Biology subjects

Weber de Melo, V.

Publications and source records attributed to Weber de Melo, V..

2 recordsLinked to original sources

bioRxiv2026

Divergent transcriptional responses of conserved cellular machinery to warming and phosphorus limitation in freshwater phytoplankton

Lakes are simultaneously warming and becoming phosphorus limited, but whether phytoplankton taxa of the same phylum respond through similar molecular mechanisms remains unclear, challenging a common assumption underlying predictions of ecological responses to environmental change. We cultured four freshwater phytoplankton species, including two diatoms (Fragilaria crotonensis and Nitzschia palea) and two cyanobacteria (Microcystis aeruginosa and Synechococcus sp.), across factorial gradients of temperature (20, 24 and 28 {degrees}C) and phosphorus (P) limitation, and characterized gene expression using RNA-seq, differential expression analysis and signed gene set enrichment. We generated predictions for expected responses for categories of gene functions derived from the growth rate (GRH) and temperature-dependent physiology hypotheses (TDPH). Warming and P limitation engaged largely the predicted functional categories in all species, however the direction of the response was not conserved, even within phyla--the two cyanobacteria regulated photosynthesis, ribosomal and chaperone genes in opposite directions. Ribosome- and translation-related genes gave the strongest warming response and, in N. palea, reversed direction within the species, increasing between 20 and 24 {degrees}C and decreasing between 24 and 28 {degrees}C, below the strain's thermal optimum estimated under moderate P limitation. Ribosomal allocation thus supported each hypothesis in different species and temperature ranges and was not predicted by thermal position alone. Where the interaction effects could be tested, P limitation rarely recruited novel pathways but modified existing warming responses, suppressing them in F. crotonensis and amplifying and redirecting them in M. aeruginosa. Molecular responses to combined drivers therefore diverge among related taxa, cautioning against aggregating species into functional groups when forecasting phytoplankton responses to global change.

molecular biology↗

bioRxiv2025

Warm-loving species perform well under limiting resources:trait combinations for future climate

Ecosystems are warming alongside shifts in other abiotic factors, leading to interactive effects on populations and communities. This underscores the importance of studying how organisms respond to multiple environmental changes simultaneously. In aquatic ecosystems, as surface waters of lakes and oceans warm, longer and stronger periods of thermal stratification lead to changes in resource (light and nutrient) availability. We investigate the combined effect of temperature and resource availability on 19 populations (comprising 17 species) of freshwater phytoplankton to examine how temperature influences the minimum resource requirements (and Monod parameters) for light, nitrogen, and phosphorus. We also evaluate how resource availability affects each populations thermal traits (i.e. thermal performance curve -TPC-parameters). When averaged across all populations, the requirements for light and phosphorus tended to display a U-shaped relationship along temperatures. Individual populations varied greatly in their responses to temperature, leading to shifts in the identity of the best competitor across the thermal gradient, particularly for nitrogen and phosphorus. TPC responses to resource limitation were highly variable, but thermal optima and maxima of individual populations often decreased with resource limitation, and thermal breadths (range where growth is 80% or more of its maximum) often increased due to a flattening of TPCs. Across all populations and resource types, the maximum optimum temperature across resource levels (maximum Topt) tended to be positively correlated with the temperature at which they had the lowest resource requirements (minimum R*). However, the temperature at which populations were the best competitors tended to be [~]5 {degrees}C colder on average than the temperature at which they grew the fastest. The populations with the highest thermal optima also had the lowest minimum resource requirements. Our findings reveal trait associations suggesting that some taxa already exhibit trait combinations that would support high performance under future warm and resource-limited conditions.

ecology↗