Hot Topics in Ecology

Climate change: underwater forest decline

Loss of kelp forest places commercial fisheries at risk
Synthesis by Dr Adriana Vergés, UNSW Australia, and A/Prof Thomas Wernberg, University of Western Australia
  • Ocean warming is causing a ‘tropicalisation’ of temperate reefs in eastern and western Australia, leading to a decline in canopy seaweeds that fulfil a role similar to trees in forests.
  • Increasing temperatures have direct negative effects on cool water seaweeds and can also increase the rate at which herbivores eat them, leading to overall seaweed decline
  • The disappearance of canopy seaweeds changes community structure, impacts biodiversity, and can lead to the collapse of Australia's most valuable commercial fisheries
Rabbitfish (Siganus spp.) are one of the main warm-affinity species observed overgrazing seaweed forests in Japan, the Mediterranean and Australia. Photocredit: Adriana Vergés

Ocean warming causes physiological stress in cool water species and facilitates the expansion of warm water species onto temperate reefs. This is leading to range contractions of important cool water organisms such as canopy seaweeds, which fulfil a role similar to trees in forests. These underwater forests provide food and shelter to hundreds of species, and support Australia's most economically important fisheries, such as rock lobster and abalone.

Increased temperature impacts seaweeds directly and indirectly, e.g. via effects on species that eat them. In Tasmania, warming has been directly linked to a decline in giant kelp forest canopy cover of over 90% since the 1940s. In Western Australia, an extreme heat wave caused the disappearance of several dominant seaweeds over ~ 100 km.

The greatest indirect impacts of warming in seaweed forests are caused by herbivore consumers. As the distribution of warm water herbivores expands, cool water seaweeds that have evolved under low levels of herbivory face increasing herbivore diversity and grazing intensity. In Tasmania, warming has led to the range expansion of a sea urchin that has overgrazed kelp forests. Similarly, increased feeding by tropical and subtropical fishes is increasing herbivore pressure on seaweeds near the warm edge of their distribution.

The climate-mediated loss of seaweeds has reduced the biodiversity of temperate reefs in Tasmania and the Mediterranean, and has been linked to the collapse of commercial fisheries in Japan. Elsewhere in Australia, climate change is emerging as a key threat to algal forests and the species they support.

Hot Topic Lead Author: 
Name: Adriana Verges
Email: a.verges@unsw.edu.au
Phone: 02 93852110

