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Plants and Algae of the Sea of Cortez

Mangrove Trees in Estero , San Carlos MexicoKingdom Plantae
True Plants

There are relatively few “true” plants in the marine environment.  Most are actually algae species, although the exact classification of algae is still hotly debated among phycologists.  While not common, the true plants are important in coastal habitats as sources of food and shelter for many species as well as shoreline stabilization.  Species include mangroves, turtle grasses etc.

bundosoma mexicana anemone in Puerto Penasco, Sonora Mexico

Kingdom Protoctista (Protista)
Algae and other Protozoa

The Kingdom Protoctista is an extremely large catchall Kingdom that is better defined by what it is not, rather than what it is.  In short, the organisms contained within this Kingdom include eukaryotes that are not plants, animals, or fungi.  For the utility of most ocean enthusiasts, these can be broadly broken down into unicellular forms (micro algae and protozoans) and multi-cellular macro algae.  For the strict phycologists and taxonomists reading, we realize such a classification probably just gave you a swearing fit and an eye twitch from which you may never recover.  We’re sorry.   

ctenophoreKingdom Protoctista
Division Chlorophyta

Green Algae

Key Features: The approximately 8000 species of green algae are a diverse lot.  They exist as both unicellular and multi-cellular organisms, in habitats as diverse as freshwater, saltwater, and even alpine snow.  Most species are found in freshwater environments.   Due to their coloration and chlorophyll compositions, they are the most depth restricted of the algae species, rarely found deeper than 20 meters.  Of the algae divisions, they are the group most closely related to the land plants, as they possess chlorophyll a and b, and store food as starch in plastids.

platyhelminthes flatworm Sea of Cortez, Baja, MexicoKingdom Protoctista
Division Phaeophyta
(Also classified as Phylum Heterokontophyta, Class Phaeophyceae)
Brown Algae

Key Features: In contrast to green algae, brown algae are a primarily marine division.  Most members of Phaeophyta are found in nutrient-rich temperate waters.  This includes Macrocystis, or kelp.  Macrocystis is among the fastest growing organisms known, with growth exceeding a half-meter per day, and an overall length of over 60m.  Within the Sea of Cortez, Padina and Sargassum are among the most abundant genera, especially in the winter.  Most members of Phaeophyta possess the pigment fucoxanthin, which gives them their characteristic coloration.

ribbon worm, nemertea, in Sea of Cortez, Guaymas, Conora, MexicoKingdom Protoctista
Division Rhodophyta

Red Algae

Key Features: The red algae, Rhodophyta, is a large group of over 5000 species, although there is little consensus as to the classification of most, even to the level of Kingdom.  Many red algae exist as the familiar seaweeds as well as some unicellular forms. There are also many species that are classified as coralline algae, in both encrusting and branching forms.  These secrete calcium carbonate into their tissues giving them a stony or “crunchy” feel.  These coralline forms play an important role in reef formation in many regions.  The red algae are also found deepest in the water column, often over 100m, depending on water clarity.  




Updated August 28, 2009

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