Klaus D Joehnk

The Commonwealth Scientific and Industrial Research Organisation | CSIRO · Land and Water

In this first worldwide synthesis of in situ and satellite-derived lake data, we find that lake summer surface water temperatures rose rapidly (global mean = 0.34°C decade−1) between 1985 and 2009. Our analyses show that surface water warming rates are dependent on combinations of climate and local characteristics, rather than just lake location, l...

Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been...

Cyanobacteria of the order Nostocales found in lakes in temperate regions are generally assumed to benefit from climate change. To predict their future development under varying environmental conditions, we developed a mathematical model that simulates their entire life cycle. Cylindrospermopsis raciborskii, a tropical species which spread to the n...

Dense surface blooms of toxic cyanobacteria in eutrophic lakes may lead to mass mortalities of fish and birds, and provide a serious health threat for cattle, pets, and humans. It has been argued that global warming may increase the incidence of harmful algal blooms. Here, we report on a lake experiment where intermittent artificial mixing failed t...

Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos...

Climate warming alters the seasonal timing of biological events. This raises concerns that species-specific responses to warming may de-synchronize co-evolved consumer-resource phenologies, resulting in trophic mismatch and altered ecosystem dynamics. Here we explore effects of warming on the temporal coherence of two key phenological events in lak...

Climate warming alters the seasonal timing of biological events. This raises concerns that species-specific responses to warming may de-synchronize co-evolved consumer-resource phenologies, resulting in trophic mismatch and altered ecosystem dynamics. Here we explore effects of warming on the temporal coherence of two key phenological events in lak...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

Empirical evidence demonstrates that lakes and reservoirs are warming across the globe. Consequently, there is an increased need to project future changes in lake thermal structure and resulting changes in lake biogeochemistry in order to plan for the likely impacts. Previous studies of the impacts of climate change on lakes have often relied on a...

Many of the world’s rivers have been found to be sources of CO2 to the atmosphere, however, there has been limited assessment in arid regions. This analysis of a long-term (1979–2013) dataset (n = 3496) along Australia’s largest river system (River Murray) showed that there were sustained high pCO2 (carbon dioxide partial pressure) levels, ranging...

Climate change and other anthropogenic stressors have led to long-term changes in the thermal structure, including surface temperatures, deepwater temperatures, and vertical thermal gradients, in many lakes around the world. Though many studies highlight warming of surface water temperatures in lakes worldwide, less is known about long-term trends...

Water quality measures for inland and coastal waters are available as discrete samples from professional and volunteer water quality monitoring programs and higher-frequency, near-continuous data from automated in situ sensors. Water quality parameters also are estimated from model outputs and remote sensing. The integration of these data, via data...

During the 2019–2020 Australian bushfire season, large expanses (~ 47%) of agricultural and forested land in the upper Murray River catchment of south‐east Australia were burnt. Storm activity and rainfall following the fires generated increased sediment loads within rivers, resulting in localised fish kills and widespread water quality deteriorati...

Lake surfaces are warming worldwide, raising concerns about lake organism responses to thermal habitat changes. Species may cope with temperature increases by shifting their seasonality or their depth to track suitable thermal habitats, but these responses may be constrained by ecological interactions, life histories or limiting resources. Here we...

A key phenological event in the annual cycle of many pelagic ecosystems is the onset of the spring algal bloom (OAB). Descriptions of the factors controlling the OAB in temperate to polar lakes have been limited to isolated studies of single systems and conceptual models. Here we present a validated modelling approach that, for the first time, enab...

Globally, lake surface water temperatures have warmed rapidly relative to air temperature, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970-2009) summertime vertical temperature profiles in lakes across the world to examine tre...

The common carp (Cyprinus carpio) is an invasive species in the rivers and waterways of southeastern Australia, and it has been implicated in the serious decline of many native fish species. Over the past 50 years, various control options have been explored, and to date, these have been ineffective or cost-prohibitive. Most recently, cyprinid herpe...

Following the 2019/20 Black Summer bushfires, rainfall can wash huge volumes of ash and debris from burnt vegetation and exposed soil into rivers. Fires can also lead to soil “hydrophobia”, where soil refuses to absorb water, which can generate more runoff at higher intensity. Ash and contaminants from the fire, including toxic metals, carbon and f...

Extensive bushfires in 2019-20 burnt large parts of forested and rural regions in south east NSW and north-eastern Victoria. These bushfires degraded water quality and altered the dynamics of river, lake and estuarian ecosystems. As loss of vegetation and parched soil surface make the fire affected area more erodible, most critical impacts occur fo...

