Regime shifts in ecology are characterised by major, often abrupt changes in ecosystem structure and functioning in response to one or more driving variables, or pressures. Changes in the provision of ecosystem services are a potential outcome. Despite the current combination of rapidly increasing pressures on what are often highly important socio‐ecological systems, the resilience of lakes in the warm tropics to human perturbation is far less well understood than those at higher latitudes. This paper focuses on evidence of aquatic ecosystem change from a cluster of three deep, freshwater, volcanic crater lakes (Yambo, Mohicap, and Sampaloc) at low altitude on the island of Luzon, Philippines. The lakes support different intensities of aquaculture, an important livelihood but also a driver of poor water quality throughout tropical Asia. Measured and monitored climate and water quality data, in addition to sedimentary evidence from sediment cores collected from the three study lakes, were used to determine the magnitude and trajectory of changes in lake water quality. Sediment cores were radiometrically dated and analysed for organic matter, spheroidal carbonaceous particles, and diatom remains. Diatom data were zoned numerically using cluster analysis. Diatom remains were also used to infer past variations in pH and possible relationships between potential driving climatic variables (temperature and rainfall). Diatom data sets were explored using detrended component analysis and principle component analysis. Despite differences in intensity of aquaculture, a common trajectory and timing of a potential regime shift, characterised by a replacement of benthic with planktonic diatoms and an increase in diatom accumulation rates from the early to mid‐1980s, is evident, and attests a low threshold for disturbance effects. A predominantly planktonic diatom flora has persisted even after recent improvements in environmental quality. The potential new regime may be less resilient and more susceptible to harmful algal blooms, abrupt expansions of anoxic conditions, and periodic mass fish kills when compared with its former state. The research further highlights the sensitivity of freshwater ecosystems in the warm tropics to disturbance pressures, and the risks to livelihoods, ecosystem services, and sustainable development.

Laguna de Bay is a large, shallow lake located near Manila, Philippines. The lake is drained by the Pasig River, which flows to Manila Bay. It periodically reverses direction, bringing saline water into this predominately freshwater body. The lake has historically been of great importance to locals who depend on it for fish and related livelihoods. Recently, it also has been considered a source of potable water for the Manila region. The intense land use in the watershed has caused enhanced siltation, and the lake has also been plagued by overfishing, intense aquaculture and water pollution from industrial and domestic sources. This paper over views these issues and examines the role of the Laguna Lake Development Authority in developing and conser ving the lake basin's resources. Two programmes related to fisheries development and an environmental user-fee programme to control water pollution are critiqued. Lessons learned from the nearly 40 years of experience managing this tropical lake also are presented. Key wordsaquaculture, environmental user fee, fish pen, institutional reform, Laguna de Bay, lake basin management, market-based instruments.

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Floating solar farm has been demonstrated as technically and commercially viable in man-made lakes, ponds and in coal-mining subsidence areas. Studies on its environmental impacts are limited and some are still being conducted globally. The use of natural lakes for this kind of renewable energy generation is being explored for the first time in the Philippines, particularly in Laguna de Bay. It is considered as a potential development project, but there were concerns on the environmental and social impacts on a multiple-use lake. As an initial step to deal with uncertainties, the Laguna Lake Development Authority allowed the operation of floating solar farms on a pilot scale for one year subject to certain requirements including the monitoring of essential water quality parameters in the pilot sites to determine the impacts. The data together with the inputs from the operators of the pilot projects were used in the assessment of the environmental, technical and commercial viability of floating solar farm and was used by the Laguna Lake Development Authority in formulating a policy on this emerging use of the lake and in crafting the implementing rules and regulations.

Understanding how lakes respond to changes in nutrient loading along a productivity gradient can help identify key drivers of aquatic change, thereby allowing appropriate mitigation strategies to be developed. Physical, chemical and biological water column measurements combined with long-term water monitoring data for six closely located crater lakes, in Southeast Asia, were compared to assess the response of lakes along a productivity gradient equating to a transect of increasing aquaculture intensity. Increasing chlorophyll a (phytoplankton biomass) in the upper waters appeared to modify the thermocline depth and light availability causing a shift from a deep chlorophyll maximum at low aquaculture intensity to the emergence of algal dead zones lower in the water column with high aquaculture intensity. High phosphorus loading and light limitation from enhanced algal biomass, associated with high aquaculture intensity, exacerbated nitrogen drawdown, leading to the prevalence of potentially nitrogen-fixing cyanobacteria. Seasonal overturn during the cooler season resulted in low dissolved oxygen concentrations in the epilimnion, potential harmful algal blooms, a reduction in the habitable depth for fish and ultimately increased mortality amongst farmed fish.