Long-term climate-associated dynamics of a tropical seagrass meadow: implications for the future

Abstract

The long-term changes of tropical intertidal seagrass, mainly Halodule uninervis and Halophila ovalis meadows and their relationship to climate are poorly documented. Developing a greater understanding of the effects of climate on seagrass meadows is critical for estimating the effects of future climate change scenarios. Here we document the temporal dynamics of coastal intertidal seagrass in tropical northeast Australia over 16 yr of detailed monitoring. This study is the first to directly relate such change to long-term climate variability in the Indo-Pacific region and southern hemisphere. Regression modelling was used to relate seagrass biomass and meadow area measurements to climate data. The aboveground biomass and area of the meadow were correlated with the interacting factors of air temperature, precipitation, daytime tidal exposure and freshwater runoff from nearby rivers. Elevated temperature and reduced flow from rivers were significantly correlated (R 2 = 0.6, p < 0.001) with periods of lower seagrass biomass. Results of this study have important implications for the long-term viability of seagrasses with regard to climate change scenarios. Modelling of our findings indicates that future higher temperatures could be detrimental to Indo-Pacific intertidal, coastal and estuarine seagrass meadows.KEY WORDS: Climate change · Global warming · Halophila ovalis · Halodule uninervis · Temperature · Rainfall · Indo-Pacific · Queensland · Australia Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 422: [93][94][95][96][97][98][99][100][101][102][103] 2011 been lost at an unprecedented rate from a variety of anthropogenic influences (Waycott et al. 2009). Predictions of the influence of climate change scenarios on seagrass (Short & Neckles 1999, Harley et al. 2006, Poloczanska et al. 2007, Waycott et al. 2007) are largely based on incidences of seagrass loss associated with extreme weather (Cardoso et al. 2008, Micheli et al. 2008 as reported in short-term experimental studies (Campbell et al. 2006). Long-term studies directly measuring seagrass changes and how they are correlated with climate are rare. Such studies are restricted to the Mediterranean Sea and coastal areas of Florida (Marba & Duarte 1997, Tomasko et al. 2005; no similar studies have been reported for the tropical Indo-Pacific region.Throughout the Indo-Pacific region, turbid estuarine and coastal environments commonly contain abundant and productive intertidal seagrass meadows dominated by the small colonising floral species of Halodule uninervis (Forssk.) Aschers., 1882 and Halophila ovalis (R.Br.) J. D. Hooker, 1858, Coles et al. 2003. Such meadows are often spatially expansive , Coles et al. 2003 and are particularly important food sources for dugong Dugong dugong and green turtles Chelonia mydas (Bjorndal 1985, Preen & Marsh 1995. The intertidal and coastal location of these meadows makes them susceptible to large climatic events, such as flooding , Campbell & McKenzie 2004, drought...

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Thermal tolerance of two seagrass species at contrasting light levels: Implications for future distribution in the Great Barrier Reef

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