LTER meeting 2012

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Changes in zooplankton
phenology at stn MC 1984-2010
Heather Anne Wright
LTER-MC MareChiara meeting
18. October.2012
Changes in zooplankton phenology
Heather.Wright@szn.it

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Part I determine phenology
1. plankton taxa selection (20 zooplankton taxa)
2. exploratory data analysis (EDA)
3. identify trends in seasonal and long term abundance
4. determine phenology
5. significant change in phenology by seasons
Part II determine environmental drivers
1. Select environmental parameters/data
2. Calculate anomalies
3. Correlate phenological timing with anomalies (by year)
Introduction

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Part I: plankton taxa selection
Mazzocchi et al., 2011. Zooplankton
associations in a Mediterranean long-
term time-series. JPR 23: 1163–1181.
Heat map analysis
L. Dubroca 1984:2006
C. Tortora 1984:2010
Discrimination using:
cluster analysis
heat map plots
EDA to explore:
abundance
frequency (omit rare)
season of occurrence
To select taxa:
dominant
ecological role

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Part I: zooplankton taxa selection

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Part I: EDA
Season of occurrence + peak
AMJ spring JAS JFM and OND

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Part I: identify phenology
p=0.0172

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Part I: changes in phenology SPRING taxa
Acartia clausi
∆ phenology 2°
End of season earlier when warmer
JAS_2m vs. 75% *p=0.0388
Centropages typicus
≠ phenology
Trend in 1° NS
End of season earlier when warmer
JAS_int vs. 75% *p=0.0281
Oithona similis
∆ phenology 1°
end of season earlier when warmer
OND_2m vs. 75% *p=0.0399

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Part I: changes in phenology SUMMER taxa
Clausocalanus furcatus
∆ phenology 2°
Phenology delayed and shorter
Duration shorter when warmer
JAS_int vs. Duration **p=0.0014
Peak in September
Paracalanus parvus
≠ phenology
Trend in 1° NS
start of season earlier when warmer
MAM_2m vs. 25% *p=0.0174
Peak in peak in August
start of season driven by temp

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Part I: changes in phenology AUTUMN taxa
Temora stylifera
∆ phenology
End of season earlier
Peak in October
Calocalanus spp.
∆ phenology 2°
Earlier in spring, later in autumn
Bimodal peak in April and Nov
Correlation with JAS_int Temp.
Chaetognaths
∆ phenology 2°
Peak in October
JAS_2m vs. 75%
End of season is later when
summer temp is higher

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Oncaeidae
≠ phenology
No trend in phenology
No correlations with timing vs. Temp
bimodal
appendicularia
≠ phenology
Slight trend in timing vs. Temp
[7:12] vs. OND_2m NS
Removed 1987 and 1998 outliers
bimodal
Cirripedia larvae
≠ phenology
Slight trend in timing vs. Temp
[7:12] vs. JAS_int NS
bimodal
Part I: changes in phenology WINTER taxa

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Summary of results (in progress)
Spring taxa:
End of season is significantly correlated with temperature anomalies in summer and
Autumn. Taxa with a June peak are correlated with JAS (summer) temperature and taxa
with a October peak are correlated with OND (autumn) temperature.
Summer taxa:
Start of season in earlier and duration is shorter when temperature anomalies are above
average. Taxa with an August peak are significantly correlated with spring MAM temp.
Autumn taxa:
End of season is earlier for T.stylifera when temp anomalies are higher, but the end of
season later when warmer for other species. Not a consistent trend in Autumn taxa
Winter taxa:
No significant changes in phenology. All selected winter zooplankton taxa are bimodal.

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Acknowledgements
LTER-MC and MECA – for sampling and data
Grazia Mazzocchi, SZN – director of studies
Adriana Zingone , SZN– internal advisor
Diana Sarno, SZN – phytoplankton taxonomy
Francesca Margiotta, SZN-MECA
Enzo Saggiomo, SZN-MECA
Laurent Dubroca , IFRMER– external collaborator
Cristina Tortora, SZN – post-doc, collaborator

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Part I: example of methods
Part II (1995-2010)
Start *p=0.011
Middle **p=0.006
End *p=0.013
Cumulative percentile method:
start 25% middle 50% end 75%
Timing of central tendency [1:12] or [1:6, 7:12]

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Part II: example of anomalies
What is an anomaly?
The term temperature anomaly means a departure from a reference value or long-
term average. A positive anomaly indicates that the observed temperature was
warmer than the reference value, while a negative anomaly indicates that the
observed temperature was cooler than the reference value.
Reference:
http://www.ncdc.noaa.gov/cmb-faq/anomalies.php

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