Lecture 7: Seagrasses

• Seaweeds lack roots, stems, leaves and their color is determined by pigments
• Seaweeds reproduce asexually through sporophytes (diploid stage that produces spores) or sexually through gametophytes (haploid stage that produces gametes)
• Alternation of Generations defined as having two or more sexual stages in succession
• Alternation of Generations can be isomorphic or heteromorphic
• Isomorphic refers to the gametophytes and sporophytes being identical
• Heteromorphic refers to the gametophyte and sporophyte stages being different
• Green algae are isomorphic
• Brown algae is heteromorphic
• Red algae has three phases of alternation of generations, where there is a third stage with a carposporophyte
• Green algae (Chlorophyta) have chlorophyll a,b and carotenoids as pigments

  They make up 13% of marine algae and are mostly unicellular
• Response of green algae to herbivory:

  Tolerance: rapid growth and large release of spores and gametophytes

  Avoidance: small size

  Deterrence: calcium carbonate deposits and toxins
• Red algae (Rhodophyta) have chlorophyll a,d and phycobilins as pigments

  Make up 98% marine algae and are mostly found in tropical waters in the shallow and intertidal zones
• Response of red algae to herbivory: less edible, changing growth patterns, evolving complex life cycles, grown in crevices
• Brown algae (Phaeophyta) have chlorophyll a,c carotenes, and xanthophylls as pigments

  Make up 99.7% marine algae and are diverse in temperate waters in intertidal and shallow subtidal zones
• Red algae is the most diverse algae
• Marine flowering plants are referred to as Anthophyta
• Three main types of Anthophyta: sea grasses (hydrophytes), salt marsh plants, mangroves
• Seagrasses occur in shallow temperate, subtropical, and tropical regions
• Two common submergent types of seagrasses: turtlegrass and eelgrass
• Seagrasses only contribute to 1% of primary production
• Salt marsh plants are mostly emergent and are found in temperate climate zones
• Salt marshes play an important ecological role in food chains, shelter/refuge, feeding grounds, and as nurseries for other marine organisms
• Mangroves are scrubby tree-like plants that are adapted to sea shore life in semi-sheltered areas
• Mangroves help stabilize sediments and filter run off from the land
• Mangroves are primarily found in tropical climate zones