UNCORRECTED PROOF Seagrass as pasture for seacows: Landscape-level dugong habitat evaluation James K. Sheppard a,b, * , Ivan R. Lawler a,b , Helene Marsh a,b a School of Tropical Environment Studies and Geography, James Cook University, Townsville 4811, Australia b CRC Reef Research Centre, PO Box 772, Townsville 4810, Australia Received 6 February 2006; accepted 19 July 2006 Abstract A 24 km 2 seagrass meadow in Hervey Bay, Queensland, Australia, was confirmed as important dugong habitat by a satellite tracking study. Marine videography, near-infrared spectroscopy (NIRS) and geographic information systems (GIS) were used to survey, analyse and map sea- grass species composition, nutrient profile and patch structure at high resolution (200 m). Five species of seagrass covered 91% of the total hab- itat area. The total above and below-ground seagrass biomass was estimated to be 222.7  19.6 t dry-weight. Halodule uninervis dominated the pasture (81.8%, 162.2 t), followed by Halophila ovalis (35.3%, 16.5 t), Zostera capricorni (15.9%, 22.2 t), Halophila spinulosa (14.5%, 21.9 t), and traces of Halodule pinifolia. Because seagrass distributions overlapped, their combined percentage totalled >100% of the survey area. The seagrass formed a continuous meadow of varying density. Abiotic variables explained relatively little of the spatial patterns in the seagrass. For all seagrass species, the above-ground component (shoots and leaves) possessed greater total nitrogen than the below-ground component (roots and rhizomes), which possessed greater total starch. Because of the relatively low intraspecific variation in nutrient composition, nutrients were concentrated according to seagrass biomass density. Halodule uninervis was the most nutritious seagrass species because of its superior whole- plant nitrogen (1.28  0.05% DW) and starch (6.42  0.50 DW %) content. Halodule uninervis formed large, clustered patches of dense biomass across the pasture and thus nitrogen and starch were concentrated where H. uninervis was prevalent. This seagrass meadow appears to be utilised well below its potential dugong carrying capacity. The survey and analytical techniques used enabled rapid, economical and accurate quantifi- cation and characterisation of seagrass habitat at scales relevant to a large forager. Ó 2006 Published by Elsevier Ltd. Keywords: seagrass; dugong; habitat; nutritional ecology; GIS; patchiness 1. Introduction The spatial distribution of quality food plants profoundly influences the movement patterns and foraging behaviours of large, terrestrial, mammalian grazers, which in turn impose patterns on the landscape (for reviews see Senft et al., 1987; Coughenour, 1991; Fryxell, 1991; Huntly, 1991; Gross et al., 1995; Bailey et al., 1996; Hulme, 1996; Augustine and McNaughton, 1998; Belovsky et al., 1999; Wilmshurst et al., 1999; Van der Wal et al., 2000). The nutritional ecology of the dugong has many similarities with that of large, terrestrial, mammalian grazers. Like other free-ranging grazers, dugongs must optimise their nutrient intake by selecting quality food plants from within pasture foodscapes (sensu Gordon et al., 1996) of lower quality herbage. Dugongs are seagrass specialists, feeding almost exclu- sively on phanerograms of the families Potamogetonaceae and Hydrocharitaceae (Kingdon, 1971; Heinsohn and Birch, 1972; Husar, 1978; Marsh et al., 1982; Preen, 1995a). Seagrass communities have many similarities to terrestrial grasses, ex- hibiting spatial heterogeneity (patchiness) at a range of scales, as both continuous and fragmented landscapes interspersed with non-vegetated substrate (Lobo et al., 1998; Bell et al., * Corresponding author. School of TESAG, James Cook University, Towns- ville 4811, Australia. E-mail address: james.sheppard@jcu.edu.au (J.K. Sheppard). 0272-7714/$ - see front matter Ó 2006 Published by Elsevier Ltd. doi:10.1016/j.ecss.2006.07.006 ARTICLE IN PRESS Please cite this article as: James K. Sheppard, et al., Seagrass as pasture for seacows: Landscape-level dugong habitat evaluation, Estuarine, Coastal and Shelf Science (2006), doi:10.1016/j.ecss.2006.07.006. Estuarine, Coastal and Shelf Science xx (2006) 1e16 www.elsevier.com/locate/ecss + MODEL 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 YECSS2044_proof  12 August 2006  1/16