DOI: 10.5061/dryad.6hf6b
title: Data from: Impact of native and non-native aquatic plants on methane emission and phytoplankton growth

description: Freshwater plants affect the ecosystem functioning of shallow aquatic
 ecosystems. However, because native plants are threatened by environmental
 change such as eutrophication, global warming and biological invasions,
 continued ecosystem functioning may be at risk. In this study, we explored
 how the growth of native and non-native plant species in eutrophic, warm
 conditions impacts two plant ecosystem functions: regulation of
 phytoplankton growth and methane emission. We expected that plants would
 inhibit phytoplankton growth, while for methane emission both inhibition
 and stimulation are possible. We conducted an outdoor experiment using
 monocultures of four native and four non-native freshwater plant species
 planted at three different densities, as well as a no-plant control.
 Monocultures of each species were planted in 65 L mesocosms and after
 three weeks of acclimatisation each mesocosm was inoculated with
 phytoplankton. Subsequently, we added nutrients twice a week for eight
 weeks, before harvesting the plant biomass. During these eight weeks, we
 measured chlorophyll-a concentration thirteen times and the diffusive
 methane emissions once after four weeks. The mesocosms amplified the
 temperature of a warm summer so that plants were exposed to
 higher-than-average temperatures. We found that five plant species lost
 biomass, two species increased their biomass only at the highest initial
 plant density (native Myriophyllum spicatum and non-native Lagarosiphon
 major) and a single species increased its biomass at all densities (on
 average 14 times its initial mass; amphibious non-native Myriophyllum
 aquaticum). Overall, the mean biomass change of non-natives was positive,
 whereas that of natives was negative. This difference in biomass change
 between native and non-native plants did not relate to overall differences
 in phytoplankton mass or diffusive methane emissions. In mesocosms where
 submerged plant species gained biomass, chlorophyll-a concentration was
 lower than in the no-plant control and mesocosms with biomass loss.
 Diffusive methane emissions were highest in mesocosms where plants lost
 considerable biomass, likely because it increased substrate availability
 for methanogenesis. However, mesocosms where plant biomass increased had
 emissions similar to the no-plant control, hence we found no inhibitory
 effects of plant presence on diffusive methane emission. We conclude that
 plant growth in eutrophic, warm conditions varies strongly with plant
 identity. Our results furthermore suggest that plant identity determines
 whether the replacement of native by non-native freshwater plants will
 alter ecosystem functions such as regulation of phytoplankton growth and
 methane emission.
description: Water abiotics
 measurementsVariables: ID, Species,
 Density and Replicate are explained in metadata document. Each ID is an
 experimental unit. The variable Date gives date at which the following
 variables were measured: Temperature, pH1, Oxygen, Conductivity,
 Alkalinity, pH2, Turbidity, TON, NH4, PO4, NO2, NO3abiotics.txtepiphytonEpiphyton data from PVC strips. Variable mesocosmID links to metadata.txt file. Variable Sample links to original raw spectrophotometer file. Variable date gives the date. The following four variables were used to calculate the epiphyton and pheopigment density per surface area (last threecolumns): 665-0, 750-0, 665-a, 750-a, chl-a (ug), pheo (ug), surface (cm2)filamentousalgaeGives the amount of filamentous algal biomass that was removed per mesocosm (links to metadata.txt) for each date (columns).gasdataRaw output of Los Gatos measurements on greenhouse gas. Use gasmetadata.txt to infer when actual measurements took place.gasmetadataIs used to make sense of gasdata.txt in that it holds the timepoints (Time-In) and some metadata on experimental units (mesocosmID, Block). The variable Seconds is the recalculated timepoint on gasdata.txt using the time-in.overall-metadataHolds the metadata on the experimental units used in the experiment, comprising of a number for each mesocosm (mesocosmID), the name of the plant that grew in the mesocosm (plantName), a codified plant name (plantCode), its initial density (density), the replicate number assigned (replicate), the spatial position in the experimental mesocosm configuration (X, Y), the date at which the mesocosm was harvested (harvestDate) and whether a species is native or non-native (plantOrigin)phytoplanktonData on the phytoplankton measurements (twice per week). First metadata (ID Species Density Replicate), then actual data of Phytopam results: Diluted, GAIN, green (ug/l), yield, blue (ug/l), yield, brown (ug/l), yield, sumchl, DATEplantsData on plant biomass with variables mesocosmID (links to metadata.txt), DM.g.end (gives plant dry weight at harvest), PVI-after-acclimation (gives plant PVI three weeks after being planted), FM.g.start (fresh plant biomass at planting) and DMC (dry matter content).