T, Rabel H, Stevens LM. 2024. Synoptic Broad Scale Ecological Assessment of Catlins/ Pounawea Estuary. Salt Ecology Report 144, prepared for Otago Regional Council, August 2024. 74p.2016: Ground-truthing of dominant substrate, saltmarsh, macroalgae, seagrass, and terrestrial margin (200m) was undertaken by Wriggle Coastal Management over December 2016. Features were recorded directly onto rectified ~0.25m/pixel resolution colour aerial photos flown in 2014/15 and sourced from LINZ Online Data Serivce. In 2021, Salt Ecology in-house scripting was used to validate 2016 field codes and check for topology errors. In the 2016 master layer, "Orig_Code" is the original 2016 field code and "FieldCode" shows any changes made. Field codes were updated to reflect improvements to the classification of substrate and any mapping errors that were found have been corrected. Spatial accuracy for features clearly visible on aerial photos (e.g. salt marsh, cobble fields) is ~2 metres. Spatial accuracy for features difficult to distinguish on aerial photos (e.g. where boundaries represent a habitat transition from mud to sand) is ~10 to 20 metres depending on the extent of ground truth undertaken. Field codes present features in order of their dominance; e.g Lesi Sare = (Lesi (rushland) dominant to Sare (herbfield)). Vegetation height is able to be derived from the structural class of features; e.g. Lesi (rushland) is taller than Sare (herbfield). Catchment land cover was sourced from Landcare Research Land Cover Database (LCDB5, 2018). Sand and mud substrate classifications were validated through the laboratory analysis of representative samples for sediment grain size. Macroalgal features were classified based on estimated percent cover, measured biomass (g/sq m wet weight) and presence of entrainment (growing >30mm within sediment). The types, and from a range of sites with variable macroalgal cover and bio-mass. Results have been used to delineate LowO2 zones where sediment oxygen is depleted to the extent that adverse impacts to macrofauna (sediment and surface dwelling animals) are expected. Areas with a mud content >25%, sediment oxygen (aRPD) depth <10mm, macroalgal cover >50%, and elevated organic content >1% were defined as representing Gross Eutrophic Zones (GEZ).

2022: Ground-truthing of dominant macroalgae and seagrass was undertaken by Salt Ecology on 1 December 2021. Features were recorded directly onto 30 cm pixel resolution (0.30 m GSD), 3-band (RGB) uncompressed GeoTIFF colour aerial imagery captured between 12 January and 5 February primary indicators used to assess sediment oxygenation are aRPD depth and RP measured at 3cm. These indicators were measured at representative sites throughout the dominant sand and mud substrate 2021 by Aerial Surveys Ltd and supplied by ORC. Each feature was digitised and field codes recorded in a master layer used to produce individual summary output layers using in-house scripting to validate field codes and check for any errors in geometry or typology. Spatial accuracy for features clearly visible on aerial photos (e.g. dense macroalgae) is ~2 metres. Spatial accuracy for features difficult to distinguish on aerial photos (e.g. sparse macroalgal beds) is ~10 to 20 metres depending on the extent of ground-truthing undertaken. Macroalgal features were classified based on estimated percent cover, measured biomass (g/m2 wet weight) and presence of entrainment (e.g. growing as stable beds rooted within the sediment). Areas with High Enrichment Conditions (HECs) - also termed Gross Eutrophic Zones (GEZs) were defined as mud-dominated sediments (>50% mud content, based on expert judgement) with >50% macroalgal cover and with macroalgae entrained. These areas typically also have an aRPD depth shallower than 10mm due to sediment anoxia and elevated organic content (i.e. >1%)

2023 Broad Scale Mapping of the Catlins / Pounawea Estuary was undertaken by Salt Ecology on behalf of Otago Regional Council and is described in: Roberts KL, Scott-Simmonds