Browsing by Author "Kattel, G"

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    The indirect response of an aquatic ecosystem to long-term climate-driven terrestrial vegetation in a subalpine temperate lake
    (John Wiley & Sons, Inc, 2017-12-15) Beck, KK; Fletcher, MS; Kattel, G; Barry, LA; Gadd, PS; Heijnis, H; Jacobsen, GE; Saunders, KM
    Aim To assess whether climate directly influences aquatic ecosystem dynamics in the temperate landscape of Tasmania or whether the effects of long-term climatic change are mediated through the terrestrial environment (indirect climate influence). Location Paddy's Lake is located at 1065 m a.s.l. in temperate north-west Tasmania, a continental island south-east of mainland Australia (41°15–43°25′ S; 145°00–148°15′ E). Methods We developed a new 13,400 year (13.4 kyr) palaeoecological dataset of lake sediment subfossil cladocerans (aquatic grazers), bulk organic sediment carbon (C%) and nitrogen (N%) and δ13C and δ15N stable isotopes. Comparison of this new data was made with a recently published pollen, geochemistry and charcoal records from Paddy's Lake. Results Low cladoceran diversity at Paddy's Lake is consistent with other temperate Southern Hemisphere lakes. The bulk sediment δ15N values demonstrate a significant lagged negative response to pollen accumulation rate (pollen AR). Compositional shifts of dominant cladoceran taxa (Bosmina meridionalis and Alona guttata) occur following changes in both pollen AR and pollen (vegetation) composition throughout the 13.4 kyr record at Paddy's Lake. The δ15N values demonstrate a significant positive lagged relationship to the oligotrophic:eutrophic cladoceran ratio. Main conclusions Long-term changes in cladoceran composition lag changes in both pollen AR and terrestrial vegetation composition. We interpret pollen AR as reflecting climate-driven changes in terrestrial vegetation productivity and conclude that climate-driven shifts in vegetation are the principal driver of the cladoceran community during the last ca. 13.4 kyr. The significant negative lagged relationship between pollen AR and δ15N reflects the primary control of vegetation productivity over within-lake nutrient status. Thus, we conclude that the effects of long-term climate change on aquatic ecosystem dynamics at our site are indirect and mediated by the terrestrial environment. Vegetation productivity controls organic soil development and has a direct influence over lake trophic status via changes in the delivery of terrestrial organic matter into the lake. © 2017 John Wiley & Sons Ltd
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    Palaeoecological evidence for sustained change in a shallow Murray River (Australia) floodplain lake: regime shift or press response
    (Springer Link, 2017-02-01) Kattel, G; Gell, PA; Zawadzki, A; Barry, LA
    Paleolimnological techniques can reveal long-term perturbations and associated stable state transitions of lake ecosystems. However, such transitions are difficult to predict since changes to lake ecosystems can be abrupt or gradual. This study examined whether there were past transitions in the ecological regime of Kings Billabong, a shallow River Murray wetland in southeast Australia. A 94-cm-long core, covering c. 90 years of age, was analysed at 1 cm resolution for subfossil cladocerans, diatoms and other proxies. Prior to river regulation (c. 1930), the littoral to planktonic ratios of cladocerans and diatoms, and bulk sediment δ13C values were high, while the period from c. 1930 to c. 1970 experienced considerable changes to the wetland ecosystem. The abrupt nature of changes of planktonic cladocerans and diatoms, particularly after the onset of river regulation (1930s), was triggered by inundation, high rates of sedimentation and shifts in bulk sediment δ15N values. However, the transition of a once littoral-dominated community, to one favouring an increasingly turbid, plankton-dominated trophic condition following river regulation was relatively slow and lasted for decades. The progression to a new regime was likely delayed by the partial recovery of submerged plant communities and related internal dynamics.© 2016, Springer International Publishing Switzerland.
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    Paleolimological investigation of the use of stable isotopes of carbon and nitrogen in bulk sediment and cladoceran zooplankton to reveal ecosystem changes in Kings Billaong Northwest Victoria, Australia
    (University of Western Australia, 2013-07-10) Kattel, G; Gell, PA; Zawadzki, A; Barry, LA
    Northwest Victoria hosts a large number of shallow floodplain wetlands along the Murray River system. One of these, Kings Billabong, is known for its high conservation values. However, the naturally occurring flood pulses, which maintain ecological connectivity between river and wetlands, have been altered impacting the ecology of Kings Billabong. The human-induced river regulation in the Murray River following the arrival of Europeans, and increased farming activities around Mildura for irrigation, has switched Kings Billabong to a permanent water regime resulting in accelerated sedimentation rates and changed sources of carbon and, subsequently, altered ecological character. This study focuses on a 90 cm long sediment core taken from Kings Billabong in 2011, where the 210Pb dating detected sediments at c. 60 cm depth to be c. 65 years old. Around this time (c. 1940-1945 AD), a systemic change occurred in the billabong. The enrichment of carbon substantially declined, while, in the meantime, nitrogen enrichment increased. Coincidently, the subfossil cladoceran zooplankton assemblages revealed changes in the limnological conditions of the wetland ecosystem. Among the littoral species, the Chydorus sphaericus group, which prefers eutrophic water, became dominant. Since the early 2000s, the abundance of Biapertura affinis, a pioneer plant dwelling species, has declined. Before the assemblage of B. affinis began to decline, a large number of cladoceran ephippia were recorded in sediment samples indicating the elevated stress in the wetland. This study suggests that paleolimnological investigations, together with the use of stable isotopes of carbon and nitrogen in sediment samples, provides an opportunity to reveal the impacts of anthropogenic disturbances on the floodplain wetlands of the Murray River system across northwest Victoria, and potentially more widely across Australia. © The Authors.