Should I stay or should I go? The diurnal behaviour of plant-attached zooplankton in lakes with different water transparency

Peer reviewe

3D-modelling of the thermal circumstances of a lake under artificial aeration

A 3D-model was developed to study the effects of hypolimnetic aeration on the temperature profile of a thermally stratified Lake Vesijärvi (southern Finland). Aeration was conducted by pumping epilimnetic water through the thermocline to the hypolimnion without breaking the thermal stratification. The model used time transient equation based on Navier–Stokes equation. The model was fitted to the vertical temperature distribution and environmental parameters (wind, air temperature, and solar radiation) before the onset of aeration, and the model was used to predict the vertical temperature distribution 3 and 15 days after the onset of aeration (1 August and 22 August). The difference between the modelled and observed temperature was on average 0.6 °C. The average percentage model error was 4.0% on 1 August and 3.7% on 22 August. In the epilimnion, model accuracy depended on the difference between the observed temperature and boundary conditions. In the hypolimnion, the model residual decreased with increasing depth. On 1 August, the model predicted a homogenous temperature profile in the hypolimnion, while the observed temperature decreased moderately from the thermocline to the bottom. This was because the effect of sediment was not included in the model. On 22 August, the modelled and observed temperatures near the bottom were identical demonstrating that the heat transfer by the aerator masked the effect of sediment and that exclusion of sediment heat from the model does not cause considerable error unless very short-term effects of aeration are studied. In all, the model successfully described the effects of the aerator on the lake’s temperature profile. The results confirmed the validity of the applied computational fluid dynamic in artificial aeration; based on the simulated results, the effect of aeration can be predicted.Peer reviewe

Bridge under troubled water : turbulence and niche partitioning in fish foraging

Peer reviewe

Persistency of artificial aeration at hypertrophic Lake Tuusulanjärvi : A sociohistorical analysis

Peer reviewe

The past, present, and future of a lake : Interdisciplinary analysis of long-term lake restoration

The history and future of the restoration efforts at the hypereutrophic southern Finnish lake, Tuusulanjarvi, are investigated. The interdisciplinary study is conducted within a modified DPSIR-framework, which allows us to both trace back and envision the future of the dynamics of the complex socio-ecological processes involved in restoration. The study covers the time period from the early 1970s up to 2030. The longitudinal study integrates environmental historical, limnological, and futures studies. The analyses reveal the multiple time scales of social and ecological processes present in long term restoration, the changing perceptions of and emphasis on restoration goals and outcomes over time, and the challenges that incidental and uncertain parameters, such as weather conditions, pose to sustainable and efficient restoration endeavors.Peer reviewe

Hypolimnetic aeration intensifies phosphorus recycling and increases organic material sedimentation in a stratifying lake: Effects through increased temperature and turbulence

Peer reviewe

Zooplankton rhapsody: Unexpected response in community following increased fish predation

The impact of increased fish density on the crustacean zooplankton was studied in a small, forest lake. Interestingly and contrary to our hypothesis, increased fish density resulted in an increase in biomass of large-sized cladocerans, but a decrease in biomass of smaller and dominant cladoceran species. Thus, the effect of increased planktivory of fish was likely tempered by compensatory dynamics of zooplankton, wherein abundance of some species increased to compensate for population decreases by other species. This change in the relative species composition of zooplankton was seen as the increased diversity in crustacean zooplankton community. We conclude that instead of simple “top-down” or “bottom-up” regulation of zooplankton, the diverse array of connections among species is more likely to cause community dynamic fluctuations in zooplankton. Moreover, behavioural changes e.g. habitat change of fish may also have a pronounced effect on the response of zooplankton community on fishing.Peer reviewe

Preface to the Special Issue “Ecologically sustainable fishing” : Project KESKALA background, objectives and conclusions

Non peer reviewe