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Plankton are at the start of the marine food web.
Phytoplankton use the suns energy to produce their own food, they are then eaten by zooplankton.
Zooplankton are food for a range of marine organisms such as fish, basking sharks, jellyfish etc. WIthout plankton there would be almost no fish, basking sharks, sea birds or dolphins living in the sea.
Babies of other marine animals
In the spring marine animals such as starfish, barnacles and crabs release their eggs into the sea.
After a couple of weeks the eggs hatch into larvae (lar-vee) and some look very different to their parents.
The babies or larvae (lar-vee) of some marine animals live in amongst the zooplankton for a few weeks or months whilst they grow into their adult form. We call this kind of zooplankton Meroplankton.
Can you guess what theses creatures will grown into?
The White Cliffs of Dover are made up millions and millions of plankton
The word plankton comes from the Greek word 'planktos' which means 'to wander'
Some plankton release a chemical that can help make clouds
Approximately half the world's oxygen comes from phytoplankton
Phytoplankton use the greenhouse gas Carbon dioxide (CO2)
The weight of all the plankton in the oceans is greater than all the whales, dolphins and fish
Phytoplankton are the primary producers of the sea, converting sunlight and CO2 into energy/ food (photosynthesis) just like plants on the land
Zooplankton are the primary consumers of the sea, and feed on the phytoplankton. They are important food source for many marine animals
Marine Food web
Phytoplankton as the primary producers form the base of the food web. The zooplankton are a mixture of omnivore and carinvore organisms which feed on phytoplankton and other zooplankton.
Zooplankton are eaten by a huge variety of animals from fish, basking sharks, rays, corals, shellfish and jellyfish. They are extremely important to the biodiversity of the marine habitat - feeding almost all life either directly or indirectly. The marine food web has predators such as sea birds, seals, dolphins and sharks. Humans are part of this food web eating fish and other marine organisms.
Some zooplankton are the larval stages of other marine organisms. This type of zooplankton is called Meroplankton.
For instance the barnacle naupli (or larvae) spends around 3 weeks in the plankton whilst it develops into its adult form. It then settles out of the water onto a surface where it spends the rest of its life inside a hard calcerous shell. Barnacles have developed a larval swimming stage as a dispersal strategy, therefore reducing the competition for space and food within the existing population.
Fish, starfish, sea urchins, corals, sea mats, tunicates, jellyfish, molluscs and numerous other marine organisms have larval stages and they often look very different to their adult forms more examples.
What have we learnt from plankton?
There are thousands of different types of plankton in the oceans and they inhabit various areas of the oceans at different times of the year. Their distribution and abudnance depends on the correct environmental conditions for the species.
Plankton are very senstive to changes in temperature, pH, salinity and nutrient availability which makes them excellant biological indicators of environmental change. SAHFOS scientists use plankton data recorded by the CPR survey to monitor changes that are occurring in the marine environment. Here are some examples of recent findings:
More information about SAHFOS research can be found here
Plankton biology and ecology
Plankton is the term given to describe the small free living plants (phytoplankton) and animals (zooplankton) living in the marine environment. The word plankton comes from the Greek word planktos which means to wander as plankton are often seen to be drifting on ocean currents.
Phytoplankton (plants) photosynthesise and live in the top 30 metres of the sea in an area called the photic zone (where light penetrates the sea). Phytoplankton are the primary producers of the oceans and they produce ~50% of the total photosynthesis of plants on Earth, sucking the greenhouse gas carbon dioxide (CO2) from the atmosphere ( Reid, P.C. and Edwards, M., 2001a. Long-term changes in the pelagos, benthos and fisheries of the North Sea. Senckenbergiana Maritima, 31: 107-115. ).
Zooplankton include protozoans, small crustaceans and at certain times of the year, the larvae of other marine organisms (meroplankton). Zooplankton graze on the phytoplankton making them the primary consumers of the sea. They are then food for fish, corals, jellyfish and basking sharks etc.
The Marine Food Web
Classic planktonic food webs often begin with the phytoplankon as the primary producers. However, it has been discovered that various nanoplankton (such as coccolithophores) and picoplankton (such as cynobacteria) actually make available the dissolved organic matter (DOM) for the majority of phytoplankton enabling them to photosynthesise. This is the microbial food web and it is an essential element of the pelagic food web. These small classes of phytoplankton are extremely abundant and show less seasonal variation than the larger phytoplankton groups. Their contribution to the food web was often overlooked by early scientists as they were too tiny to catch in nets and were easily destroyed by the sampling method.
