Seagrasses in Port Curtis and Rodds Bay 2015: annual long-term monitoring
Other Publication ResearchOnline@JCUAbstract
In brief: Seagrass monitoring in Port Curtis and Rodds Bay commenced in 2002 and has been conducted annually since 2004. In November each year 14 monitoring meadows are assessed for changes in three seagrass metrics; biomass, area and species composition (Figure 1). These monitoring meadows represent the range of different seagrass community types in Port Curtis and Rodds Bay. Changes in the seagrass metrics are used to develop a seagrass condition index (see Sections 2.5 and 3.6). This report presents results from the November 2015 monitoring survey. The overall condition of seagrasses in Port Curtis and Rodds Bay was assessed as 'Poor' mostly due to low seagrass biomass. Average biomass declined at more than half of the monitoring meadows and remained below the long-term average. Following the large declines for most meadows in 2009/10 there had been some recovery recorded in 2012 but declines for most meadows were recorded again in 2013 (Figures 2 and 3). At many meadows there has also been a shift from the once dominant Z. muelleri subsp. capricorni to the colonising Halophila species. Biomass and/or species composition has generally deteriorated at monitoring meadows from the Inner Harbour to Rodds Bay since 2014 and overall meadow condition in these zones is currently poor to very poor (Figure 3). Despite the declines in biomass and shifts in species composition, seagrass area has continued to increase with half of the monitoring meadows recording an increase in area in 2015. The total distribution of coastal seagrasses from The Narrows to the Boyne River increased by over 1000ha following reductions in 2013, and covered the greatest area since November 2009 (Figure 4). Many new or substantially expanded meadows were mapped in The Narrows and Grahams Creek zones. There were also increases in area at the intertidal/shallow subtidal Halodule uninervis meadow off Boyne Island and in the Inner and Mid Harbour zones where several small patches of Z. muelleri subsp. capricorni and H. ovalis emerged. Seagrass condition was best in the Narrows and Western Basin zones where substantial increases in area were recorded and average biomass also generally increased or remained well above the long-term average. Some meadows in The Narrows and Western Basin (e.g. Meadow 8 and Meadow 21) have also experienced shifts to less persistent species; however the majority were classed as being in an overall condition of satisfactory or better (Figure 2).
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16/04
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74
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James Cook University
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Cairns, QLD, Australia
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