phytoplankton are observed at different
latitudes.
Plankton distribution
Vertical distribution
25. Vertical distribution of phytoplankton
The vertical distribution of phytoplankton along the water
column is partly dependent on the stability of the water
column and the light attenuation. Vertical mixing and the
depth of the euphotic zone vary markedly at the different
latitudes, and the factors affecting the vertical distribution of
phytoplankton crop showed significant regional differences.
In the Antarctic areas, the phytoplankton vertical distribution
showed pronouncedly areal differences.
In areas with temperature stratified waters, the phytoplankton
was so concentrated in the upper layers due to the strong
summer illumination near the surface.
While in areas with marked turbulence and vertical mixing
(no stratification), the phytoplankton was uniformly low
throughout the euphotic zone.
26. The phytoplankton distribution may exist below the euphotic
zone at light intensity between 1% - 0.0001% of the surface
light (hypophotic zone), that varies at different latitudes
relative to the depth of the euphotic zone.
The phytoplankton biomass in the euphotic zone is usually
greater than in the hypophotic zone, particularly in stratified
waters of open tropical areas.
-In mixed waters, the difference in chlorophyll between the
two zones is not great, particularly in temperate and high
latitudes zone, particularly in the open waters.
Vertical distribution of phytoplankton
27. Stratification is also observed in the vertical distribution of
different phytoplankton species, particularly in tropical areas,
where diatoms dominated in the uppermost 25-50m,
dinoflagellates occupied slightly deeper layers and
coccolithophores were reported mainly at the depth range 50-
100m and some species were found abundantly at 150m depth.
In most tropical and subtropical areas, the intense solar
radiation restrict phytoplankton production at the surface, and
the lack of vertical mixing generally in subtropical coastal seas
usually causes a reduction in production due to nutrient
restriction. In the areas with pycnocline light penetrates to the
water layers beneath them and give a chance for high primary
production in occurrence of sufficient nutrients in deeper
layer.
Vertical distribution of phytoplankton
28. In temperate and high latitudes, the phytoplankton may
tend to show a more even vertical distribution, but frequently
have mass production near the surface and sometimes in
deeper layers.
In estuarine areas, which are highly stratified, the
phytoplankton is frequently confined to a narrow vertical zone
below the surface, lower salinity water. The rapid attenuation
of light , especially with turbid conditions, markedly restricts
the depth of the phytoplankton in lower, more saline water, but
the comparatively rich nutrients can lead to massive algal
concentrations, and self-shading by algae may then be
significant.
Vertical distribution of phytoplankton
29. The sub-surface chlorophyll maxima are restricted to
sinking rate of the phytoplankton cells, the light intensity, the
nutrient concentrations, the physiological state of the cells
(division, age), the density and temperature of the water and
grazing pressure.
The old cells of diatoms sink more rapidly than the younger.
The dinoflagellates were found to sink more rapidly at night,
when division rate is lowest, and most slowly during the
morning, when division rate is high.
The (SCM) observed during summer is associated with the
occurrence of the thermocline, while in spring with well mixed
waters, there was no (SCM) recorded, but standing crop and
primary production were high.
Sub-surface chlorophyll maximum (SCM)
30. The (SCM) in inshore temperate waters usually differ from
those in oceanic waters because of the discontinuity of
(seasonal) thermocline, under the effect of tidal influence on
water mixing, and less stable conditions.
In sheltered temperate areas, a great deepening of the
productive algal layer with time was observed, may be due to
the gradual sinking of algal cells, and/or due to depletion of
nutrients from the surface downwards. Such a pattern could
occur only under usually stable and sheltered conditions.
In spring, the (SCM) could be attributed to the increase in
light intensity, where the more light sensitive species tending
to flourish at the subsurface rather than surface depth.
Sub-surface chlorophyll maximum (SCM)
31. A (SCM) can develop due to the light inhibition at the surface
and the increase of algal density due to self-shading. In this
case the compensation depth decreases causing a bloom at a
shallow depth, where provided nutrients are sufficient. As
nutrients are exhausted, the maximum algal crop is found in
the deeper euphotic layer. Grazing will also play a great role in
the vertical pattern of (SCM).
The factors leading to SCM are probably not identical in the
several areas, but may include changes in density of the water
it self in the column (seasonal and permanent pycnocline) and
adjustment of buoyancy by the algae. Sinking of the cells into
deeper euphotic layers may also be caused by increase in the
cell chlorophyll content, as well as by cell multiplication.
Sub-surface chlorophyll maximum (SCM)
34. Seasonal vertical profiles of phosphate, nitrate,
chlorophyll a, and zooplankton abundance
in epipelagic zone at Sharm El-Sheikh (A: autumn,
W: winter, Sp: spring, Su:summer)
35. In tropical waters, Phytoplankton biomass show:
• clear stratification in the thermally stratified areas,
being markedly greater in the euphotic zone than in the
hypophotic zone,
• more or less homogeneous distribution in mixed waters.
• Stratification is also observed in the vertical
distribution of different phytoplankton species,
diatoms: 0-50m, dinoflagellates: slightly deeper, and
coccolithophores: 50-100 m. Some species were found
abundantly at 150 m depth.
Plankton distribution
Vertical distribution in different latitudes
36.
37. In temperate and high latitudes:
• More even (homogeneous) vertical distribution of
phytoplankton occurs.
• Phytoplankton mass mostly occur near the surface
and sometimes in deeper layers are frequently
observed.
High latitude : around the 60°
Middle latitudes: between the 50° and 60°
Low latitude: below the 50° .
Plankton distribution
Vertical distribution
38. In estuarine areas (highly stratified):
• The phytoplankton are frequently
confined to a narrow vertical zone
below the surface (lower salinity water).
• In the deeper more saline water, the rapid
attenuation of light, due to turbid conditions,
markedly restricts the depth of the phytoplankton
occurrence.
Plankton distribution
39.
40. The SCM is affected by:
- Sinking rate of the phytoplankton cells,
- Light intensity,
- Nutrient concentrations,
- Physiological state of the cells (division, age),
- Density and temperature of the water,
- Water stability (affected by Temp., salinity and winds),
- Grazing pressure.
