Phytoplankton face environmental nutrient variations that occur in the dynamic upper layers of the ocean. Phytoplankton cells are able to rapidly acclimate to nutrient fluctuations by adjusting their nutrient-uptake system and metabolism. Disentangling these acclimation responses is a critical step in bridging the gap between phytoplankton cellular physiology and community ecology. Here, we analyzed the dynamics of phosphate (P) uptake acclimation responses along different P temporal gradients by using batch cultures of the diatom Phaeodactylum tricornutum. We employed a multidisciplinary approach that combined nutrient-uptake bioassays, transcriptomic analysis, and mathematical models. Our results indicated that cells increase their maximum nutrient-uptake rate (Vmax) both in response to P pulses and strong phosphorus limitation. The upregulation of three genes coding for different P transporters in cells experiencing low intracellular phosphorus levels supported some of the observed Vmax variations. In addition, our mathematical model reproduced the empirical Vmax patterns by including two types of P transporters upregulated at medium-high environmental and low intracellular phosphorus levels, respectively. Our results highlight the existence of a sequence of acclimation stages along the phosphate continuum that can be understood as a succession of acclimation responses. We provide a novel conceptual framework that can contribute to integrating and understanding the dynamics and wide diversity of acclimation responses developed by phytoplankton.

Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates during two Lagrangian surveys in inner and eastern locations of the Eastern North Atlantic Subtropical Gyre province (NAST-E). Our design included two phytoplankton size fractions (0.2–5 µm and >5 µm) and five depths, allowing us to characterize differences in growth and grazing rates between size fractions and depths, as well as to estimate vertically integrated measurements. Phytoplankton growth rates were high (0.11–1.60 d⁻¹), especially in the case of the large fraction. Grazing rates were also high (0.15–1.29 d⁻¹), suggesting high turnover rates within the phytoplankton community. The integrated balances between phytoplankton growth and grazing losses were close to zero, although deviations were detected at several depths. Also, O₂ supersaturation was observed up to 110 m depth during both Lagrangian surveys. These results add up to increased evidence indicating an autotrophic metabolic balance in oceanic subtropical gyres.

We have supplemented available, concurrent measurements of fresh weight (W, g) and body carbon (C, g) (46 individuals, 14 species) and nitrogen (N, g) (11 individuals, 9 species) of marine gelatinous animals with data obtained during the global ocean MALASPINA 2010 Expedition (totalling 267 individuals and 33 species for the W versus C data; totalling 232 individuals and 31 species for the N versus C data). We then used those data to test the allometric properties of the W versus C and N versus C relationships. Overall, gelatinous organisms contain 1.13 ± 1.57% of C (by weight, mean ± SD) in their bodies and show a C:N of 4.56 ± 2.46, respectively, although estimations can be improved by using separate conversion coefficients for the carnivores and the filter feeders. Reduced major axis regression indicates that W increases isometrically with C in the carnivores (cnidarians and ctenophores), implying that their water content can be described by a single conversion coefficient of 173.78 gW(g C)⁻¹, or a C content of 1.17 ± 1.90% by weight, although there is much variability due to the existence of carbon-dense species. In contrast, W increases more rapidly than C in the filter feeders (salps and doliolids), according to a power relationship W = 446.68C^1.54. This exponent is not significantly different from 1.2, which is consistent with the idea that the watery bodies of gelatinous animals represent an evolutionary response towards increasing food capture surfaces, i.e. a bottom-up rather than a top-down mechanism. Thus, the available evidence negates a bottom-up mechanism in the carnivores, but supports it in the filter feeders. Last, N increases isometrically with C in both carnivores and filter feeders with C:N ratios of 3.89 ± 1.34 and 4.38 ± 1.21, respectively. These values are similar to those of compact, non-gelatinous organisms and reflect a predominantly herbivorous diet in the filter feeders, which is confirmed by a difference of one trophic level between filter feeders and carnivores, according to stable N isotope enrichment data.

The spring phytoplankton bloom plays a key role in the dynamics of temperate and polar seas. Nevertheless, the mechanisms and processes behind these blooms remain a subject of considerable debate. We analyzed the influence of deep mixing during winter on the spring phytoplankton bloom in the Cantabrian Sea (southern Bay of Biscay). To this end, we combined long‐term physical and biogeochemical in situ data (1993–2012) and satellite observations (1997–2012). Deeper winter mixing led to higher nitrate and chlorophyll concentrations through the water column during the spring bloom. However, this effect was modified by short‐term variability in near‐surface stratification in spring. Winter‐mixing preconditioning also influenced different spring bloom metrics: deeper and later mixing in winter was followed by later blooms with a larger peak. In these enhanced blooms, nitrate was taken up at faster rates, indicating higher rates of phytoplankton production. Winters with weaker mixing (that led to weaker spring blooms) were associated with warmer surface temperatures. This relationship suggests that the multi‐decadal trend toward warmer surface temperatures in the Bay of Biscay may promote a decrease in the magnitude of the spring bloom, which could impact upper trophic levels and also deep carbon export in the future.

The application of methoprene and access to protein in adult diet has been shown to enhance mating success in male melon flyBactrocera cucurbitaeCoquillett (Diptera: Tephritidae), supporting their incorporation into operational area‐wide programmes integrating the Sterile Insect Technique (SIT). The objective of the present study was to investigate the effect of methoprene, diet including protein and feeding days on male starvation survival to determine the minimum number of feeding days required prior to male release in the field. The study was performed in the laboratory by treating males with (i) both protein and methoprene (M+P+), (ii) only protein (M−P+), (iii) only methoprene (M+P−) or (iv) untreated (M−P−). The males were starved after exposure for an increasing number of days (1–7) to their respective treatment. Mean longevity was highest after 3‐day post‐emergence feeding duration for M+P+, M+P− and M−P− males, but 4 days of feeding for M−P+ males. Additional feeding days after 4 days, did not increase male survival and feeding for 7 days decreased starvation survival of sugar‐fed males. Application of methoprene and/or access to diet including protein had no adverse effect on starvation survival but feeding duration had a significant positive effect on starvation survival. To the contrary, the current study provides a strong evidence for the benefits of methoprene application and protein incorporation into the adult diet of sterile males. Treated males achieve higher sexual success, reach sexual development several days earlier, and are therefore much closer to sexual maturity when released in SIT action programmes after being held in the fly emergence and release facility for a post‐emergence feeding duration of at least 3 days.