DOI: 10.5061/dryad.8cz8w9gwj
title: Data from: Plankton recruitment from coastal sediments under different temperature and light treatments

description: In highly seasonal systems, the emergence of planktonic resting stages
 from the sediment is a key driver for bloom timing and plankton community
 composition. The termination of the resting phase is often linked to
 environmental cues, but the extent to which recruitment of resting stages
 is affected by climate change remains largely unknown for coastal
 environments. Here we investigate phyto- and zooplankton recruitment from
 oxic sediments in the Baltic Sea in a controlled experiment under proposed
 temperature and light increase during the spring and summer. We find that
 emergence of resting stage differs between seasons and the abiotic
 environment. Phytoplankton recruitment from resting stages were high in
 spring with significantly higher emergence rates at increased temperature
 and light levels for dinoflagellate and cyanobacteria than for diatoms,
 which had highest emergence under cold and dark conditions. In comparison,
 copepod hatchlings were most abundant in summer and emergence was not
 affected by increased temperature and light levels. These results show
 that activation of plankton resting stages are affected to different
 degrees by increasing temperature and light levels, indicating that
 climate change affects plankton dynamics through processes related to
 resting stage termination with potential consequences for bloom timing,
 community composition and trophic mismatch.
description: Twenty-four sediment cores were collected with a
 Multicorer (K.U.M. Umwelt und Meerestechnik, Kiel GmbH), fitted with 4
 plexiglass tubes measuring 10 cm (inner diameter) and subsampled with
 plexiglass tubes (25 cm high, 7.4 cm inner diameter with a surface area of
 0.004 m<sup>2</sup>) from a depth of 21 m in the northern
 Baltic Sea proper (58°50´N, 17°33´E). The same tubes were used for the
 microcosm experiments. The ratio of sediment to overlaying bottom water
 (451 ml) in each subsample was about 1:1. The smaller tubes (hereafter
 called microcosms) were kept cold and dark from collection until being
 placed in a temperature-controlled room set to <em>in
 situ</em> bottom temperature for 24 h to allow any suspended
 material to settle to the bottom. Before deployment of the multicorer,
 bottom water was collected with a Niskin bottle, and temperature, oxygen
 and light intensity was measured at 20 m depth by use of a CTD (Sea
 & Sun Technology GmbH). Sampling was conducted once in the late
 June 2019 (summer) and early March 2020 (spring). Light and oxygen
 measurements at 20 m were 2.73 µE m<sup>-2</sup> and 7.26 ml
 l<sup>-1 </sup>in spring, and 1.69 µE and 8.83 ml
 l<sup>-1</sup> in summer, respectively. In comparison, light
 values below the water surface were 471 µE m<sup>-2</sup> in
 spring and 1042.46 µE m<sup>-2</sup> in summer, respectively. 
 Before the experimental start, water overlaying
 the sediment was siphoned off with syringes as close as possible to the
 sediment, leaving approximately 5 mm of water. Siphoning off the initial
 water did, however, not completely remove adult
 <em>Eurytemora</em> individuals in summer (Fig. S1). Thus, the
 experiment does not allow for separation of
 <em>Eurytemora</em>nauplii recruitment from the sediment or
 hatching from subitaneous eggs and are excluded from the analysis.
 Sterile, filtered (0.2 mm) bottom water from the collection site was
 drip-fed onto polystyrene foam disc, placed in each microcosm, to avoid
 resuspension of the sediment. After re-filling the microcosms with water,
 they were covered with parafilm with small holes in order to minimize
 evaporation but also to allow for gas exchange and light aeration through
 a single thin nylon tube per microcosm. Care was taken to allow minimal
 aeration of the upper few centimeters of the water to avoid any
 resuspension of the sediment. The 24 microcosms were placed in incubators
 divided into four abiotic factor treatments, with six replicates each:
 control CTRL was kept dark and at <em>in situ</em> bottom
 temperature (3 °C in spring and 9 °C in summer), elevated temperature (T), kept
 dark and subjected to an increase of +2 °C, light (L), subjected to the same temperature
 as CTRL and to weak green light emitting 0.5 mmol m<sup>-2</sup>
 s<sup>-1</sup> (Nascimento <em>et al.</em>,
 2008), and a combination
 of elevated temperature of +2 °C and weak green light (T+L). Treatment T was
 covered with a thick, dark plastic sheet to block all possible light from
 entering. A +2 °C temperature increase was based on average
 projected temperature increase for the Baltic Sea by the end of this
 century and weak green light representing underwater light change due to
 loss of sea ice (HELCOM,
 2021). Incubation of the experiment lasted for two
 weeks and samples were taken at day 7 and day 14 of the experiment. For
 this, the overlaying water in each microcosm was removed with syringes,
 treated with acid Lugol’s solution and placed in clear flasks covered with
 parafilm to prevent evaporation. Samples were allowed to settle for 6
 days, reduced to &lt; 100 ml by siphoning off the water surface and
 the remaining part transferred to clear 100 ml PVC bottles for storage at
 4 °C. At the end of the experiment, sediment from
 all microcosms was sieved through a 500 mm mesh for identification of benthic macrofauna
 to determine potential impacts through bioturbation or predation, which
 did not differ between treatments. All macrofauna retrieved was living,
 suggesting that the sediment remained well oxygenated throughout the
 experimental duration.  Identification and quantification of
 phytoplankton cells followed the Utermöhl method (Edler and Elbrächter,
 2010) with a sedimentation chamber of 100 ml. All samples were allowed to
 settle for 48 h according to standard guidance (HELCOM, 2017). Phytoplankton were identified to either class
 (dinoflagellates &lt; 20 mm), order (dinoflagellates &gt; 30
 mm), genus (diatoms and cyanobacteria) or
 dinoflagellate cysts, using http://nordicmicroalgae.org/galleries/HELCOM-PEG (2021). Phytoplankton cell density was calculated per L<sup> </sup>and carbon content per m<sup>2</sup> for comparison with plankton monitoring data and flux estimations from benthic to pelagic systems, respectively. Carbon content are based on Olenina <em>et al</em>. (Olenina <em>et al.</em>, 2006). Due to the relatively high taxonomic level of dinoflagellates and to avoid overestimation of C content, all C content calculations for cells &gt; 30 mm, was based on a size class of cells with a size &lt; 30 mm. Zooplankton were identified to genus level using Telesh et al. (2015). Nauplii biomass was calculated on naupliar stages I-III based on Gorokhova et al. (2016).  
