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Abstract:Science should serve to improve people's lives through knowledge acquisition, education, and policy implementation. However, if rooted in exclusive and extractive practices, it can inadvertently elicit mistrust in various sectors in our society. Critical examination of historical foundations and current events in the Philippines, as demonstrated in the articles in this special issue, helps identify problems that perpetuate—as well as solutions that break down—the divide between science and society. Valuing and incorporating perspectives from the public ensures that the nature and pace of progress in the Philippines are constantly well aligned with its people and their interests.

ABSTRACTThe 7 maar lakes of San Pablo are a cluster of small volcanic lakes on Luzon Island, Philippines. These lakes, which are heavily utilized for aquaculture and ecotourism, usually experience fish kills that coincide with the northeast monsoon (NEM). This study explores limnophysical processes, particularly mixing regimes, in the lakes in relation to prevailing monsoons. We monitored monthly vertical and seasonal profiles of water temperature, salinity, conductivity, and dissolved oxygen from October 2016 to December 2018. Three types of mixing regimes were observed among the lakes, which have similar surface areas but different depths: polymixis in the shallowest; warm monomixis in lakes with intermediate depth; and meromixis in the deepest. A boundary between monomixis and meromixis was identified between 36 and 62 m depth. Monthly monitoring showed seasonal mixing occurred exclusively during the NEM (Nov–Apr). We also incorporated meteorological data into the model and performed multiple regression analysis for each lake to determine the best predictor: lake stability, as indicated by the Schmidt stability (ST). A between-lake comparison showed lake stability was strongly correlated with both air temperature and wind speed, suggesting these 2 meteorological variables are involved in establishing thermal stratification in the lakes during the southwest monsoon. This study provides insights for adaptive lake management and projections of climate impacts on these understudied tropical lake ecosystems in Southeast Asia.

AbstractIn the Philippines, the ecology of microcrustaceans from groundwaters and their dependent ecosystems remain poorly understood, yet knowledge about this group can elucidate patterns in groundwater biodiversity to develop sound conservation policies. In this study, microcrustaceans were studied by collecting samples from 102 groundwater-dependent ecosystems, including 51 artesian wells, 23 caves, 14 springs, and 14 piped groundwater pumps during the dry (Nov 2014 to Apr 2015) and wet (May–Oct 2015) seasons. Results indicate the presence of 21 species from Cladocera and Copepoda, including 2 obligate stygobionts and 19 species consist with surface water and facultative stygobiotic taxa. Significant differences in microcrustacean assemblages were noted among types of groundwater-dependent ecosystems (P < 0.05), wherein wells and caves harbored more abundant assemblages with higher total species richness; however, no significant variations were observed between seasons (P > 0.05). Furthermore, principle component analysis revealed that sampling sites were highly characterized by altitude, specific conductivity, and total water hardness. Microcrustacean assemblages in sampled sites were highly dominated by the influence of temperature, dissolved oxygen, and altitude. Species rarefaction analysis revealed low species richness in sampled sites within the region, supporting the existing notion that temperate groundwater-dependent ecosystems were more diverse, and faunal composition in terms of ecological groups is extremely different in tropical and temperate settings.

We conducted a preliminary analysis on the effects of various physical and chemical parameters on the morphometry and reproductive capacity of the calanoid copepod Filipinodiaptomus insulanus(Wright, 1928), endemic to the Philippines, by proxying clutch size (CS). Specimens and water quality readings were obtained between October 2019 and February 2020 from four sites in northern Philippines. Only the sizes of adult males and non-ovigerous adult females showed significant differences (P< 0.05) among populations. Non-eutrophic, temporary shallow waters were the predominant habitat type of F. insulanus, corroborating earlier observations that it is mainly found in relatively pristine environments. Correlation analysis showed a significant indirect relationship (P< 0.001) between the size of individuals and temperature, a potential adaptive response to its environment. Such observations may be valuable in preventing the disappearance of this species from parts of its previously known range.

To understand methane (CH4) dynamics in tropical lakes and describe their importance in overall CH4emissions, we observed temporal trends of CH4stored in the water columns of Philippine lakes of different depths (shallow, moderately deep, and deep). We detected higher CH4stored in profundal anoxic layers of deeper lakes. The average surface and profundal CH4concentrations throughout our monthly monitoring were 0.27 ± 0.07 and 421 ± 189 μmol L–1in the shallow lake, 0.48 ± 0.37 and 1,121 ± 125 μmol L–1in the moderately deep lake, and 0.34 ± 0.23 and 943 ± 119 μmol L–1in the deep lake. The fate of CH4stored in the water column was related to depth, owing to different stratification and mixing regimes. Analyses of temporal relationships of CH4with daily weather and physicochemical parameters revealed their impact on CH4dynamics by controlling the frequency and mixing intensity throughout the year. Only shallow lake exhibited increase in CH4concentrations with lowering atmospheric pressure. This allows vertical mixing and transport of CH4from deeper to shallower layers. In moderately deep, and deep lakes, effects of daily weather parameters were not apparent on CH4concentrations in the deepest layers (below 30 m depth). This suggests that lake depth and stratification should be considered for precise estimation of tropical lakes' CH4emissions. Comparison with lakes under different climate conditions revealed the importance of tropical lakes for surface CH4emission due to higher surface CH4concentrations. Changes in water temperature is one of the factors controlling profundal CH4production, storage, and its transport to shallower layer. Vertical CH4storage distribution in studied lakes are linked to episodic events, such as monsoons and extreme weather, driving turnoverWeather variables such as air temperature and atmospheric pressure are external drivers of stored methane in tropical lakesTropical lakes, with higher profundal water temperature, show more potential for storing and emitting CH4than lakes from other regions Vertical CH4storage distribution in studied lakes are linked to episodic events, such as monsoons and extreme weather, driving turnover Weather variables such as air temperature and atmospheric pressure are external drivers of stored methane in tropical lakes Tropical lakes, with higher profundal water temperature, show more potential for storing and emitting CH4than lakes from other regions