LSM3254_Lecture 7 Plankton and Productivity

8/3/2019 LSM3254_Lecture 7 Plankton and Productivity

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LSM3254 Ecology of Aquatic Environments

an ton an pro uct v ty

Peter ToddDept of Biological Sciences

By the end of this lecture you should be able to discuss various

Learning outcomes:

aspects of plankton and productivity, including:

What is phytoplankton? What are Dinophyta,Chrysophyta and Cyanophyta?

The diversity of zooplankton. Definition of holoplanktonand meroplankton, etc.

Primary production in relation to depth, temperatureand nutrients.

Seasonal phases of primary production.

Plankton - Greek: “wanderer" or "drifter”

Limited powers of locomotion and thus at the mercy ofwater movements, e.g. currents.

Some planktonts (phyto- or zoo-) are active swimmers,but are so small that swimming does not move them far(compared to the distance they are carried by the water).However, it does help them to:

• Keep them afloat / alter their level in the water column

•

• Avoid capture

• Find a mate

2 main types: zooplankton and phytoplankton (but also bacterioplankton).

McGraw-Hill

Phytoplankton is at the bottom of the marine food chain



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Phytoplankton

• Phytoplankton contain chlorophyll

• -

• Generally microscopic; but there are some v.large planktonic alga, e.g the seaweedSargassum in Sargasso Sea.

• Larger phytoplankton:•

Length 300-400micrometer,width 45

• Smaller phytoplankton:• Coccolithophores (5-20 µm) and Cyanobacteria (blue

green bacteria, ~1 µm)

micrometer.

Very large phytoplankton - Sargassum

Huge mats of

atona eograp c

Sargassum float inthe Sargasso Sea

– supporting anentire ecosystem!



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Microscopicphytoplankton

Three main phyla:

Dinophyta (or Dinoflagellata)Protoctista

rysop y a inc Diatoms and Coccolithophores )

Bacteria Cyanophyta (or Cynobacteria)

u aryo es

Prokaryotes

Dinoflagellates (Dinophyta)• Unicellular - solitary organisms

• Usually two flagellaMcGraw-Hill

• -groove called the annulus,other groove= sulcus

• Plates of carbohydratecellulose

• Some produce toxins

• 2-8x106 cells per liter!

• Reproduction – asexualdivision

• Can be heterotrophic

• Zooxanthellae

Thecate dinoflagellate

A dinoflagellate swimming in acharacteristic spiralling motion

Dinoflagellates

Important as primary producers of food material, althoughNoctiluca devours copepod larvae and other small organisms.



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Red tidesP. Piscicida =

VIMS

McGraw-Hill

Pfiesteria piscicida

Usually harmless, but some speciesproduce neurotoxins that can be

transferred through the food web.

Ceratium

Common in temperate waters – can bloom but harmless.

Zooxathellae are dinoflagellate symbionts of hermatypic corals


Three main phyla:




u aryo es

Prokaryotes



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Diatoms(Chrysophyta)

• Diatoms are unicellular algaegenerally placed in the classBacillariophyceae

• -

• Some enclosed within ‘pillbox’

• Box made of sil ica

• Singly or in chains

McGraw-Hill

• Reproduction –

two) - Auxospore after afew generations

Pillbox diatom

McGraw-Hill

McGraw-Hill

Pillbox diatom reproduction

Diatoms



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Three main phyla:




u aryo es

Prokaryotes

Coccolithophores (Chrysophyta),

with their tiny calcareous plates(coccoliths), are abundant in alloceanic waters.

McGraw-Hill

White Cliffs of Dover, U.K., Formed ~140 to 70 million years ago.

FreeFoto.com


Three main phyla:




u aryo es

Prokaryotes

Cyanobacteria has

been around for along time (~3.5billion years!)

McGraw-Hill

There are some

living stromatolites,e.g. Western Australiaat Shark Bay.



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Perhaps most important are the recently discovered, very tiny(0.8 to 0.6μm) Prochlorophytes (Cyanophyta), which areprobably the most abundant phytoplankton in the open sea.

Zooplankton

Free floating (more or less)

animals in the water body

Zooplankton

• Most phyla are represented

NOAA

• Crustacea/copepods-

account for 60-70%. Large

antennae.• Primarily herbivores

• Usually microscopic but

includes jellyfish too

• Often transparent

Marine food chain

Zooplankton are the next link up of the marine food chain.



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Holoplankton - spend theirentire life in the plankton.

Meroplankton - spend onlyparts of their lives in thep an on, e.g. arva s ages

Zooplankton - holoplankton

(entire life as plankton- often oceanic) • Foraminiferans and

Radiolarians (Protoctists)Jelly fish (Scyphozoa) are

• Cnidaria (Hydrozoa and

Scyphozoa)

• Annelids

• Arthropods

• Molluscs - pteropods and

probably the most familiar

NOAA

e eropo s

• Chaetognaths

• Urochordates

• Ctenophores

Radiolarians andforaminiferans

McGraw-Hill

Portuguese-man-of-war, physalia

Floating colonial hydrozoan: Adam Laverty

polyps:

A pneumatophore (float)

Dactylozooids (tentacles)

Gastrozooids (feedingzoo s

Gonozooids (producegametes)



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Zooplankton: meroplankton (some of the time

as plankton – often neritic [as opposed to oceanic])

– stages) - all phyla

Sea star larvae

Certain times of the year neritic meroplankton

(i.e. nearshore & temporary) plankton aredominated by larval crustaceans.



