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NORTHWESTERN GULF OF MEXICO
HABITAT CLASSIFICATION

Exploration and mapping activities in and around the sanctuary have led to an updated habitat classification scheme for the Northwestern Gulf of Mexico. The original scheme was proposed by early explorers and marine biologists, Tom Bright, Richard Rezak and Dave McGrail, to name a few.

Fish Communities Associated with Benthic Biological Zones at the Flower Garden Banks National Marine Sanctuary and other Banks in the Northwestern Gulf of Mexico (3MB pdf)
- poster presented by Marissa Nuttall at GCFI 2013

Biological Zone: Coral Reef

Major Habitats: coral reef community, Montastraea, Orbicella, Madracis, Stephanocoenia, carbonate sand (reef-derived sediments)

Large boulder of mountainous star coral on a reef
Montastraea faveolata

Biology: Montastraea, Orbicella, Stephanocoenia, Madracis, Agaricia, sponge, mixed coral, leafy algae, hardbottom community, sand community

Large colony of boulder star coral layered out in plates.
Montastraea franksi

Geomorphological Descriptors: coral reef, patch reef, carbonate sand

Large area of small branching corals
Madracis auretenra (formerly mirabilis)

The coral reef zone is the shallowest zone, occurring at depths of approximately 18-45 m (59-148 ft).  This zone is characterized by a high cover of coral assemblages dominated by Montastraea and Orbicella species, Pseudodiploria strigosa, Porites astraeoides, Colpophyllia natans and Stephanocoenia intersepta.  Coralline algae, filamentous and leafy algae also occur on reef substrates, but are not dominant members of the benthic assemblage.  Madracis auretenra (formerly mirabilis) forms large monotypic stands in deeper portions of the coral reef community.  Sponges and Agaricia species are common in crevices and cavities of the reef.  Sand patches and channels are prevalent throughout the reef.

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Biological Zone: Coral Community

Major Habitats: coral community, Millepora-sponge, sponge, leafy algae/sponge, low density coral

Variety of fish swimming over small, clustered corals at Stetson Bank
A coral community with a concentration of Madracis decactis on top of one of the pinnacles at Stetson Bank.

Biology: Millepora-sponge, sponge, leafy algae/sponge, low density coral, mixed coral, leafy algae, sand community, hardbottom community

Geomorphological Descriptors: patch reef, hardbottom

Reef scene dominated by algae and sponges
A coral community dominated by algae and sponges.

The coral community (formerly known as the low-diversity coral reef) is characterized by the blushing star coral (Stephanocoenia intersepta), the large star coral (Montastraea cavernosa), fire coral (Millepora alcicornis), and the large grooved brain coral (Colpophyllia natans), and occurs between depths of 40-55 m (131-180 ft).  The lettuce corals (Agaricia species) and brain coral (Pseudodiploria strigosa) are also an important part of the community.  Crustose coralline algae are the dominant encrusting form on dead coral rock, along with leafy algae and numerous sponges.  The dominance of hard corals declines with depth, and few coral colonies occur between 45-50 m (147-180 ft).

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Biological Zone: Coralline Algae

Major Habitats: algal nodules

Biology: sand community, Madracis, leafy algae/sponge, octocoral, antipatharian, mixed coral, sponge, algal pavement, leafy algae, rhodolith assemblage, tilefish mound

Geomorphological Descriptors:   algal nodules, honeycomb reef, patch reef, molluscan reef, hardbottom, pavement

Rocky nodules encrusted with purplish algae and orange sponges.
Algal nodules

Major Habitats: coralline algal reefs

Biology: sand community, leafy algae/sponge, octocoral, antipatharian, octocoral/antipatharian, mixed coral, algal pavements, sponge

Geomorphological Descriptors: algal nodules, honeycomb reef, patch reef, hardbottom, hardbottom reef, pavement, molluscan reef

Reef surface encrusted with purplish algae and orange sponges
Coralline algal reef

The coralline algae community at the Flower Garden Banks sanctuary (formerly known as the algal/sponge zone) is dominated by crustose coralline algae, forming individual algal nodules or rhodoliths, or forming large plates and ridges that develop into massive reef structures.  A variety of sponge species are abundant in this zone, along with numerous antipatharians and octocorals.  Few reef-building corals occur at these depths, and are mostly limited to small isolated colonies.  A variety of leafy algae fields are also present.

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Biological Zone: Deep Coral

Major Habitats: deep reef

Biology: octocoral, antipatharian, stony corals, sponge/coral, mixed coral, sponge

Deep reef covered in green bottlebrush corals
Deep coral zone

Geomorphological Descriptors: patch reef, highly eroded patch reef, hardbottom, rubble, molluscan reef, hardbottom reef

Large red and orange crinoid spread like a flower amid soft corals in white and yellow on a deep reef
Red crinoid among gorgonians in deep coral habitat.

The deep coral community (formerly known as the drowned reef zone) occurs below water depths that support active photosynthesis.  The deep coral community is characterized by a diverse assemblage of antipatharian and gorgonian corals, crinoids, bryozoans, sponges, azooxanthellate branching corals, and small, solitary hard corals.  Rock surfaces are often highly eroded and lack coralline algal growth.  Reef outcrops may be covered with a thin layer of silt.

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Biological Zone: Soft Bottom Community

Major Habitats: soft bottom community

Dead sea biscuit shell partly covering an anemone on a soft sediment bottom
A sea biscuit shell partially covers an anemone living
in a soft bottom community.

Biology: bacterial mats, antipatharian fields, stony corals, octocorals

Splotchy white and greenish brown patches covering soft bottom habitat.
Bacterial mat

Geomorphological Descriptors: silt, fine sediments, coarse sediments, carbonate rubble, patch reef, hardbottom, burrows, patterned burrows, mound, pit

A burrow dug into soft bottom sediments on the ocean floor.  The sediment surrounding half of the opening looks honeycombed.
Squat lobster burrow in soft bottom sediments at McGrail Bank.

Deeper areas of the sanctuary are characterized by a soft, level bottom community composed of both terrigenous sediments originating from coastal rivers and carbonate sediments resulting from erosion of rocky outcrops and coral reef communities.  Few conspicuous fishes and invertebrates occur on soft bottom communities when compared to coral reef or rocky zones.  Soft bottom communities are often characterized by sand waves, burrows and mounds.   Transitional zones between soft bottom communities and hard bottom features are characterized by exposed rubble, isolated patch reefs or exposed hardbottom.  Areas with buried or exposed rubble are often colonized by antipatharians, octocorals or solitary hard corals.

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Interactive Map

In 2009, the sanctuary research team partnered with the National Coastal Data Development Center (NCDDC) to make this information available in the form of a GIS-based mapping tool.  We are using this website to highlight, amongst other things, the deeper water habitats in the NW Gulf of Mexico.

Image of an interactive map showing a photo linked to a specific location on the map
Example of a habitat photo linked to an ROV track on
our interactive map tool.

To access the map, just click on the button below or an identical button on our home page.

Map Tool button

The map is a work in progress, so check back regularly!

For more information about the development of this map and how to use it, please visit our Interactive Mapping Tool page.

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weather report observations cool stuff get wet


Orange, branching gorgonian (soft coral) anchored in a bed of sponges and other sea life.
   
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