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Relatively limited information exists on Lake Wood's limnology and ecology, an ancestral lake of the Subanens. Here, we provide a limnological characterization of the lake -- exploring its physical, chemical, and biological features. The data on lake morphometry were gathered using an echosounder; lower depth water samples were collected using a Niskin water sampler for physicochemical analyses while surface water samples were collected at five sampling sites for phosphate (PO4) analysis; and zooplankton samples were collected at several depths through vertical towing in March-April 2019. Lake Wood, located at 320 m above sea level, has an extensive surface area covering 7.38 km² with a maximum depth of 85 m. Lake water comes from rainfall, small rivers, and groundwater and empties into the Dumanquilas Bay via its only outlet -- the Biswangan River. Land use of the lake is predominantly cultivated land. Moreover, based on the trophic state index (TSI), the lake's current trophic status is eutrophic. During the study periods, thermocline and oxycline formed at 15 m below the surface of the lake. We recorded three cladocerans (Ceriodaphnia cornuta, Diaphanosoma cf. sarsi, and Moina micrura) and one copepod species (Thermocyclops crassus) in the lake, all of which are common limnetic species found in the Philippines. Based on our findings, we recommend more efforts to manage and rehabilitate the lake to control and manage eutrophication's negative impacts. Finally, our study contributes to understanding lakes in Mindanao that are less represented in Philippine freshwater research. [ABSTRACT FROM AUTHOR]

Zooplankton are key ecosystem components in the pelagic food web. These organisms move vertically to avoid visual predators (i.e. fish) that prey on them; such movement is known as diel vertical migration (DVM). This study aims to elucidate the dynamics of the daily vertical migration of zooplankton and to determine the factors that govern their migration behavior in an understudied Philippine Lake in Lake Wood (Mindanao Island) from March to April 2019. Zooplankton and several environmental parameters were sampled in the deepest part of the lake at specific depths (1 m, 15 m, 30 m, 50 m, and 70 m) during noon and midnight. Adult females of Thermocyclops crassus displayed typical diel vertical migration patterns accompanied by large migration amplitudes. The food-rich epilimnion supports the abundance of T. crassus during the night and rather dwells in the hypolimnion during the day to evade visual predators. The study underscores the intricate interplay among predation pressure, temperature, water transparency, and total dissolved solids, collectively shaping the observed vertical migration behavior of adult female T. crassus. These perspectives provide a deeper understanding of how these organisms navigate the intricate challenges posed by their environment, offering insights into their strategies for survival and thriving within the ecosystem. [ABSTRACT FROM AUTHOR]

Limnetic zooplankton serve as a major food source for pelagic fi sh. This paper updates the species composition, diversity and community dynamics of limnetic zooplankton in the two basins of Lake Taal, an active caldera lake ecosystem. Samples obtained from January to December 2008 included 15 rotifer, six cladoceran and three copepod species. Eight species are new records for the lake. The zooplankton community is dominated by copepods, which contributed 64% to total abundance and 84% to total biomass. Diversity values for rotifers and cladocerans were low and similar in both lake basins. The composition, diversity and homogenous spatial distribution of zooplankton in Lake Taal is typical for tropical lakes with a high trophic state which may be a response to the prevailing conditions infl uenced by its location, geological origin and meteorological factors. [ABSTRACT FROM AUTHOR]

Lake Taal is one of the most significant lake ecosystems in tropical East Asia. In 2011, a review paper consolidated all known biodiversity and limno-ecological studies conducted in Lake Taal from the beginning of the 20th century all the way to the late 2000s. It highlighted that insufficient funding, inadequate long-term monitoring data, and the publication culture of that time impeded having a comprehensive understanding of the lake. Since then, much research work has been done in Lake Taal, especially during the past decade. This review paper provides an analysis and summary of the research work conducted in Lake Taal over the past 10 years. The recent decade has seen a steady increase in scientific interest in Lake Taal made evident by more scientists and institutions working on topics involving the lake. Research grants, collaborations, and publications have also significantly increased during the past 10 years. This has led to an improved understanding of the lake's biodiversity, ecology, and impacts of intensive aquaculture and the introduction of non-native species. Taken together, this paper presents a better understanding of Lake Taal, which can be utilized for the design and improvement of conservation, preservation, and management programs for this multi-use freshwater system. [ABSTRACT FROM AUTHOR]