The period of 2019-20 shall be remembered for its devastating bushfires across the east of Australia. In the Murray-Darling Basin, fires burnt about 5,000 Km2 of forested and rural regions in south east NSW and north-eastern Victoria, an important water catchment for the Murray River. Extensive bushfires in the Upper Murray catchment resulted in ex...

To understand how the Southern Spring Flow event influenced productivity along the length of the Murray River two complementary monitoring programs were carried out. In the first program, field measurements were taken each week along the Murray at 21 sites for 15 weeks to determine the concentrations and loads of carbon, nutrients and algae (measur...

In recent decades, several lake models of varying complexity have been developed and incorporated into numerical weather prediction systems and climate models. To foster enhanced forecasting ability and verification, improvement of these lake models remains essential. This especially applies to the limited simulation capabilities of biogeo-chemical...

The Conversation, 13. Jan. 2010. https://theconversation.com/the-sweet-relief-of-rain-after-bushfires-threatens-disaster-for-our-rivers-129449 When heavy rainfall eventually extinguishes the flames ravaging south-east Australia, another ecological threat will arise. Sediment, ash and debris washing into our waterways will decimate aquatic life an...

Despite the enticing discoveries of chaos in nature, triggers and drivers of this phenomenon remain a classical enigma which needs irrefutable empirical evidence. Here we analyze results of the yearlong replicated mesocosm experiment with multi-species plankton community that allowed revealing signs of chaos at different trophic levels in strictly...

Global temperature is steadily increasing and so is for freshwater demand. The world population today is 7.7 billion and is currently growing by approximately 83 million people every year causing increased demand for clean freshwater. The nexus between rapid population growth, infrastructure development, increased agricultural demands and global wa...

In recent decades, several lake models of varying complexity have been developed and incorporated in numerical weather prediction systems and climate models. To foster enhanced forecasting ability and verification, improvement of these lake models remains essential. This especially applies to the limited simulation capabilities of biogeochemical pr...

This article is freely available for 50 days at https://authors.elsevier.com/c/1YsCs4sKhEHMiM

The water regime of the Lower Lakes and Coorong, which includes the hydrology, climate, hydrodynamics and water quality, is a significant driver of the ecology in the region. Changes in water level and salinity have a strong influence on ecosystem variability and habitat conditions (e.g. Paton et al. 2009; Ye et al. 2016). At a whole-of- site level...

Under limited time and resources, ecological managers are under increasing pressure to demonstrate tangible impact of monitoring activities. Value of Information (VOI) has been advocated as an ideal tool to evaluate whether more data is required to improve expected management outcomes. Yet, despite several recent works explaining its value, VOI rem...

This chapter addresses the demand of environmental agencies and water industries for tools enabling them to prevent and mitigate events of rapid deterioration of environmental assets such as contamination of air, soils and water, declining biodiversity, desertification of landscapes. Getting access to reliable early warning signals may avoid excess...

Mathematical models are indispensable for addressing pressing aquatic ecosystem management issues, such as understanding the oceanic response to climate change, the interplay between plankton dynamics and atmospheric CO2 levels, and alternative management plans for eutrophication control. The appeal of process-based (mechanistic) models mainly stem...

Over the last decade the field of lake modeling has attracted much attention in weather and climate modelling community. Several lake models of diverse complexity have been developed and incorporated in the numerical weather forecast systems and climate models. Hence, the comparison of lake models and their verification are essentially relevant. Es...

Boom-bust dynamics – the rise of a population to outbreak levels, followed by a dramatic decline – have been associated with biological invasions and offered as a reason not to manage troublesome invaders. However, boom-bust dynamics rarely have been critically defined, analyzed, or interpreted. Here, we define boom-bust dynamics and provide specif...

Water quality in future mining lakes strongly depends on their thermal and chemical stratification. High salinity groundwater inflow accumulating in the deepest parts of the lake tend to generate a permanent stratification, a monimolimnion. Turbulence generated by wind action and convective mixing during cooling periods in autumn and winter can, on...

Water quality in inland waters is worldwide declining due to changes in land-use and climate change, recurring algal blooms by e.g. toxic cyanobacteria species are widespread. Such potential harmful algal blooms impact ecosystem services, harm aquatic ecosystem health and limit recreational and cultural water uses. Predicting and managing algal blo...

Water quality and ecosystem health of inland systems are important for the sustainable development of these important ecosystems. The UN-Water agency recognized that there are many challenges in undertaking improvements in water quality or ecosystem health and monitoring their changes over time. Quantitative use of satellite remote sensing data for...

