Honours supervisors and projects

Prof Sam Lake

Aquatic Ecology

Telephone: 9905 5653
Email: sam.lake@sci.monash.edu.au

General areas of research centre on community ecology of freshwater ecosystems (both standing and freshwater) and adjoining ecosystems, such as estuaries and riparian zones. Particular areas of research include the effects of abiotic disturbances (e.g., floods and droughts) and invading species on community structure, the effects of interspecific interactions (predation, competition), evaluation of the links between biodiversity and ecological processes, and restoration ecology as applied to freshwater ecosystems. There is a variety of possible Honours projects available, some of which are listed below.

1. Utilization of detritus in heavily sedimented streams

(This project is linked with a major stream restoration project centred on the "Granite Creeks" near Euroa in central Victoria.) This project has two components; comparison of rates of leaf breakdown at restored and unrestored control sites and the comparison of rates of breakdown for leaves on the streambed surface and buried in sand sediment.

2. Stream drift in heavily sedimented streams in comparison with intact streams

(Again linked with the "Granite Creeks" project.) Is drift an important process in the dynamics of the fauna in heavily sedimented streams?

3. Interactions between introduced and native freshwater snails

Two snails the New Zealand mud snail Potamopyrgus antipodarum and Physa acuta occur in freshwater ecosystems of south-eastern Australia. As they co-occur, do they interact (positively or negatively)? This could be investigated in both the field and the laboratory. (With Dr Fred Govedich).

4. The influence of nutrient availability on population growth of the New Zealand mud snail (Potamopyrgus antipodarum)

It has been suggested that the nutrient content of food (C:N, C:P) strongly influences somatic growth in P.antipodarum, but does this also mean that population growth and hence ability to be a swamping invader is strongly nutrient dependent.

5. Habitat use, diet and potential impacts of the introduced fish, Roach (Rutilus rutilus)

Roach a cyprinid fish introduced from Europe, is locally abundant in waters of southern Victoria. Virtually nothing is known about its biology in Victoria and yet with its high local abundance, it could potentially be adversely affecting native biota. This project is one of description and exploration. (With Dr Nick Bond).

6. Wood packs in streams

Detritus accumulations in streams are seen as important patches of faunal diversity and ecological processing. Using standard pieces of wood, the question of does diversity change with patch size (i.e., amount of wood) and with spatial configuration (isolated versus aggregated) can be examined in experiments? (With Dr Nick Bond)

7. Ecology of wood-dwelling beetles

Aquatic beetles in the family Elmidae are widespread and patchily abundant in temperate streams in Australia. The larvae and adults of these beetles are associated with and feed on bits of wood. There are four genera (Austrolimnius, Kingolus, Simsonia and Notriolus) commonly found in south-eastern Australian streams. Do these beetles consume wood in different ways and do they construct different types of galleries and tunnels? This study in resource partitioning is experimental and can be carried out in the laboratory. (With A. Glaister).

8. What are the relative roles of light, nutrients and flow in driving benthic algal biomass and production in Australian lowland streams?

(Jointly supervised with Paul Reich and Slobodanka Stojkovic ) Australia’s inland waterways comprise many small streams with highly degraded red gum dominated riparian vegetation- much of which is being actively restored. However, very little is known about the rate, magnitude and timing of any changes resulting from riparian restoration. Moreover we still lack a good understanding of the processes that might drive these changes.One of the main driving forces in stream ecosystems is the activity of benthic microalgae. They are significant primary producers and influence nutrient cycling. These organisms respond to, amongst other things, nutrient levels and light climate, which in turn are both influenced by riparian vegetation. Streams with degraded riparian zones often experience elevated light and nutrient regimes. As riparian zones are restored we might expect changes to occur in the production and biomass of benthic algal populations as shade increases and nutrients from the surrounding catchment are trapped and taken up by plants.

Questions that might be tackled include: What are the independent and interactive effects of light and nutrients on benthic algae? Is algal production limited by the relatively open canopy of a red gum riparian forest or do nutrients play the major role?

How do low flow periods influence spatial patterns of benthic algal production and biomass? Many small lowland streams seasonally disconnect to form a series of pools during summer, and our preliminary data show that within a single stream reach these pools differ substantially in their physico-chemical parameters. Do these differences translate into differences in benthic algal production and biomass? Could we expect these differences to diminish under a lower light regime?

Artificial substrates can be used to monitor algal colonization and biomass, and can also be used to provide measurements of respiration and production processes. Oxygen probes can also be deployed in situ at the same time to relate processes on a system scale to the ones observed from biofilms on the substrates. Measurements of benthic algal production and nutrient loads could also be taken from natural substrates by removing benthic cores from selected locations and investigating their metabolic processes.

The project would link to a larger study in the SOB lead by Dr Paul Reich and Prof Sam Lake that aims to evaluate the effectiveness of riparian restoration in streams of the Murray-Darling Basin, and understanding of the processes involved in ecosystem recovery.

9. Dissolved organic nitrogen (DON) - a fuzzy component of the aquatic nitrogen cycle.

(Jointly supervised with Dr Nick Bond, Dr Assaf Sukenik [sabbatical visitor in SBS] and Dr Phil Heraud.

In both marine and freshwaters, the concentration of dissolved organic nitrogen (DON) frequently exceeds that of dissolved ammonium, nitrate, and nitrite together (the inorganic nitrogen – DIN components). Recent evidence indicates that many organic N compounds are released into the DON pool and taken up from this pool by planktonic microbiota (microalgae and bacteria) on time scales of hours to days. This observation suggests that many components of the DON pool can play an active role in supplying N nutrition directly or indirectly to phytoplankton and bacteria and may affect the species composition of the microbial assemblage.

We propose to analyze the DON pools in aquatic environments and to study their sources and fate. Both allochthonous and autochthonous sources of DON will be fractionated and general chemical structure will be studied by various spectroscopic methods. Bio-availability of the major components of the DON pool will be investigated under laboratory conditions to evaluate their turnover time and their persistence in nature.