Phytoplankton and sampling Flashcards
What is the most abundant species of phytoplankton in the oceans?
Diatoms are one of the most abundant groups of phytoplankton in oceans, are more commonly found in temperate latitudes.
In the Atlantic they’re very dominant and form long chains to help suspend themselves in the water column in the photic zone for photosynthesis.
Which shapes can diatoms form?
Pennate = rods,bilateral symmetry (can be benthic) Only pennate diatoms are capable of locomotion – wave like motion on surface – only possible when diatom is in contact with another surface – generally restricted to shallow water sediments & surfaces larger plants/animals
Centric = petri dish shape, radial symmetry, Centric diatoms – tend to always be planktonic in the water column.
Describe the anatomy of a diatom
Diatoms all have external skeletons made of silica called the frustule which is made up of two halves.
1st half, the epitheca is larger than the other forming a ‘lid’.
2nd half, the hypotheca is smalla forming the ‘box’ part.
Describe how diatoms reproduce asexually
Parent cell divides to produce 2 daughter cells (simple asexual division. The cell forms 2 nuclei, 2 halves of frustule split. Each daughter cell grown new inner half.
Method can yield large number in short period – take advantage of improved growth conditions
This method of cell division recycles the old frustules – results slight decrease in ave. cell size with each division
Diatom forms another frustule inside the original frustrule. The epitheca grows a new hypotheca to regenerate new cell. The hypotheca becomes the new epitheca on the new cell. So cells get smaller through reproduction.
How often can diatoms divide under optimum light and nutrient conditions?
Every 12-24 hours making number swell and producing a bloom.
Describe how diatoms reproduce sexually
Due to the reduction in size during asexual reproduction, once daughter cells reach their critical minimum size sexual reproduction will take place.
Cells loose the frustule and half their genetic material.
They will meet another cell in the same condition and fuse to make a zygote which grows into an auxospore.
The frustule returns to it’s normal size so asexual reproduction begins again.
Describe a Coccolithophore
Unicellular, nanoplankton (2-20 nanometres)
Made up of round circles are coccolith plate made up of calcium carbonate. The plates come together to form a Coccolithophore. Effected by ocean acidification because they’re made up of primarily calcium carbonate. Important in the production of chalk.
They’re important in tropical and subtropical waters
Describe a Silicoflagellate
They have internal ornate silica skeletons with one or two flagella which help with mobility and many small chloroplasts.
Their contribution to primary production is smaller than that of diatoms and coccolithophores but is still significant.
Describe a Dinoflagellate
Usually solitary with two flagella and between 25-1000 nanometres.
They dominate tropical regions and autumn temperate blooms.
Most dinoflagellates possess a thick cellulose wall called a theca. Without a theca dinoflagellates are considered as ‘naked’.
These phytoplankton don’t form chains or aggregations.
What are the two types dinoflagellates and their properties
Desmophyceae
-2 longlitudunal halves with flagella both on the anterior.
Dinophyceae
-Made up of anterior and posteria halves with 1 flagella girdle and 1 flagella posterior
How do dinoflagellates reproduce asexually?
Longitudinal cell division – each new daughter cell retains part of old cell wall & rebuilds missing part after cell division
Longitudinal cell division – each new daughter cell retains part of old cell wall & rebuilds missing part after cell division
How do dinoflagellates reproduce sexually?
Sexual reproduction will only take place under very harsh conditions such as; not enough light, nutrients or too much turbidity.
New cells are dormant thick walled cysts on the seabed.
Can dinoflagellates cause a harmful toxic bloom?
Yes, their biolumin (lucifrin protein) is oxidised which is a toxin and causes harmful bloom which is of concern for the public and the environment.
What is the most common method for sampling plankton?
A large cone shaped net.
This can be used vertically, obliquely and horizontally.
It filters larger volumes so is useful for less abundant species.
Who invented the continuous plankton recorder and how does it work?
Sir Alister Hardy invented it in 1926.
The filtering silk moves around the columns continuously to allow looking at the spatial distribution of plankton. Towed off the back of the ships of opportunity. E.g the ferry that moves from Plymouth to france continuously. Like tankers for example. This has been happening since the 1930’s
