BOT4404 Main Page

FIU Home

FIU Marine Biology Home

Dept. Biology Home

Frank Jochem Home


Macroalgal and Periphyton Ecology
  • Substrate: macroalga and periphyton live attached and non-motile on substrate; substrates can be rocks, corals, sand, other algae, aquatic animals
  • Light requirements for photosynthesis limits distribution to shallow, coastal areas
  • Macroalgal production is important for coastal food webs in terms of carbon fixation and as habitat for other animals and juvenile fish; production of seaweed communities and kelp forrests is a high as highest terrestrial primary production
  • Only 10% of macroalgal biomass is directly grazed by herbivores, 90% is made available to higher trophic levels by the detritus food web
  • In streams and shallow lakes, periphyton contributes more primary production than phytoplankton
  • Eutrophication can lead to overgrow of substrates and benthic communities by fast-growing macroalgae such as the green alga Cladophora
  • Community shaping factors: herbivorous grazing, competition for substrate and nutrients, pathogene attack, physico-chemical environment
The Physical Environment: Tides
  • Tides : periodical changes in the water level due to the gravitational influence of the moon (and the sun)
  • High tides occur every 12 hrs 25 min = ½ lunar day !

  • Sun and Moon and Earth…

  • Gravitational forces of sun and moon add at full and new moon to produce spring tides. Gravitational forces of sun and moon compete at half moon to produce neap tides.
  • Lunar tides occur twice a day (semidiurnal tides), solar tides once a day (diurnal tides)

  • Depending on the orbital position of sun and moon and ocean region, mixed tides occur.

The Littoral: Between Water and Air 
  • Harsh environment: loss of water at low tide; physical forces of waves; variation in temperature; UV radiation; ice formation; variation in salinity (rain exposure)
  • Adaptation of algae to life between water and air
    • Solid attachement against wave action
    • High temperature and water loss tolerance (60-90% in some algae)
    • Synchronized release of gametes
    • Cluster formation
    • Highly flexible thalli or thick, rigid thalli
  • Littoral zonation: Tides set the boundaries for permanently, periodically, and rarely submerged zones in the coastal ecosystem, the littoral
    • Eulittoral: range between mean low water and mean high water, periodically submerged
    • Supralittoral: range above the mean high water, rarely submerged
    • Sublittoral: range below the mean low water, permanently submerged
  • Zonatation of macroalgae according to resistance to wave action, falling dry, light requirements – specific for each coast and substrate

  • Wave action has positive and negative effects:

    Positive Effects
    • Reduce shading by re-arranging thalli
    • Transport and mixing of nutrients
    • Reduce thickness of boundary layer (higher uptake of nutrients and faster growth)
    • Remove sessile animals and other competitors for habitat
    • Dispersal of spores, gametes, zygotes
    Negative Effects
    • Damage, destruction, removal of thalli
    • Removal of settling zygotes/germlings
    • Expense of energy into strong holdfast and thick, rigid thallus or calcification
    • Destruction by ice floes during winter in temperate and polar regions
  • Light: High light irradiance and UV irradiation can cause photoinhibition and DNA damage; low light irradiance requires low-light adaptation by higher pigment concentrations and adjusting thallus forms
  • Light and UV protection mechanisms involve inactive photosystems, increase in accessory pigments, UV absorbants (mycosporin like amino acids)
  • Timing of growth and reproduction is triggered by light signals (sensor pigments cytochrome, phytochrome)
  • Herbivory Defense
    • Macroalgal herbivores are predominantly amphipods, copepods, polychaetes, urchins, fish
    • Chemical defense by production of secondary metabolic substances such as terpenes, alkaloids, halogenated (bromid) phenolics, and many more
    • One species can produce multiple defense chemicals
    • Structural defense by spiny or calcified thalli
    • Interaction of defense mechanisms: in the green alga Halimeda, cell division occurs at night (no visual predators), and young, less calcified cells contain more defense chemicals than older, calcified cells
    • Animals (e.g. the amphipod Ampithoe) ingest algal defense chemicals to protect themselves against grazers
      The amphipod Ampithoe uses defense chemicals from the brown alga Dictyota
    • Energetic cost: production on complex defense molecules requires energy; defended species often grow slower than species without defense chemicals; production of defense chemicals can be grazer-induced or constitutive (continuous)
  • Marine Periphyton Turfs
    • Periphyton compete for habitat space
    • Macroalgae possess mechanisms to prevent overgrowth by periphyton, such as shedding superficial cell layers or constant errosion of thallus tips
    • Turf development starts usually with diatom settlement, followed by cyanobacteria, which eventually dominate most marine turfs
    • epiphytic cyanobacteria are a major source for nitrogen fixation
    • Primary production is high per unit biomass (in contrast to macroalgae)
    • Grazing pressure on epiphyton is higher than on macroalgae; grazing helps preserving the turf by preventing dominance of larger forms and enhancing branching by grazing on filament/thallus tips 
  • Freshwater Periphyton
    • Freshwater periphyton comprises settlement on other algae/plants and microphytobenthos (on rocks and sediments)
    • Major source of photosynthetic carbon fixation in shallow lakes and streams, which do  not provide a favorable environment for plankton
    • Periphyton traps nutrients from the water and transfers them to the sediment upon death, thus preventing nutrient loss from wetlands and streams into lakes
    • Freshwater periphyton contains more bacteria and fungi than marine turfs, held together by mucilage from algae and/or bacteria
    • Metaphyton describes loose masses of epiphyton broken from their substrate and floating in the plankton

    • Grazing losses are higher than in marine epiphyton