DOI: 10.5061/dryad.vt4b8gv1s
title: Data from: Zooplankton responses to simulated marine heatwave in the Mediterranean Sea using in situ mesocosms

description: Globally, marine heatwave frequency, intensity, and duration are on the
 rise, posing a significant threat to plankton communities, the
 foundational elements of the marine food web. This study investigates the
 ecological and physiological responses of a temperate plankton community
 in the Thau lagoon, north-western Mediterranean, to a simulated +3°C
 ten-day heatwave followed by a ten-day post-heatwave period in
 in-situ mesocosms. Our analyses encompassed zooplankton grazing,
 production, community composition in water and sediment traps, as well as
 oxidative stress and anti-oxidant biomarkers. The results revealed
 increased abundances of harpacticoid copepods and polychaete larvae during
 the simulated heatwave and post-heatwave event. Sediment trap data
 indicated elevated mortality, particularly dominated by polychaete larvae
 during the post-heatwave period. Oxidative stress biomarker (lipid
 peroxidation LPX) levels in the plankton community correlated with
 temperature, signaling cellular damage during the heatwave. LPX increased
 and proteins decreased with increasing salinity during the experiment.
 Offspring production peaked during the post-heatwave phase. Notably, the
 calanoid copepod Acartia clausi exhibited a preference for ciliates as its
 primary prey, constituting 20% of the overall available prey. Our findings
 suggest a potential shift in coastal zooplankton communities during future
 marine heatwaves, transitioning from calanoid mesozooplankton dominance to
 a system featuring meroplankton and/or harpacticoid copepods. Although
 species preying on microzooplankton may gain advantages in such
 conditions, the study underscores the damaging impact of heatwaves on
 organismal lipids, with potential consequences for reproduction, growth,
 and survival within marine ecosystems.
description: The mesocosm field experiment studying heatwave effects on the
 plankton community was conducted using the MEDIMEER platform
 (Mediterranean platform for Marine Ecosystems Experimental Research) based
 at the marine station of Sète (SMEL, University of Montpellier 2, 43° 24’
 49” N, 3° 41’ 19” E) in summer 2019. The experiment was conducted in the
 Thau lagoon in the western Mediterranean Sea which is oligotrophic and is
 connected to the sea via two permanent inlets.  The
 heatwave experiment was conducted between 24 May and 12 June 2019, during
 a total of 20 days. The size of the transparent mesocosm bags was 280 cm
 (length) and 120 cm (width), made of vinyl acetate polyethylene film
 (thickness: 200 µm), reinforced with nylon (Engineering Agency Haikonen
 Ky), and equipped with a 50 cm long sediment trap. Mesocosms were covered
 with a polyvinyl-chloride dome, which transmitted 73% of the
 photosynthetically active radiation PAR, to avoid external inputs and
 precipitation. A pump (Rule, Model 360) was immersed at 1 m depth to
 gently mix the mesocosm water. Two treatments, each in
 triplicate, were applied to six mesocosms. During the first 10 d of the
 experiment (D1–D10), the water temperature was raised +3°C in three
 mesocosms (heatwave H), while the three remaining mesocosms had natural
 lagoon temperature (control C). After this 10 days period (d11–d20), the
 temperature was returned to ambient water temperature (post-heatwave PH).
 During this period, the “control mesocosms” experienced the <em>in
 situ</em> lagoon temperature. In addition, two incubation mesocosms
 with the same water temperature as Control and Heatwave experimental
 mesocosms were established to incubate several samples, thereby avoiding
 contamination of the experimental mesocosms. We
 investigated the zooplankton community composition, vital rates (including
 grazing, production, survival, and oxidative stress), and the quantity and
 quality of zooplankton prey, assessing whether these factors were impacted
 by the heatwave. Further details in the manuscript:
 10.1371/journal.pone.0308846
description: # Zooplankton response to marine heatwave
 [https://doi.org/10.5061/dryad.vt4b8gv1s](https://doi.org/10.5061/dryad.vt4b8gv1s) ## Description of the data and file structure ### Files and variables #### File: Temperatures.xls **Description:** Temperature values in the mesocosms during the experimental period ##### Variables Temperature (degree C) #### File: offspring.xls **Description:** Egg and nauplii copepod production in the mesocosms during the experimental period ##### Variables * eggs L-1, nauplii L-1, eggs+nauplii L-1 #### File: Copepodgrazing.xls **Description:** Initial copepod prey (abundance and biomass), clearance rates and ingestion rates on chlorophylla, diatoms, ciliates and dinoflagellates ##### Variables * Chlorophylla (mg L-1), diatoms (mg L-1), ciliates (mgC L-1), dinoflagellates (mgC L-1), clearance rates (ml ind-1 day-1), ingestion (%body Carbon ingested day-1) #### File: sediment\_traps.xls **Description:** Zooplankton composition in the sediment traps during the experimental period ##### Variables * Abundance ind L-1 #### File: Communities.xls **Description:** Zooplankton communities in the mesocosms during the the experimental period ##### Variables * Abundance ind L-1 #### File: Data\_for\_repository\_biomarkers\_7.8.2024.csv **Description:** Biomarkes of copepods in the mesocosms ##### Variables * lipid peroxidation * FOX/mg protein; FOX= ferrous oxidation xylenol orange; glutathione-s-transferase: * umol/min/mg;catalase  * umol/min/mg; protein * mg; treatment; 1=control * 2 = treatment; days;"mesocosms; control: 1-3 * treatment: 4-6: ## Code/software General Linear Models (GLM) in SPSS version 28.0 were used to analyze differences between Treatment For linear mixed models (LMMs), based on restricted maximum likelihood RML estimation, we used the package *lmerTest* was used in the free software R, version 3.4.3 ([www.R-project.org](http://www.R-project.org)).