Sub-surface chlorophyll maximum (SCM)
SCM is the maximum concentration of chlorophyll
which occur in the water column in the sea at any layer
beneath the surface water.
41. Day and night vertical distributions of: a) calanoids,
b) cyclopoids, c) Poecilostomatoids, and d) harpacticoids.
Z
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a b
C d
42. Vertical profiles of the relative abundance (%) of the main
planktonic orders to the total copepods during day (a) and
night (b) off Bermuda.
Z
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(b)
(a)
43. • light availability,
• Nutrient limitation,
• N/P ratios,
• Temperature,
• Wind,
• Grazing.
• Water stability
• Upwelling
Factors affecting vertical distribution
of phytoplankton
45. Light:
Light is the ultimate limiting factor for phytoplankton
photosynthesis and vertical distribution in the water column.
The light requirement phytoplankton cells varies according to
the phototaxis of the species.
-The average radiation reaching the earth's surface from the
sun's ray is reduced by about 60% due to transmission through
the atmosphere.
-The incident light varies with day time, season, latitude,
cloudiness and other weather conditions.
-Of the radiation reaching the sea surface, more than 50% is
made up of the infra-red or heat rays (wavelengths: 730-2500
nm) and a small percentage of the ultraviolet ray (wavelength:
<380 nm).
Factors affecting vertical distribution of phytoplankton
46. -Approximately 98% of the infra-red ray is absorbed in the
upper 2 m of the sea water, while the ultraviolet ray is also
rapidly absorbed in the upper layer (maximum 10 m depth).
-The rest of the incident radiations are composed of visible
spectra (380-730 nm). The depth within which the light
intensity is suitable for photosynthetic activity by the all
existing phytoplankton species (1% of that at the surface)
known as euphotic depth. The depth of the euphotic zone
varies with the variation of water transparency.
-Each species of phytoplankton has a minimum light intensity
(compensation intensity) which is necessary to achieve
primary production.
Factors affecting vertical distribution of phytoplankton
Light:
47. Compensation intensity
Compensation depth = the depth at which the rate of
photosynthesis of phytoplankton (anabolic) is balanced by
catabolic process due to respiration.
Compensation intensity = the intensity of light at which the
rate of photosynthesis equal to the rate of respiration, it
usually occurs at very low light intensity at ther base of the
euphotic zone or below.
The occurrence of a species in the euphotic zone at the depth
of 1% of the surface light assumes that this species has a
similar compensation intensities.
However, those species which normally live near the base of
the euphotic zone, and those species which live in shallow
coastal waters, close to the bottom, must probably adapted to
much lower intensities and presumably have corresponding
lower compensation intensities.
48. -Above the compensation intensity, production increase with
increase in light energy, until reaches its maximum rate at a
certain intensity of light. Further increase of the light within a
limited range will not affect the rate of production. This range
is known as "saturation intensity". A much higher light energy
value leads to the decrease in the photosynthetic activity of
the majority of species, causing inhibitory effect.
An average value for compensation intensity has been
accepted as equivalent to 1% surface illumination. On the
other hand, the values for compensation and saturation
intensities vary for different phytoplankton species, depending
upon the state of growth (age), physiological state,
particularly their short-term or long-term light adaptation.
Factors affecting vertical distribution of phytoplankton
Light:
49. -The vertical distributions of nutrients in the ocean show a
surface minimum, a mid-depth maximum and a gradual
decrease with depth.
-This distribution is mainly controlled by biogeochemical
processes such as the production and decomposition of
biogenic organic matter and the sinking of particulate matter.
-There must be a balance between the effects of diffusion,
advection, and the net effects of biological processes.
-In the surface layers (in the euphotic zone) biological
processes will generally lead to a net utilization of the nutrient
elements, and, if the rate of utilization exceeds the rate of
supply by diffusion and by advection, the concentrations will
decrease.
Nutrient limitation
Factors affecting vertical distribution of phytoplankton
50. This change occurs during spring and summer in regions
where physical conditions limit plant activity during the
winter, when the supply to the surface layers by diffusion and
advection exceeds the utilization and leads to an increase in
the nutrient content at and near the surface.
-The supply of nutrient elements to the surface layers by
diffusion and advection may vary during the course of the
year.
- Shifts in currents will also affect the distributions of
nutrients.
-In regions of surface convergence, waters low in nutrients
may extend for a considerable distance below the euphotic
layer.
Factors affecting vertical distribution of phytoplankton
Nutrient limitation
51. -In divergence (upwelling areas) nutrient rich waters are
carried upward toward the surface.
-Divergence may occur in the open ocean or along continental
coasts where the prevailing winds are such that upwelling is
induced. In coastal areas where upwelling is seasonal or
intermittent, the nutrient content of the surface waters may
show marked fluctuations and may actually increase during
the season of maximum plant activity.
Factors affecting vertical distribution of phytoplankton
Nutrient limitation
52. Effect of wind
It has long been recognized that wind induced water motions
influence the distributions of phytoplankton cells in the ocean
and in lakes.
-Wind-generated turbulence in the upper layers of these water
bodies mixes cells, while horizontal or vertical currents advect
cells from one location or depth to another.
-Because vertical currents are usually small, turbulent mixing
in the vertical direction has commonly been considered to be
the prime determinant of the physical and chemical
environments for phytoplankton cells.
- In regions of horizontal current divergence, however, such
as near a coast or in the vicinity of oceanic fronts, horizontal
and vertical advection of phytoplankton may be important in
determining the horizontal and vertical distributions of the
cell population
53. Grazing
-Rates of grazing on phytoplankton by macrozooplankton
(cladocerans and copepods) and microzooplankton (mostly
rotifers and nauplii) were well documented in Lakes.
-Grazers consumed 3 to 26% of the total phytobiomass
present and 22 to 139% of net primary productivity daily.
-Macrozooplankton fed most heavily on algae 5 to 25 μm in
size and generally selected dinoflagellates and green algae (6
to 26% of biomass removed per day) over cryptophytes (1 to
8%/day), diatoms (0 to 10%/day) and blue green algae (0 to
6%/day).
