Impact of native and non-native aquatic plants on methane emission and phytoplankton growth

TY - JOUR

T1 - Impact of native and non-native aquatic plants on methane emission and phytoplankton growth

AU - Grutters, B.M.C.

AU - Aben, Ralf Cornelis

AU - Kosten, S.

AU - Bakker, E.S.

N1 - 6345, AqE; Data Archiving: data archived at Dryad

PY - 2017

Y1 - 2017

N2 - Freshwater plants affect the ecosystem functioning of shallow aquatic ecosystems. However, because native plants are threatenedby environmental change such as eutrophication, global warming and biological invasions, continued ecosystem functioning maybe at risk. In this study, we explored how the growth of native and non-native plant species in eutrophic, warm conditions impactstwo plant ecosystem functions: regulation of phytoplankton growth and methane emission. We expected that plants would inhibitphytoplankton growth, while for methane emission both inhibition and stimulation are possible. We conducted an outdoorexperiment using monocultures of four native and four non-native freshwater plant species planted at three different densities, aswell as a no-plant control. Monocultures of each species were planted in 65 L mesocosms and after three weeks of acclimatisationeach mesocosm was inoculated with phytoplankton. Subsequently, we added nutrients twice a week for eight weeks, beforeharvesting the plant biomass. During these eight weeks, we measured chlorophyll-a concentration thirteen times and the diffusivemethane emissions once after four weeks. The mesocosms amplified the temperature of a warm summer so that plants wereexposed to higher-than-average temperatures. We found that five plant species lost biomass, two species increased their biomassonly at the highest initial plant density (native Myriophyllum spicatum and non-native Lagarosiphon major) and a single speciesincreased 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 biomasschange between native and non-native plants did not relate to overall differences in phytoplankton mass or diffusive methaneemissions. In mesocosms where submerged plant species gained biomass, chlorophyll-a concentration was lower than in the noplantcontrol and mesocosms with biomass loss. Diffusive methane emissions were highest in mesocosms where plants lostconsiderable biomass, likely because it increased substrate availability for methanogenesis. However, mesocosms where plantbiomass increased had emissions similar to the no-plant control, hence we found no inhibitory effects of plant presence ondiffusive methane emission. We conclude that plant growth in eutrophic, warm conditions varies strongly with plant identity. Ourresults furthermore suggest that plant identity determines whether the replacement of native by non-native freshwater plants willalter ecosystem functions such as regulation of phytoplankton growth and methane emission.

AB - Freshwater plants affect the ecosystem functioning of shallow aquatic ecosystems. However, because native plants are threatenedby environmental change such as eutrophication, global warming and biological invasions, continued ecosystem functioning maybe at risk. In this study, we explored how the growth of native and non-native plant species in eutrophic, warm conditions impactstwo plant ecosystem functions: regulation of phytoplankton growth and methane emission. We expected that plants would inhibitphytoplankton growth, while for methane emission both inhibition and stimulation are possible. We conducted an outdoorexperiment using monocultures of four native and four non-native freshwater plant species planted at three different densities, aswell as a no-plant control. Monocultures of each species were planted in 65 L mesocosms and after three weeks of acclimatisationeach mesocosm was inoculated with phytoplankton. Subsequently, we added nutrients twice a week for eight weeks, beforeharvesting the plant biomass. During these eight weeks, we measured chlorophyll-a concentration thirteen times and the diffusivemethane emissions once after four weeks. The mesocosms amplified the temperature of a warm summer so that plants wereexposed to higher-than-average temperatures. We found that five plant species lost biomass, two species increased their biomassonly at the highest initial plant density (native Myriophyllum spicatum and non-native Lagarosiphon major) and a single speciesincreased 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 biomasschange between native and non-native plants did not relate to overall differences in phytoplankton mass or diffusive methaneemissions. In mesocosms where submerged plant species gained biomass, chlorophyll-a concentration was lower than in the noplantcontrol and mesocosms with biomass loss. Diffusive methane emissions were highest in mesocosms where plants lostconsiderable biomass, likely because it increased substrate availability for methanogenesis. However, mesocosms where plantbiomass increased had emissions similar to the no-plant control, hence we found no inhibitory effects of plant presence ondiffusive methane emission. We conclude that plant growth in eutrophic, warm conditions varies strongly with plant identity. Ourresults furthermore suggest that plant identity determines whether the replacement of native by non-native freshwater plants willalter ecosystem functions such as regulation of phytoplankton growth and methane emission.

KW - NIOO

UR - https://doi.org/10.5061/dryad.6hf6b

U2 - 10.3391/ai.2017.12.3.10

DO - 10.3391/ai.2017.12.3.10

M3 - Article

SN - 1798-6540

VL - 12

SP - 371

EP - 383

JO - Aquatic Invasions

JF - Aquatic Invasions

IS - 3

ER -