Methods for mapping seagrass distribution

McKenzie, Len J.

doi:10.1016/b978-044450891-1/50006-2

Cited by 104 publications

(111 citation statements)

References 9 publications

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“…The boundaries of the seagrass meadow were mapped by means of GPS from aerial (helicopter) surveys conducted at low tide when the seagrass meadow was exposed. Data were digitised to a GIS basemap (McKenzie et al 2001) with ArcGISs (Environmental Systems Research Institute). The GIS basemap was constructed from a 1:25 000 vertical aerial photograph rectified and projected to Geodetic Datum of Australia (GDA 94) coordinates.…”

Section: Methodsmentioning

confidence: 99%

“…The GIS basemap was constructed from a 1:25 000 vertical aerial photograph rectified and projected to Geodetic Datum of Australia (GDA 94) coordinates. The precision of determining the seagrass meadow boundary was expressed as an estimate of reliability (R) (McKenzie et al 2001). The reliability estimate ranged between ±10 and 15 m for the surveys and was based on the accuracy of obtaining position fixes for boundary mapping sites (McKenzie et al 2001).…”

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confidence: 99%

“…The precision of determining the seagrass meadow boundary was expressed as an estimate of reliability (R) (McKenzie et al 2001). The reliability estimate ranged between ±10 and 15 m for the surveys and was based on the accuracy of obtaining position fixes for boundary mapping sites (McKenzie et al 2001).Seagrass aboveground biomass sampling. Aboveground biomass data for seagrass meadows were col-94 Rasheed & Unsworth: Climate-associated dynamics of a tropical seagrass meadow lected at seagrass habitat characterisation sites scattered randomly within the mapped seagrass meadow.…”

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confidence: 99%

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

Rasheed¹,

Unsworth²

2011

Mar. Ecol. Prog. Ser.

105

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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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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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

Rasheed¹,

Unsworth²

2011

Mar. Ecol. Prog. Ser.

105

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“…Meadows chosen for monitoring were lower littoral (rarely exposed to air) and subtidal (~2 m depth). Field survey methodology followed Seagrass-Watch standard protocols [78]. Sites were defined as a 50 mˆ50 m or 50 mˆ6 m area, for lower littoral and subtidal, respectively, within a relatively homogenous section of a representative seagrass community/meadow.…”

Section: Seagrass Monitoring Programsmentioning

confidence: 99%

Estimating the Exposure of Coral Reefs and Seagrass Meadows to Land-Sourced Contaminants in River Flood Plumes of the Great Barrier Reef: Validating a Simple Satellite Risk Framework with Environmental Data

et al. 2016

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River runoff and associated flood plumes (hereafter river plumes) are a major source of land-sourced contaminants to the marine environment, and are a significant threat to coastal and marine ecosystems worldwide. Remote sensing monitoring products have been developed to map the spatial extent, composition and frequency of occurrence of river plumes in the Great Barrier Reef (GBR), Australia. There is, however, a need to incorporate these monitoring products into Risk Assessment Frameworks as management decision tools. A simple Satellite Risk Framework has been recently proposed to generate maps of potential risk to seagrass and coral reef ecosystems in the GBR focusing on the Austral tropical wet season. This framework was based on a "magnitudeˆlikelihood" risk management approach and GBR plume water types mapped from satellite imagery. The GBR plume water types (so called "Primary" for the inshore plume waters, "Secondary" for the midshelf-plume waters and "Tertiary" for the offshore plume waters) represent distinct concentrations and combinations of land-sourced and marine contaminants. The current study aimed to test and refine the methods of the Satellite Risk Framework. It compared predicted pollutant concentrations in plume water types (multi-annual average from 2005-2014) to published ecological thresholds, and combined this information with similarly long-term measures of seagrass and coral ecosystem health. The Satellite Risk Framework and newly-introduced multi-annual risk scores were successful in demonstrating where water conditions were, on average, correlated to adverse biological responses. Seagrass meadow abundance (multi-annual change in % cover) was negatively correlated to the multi-annual risk score at the site level (R 2 = 0.47, p < 0.05). Relationships between multi-annual risk scores and multi-annual changes in proportional macroalgae cover (as an index for coral reef health) were more complex (R 2 = 0.04, p > 0.05), though reefs incurring higher risk scores showed relatively higher proportional macroalgae cover. Multi-annual risk score thresholds associated with loss of seagrass cover were defined, with lower risk scores (ď0.2) associated with a gain or little loss in seagrass cover (gain/´12%), medium risk scores (0.2-0.4) associated with moderate loss (´12/´30%) and higher risk scores (>0.4) with the greatest loss in cover (>´30%). These thresholds were used to generate an intermediate river plume risk map specifically for seagrass meadows of the GBR. An intermediate river plume risk map for coral reefs was also developed by considering a multi-annual risk score threshold of 0.2-above which a higher proportion of macroalgae within the algal communities can be expected. These findings contribute to a long-term and adaptive approach to set relevant risk framework and thresholds for adverse biological responses in the GBR. The ecological thresholds and risk scores used in this study will be refined and validated through ongoing monitoring and assessment. As uncertainties are red...