Microzooplankton had greater weight-specific clearance rates
than macrozooplankton when consuming diatoms, blue-green
algae, and cryptophytes, but were less efficient at harvesting
green algae.
54. The potential for grazing to influence algal biomass has long
been recognized.
That grazing may account for significant mortality over longer
periods of time is apparent in recent re-evaluations of the
chlorophyll a- phosphorus relationship in lakes.
When zooplankton manipulations affect phytobiomass,
phytoplankton species composition is often altered as well.
Discrepancies in the relative proportions of phytoplankton
species found in the guts of zooplankton with the proportions
present in lake communities suggest that zooplankton
frequently feed selectively, with prey discrimination on the
basis of size, shape, toxicity, or nutrient content.
Grazing
55. Upwelling
Upwelling is an oceanographic phenomenon that involves
wind-driven motion of dense, cooler, and usually nutrient-rich
water towards the ocean surface, replacing the warmer,
usually nutrient-depleted surface water.
-The nutrient-rich upwelled water stimulates the growth and
reproduction of primary producers such as phytoplankton.
-Due to the biomass of phytoplankton and presence of cool
water in these regions, upwelling zones can be identified by
cool sea surface temperaures (SST) and high concentrations
of chlorophyll-a.
-These conditions results in high levels of primary
productivity and thus fishery production.
-About 25% of the total global marine fish catches come from
five upwellings that occupy only 5% of the total ocean area.
56. Mechanisms
The three main drivers that work together to cause upwelling
are wind, Coriolis effects, and Ekman transport.
-They operate differently for different types of upwelling, but
the general effects are the same.
-In the overall process of upwelling, winds blow across the
sea surface at a particular direction, which causes a wind-
water interaction.
-As a result of the wind, the water is transported a net of 90
degrees from the direction of the wind due to Coriolis forces
and Ekman transport.
-Ekman transport causes the surface layer of water to move at
about a 45 degree angle from the direction of the wind, and
the friction between that layer and the layer beneath it causes
the successive layers to move in the same direction.
57. This results in a spiral of water movement down the water
column. Then, it is the Coriolis forces that dictate which way
the water will move; in the Northern hemisphere, the water is
transported to the right of the direction of the wind. In the
Southern Hemisphere, the water is transported to the left of
the wind. If this net movement of water is divergent, then
upwelling of deep water occurs to replace the water that was
lost.
Mechanisms
58.
59. -Phytoplankton is important, to the fishing industry, because it
forms the beginning of the food chain for all ocean fauna and
is important in the global carbon cycle.
When Phytoplankton and higher organisms in the food chain
die and sink to the ocean floor and their carbon content is
soon sinking to the ocean bottom.
-Organic matter in sinking died organisms disappears in the
depth of the ocean and in its sediments, life in the oceans is
generally deprived of nutrients, and its abundance is limited by
nutrient concentrations.
-Nutrients are abundant near coasts and river outlets as well as
in upwelling waters, which originate near the ocean floor.
-Therefore the most productive fishing areas are generally near
river outlets, and where upwelling occurs.
Ocean upwelling and phytoplankton
60. • Warming of the surface water in spring
restricts the vertical water mixing due to the
decrease of water density under the surface.
• These conditions led to the stability of the
water column.
• The outburst of spring phytoplankton growth
depends mainly on stabilization of the water.
Water stability
Seasonal variation of stability:
Stability: the resistance of a water body to mixing
61. Seasonal variation of stability:
* The temperature rise during
late spring and early summer in
temperate regions results in the
establishment of a marked seasonal
thermocline over the summer.
* The thermocline restricts the continued supply
of essential nutrients to the euphotic zone.
* Reduced surface salinity may reduce nutrient
replenishment to the upper layers in summer.
Water stability
62. • The summer phytoplankton growth depends on the
rate of supply of nutrients by vertical mixing from the
bottom layers.
• Under tidal effects the water column will be mixed,
allowing transport of nutrients; and better light
conditions will give increased production.
• During autumn, the summer thermocline decreased,
the surface temperature decreased, and surface light is
reduced. All these conditions cause phytoplankton
blooms only with unusually sunny and calm weather.
Seasonal variation of stability:
Water stability
63. Stability and temperature:
Water stability is necessary to keep the phytoplankton cells
within the euphotic zone. It depends mainly on temperature
and to less extent on salinity.
The vernal bloom of phytoplankton is affected mainly by
water stratification, which produced due to the variation of the
vertical gradient of water temperature.
The increase of temperature in spring causes the warming of
the surface layer of water, which become less dense than the
deeper layers, and causing the stability of the water column.
The reduction in surface salinity may also affect water
stabilization due to the lower density of surface water.
Water stability
64. The stability of the water column is affected also by wind
strength, as strong winds will reduce stability. Sheltered areas
may bloom earlier than exposed regions at similar latitudes.
The continued rise in temperature during late spring and early
summer in temperate regions results in the establishment of a
marked seasonal thermocline over the summer. This
thermocline restricts the continued supply of essential
nutrients to the euphotic zone where they are being
extensively utilized during spring.
Reduced surface salinity producing a stable water column may
similarly reduce nutrient replenishment to the upper layers
later in the season and thus may cause lower productivity
when regeneration of nutrients is insufficiently rapid.
Water stability
65. The increasing illumination during spring could cause some
rise in phytoplankton, but the outburst of spring growth was
mainly dependent on stabilization of the water.
After spring the plant crop fell sharply; summer growth
depended apparently on the rate of supply of nutrients by
vertical mixing from the bottom layers.
In the areas, where tidal effects are strong the column will be
mixed, allowing transport of nutrients; production is then
mainly dependent upon average light. In other areas, where
there is moderate tidal influence provided, there is sufficient
vertical transport of nutrients, better light conditions will give
increased production.
Water stability
66. During autumn, the summer thermocline retreated its wide
spread, the surface temperature decreases, surface light is also
reduced and the mixed layer is nearly equal to the critical
depth. In autumn, therefore, phytoplankton blooms were
possible only with unusually sunny and calm weather, and
locally where the temperature gradient was still maintained.
