Seaweed and Plants: Multicellular Primary Producers

Types of Algae Classes Chlorophyta = Green Phaeophyta = Brown Rhodophyta = Red

Seaweeds Seaweeds are another class of primary producers. Techincally they are not weeds, but algae, and sill eukaryotic. Most biologists agree that macrophyte is a much better name. Some also call them macroalgae.

Seaweeds: Green algae Have the same pigments as land plants (chlorophyll) More than 7,000 species Marine algae are “macro” Alteration of generations

Thalus

Filamentus algae such as Ulva forms paper thin sheets.

“Dead man’s fingers,” Codium fragile and several spp. of Culerpa are know for there tube-like structures.

Padina (brown algae) with flat, calcified blades... advantage?

Phaeophyta Largest (size) and most complex of the algae Nearly all are marine (~1500 spp.) Brown color comes from accessory pigments (fucoxanthin)

Fucus sprialis a common brown algae can be found on rocky shores. Unlike other algae in this category, its thallus lacks gas bladders.

Knotted rockweed, Ascophyllum nodosum, is common to N. America and Europe.

Kelps! Kelps are the largest seaweed we encounter in the ocean. They are also the most complex. Due to this large size, many of the kelps are harvested for food! Who knows where we will find seaweed next?

Sea plam (Postelsia palmaeformis) containsinternal support structures that help them withstand wave action! It’s also eated on a regular basis as “sea noodles.”

Pneumatocysts Macrocystis pyrifera, the largest of the kelps anchors itself to the sea floor by use a massive holdfast. Here we can see not only the large blades, but the extensive pneumatocysts used for buoyancy. Rem: Pneumatocysts developed as a means to maximize energy production through photosynthesis by keeping the seaweed close to the surface.

These kelp obtain huge proportions growing as much as 0.5m/day! These when large kelp group together a kelp forest is develops. Kelp forest are great for sheltering all sorts of marine life, including Garabaldi, scallops, seals and sharks. They also provide an opportunity for selective harvesting of the upper sections of the blades for food.

Members of the species Rhodophyta red algae, are more numerous than the green and brown algae combined (if we include aquatics). Although many red algae are in fact red; due to the prescence of red pigments known as phycobilins, which mask chlorophyll, these algae may display an even greater intensity when exposed to sunlight! Nearly 4,000 marine species exist and many are used for food or other specialty products. Porphya, a “red” algae

encrusting Corallina, a coralline algae, deposits CaCO 3 within its cell walls which provides structural support and often encrusting many surrounding surfaces.

Sexual Reproduction, or not… Sexual reproduction is expensive both energetically and physiologically. Sometimes it’s better to reproduce by asexual means from fragments, spores, or buds. Sometimes algae use both sexual and asexual reproduction depending on environmental conditions.

Products from Seaweed: Phycocolloids—form gels and increase viscosity of liquids Algin—stabilizer in ice cream (Macrocystis) Carageenan—emulsifier (Irish Moss, Chondrus) Agar—jellies (and of course all your plates in microbiology, Gelidium, Pterocladiella)

Seagrasses (lillies) reproduce through rhizomes, or horizontal stems which grow beneath the sediment.

Mangroves

Mangroves thrive in salty environments and are able to obtain freshwater from saltwater. Some spp. secrete excess salt through their leaves while other block absorption of salt at their roots.

Magrove Impacts At one time, nearly 0.5 million acres of magroves surrounded Florida’s coastal zone contributing to ecosystem health in a variety of ways. - Trap and cycle organics, chemical elements, sediment and minerals. -Provide shelter for marine organisms.

Plate 9. Black Mangrove, Avecennia germinans.

Plate 8. Red Mangrove, Rhizophora mangle.

Red Mangrove

Plate 10. White Mangrove, Laguncularia racemosa.