A floristic study of the diatoms (Bacillariophyceae) along the Marikina River in the eastern part of Metro Manila, Philippines, recorded at least 140 species belonging to 39 genera. Of these genera, one of the greatest number of species was observed in the genus Gomphonema (18 species). These species were identified and described under the bright field light microscope. Some species were further observed under the scanning electron microscope. A habitat description of the occurrence of the Gomphonema species is given. Twelve (12) out of the 18 species are new records for the country: G. brasiliense subsp. pacificum Moser, Lange-Bertalot & Metzeltin, G. chinense Liu & Kociolek, G. contraturris Lange-Bertalot & E.Reichardt, G. cuneolus E.Reichardt, G. exilissimum (Grunow) Lange-Bertalot & E.Reichardt, G. insigniforme E.Reichardt & Lange-Bertalot, G. javanicum Hustedt, G. kobayasii Kociolek & J.C.Kingston, G. pseudosphaerophorum H. Kobayasi, G. sundaense E.Reichardt, G. cf. qingyiensis L-X Zhang, P. Yu & Q-M You, and G. vibrio var. bohemicum (Reichelt & Fricke) R. Ross. Hence, this paper reports a total of 44 species of Gomphonema from the Philippines, including previous studies from 1937 to date. [ABSTRACT FROM AUTHOR]

• Individual-based model to study the production of an invasive copepod. • Model integrates the effect of food concentration on several individual endpoints. • Calibration of the model benefits from measures obtained in vivo. • Quantify the combined impact of food and predation on egg and offspring production. Arctodiaptomus dorsalis is an invasive calanoid copepod originally from America and has recently established a population in Lake Taal in the Philippines. It has been proposed that eutrophication due to aquaculture contributes to the establishment and success of this species. This study aimed to clarify this hypothesis by quantifying the effect of increasing food concentration on the reproduction of A. dorsalis using an Individual-Based Model. We parameterized food concentration-dependent equations to simulate the effect of different food concentration on the reproductive traits (latency time, embryonic development time, clutch size, and hatching success) of this species using data from the literature and simulated the reproduction of 1000 independent females for 20 days at different food concentration, taking into account the variability among individuals. The simulation results showed that the cumulative production of eggs and offspring increased continuously with time when the food concentration was above 3.2 × 104 cells mL−1, suggesting that this value was the threshold concentration required for stable reproduction of A. dorsalis. This value is not particularly low compared to other copepods. Hence, our result revealed that the food use efficiency of A. dorsalis is not particularly outstanding and urge the need of a comparison with native species to confirm a possible superiority. We suggest that A. dorsalis has filled the ecological niche left vacant by the disappearance of the original species due to the deterioration of water quality caused by the eutrophication of the lake. The reproductive cycle model developed in this study constitutes a necessary step in the development of a complete population dynamics model, which can help clarify the invasive abilities of A. dorsalis. [Display omitted] [ABSTRACT FROM AUTHOR]

