Changes in the elemental composition and stoichiometric ratios of the marine calanoid copepod Paracartia grani along development, reared in the laboratory fed the cryptophyte Rhodomonas salina, This study was supported by [CTM2017–84288-R] funded by Fondo Europeo de Desarrollo Regional (FEDER)/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Body length; C, N and P contents per individual; C:N molar ratio; C:P molar ratio; N:P molar ratio; Body volume; C, N and P contents per unit body volume, Peer reviewed

Changes in the elemental composition and stoichiometric ratios of the marine cyclopoid copepod Oithona davisae along development, reared in the laboratory fed the heterotrophic dinoflagellate Oxyrrhis marina, This study was supported by [CTM2017-84288-R] funded by Fondo Europeo de Desarrollo Regional (FEDER)/Ministerio de Ciencia, Innovación y Universidades-Agencia Estatal de Investigación, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Body length; C, N and P contents per individual; C:N molar ratio; C:P molar ratio; N:P molar ratio; Body volume; C, N and P contents per unit body volume, Peer reviewed

Diel vertical migration exposes zooplankton to fluctuating environmental conditions. In our study, we investigated the physiological costs of diel temperature fluctuations of vertical migration in the neritic marine copepod Centropages typicus, and checked whether the direct effects of fluctuating temperature on copepod performance may differ from those of average temperature conditions (Jensen’s inequality). We determined the rates of egestion, egg production, and respiration of copepods exposed to four temperature regimes including one treatment that simulated diel vertical migration (DVM, 10 h at 14 °C and 14 h at 19 °C) and three treatments with constant temperature (14, 17 and 19 °C). We found that the physiological
performance of C. typicus was not significantly different between fluctuating (DVM) and average (17 °C) temperature conditions, thus indicating that differences between varying and average temperature effects might not emerge in migrant zooplankton exposed to thermal variations of moderate magnitude (5 ºC). The copepods exposed to fluctuating temperature mimicking vertical migration (DVM) showed better performance (e.g. higher egg production) than those exposed to constant depth conditions (14 °C); however, no significant differences were detected when compared to constant surface conditions (19 °C). Our study indicates that neritic marine copepods experiencing daily moderate temperature fluctuations through vertical migration may not suffer physiological costs due to temperature associated with this behaviour. In this sense, these animals might have physiological mechanisms to compensate diel temperature fluctuations, which would represent a particularly relevant preadaptation to cope with the increased thermal variability predicted in future climates, This study was framed within the project ZOOTHERM (CTM2017-84288-R, MICIU/AEI/FEDER, UE), and Manuel Olivares was supported financially by an FPU grant (FPU15/01747) from the Spanish Ministry of Education, Culture and Sport, Number of experiment, date of experiment, temperature, bottle volume, prey species, prey species AphiaID, copepod species, copepod species AphiaID, copepod stage, prey concentration, prey size, number of copepods per bottle, copepod size, incubation time, egestion rate, egg production rate, respiration rate, Peer reviewed

It is a contribution of the Marine Zooplankton Ecology Group (2017 SGR 87), Proper thermal adaptation is key to understanding how species respond to temperature. However, this is seldom considered in protozooplankton and mixoplankton experiments. In this work, we studied how two heterotrophic dinoflagellates (Gyrodinium dominans and Oxyrrhis marina), one heterotrophic ciliate (Strombidium arenicola), and one mixotrophic dinoflagellate (Karlodinium armiger) responded to warming, comparing strains adapted at 16, 19 and 22 °C and those adapted at 16 °C and exposed for 3 days at 19 and 22 °C (acclimated treatments). Neither CNP contents nor the corresponding elemental ratios showed straightforward changes with temperature, except for a modest increase in P contents with temperature in some grazers. In general, the performance of both acclimated and adapted grazers increased from 16 to 19 °C and then dropped at 22 °C, with a few exceptions. Therefore, our organisms followed the “hotter is better” hypothesis from 16 to 19 °C; above 19 °C, however, the results were variable. Despite the disparity in the responses between species and physiological rates, in general, it seems that 19 °C-adapted organisms performed better than acclimated-only organisms. However, at 22 °C, most species were at the limit of their metabolisms and were unable to fully adapt. Nevertheless, adaptation to higher temperatures conferred some advantages prior to sudden increases in temperature (up to 25 °C) that simulated a heatwave episode. In summary, adaptation to temperature seems to confer a selective advantage to protistan grazers within a narrow range (i.e., ca. 3 °C). Adaptation to much higher temperatures (i.e., 6 °C) does not confer any clear physiological advantage (with few exceptions; e.g., the mixotroph K. armiger), at least within the time frame of our experiments, This research was funded by Grant CTM2017-84288-R by Fondo Europeo de Desarrollo Regional (FEDER)/ Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI), and by Grant PID2020-118645RB-I00 by Ministerio de Ciencia e innovación (MCIN)/AEI/ 10.13039/501100011033 and by “ERDF A way of making Europe”. With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Para 4 especies: Volumen (µm3/depredador), Tasa crecimiento (µ 1/d), Tasa de ingestion (cells/ind/d), Eficiencia bruta de crecimiento (GGE, %), Peer reviewed

