lecture ?: sandy shores and micro organisms

sample collected on 27 oct morning at beach at fornebu

labs on thrusday and friday

collected top 20 centimetres

used using a bailer in the hydropsammon

preparation - incubation - examination

• place sand sample in petri dish

• cover with lens paper

• the organisms should crawl onto the coverslips and those slips will be moved onto a microscopy slide

• add coverslips and/or microscopy slide

• examination of coverslips under light microscope

teh habitat

• beach

• influenced by:

  • temperature

  • salinity

  • wave action (wind, tides)

  • grain size

  • light

• depending on the coarsness of the grains, it can control how much light can penetrate into the sand

• around the world, the temperature varies greatly

nutrients

• the organisms that live in teh beach need nutrients to grow

• the organic material that washes up onto the beach decompose, which provides enough nutrients to the animals living in that area and microbes in the sand

• poor water has more nutrients than the water above

dryness - wetness

• the swash zone → never totally dries out

• beaches can be very different:

  • some can be very sheltered or very exposed

  • protected beaches:

    • fine sediments

    • large wave periods

    • shallow slope

    • benign swash conditions

    • rich fauna

  • exposed beaches:

    • sand grains are larger

    • small wave periods

    • steeper slope

    • harsher swash conditions

    • fauna less rich

  • these are the extreme ends on the type of beaches

morphodynamic spectrum

• dissipative beaches →

• reflective beaches →

average particle size affect physico-chemical conditions

• small particle size - large surface

• mud retain water better than sand

• gradients on concentration of free oxygen

• in mud teh surface area, the number of bacteria, and organic ocntent of hte sand are high

• in sheltered ares, the oxygen is depleted withing the first 10 cm, due to low wave action. when there is highere wave actions in more exposed beaches, the sund in the beach is moved more around and oxygen is penetrated deeper

size ranges of grains and organisms

• grain size structures the habitat and influences what kind of organisms that will live there

organisms living in sandy beaches

• macrofauna → > 500 µm

• meiofauna → 100-500 µm, e.g. flatworms and nematodes

• microfauna → <100 µm

microflora and fauna of sandy beaches

• important groups:

  • cyanobateria

  • ciliates

  • euglenozoa

  • dinoflagellates

  • haptophytes

  • cryptomonads

  • heterokonts

  • cercozoa

  • incerta sedis

cyanobacteria

• photsynthetic bacteria

• contain chlorphyll a

• phycocyanin (blue)

• phycocerathrin (red)

euglenozoa

• characcterisitcs: …

• majority are heterotrophs

• dominating group in the psammon (sandy habitat)

• genera and species differ from thos in th eplankton

• reducing environments: thrive in environments with low oxygen

dinoflagellates

• characteristics: amphiesma some with cellulose plates (armour/ theca), two flagella often in furrown, dinokaryon

• heterotrophic and photosynthetic species common

• most species in psammon lack theca

• many genera in common with plankton, species differ

cilliates

• characterisitcs: cilia

• heterotrophic, some inhabit anoxic habitats

• some have symbiontic algae, e.g. mesodinium pulex

stramenopiles

• characterisitcs: two flagella, one smooth, teh other with tripartite hairs

• many calsses

• heterotrophic, phototrophic

• consists of diatoms (silicified frustules, lack flagella, all phototrophic) and raphidophytes (naked)

haptophytes

• characteristics: haptonema, organic scales (a few coccoliths), smooth flagella

• a few representatives in the psammon, mainly planktonic

cryptomonads

• characterisitcs: two flagella with bipartite hairs, periplast

• heterotrophic and photosynthetic

chlorophyta (archaeplastida)

• photosynthetic

• characteristics: smooth flagella, green chloroplasts

adaptations

• living on and between sand grains

• gliding - diatoms - raphe, extruding mucus

• flagellates - swim

• cells oftne flattened

• costs very little energy to move the flagella

• vermiformed organisms

surf zone diatoms

• solid line - floating cells

• dashed line - mucus coating

• dotted line - dividing cells

• predators: Donax and Emerita

coloration of the sand

• the coloration can be casued by diatoms, dinoflagellates, chlorphytes, euglenophytes

• they form green, golden brown or brown patches ont he surface of hte mosit sand or shallow water sediments

• dinofalgellates aoccur in large numbers

vertical migration 

euglenophytes

• diurnal pattern of vertical migration

• cells on the surface during the day

• tidal migration pattern with cells on the beach surface only during daytime tide and more than 15 cm below the surface during daytime high tides and at night

diatom

• tidal rhythm

• on intertidal sand and mud flats

• at low tide golden brown pathces on the surface of intertidal sandflats

• at high tide up to 2 cm below the sediment surface

bias when collection 

• record only the organisms that attach to teh coverslip

• if the ice method is used, only organisms that are driven out of the sand by the temperature gradient will be seen

microalgae; species identification

• …..