OXB2005 Zooplankton

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OXB2005 Zooplankton

• Indicator species

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Summary indicator species
Institute of European Finance

• Spatial and temporal distribution of Zoo-plankton
• Practical use of indicators
• Causes of Zoo-plankton community changes
• Why are indicator species important?

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Why are indicator species important?

• We can use some zoo-plankton species as
  INDICATORS of different water masses and
  environmental changes.
• Water quality indicators (pollution)
• Climate changes indicators (global warming)
• Predict changes in World fisheries (food of
  fish-larva)

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Zoo-geography of the Zooplankton

• How can we have indicator species?
• Oceans/water masses are very different in their
  chemical and physical properties.
• Temperature
• Salinity
• Chemical constituents
• and also Plankton communities

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Zoo-geography of the Zooplankton

• Characteristics of water masses can change
  between
• Regions
• Ocean Basins
• Seasons
• Each water mass is associated with a different
  abundance and composition of plankton since
• plankton species are very sensitive to
  environmental conditions
• their distribution is dictated by the species
  ability to survive and /or to reproduce in a
  given water mass.

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Zoo-geography of the Zooplankton

• Regional differences in Zoo-plankton distribution
  results in
• Neritic species
• Oceanic species
• Intermediate species
• Cosmopolitan species

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Zoo-geography of the Zooplankton

• Neritic species are found in coastal waters where
  the conditions of temperature and salinity show
  large changes. Examples are
• Sagitta setosa (Chaetognath)
• Temora longicornis (copepod)
• Centropages hamatus (copepod)
• Larvae of benthic species (e.g. Barnacles)

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Zoo-geography of the Zooplankton

• Oceanic species live in more stable ecological
  conditions (temperature, salinity) and often in a
  greater range of water depths.
• Pleuromamma gracilis (copepod)
• Siphonophores (Cnidaria)
• Heteropods (mollusca)

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Zoo-geography of the Zooplankton

• Intermediate species are found between neritic
  and oceanic areas.
• Sagitta elegans (Chaetognaths)
• Euphasids (Crustacea)

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Zoo-geography of the Zooplankton

• Cosmopolitan species few species have an
  ocean-wide distribution. Examples of such
  species are
• Oithona similis (copepod)
• Beroe cucumis (ctenophore)
• Pleurobrachia pileus (ctenophore)

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Zoo-geography of the Zooplankton

• Expatriation areas (Ekman, 1953)
• Species distribution is controlled mainly by
  temperature. A large body of water can carry
  zoo-plankton to new areas hundreds of miles from
  where they reproduced.
• They may stay alive but cannot reproduce or may
  die due to slow temperature changes with time of
  original water mass.
• Lusitanian plankton carried by deep currents (600
  m depth) from Mediterranean up to the Shetlands
  islands (Scotland). Species Sagitta lyra and
  Pelagia noctiluca, salps.

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Zoo-geography of the Zooplankton

• Latitudinal differences in distribution
• Zooplankton can be divided into geographical
  areas based on temperature.
• Tropical
• Temperate
• Polar

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Zoo-geography of the Zooplankton

• Tropical seas
• Lower water density
• Higher surface temperatures
• Great species diversity
• Salps
• Heteropods
• Majority of pteropods
• Several siphonophores (Velella and Physalia)

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Zoo-geography of the Zooplankton

• Temperate oceanic waters
• Lower diversity (few species dominant)
• Calanus community
• Calanus finmarchicus (dominant)
• Metridia lucens
• Eucheta norvegica
• Pseudocalanus sp.
• Oithona similis
• Euphasids (Thysanoessa sp.)
• Intermediate waters Meganictiphanes norvegica
  (Euphasids), Sagitta elegans (Chaetognaths),
  Centropages typicus (copepod).

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Zoo-geography of the Zooplankton

• Polar Latitudes
• High water density
• Large body sizes
• Low diversity
• Euphasia superba (Euphasid, Krill)
• Calanus glacialis (copepod)
• Calanus hyperboreus (copepod)
• Metridia longa (copepod)
• Limacina helicina (pteropod)
• Martensia ovum (ctenophore)

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Zoo-geography of the Zooplankton

• Seasonal differences in Zoo-plankton living in
  Temperate latitudes
• Seasonal changes in Zoo-plankton species are due
  to different life/reproductive cycle, resistance
  to environmental factors, competition/predation
  among species.
• Thus, the plankton composition can also be used
  to identify the season.

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Zoo-geography of the Zooplankton

• Seasonal changes in zoo-plankton of the Menai
  Strait, North Wales, UK
• Winter Low diversity, mainly holoplankton
  species large adult copepods like Pseudocalanus
  elongatus (dominant, cold water species), Temora
  longicornis, Centropages hamatus, Sagitta sp.,
  some flat-fish larva and egg. Sparse meroplankton
  mostly eggs of Littorina sp. (gastropod) and
  sparse crab zoea. No or limited larval stages.

