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Fig. 1 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 1. Map of Lake Taal with the six sampling sites (NB – North Basin, SB – South Basin). The insert shows the location of Lake Taal and the other lakes mentioned in the text (P – Lake Paoay, Lb – Lake Laguna de Bay, N – Lake Naujan and Ln – Lake Lanao).

Fig. 4 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 4. Monthly variations in Shannon-Wiener Diversity (H') Index values of rotifers and cladocerans in the north and south basins of Lake Taal.

Fig. 3 in The Composition, Diversity And Community Dynamics Of Limnetic Zooplankton In A Tropical Caldera Lake (Lake Taal, Philippines)

Fig. 3. Mean monthly biomass (μg / l) of common zooplankton species from the north and south basins of Lake Taal for the year 2008.

Fig. 5 in Spatial patterns of zooplanktivore Chirostoma species (Atherinopsidae) during water-level fluctuation in the shallow tropical Lake Chapala, Mexico: seasonal and interannual analysis

Fig. 5. (left column) Distribution-based Redundancy Analysis (db-RDA) ordination diagram of Lake Chapala with environmental variables (thick arrows), atherinopsids species (italic letters), sampling sites (numbers), and principal coordinates axes (thin arrows) at dry season (a: May of 1999) and rainy season (b: August of 1999; c: 2000). The fish are: jordani = Chirostoma jordani; consocium = Chirostoma consocium; labarcae = Chirostoma labarcae. The environmental variables are: Temp = temperature, DO = dissolved oxygen, Sal = salinity. In figure 5c shallow sites are in italic and deep sites in regular.

Fig. 3 in Spatial patterns of zooplanktivore Chirostoma species (Atherinopsidae) during water-level fluctuation in the shallow tropical Lake Chapala, Mexico: seasonal and interannual analysis

Fig. 3. GAM results for May and August of site influence on fish density to show differential distribution of species in Lake Chapala. a: Chirostoma jordani; b: Chirostoma consocium; c: Chirostoma labarcae. Circles represent the residuals. Spline fit (solid line) is bound by 95% confidence intervals (dotted lines).

Fig. 2 in Spatial patterns of zooplanktivore Chirostoma species (Atherinopsidae) during water-level fluctuation in the shallow tropical Lake Chapala, Mexico: seasonal and interannual analysis

Fig. 2. GAM results for May of environmental characteristics influence on fish density. a: effect of depth (m) on Chirostoma jordani; b: effect of temperature (°C) on C. jordani; c: effect of salinity on C. consocium. Circles represent the residuals. Spline fit (solid line) is bound by 95% confidence intervals (dotted lines).

Fig. 1 in Spatial patterns of zooplanktivore Chirostoma species (Atherinopsidae) during water-level fluctuation in the shallow tropical Lake Chapala, Mexico: seasonal and interannual analysis

Fig. 1. Map of Lake Chapala, Mexico. Numbers in bold represent sample sites and numbers in italic lake depths.

opencc-by-4.0Jun 2024View details →

The interaction of physical structure and nutrient loading drives ecosystem change in a large tropical lake over 40 years (DATA)

