Multicellular Primary Producers Seaweeds and Plants Chapter 6

All photosynthetic? Most are photosynthetic but of course there are exceptions Some are not photosynthetic and are actually parasites of other seaweeds! Almost all the seaweeds and marine plants discussed in this chapter are photosynthetic. There are always exceptions, and a few seaweeds are not primary producers but parasites of other seaweed!

The role of seaweeds Transform solar every to chemical energy in the form of organic matter Energy is then available for consumption Habitat Oxygen producers Seaweeds play an important role in many coastal environments. Seaweeds transform solar energy into chemical energy in the form of organic matter and make it available to a long list of hungry creatures. Some organisms live on or even in the tissues of seaweeds Organisms on land as well as those living in the ocean utilize some of the oxygen seaweeds produce.

Structure of seaweeds Seaweeds are eukaryotic Seaweeds still lack the specialized structures and reproductive mechanisms characteristic of terrestrial plants Wide range of variation among seaweeds The structure of seaweeds or macrophytes or macroalgea are much more complex than those of unicellular algae.

Variation Rocky shore- small and sturdy to withstand waves Some delicate ones live on other seaweeds Kelps- found offshore in cold waters (giants) The multicellular condition of seaweeds allows many adaptations not available to unicellular forms. The ability of seaweeds to grow tall and rise off the bottom provides new opportunities as well as challenges, particularly that of wave action.

General Structure Seaweeds lack true leaves, stems, and roots of plants. Thallus- Complete body Blades- Leaf-like flattened portions of the thallus, large surface area, photosynthesis Pneumatocysts- Gas-filled bladders that can keep blades close to sea surface Stipe- Stem-like structure for support, blades originate Holdfast- Attaches the thallus to the bottom and well developed in kelps Lots of variation among seaweeds. Unifying features are worth mentioning. Blades- The have a large surface area and are the main photosynthetic region though all portions of the thallus are able to photosynthesis as long as they have chlorophyll. The upper and lower surfaces of the blades are identical to each other. Most seaweeds cannot anchor in soft sediments and are restricted to hard bottoms. Water and nutrients bathe the entire thallus and are picked up directly across the surface without the need of roots as in land plants.

Structure

Types of Seaweeds Three types 1) Green 2) Brown 3) Red It is not easy to recognize the groups by their color in nature since the proportion of chlorophyll and other pigments can vary. Chemical analysis, however, reveals the characteristic pigments of each group.

Green Algae Most are freshwater and terrestrial 10% of the 7,000 species are marine Most have a simple thallus compared to the other 2 groups Thought that land plants evolved from green algae Pigments and food reserve are the same Most of the marine species are unicellular but that does not mean that multicellular green algae are uncommon in the sea. The chlorophyll is not masked by other pigments so they are typically bright green in color

Where do green algae live? Common on rocks in shallow water Rocky shore tide pools

Types of green seaweeds Filamentous types may be branched or unbranched Enteromorpha- thin thallus in the form of a hollow tube Ulva- Sea lettuce is paper thin Valonia- forms large spheres or curious spherical clusters. Caulerpa- Single giant cell with many nuclei Codium- Deadman’s fingers Halimeda- Calcareous green algae (coral reefs) Valonia forms large spheres or clusters in the tropics and subtropics. Codium- multinucleated filaments woven into a spongy, often branching thallus.

Enteromorpha

Ulva

Valonia

Caulerpa

Codium

Halimeda

Brown Algae Coloration – varies from olive green to dark brown Fucoxanthin over chlorophyll Almost all of the 1500 species are marine Often the dominant primary producers on temperate and polar rocky coasts. Largest and structurally most complex (Include the kelps) The variation in color is due to yellow-brown pigments Fucoxanthin over chlorophyll

Types of Brown Algae Ectocarpus- Finely filamentous thallus Dictyota – thallus is flat and branched Padina- Fan-shaped and lightly calcified Desmaretia- branched Some are exposed at low tides at the middle and upper levels of rocky shores Gas-filled floats – rockweeds or wracks Ectocarpus is widely distributed Desmaretia – found in cold waters Those exposed at low tides have thick leathery thalli that can withstand exposure to air.

Sargassum Brown algae found in warm waters (Gulfs of Mexico and California) Sargasso weed has spherical air bladders to keep small leaf like blades afloat Most grow on rocks Offshore in huge masses Sargasso Sea Area in Atlantic

Sargasso Sea

Sargassum Sea http://www.youtube.com/watch?v=JFxhlyJ3U4Q

Kelps Most complex and largest of all brown algae Great importance – provide food and shelter for many organisms. Laminaria- species of kelp where a single large blade can be up to 10 ft Agarum and Alaria – Rib runs along the middle of a single blade Egregia- Feather boa kelp Eisenia- Southern sea palm Nereocystis- Bull kelp Pelagophycus- Antler like branches Found in great abundance below the low tide level in temperate and sub-polar latitudes Laminaria is harvested for food in some parts of the world

Brown Algaes kelp.gifkelp.gif Padina Agarum Egregia Dictyota Ectocarpus Laninaria Desmarestia Alaria Nereocystis Eisnia Pelagophycus

Macrocystis Largest of kelps Massive holdfast attaches to the bottom At the base of each blade a gas-filled pneumatocyst Can grow 20 in per day in optimal conditions Form kelp beds or forests Among the richest, most productive environments in the marine world

Kelp Forest http://www.youtube.com/watch?v=GcbU4bfkDA4 What coast of North America can they be found? What do kelps consist of? What do young kelp compete for? What do fish use the kelp forest for? Why does the canopy make a good nursery environment? Youtube: Underwater Kelp Forests usoceangov

Red Algae More red algae that green and brown combined Red pigments known as phycobilins Essentially marine Of the 4000 species, only a few are fresh water or soil Live in most shallow-water marine environments Phycobilins mask chlorophyll.

Structure of Reds Simplified in structure by becoming parasites of other seaweeds A few have lost all chlorophyll and are heterotophs Most are filamentous Thickness, width, arrangement of filaments varies A few have lot all chlorophyll and are heterotrophs depending entirely on their host for nutrition.

Types of Reds Gelidium Gracilaria Endocladia – wirey clumps on rocky shores from Alaska to S. Ca. Gigartina- Most massive of the red algae Porphyra-Common on rocky shores above the lowest tide mark Rhodymenia –Common in North Atlantic Chondrus –Irish moss and can tolerate wide ranges in temp, light and salinity Gelidium and Gracilaria are found worldwide, there are many species of Gelidium and Gacilaria

Red Algae en Gelidium Gracilaria Porphyra Rhodymenia Endocladia Gigartina Chondrus

Coralline Algae (Corallina) Red algae that deposit calcium carbonate in their cell walls Important in several marine environments Calcified thallus takes a variety of shapes Color varies from light to intense reddish-pink Warm-water coralline algae are actively involved in formation and development of coral reefs

Bingo Thallus Blades Pneumatocysts Stipe Holdfast Green algae Red algae Brown algae Enteromorpha Ulva Valonia Caulerpa Halimeda Gigartina Chondrus Fucoxanthin Ectocarpus Dictyota Padina Desmarestia Rockweeds Sargasso Sea Laminaria Nereocystis Pelagophycus Macrocystis Kelp forest Phycobilins Coralline algae Gracilaria Porphyra