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Zoo-geography of the Zooplankton

• Spring Higher diversity, mainly meroplankton
  species including the larvae of many benthic
  species like barnacle nauplii, crab zoea, mollusc
  larvae, Terebellid larvae (tube worm).
  Holoplankton Herrings, sprat (fish larvae),
  Temora and Centropages (dominant), many
  copepodite stages, increase in Pleurobrachia
  pileus, Beroe sp. (predators on copepods).

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Practical use of indicators

• An unknown zoo-plankton samples can be analysed
  and described to a seasonal and a geographical
  area based on the species of holoplankton and the
  meroplankton it contains.
• Thus, we can identify the origin of the plankton
  and of its water mass. Water masses can be
  followed not only by their temperature, salinity
  chemical composition but also by their planktonic
  organisms which TAG them and are called
  INDICATOR SPECIES.

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Zoo-geography of the Zooplankton

• Summer high diversity, mainly copepod of small
  sizes. Holoplankton Acartia clausii (dominant,
  from resting eggs hatching in summer),
  Pseudocalanus sp. (lowest). Meroplankton
  polychates, mollusks and crab larvae (megalopa).
• Autumn Lower diversity, small copepods.
  Holoplankton majority Pseudocalanus sp.
  (dominant), numerous Sagitta setosa and
  Pleurobrachia pileus, numerous bivalve larvae.

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Practical use of indicators

• How do we use INDICATOR species ?
• A good indicator species should
• Be common enough in all samples in a given area
• Be easy to pick out under low magnification
• Be linked with the original centre of abundance
• Be restricted in his reproductive ability

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Practical use of indicators

• Changes in the abundance of some marine
  zoo-plankton species are associated with
  long-term changes in the oceanic climates
• Examples
• Russell Cycle (British Isle)
• Calanus finmarchicus NAO-index (North Atlantic
  Oscillation Index)
• Peruvian Anchovy ENSO (El-Nino Southern
  Oscillation)

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Practical use of indicators

• Russell Cycle
• The development of the study of plankton
  indicators was greatly stimulated by the work of
• Russell (1939) English Channel, Western
  Approaches
• Meek (1921-27) North Sea, Northumberland coast
• Documented a complex series of changes in the
  plankton community around the British Isle .

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Practical use of indicators

• Study of Chaeognaths species Saggita elegans and
  S. setosa and their associated plankton community
  as indicators of the water masses movements
  around British Isle.
• Chaetognaths are easy to identify, are big and
  are restricted to certain water masses.

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Practical use of indicators

• Sagitta elegans
• Intermediate species (e.g. between oceanic and
  neritic waters).
• Max body length 30 mm
• Long ovary in adult
• Conical seminal vescicles, far from lateral fins
• Stiff body when preserved
• Distribution Northern North Sea, Western English
  Channel, Western Irish Sea.

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Practical use of indicators

• Richer waters high plankton diversity, high
  plankton concentration, high salinity
  nutrients.
• S. elegans water Calanus finmarchicus,
  Centropages typicus, Euphasids (meganictiphane),
  Aglantha digitale (trachimedusa), Cosmetira
  pilosella (hydroid), Candacia sp., Tomopteris
  (polychaete), Euthemisto (hyperid), sparse
  larvae, herring and/or mackerel.

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Practical use of indicators

• Sagitta setosa Neritic species
• Max body length 14 mm
• Short ovary in adult
• Wedge shaped seminal vescicles, near lateral fins
• Flexible body when preserved
• Poorer waters Low plankton diversity, low
  plankton concentration, low salinity, low
  nutrients.
• S. setosa water Temora longicornis, Centropages
  hamatus, Isias claviceps, Oithona nana, mysids,
  numerous larvae, pilchard.
• Distribution Southern North Sea, Eastern English
  Channel, Eastern Irish Sea.

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Practical use of indicators

• The Russell Cycle Northumberland coast
• Meek observed that the relative abundance of the
  two Sagitta species fluctuates around the
  Northumberland coast
• He concluded that hydrographic conditions
  affected the extent of distribution
• Strong flow of Atlantic water in North Sea ? S.
  elegans spreads South.
• Weak flow of Atlantic water in North Sea ? S.
  setosa spreads North

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Practical use of indicators

• The Russell Cycle -English Channel
• Russell investigated the long term distribution
  of S. elegans and S. setosa in the English
  channel between 1930-60.
• Observed fluctuation in Chaetognaths species
  abundance and water mass characteristics over
  time at Plymouth station.

