Subtidal high energy over mud

Long description

Subtidal very high to medium energy muddy ecosystems including subtidal mudbanks, muddy shoals and muddy channels, usually in shallow water resuspended into the water column, with or without sparse macrobiota. Muddy ecosystems may also include those with a proportion of gravel especially within channels and areas experiencing additional riverine and tidal current energy. Resuspension of mud may occur due to wave, current (e.g. tidal) or riverine energy however this typology maps wave energy.

Resuspension of mud or silt in the water column is problematic for photosynthetic biota such as corals and seagrasses, which need clear water to enable light penetration required to make food. Suspended sediment can also settle on the coral and seagrass ecosystems causing mortality. Extreme events such as rainfall runoff and flood plumes are known to impact coral ecosystems[3][4] and seagrass ecosystems[6][5]. Certain hard coral taxa such as the foliose (e.g. Dendrophyllids like Turbinaria mesenterina) and massives (e.g. Porites) are more tolerant of sediment suspension, low light levels and muds and these become dominant on turbid water inshore reefs[1][2]. Turbinaria mesenterina actively feeds on particles in the mud[7] and turbid water inner shelf corals may be adapted to periodic exposure to low levels of suspended sediment.

Gravelly muds may provide an attachment surface for Structural macrobiota including filter-feeders such as sea fans and other octocorallians, sponges etc.

Special values

Suspended mud in the water column is deleterious to certain corals and seagrasses, however the intrinsic values of the corals within these areas are important to maintain.

Diagnostic attributes:

Inundation 'subtidal'

Energy magnitude 'very high', 'high', 'medium'

Sediment texture 'Mud', 'gravelly Mud', 'muddy Sand', '(slightly gravelly) sandy Mud', '(slightly gravelly) Mud', 'sandy Mud'

Qualifiers

Includes mapped modified ecosystems that have modified Benthic depth and Terrain morphology including dredged channels, boat harbours, depressions near boat ramps etc. Although unmapped, Period and Trend qualifiers are also relevant as the Energy magnitude may also vary seasonally and episodically with respect to wave action.

Distribution

High energy over mud is found along the Queensland continental shelf in nearshore waters often close to areas of riverine discharge. Areas of high current velocity and muddy substrate with higher tidal range are found between Shoalwater Bay to Mackay.

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

• Gravelly muds are prevalent in the Port Curtis area where there is an abundance of rocky substrates.

Comments

Standardising wave models between local and national scales is problematic and may result in mis-matches in wave Energy magnitude mapping. Incorporating the attribute of Energy source by creating a typology of other forms of energy such as riverine and current to form a benthic stress model would more accurately model areas where mud is likely to be resuspended within the water column. Tidal range is relevant where current speeds are rapid and suspend sediment.

References

1. ^ Browne, NK (2012), 'Spatial and temporal variations in coral growth on an inshore turbid reef subjected to multiple disturbances', Marine environmental research, vol. 77, pp. 71-83, Elsevier.
2. ^ Browne, NK, Smithers, SG & Perry, CT (March 2013), 'Spatial and temporal variations in turbidity on two inshore turbid reefs on the Great Barrier Reef, Australia', Coral Reefs. [online], vol. 32, no. 1, pp. 195-210. Available at: http://link.springer.com/10.1007/s00338-012-0965-1 [Accessed 15 March 2019].
3. ^ Butler, IR, Sommer, B, Zann, M, Zhao, J & Pandolfi, JM (2013), 'The impacts of flooding on the high-latitude, terrigenoclastic influenced coral reefs of Hervey Bay, Queensland, Australia', Coral Reefs, vol. 32, no. 4, pp. 1149-1163, Springer.
4. ^ Butler, IR (2015), Flood response and palaeoecology of the high-latitude, terrigenoclastic influenced coral reefs of Hervey Bay, Queensland, Australia. PhD thesis, School of Biological Sciences The University of Queensland.
5. ^ Campbell, SJ & McKenzie, LJ (2004), 'Flood related loss and recovery of intertidal seagrass meadows in southern Queensland, Australia', Estuarine, Coastal and Shelf Science, vol. 60, no. 3, pp. 477-490, Elsevier.
6. ^ Preen, AR, Long, WJL & Coles, RG (1995), 'Flood and cyclone related loss, and partial recovery, of more than 1000 km 2 of seagrass in Hervey Bay, Queensland, Australia', Aquatic Botany, vol. 52, no. 1, pp. 3-17, Elsevier.
7. ^ Sofonia, JJ & Anthony, KRN (30 July 2008), 'High-sediment tolerance in the reef coral Turbinaria mesenterina from the inner Great Barrier Reef lagoon (Australia)', Estuarine, Coastal and Shelf Science. [online], vol. 78, no. 4, pp. 748-752. Available at: http://www.sciencedirect.com/science/article/pii/S0272771408000826 [Accessed 25 March 2019].

Last updated: 22 July 2019