Transcript Plankton - Somers Public School District

Plankton
Plankton Definition
Plankton Any drifting organisms which can be animals, plants,
archaea, or bacteria, that live in the pelagic zone of
oceans, seas, or fresh water.
Plankton are defined by their role in the environment.
They provide a crucial source of food to more
familiar aquatic organisms such as fish.
Plankton Definitions
While some forms of plankton are capable of
independent movement (diel vertical
migration) their horizontal position in the
water is determined by currents in the body
of water they inhabit.
Plankton are unable to resist ocean currents.
Types of Planktons
Holoplankton organisms that spend their whole
lives as plankton (e.g. most algae, copepods, salps,
and some jellyfish).
Meroplankton are those organisms that are only
planktonic for part of their lives (usually the larval
stage), and then graduate to either the nekton or a
benthic (sea floor) existence. Examples of
meroplankton include the larvae of sea urchins,
starfish, crustaceans, marine worms, and most fish.
Sea star
(Meroplankton)
Holoplankton
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Functional Groups of
Planktons
Phytoplankton- plant plankton, autotrophic,
prokaryotic or eukaryotic algae that live near the
water surface where there is enough light to support
photosynthesis.
Among the more important groups are the diatoms,
cyanobacteria, dinoflagellates and coccolithophores.
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Functional Groups of
Planktons
Zooplankton- animal plankton, small protozoans or
metazoans (e.g. crustaceans and other animals) that
feed on other plankton and telonemia.
Some of the eggs and larvae of larger animals, such
as fish, crustaceans, and annelids, are included
here.
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Functional Groups of
Planktons
Bacterioplankton, bacteria and archaea,
which play an important role in recycling
organic material into the water (note that the
prokaryotic phytoplankton are also
bacterioplankton).
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Common Types of Plankton
Diatoms are the most common phytoplankton.
They are one celled producers with a covering (called
a frustule) of glass.
Many species have flotation mechanisms (spines,
internal oil droplets, colonies).
Diatoms are important oxygen producers in marine
ecosystems (usually the first step in the food chain).
They are holoplanktonic.
When conditions are bad they die, sink, the cell
decomposes and the frustule breaks up and mixes
with sand and mud. This combination of sediments
and glass frustules makes a siliceous ooze called
diatomaceous earth
Asexual reproduction occurs with diatoms in good
conditions in a unique way so that some get smaller
and smaller until they are too small to function
properly.
Common Types of Plankton
Cont..
Certain species of diatoms produce harmful chemicals (most
notably domoic acid) which can concentrate in animals who eat
plankton (filter feeders). Large amounts of domoic acid
consumed by mammals (such as seals, sea lions and humans)
can cause erratic behavior and lead to death.
Plankton Size
Group
Size range (ESD)
> 2×10-2
(20+ mm)
Megaplankton
m
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Macroplankton
2×10-3→2×10-2 m
(2-20 mm)
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Mesoplankton
2×10-4→2×10-3
m (0.2 mm-2 mm)
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Examples
metazoans; e.g.
jellyfish; ctenophores;
salps and pyrosomes
(pelagic Tunicata);
Cephalopoda
metazoans; e.g.
Pteropods;
Chaetognaths;
Euphausiacea (krill);
Medusae;
ctenophores;
salps, doliolids
and pyrosomes
(pelagic Tunicata);
Cephalopoda
Medusae; Cladocera;
Ostracoda;
Chaetognaths;
Pteropods; Tunicata;
Heteropoda
Plankton Size Cont..
Group
Microplankton
Size range (ESD)
Examples
2×10-5→2×10-4 m
(20-200 µm)
Large eukaryotic
protists; most
phytoplankton;
Protozoa
(Foraminifera); ciliates;
Rotifera; juvenile
metazoans - Crustacea
(copepod nauplii)
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Nanoplankton
2×10-6→2×10-5
m
(2-20 µm)
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Picoplankton
2×10-7→2×10-6 m
(0.2-2 µm)
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Small eukaryotic
protists; Small
Diatoms; Small
Flagellates;
Pyrrophyta;
Chrysophyta;
Chlorophyta;
Xanthophyta
Small eukaryotic
protists; bacteria;
Chrysophyta
Plankton Size Cont..
Group
Femtoplankton
Size range (ESD)
< 2×10-7 m (< 0.2
µm)
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Examples
marine viruses
Distribution
Plankton are found in oceans, seas and lakes.
The first cause of amount and variability plankton
varies horizontally, vertically and seasonally. This is
caused by the availability of light in an area.
A secondary cause of variability is the availability of
nutrients. Large areas of tropical and sub-tropical
oceans have a lot of light they have a low availability
of nutrients such as nitrate, phosphate and silicate.
This is a result of ocean-circulation and ocean
layering or stratification of water column.
Importance of Plankton
Phytoplankton fix carbon in sunlight by
photosynthesis. Primary production (the
amount of carbon produced by
photosynthesis) occurs as a result of
phytoplankton.
Phytoplankton are at the bottom of the
aquatic food web and produce all the energy
for all other life in the water.
Phytoplankton produce approximately 60% of
the oxygen for the planet Earth.
Importance of Plankton Cont..