description: # Data from: The response of plankton resting stage emergence to climate
 warming from coastal sediments --- Data represent the number of hatchlings
 from sediment cores subjected to different treatments for a volume of
 0.4513 L and surface area of 0.004 m2. Sediment was sampled a depth of 21
 m in the northern Baltic Sea proper (5850N, 1733E). ## Description of the
 data and file structure HatchingData-PP.txt Treatment: CTRL (control), L
 (light increase), T (temperature increase), T+L (light and temperature
 increase) Replicate: number of replicate Week: week of sampling, 1 or 2
 Season: time (season of the experiment: spring, summer) Peridiniales:
 number of hatchlings per 0.4513 L or 0.004 m2 Gymnodiniales: number of
 hatchlings per 0.4513 L or 0.004 m2 Dinoflagellate: number of hatchlings
 per 0.4513 L or 0.004 m2 Skeletonema: number of hatchlings per 0.4513 L or
 0.004 m2 Chaetoceros: number of hatchlings per 0.4513 L or 0.004 m2
 Coscinodiscus: number of hatchlings per 0.4513 L or 0.004 m2
 Dolichospermum: number of hatchlings per 0.4513 L or 0.004 m2
 Aphanizomenon: number of hatchlings per 0.4513 L or 0.004 m2 Nodularia:
 number of hatchlings per 0.4513 L or 0.004 m2 Total: total phytoplankton;
 number of hatchlings per 0.4513 L or 0.004 m2 Cyanobacteria: total
 cyanobacteria; number of hatchlings per 0.4513 L or 0.004 m2
 Dinoflagellates: total dinoflagellates; number of hatchlings per 0.4513 L
 or 0.004 m2 Diatoms: total diatoms; number of hatchlings per 0.4513 L or
 0.004 m2 HatchingData-ZP.txt Treatment: CTRL (control), L (light
 increase), T (temperature increase), T+L (light and temperature increase)
 Replicate: number of replicate Week: week of sampling, 1 or 2 Season: time
 (season of the experiment: spring, summer) Nauplii: total nauplii; number
 of hatchlings per 0.4513 L or 0.004 m2 Copepoda: total copepoda juvenile
 and adult stages; number 0.4513 L or 0.004 m2 Nauplii-Acartia: number of
 hatchlings per 0.4513 L or 0.004 m2 Nauplii-Eurytemora: number of
 hatchlings per 0.4513 L or 0.004 m2 Nauplii-Temora: number of hatchlings
 per 0.4513 L or 0.004 m2 Eurytemora: immature or adult stages; number of
 hatchlings per 0.4513 L or 0.004 m2 HatchingData-PP-Carbon.txt Treatment:
 CTRL (control), L (light increase), T (temperature increase), T+L (light
 and temperature increase) Replicate: number of replicate Week: week of
 sampling, 1 or 2 Season: time (season of the experiment: spring, summer)
 Peridiniales: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Gymnodiniales: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Dinoflagellate: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Skeletonema: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Chaetoceros: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Coscinodiscus: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Dolichospermum: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Aphanizomenon: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Nodularia: carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Total: total phytoplankton; carbon (biovolume) of hatchlings per 0.4513 L
 or 0.004 m2 Cyanobacteria: total cyanobacteria; carbon (biovolume) of
 hatchlings per 0.4513 L or 0.004 m2 Dinoflagellates: total
 dinoflagellates; carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Diatoms: total diatoms; carbon (biovolume) of hatchlings per 0.4513 L or
 0.004 m2 HatchingData-ZP-Carbon.txt Treatment: CTRL (control), L (light
 increase), T (temperature increase), T+L (light and temperature increase)
 Replicate: number of replicate Week: week of sampling, 1 or 2 Season: time
 (season of the experiment: spring, summer) Acartia: nauplii stages;carbon
 (biovolume) of hatchlings per 0.4513 L or 0.004 m2 Eurytemora: nauplii
 stages;carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2 Temora:
 nauplii stages; carbon (biovolume) of hatchlings per 0.4513 L or 0.004 m2
 Nauplii: total nauplii; carbon (biovolume) of hatchlings per 0.4513 L or
 0.004 m2 ## Code/Software R codes are available by demand