L. Jimenez-Segura, J.D. Restrepo-Angel, A Hernandez-Serna. Front. Environ. Sci., 06 October 2022 https://doi.org/10.3389/fenvs.2022.866575

We review knowledge on the Magdalena River in Colombia and its fish to identify those drivers that influence the artisanal fisheries production. We identify eight direct drivers (four natural and four anthropogenic) and at least four indirect drivers. Those drivers modify conditions in the fluvial network that promote fish movements, reproduction, and their larvae survivor. Landscape, rains, floods, connectivity of the fluvial net as land cover change, water pollution, hydropower, and alien species are the natural and anthropogenic direct drivers described in this article. The river–lake interaction dynamics in the Magdalena River are determined by two rainy cycles per year. Two seasonal flooding periods induce two cycles in the biological productivity of floodplains because water and sediment inputs. The most visible consequences in these hydrological cycles are the migrations of potamodromous fish and the periodic increase in the artisanal fishery production. Major floodplains are reducing their storage capacity by trapping ∼10%–40% of upstream sediment production. This process induces many research questions about rates of biomass production, carbon fluxes in the basin, impacts of human-induced erosion, and increasing rates of sediment load on floodplain connectivity, but still there is not enough data to answer them. Finally, we make some suggestions toward the sustainability of the Magdalena floodplains. The well-being of the floodplain ecosystems and their connectivity with the main river are the main tools to preserve and manage the ecosystem services of the Magdalena River and its floodplains lakes.

P. V Potapov; X. Lia, A. Hernandez-Serna, A. Tyukavina, M. C. Hansen, A. Kommareddy, A. Pickens, S. Turubanova, H. Tanga, C. Edibaldo Silva, J. Armstona, R. Dubayah, J. Bryan Blair, M Hofton. Remote Sensing of Environment. Volume 253, February 2021, 112165 https://doi.org/10.1016/j.rse.2020.112165

A new, 30-m spatial resolution global forest canopy height map was developed through the integration of the Global Ecosystem Dynamics Investigation (GEDI) lidar forest structure measurements and Landsat analysis-ready data time-series (Landsat ARD). The GEDI RH95 (relative height at 95%) metric was used to calibrate the model. The Landsat multi-temporal metrics that represent the surface phenology serve as the independent variables. The “moving window” locally calibrated and applied regression tree ensemble model was implemented to ensure high quality of forest height prediction and global map consistency. The model was extrapolated in the boreal regions (beyond the GEDI data range, 52°N to 52°S) to create the global forest height prototype map. 

Data download: https://glad.umd.edu/dataset/gedi/ 

P. V. Potapov, A. Tyukavina, .S Turubanova, A. Hernandez-Serna, Y Talero, M.C. Hansen, D. Saah, K. Tenneson, A. Poortinga, A. Aekakkararungroj, F. Chishtie, P. Towashiraporn, B. Bhandari, KS Aung, NH Quyen. Remote Sensing of Environment, Volume 232, October 2019, 111278; doi: 10.1016/j.rse.2019.111278.

Spatially and temporally consistent vegetation structure time-series have great potential to improve the capacity for national land cover monitoring, to reduce latency and cost of international reporting, and to harmonize regional land cover characterizations. Here we present a semi-automatic, operational algorithm for mapping and monitoring of woody vegetation canopy cover and height at a regional scale using freely available Landsat time-series data. The presented algorithm employs automatic data processing and mapping using a set of lidar-based vegetation structure prediction models. Changes in vegetation cover are detected separately and integrated into the structure time-series. Sample-based validation and inter-comparison with existing datasets demonstrates the spatial and temporal consistency of our regional data time-series. The dataset reliably reflects changes in tree cover (tree cover loss user's accuracy of 0.84 and producer's accuracy of 0.75) and can serve as a tool to map annual forest extent (user's accuracy of 0.98 and producer's accuracy of 0.81 for 10% canopy cover threshold to define the forest class). The tree height estimates are consistent with a GLAS-based global map (mean average error of 3.7 m, the correlation coefficient of 0.92 and the R2 of 0.85). Total forest area decreased by 6.2% within the region, and 11.1% of year 2000 primary forest area was lost by 2017. At the national level, Cambodia demonstrated the highest rate of deforestation, with a net forest area loss of 22.5%. We estimated that 21.3% of 2017 forest cover had an age of 17 years or less, illustrating the intensive forest land uses within the region. The time-series product is suitable for mapping annual land cover and inter-annual land cover change using customized class definitions.

Data download: https://landcovermapping.org/en/

A Hernandez-Serna, C Granado-Lorencio and LF Jiménez-Segura. Journal of Applied Ichthyology. 31: 638–645. 2015

Investigated were whether fish assemblages in 35 neotropical floodplain lakes along the Magdalena River, Colombia (ranging from 4 to 2333 ha) have a trophic structure that is dependent on fish body size within the diel cycle (24 h), and whether any changes to the trophic structure of fish assemblages occur during the diel cycle. Sampling was done during diel cycles in the rainy seasons between 2008 and 2011 (ten lakes in 2008, 20 in 2010, and five in 2011). Small fish (27–87 mm) were most active from 06:01 to 18:00, while larger predatory fish (>87 mm) were inactive during this time. In addition to fish body size, trophic group composition also varied throughout the diel cycle: insectivores, piscivores, and omnivore-insectivores were the dominant groups from 06:01 to 18:00; carnivores, carnivore-insectivores, and detritivores dominated from 18:01 to 06:00. This study highlights the importance of fish size in predicting predator-prey interactions during different periods of the diel cycle.

