Subtidal other habitat forming biota

Long description

Subtidal gardens dominated by other benthic macroinvertebrates including sponges, bryozoans, polychaetes, ascidians, hydroids or zooanthids. Density of these ecosystems is highly variable and they may co-occur in association with other ecosystems such as seagrass meadows, soft coral gardens, gravels, muds and sands, or consolidated ecosystems. There may be evidence of Infauna utilisation, (e.g. mounds, burrows, other forms of bioturbation, tubes). Depending on the proportions of Octocorallians, these ecosystems may grade into the reefal gardens ecosystem types (98, 117). Depending on the proportion of algae that is present, they may grade into algal-dominated unconsolidated ecosystems (54, 55, 59 or 61).

Special values

High densities of other habitat forming biota are biodiverse and add to the three dimensional structure of the sea floor.

Sponge gardens in particular are high diversity ecosystems providing living space for a range of sessile and mobile fauna, notably fish dependent on sponges and other biota for food. These gardens usually have a high diversity of sponge species and growth forms.

Diagnostic attributes

Inundation 'Subtidal'

Structural macrobiota (any of the following) 'Sponges', 'Ascidians', 'Crinoids', 'Tubeworms', 'Bryozoans', 'Barnacles', 'Other fauna', 'Other flora'

Qualifiers

Cover qualifier is relevant as different densities characterise different communities. The Naturalness qualifier may be relevant where seabed is trawled or dredged.

Period and Trend qualifiers are also relevant, as the dominant biota may vary between years and seasons. Depending on the cover of octocorallians or algae, these ecosystems may switch to other types (see above).

Distribution

Likely to occur throughout Queensland subtidal waters, in a range of different locations.

The following relates to distribution of this ecosystem type within the Central Queensland mapping area:

• Subtidal other habitat forming biota were systematically mapped in Port Curtis. In Port Curtis, these ecosystems were either low density, medium density or high density, according to their association with open unconsolidated substrates (sand and mud) , sand and shell with small amounts of hard coral (i.e. gravels, muddy and sandy gravels), live and dead rock and rubble (i.e. gravels and boulders) and reef (i.e. consolidated substrates). The dominant structural taxa were filter feeders and suspension feeders i.e. bivalves, polychaetes and bryozoans (both encrusting and erect forms) and other taxa present included isolated hard corals, octocorallians (sea fans, sea pens, soft corals), zoanthids and hydroids[1].
• Examples of sponge gardens occur in the Great Sandy Strait Ramsar area in association with soft coral gardens or otherwise (Little Woody Island and adjacent to southern Woody Island) in deep waters (~14m).
• Swales in very deep water off Rooney’s Point, northwest of Fraser Island are known to support sponges in association with other reefal garden assemblages (Stevens, pers. comm.)

Comments

Consider also Consolidation and Sediment texture for predicting where the different densities of habitat forming biota occur. Energy source and Energy magnitude relevant as filter feeders such as sponges rely on high current energy to extract their food. Further work and especially inventory is required to better characterise these ecosystems. Offshore inventory within the Great Barrier Reef lagoon has determined broad patterns of biota generally outside State coastal waters (including other habitat forming biota). Terrain morphology may be relevant as these ecosystem types may be associated with swales or depressions (Stevens, pers. comm.).

Additional Information

Seabed Biodiversity on the Continental Shelf of the Great Barrier Reef World Heritage Area 2003 - 2006 (CRC Reef, CSIRO) - eAtlas

Great Sandy Marine Park Regional Profile: Northern Great Sandy Strait - Department of the Environment, Tourism, Science and Innovation"

References

1. ^ McKenna SA, Bryant CV, Tol SJ & Rasheed MA (2013), 'Baseline Assessment of Benthic Communities (algae and macro‐invertebrates) in the Port Curtis Region. November 2013', JCU Publication, Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER) Publication, Cairns, 26pp, vol. 14/54, JCU Publication, Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER) Publication, Cairns.

Last updated: 22 July 2019