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Practical use of indicators

• Prior 1930s
• S. elegans dominant West of Plymouth and S.
  setosa dominant to the East
• 1950s - 60s
• S. elegans retreat west of Plymouth
• Increase in Temperature ( 0.5 ?C mean)
• Decrease in nutrients Phosphate
• Decrease in herring , increase in pilchard

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Practical use of indicators

• 1970s-90s Shift
• Reverse of trend prior to 1930s
• S. elegans advance East of Plymouth
• Decrease in Temperature
• Increase Phosphate
• Increase in Sardina pilchardus which replaced
  Clupea harengus

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Practical use of indicators

• These shifts in water masses caused the collapse
  of the herring fisheries and replacement with the
  pilchard in the 50-60s. Reverse of cycle in the
  70s with the collapse of pilchard and the
  reappearance of the herrings with the mackerel.
• Duration of the Cycle from the 1930s to 70s was
  40 years

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Russell Cycle
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Causes of plankton changes

• Why should one plankton community replace another
  with a 40 years cycle?
• Nutrient changes (phosphate)
• Over-fishing
• Natural cycles
• Direct Climate effect
• Indirect Climate effect

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Causes of plankton changes

• Nutrient changes
• Due to variation in the flow of water in the
  channel, from elegans (mixed water) to setosa
  waters (coastal).
• Lower levels of Phosphate in the 1950-60's, but
  increase of S. elegans preceded nutrients
  increase.

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Causes of plankton changes

• Over-fishing
• community controlled by the top predator. If
  herring was over-fished the Pilchard would
  replace it. However, all the species including
  herrings, mackerel and pilchard were
  heavily-fished.
• Natural fluctuations
• Assume a change in the food of the plankton.
  However, primary production in the English
  Channel hasn't changed much over last century.
  Thus, zoo-plankton and fish change no due to
  phytoplankton production. No change in community
  but a shift in communities.

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Causes of plankton changes

• Direct climate changes
• Sun spot activity poorly correlated with plankton
• Indirect climate changes
• Change of the rate of water mass flows into
  channel have pushed setosa/elegans boundary
  backwards and forwards

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Causes of plankton changes

• North Atlantic drift (NAD)
• Warm periods extension of NAD spreads north into
  Arctic, Gulf Stream wider spread, weak flow in
  English Channel and S. setosa goes West
• Cold periods NAD spread south Gulf Stream
  tighten, strong flow in English Channel and the
  S. setosa retreats East.
• But, no evidences of salinity changes with
  different water masses.

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Causes of plankton changes

• There is general, agreement that the Russell
  cycle is associated with Climate changes.
• Ref Southward (1980), Nature, 285361-470
• Russell Cycle has been recently linked with the
  NAO-index (Mann Lazier, 1991)

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Definition ENSO and NAO-Index

• There are other evidences of indirect climate
  changes on plankton are
• NAO-Index- The North Atlantic oscillation index
  is the dominant mode of inter-annual climate
  variability over the North Atlantic ocean
  (Northern Emi-sphere).
• ENSO El-Niño is a warm nutrient poor surface
  current that replaces the cold coastal up-welling
  off coast of Peru (Southern Emi-sphere).

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NAO-index and C. finmarchicus

• Long term fluctuation in NAO-index strength ve
  correlation in C. finmarchicus abundance
  (PCA-Plankton Continuous Recorder)
• C. finmarchicus is an important in the diets of
  the fish larvae of many commercial fish stocks.
• Changes in Atlantic Salmon population
• Ref Fromentin Planque (1996), Marine ecology
  Progress Series, 134111-18.

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NAO-Index C. finmarchicus
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El-Nino and the Peruvian Anchovy

• Peruvian Fishery Developed in the 1950s to be a
  model of fisheries management. Anchovies eating
  plankton. Anchovy harvest 9-10 million Tons.
  Collapsed from 1970 onwards and has not recovered
  since.
• During El-Niño warm oligotrophic water pushed
  anchovies to feed deeper and birds starved.
• Ref. Mann, K.H. Lazier, J.R.N. (1991),
  Dynamics of marine ecosystem

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Peruvian Anchovy El-Niño
Strong
Moderate
Strong
Moderate
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Suggested references

• 1) The Open Ocean, vol. 1, by Alister Hardy,
  (Wolfson Library)
• 2) Biological Oceanography an Introduction
  (1997), C.M. Lalli T.R. Parson (Wolfson
  Library, QH91.L35.1997)
• 3) Mann, K.H. Lazier, J.R.N. (1991), Dynamics
  of marine ecosystem, (Wolfson Library)
• 4) Southward (1980), The western English Channel
  - an inconstant ecosystem? Nature, 285361-470
  (Science Library)
• 5) Plankton and productivity in the Ocean, Vol.
  2, J.E., Raymont (1980), Pergamon Press, (Wolfson
  Library, QH91.8.P5R3)