Water stability
68. Stratification:
-Various parameters in the water column change with depth,
including water temperature, salinity, density, and pressure.
-The density (mass per unit volume) of seawater is controlled
by its temperature and salinity. The higher salinity of water is
characterized by higher density, while the higher temperature
is associated with lower density of water.
-Density stratification is the formation of layers, the deeper
layer being denser than the layer above it.
-The ocean water is divided into three density zones, the
surface zone, the pycnocline (a layer in which the density
increases significantly with depth, and the deep zone.
-Differences in density are responsible for sinking or floating
of things, particularly plankton organisms, the less dense
organisms float on top of more dense things.
69. Plankton distribution
Phytoplankton are abundant in:
* the coastal waters rich in nutrients due to
continuous mixing of the water under the
effects of waves, currents and winds.
* in the open waters around the upwelling
areas.
71. Average sea surface chlorophyll for the period Jan. 1998 –
Dec. 2006 from the SeaWIFS satellite (mg chl m-3).. Image
provided courtesy of Dr A. Yool.
72. Role of Phytoplankton in climate changes
* Phytoplankton play a key role in global climate
change by removing carbon from the
atmosphere and injecting it deep into the oceans.
* When phytoplankton die, large number of
their cells sink to the ocean floor, taking carbon
deep into the ocean.
* The diversity of phytoplankton is important for
regulating the cycles of carbon in the ocean.
73. Role of Phytoplankton in climate changes
* The stress of (UV) radiation enhances the cells
of phytoplankton to produce a chemical defense
called Dimethyl-sulfonio-propionate (DMSP).
* DMSP is broken down in the water by bacteria,
and changes into dimethyl-sulfide (DMS), the
most abundant biological sulfur compound
emitted to the atmosphere.
* DMS sticks together in the air and creates tiny
dust-like particles, condensing on the water and
begin to form clouds.
74. Biogeochemical significance of plankton
• Plankton play a role in the biogeochemical cycles of
many important chemical elements, particularly in the
ocean's carbon cycle.
• The carbon fixed by phytoplankton via photosynthesis
is transformed by grazing into zooplankton .
• This carbon enters the planktonic foodweb, where it is
either respired to provide metabolic energy, or
accumulates as biomass or detritus .
•BIO GEO CHEMICAL cycles describe the fluxes of one
or more elements (CHEM) through the different phases
inside the biotic (BIO) or abiotic (GEO) compartments
75. • When living plankton die they sink, and this leads
to the transport of carbon from surface waters to
the deep.
• This process is known as the biological pump, and
is one of the reasons that the oceans constitute the
largest carbon sink on Earth.
Biogeochemical significance of plankton
78. Global warming
• Global warming is the increase in the average
temperature of Earth’s near-surface air and oceans.
• Climate changes due to global warming are leading
to large-scale irreversible effects.
1- Natural causes,
2- Man-made (anthropogenic) causes.
Natural causes like methane gas, which is released from
arctic tundra and wetlands, and a natural cycle of
climate change on the earth (every 40,000 years).
Causes of Global warming:
79. • Man-made causes :
• - Pollution in many shapes and sizes.
- Burning fossil fuels (gives CO2).
- Mining coal and oil allows methane to
escape during digging processes.
- population. More people means more food
(methane) and more methods of
transportation and increase of CO2
emission.
Causes of global warming
80. Global warming
• Temperature changes:
• +se by 0.6oC over the past 70 to 100 years,
• +se by 1.4 - 5.8oC over the period 1990 – 2100.
• The warming would vary by region
81. Causes of global warming
• Sources of Carbon dioxide:
• Burning of fossil fuels.
• Emission from cars, airplanes and buildings
• Natural gas.
• Deforestation.
* Permafrost is a solid structure of frozen soil,
(at 650 m depth) in some arctic and subarctic
regions.
* Dryness of tundra (Tundra is a biome in arctic
and subarctic region, having distinctive
vegetation, animals and microorganisms
adapted to a unique climate).
83. • Deforestation : 20-25% of all carbon emission
by the burning and cutting of about 34 million
acres of trees each year.
CO2 emission
84. Active layer
Permafrost
Talik
Permafrost in some areas
started to emit carbon,
which could accelerate the
global warming.
Permafrost is a solid
structure of frozen soil,
(at 650 m depth) in some
arctic and subarctic regions.
-It holds about 14% of the
world’s carbon.
650 m
85. • About 50 billion tons of
carbon are held in a
frozen state in the
tundra.
• The global warming
caused dryness of
tundra and CO2 start
to be emitted to the
atmosphere.
Tundra is a biome in arctic and subarctic region,
having distinctive vegetation, animals and
microorganisms adapted to a unique climate.
Tundra
87. Causes of global warming
• Methane is the second most important gas,
being more effective (20 times) than CO2 at
trapping heat in the atmosphere.
• Methane in atmospheric have risen 145% in
the last 100 years.
• Sources of Methane:
• rice paddies,
• bovine flatulence(األبقار )روث,
• bacteria in bogs ()المستنقعات and
• fossil fuel production.
88. Causes of global warming
• Nitrous oxide:
• Sources;
• Naturally produced by oceans and rainforests.
Man-made through nylon and nitric acid
production,
• Fertilizers in agriculture,
• Cars with catalytic converters and
• Burning of organic matter.
89. Effects of global warming
• Sea Level rise,
• Change in ocean circulation,
• Decrease in sea-ice extent,
• Changes in salinity,
• Storm frequency,
• Ocean acidification
90. Global average sea level rose 0.1 - 0.2 m. during the
20th century.
It is projected to rise by 0.09 - 0.88 m. from 1990 to
2100.
Effects of global warming
91. 3. Ocean Circulation:
-Climate changes in the polar regions of the North
Atlantic, lead to changes in large scale circulation
patterns of the northern North Atlantic.
-The changes in circulation patterns influence the
distribution, abundance, composition and size structure
of zooplankton communities.
-Changes in the size and energy content of key
zooplankton prey affect energy transfer in the pelagic
food web.