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“…Mapping of seagrass in intertidal zones and shallow water is relatively easy, with many techniques available (McKenzie et al 2001); however, all rely on the ability to locate a seagrass meadow and to map edges or features that can be georeferenced. Georeferencing is simple and quick in intertidal zones and down to depths where free-divers or SCUBA divers can reasonably operate (i.e.…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of deepwater seagrass in the inter-reef lagoon of the Great Barrier Reef World Heritage Area

Coles¹,

McKenzie²,

De’ath³

et al. 2009

Mar. Ecol. Prog. Ser.

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Seagrasses in waters deeper than 15 m in the Great Barrier Reef World Heritage Area (adjacent to the Queensland coast) were surveyed using a camera and dredge (towed for a period of 4 to 6 min); 1426 sites were surveyed, spanning from 10 to 25°S, and from inshore to the edge of the reef (out to 120 nautical miles from the coast). At each site seagrass presence, species, and biomass were recorded; together with depth, sediment, secchi, algae presence, epibenthos, and proximity to reefs. Seagrasses in the study area extend down to water depths of 61 m, and are difficult to map other than by generating distributions from point source data. Statistical modeling of the seagrass distribution suggests 40 000 km 2 of the sea bottom has a probability of some seagrass being present. There is strong spatial variation driven in part by the constraint of the Great Barrier Reef's long, thin shape, and by physical processes associated with the land and ocean. All seagrass species found were from the genus Halophila. Probability distributions were mapped for the 4 most common species: Halophila ovalis, H. spinulosa, H. decipiens, and H. tricostata. Distributions of H. ovalis and H. spinulosa show strong depth and sediment effects, whereas H. decipiens and H. tricostata are only weakly correlated with environmental variables, but show strong spatial patterns. Distributions of all species are correlated most closely with water depth, the proportion of medium-sized sediment, and visibility measured by Secchi depth. These 3 simple characteristics of the environment correctly predict the presence of seagrass 74% of the time. The results are discussed in terms of environmental dynamics, management of the Great Barrier Reef province, and the potential for using surrogates to predict the presence of seagrass habitats.KEY WORDS: Seagrass · Trawling · Depth · Marine park · Halophila spp. Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 392: [57][58][59][60][61][62][63][64][65][66][67][68] 2009 their connectivity to the coral reef ecosystem, the impacts of fishing, global threats from climate change, global declines of coral reef ecosystems and on the biodiversity of the system as a whole (Day et al. 2000).In the early 1990s coastal management agencies recognised the value of seagrass meadows to coastal fisheries in the northern Australian region , Watson et al. 1993, and subsequent studies have reinforced the value of seagrasses as part of coastal ecosystems worldwide (Larkum et al. 2006. Seagrasses are a functional grouping of vascular flowering plants which can grow fully submerged and rooted in soft bottom estuarine and marine environments. Seagrasses are rated the third most valuable ecosystem globally (on a per hectare basis), and the average global value for their nutrient cycling services and the raw product they provide has been estimated at US$ 19 004 ha -1 yr -1 (at 1994 prices; Costanza et al. 1997). In tropical and subtropical waters, seagrasses are also important as...

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Methods for mapping seagrass distribution

Cited by 104 publications

References 9 publications

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

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

Estimating the Exposure of Coral Reefs and Seagrass Meadows to Land-Sourced Contaminants in River Flood Plumes of the Great Barrier Reef: Validating a Simple Satellite Risk Framework with Environmental Data

Spatial distribution of deepwater seagrass in the inter-reef lagoon of the Great Barrier Reef World Heritage Area

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