(1) define the objectives and intended use of the maps and spatial data and

Transcription

1 Mapping coastal seabed habitats in Tasmania: development and integration of remote sensing techniques within a hierarchical framework Alan Jordan Vanessa Halley Miles Lawler Richard Mount Project Planning (1) define the objectives and intended use of the maps and spatial data and select the appropriate scales and data resolution (2) assess the time and cost limitations of the various methods available to collect data at appropriate resolutions and spatial scales relevant to the objectives and level of habitat categorisation (3) classify habitats within a hierarchical scheme based on bio-physical characteristics (4) define and quantify spatial uncertainty (5) develop methods for integrating and displaying spatial data collected by a range of methods and at different scales and resolutions defined within the habitat classification scheme 0 1 SEAMAP Tasmania Spatial Management Mapping conducted for a range of planning and management needs: Marine Protected Area planning Marine farm planning Fisheries assessment (eg. Spatial distribution of catch, CPUE and habitat, urchin barrens, spawning beds, effects of dredging Long term habitat monitoring (eg. seagrass) Baseline environmental surveys Localised coastal developments Pollution and oil spill response Hydrodynamic modelling 2 Tasmania Marine Protected Area Planning - Bruny and Twofold bioregions completed (2500 km) Commercial fishery assessments Garfish catch 3

2 Hierarchical Hierarchical Habitats Habitats Classifications Rock/consolidated Dominant algae Reef High Profile > 4m profile Medium Profile 1-4 m Low Profile <1 m Continuous Patchy Ecklonia Phyllospora Geomorphic Type Bio-geomorphic Unit Relief Dominant biota Unvegetated Substratum Ecotype Sand Silty-sand Silt s Unconsolidated Flat Ripples Hills Sponge Scallop Species Vegetated Seagrass Dense Patch Sparse Heterozostera Halophila Posidonia 4 Hierarchical Habitats Classifications Habitat categories are based on what is definable using singlebeam acoustics, video and airborne remote sensing and prior knowledge on the factors determining community structure (e.g. reef profile, patchiness) Reef algal assemblages - (Edgar 1981, 1984, Sanderson 1984, 1987) Soft sediment fishes - (Last 1983, Jordan 1997, Jordan et al. 1998) Reef associated fishes - (Edgar et al. 1995, Murphy & Lyle 1998) Soft sediment invertebrates - (Moverley & Jordan 1996, Edgar et al. 1999) Defining lower levels in habitat classification is important to maximise the use of habitats as surrogates for species diversity 5 Aerial Photography Aerial photographs obtained mostly from existing terrestrial photographs Developing techniques for low Limited to depths <10 m altitude targeted digital photos for monitoring (ground-control, water clarity, sun glint, image processing Field Surveys Single-beam acoustics - Simrad ES60 with pole mounted 120kHz 10 o beam width transducer 6 Logs depth and differentially corrected position into SeaBed Mapper which allows habitat attributes to be logged in real time with positional data 7

3 Field Surveys Field mapping using acoustics and underwater video conducted from small vessels (5-6 m) in shallow water and larger vessels off shore (~24 m) Echogram analysis 1 Nm Survey tracks Variable track spacing Echograms logged in EchoView software and post-processed to determine habitats boundaries, primarily those with crisp boundaries 8 9 Echo Integration Integration of the tail of the first and the whole second echo post-processed in EchoView Used primarily in offshore unconsolidated habitats where most boundaries are fuzzy Issues of acoustic footprint size with depth, vessel speed, ping rate and sea conditions Underwater Video Video transects used to ground-truth acoustics and help determine habitat boundaries Qualitative/quantitative surveys Positive species ID and distribution by depth including: dominant macro algal species on reef seagrass species sponges and invertebrates Overlay position and depth on video Roughness 10 11

4 Attributed points imported from Echoview into ArcView Interpolation Reef Habitat Cross check and validation of polygons with video, real-time attribution and aerial photos Vector model used primarily in inshore areas due to crisp, complex boundaries Patchy reef <45 m depth Bathymetric contours generated using a TIN model Sponge reef >45 m depth Unconsolidated Habitats Track spacing and resolution 50 m 100 m How does track spacing affect map accuracy? Sparse Sponge Track spacing has large influences estimate of reef shape but less on reef area 200 m 50 m cross shore and 100 along shore Is there an optimal sampling density to resolve spatial patterns of marine habitats? Seagrass 14 15

5 Data presentation Sponge reef morphology Aerial photo Acoustics Video Diver Positional accuracy 1:10, m 200 m 1 transect 5m Rock type Dominant macroalgae Using photogrammetry to determine morphology of sponge dominated communities as a surrogate for diversity Software - Photomodeller, Virtuoso and WinAnalyse 16 Exposure Continuous Granite 5 m Durvillea 75% Phyllospora 25% 10 m - Phyllospora 50% Ecklonia 25% Sub-maximal 17