Sponge-microbe symbiosis is considered among the most primitive ecological relationships between metazoans and microorganisms. There is strong interest in understanding the occurrence of microbial communities in sponges due to their integral roles in host ecology, nutrient cycling, and production of potential bioactive secondary metabolites. However, most studies on sponges have been centered on marine species. In this study, the freshwater sponge Spongilla alba and its associated microorganisms were explored for the first time. Sponge samples collected from Lake Taal were taxonomically identified using gross morphology and spicules analysis. Both bacterial and fungal isolates were culturally characterized and molecularly identified using 16S rRNA gene for bacteria and ITS for fungi. Five bacterial species were identified as Pseudomonas sp., Enterococcus sp., Stenotrophomonas sp., Stenotrophomonas maltophilia, and Pseudomonas mosselii plus eight fungal species with spore sizes from 5-10 μm were identified as Colletotrichum truncatum, Trichosporon asahii, Rhizopus microsporus, Puccinia striiformis f. sp. tritici strain, Talaromyces columbinus, Phoma sp., Phomopsis sp., and Lichtheimia ramosa. Phylogenetic analysis revealed microbial sequences belonging to Proteobacteria (n = 4), Firmicutes (n = 1), Ascomycota (n = 4), Zygomycota (n = 2), and Basidiomycota (n = 2). The study reports infrequent occurrences of Enterococcus, Stenotrophomonas, Puccinia, and Lichtheimia species as freshwater sponge-associated microbes. This also presents the culturable microbial composition of freshwater sponges and rare occurrence of marine- and terrestrial-associated fungi T. asahii, R. microsporus, Phoma sp., Phomopsis sp., C. truncatum, and T. columbinus in a unique freshwater ecosystem such as Lake Taal. [ABSTRACT FROM AUTHOR]

The center-periphery hypothesis (CPH) predicts that peripheral populations will have lower genetic variation than those at the center of a species' distribution. However, ecological margins do not always coincide with geographical edges when topographies are diverse. Historical climate changes can also strongly affect genetic variation. Here, we examined genetic variation in Phyllodiaptomus tunguidus , a calanoid copepod endemic to the north-eastern Oriental. This species was predicted to exhibit a complex pattern of genetic variation across its range due to the diverse topographies and stable climate history of the north-eastern Oriental. To test this, we used geographic distance to the center of the distribution, current ecological suitability, and climate during the last glacial maximum as geographical, ecological, and historical factors, respectively, in our analyses. We measured genetic diversity and population differentiation using mitochondrial and nuclear markers. This showed that P. tunguidus had 3 refugia during the last glacial maximum (LGM). Such a pattern of multiple refugia complicates the determination of the center and periphery of spatial genetic diversity. Both regression models and redundancy analyses failed to support the CPH. Instead, they showed that geographical, ecological, and historical factors together shaped population genetic structure in this species. Ecological factors explained significantly more genetic variation than did geographical and historical factors—however, all three factors interacted significantly to affect the pattern of genetic variation. The results extend our understanding of the CPH and the extent to which it can explain genetic variation across populations. [ABSTRACT FROM AUTHOR]

Our knowledge of the freshwater cyclopid copepods of the Visayas Islands remains poor as compared to other terrestrial and aquatic fauna. This study focuses on two genera, Mesocyclops and Thermocyclops, which are common components of lake plankton communities. This study included specimens collected from 59 sampling sites found in major islands (Panay, Negros, Cebu, Bohol, Leyte and Samar) and a small island (Pacijan) in the Visayas region. Four species of Mesocyclops and three species of Thermocyclops were identified. This includes the first record of Mesocyclops woutersi in the Philippines, which was so far unknown from insular SE Asia. The endemic Mesocyclops microlasius, previously reported from Luzon Island, was also found in Lake Danao (Pacijan Island). An identification key to Philippine species of Mesocyclops and Thermocyclops is herein provided. Geographic distribution and possible causes of the low number of species observed and their implications for further faunal studies are also discussed. [ABSTRACT FROM AUTHOR]