Surface water quality in Australia is declining and recurring harmful algal blooms by toxic cyanobacteria species (Cyanohab) are widespread. Cyanohabs impact ecosystem services, harming the health of water ecosystems and limiting recreational and cultural water uses. With current approaches, predicting and managing HABs requires intensive local mon...

Water quality in future mining lakes strongly depends on their thermal and chemical stratification. High salinity groundwater inflow accumulating in the deepest parts of the lake can generate a permanent stratification, a monimolimnion [1, 2]. However, turbulence generated by wind action and convective mixing during cooling periods in autumn and wi...

The extent to which the water quality of receiving bodies is driven by sediment load inputs from catchments can be unclear due to coincident processes, such as tidal or wind resuspension of benthic sediments within a coastal water body. We examined whether historical monitoring programs contain information on the linkage between catchment and recei...

Keywords: hydrodynamic model, waves, population dynamics, sediment transport, suspended sediment, seagrass, ecology Seagrass extent, growth, and decline are mainly driven by the hydrodynamics affecting the physical environment for growth, the underwater light climate, and the availability of nutrients. Seagrass stands have a feedback effect on the...

Archival remote sensing imagery were used to reconstruct seagrass coverage and turbidity time-series for Western Port, Victoria. This enables investigation of the extent to which seagrass coverage and bay turbidity are, and have been, sensitive to river discharge and suspended solids or climatic fluctuations. Furthermore, the use of remote sensing...

Western Port in Victoria has experienced extensive loss of seagrass coverage believed to be due to large sediment inputs to the bay from its river catchments. This study is an attempt to advance understanding of the efficiency of sediment delivery from upland erosion through a channelized floodplain to seagrass beds within a semi-enclosed bay, West...

Surface water quality in Australia is declining and recurring harmful algal blooms by toxic cyanobacteria species (Cyanohab) are widespread. Cyanohabs impact ecosystem services, harming the health of water ecosystems and limiting recreational and cultural water uses. With current approaches, predicting and managing HABs requires intensive local mon...

"Integrated Lake Modelling in the Climate System" and "Lake Ice Dynamics" were two sessions at the ASLO Aquatic Sciences Meeting in Granada Feb. 2015 attracting each 12 presentations on * modelling hydrodynamic processes in lakes, * coupling with ecosystem models, * running multi-lake and multi-model approaches, and * coupling with regional climat...

The Coorong, South Australia, is a hypersaline coastal lagoon receiving freshwater inflow from the Murray River via a series of barrages separating it from the Lower Lakes. It is connected to the ocean via a tidal inlet. During the prolonged drought in the Murray–Darling Basin in Australia (2001-2010), the ecosystem in the Coorong suffered severe s...

Long term trends and variability in the seasonality of lake ice dynamics are some of the clearest indicators of changes in climate conditions. The timing of ice formation, ice cover duration and ice loss in lakes and reservoirs will modulate the impact of regional weather conditions on lake thermal structure and mixing, and thus will ultimately inf...

Increasing concentrations of atmospheric CO2 and other greenhouse gases lead to the possibility of future climatic warming, the extent of which has been projected using General Circulation Models (GCMs). The potential impact of climate change on lakes and reservoirs will be strongly influenced by changes in thermal stratification and mixing. Howeve...

The physical dynamics of lake temperature and ice phenology are important in the modelling and management of temperate aquatic ecosystems. One-dimensional hydrothermal lake models have not been well evaluated in terms of how they simulate ice dynamics in particular. We chose four models (Hostetler, Minlake, Simple Ice Model or SIM, and General Lake...

In the present study, a numerical model of the hydrodynamic and thermal structure of artificial shallow lakes in eastern India has been developed as a tool to assess the ecological water quality, driven by the meteorological forcings. It allows quantification of the vertical mixing processes that govern not only the thermal structure but also nutri...

Accounting for groundwater recharge from overbank flooding is required to reduce uncertainty and error in river-loss terms and groundwater sustainable-yield calculations. However, continental- and global-scale models of surface water–groundwater interactions rarely include an explicit process to account for overbank flood recharge (OFR). This paper...

The African great lakes are of utmost importance for the local economy (fishing), as well as being essential to the survival of the local people. During the past decades, these lakes experienced fast changes in ecosystem structure and functioning, and their future evolution is a major concern. In this study, for the first time a set of one-dimensio...

Five one-dimensional (1D) lake models were run for the open water season in 2006 for Lake Valkea-Kotinen (Finland) using on-lake measured meteorological forcing. The model results were validated using measurements of water temperature and of eddy covariance (EC) fluxes. The surface temperature is satisfactorily simulated by all models showing sligh...