Date approved: 
Thursday, October 8, 2015 - 19:53
ID Title Location Type
7916 Basford A. J., Feary D. A., Truong G., Steinberg P. D., Marzinelli E. M. & Vergés A. (2015) Feeding habits of range-shifting herbivores: tropical surgeonfishes in a temperate environment. Mar Freshw Res. Sydney Surveys and aquaria experiments
7920 Wernberg T., Russell B. D., Moore P. J., Ling S. D., Smale D. A., Campbell A., Coleman M. A., Steinberg P. D., Kendrick G. A. & Connell S. D. (2011) Impacts of climate change in a global hotspot for temperate marine biodiversity and ocean warming. J Exp M Temperate Australia Regional review
7904 Johnson C. R., Banks S. C., Barrett N. S., Cazassus F., Dunstan P. K., Edgar G. J., Frusher S. D., Gardner C., Haddon M., Helidoniotis F., Hill K. L., Holbrook N. J., Hosie G. W., Last P. R., Ling S. D., Melbourne-Thomas J., Miller K., Pecl G. T., Richard Eastern Tasmania Regional review
7906 Wernberg T., Russell B. D., Moore P. J., Ling S. D., Smale D. A., Campbell A., Coleman M. A., Steinberg P. D., Kendrick G. A. & Connell S. D. (2011) Impacts of climate change in a global hotspot for temperate marine biodiversity and ocean warming. J Exp M Temperate Australia Regional review
7831 Bennett, S., T. Wernberg, E. S. Harvey, J. Santana-Garcon and B. J. Saunders (2015). Tropical herbivores provide resilience to a climate-mediated phase shift on temperate reefs. Ecology Letters 18(7): 714-723. Port Gregory, Western Australia Surveys and experiments
7439 Bates A. E., Pecl G. T., Frusher S., Hobday A. J., Wernberg T., Smale D. A., Sunday J. M., Hill N. A., Dulvy N. K., Colwell R. K., Holbrook N. J., Fulton E. A., Slawinski D., Feng M., Edgar G. J., Radford B. T., Thompson P. A. & Watson R. A. (2014) Defini Generic context, Australian examples Global review
7440 Johnson C. R., Banks S. C., Barrett N. S., Cazassus F., Dunstan P. K., Edgar G. J., Frusher S. D., Gardner C., Haddon M., Helidoniotis F., Hill K. L., Holbrook N. J., Hosie G. W., Last P. R., Ling S. D., Melbourne-Thomas J., Miller K., Pecl G. T., Richard Eastern Tasmania Regional review
7441 Steneck R. S. & Johnson C. R. (2013) Kelp forests: dynamic patterns, processes and feedbacks. In: Marine Community Ecology (eds M. Bertness, B. Silliman and J. J. Stachowicz) pp. 315-36. Sinaur Associates Inc. Global Review
7442 Vergés A., Steinberg P. D., Hay M. E., Poore A. G. B., Campbell A. H., Ballesteros E., Heck K. L., Booth D. J., Coleman M. A., Feary D. A., Figueira W., Langlois T., Marzinelli E. M., Mizerek T., Mumby P. J., Nakamura Y., Roughan M., van Sebille E., Gupt Worldwide Global review
7409 Booth D. J., Figueira W. F., Gregson M. A., Brown L. & Beretta G. (2007) Occurrence of tropical fishes in temperate southeastern Australia: Role of the East Australian Current. Estuarine, coastal and shelf science 72, 102-14. New South Wales (Australia) locations from Red Rocks to Bittangabee Survey
7410 Booth D. J., Bond N. & Macreadie P. (2011) Detecting range shifts among Australian fishes in response to climate change. Mar Freshw Res 62, 1027-42. World wide and Australian focus Review
7411 Cheung W. W. L., Meeuwig J. J., Feng M., Harvey E., Lam V. W. Y., Langlois T., Slawinski D., Sun C. & Pauly D. (2012) Climate-change induced tropicalisation of marine communities in Western Australia. Mar Freshw Res 63, 415-27. Model simulation
7413 Feary D. A., Pratchett M. S., J Emslie M., Fowler A. M., Figueira W. F., Luiz O. J., Nakamura Y. & Booth D. J. (In press) Latitudinal shifts in coral reef fishes: why some species do and others do not shift World wide Review
7414 Figueira W. F. & Booth D. J. (2010) Increasing ocean temperatures allow tropical fishes to survive overwinter in temperate waters. Global Change Biol 16, 506-16. New South Wales (Australia) locations from Solitary Islands to Merimbula Surveys and modelling
7416 Ling S. D. (2008) Range expansion of a habitat-modifying species leads to loss of taxonomic diversity: a new and impoverished reef state. Oecologia 156, 883-94. Bicheno, eastern Tasmania Manipulative experiment
7417 Ling S. D., Johnson C. R., Frusher S. D. & Ridgway K. R. (2009) Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift. Proc Natl Acad Sci USA 106, 22341-5. Eastern Tasmania, Australia Combination of natural experiment (historical and contemporary contrasts inside/outside sanctuaries) and manipulative experiment (urchin predation) in the field and aquaria
7418 Nakamura Y., Feary D. A., Kanda M. & Yamaoka K. (2013) Tropical fishes dominate temperate reef fish communities within western Japan. Plos One 8, e81107. Southwestern Japan (Tosa Bay) Survey
7419 Sala E., Kizilkaya Z., Yildirim D. & Ballesteros E. (2011) Alien marine fishes deplete algal biomass in the eastern Mediterranean. Plos One 6, e17356. SW Turkey Manipulative experiment
7420 Sen Gupta A., Brown J. N., Jourdain N. C., van Sebille E., Ganachaud A. & Vergés A. (In press) Episodic and non-uniform migration of thermal habitats in a warming ocean. Deep Sea Research Part II: Topical Studies in Oceanography. Worldwide Historical observations and model simulation
7421 Serisawa Y., Imoto Z., Ishikawa T. & Ohno M. (2004) Decline of the Ecklonia cava population associated with increased seawater temperatures in Tosa Bay, southern Japan. Fish Sci 70, 189-91. Tei (Kochi), southern Japan Surveys/ review
7422 Smale D. A. & Wernberg T. (2013) Extreme climatic event drives range contraction of a habitat-forming species. Proceedings of the Royal Society B: Biological Sciences 280. Southwestern Australia, Jurien Bay Natural experiment (before-after comparison)
7424 Vergés A., Tomas F., Cebrian E., Ballesteros E., Kizilkaya Z., Dendrinos P., Karamanlidis A. A., Spiegel D. & Sala E. (2014) Tropical rabbitfish and the deforestation of a warming temperate sea. J Ecol 102, 1518-27. Eastern Mediterranean (Turkey & Greece) Surveys and manipulative experiment
7425 Wernberg T., Russell B. D., Moore P. J., Ling S. D., Smale D. A., Campbell A., Coleman M. A., Steinberg P. D., Kendrick G. A. & Connell S. D. (2011) Impacts of climate change in a global hotspot for temperate marine biodiversity and ocean warming. J Exp M Temperate Australia Regional review
7426 Wernberg T., Russell B. D., Thomsen M. S., Gurgel C. F. D., Bradshaw C. J. A., Poloczanska E. S. & Connell S. D. (2011) Seaweed communities in retreat from ocean warming. Curr Biol 21, 1828-32. Southwestern and Southeastern Australia Analysis of herbarium records
7427 Wernberg T., Smale D. A., Tuya F., Thomsen M. S., Langlois T. J., de Bettignies T., Bennett S. & Rousseaux C. S. (2013) An extreme climatic event alters marine ecosystem structure in a global biodiversity hotspot. Nature Clim. Change 3, 78-82. Southwestern Australia, Jurien Bay & Hamelin Bay Natural experiment (before-after comparison)
7428 Wernberg T., Thomsen M. S., Tuya F., Kendrick G. A., Staehr P. A. & Toohey B. D. (2010) Decreasing resilience of kelp beds along a latitudinal temperature gradient: potential implications for a warmer future. Ecol Lett 13, 685-94. Southwestern Australia, Kalbarri, Jurien Bay, Perth, Hamelin Bay Comparative experiment (surveys and manipulations along natural gradient)
7429 Yamaguchi A. (2010) Biological aspects of herbivorous fishes in the coastal areas of western Japan. Bull Fish. Res. Agen. 32, 89-94. Kyushu and Okinawa, southern Japan Animal tracking, surveys, experiments, morphological traits
7370 Bates A. E., Barrett N. S., Stuart-Smith R. D., Holbrook N. J., Thompson P. A. & Edgar G. J. (2014) Resilience and signatures of tropicalization in protected reef fish communities. Nature Clim. Change 4, 62-7. Tasmania (Maria Island Reserve; Australia) Comparative experiment (reserve vs no-reserve contrast) over a temporal gradient in warming

Further information about this topic contact:

Adriana Verges
a.verges@unsw.edu.au
02 93852110

Chair, Hot Topics Editorial Board
Dr Rachel Standish
R.Standish@murdoch.edu.au