Datasets for manuscript entitled "The interaction of physical structure and nutrient loading drives ecosystem change in a large tropical lake over 40 years" Includes data collected by Fadum and Hall as well as unplublished data from Vaux and Goldman 1984. Abstract: Many lakes across the world are entering novel states and experiencing altered biogeochemical cycling due to local anthropogenic stressors. In the tropics, understanding the drivers of these changes can be difficult due to a lack of documented historic conditions or an absence of continuous monitoring that can distinguish between intra- and inter-annual variation. Over the last forty years (1980–2020), Lake Yojoa (Honduras) has experienced increased watershed development as well as the introduction of a large net-pen Tilapia farm, resulting in a dramatic reduction in seasonal water clarity, increased trophic state and altered nutrient dynamics, shifting Lake Yojoa from an oligotrophic (low productivity) to mesotrophic (moderate productivity) ecosystem. To assess the changes that have occurred in Lake Yojoa as well as putative drivers for those changes, we compared Secchi depth (water clarity), dissolved inorganic nitrogen (DIN), and total phosphorus (TP) concentrations at continuous semi-monthly intervals for the three years between 1979 and 1983 and again at continuous 16-day intervals for 2018–2020. Between those two periods we observed the loss of a clear water phase that previously occurred in the months when the water column was fully mixed. Seasonal peaks in DIN coincident with mixing suggest that an enhanced accumulation of ammonium in the hypolimnion (the bottom layer of a stratified lake) during stratification, and release to the epilimnion (the top layer of a stratified lake) with mixing maintains high algal abundance and subsequently low Secchi depth during what was previously the clear water phase. This interaction of nutrient loading and Lake Yojoa's monomictic stratification regime illustrates a key phenomenon in how physical water column structure and nutrients interact in tropical monomictic lakes. This work highlights the need to consider nutrient dynamics of warm anoxic hypolimnions, not just surface water nutrient concentrations, to understand environmental change in these societally important but understudied ecosystems.   (for more recent years of data collection see additional zenodo repositories by Fadum and/or Hall)

opencc-by-4.0Jun 2024View details →

Dataset for "The Role of Microbial Communities in Biogeochemical Cycles and Greenhouse Gas Emissions within Tropical Soda Lakes"

Here, we make available 27 raw metagenomic files in fastq.gz associated to the article: "The Role of Microbial Communities in Biogeochemical Cycles and Greenhouse Gas Emissions within Tropical Soda Lakes". This files is not paired, with forward as _1.fastq.gz and reverse as _2.fastq.gz. The abstract of manuscript is described below: Abstract Although anthropogenic activities are the primary drivers of increased greenhouse gas (GHG) emissions, it is crucial to acknowledge that wetlands are a significant source of these gases. Brazil's Pantanal, the largest tropical inland wetland, includes numerous lacustrine systems with freshwater and soda lakes. This study focuses on soda lakes to explore potential biogeochemical cycling and the contribution of biogenic GHG emissions from the water column, particularly methane. Both seasonal variations and the eutrophic status of each examined lake significantly influenced GHG emissions. Eutrophic turbid lakes (ET) showed remarkable methane emissions, likely due to cyanobacterial blooms. The decomposition of cyanobacterial cells, along with the influx of organic carbon through photosynthesis, accelerated the degradation of high organic matter content in the water column by the heterotrophic community. This process released byproducts that were subsequently metabolized in the sediment leading to methane production, more pronounced during periods of increased drought. In contrast, oligotrophic turbid lakes (OT) avoided methane emissions due to high sulfate levels in the water, though they did emit CO2 and N2O. Clear vegetated oligotrophic turbid lakes (CVO) also emitted methane, possibly from organic matter input during plant detritus decomposition, albeit at lower levels than ET. Over the years, a concerning trend has emerged in the Nhecolândia subregion of Brazil's Pantanal, where the prevalence of lakes with cyanobacterial blooms is increasing. This indicates the potential for these areas to become significant GHG emitters in the future. The study highlights the critical role of microbial communities in regulating GHG emissions in soda lakes, emphasizing their broader implications for global GHG inventories. Thus, it advocates for sustained research efforts and conservation initiatives in this environmentally critical habitat.

Figure 7 in Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Figure 7. NMDS diagram of macroinvertebrates in the sampled periods. (A) NMDS: structure; (B) NMDS: composition.

Figure 1 in Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Figure 1. Study site and sampling stations (P1, P2, and P2) in Barbosa Lake (the circle shows the connection site between the lake and the river).

Figure 4 in Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Figure 4. Means and standard deviations of root biomass of E. azurea (g.DW–1) in Barbosa Lake during the study period.

Figure 2 in Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Figure 2. Scheme of an adult E. azurea individual showing the sampled root mass in sequential direction from the apical to the basal parts of the plant.