-Along with the increased influx of Atlantic waters,
Arctic zooplankton communities, dominated by large
coldwater species, will be replaced with warmer water
small plankters.
Effects of global warming
93. • There has been a retreat
of sea-ice extent in the
Arctic spring and summer
by about 10 to 15% since
the 1950s.
* It is likely that there has
been about a 40% decline in
Arctic sea-ice thickness
during the late summer to
early autumn in recent
decades and a slower decline
in winter sea-ice thickness.
4. Sea-ice Extent
Effects of global warming
94. 5. Changes in salinity
-Changes in salinity may occur as a result of increased
evaporation with increased temperature and changes in
ocean circulation.
-There may also be more localized changes as a result of
changes in precipitation and associated river input and
land run-off or the melting of ice sheets.
Effects of global warming
95. * Waves in the North Sea have
increased in size, by about 20
cm every 10 years, as a result of
increases in the average wind
speed.
The first recorded
South Atlantic
hurricane, Catarina,
which hit Brazil in
March 2004
6. Storm frequency, Wind
Speed and Wave Conditions
* Over the northern North Sea
average wind speeds have
become 2 knots faster since
1960.
Effects of global warming
96. 7. Ocean acidification:
• Ocean acidification is the ongoing decrease in the
pH of the oceans, caused by their uptake of
anthropogenic CO2.
• Between 1751 and 1994 surface ocean pH is
estimated to have decreased from approximately
8.179 to 8.104
• Ocean acidification or disruptions to the
thermohaline circulation may result in disruption
of the sulfur cycle, thus reducing its cooling effect on
the planet through the creation of stratospheric
sulfur aerosols.
Effects of global warming
22 October
2017
97. • With increasing ocean acidity calcareous shells and
plates are exposed to dissolution unless the
surrounding seawater contains saturating
concentrations of carbonate ions.
• Corals, coccolithophores, algae, coralline algae,
foraminiferans, shellfish and pteropods experience
reduced calcification or enhanced dissolution with
increasing CO2.
8- Calcification
Effects of global warming
98. -Vertical stability of the water column increases as
fresher water overrides denser saltier water. This will
decreases the ability of winds and tides to vertically mix
water, and decreases the replenishment of oxygen from
the atmosphere to deeper waters of the estuary.
-Nutrient inputs from associated watersheds increase,
increasing plankton production and the organic debris to
deeper levels, causing additional oxygen consumption as
bacteria and other fauna degrade the debris.
9- Vertical stability
Effects of global warming
99. • Climatic changes promote the rapid spreading of
invasive species.
• The ctenophore Mnemiopsis leidyi was introduced from
the Atlantic American Coast into the Black Sea (1980s)
and then spread to the Mediterranean Sea.
• This species caused dramatic decrease in both the
abundance and biodiversity of the zooplankton
community in the Black Sea.
• The competition between the ctenophore species and fish
for zooplankton prey lead to a remarkable decline in the
fish stock.
10-Plankton invasions
Effects of global warming
100. • The temperature increase about +0.5oc caused the
following:
• Marked changes in plankton community structure,
• Shift in the distribution of both plankton and intertidal
organisms up to 120 miles; and future increase in shift
to 200-400 miles,
• Increase or decrease of 2-3 folds in plankton
abundance,
• Warm water species increased in abundance and extend
their range during periods of warming, while cold-
water species declined or retreated.
11-Plankton distribution
Effects of global warming
101. -The warming-up of the earth's climate will not directly
affect primary production in the oceans, but indirectly, by
changing the hydrographic circumstances.
-For example, a longer period of thermal stratification due
to higher temperature at the surface of the water may
cause lower primary production in the ocean surface.
-Also, a change in the direction of sea currents and wind
belts could affect the upwelling zones near the continents,
with consequences on, primary production.
12-Primary production
103. An indicator species is any biological species that defines
a nature or characteristic of the environment.
For example
-A species may indicate an environmental condition such
as:
-disease outbreak,
-pollution,
-species competition, or
-climate change.
-Indicator species can be among the most sensitive
species in a region, and sometimes acts as an early
warning to monitoring biologists.
Plankton indicators
104. • It must be of reasonable size and fairly easily
recognized.
• It must be not cosmopolitan species..
• Its ecology should be studied in detail.
• It must be well identified.
• The biota and physico-chemical conditions of the
locality, to which the indicator is transported, should
be fully studied before any indicator can be accepted.
• The species should not be able to perform diurnal
vertical migration.
Characteristics of indicator species:
Plankton indicators
105. Application of plankton indicators:
• Phytoplankton species as indicators to track the origin
of phytoplankton blooms.
• Plankton as indicators of Earthquakes .
• Plankton as indicators of coastal water bodies during
south-west to north-east monsoon transition.
• Chemistry Of fossil plankton shells precise indicator of
depth habitat
Plankton indicators
106. • Phytoplankton pigments as indicators of coastal
eutrophication.
• Biological indicators of climatic changes .
• Bio-indicators of water quality.
• Phytoplankton as indicator in estimating long-term
changes in the water quality.
• Bio-indicator of water movement.
• Living planktonic foraminifera as indicators of
hydrologic conditions in the Ross Sea (Antarctica)
Applications of plankton indicators:
Plankton indicators
107. Bioindicators
Plankton indicators
A bioindicator is the response of an organism that
reveals the presence of the pollutants. These organisms
(or communities) deliver information on changes in the
environment or the quantity of pollutants by changing
in their physiological, chemical or behavioural
characteristics.
108. • An increase or decrease in an animal population
may indicate damage to the ecosystem caused by
pollution.
• For example, if pollution causes the depletion of
important food sources (Prey), Predator animal
species dependent upon these food sources will also
be reduced in number.
• Some species are used in monitoring the
concentration of toxins in animal tissues, or
monitoring the rate at which deformities arise in
animal populations.
Animal indicators and toxins :
Plankton indicators
109. • Microorganisms can be used as indicators of
aquatic ecosystem health, when found in large
quantitie.
