Reducing resilience of the Great Barrier Reef to increased temperature stress

2 thoughts on “Reducing resilience of the Great Barrier Reef to increased temperature stress”

  1. Richard, interesting post, it’s nice to see seagrasses get a mention here as they are all too often overlooked! As you point out there are various other habitats on the Great Barrier Reef that are vulnerable to the impacts of climate change.

    Seagrasses are indeed a highly important feature of coastal ecosystems, including the Great Barrier Reef. For example, seagrasses rate amongst the most valuable of the world’s ecosystems in terms of their contribution to the global economy (Costanza et al 1987) due largely to their role in nutrient cycling in coastal environments. As well as supporting biodiversity and fisheries productivity, tropical seagrasses are the sole food source for dugongs and a vital food source for marine turtles.

    As you rightly point out, one of the impacts of climate change on seagrasses will be increased frequency and severity of exposure to short periods of very high temperatures. To expand slightly: In shallow coastal habitats, water is generally more turbid than it is further away from the shore. Seagrass meadows are restricted to fairly shallow-water habitats where they receive enough light for photosynthesis (up to 70m (Short et al 2007 JEMBE 350:3-20). High turbidity in coastal areas forces seagrasses into even shallower water (Dennison et al 1993 BioScience 43: 86-94). It is these shallow water habitats that are the most susceptible to high water temperature. At low tide, in particular, they may be exposed to the air, or remain sitting in very shallow pools of water that reach 40-45°C.

    Improving water quality is critically important for the future health of seagrasses on the Great Barrier Reef. As you describe, the combined effect of higher nutrients and climate change can increase the light requirements of seagrasses, potentially forcing them into even shallower waters. Conversely, any improvements to water quality that increase light penetration will extend the habitable depth range of seagrasses, allowing them to move into deeper waters. Seagrasses growing in deeper water will be less susceptible to damaging shallow-water temperatures expected under future climate change.

    Dr Catherine Collier
    School of Marine and Tropical Biology
    James Cook University


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s