Algae II PDF

OSX-1004: Diversity of Marine Life Algae 2 Dr Martyn Kurr [email protected]  Algae teaching block structure Lecture One: Importance of algae and how we define them Types of algae and where we find them Lecture two: Morphology and growth forms of macroalgae Macroalgae dis...

OSX-1004: Diversity of Marine Life Algae 2 Dr Martyn Kurr [email protected]  Algae teaching block structure Lecture One: Importance of algae and how we define them Types of algae and where we find them Lecture two: Morphology and growth forms of macroalgae Macroalgae distribution and uses  Macroalgae (seaweeds) Generic term, but typically used to describe algae which are: Macroscopic (large, easy to see with the naked eye). Multicellular (composed of many cells, although there are a few exceptions..). Red, green or brown algae. Usually attached to substrata (known as benthic). You may see the term ‘macrophyte’ An individual seaweed is referred to as an ‘alga’, an ‘algal individual’, a ‘genet’, or sometimes a ‘plant’ (😠😒) Where do you find macroalgae? Basic morphology of macroalgae Thallus Used to define the whole organism, including stipe / fronds etc.  Basic morphology of macroalgae Blade or frond Usually found on large brown algae. Sometimes specifically adapted to tolerate wave exposure  Basic morphology of macroalgae Holdfast Anchors algae to the benthos. Has no other root-like role. Basic morphology of macroalgae Stipe Connects the blade to the holdfast. Is usually very strong.  Basic morphology of macroalgae Bladders – Known as pneumatocysts, these are gas filled and keep the thallus upright when immersed.  Basic morphology of macroalgae Receptacles – Sex organs on large brown algae.  Functional-form groups (Littler et al 1983) Group External morphology Texture Examples Sheet group Thin, tubular, and Soft Ulva, Enteromorpha, sheet like (foliose) Dictyota Filamentous group Delicately branched Soft Polysiphonia, (filamentous) Chaetomorpha, Centroceras Coarsely branched Coarsely branched Fleshy-wiry Laurencia, Chordaria, group (upright) Gracilaria, Caulerpa Thick, leathery group Thick blades and Leather, rubbery Laminaria, Fucus, branches Udotea, Chondrus Jointed calcareous Articulated, Stony Corallina, Halimeda, group calcareous, upright Galaxaura Crustose group Prostrate, encrusting Stony or tough Lithothamnion, Ralfsia, Hildenbrandia Sheet group Thin, tubular, and Soft Ulva, Enteromorpha, sheet like (foliose) Dictyota Filamentous group Delicately branched Soft Polysiphonia, (filamentous) Chaetomorpha, Centroceras Coarsely branched Coarsely branched Fleshy-wiry Laurencia, Chordaria, group (upright) Gracilaria, Caulerpa Thick, leathery group Thick blades and Leather, rubbery Laminaria, Fucus, branches Udotea, Chondrus Jointed calcareous Articulated, Stony Corallina, Halimeda, group calcareous, upright Galaxaura Crustose group Prostrate, encrusting Stony or tough Lithothamnion, Ralfsia, Hildenbrandia  Biotic and abiotic factors driving macroalgal distribution Macroalgae interact with their surrounding physiochemical environment (abiotic). Light Salinity Nutrients Wave action / tides Benthic macroalgae interact with other marine organisms (biotic). Competition Grazing  Light Light absorbance is known as attenuation  Too much light: Light Damaging UV radiation leads to photoinhibition Some species have no photoinhibition capability to maximise their light capture at extremes Can also increase temperature Too little light: Less photosynthesis. Accessory pigments Many species show plasticity; may shift pigments (photoacclimation)  Salinity Marine salinities are usually around 35 on the practical salinity scale. Intertidal seaweeds are tolerant to salinities between 10-100, subtidal less tolerant between 18-52. Ulva is a key example of a tolerant seaweed, found in estuaries and marine environments.  Nutrients Macroalgae require a range of elements to grow: nitrogen, carbon, phosphorus, iron, cobalt, manganese, zinc, copper, silicon, sulphur, potassium, sodium, to name a few The elements that usually limit growth in the intertidal marine environment are nitrogen and phosphorus. Too many nutrients can be a bad thing, resulting in rapid and excessive growth; Eutrophication. General terms: Oligotrophic: low levels of nutrients. Eutrophic: high levels of nutrients. Mesotrophic: between the two. Wave action / tides Tides expose algae to desiccation. Some are species able to withstand long periods, others not. Causes in part: zonation. Wave action can damage algae with some especially adapted to high energy environments. Many species can be characterised by their tolerance to wave energy. Ballantine exposure scale. Zonation Competition On a rocky shore, macroalgae compete for space and light The best competitors are at the bottom – abiotic conditions are more benign The worst competitors are at the top – abiotic conditions are more hostile (Chilean species) Herbivory Many herbivores consume seaweeds Seaweeds defend themselves with chemicals; unlike plants there are very few physical defences (e.g., thorns) Grazing pressure is stronger on the low shore Herbivore pressure contributes to zonation Uses of macroalgae Commercial Food Industrial Fertiliser Pharmaceutical Cosmetics Weight loss? Laboratory Agar jelly Aquaculture Bioremediation http://seaweed.ie/uses_g BNS-1001/2 – A2 Carrageenan Read some ingredients lists! Global seaweed production http://www.fao.org/docrep/019/i3344e/i3344e.pdf  Summary; lecture two of two I have this weird compulsion to stare at seaweed You should now know The basic morphology and growth forms of macroalgae The main ecological drivers of macroalgal distribution Just a few of the uses for seaweeds I desperately need to see kelp 🙁  Resources Graham, L. E. (2000). Algae. Michigan, Prentice Hall. (In the library [3 copies] but not available as an ebook)