Plankton Flashcards
What are the 2 types of plankton?
Phytoplankton - photosynthetic protests including diatoms and dinoflagellates
Zooplankton- diverse, contains the holoplankton (organisms that spend their entire lives as plankton) and the meroplankton (temporary members of the plankton, often larval forms)
Define the 4 vertical distributions associated with plankton
Pleuston - sea surface. Transport more often determined by wind than by currents
Neuston- within 10mm of the surface, not always easy to separate from the Pleuston and concepts may be combined
Epipelagic - 200-300m, includes the euphotic (sunlit for sufficient light for photosynthesis) and disphotic (twilight) zones
Mesopelagic - 200/300-1000m, dark zone that contains some unusual plankton
Advantages and disadvantages of the Neuston lifestyle?
Adv. rich in organic matter - upper few mm 10-1000X richer in Bacteria Buoyant eggs Dis. High infrared and UV light Little phytoplankton Extreme temperature fluctuations Aerial and aquatic predators
Give an 2 examples of planktonic animals found in the Neuston zone
Glaucus atlanticus - sea slug that can feed on the Portuguese man-o-war (Physalia physalis) and transfer its nematocysts to itself for its own protection
Vellela vellela - by-the-wind sailor, colony of Hydrozoa that make up one large organism
Name some examples of holoplankton and how many approx species/phyla there are
Protests Cnidaria, Ctenophora Annelida Mollusca Crustacea Chaetoagnatha Chordata ~7000 spp. 15 phyla
What are some points with regards to the meroplankton?
Larvae form the bulk of the meroplankton
Representatives from all phyla and all marine habitats
Many species go through a series of different larval stages and so diversity of larvae is greater than the diversity of species
Many fish have planktonic eggs and larvae
What stresses do planktonic life face and give an example?
Mortality rates are extremely high (>99%)
Due to predation, sinking and food availability
Example - losses of oyster larvae off Holland are 14% per tidal cycle. Of 3 million eggs produced by a clam Mya arenaria only 0.001% survive to settle (leaves just 10 clams)
How do plankton avoid predation?
Camouflage - transparency is often utilised by plankton eg. Spiny lobster
Deterrent - spines can serve as mechanical deterrents eg. Crab zoea has 6 major spines that armour It against would be predators
Escape and evasion - nerve cells detect predators and immediately move away from the danger eg. Copepods initiate series of kicks with their antennules
How do plankton stay afloat?
Many are denser than water and so;
- some actively swim
- some have appendages to increase drag and reduce sinking
- small size
- buoyant compounds
What advantages re there to being a planktonic larvae?
Exploitation of temporary food sources - phytoplanktonic blooms
Colonisation of new habitats
Expansion of geographical range
Avoidance of catastrophe due to local habitat failure
Avoidance of local and sibling competition
What are the different patterns of DVM?
Nocturnal DVM - shallower depth at night, deeper during the day
Twilight DVM - less common, up at dusk down during the night up again at dawn and down again during the day
Reverse DVM - up during the day down at night
What are the main advantages of DVM?
Avoidance of predators - less vulnerable to visual predators if they remain in the dark
Production and energetics - non feeding time in deeper, colder water saves energy, overall phytoplankton production greater if feeding discontinuous
Horizontal movement - water currents move at different speeds at different depths
Light damage avoidance
What are the ecological consequences of DVM?
Enhances genetic exchange by mixing members of a population
Active vertical transport of organic materials
What is the importance of plankton?
Foundation of many marine food chains
Provide other ecosystem services such as active distribution of organic carbon
Many are the larval stages of larger adult animals such as fish, crabs, mussels etc.