The presence of the invasive calanoid copepod Arctodiaptomus dorsalis in Philippine inland waters has been reported in numerous studies. Attempts to understand how it effectively proliferated in the country's freshwaters have shown its preference towards shallow and productive waters - a feature shared by most lakes in the Philippines. In this study, we compared the body size and reproductive capacity - proxied by clutch size (CS) - of ovigerous female A. dorsalis obtained from established populations in the seven maar lakes (SML) of San Pablo, Laguna, Philippines. These measurements were also correlated with selected water quality parameters. Collection of ovigerous A. dorsalis and water quality parameters were conducted on a 3-mo sampling period during the southwest monsoon season in 2016. Statistical analysis shows that there exists a significant difference between the prosome length (PL) and CS of A. dorsalis from the seven lakes (p < 0.001), with the shallowest and most productive lake containing the most fecund population. Additionally, all water quality parameters showed a positive correlation with the PL and CS of ovigerous A. dorsalis from the SML (p < 0.01). This shows that the SML provides favorable conditions for the propagation of A. dorsalis, making it a model for in situ investigation of this invasive species' ecology; the first step in incorporating zooplankton ecology as a tool for the development of lake management systems. [ABSTRACT FROM AUTHOR]

Reservoirs are continuous waterscapes that exhibit hydrodynamic characteristics of both lakes and rivers with water flow. These dynamic habitats provide a novel chance to explore the effects of metacommunity dynamics on community structure in relation to environmental, spatial, and temporal processes. We investigated the spatial distribution of spring zooplankton communities in a large reservoir in southern China. We intensively sampled along a longitudinal gradient during early and full spring. We compared the relationship of environmental and spatial variables to the community structure of three zooplankton groups: rotifers, cladocerans, and copepods. The overall composition and abundance of zooplankton groups across longitudinal zones became more heterogeneous with increasing environmental heterogeneity across sampling periods. Multi-level ANOVA and PERMANOVA results showed that rather than homogenize the environment, water flow in late spring increased spatial heterogeneity in the environment and increased the importance of species sorting in shaping the zooplankton community. However, variation partitioning analysis showed that the influence of environmental and spatial variables also varied across the three zooplankton groups likely due to their differences in both physiological and morphological adaptation. Our study shows that metacommunity processes are important in structuring zooplankton communities in reservoir waterscapes that are influenced by flow. [ABSTRACT FROM AUTHOR]

Body size is a functional trait that influences the overall biology and ecology of an organism. Studying the shape of size–frequency distributions and size variability within different scales, approximates the influence of large-scale ecological and evolutionary processes on a species. In this study we examine the patterns of distribution and variability of body size among freshwater Cladocera across different taxonomic levels, geographic distribution and habitat association. Using extensive literature data, we show the global distribution of body size in freshwater Cladocera. Hierarchical models were used to assess the effect of different categorical variables on size variability. Our results show that almost all size–frequency distributions were skewed right in all categories. The hierarchical model showed that taxonomic affiliation contributes the most to size variability in our dataset, suggesting that size might be a conserved trait. Large genera (≥1mm) have larger estimated variability compared to smaller genera. In general, our observations on size–frequency distributions and size variability show a brief insight in the varying advantages of adaptive body size in this group of organisms in both biology (physiology) and ecology (competition and co-existence). Thus, body size is a trait important to the survival and continuing evolution of Cladocera. [ABSTRACT FROM AUTHOR]

In developing countries such as the Philippines, the inadequacy of even the most basic limnological datasets available has hindered planning and implementation of science-based management policies for inland waters. This situation is aggravated by overutilization of natural resources for ecosystem services such as water usage, aquaculture, fishing, and tourism. We reviewed published researches related to the Seven Maar Lakes (SMLs) in Luzon Is., Philippines to summarize information invaluable for the protection and sustainable use of these resources. Popular scientific search engines were utilized to gather peer-reviewed research articles and reports from both private institutions and government agencies. Literature and timeline from the 1930s to 2019 was classified into topics – namely socioeconomics, fisheries, biodiversity, and environment. Based on the literature survey, a variety of challenges, knowledge gaps, and promising research directions were identified, which are essential to the sustainable ecosystem management of the SMLs. Aquaculture practices impacting the lakes and its underestimated biodiversity were described. Measured vertical profiles of dissolved oxygen (DO), temperature, conductivity, pH, and salinity was supplemented by our preliminary limnological survey in the SMLs. Past and present monitoring data of selected physicochemical parameters were assessed from which the changing limnological status of the lakes was determined. We recommended measures motivated by strategic environmental assessments while still considering maintained economic yields. A sustained collaborative effort from different sectors is strongly suggested not only to manage the SMLs but also to address trade-offs among critical ecosystem services. Aside from the need for well-designed, long-term water quality monitoring, we also stress the synergistic interpretation of all available knowledge, which can contribute to the resolution of environmental issues at both local and global scales. [ABSTRACT FROM AUTHOR]

