LTER meeting February 2013

LTER-MC meeting 15 Feb 2013
Thesis: Long-term variability of plankton
phenology in a Mediterranean time
series (LTER-MC)
Phenology in plankton
Main results from methods applied
Patterns observed to date
Final analysis
Acartia clausi
Emiliania huxleyi
Minidiscus comicus
Chaetoceros socialis
1

Part I species selection
• community structure analysis
• Initial selection 46 species
Part II results
• Significant changes in phenology
• Relationships with temperature
2

Zooplankton n=111 categories
1. Calanoid juveniles ( juv of Clausocalanus
spp.+P.parvus)
2. Penilia avirostris
3. (bulk) appendicularia
4. Acartia clausi
5. Paracalanus parvus (only adults)
Phytoplankton n=344 categories
1. (bulk undetermined )
Undetermined phytoflagellates
<10m size
2. (genus level) Chaetoceros spp.
3. Chaetoceros tenuissimus
4. Skeletonema pseudocostatum
5. Leptocylindrus danicus
Plankton community structure
RAD curves
3

LTER-MC meeting 15 Feb 2013 4
Plankton community structure
Frequency distribution curves
Phytoplankton
168 categories occur with a
frequency of <1%
This class is discarded from
consideration since the data is too
sparse
Zooplankton
Only 14 out of categories <1%
frequency

Initial selection
n=46 species, genus level and groups

Part II results

Significant changes in phenology: phytoplankton

Chaetoceros socialis
Spring colonial diatom with peak in April
- April peak increased in second part of
time series
- Start and middle phases of phenology
are significantly later
- End of phenology did not have a
significant change
- Timing of peak was significantly later
Significant changes in phenology

Dinobryon faculiferum
Spring flagellate with peak abundance in
March continuing through August
- Decrease in late summer abundance
after 1995
- The start of season phenophase was
significantly later after 1995
- The duration was significantly shorter
after 1995

Heterocapsa niei
Spring dinoflagellate with a peak in May
- Start and middle of season are
significantly later
- Duration is longer in part II of t.s.
- Timing is earlier after 1995

Skeletonema pseudocostatum
Spring diatom with a peak in July (part I)
which has shifted to May in Part II
- Timing is later in part I of time series
- Timing is earlier in part Ii of t.s. But not
significant

Minidiscus comicus
Summer diatom with a peak in
September (part I) and August (part II
- Timing after 1995 is significantly
earlier in all phenophases

Chaetoceros tenuissimus
Bimodal diatom with a primary peak
in spring and secondary in autumn
Peak in May (part I) shifted to June in
part II
- Start of season significantly later
after 1995 (this phenophase
corresponds to the later mean
seasonal abundance cycle)
- Timing [1:6] later in part I
- Timing [7:12} earlier after 1995

Skeletonema menzelii
Bimodal diatom with summer peak in
August and autumn peak in October
- The end was significantly earlier after
1995
- The timing was also significantly
earlier after 1995

Significant changes in phenology: zooplankton

Significant changes in phenology: phytoplankton

• Most species did not change phenology over long term !
• Four phytoplankton species that occur during the spring season changed
• The start of season and timing was later
• Phenology of D.faculiferum restricted, H.niei enlarged (duration)
• Spring and autumn zooplankton species showed significant change
• A.clausi, C.typicus, O.similis, C.paululus had earlier phenology
• Summer zooplankton had a stable phenology over the long term
• P.parvus, Evadne+Pseudoevadne, P.avirostris
• Changes observed in bulk assemblages could be attributed to species
level changes in phenology of target species

Part II results

Relationships with temperature
phytoplankton
Species that had significant changes in phenology also had significant
relationships with temperature anomalies within each season

phytoplankton

zooplankton

Significant relationships with temperatures
• spring phytoplankton and zooplankton species had strong relationships
with temperature
• The timing of bimodal species was later when warmer
• S.menzelii, S.pseudocostatum
• Spring zooplankton species phenology was earlier when temperature
anomalies were higher
• A.clausi,C.typicus, O.similis, C.paululus (as for ∆ phenology)
• End of season phenology and seasonal temperature
• 2 species within the zooplankton genera Oithona and Clausocalanus had
significant relationships with temperature anomalies in different seasons

Part II results
Final analysis

Final analysis
Community assembly

Final analysis
- Consideration of more than 46 species
- Expand to all taxa > 1% frequency of occurrence
- Correlation with other environmental parameters
- Salinity
- Heat flux
- Light
- Chl a
- nutrients

LTER meeting February 2013

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