• These microorganisms will produce new proteins,
called stress proteins, when exposed to
contaminants like cadmium and benzene. These
stress proteins can be used as an early warning
system to detect the levels of pollution.
Microbial indicators and chemical pollutants :
Plankton indicators
110. • Ecological indicators used to reflect a variety of
aspects of ecosystems, including biological, chemical
and physical .
• Environmental indicators provide information on
pressures on the environment and environmental
conditions .
Ecological (Environmental) indicators
Plankton indicators
111. • blooms of plankton have been found to increase as a
response to earthquakes.
• In the area of earthquakes, heat energy releases causing
increase in nutrients and temperature of deep water,
which are raised to the surface by upwelling ,and
consequently lead to blooms of plankton.
• At earthquakes areas (India, 2001; Algeria, 2002; Iran,
2003) satellite images and measurements of sea-
temperatures illustrated a correspondence between
peaks in chlorophyll concentration and an impending
earthquake.
Plankton Indicators of Eathquakes :
Plankton indicators
112. • Chemistry of fossil plankton shells precise indicator
of depth habitat.
• The chemistry of the foraminifera shells provides
important information on the ocean's temperature,
density stratification, ice volume or may be used to
reconstruct past changes in biological productivity or
CO2.
Plankton indicators
Plankton fossil indicators
113. • During the last decade of the 20th century, 10 non-
indigenous thermophilic phytoplankton species were
first recorded in the North Sea.
• The permanent colonization of the North Sea by species
from lower latitudes may be a biological signal for
subtle changes in climate, which are indicated from the
relatively mild winters during recent years.
Plankton indicators
Biological indicators of climatic changes
114. -Certain areas of the oceans have high levels of nutrients,
but the phytoplankton does not grow as strongly as it
should. This phenomenon is known as HNLC (high
nutrient, low-chlorophyll)
-The low chlorophyll was attributed to the lack of iron,
which is an essential co-factor in the biosynthesis of
chlorophyll.
-Scientists proved that by fertilizing the surface layer of
the sea water with fine particles of iron stimulates blooms
of phytoplankton (Iron Hypothesis ).
-The Iron hypothesis was formulated by John Martin.
Iron hypothesis
115. -The scientific suggests that fertilization results in a short
term increase in phytoplankton biomass that is then
consumed by heterotrophs and the CO2 is immediately
returned to the atmosphere through the respiration.
-Tests in 2002 suggested that between 10,000 and 100,000
carbon atoms are sunk for each iron atom added to the
water.
-The amount of seeding has to be carefully controlled,
since too large phytoplankton bloom may release methane
and dimethyl sulfide (DMS), which are not desirable.
Iron hypothesis
117. • Light intensities and quality may cause either
promotion or inhibition of the excretion of the
DOM the between different species.
• Algal excretion is undertaken in darkness, but
with different rates between species.
• The water type depth play a role in the release
of the DOM.
• The percentage to total photosynthates is higher
at the deeper layer of euphotic zone.
Algal secretion
Factors affecting algal excretions:
118. • In a highly productive inshore area, the rate of
release of DOM is considerably higher than low
productive offshore.
• The cells are less active physiologically at low
nutrient level, while they are active in eutrophic
conditions.
• Release of DOM in some phytoplankton species
increased under the ecological stress (pollution
or other stresses).
Algal secretion
Factors affecting algal excretions:
119. • Increased bicarbonate concentration in the
medium resulted in a rise in the relative amount
of extracellular substances released.
• Ageing cultures showed both an absolute and
relative increase in excretion.
• The re-exposure of phytoplankton cells after
long darkness period rose the percentage of
carbon excretion.
Algal secretion
Factors affecting algal excretions:
120. • The variety of organic substances found in
seawater is largely derived from the
decomposition of marine plants and animals.
• Part of these substances may be secreted by
living phytoplankton cells, as a normal part of
their growth.
• The phytoplankton excretions are known as
dissolved organic matter (DOM).
Algal secretion
Types of algal secretions:
121. • Highly toxic substances excreted by certain
dinoflagellates at red tide and have serious
effects on wide range of animals.
• Many algal species release material which is not
obviously toxic, but can promote or discourage
the growth of other species.
• About a quarter of some eighty species of
diatoms have antibiotic effects on certain
bacteria.
Types of algal secretions:
Algal secretion
122. • Thermolabile materials (a fatty acid and a
nucleoside) were excreted by the diatom species.
• Substance of a protein nature and has antibiotic
effect.
• Carbohydrates.
• Nitrogenous compounds (amino acids and
peptides).
• Glycollic acid, polysaccharides, malic acid, citric
acid and nictonic acid.
Algal secretion
Types of algal secretions:
124. What is an alien species?
*Alien species is a species introduced into a new
environment and is not native to that environment.
•If an alien species causes or is likely to cause economic or
environmental harm or harm to human health, it is then
become an invasive species.
Sources of alien species:
- Fouling communities from ships’ hulls (33%)
- Ballast water (60%)
- Aquaculture (6%),
- Water current.
An estimated 7,000 species are carried around the world
in ballast water every day.
Alien plankton species
125. 1-Loss of native biodiversity due to:
– preying upon native species,
–serious change in the community structure.
– decreased habitat availability for native species,
– additional competition,
– parasites and disease,
– smothering and overgrowth,
– hybridization, causing genetic dilution,
– changes to ecosystem function,
– changes in nutrient cycles,
– deterioration of water quality and water colour,
– decline in water transparency with plankton blooms.
Impacts of Alien plankton species
Impacts on the ecosystem:
126. – An increase of some dinoflagellate abundance causes
increase in pH fro 8.28 to 9.02.
-The abundance of mixotrophic dinoflagellates may cause
shifts among the dominant functional groups, such as
autotrophic phytoplankton species (cyanobacteria,
diatoms).
Cause Hybridization
-The high abundance of an invasive species may
hybridize with native species so that the invaders genes
"flood" the native species, thus effectively driving the
native species to extinction.
Impacts on the ecosystem:
Impacts of Alien plankton species
127. -The red tides caused by dinoflagellates are responsible for
inflammation of the upper respiratory tract and eye
infection for swimmers.