Scientists now believe that upto 75% of the phytoplankton biomass in open water may in fact be nanoplankton and that almost 80% of photosynthesis is carried out by organisms that are <30μm in size (Malone TC (1980) Size fractionated primary productivity of marine phytoplankton. In: Falkowski PG (ed) Primary productivity in the sea. Plenum Press, New York, p 301-319 ).
Meroplankton and phenology
Meroplankton is the name given to the zooplanktonic organisms that are the larvae and juveniles of other marine organisms.
Lifecycle of a barnacle
Fish, barnacles, starfish, corals, sea mats, jellyfish, molluscs, decapods (crabs) and polychaetes are just a few of those that have a meroplanktonic stage in their lifecycle.
Meroplankton represent the mobile free living stage of many organisms. This strategy enables these offspring to colonise new areas of the marine environment and reduce competition for resources within the parental community.
During the early spring and into the summer the abundance of meroplankton increases and causes the overall planktonic biomass in coastal areas to 'bloom'. This explosion of zooplankton attracts seasonal predators and grazers such as basking sharks to the UK coasts. Many sea mammels and sea birds also time their own reproductive cycle around this abundance of food - ensuring that there is plenty to feed their own juveniles and young.
Plankton research at SAHFOS
Plankton are very senstive to changes in temperature, pH, salinity and nutrient availability which makes them excellant biological indicators of environmental change. SAHFOS scientists use plankton data recorded by the CPR survey to monitor changes that are occurring in the marine environment. Here are some summaries of our recent findings:
The Continuous Plankton Recorder Survey - a brief history
In 1925 a young fishery biologist called Alister Hardy designed and built a robust sampling mechanism capable of sampling plankton over an entire ship's journey. This device was called a Continuous Plankton Recorder or CPR.
After trialling the Mark I CPR on his Discovery cruises in the Antarctic he went on to design a smaller version of the CPR (Mark II) for use on merchant ships. This model is essentially the same as that used routinely today. In September 1931, the SS Albatross towed the first CPR and the survey was born. The survey was based in Hull until 1950, when it moved to Edinburgh to be join the SMBA (Scottish Marine Biological Association). It remained in Edinburgh until 1979 and then relocated to be with the IMER laboratory (now Plymoutrh Marine Laboratory) in Plymouth. In 1991 SAHFOS was established as a charitable organisation to run and maintain the survey. In 1993 the survey moved across Plymouth Hoe to the Citadel Hill Laboratory (with the Marine Biological Association) where it remains to the present day.
How does the CPR work?
The CPR is towed through the water by a ship of opportunity on a metal rope at a depth of ~10m. The water moving past the propeller turns the internal mechanisms, which moves a band of silk very slowly. Water enters the CPR at the front and plankton are filtered out onto the moving band of silk. Another band of silk overlies the filtering silk to create a 'sandwich' and then this is wound onto another spool in a tank of formalin (preservative).
The phytoplankton and zooplankton are captured on the silk and create a 'snap shot' of the planktonic community in a particular area of the sea. Since Hardy invented the CPR in 1925, scientists have discovered a whole group of organisms smaller than phytoplankton. The CPR now has new additions to its external body for collecting nano and picoplankton. Since 1994 the CPRs having been collecting temperature, pH and salinity measurements along with the plankton data.
Scientific research from the CPR survey
SAFHOS scientists work in 5 major areas of reseach. These are:
SAHFOS produces the Marine Ecological Status Report based on observations from the global Continuous Plankton Recorder survey. This publication can be downloaded as PDF here
A selection of reaseach summaries:
SAHFOS educational resources are suitable for home or the classroom
All files are in PDF format and can be downloaded using Adobe
All resources written and designed by Clare Buckland (SAHFOS Education Officer)
SAHFOS educational activities are suitable for home or the classroom.
All files are in PDF format and can be downloaded using Adobe
All resources written and designed by Clare Buckland (SAHFOS Education Officer) and Stephanie Davis
Using plankton and other marine studies in the classroom couldn't be easier!
Plankton make excellent examples in which to teach and cover a number of important key skills. We have provided resources, fact sheets and worksheets that can be incorporated into teaching any of the following topics.
Sc2: Living processes and Living things
Key Stage 1 & 2 Life processes and adaptation to habitats
Key stage 4 Primary production
Life Adrift is a work book all about plankton and the important role it plays in the marine environment. Written for Key Stage 3 (but can be adapted by teachers and parents for other Key Stage groups) it is now available to download in PDF format here
Topics covered include:
The ecology and distribution of plankton
The marine food chain and trophic levels
Photosynthesis in the marine environment
Monitoring the marine environment
Each section is concluded with a number of questions to aid learning and the answer sheet is available here.