Erect non-calcareous algae (macrophytes)

Long description

Ecosystems dominated by subtidal macrophytic algae (seaweed) with an erect growth form and a high level of cellular differentiation[8], on any substrate type (irrespective of consolidation). Erect macrophytic algae are usually more than 10 millimetres high and include brown algae (e.g. genera Padina, Sargassum, Lobophora, Dictyota), green algae (e.g. genera Chlorodesmium, Ulva sea lettuce, Caulerpa) or red algae (e.g. genera Asparagopsis)[6]. The kelp Ecklonia radiata is a canopy-forming brown alga that is a keystone species of temperate reefs in Australia, New Zealand and South Africa[1]. These algae are relatively anatomically complex, having specialized attachment structures to attach to the sea floor, including consolidated surfaces such as coral rubble, carbonate pavement or rock but lack roots for attachment[6]. These ecosystems may form a tall canopy that overshadows biota living on the bottom, or alternately a short canopy, depending on the seasonal factors, herbivory, nutrients and other factors that effect growth[7]

Macroalgae are a prominent component of consolidated ecosystems, including coral reefs. There are interactions between coral ecosystems and macroalgal ecosystems such that many coral reefs have shifted away from coral dominance to assemblages that include macroalgae. Causal relationships between fishing and eutrophication of waters have been implicated[2]. Macroalgae such as Sargassum spp. are associated with inshore coral reefs, colonising after disturbance and forming regular association with degraded reefs[3][4].

Special values

Macroalgae provide a major food source, cover and nurseries for herbivorous fish and other species[7]. Sargassum beds on coral reefs are intermittently and seasonally either tall or short in structure. The tall structure provides three-dimensional space for understorey algae and for fish to shelter, followed by short structure created by storms and cyclones detaching the canopy, washing it up onto the shore as debris (wrack)[7].

Kelp forests are recognised as global biodiversity hotspots for many taxa including other seaweeds, sponges, crustaceans, chordates, bryozoans, echinoderms and molluscs. They are also important fish habitats, facilitating connectivity for mobile fish species. Kelp forests may be isolated from each other and the taxa living in them are often highly endemic[1].

Diagnostic attributes

Inundation 'Subtidal'

Structural macrobiota 'Algae – erect macrophyte'

Qualifiers

Although unmapped, Period and Trend qualifiers are relevant as macroalgal growth can be seasonal and ephemeral. After a disturbance event such as floods, cyclones and coral bleaching macroalgae is often the first coloniser of impacted coral or seagrass ecosystems.

Distribution

Erect macrophytic algae are found throughout Queensland waters and are part of many ecosystem types. Kelp beds Ecklonia radiata are at their northern limits and found in very deep (greater than 60 metres) shelf waters south of Moreton Island where they may be linked with upwelling events[9].

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

• Macrophytic algae were systematically mapped within Port Curtis and outside this area are not targeted for inventory, although they may co-occur with seagrass meadows and coral reefs and many other ecosystems.
• Algal growth on coral and seagrass ecosystems can increase following episodic disturbance such as floods, cyclones or bleaching events, and chronic disturbance such as stormwater etc. where there is an increase in nutrients, sediment and freshwater. The abundance of genera Sargassum and Asparagopsis has increased in Hervey Bay and the Great Sandy Strait coral reefs following the 2011, 2012 and 2013 floods[3][5].

Comments

Other relevant attributes are those of the water column: Water temperature; Water clarity; and Benthic depth (as related to light). Energy source (upwellings) and Energy magnitude are especially relevant to the distribution of kelp forests[9].

Additional Information

Saltmarshes, seagrasses and algae - Department of Agriculture and Fisheries

Algae and algae blooms - Queensland Government

Harmful algae - Queensland Government

Algae - WetlandInfo

References

1. ^ a b Bennett, S, Wernberg, T, Connell, SD, Hobday, AJ, Johnson, CR & Poloczanska, ES (2016), 'The 'Great Southern Reef': social, ecological and economic value of Australia's neglected kelp forests', Marine and Freshwater Research. [online], vol. 67, no. 1, p. 47. Available at: http://www.publish.csiro.au/?paper=MF15232 [Accessed 15 March 2019].
2. ^ Brown, KT, Bender-Champ, D, Kubicek, A, van der Zande, R, Achlatis, M, Hoegh-Guldberg, O & Dove, SG (24 May 2018), 'The Dynamics of Coral-Algal Interactions in Space and Time on the Southern Great Barrier Reef', Frontiers in Marine Science. [online], vol. 5. Available at: https://www.frontiersin.org/article/10.3389/fmars.2018.00181/full [Accessed 15 March 2019].
3. ^ a b 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. ^ Butler, S (2015), Macquarie Dictionary. [online], Macmillan Publishers Group Australia. Available at: https://www.macquariedictionary.com.au/features/word/search/?word=macroinvertebrate&amp [Accessed 15 February 2016].
6. ^ a b Diaz-Pulido, G & McCook, L (2008), State of the Great Barrier Reef report.. [online], Great Barrier Reef Marine Park Authority, Townsville, Qld.. Available at: http://www.gbrmpa.gov.au/__data/assets/pdf_file/0019/3970/SORR_Macroalgae.pdf.
7. ^ a b c Fulton, CJ, Abesamis, RA, Berkström, C, Depczynski, M, Graham, NAJ, Holmes, TH, Kulbicki, M, Noble, MM, Radford, BT, Tano, S, Tinkler, P, Wernberg, T & Wilson, SK (29 January 2019), 'Form and function of tropical macroalgal reefs in the Anthropocene', Functional Ecology. [online], ed. C Fox. Available at: http://doi.wiley.com/10.1111/1365-2435.13282 [Accessed 15 March 2019].
8. ^ 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.
9. ^ a b Richmond, S & Stevens, T (2014), 'Classifying benthic biotopes on sub-tropical continental shelf reefs: How useful are abiotic surrogates?', Estuarine, Coastal and Shelf Science, vol. 138, pp. 79-89.

Last updated: 22 July 2019