-Decreased recreational opportunities, due to algal slicks,
overgrowth of aquifers and smothering of beaches.
-The toxins accumulate in filter-feeding organisms
(oysters, scallops or mussels) can poison people and
native marine animals.
-The algal toxins can cause Paralytic Shellfish Poisoning
(PSP) which, in extreme cases, causes muscular
paralysis, respiratory difficulties and even death.
Impacts to human health
Impacts of Alien plankton species
128. -Toxic alien species cause mass mortality of fish and
shellfish.
- They also cause invasive pathogenic species.
-cause disruption to tourism
-Damage to infrastructure (through fouling of pipes,
wharves, buoys etc.)
-The huge summer abundance of the Red Sea jellyfish
(Rhopilema omadica) entered earlier (in 1972) the eastern
Mediterranean caused yearly the following effects:
• Disruption of the coastal fisheries during the swarming
due to clogging of nets.
• deterioration in coastal tourism and fishing industries.
Socio-economic impacts
Impacts of Alien plankton species
129. -The North American comb jelly (lediy’s misspelt)
introduced into the Black Sea and Sea of Azov through
ship ballast water in 1980s was estimated of 1 billion
tones.
-This jellyfish ate vast quantities of fish eggs and larvae
as well as the zooplankton, leading to the collapse of fish
stocks in the Black Sea.
-By 1994 the anchovy fishery had almost disappeared
and the food web has completely altered within the
Black Sea.
Socio-economic impacts
Impacts of Alien plankton species
130. Red Sea jellyfish
(Rhopilema omadica)
North American comb jelly
(lediy’s misspelt)
Examples of invasive plankton species
131. -The freshwater zebra mussel (Dreissena polymorpha),
native to Europe, has become a prolific invader to
North America.
-Zebra mussels caused a substantial and sustained
decline in phytoplankton, and until recently,
zooplankton.
Impacts of alien molluscs
132. • zebra mussels in the Hudson River (New York,
USA) caused a substantial decline in plankton
production, because its veliger larvae feed on
microzooplankton .
Impacts of alien molluscs
133. Strategies used to control invasive species include :
Controlling invasive species
1-Keeping potential invaders out
By monitoring the common invasion pathways such as
ship ballast water, aquaculture and other vectors.
2-Eradicating after invasion
Early intervention can keep the population sizes of
invaders at acceptably low levels.
3-Chemical control
Using chemical pesticides to kill invaders. But chemical
control can be expensive and may only be effective for a
limited time because invaders can evolve resistance to the
pesticides.
134. • By introducing an enemy of an invasive plant (i.e., a
disease, parasite, predator, or competitor) to lower the
population size of the invader.
• A disadvantage of biological control is that some agents
attack non-target species, becoming noxious invaders
themselves, and it is very difficult to remove a
troublesome introduced natural enemy once it is
established.
Controlling Invasive Species
4-Biological control
135.
136. Eutrophication: is an increase in nutrient salts (N &P) in
an ecosystem, resulting in algal bloom, mainly microalgae.
Causes of eutrophication:
natural run-off of nutrients from the soil and the
weathering of rocks,
Inorganic fertilizers (containing nitrate and phosphate)
Erosion (following mining, construction works)
discharge of detergents (phosphates)
Sewage discharge.
Wastes of fish farms.
Eutrophication
137. Phytoplankton blooms fall into two categories:
– Nuisance algae (e.g. Noctiluca, Phaeocystis) can
create problems by discolouring the water,
creating aesthetic nuisance, and more severely by
de-oxygenating the water and killing fish and
benthic organisms.
– Toxic algae can be taken up by shellfish which if
eaten may produce diarrhoetic shellfish poisoning
(DSP), whilst Pseudonitzchia can induce amnesic
(ذاكرة )فقد shellfish poisoning (ASP).
Eutrophication
138. Main effects:
• increase in plant and animal biomass,
• increase in growth of rooted plants,
• increase in turbidity of water,
• increase in organic matter,
• development of anoxic conditions,
• decrease in species diversity,
• change in dominant biota.
• increase in HABs and/or 'red tides‘,
• kills of other biota,
• change in species composition and biomass of pelagic
and benthic communities.
Eutrophication
139. Eutrophication
Main effects:
• Coral reef damage.
• Effect on fish farming.
• Introduction of alien species,
• changes in food webs due to change in phytoplankton
community structure and in grazing zooplankton.
• Deterioration of coastal ecosystems, particularly for
tourism, recreation.
144. - Of more than 5000 species of marine phytoplankton
found in the aquatic ecosystem worldwide, about 2% are
known to be harmful or toxic.
-Harmful algal blooms (HAB) can cause adverse effects to
a wide variety of aquatic organisms, including marine
mammals, sea turtles, seabirds and finfish.
-HABs are widely distributed in many regions of the
world.
Causes of HABs
- HABs may occur natural in some locations (upwelling
areas), or as a result of human activities in other areas.
-There are many different species of algae that can form
HABs, each with different environmental requirements for
optimal growth.
Harmful algal blooms
145. Effect of HABs
These blooms of organisms cause severe disruptions in:
-fisheries as the toxins in the phytoplankton cause filter-
feeding shellfish in affected waters to become poisonous
for human consumption.
-HAB may cause water colouration.
146. Factors affecting HABs
-The type of nitrates and phosphates available in the
system are also a factor, since phytoplankton can grow at
different rates depending on the relative abundance of
these substances.
-A variety of other nutrient sources can also important
algal bloom formation, including iron, silica or carbon.
-Iron-rich dust influx from large desert areas such as the
Sahara are thought to play a role in causing HABs.
- Occurrences of large-scale climatic oscillations such as El
Nińo events enhance nutrient enrichment necessary for
HABs.
147. -Ice algae are algal communities found in annual and
multi-year sea or terrestrial ice.
-Ice algae play an important role in primary production.
-Sea ice algae are mostly concentrated in the bottom layer
of the ice, in brine channels within the ice, in melt ponds,
and on the ice surface.
-The composition of terrestrial ice algae in freshwater
systems differs greatly from that of sea ice algae.