We have studied the phenotypic response, at the cellular and organismal levels, of the marine calanoid copepod Paracartia grani to short- and medium-term thermal stress, This research was supported by Grant [CTM2017-84288-R] funded by MCIN/ AEI /10.13039/501100011033/ and by FEDER Una manera de hacer Europa, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Survival, body composition stoichiometry, enzymatic biomarkers, LPO levels, ingestion rates, fecal pellet production rates, egg production rates, gross-growth efficiencies, respiration rates, Peer reviewed

We exposed the calanoid copepod Paracartia grani, reared in the laboratory at 19°C, to warmer conditions (22°C and 25°C) for 11 generations and examined the direct effects of temperature on feeding, fecundity, development, population sex ratio and somatic traits (adult and egg sizes and adult carbon content), This research was funded by Grants [CTM2017-84288-R and PID2020-118645RB-I00] by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. CJ was supported by Grant [PRE2018-084738] funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Rearing temperature, generation, prosome length, carbon content, ingestion rate, egg production rate, egg diameter, gross-growth efficiency, hatching success, Peer reviewed

The study of a species' thermal tolerance and vital rate responses provides useful metrics to characterize its vulnerability to ocean warming. Under prolonged thermal stress, plastic and adaptive processes can adjust the physiology of organisms. Yet it is uncertain whether the species can expand their upper thermal limits to cope with rapid and extreme changes in environmental temperature. In this study, we reared the marine copepod Paracartia grani at control (19°C) and warmer conditions (25°C) for >18 generations and assessed their survival and fecundity under short-term exposure to a range of temperatures (11-34°C). After multigenerational warming, the upper tolerance to acute exposure (24 hours) increased by 1-1.3°C, although this enhancement decreased to 0.3-0.8°C after longer thermal stress (7 days). Warm-reared copepods were smaller and produced significantly fewer offspring at the optimum temperature. No shift in the thermal breadth of the reproductive response was observed. Yet the fecundity rates of the warm-reared copepods in the upper thermal range were up to 21-fold higher than the control. Our results show that chronic warming improved tolerance to stress temperatures and fecundity of P. grani, therefore enhancing its chances to persist under extreme heat events, This research was funded by Grants CTM2017-84288-R and PID2020-118645RB-I00 by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”. “ERDF A way of making Europe” C. J. was supported by Grant [PRE2018-084738] funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Rearing temperature, generation, exposure temperature, survival 24h, survival 7d, egg production rate, fitness index, egg diameter, female prosome length, Peer reviewed

We studied the impact of sublethal thermal stress (28ºC, 7 days) on the physiological rates and metabolic balance of three populations of the calanoid copepod Paracartia grani, reared at 19, 22 and 25ºC for multiple generations, This research was funded by Grants CTM2017-84288-R, PID2020-118645RB-I00 and PID2023-150548NB-I00 by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe” and ERDF/EU. C. J. was supported by Grant [PRE2018-084738] funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”. The open-access publication fee was covered by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI), With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), Peer reviewed