Multi-cellular Primary Producers: Seaweeds and Plants Multi-cellular algae are commonly referred to as seaweeds Seaweeds belong to Kingdom Protista, and are further classified into divisions (or phylum) according to their characteristic color (pigmentation) Like unicellular algae, all multi-cellular algae are eukaryotic

Three Domains of Life Kingdom Protista

Multi-cellular Algae: Seaweeds Seaweeds are more formally referred to by biologists as macrophytes or macroalgae Seaweeds are not plants and so lack true leaves, stems, and roots The complete body is known as the thallus whether it is a filament, a thin leafy sheet, or a giant kelp

General Structure All portions of the thallus are capable of photosynthesis The leaf-like, flattened portions of the thallus are known as blades – large surface area; main photosynthetic region Gas-filled bladders known as pneumatocysts help keep the blade close to the sea surface Some seaweeds have a distinctive, stem-like structure, the stipe, which provides support

Plant Algae

General Structure A structure resembling roots, the holdfast, attaches the thallus to the bottom – NOT involved in any significant absorption of water and nutrients – Does not penetrate through sand and mud as true plant roots do Restricts seaweeds to hard bottoms; not found in sandy, soft bottom habitats Water and nutrients are transferred directly across the surface of the thallus

Types of Seaweeds There are three types of seaweeds – The green algae – The brown algae – The red algae

Green Algae: Phylum Chlorophyta Green algae belong to phylum (or “division”) Chlorophyta Most green algae live in freshwater and terrestrial environments; only ~10% of the estimated 7,000 species are marine Nonetheless, many species of green algae dominate bays and estuaries and isolated tidal pools on rocky coasts

Green Algae: Phylum Chlorophyta Chlorophyll in both green algae and plants are not normally masked by other pigments Land plants are believed to have evolved from green algae; considered by many taxonomists as belonging to Kingdom Plantae!

Common Long Island Chlorophytes Codium fragile (“Dead Man’s Fingers”) Ulva lactuca (“Sea lettuce”) Enteromorpha sp. (“Gutweed”)

Brown Algae: Phylum Phaeophyta Brown algae belong to phylum (or “division”) Phaeophyta Color varies from olive green to dark brown, but are classified by having a preponderance of yellow-brown photosynthetic pigments, particularly fucoxanthin Nearly all 1,500 species are marine Include the largest and most complex seaweeds

Brown Algae: Phylum Phaeophyta Many species have gas-filled floats (pneumatocysts); e.g., rockweeds or wracks, Sargassum weed

Brown Algae: Phylum Phaeophyta The kelps are the most complex and largest of all brown algae – Consist of a single, or numerous large blade(s) – The stipes of giant kelp, Macrocystis can reach lengths of 100 m and grow ~1 ft per day! – Provides food and shelter for many other marine organisms

KELP!!!

Kelp community with sea otters Kelp community without sea otters

Red Algae: Phylum Rhodophyta Red algae belong to phylum (or “division”) Rhodophyta There are more species of marine red algae than green and brown algae combined! The chlorophyll of red algae is masked by large amounts of red pigments called phycobilins Nearly all 4,000 species are marine Dominate in tropical and subtropical regions

Common Long Island Rhodophytes Chondrus crispus (“Irish moss”) Palmaria palmata (“Dulce”) Porphyra sp. (“Laver”)

Multi-cellular Primary Producers: The Plants Worldwide, there are 5,000-6,000 species of seaweed and only 55 species of seagrass! Seagrasses are flowering plants belonging to the kingdom Plantae – Not actually a grass – Related to lilies; evolved from land plants! – True leaves, stems, and roots

Seagrasses Underground roots and rhizomes (horizontal stems) extract nutrients from the sediment and hold the plant in its place Seagrasses have cell walls made out of cellulose (a characteristic of all plants) which provide support for the plant and keep the plant vertical in the water column

Seagrasses Seagrass provides important shelter and food for many marine inhabitants Because of the protection they provide, seagrass communities serve as important nursery grounds for developing fish & shellfish

Common seagrass of Long Island Zostera marina (“Eel grass”)

How NOT to drive your boat through seagrass...