Marine Algae

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Algae is a primitive eukaryotic autotroph that uses nutrients and sunlight to survive. Algal species do not differentiate between leaves roots and stems like land plants and they have no true vascular conduction system. Most commonly you might think of algae as a green or brown film found in a lake or pond. However, contrary to common belief, algae can grow in fresh water and in brackish or salt water. In the ocean, one can find both microalgae, on a singular cellular level, like phytoplankton, or macroalgae, on a multicellular level, like seaweed. Algae exists in multiple forms as free living (planktonic), benthic, epiphytic, endophytic and sometimes even parasitic.
The majority of the time, the algae that one may notice in the ocean is considered macroalgae or seaweed. For example, Macrocystis pyrifera (Giant Kelp) or Nereocystis luetkeana (Bull Kelp) are very common macroalgal species you would see in the ocean, especially here on the west coast of North America. Contrary to popular belief, there are over thousands of different species of seaweed. Scientists who study the biology of seaweed, phycologists, have yet to still determine every species.
Phycologists have categorized seaweeds into three categories, greens, browns, and reds otherwise referred to as Chlorophyta, Phaeophyta, and Rhodophyta. These groups are not based soley on color but also on composition, life histories, nutrient storage and transmission of nutrients throughout their thallus. Most are familiar with a group of browns called kelps. These species make up much of the seaweed canopies and make up the majority of the seaweed rack on the beach during the stormy months on the pacific coast.
Kelps, especially giant kelp and bull kelp, are known as foundation species, which ecologists commonly refer to as habitat forming species in the marine environment. Kelps provide physical structure for shelter, food, and nursery habitat to fish and invertebrates. For example, the kelp rockfish will swim vertically next to a giant kelp to stay within the kelp blades. As the surge underwater moves the blades back and forth, the fish sway with it, camouflaging themselves within the seaweed. Common subtidal and intertidal seastar species along with many other invertebrates, use the giant kelp holdfast as nursery habitat. The holdfast is full of small compartments where these invertebrates can mature while safely avoiding any contact from larger adult predators. Some may even hold young octopi. Other species and groups of seaweeds can also provide habitat or energy to their surrounding systems, especially those that live in the intertidal, like fucoids and red alga.