N Alvarez-Berríos, M Campos-Cerqueira, A Hernandez-Serna, J.A Delgado C, F Román-Dañobeytia and T. Mitchell Aide Aide. Tropical Conservation Science. Vol. 9 (2): 832-851, 2016. 

bstract Artisanal and small-scale gold mining (ASM) is becoming a significant cause of environmental degradation in tropical ecosystems. In this study, we conducted a rapid assessment on the impact of an ASM gold mine on the vocalizing avian and anuran communities in the buffer zone of the Tambopata National Reserve in Peru. We used seven audio recorders (three near an active mine, two in an abandoned mine, and two in an adjacent forest) to collect 2900 recordings to generate soundscapes and compare acoustic activity patterns of birds and anurans among sites. We identified 56 bird species during the morning chorus (05:00-07:00) and 9 anurans species in the evening chorus (18:00-20:00). Bird speciesrichness wassimilar between the forest (28 bird species), the abandoned mine (25 species) and the active mine (24 species), but species richness of birds sensitive to disturbance was much lower in the active mine. In contrast, anuran species richness was highest in the active mine (5 species) and lowest in the forest (2 species). Results indicate that acoustic monitoring and soundscape analysis can be effective tools for evaluating the impact of mining activities on vocalizing species, and could become useful tools in rapid environmental impact assessments for mitigation and conservation strategies in ASM mining regions. 

Data download: https://arbimon.sieve-analytics.com/ 

V  Márquez Velásquez, R Galdino Leite, A Hernandez-Serna, F Alvarado.  2020. Journal of Fish Biology. doi : 10.1111/jfb.14565 

Analysis of feeding habits was performed for early life stages of Brachyplatystoma rousseauxii and Brachyplatystoma filamentosum in the Madeira River, Brazil. Stomach contents of B. rousseauxii and B. filamentosum were identified and analyzed. The percentage of frequency of occurrence (%FO) and area (%A) and the alimentary index IAi were used to quantify the feeding habits of the two species. The order Diptera represented the most important item consumed by both species. This is the first analyses of the trophic ecology of these ecologically and economically important species of the Amazonian region in early life stages.

Granado-Lorencio,  A Gulfo, F Alvarez, LF Jiménez-Segura, JD Carvajal-Quintero, and A Hernandez-Serna. 2012. Journal of Tropical Ecology. 28:271-279. 

A number of studies have pointed out that abiotic factors and recolonization dynamics appear to be more important than biotic interactions in structuring river–fish assemblages. In this paper, we studied the fish assemblages in 27 floodplain lakes, with perennial connection to the river, in the middle section of the Magdalena River (Colombia), to examine spatial pattern in freshwater fish diversity in relation to some environmental parameters. Our objective was to examine relationships between floodplain-lake fish communities and nvironmental variables associated with lake morphology, water chemistry and river–floodplain connectivity in a large river–floodplain ecosystem. During the study, a total of 18 237 fish were caught from 50 species (regional richness; 17 were migrants and 33 residents). In the present study, the most diverse order was Characiformes with 20 species, followed by Siluriformes, with 19 species. Characidae and Loricaridae were the richest families. The range of species richness (local richness) varied between five and 39 species. Similarity of local assemblages (using the presence–absence data) depends on the distance between lakes. A positive relationship was observed between the Ln of the total abundance of each species and the number of lakes where they were found. Out of all the environmental parameters taken in the lakes, only the size (Log Area) and relative perimeter length are significantly related to local assemblage species richness. It has not been possible to demonstrate that the connectivity (distance) from lakes to the main river can be considered a predictor of the local richness.

M.S., Ecology and Evolution, May 2016. Department of Biology. University of Puerto Rico, Puerto Rico, Advisor: T. M Aide. 

Acoustic signals are used for species recognition, mate choice, and resource defense, but the frequencies used are restricted by body-size, phylogeny, habitat structure, and biotic and abiotic sounds in the habitat. Acoustic space is a limited resource, and studies have suggested that species avoid competition by partitioning this space in time and frequency. Alternatively, other studies have reported temporal synchrony and spectral overlap among species. These studies have focused on individual taxonomic groups (e.g. fish, bird, insects, and anurans), and no study has assessed patterns of acoustic activity for all species in a community across a gradient of species richness. Here we compare the use of acoustic space (i.e. soundscape) in nine tropical forest sites, and show a highly significant positive relationship between the percent of acoustic space used and total bird, amphibian, and mammal species richness. If community richness is relatively low, species may avoid overlapping and maintain signals within the optimal frequency range of a given habitat, but in species-rich communities, species will encounter greater signal overlap and will be forced to use other frequencies. Our acoustic species richness hypothesis unifies the acoustic partitioning and network hypotheses by demonstrating how variation in species richness across sites affects the patterns of activity within the acoustic space. This novel approach for analyzing soundscapes contributes to our understanding of ecological community dynamics (e.g. niche theory) and provides useful tools for monitoring species in the context of restoration ecology, climate change, and conservation biology.