-The terrestrial ice algae often change the color of glaciers
and ice sheets, impacting the reflectivity of the ice itself.
-Microbial life in sea ice is extremely diverse.
-Dominant species vary based on location, ice type, and
irradiance.
Ice phytoplankton
148. -Some pennate diatoms (Nitschia frigida ) dominate in the
Arctic, and (Fragilariopsis ) dominate in the Antarctic.
-Melosira arctica occurred at the ice bottom in the Arctic as
an important food source for marine species.
-Sea ice algae communities are introduced from the ocean
water to the column of sea ice through the period of ice
formation.
-Algae enter the sea ice from the ocean water during the
formation of frazil ice (1st stage of sea ice formation), when
newly formed ice crystals rise to the surface, bringing with
them micro-algae, protists, and bacteria.
Sea ice algal communities can also thrive at the surface of
the ice, in surface melt ponds, and in layers where rafting
has occurred.
Ice phytoplankton
150. -Some sea ice algae species secrete ice-binding proteins to
protect cell membranes from damage from ice crystal
growth and freeze thaw cycles.
-Surface-dwelling algae produce special pigments to
prevent damage from harsh ultraviolet radiation.
-Higher concentrations of xanthophyll pigments protects
ice algae from photo-damage by ultraviolet radiation
during ice melting to water during the spring.
-Ice algae have extreme efficiency in light utilization and
can build up biomass rapidly with light improvement
during spring.
- Higher concentrations of diatoms are found in melt
ponds with higher salinity.
Ice phytoplankton
151. -The vertical position of ice algae is limited by nutrient
availability because of their adaption to low light
conditions.
-The highest concentrations of algae are found at the base
of the ice because the porosity of that ice enables nutrient
infiltration from seawater.
-Organisms must be able to endure extreme variations in
salinity, temperature, and solar radiation.
-Algae living in brine channels secrete osmolytes, like
dimethylsulfonioprpopionate (DMSP), which help them to
tolerate the high salinities in sub-ice water after ice
formation in the winter, and low salinities produced on ice
melting in the spring and summer.
Ice phytoplankton
152. -Ice algae play a critical role in primary production and
serve as part of the polar food in the upper ocean of both
the Arctic and Antarctic.
-They contribute 3-25% to total primary production in the
Arctic and 50-57% in high Arctic.
-Their biomass are mostly consumed by amphipods (krill)
and copepods, that are eaten by fish, whales, penguins, and
dolphins.
-When ice thaw the algal communities detach to the water
and are consumed by pelagic grazers, such as zooplankton.
-Sea ice algae are rich in polyunsaturated and other
essential fatty acids, including omega 3 fatty acids that are
important for copepod egg production, egg hatching, and
zooplankton growth and function.
Role of ice algae in ecosystem
153. Temporal variation
The timing of sea ice algae blooms has a significant impact
on the entire ecosystem.
-Initiation of the bloom is primarily controlled by the
return of the sun in the spring. Because of this, the ice
algae bloom usually occurs before the blooms of pelagic
phytoplankton, which require higher light levels and
warmer water.
-Early in the season, prior to the ice melt, sea ice algae
constitute an important food source for higher trophic
levels.
154. -With climate change and warming of Arctic and Antarctic
regions, , decreasing ice cover in polar regions is expected
to decrease the role of sea ice algae in the annual primary
production.
-Thinning ice allows for greater production early in the
season but early ice melting shortens the overall growing
season of the sea ice algae.
-This melting also contributes to stratification of the water
column that inhibits the upwelling of nutrients from deep
waters. This is expected to cause an overall shift towards
pelagic phytoplankton production.
- These alterations will affect the reproduction and
migration cycles of many polar primary consumers that
are timed with the bloom of sea ice algae.
Implications of climate change
155. - In early spring sea-ice algal growth starts before that of
phytoplankton.
-In summer as the sea ice melts and nutrients become
limiting, some sea-ice algae are released to the water
column or grow into the water column. Due to their
stickiness and the under-ice turbulence they form
aggregates.
- In late summer melt ponds grow in depth and the sea-ice
algae that are still in the ice are gradually exposed to very
low salinities, high irradiances, and nutrient depletion
making them accumulate and degrade in the pond. -
Depending on the environmental conditions, some sub-ice
aggregates sink and others remain floating.
Seaonal variation of ice algae
156. -(4) In early autumn, the melt ponds can either open
completely allowing some phytoplankton species to come
into the melt pond, or they can refreeze again, becoming
second year ice.
-(5) In autumn those melt ponds that were open to the
seawater freeze again, trapping the floating aggregates
that were not grazed in the newly formed ice.
Seaonal variation of ice algae
159. Snow at the surface reduces light availability in specific
areas and thus the ability of algae to grow
160. The undersurface of the pack ice in Antarctica colored
green - Antarctica krill scraping off the ice algae
161.
162. During the winter months the plankton is trapped in the ice
and overwinters until sunlight returns to the Arctic in spring.
163. Sea ice algae inhabiting the brine channels color the ice
green (seen here from below the ice).
164.
165.
166. Automated instrument system to
obtain & transmit upper ocean water
property profiles under perennial sea
ice in the polar oceans, multiple times
daily over months to years.
Ice-Tethered Profilers
167.
168. Mycosporine-like amino acids (MAAs) are small secondary
metabolites produced by organisms that live in environments
with high sunlight, usually marine environments.
-There are up to 20 known MAAs identified, that are known
as “microbial sunscreen” but their function is not limited to
sun protection.
-MAAs are widespread in the microbial world and have been
reported in many microorganisms including heterotrophic
bacteria, cyanobacteria, microalgae, macroalgae, and fungi, as
well as some multi-cellular organisms.
-the most characteristic feature of MAAs is their light
absorbing and radiation protecting properties.
-All MAAs absorb UV light that can be destructive to
biological molecules (DNA, Proteins, etc.).
169. They are also effective antioxidant molecules and are able to
stabilize free radicals within their ring structure.
- MAAs are able to boost cellular tolerance to desiccation,
salt stress, and heat stress.