Unsustainable urbanization in the Indo-Pacific continues to threaten terrestrial and aquatic ecosystems due to habitat disturbances driven by human pressures. The Marikina Watershed, one of the most critical watersheds in the Philippines, has been exposed to economic and population growth resulting in landscape modification and water quality degradation. This led to establishment of the Upper Marikina River Basin Protected Landscape (UMRBPL) to rehabilitate the watershed ecosystem. To strengthen this conservation initiative, we aimed to assess whether the establishment of UMRBPL has been effective in conservation of benthic macroinvertebrate diversity in streams of the Marikina Watershed. Sixteen streams, eight from UMRBPL and eight from adjoining unprotected areas, were monitored for benthic macroinvertebrate assemblages and their habitat environments, such as pH, water temperature, dissolved oxygen, total dissolved solids, conductivity, salinity, and canopy openness. Principal component analysis and non-metric multidimensional scaling based on the environmental variables and biological metrics, respectively, revealed that habitat quality and benthic macroinvertebrate assemblages significantly differed between the protected and unprotected streams, with the former having better environment and higher biodiversity. More precisely, protected streams have significantly higher dissolved oxygen and lower canopy openness and material loadings as compared to unprotected streams. Consequently, taxon richness was four-fold higher in protected streams while stream quality indices based on abundance of key invertebrate groups (EPT and EPTC) were ten-fold higher in protected streams, as compared to unprotected streams. This study demonstrates that freshwater protected areas play crucial roles in the conservation of stream ecosystems and biodiversity under rapid urbanization in developing countries, like the Philippines. [ABSTRACT FROM AUTHOR]

Despite the increasing interest in studying Cladocera and Copepoda in Philippine freshwaters, there is a need to update our knowledge on its taxonomy and distribution in highly urbanized areas, such as Metropolitan Manila. This paper presents an updated listing of freshwater microcrustaceans and their distribution in Metropolitan Manila, considering the continued deterioration of water quality and increased urbanization in many areas since the last comprehensive study on these taxa in 1950s. We collected water samples from 33 freshwater sites in Metropolitan Manila and 23 of which were found to contain microcrustacean zooplankton. A total of 13 species were identified including two new locality records for C. cornuta and D. dubium in Pasig River. All 8 cladocerans, we identified have already recorded in previous studies while 3 cyclopoid copepods are new records for Metropolitan Manila. Furthermore, 16% of all known freshwater microcrustacean zooplankton species in the Philippines are found in Metropolitan Manila, including the Luzon-endemic Filipinodiaptomus insulanus collected from man-made reservoirs in less-disturbed habitats (an urban wildlife park, golf course and eco-park). Other identified species such as Thermocyclops taihokuensis may serve as indicator for high levels of nutrient. These results point to the importance of monitoring urban aquatic biodiversity for their potential in determining aquatic ecosystem health and of maintaining urban aquatic sanctuaries which may serve as alternative habitat for flora and fauna in rapidly developing urban centers such as Metropolitan Manila. [ABSTRACT FROM AUTHOR]

