Biofilm
Response Of Basal Resources To Changing Flows
Background
Water level variations from managed flow releases are known to influence both rates of biofilm productivity (Ryder 2004) and structural attributes (Burns & Walker 2000; Ryder et al. 2006) of biofilms that inhabit hard surfaces within rivers. However, little attention has been directed at understanding how managed flows may alter the potential food quality of river biofilms and the subsequent implications for higher consumers (e.g. invertebrates, fish and water birds).
Flow directly influences biofilm communities that inhabit hard surfaces within rivers via mobilisation of carbon, nutrients (N and P), and sloughing. Hard surfaces within streams are hot spots for production, and support diverse macroinvertebrate communities; in effect, the biofilm communities are the first responders to changed flow. Biofilms are also important food sources, providing the basal resource for higher order consumers. As such, responses in biofilms can have a significant impact on community compositions at higher trophic levels. Improved biodiversity is a key target for environmental water management activities, but assessment tools and time restraints often fail to demonstrate desired outcomes. A key limitation is understanding the basal level ecology and its influence on higher trophic levels.
This project will employ biochemical and DNA techniques to measure structural and functional responses of biofilms to managed environmental flows. Biochemical tools can provide information of food nutrition, while DNA tools can provide rapid, detailed analyses of microbial communities. Applying both tools simultaneously represents a novel approach to demonstrating ecological responses to environmental water delivery. We will apply molecular DNA techniques to demonstrate how biofilm communities (from prokaryotes e.g. bacteria, through to higher eukaryotes e.g. algae, fungi and insects) respond to changing flow regimes. Our research group has previously shown that the nutritional landscape available to consumers changes with community structure. This project will investigate how community structure, and thus the nutritional landscape, responds specifically to changes in flow regime (specifically in-channel parts of the flow regime). Coupled with this, quantification of the nutritional landscape (i.e. C, N, and P) will allow us to investigate what flow regimes and what components of the community are likely to be driving changes in nutritional quality.
Objective
- Provide an improved understanding of basal level ecology and processes associated with environmental watering.
- Demonstrate the use of new tools and protocols to provide measures of ecosystem function response to flows.
- Generate information that relates biofilm functionality and community structure to specific flow variables.
Management implications
This project contributes to two objectives of the Basin Watering Strategy: Protect restore the ecosystem functions of water-dependent ecosystems and ensure that water-dependent ecosystems are resilient to climate change. This is accomplished by improving our understanding of ecosystem function in response to a range of environmental flows (base flows, freshes, bank full flows and overbank flows).
The response of basal resources to changing flows project will contribute to understanding which environmental flow regimes can best support the food webs necessary for successful breeding and independent survival of waterbirds and fish (e.g. MDB EWKR, LTIM).
Information generated from this work will provide managers with detailed basal resource responses to a range of managed flow scenarios. Managed environmental flows that are not of sufficient magnitude to inundate adjacent floodplains are routinely employed in regulated rivers, and are generally seen as beneficial to ecosystems. However, empirical data describing such benefits are scarce, and managers currently lack information surrounding the influence of flow magnitude and timing on basal resource food quality. This information is key for prioritisation of water resources for maximum ecological benefit, since basal resources sit at the foundation of all aquatic food webs.
References
Burns A, Walker KF (2000) Effects of water level regulation on algal biofilms in the River Murray, South Australia. Regulated Rivers: Research & Management 16, 433-444.
Cook, R.A., Gawne, B., Petrie, R., Baldwin, D.S., Rees, G.N., Nielsen, D.L. & Ning, N.S.P. (2015) River metabolism and carbon dynamics in response to flooding in a lowland river. Marine and Freshwater Research, 66, 919-927.
Ryder DS (2004) Response of epixylic biofilm metabolism to water level variability in a regulated floodplain river. Journal of the North American Benthological Society 23, 214-223.
Ryder DS, Watts RJ, Nye E, Burns A (2006) Can flow velocity regulate epixylic biofilm structure in a regulated floodplain river? Marine and Freshwater Research 57, 29-36.