Zooplankton responses to simulated marine heatwave in the Mediterranean Sea using in situ mesocosms

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 cel..., 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, Mo..., , # 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 trap...