1. Sclerochronology: tool for uncovering environmental drivers in a semi-enclosed sea
Melita Peharda1, Ivica Vilibić1*, Tomislav Džoić1, Krešimir Markulin1, Natalija Dunić1, Hrvoje Mihanović1, Miroslav Gačić2, Bryan Black3, Hana Uvanović1, Daria Ezgeta-Balić1, Jadranka Šepić1, Žarko Kovač1, Ivan Župan4
1 Institute of Oceanography and Fisheries, Split, Croatia
2 OGS, Trieste, Italy
3 Marine Science Institute, University of Texas as Austin, Austin, USA
4 University of Zadar, Zadar, Croatia
THEMES Workshop
Venice, Nov 2017

2. What is sclerochronology?
Sclerochronology is analogous to dendrochronology, the study of annual rings in trees, and equally seeks to deduce organismal life history traits as well as to reconstruct records of environmental and climatic change through space and time Sclerochronology is the study of physical and chemical variations in the accretionary hard tissues of organisms, and the temporal context in which they formed
It focuses primarily upon growth patterns reflecting annual, monthly, fortnightly, tidal, daily, and sub-daily increments of time entrained by a host of environmental and astronomical pacemakers
Jones et al. 2007
Arctica islandica
Lack of sclerochronological studies in the Mediterranean!!!
Longevity >500 years
Chronologies >1,300 godina
THEMES Workshop
Venice, Nov 2017

3. Target species?
Three sprecies from genus Glycymeris live in the Adriatic Sea:
G. nummaria
G. bimaculata
G. pilosa
Smallest of three species
Longevity ~ 20 years
Largest of three species, ~ 60 years
Bušelić et al. (2015) – 16 year chronology
G. glycymeris vs. G. pilosa
Purroy et al. (2016)
Other species:
Ezgeta-Balić et al. (2011)
Max longevity 44 years
Very few specimens older than 20 years
Pecten jacobaeus
Callista chione
THEMES Workshop
Venice, Nov 2017

4. to develop a network of bivalve chronologies for the eastern Adriatic
Project: Sclerochronology as a tool for detecting long-term Adriatic environmental changes (SCOOL) Duration: June June 2019 Funder: Croatian Science Foundation Budget: ca. 120 kEuro Principal Investigator: Melita Peharda Uljević Leading institution: Institute of Oceanography and Fisheries
Project objectives:
to develop a network of bivalve chronologies for the eastern Adriatic
to research different basin-scale hydrodynamic and environmental processes that drive the changes of oceanographic properties in the Adriatic Sea
THEMES Workshop
Venice, Nov 2017

5. Bivalve sampling sites
West coast of Istra
Pag Bay
Pašman Channel
Živogošće (Makarska)
Pelješac
South Adriatic
THEMES Workshop
Venice, Nov 2017

6. Laboratory and data analysis
> 50 large shells per species and location
Embeding in epoxy resin
Cutting, grinding and polishing (STRUERS)
Etching – preparation of acetate peels
0.1 M HCl - 2 min, or 0.3 M HCl - 30 sec
Image Pro Premiere – software – image analysis
COFECHA, ARSTAN
THEMES Workshop
Venice, Nov 2017

7. Validation of growth lines
visual cross-dating using – „list year” method
A. May 2012., B. May 2014., C. and April 2015, scale bar 200 µm.
Full circles – wide growth increments, open circles – narrow increments.
THEMES Workshop
Venice, Nov 2017

8. Case study: Glycymeris pilosa, Barbariga, Istra
Bivalve sampling:
Barbariga – 10 m depth, SCUBA
Collection 2015 and 2016
Environmental parameters (monthly values):
ERA Interim: total precipitation (TP), downward net heat flux (NHF), air temperature at 2 m (T2M), sea surface temperature (SST)
NEMOMED12 climate model: sea surface temperature (SSTN), sea surface salinity (SSSN)
Po River discharge at Pontelagoscuro (PO)
Absolute Dynamic Topography (ADT) difference between the centre and the periphery of the Northern Ionian Gyre
THEMES Workshop
Venice, Nov 2017

9. Istra chronology Processed 66 shells, 30 used for chronology
Longevity years
Clear growth lines and synchronized shell growth within population
Earliest measured increment year 1953
Statistically robust (38 years)
Acetate peel of specimen S3P99 (scale bar 500 µm), B. Individual detrended growth series ( ) and their average (1978 statistically robust chronology in black, prior to 1978 in dashed line), C. Sample depth (grey shading area) and EPS values computed in a 30 year window with indicated arbitrary value of EPS value ≥0.85.
THEMES Workshop
Venice, Nov 2017

10. Istra chronology - geochemistry
Peharda et al Chemical Geology, in press
Analysis of stable isotopes indicate periods with low growth and generation of growth lines
For G. Pilosa growth lines are occurring during late summer (September-October)
THEMES Workshop
Venice, Nov 2017

11. Correlations with local freshwater budget
90%
95%
Correlations with local freshwater budget
Correlations were not significant between chronologies and monthly water budget variables (TP and PO) in the year of growth (October-September) and preceeding 6 months
Local freshwater inputs (including nutrient inputs) are not significantly influencing growth rates.
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Correlation
90%
95%

12. Correlations with local temperatures
90%
95%
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Correlations were significant with winter (February-March) and summer (June-September) sea surface temperatures (both SST and SSTN)
The higher are winter temperatures the higher is the bivalve growth
The higher are summer temperatures the lower is the bivalve growth (due to a stress to the organism)
THEMES Workshop
Venice, Nov 2017

13. Correlations with remote forcing (i.e. BiOS)
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Correlation
90%
95%
Correlations were significant with winter (October- February) ADT
The stronger is the cyclonic BiOS (i.e. higher inflow of high-saline waters from the Levantine Basin) the weaker is the bivalve growth
ADT (Oct-Feb)
THEMES Workshop
Venice, Nov 2017

14. Ongoing activities Glycymeris sp.
Preliminary analysis of fossil samples – estimated longevity >100 years
14C analysis in process
Possibilities for EXTENDING CHRONOLOGIES back in time (>50 years) and/or constructing floating chronologies?
THEMES Workshop
Venice, Nov 2017

15. Plans for future Extending chronology - analysis of fossil samples
Construction of chronologies for multiple locations – other parts of the Mediterranean
Construction of multi-species chronologies
Chronologies for commercially important species
Geochemical analysis of shells – stable isotopes (δ18O i δ13C) and elements (Mo, Ba, Li)
Correlating basin-wide (Adriatic, Mediterranean) chronologies to global, regional and local climate and environmental indices and processes
THEMES Workshop
Venice, Nov 2017

16. Split, Croatia, 17-20 June 2019 Sessions
Climate and Oceans: Past, Present and Future
Proxy Development: Challenges and Opportunities
Growth, Bioenergetics and Ecosystems
Sclerochronology and Human-Environmental Interactions: Past and Present
Fisheries Ecology and Management
Paleoecology and Evolution
Environmental Biomonitoring & Entrepreneurship