2022-11-08 P&E Agenda - Item 6 - Attachment 1 - Current & Historical Distribution of Seagrass in the Noosa Estuary (40 pages)

                                                                  Ecological Service Professionals
                                                                                       Sustainable Science Solutions




2.3.1   Assessment of Seagrass Habitats

Where seagrass was present, the seagrass beds were assessed further for their extent
(using a hand-held GPS to later define and confirm the current perimeter of patches using
GIS by tracking along the perimeter of seagrass along a channel or around a patch in the
lakes). This was done by taking georeferenced images along the edge of seagrass beds or
walking intertidally and taking a series of points along the edge, then matching to recent
aerial imagery in ESRI ArcMap. The species composition, percent coverage and condition of
seagrass was also assessed qualitatively, based on expert assessment of georeferenced
imagery (video and photos) at more than 1700 points across the study area, using methods
adapted from Roelfsema & Phinn (2009) where a gps is either towed along the waters
surface with the type of substrate recorded either on snorkel or using a drop camera from a
boat. Broad seagrass coverage categories were either determined directly from imagery or in
the laboratory using georeferenced imagery. Georeferenced image capture enable mapping
linked to images showing the seagrass (or other benthic habitat) and allowed for rapid geo-
referenced image collection over a large spatial area of the estuary. Where identification of
the presence of seagrass was not possible from surface view imagery, a field sample was
collected using a grapple hook to confirm identification (particularly of seagrass species).

2.3.2   Seagrass Condition and Fisheries Value

The condition of representative seagrass beds in each of the estuarine reaches was
assessed along several transect completed perpendicular to the channel, with georeferenced
observations and photo quadrats made at regular assessment points (approximately every
5 m) along each transect. The value of fisheries habitat in the study area was assessed
using:
    •   desktop review of the current literature;

    •   condition and type of habitat present based on field results; and,

    •   professional judgement based on the dominant habitat category (e.g. seagrass) using
        the criteria adapted by ESP from Wetland Assessment Manual (Price et al. 2007) and
        a review of the available fisheries literature1 linking habitat features with fisheries
        productivity as outlined in Appendix A (Table 7.1 and Table 7.2).

    •   habitat patches are scored based on the presence of various criteria, with seagrass in
        better condition or having higher value to fisheries species given a higher score. The
        total is then summed across each criteria to determine whether the seagrass habitat
        is poor, fair, good or very good.




1
 Bell & Westoby 1986a, b; Edgar & Robertson 1992; Boström & Bonsdorff 1997; Heck et al. 1995;
Webster et al 1998; Skilleter et al. 2005; Vanderklift & Jacoby 2003; Boström et al. 2006; Jelbart et al.
2007; Price et al. 2007; Shoji et al. 2007.
Assessing Distribution of Seagrass in the Noosa Estuary                                                           5