Zooplankton are initially the sole prey item for
almost all fish larvae as they use up their yolk
sacs and switch to external feeding for
nutrition.
Fish species rely on the density and
distribution of zooplankton to coincide with
first-feeding larvae for good survival of
larvae, which can otherwise starve.
Natural factors (e.g. variations in oceanic
currents) and man-made factors (e.g. dams
on rivers) can strongly affect zooplankton
density and distribution, which can in turn
strongly affect the larval survival, and
therefore breeding success and stock
strength, of fish species.
Common Phytoplankton
Diatoms
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Dinoflagellates
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Bioluminescence
Some species of dinoflagellates will produce
a blue/green light, after dark, when they are
disturbed.
This probably functions to scare predators
away in the natural environment. There are
always a few of these dinoflagellates in the
water but their small size keeps their tiny
spark of light from being visible on most
nights. But, if these species are blooming,
and very concentrated in the seawater, every
movement of the water produces a glow waves appear to light up as they break at
night and fish leave glowing trails in the
water as they swim at night.
This phenomenon is seen all over the world.
Zooplankton
Zooplankton are tiny animals found in all ocean
zones, particularly the pelagic and littoral zones in
the ocean, but also in ponds, lakes, and rivers.
They are a key component of marine ecosystems.
The most common plankton are protists,
nanoplanktonic flagellates, cnidarians, ctenophores,
rotifers, chaetognatha, veliger larvae, copepods,
cladocera, euphausids, krill and tunicates.
Nanoplanktonic Flagellates
Nanoplanktonic flagellates that help keep bacteria
populations under control.
They are characterized by either a long tail used for
swimming (flagellates) or by hair-like structures
called cilia (ciliates).
Some dinoflagellates have a net-like structure called
a protoplasmic net—used to capture and eat prey
that are typically larger in size than bacteria.
Some dinoflagellate species are also responsible for
harmful fish kills and the infamous red tides.
Ciliates are capable of catching bacteria, other
protists and phytoplankton.
Cnidarians
These contain the colonial siphonophores and the
scyphozoans—also known as the true jellyfish.
Both of these animals are predators and have
stinging tentacles.
They are not found often in fresh water and in the
ocean they inhabit the layers closer to the surface.
Comb jellies or ctenophores were previously
classified under Cnidaria but have recently been
distinguished from other jellyfish because they lack
the characteristic stinging cells of other jellyfish
known as nematocysts. Comb jellies effectively keep
copepod zooplankton levels in check through
Cnidarians
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Phylum Rotifera
Most of the rotifers are non-motile (not able
to move) but about 100 species are
holoplanktonic.
Rotifers eat bacteria, detritus, other rotifers,
algae or protozoa.
Rotifers are highly efficient reproducers.
They are able to reproduce asexually
(without a mate) when environmental
conditions are good, and sexually when
environmental conditions are stressful.
Rotifer
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Marine Gastropods
Larvae of benthic mollusks usually found in coastal
waters, such as marine gastropods including
heteropods or pteropods.
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Krill
They are found all over the world.
They can be 3 cm large and are an important source
of food for many types of whales. In cold waters, krill
often feed on diatoms, a type of phytoplankton.
In warmer water they prefer to eat other animals
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Tunicates (Sea Squirts)
Some tunicates are planktonic, such as the
holoplanktonic classes Appendicularia and Thaliasia.
Both are filter feeders; Appendicularia consumes
small food particles using a mucous filter.
Other types of tunicates are benthic and are only
planktonic during their larval stages.
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Copepods
Most macrozooplankton are copepods found in
marine and freshwater ecosystems.
Copepods swim using an antenna and frontal
structures on their bodies. They eat phytoplankton
and detritus, and occasionally other zooplankton
smaller in size.
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Adaptations
They have structural adaptations to be able to float in the water
column. Adaptations include: flat bodies, lateral spines, oil
droplets, floats filled with gases, sheaths made of gel-like
substances, and ion replacement. The flat body and spines
allow some species of plankton to resist sinking by increasing
the surface area of their bodies while minimizing the volume. All
other adaptations keep plankton from sinking quickly to the
bottom.
Zooplankton have also adapted mechanisms to deter fish (their
heaviest predator) including: transparent bodies, bright colors,
bad tastes, red coloring in deeper water, and cyclomorphosis.
Cyclomorphosis occurs when predators release chemicals in
the water that signal zooplankton, such as rotifers or
cladocerans, to increase their spines and protective shields.
Night Swimming
Many types of zooplankton migrate deeper into the water during
the day and come up at night.
The migration of species appears to be dependent on location
rather than particular species types.
All plankton migrate differently based on factors like age, sex
and the season. The amount of light is probably the major factor
in the extent of migratory behavior.
It seems that zooplankton move around most in low light and
least in higher light situations.
It’s possible that zooplankton migrate to lower levels during the
day so they are less visible to predators relying on vision. At
night, zooplankton can sneak up to the surface and snack on
phytoplankton relatively safely.
The lower metabolism occurring in colder waters during the day
may also be a factor in the migration of zooplankton. This way,
zooplankton can save energy by feeding in the cooler, night
waters.
The fact that different species of zooplankton have varying
migration times may be the result of a partitioning of resources.