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Food web studies rely heavily on the use of traditional gut content analysis or the fairly popular stable isotope analysis rather than fatty acid analysis (FAA) despite its straightforward process, and ability to identify and characterize more diverse trophic pathways. In this study, we employed fatty acid (FA) biomarkers as a preliminary attempt to trace and characterize trophic pathways in food webs of four tropical lakes of volcanic origin in Luzon Island, Philippines - three clustered maar lakes (Yambo, Pandin and Calibato) and a large caldera lake (Taal). These lakes have a long history of human disturbance but limited ecological data. Knowledge of basal food sources and existing trophic dynamics of organisms are generally non-existent. Particulate organic matter (POM), zooplankton, and fish species were collected in August 2019 from the study lakes as representative of three trophic guilds. Non-metric multidimensional scaling (NMDS) and principal component analysis (PCA) were conducted to analyse FA profiles and characterize trophic relationships between representative organisms. For the POM, within lakes comparison of taxon-specific FA profiles showed a significant difference between the surface and near bottom depths, with the former dominated by photoautorophs and the latter by chemotrophs, suggesting the ability of FAA to effectively delineate between micro-organisms. Between lakes comparison also showed significant difference between the caldera and maar lakes, with the latter containing higher composition of bacterial FA, reminiscent of the considerably smaller lakes' response to the impact of unmitigated organic loadings from anthropogenic activities. Taken together with the primary consumers' FA profiles, analysis confirmed the ability of FAA to discriminate between FA profile sources. PCA explained >70% of the variance in the FA compositions for three trophic guilds in the two deepest lakes, which delineated both zooplankton and fish species food selectivity in each lake, alluding to FAA's capacity to characterize dietary reliance of various species in an environment with numerous food sources. Although certain limitations were encountered, such as the specificity of the sampling depths for POM, and the small sample size of the representative species of the third trophic level, this study demonstrated the effectiveness of FAA as a powerful ecological tool for disentangling intricate lake food webs comprising various food sources. Overall, this study provided baseline information on basal food sources and trophic pathways of representative organisms from four tropical lakes. Taken together, FAA studies have wide application in understanding food webs, including anthropogenically-threatened lake ecosystems. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

The article discusses findings of a study on the composition and quantity of zooplankton found in freshwater sardine that were caught in Taal Lake, Philippines. The research revealed that 90 percent of the stomach contents of freshwater sardine consisted of large adult copepods and 10 percent cladocerans and rotifers. An analysis of collected samples from July 2003 to July 2004 to determine the zooplankton diet of Sardinella tawilis determined that freshwater sardine prefers to consume larger prey since they are more visible. Researchers noted that smaller-bodied organisms dominated the zooplankton community because of size-selective predation.

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]