Intensive aquaculture in natural lakes has been shown to have negative effects on biodiversity. We conducted a study on the diversity and distribution of macro-gastropods (>1 cm) in three major lakes used for aquaculture on Luzon, the largest island in the Philippines archipelago, to provide baseline information on freshwater gastropods. Collections were made in 27 sampling sites in all three lakes. The samples were identified by examining the shell and radula. The gastropod collection comprised 13 species in six families, including 12 new records in Laguna de Bay and seven new records for Lake Taal. All species found in Lake Sampaloc are considered new records due to the lack of published literature on its gastropod fauna. There is low gastropod diversity in all three lakes. Distribution within the lakes is related to the presence of suitable habitats for each species rather than the size and geological origin of the lakes. The proximity of all three lakes may have facilitated gastropod dispersal between them, as all have similar environmental conditions brought about by intensive aquaculture activities. [ABSTRACT FROM AUTHOR]

Arctodiaptomus dorsalis is an invasive calanoid copepod from America, and is now found in 23 out of 32 lakes and rivers in the Philippines. Live specimens of A. dorsalis were collected from Lake Taal and cultured in the laboratory. The specimens were reared under three different temperatures (25°C, 30°C, and 35°C) with the same food and light conditions, i.e. ~105 cells mL-1 of Chlamydomonas reinhardtii and 12L:12D at ~60 lx, respectively. Post-embryonic development times from hatching to adult decreased from 31.5 d to 18.3 d as the temperature increased, while those during naupliar stages were quite similar, i.e. 4.4, 2.8 and 2.3 d at 25, 30 and 35°C, respectively. The naupliar durations were substantially shorter than the copepodid stages. Clutch sizes were almost the same, 8.7-9.2 eggs clutch-1, among all temperatures tested, while hatching success decreased from 85.9% at 25°C to 24.2% at 35°C. Overall survival rates from hatching to adult decreased as well from 67% at 25°C to 23% at 35°C. This is the first successful attempt to culture A. dorsalis collected from a freshwater lake in the Philippines. [ABSTRACT FROM AUTHOR]

Macrophytes play an important role in the aquatic ecosystem since they are good bioindicators and serve as habitat for littoral fishes. This research involves the use of the hydroacoustic method aided by visual observation and quantification in determining the distribution and abundance of submerged macrophytes in the littoral zones of Lake Taal. The results were used to generate spatial distribution and percent cover maps of macrophytes in the lake. Based on the surveys, five macrophyte species were present in Lake Taal. Denser macrophyte beds were concentrated in the south basin of the lake. High nutrient levels in the south basin contributed to heavy macrophyte growth in this area, which usually come from run-offs from the residential, commercial and agricultural watersheds. The lesser biomass of macrophytes in the north basin was attributed to clearing activities due to the construction of fish cages for aquaculture. Furthermore, we were able to observe that there were different dominant species in the north and south basins of the lake; Najas indica was more prominent in the north basin, while Vallisneria nanawas more common in the south. This study shows that anthropogenic sources of excess nutrients and other activities such as aquaculture play a role in altering the distribution of macrophytes in Lake Taal and how these can have potential detrimental impacts to the littoral zones of the lake. [ABSTRACT FROM AUTHOR]

Body size and environmental prey availability are both key factors determining feeding habits of gape-limited fish predators. However, our understanding of their interactive or relative effects is still limited. In this study, we performed quantitative dietary analysis of different body sizes of goby (Gymnogobius isaza) specimens collected from Lake Biwa between 1962 and 2004. First, we report that the diet was composed mainly of zooplankton (cladocerans and copepods) before the 1980s, and thereafter, shifted to zoobenthos (gammarids). This foraging shift coincided with, and thus can be linked to, known historical events in the lake at that time: decrease in zooplankton abundance with the alleviation of eutrophication, increase in fish body size resulting from fish population collapse, and increase in gammarid abundance due to reduced fish predation pressure. Supporting this view, our data analyses revealed how the long-term changes in the diet composition would be co-mediated by changes in fish body size and environmental prey availability. Specifically, while zoobenthos abundance strongly affected the fish diet composition, larger (smaller) fish preferred zoobenthos (zooplankton). Furthermore, the body size effects were stronger than those of prey availability. These results provide the best long-term evidence that fish feeding habits vary over decades with its body size and prey community due to anthropogenic disturbances. [ABSTRACT FROM AUTHOR]