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Responses of phyto- and zooplankton communities to Prymnesium polylepis (Prymnesiales) bloom in the Baltic Sea.

Gorokhova E, Hajdu S, Larsson U - PLoS ONE (2014)

Bottom Line: The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008.Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA:DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton.Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden.

ABSTRACT
A large bloom of Prymnesium polylepis occurred in the Baltic Sea during the winter 2007-spring 2008. Based on numerous reports of strong allelopathic effects on phytoplankton exerted by P. polylepis and its toxicity to grazers, we hypothesized that during this period negative correlations will be observed between P. polylepis and (1) main phytoplankton groups contributing to the spring bloom (i.e., diatoms and dinoflagellates), and (2) zooplankton growth and abundance. To test these hypotheses, we analyzed inter-annual variability in phytoplankton and zooplankton dynamics as well as growth indices (RNA:DNA ratio) in dominant zooplankton in relation to the Prymnesium abundance and biomass. Contrary to the hypothesized relationships, no measurable negative responses to P. polylepis were observed for either the total phytoplankton stocks or the zooplankton community. The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008. Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA:DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton. Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce.

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Dynamics of RNA∶DNA ratio (monthly mean ± SD, n varies from 5 to 12) in the copepods Acartia spp. and rotifers Keratella quadrata (left axis) in relation to the total phytoplankton (TPhyto) and Prymnesium polylepis (biovolume, right axis) during 2007 and 2008; stn BY31, B1 and H4 in the northern Baltic proper.Note that main peaks for TPhyto at stn H4 are outside the axis limits.
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pone-0112985-g005: Dynamics of RNA∶DNA ratio (monthly mean ± SD, n varies from 5 to 12) in the copepods Acartia spp. and rotifers Keratella quadrata (left axis) in relation to the total phytoplankton (TPhyto) and Prymnesium polylepis (biovolume, right axis) during 2007 and 2008; stn BY31, B1 and H4 in the northern Baltic proper.Note that main peaks for TPhyto at stn H4 are outside the axis limits.

Mentions: During the study period, RNA∶DNA ratios ranged from 1.4 (stn B1, 2007) to 6.7 (stn B1, 2008) in Acartia spp., and from 1.9 (stn B1, 2007) to 7.6 (stn BY31, 2008) in Keratella quadrata, generally increasing with increased phytoplankton stocks (Figure 5). For each taxa-specific GLM with RNA∶DNA ratio as a response variable and year, station, and season as explanatory variables, a significant season×year interaction effect was observed (Acartia: Wald stat = 10.81, p<0.001; Keratella: Wald stat = 5.79, p<0.016). Hence, it was followed up by the season-specific models to test effects of station and year. In winter-spring, RNA∶DNA ratios in both species were significantly higher in 2008 compared to 2007 (Acartia: Wald stat = 41.18, p<0.0001; Keratella: Wald stat = 13.97, p<0.001) and the effect was consistent for all stations. In summer-autumn, there was a significant station×year interaction effect for RNA∶DNA ratio in Acartia (F = 3.86, p<0.026), with significantly higher ratios in 2008 than in 2007 observed at stn B1 (Wald stat = 20.63, p<0.0001) but not at the other stations (p>0.05 in both cases). No significant effects were observed for RNA∶DNA ratios in Keratella for the summer-autumn period (p>0.4 in all cases).


Responses of phyto- and zooplankton communities to Prymnesium polylepis (Prymnesiales) bloom in the Baltic Sea.

Gorokhova E, Hajdu S, Larsson U - PLoS ONE (2014)

Dynamics of RNA∶DNA ratio (monthly mean ± SD, n varies from 5 to 12) in the copepods Acartia spp. and rotifers Keratella quadrata (left axis) in relation to the total phytoplankton (TPhyto) and Prymnesium polylepis (biovolume, right axis) during 2007 and 2008; stn BY31, B1 and H4 in the northern Baltic proper.Note that main peaks for TPhyto at stn H4 are outside the axis limits.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231118&req=5

pone-0112985-g005: Dynamics of RNA∶DNA ratio (monthly mean ± SD, n varies from 5 to 12) in the copepods Acartia spp. and rotifers Keratella quadrata (left axis) in relation to the total phytoplankton (TPhyto) and Prymnesium polylepis (biovolume, right axis) during 2007 and 2008; stn BY31, B1 and H4 in the northern Baltic proper.Note that main peaks for TPhyto at stn H4 are outside the axis limits.
Mentions: During the study period, RNA∶DNA ratios ranged from 1.4 (stn B1, 2007) to 6.7 (stn B1, 2008) in Acartia spp., and from 1.9 (stn B1, 2007) to 7.6 (stn BY31, 2008) in Keratella quadrata, generally increasing with increased phytoplankton stocks (Figure 5). For each taxa-specific GLM with RNA∶DNA ratio as a response variable and year, station, and season as explanatory variables, a significant season×year interaction effect was observed (Acartia: Wald stat = 10.81, p<0.001; Keratella: Wald stat = 5.79, p<0.016). Hence, it was followed up by the season-specific models to test effects of station and year. In winter-spring, RNA∶DNA ratios in both species were significantly higher in 2008 compared to 2007 (Acartia: Wald stat = 41.18, p<0.0001; Keratella: Wald stat = 13.97, p<0.001) and the effect was consistent for all stations. In summer-autumn, there was a significant station×year interaction effect for RNA∶DNA ratio in Acartia (F = 3.86, p<0.026), with significantly higher ratios in 2008 than in 2007 observed at stn B1 (Wald stat = 20.63, p<0.0001) but not at the other stations (p>0.05 in both cases). No significant effects were observed for RNA∶DNA ratios in Keratella for the summer-autumn period (p>0.4 in all cases).

Bottom Line: The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008.Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA:DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton.Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce.

View Article: PubMed Central - PubMed

Affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden; Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden.

ABSTRACT
A large bloom of Prymnesium polylepis occurred in the Baltic Sea during the winter 2007-spring 2008. Based on numerous reports of strong allelopathic effects on phytoplankton exerted by P. polylepis and its toxicity to grazers, we hypothesized that during this period negative correlations will be observed between P. polylepis and (1) main phytoplankton groups contributing to the spring bloom (i.e., diatoms and dinoflagellates), and (2) zooplankton growth and abundance. To test these hypotheses, we analyzed inter-annual variability in phytoplankton and zooplankton dynamics as well as growth indices (RNA:DNA ratio) in dominant zooplankton in relation to the Prymnesium abundance and biomass. Contrary to the hypothesized relationships, no measurable negative responses to P. polylepis were observed for either the total phytoplankton stocks or the zooplankton community. The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008. Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA:DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton. Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce.

Show MeSH
Related in: MedlinePlus