Vertical Migration

By

Kip Atwater

What is it?• Vertical migration refers to a pattern of movement that some

organisms undertake involving traveling to the surface then descending to darker depths (vertically in the water column)– Can be “diel vertical migration” which is vertical migration that follows a

pattern every 24 hours • Some organisms move up during the day for photosynthesis and then

move deeper at night to obtain nutrients• Some organisms move up at night to feed and then move deeper in

the day to avoid predation

Diel Vertical Migration in Benthic Diatoms

• Mitbavkar and Anil 2004 experiment on benthic diatoms

• Vertical migration allows for the desirable acquisition of light despite tide and irradiance changes in the environment

• Diatoms kept in the dark showed that internal clocks set up constant vertical migration rhythms even in the absence of tide or light

• Diatoms kept in constant light environment changed rhythm and spent 18 hours at the surface before migrating down

• Concluded that irradiance is the major factor in vertical migration compared to tide changes for these organisms

Dinoflagellates Display Diurnal Vertical Migrations

• Anissa Merzouk et al. 2004 study on dinoflaggellates Alexandrium tamarense and Scrippsiella trochoidea

• Allows the use of nutrients at depth at night and solar radiation close to the surface during the day

So What?• Anissa Merzouk et al. 2004 linked

DMS and DMSP production to vertical migration in these dinoflagellates

• Dissolved DMSP and DMS exhibited diel patterns with minimum concentrations during the night and maximum concentrations around noon

• Causes large fluctuations in DMSP and DMS concentrations throughout the day

• So…vertical migration is affecting the atmosphere, climate, and sulfur cycle. Now that’s neat-o!

If you weren’t convinced…

• 15% of atmospheric DMS comes from the ocean

Vertical Migration and Biofilms

• Underwood et al. 2005 measured species composition and productivity of estuarine microphytobenthos (MPB)

• The constant effectiveness of MPBis important because they can contribute up to 50% of the total carbon in estuaries

• Vertical migration of individual species was hypothesized to change the compostion of the biofilm– Changing species composition should allow for high rates

of production during changing environmental conditions

Vertical Migration and Biofilms: Results

•Early in the diel pho-toperiod ambient light levels were low and small naviculoid, and Nitzschia-type cells covered larger cells of Pleurosigma and Gyrosigma •Changes in species composition can occur through two methods•clear evidence of upward migration was visible in the orientation of larger taxa within the sediment and their orientation when arriving at the surface. These larger taxa appeared at the surface from 1100 h on•Evidence of downward migration was observed in P. vitrea which moved down before midday, whereas other species, notably G. balticum and N. dubia, were observed moving down in intact biofilms under high irradiances•The intertidal biofilms showed sequential species change in the surface layers and followed a diel rhythm•this vertical migration of individual species is presumed to prevent photodamage and maintain biofilm productivity

• This just shows how each species of algae has a different photochemical efficiency as the day goes on, so by changing the species composition, the biofilm can be most effective

Sources• Merzouk A., M. Levasseur, M. Scarratt, S. Michaud, and M. Gosselin.

Influence of dinoflagellate diurnal vertical migrations on dimethylsulfoniopropionate and dimethylsulfide distribution and dynamics. Can. J. Fish. Aquat. Sci. (2004) 61: 712–720

• Mitbavkar, S., and A. C. Anil. Vertical migratory rhythms of benthic diatoms in a tropical intertidal sand flat: influence of irradiance and tides. Marine Biology. (2004) 145: 9–20

• Underwood, G. J. C., R. G. Perkins, M. C. Consalvey, A. R. M. Hanlon, K. Oxborough, N. R. Baker, and D. M. Paterson. Patterns in Microphytobenthic Primary Productivity: Species-Specific Variation in Migratory Rhythms and Photosynthetic Efficiency in Mixed-Species Biofilms. American Society of Limnology and Oceanography. (2005) 50-

3: 755-767