Fig. 1 in Trophic interactions among sympatric zooplanktivorous fish species in volume change conditions in a large, shallow, tropical lake

Fig. 1. Lake Chapala, Mexico. Numbers in bold represent the sampling sites, in italics depths contours (m).

opencc-by-4.0Oct 2023View details →

Dominant nitrogen metabolisms of a tropical monomictic lake identified using genome resolved metatranscriptomics

Dataset for manuscript entitled "Dominant nitrogen metabolisms of a tropical monomictic lake identified using genome resolved metatranscriptomics" Abstract: Reactive nitrogen (N) is one of the principal drivers of primary productivity across aquatic ecosystems. However, N cycling in tropical inland waters is less well understood relative to temperate ecosystems. In particular, N cycling in monomictic tropical lakes may be distinct from that of their temperate counterparts due to the warm (>20 °C) temperatures of their anoxic hypolimnions (deepest portion of a stratified water column). These warm anoxic conditions have the potential to dramatically alter ecosystem biogeochemistry by releasing anaerobic metabolic pathways from temperature limitations that are present in anoxic strata of lake ecosystems at higher latitudes. To explore dominant N transformation pathways under warm anoxic conditions, we combined measurements of geochemistry and water column thermophysical structure with genome resolved metatranscriptomic analyses of the water column microbiome in Lake Yojoa, Honduras. Lake Yojoa is characterized by a pronounced accumulation of ammonium in the hypolimnions during stratification, beginning in May, and an annual mixing event that releases reactive N to the photic zone, in November. We sampled Lake Yojoa both above (1m) and below (16m) the thermocline at three locations, in June 2021, when the water column was stratified, and again at the same depths and locations in January 2022, when the water column was mixed. We identified 335 different lineages and significantly different microbiome membership between seasons and, in June, between depths. Expression of genes associated with N metabolic pathways was highest in June below the thermocline. In particular, we found nrfA, along with other respiratory NO2- reductases, was upregulated relative to other N metabolism genes in the June hypolimnions, suggesting that dissimilatory nitrate reduction to ammonium (DNRA) was partially responsible for the previously observed ammonium accumulation. DNRA is infrequently identified as a dominant N transformation pathway in natural aquatic ecosystems. This work highlights the need to better define N biogeochemistry in the poorly understood warm anoxic hypolimnions of tropical lake ecosystems. Defining the dominant anaerobic pathways when temperature is not limiting is one key to providing a more complete understanding of how rapidly occurring global change is altering tropical inland waters. Files described below:  Yojoa_572_MAGs_scaffolds.fna.zip scaffolds for 572 dereplicated MAGs  Yojoa_572_MAGs_annotations.tsv.zip DRAM annotations for 572 dereplicated MAGs  bipartitionsBranchLabels.nxr_nar_for_tree_aligned.fasta_mode_low.renamed  phylogenetic tree for nar/nxr genes bipartitionsBranchLabels.amo_pmo_fortree_aligned.fasta_mode_low.renamed phylogenetic tree for amo/pmo genes YojoaMasterSheet_final.xls MAG inventory with accession numbers and quality stats MetaT_norm.counts.rpk_edger.bins_mean.csv mean geTMM values per bin expressed in metatranscriptomic data MetaT_geTMM_norm.counts.rpk_edger_genes.csv geTMM values per gene expressed in metranscriptomic data geochem_data_Yojoa.csv geochemical data from each location including NH4+, NO3-, total phosphorus (TP), and dissolved organic carbon (DOC) profile_data_Yojoa.csv depth profile data at each location including temperature and dissolved oxygen measurements

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Figure 6 in Temporal variability of the macroinvertebrate community associated with Eichhornia azurea (Swarts) Kunth (Pontederiaceae) in a lake marginal to a tropical river

Figure 6. Box-plots of macroinvertebrates community richness (expressed in log values).