The effects of urban geochemical modification on endangered Blue Mountains Upland Swamps

Abstract

Catchment urbanisation is associated with the global degradation of freshwater ecosystems, including poor water quality, sediment contamination and exotic weed invasions. Urban ecosystems are identified as exhibiting distinct patterns of elevated major ions (including calcium, potassium and bicarbonate) and metals, referred to as the 'urban geochemical signature'. However, the implications of this modified urban fingerprint on physical, chemical and biological attributes of sensitive freshwater systems is not well-known. Blue Mountains Upland Swamps are listed as an 'endangered ecological community' under State and Federal legislation and are home to a range of endangered flora and fauna. These ecosystems provide a unique case study to examine the effects of catchment urbanisation on a fragile freshwater environment with high conservation value. This study investigated whether urban Blue Mountains Upland Swamps exhibit altered elemental composition compared to naturally vegetated swamp catchments. Water, sediment and foliage chemistry was assessed within four urban and four naturally vegetated Blue Mountains Upland Swamp catchments, through field monitoring and a range of routine and innovative laboratory techniques (including scanning electron microscopy, x-ray diffraction and acid digestion methods). Urban swamps exhibited a distinct elemental signature compared to naturally vegetated swamps. Water in urban swamps displayed higher pH, ionic strength and had elevated concentrations of major ions (particularly calcium and bicarbonate) and metals (including strontium, barium, manganese and iron). Sediment from urban swamps had higher concentrations of calcium, with calcium hydroxide detected at two of the urban sites. Analysis of foliage tissue suggested the potential for foliage from urban catchments to exhibit higher concentrations of calcium, bicarbonate and potassium compared to non-urban catchments, however there was variability between sites and exotic and native species. Urban development alters natural hydrology and channels surface runoff into concrete drainage infrastructure, which can modify water chemistry. Findings from this study suggest that urbanisation remains a potential source of chemical modification within BMUS. Understanding the impacts of urban development is key to guiding management and promoting conservation within fragile environments. In an increasingly urban world, this research can be applied at local and international scales, assisting to identify the ecological consequences of urbanisation and shape management approaches within fragile freshwater environments.

Date of Award	2018
Original language	English