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Primary productivity

Primary production

• The synthesis of organic compounds frominorganic constituents of seawater by theactivity of organisms is termed ‘production’.

• The raw materials are:

1) water

2) carbon dioxide

nu r en s

• Mostly by pelagic photosynthesis (a few %chemosysnthesis)



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• Gross primary production (GPP): total amount

Primary production

of organic material fixed in the primaryproduction process

• Net primary production (NPP): amount ofenergy available for transfer to other organisms

• Primary production of new organic material isthe first link in all food chains in the sea

Primary production

Large marine algae inshallow waters onlycontribute ~0.05%ecause t ey are o

restricted distribution

Herbivorous zooplanktoneat phytoplankton, leadingto the formation of animaltissue = secondary

production

These organisms are then eaten by the first rank of carnivorousanimals (carnivorous zooplankton and fish predators) and this iscalled tertiary production. These may then fall prey to othercarnivores and so on…

In general, the highesttrophic level is occupied byadult animals with no

predators of their own

McGraw-Hill

For example, killer whales wouldoccupy the highest trophic level inan Antarctic food chain

Between each trophic level there are losses oforganic material caused because:

• 1) A percentage of organisms at each level arenot eaten but simply die and decompose.

• 2) Some of the food that animals consume isexcreted unassimilated.

However

• 3) Most of their assimilated food is broken downby respiration, leaving only a small proportion toform new tissue



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res iration

GPP

70 to90%

NPP

30%

Bacteria

Necessary fordecomposition of organicmatter.

Also, they grow andmultiply and constitute animportant component of

.

At depths (e.g. Hydrothermal vents) remote from theeuphotic zone chemosynthetic autotrophic bacteria may playa significant role in primary production.

• Primary production rates are normally expressed as theweight of carbon fixed in organic compounds beneath unitarea of sea surface in unit time (gC/m2 /day)

• Estimates of net primary production by phytoplankton: 0.05-0.5 gC/m2 /day

• Primary productivity varies

between 0.1 gC/m2/day inthe open ocean to about10g gC/m2/day in highly

McGraw-Hill

• Estimates of 33 gc/m2/dayare reported forCalifornian kelps

Factors affecting primary productivity: Light

• Phytoplankton restricted to epipelagic zone forphotosynthesis

• Light penetration affected by:

– Absorption of light by water (thus depth)

– Wavelength of light

–

– Suspended particles (turbidity)

– Latitude

– Season



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• With increase in light intensity from zero there is first a

linear phase of increasing photosynthesis.• Then a plateau is attained, where the photosynthetic

mechanism is saturated

• And finally photosynthesis decreases at high intensities(e.g. near the surface photosynthesis may be inhibited). Just nice!

Factors affecting primary productivity:

Temperature

• The rate of photosynthesis increases with rising temperatureu to a maximum butthen diminishes shar l with further

• In temperate waters there is

an outbreak of phytoplanktongrowth in the spring (could bedue to either temperature orlight conditions).

,rises of temperature.

• Temperature also influencesproduction indirectly throughits effects on movement andmixing of the water.

Factors affecting primary productivity:

Nutrients

• e s r u on o e roug ou e oceans epen supon the availability of nutrients.

• Continents are the major source of inorganic nutrients(river and dust inputs).

•oceanic waters.

• The high productivity is also a result of strong mixingforces (wind and tidal forces).



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Global primary productivity

UPWELLING: Currents bringing nutrients from

deeper water where they haven’t been utilized

Successions & associations

• Annual patterns ofphytoplanktonabundance

• Temperate regions -seasonal changesrelated totemperatureillumination etc.



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Successionsand

associations

Variesdependingon location

In summary:

Phytoplankton photosynthesize and are the primary producers of theoceans.

, ,Dinoflagellates, Coccolithophores and Cyanobacteria.

Zooplankton generally feed on Phytoplankton. Most phyla arerepresented but crustaceans dominate.

Holoplankton spend their entire life in the plankton whereasmeroplankton spend only parts of their lives in the plankton.

transfer to other organisms (GPP minus respiration).

Production isependent on light, nutrients and temperature and variesboth temporally and spatially.

Highest levels near the coast. Upwellings important too.

Depth• Epiplankton plankton of euphotic zone

• Mesoplankton between 80 to 200m

• Bath lankton below 200m

Additional reference slide

• Hypoplankton plankton close to sea bottom

• Megaplankton - above 20 cm

• Macroplankton - 2 to 20 cm

• Meso lankton – 0.2 to 20 mm

Size

• Microplankton – 20 to 200 µm

• Nanoplankton – 2 to 20 µm

• Ultraplankton - less than 5 µm

• Femtoplankton - 10-7 i.e. 0.02-0.2µm

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LSM3254_Lecture 7 Plankton and Productivity