11th ICRS Abstract book - Nova Southeastern University
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11th ICRS Abstract book - Nova Southeastern University

11th ICRS Abstract book - Nova Southeastern University 11th ICRS Abstract book - Nova Southeastern University

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Poster Mini-Symposium 4: Coral Reef Organisms as Recorders of Local and Global Environmental Change 4.59 Maracajau Reefs (In Northeastern Brazil) -An Ecosystem Under Severe Thermal Stress Elga MAYAL 1 , Sigrid NEWMANN-LEITAO 2 , Elga MAYAL* 1 1 Zoology, UFPE, Recife, Brazil, 2 Oceonography, UFPE, Recife, Brazil All reefs in which corals grow or grew in Northeastern Brazil have a base of sandstone or sometimes another rock type cropping out of the sea floor. Where corals occur, there is also a great profusion of algae which usually grow on the seaward side of the reef, where the wave action is strong (Laborel,1965). Reefs, thus, are excellent sentinels of the quality of their environment. Proper monitoring of reefs can identify changes in water quality or impacts from land-based activities. Reefs are good environment quality indicators because even the slightest change in hydrology and many anthropogenic impacts may result in community structure changes. This research provides baseline information on the hydrological conditions and on the coral and plankton communities at the Maracajaú reef ecosystem. Studies were performed from February to June 2000, covering the transition from dry to rainy season. In this area, there is an offshore coral reef formation, where corals were observed in loco and water samples were collected to obtain hydrological and plankton data. Six Scleratinians species were identified. Stable isotope analysis on the carbonate fraction of Favia gravida fragments showed that these corals are under severe thermal stress. Chlorophyll-a varied from 1.1mg m-³ to 9.3mg m-³, with higher values during the rainy season. Average zooplankton wet weight biomass were 117.0mg m-³(microzooplankton) and 15.7mg m-³(mesozooplankton). 136 Phytoplankton and 61 zooplankton taxa were identified. Seasonal forcing determined the micro- and mesozooplankton community structure, rather than the coastal offshore gradient. Our results will help to assess anthropogenic disturbances and assist decision-making processes by helping local resource managers to understand the implications of actions associated with particular coral communities. These connections will help in developing management plans for coral reefs and other coastal and marine resources in Brazil. 4.60 Seawater Isotopic Composition Variation in Abrolhos Reef Complex, Brazil Ricardo DOMINGUES* 1 , Alexandre COSTA 2 , Ruy KIKUCHI 3 1 Instituto de Geociências, Universidade Federal da Bahia, Salvador, Brazil, 2 Instituto de Física, Universidade Federal da Bahia, Salvador, Brazil, 3 Geophysics and Geology Research Center, Universidade Federal da Bahia, Salvador, Brazil Coral skeletons provide powerful tools for investigating past environmental conditions of their growth sites, especially information about sea surface temperature (SST). The precise understanding of d18O and d13C in coral skeletons demand that their behavior in seawater is well known as well. The aim of this study was to evaluate isotopic composition of sea water along one year in Abrolhos Reef Complex and contribute to set the basis for the use of stable isotope proxies for temperature in the South Atlantic. From December 2005 to September 2006, water samples were taken in Abrolhos Archipelago twice a month during low tide and high tide. These samples were analyzed in a Delta Plus mass spectrometer, following instructions of the International Atomic Energy Agency (IAEA Guidelines/ Manual for Operation of an Isotope Hydrology Laboratory). Sea water content of d18O varies from 1.5‰ (SMOW) in summer (February) to 1.0‰ (SMOW) in winter-spring (September). This seasonal trend in the sea water isotopic composition for the Abrolhos region may be due to the precipitation/evaporation balance, since the low values of d18O occurred in the rainy season, thus leaving the water lighter. A similar variability occurs with d13C. During fall and winter, its values vary from about 0 to -1.5‰ while during the summer, its value varies from 0.5 to 1.0‰. 4.61 Montastrea cavernosa thermal stress bioindicator in the South Atlantic Elga MAYAL* 1 , Mara FISNER 2 , Alcides SIAL 3 , Valderez FERREIRA 3 , Isabelle SOARES 1 1 UFPE, Recife, Brazil, 2 Oceonography, UFPE, Recife, Brazil, 3 Geology, UFPE, Recife, Brazil We work with species collected from the Atol das Rocas in 1999, and from Tamandaré, south region of Pernambuco, in 2002 and 2003. Some analysis of stable isotopes C and O were done, being as follows: 41 analyses in the Atol das Rocas in 7 specimens; 11 analyses in Tamandaré in 2002 in 2 specimens, and 57 analyses in 2003 in 4 specimens. Both places are units of preservation These 109 analyses have shown that in all these years of collection, with the exception of one specimen in 2003, the temperature registered was higher than 30ºC. The estimated temperatures with values equal or above 30ºC are considered as anomalous in this study. The samples were collected with SCUBA and apnea dives. The samples were washed with tap water and after immersed in a container with hydrogen peroxide 15% during 24 hours. Next, the samples were sliced; micro drilled and collected powders. The powder reacted overnight with orthophosphoric acid and was placed in a high vacuum extraction line. The gas was analyzed in a dual inlet, triple collector mass spectrometer. The C and O isotope ratios are reported on the PDB scale and the temperature was estimated assuming isotope equilibrium, between aragonite and seawater, for each sample, using the Horibe and Oba(1972) equation and d18O‰PDB, and paleosalinity using Craig&Gordon (1965) equation. The isotopic analysis obtained for specimens in Atol das Rocas for the year 1999, presented variations of d13C -0.412 to -1.836‰PDB ; d 18O -4.162 to -4.611 ‰PDB. The analysis obtained for specimens in Tamandaré for the year 2002, presented variations of d13C -3.269 to 2.647‰PDB ; d18O -4.122 to -4.506.‰PDB. In 2003, the isotopic analysis obtained presented variations of d13C -0.363 to -1.617 ‰PDB ; d18O -3.216 to -3.813 ‰PDB. 4.62 Sr/Ca and Mg/Ca Use As Temperature Proxy In A Southwestern Atlantic Endemic Coral Maria Cristina SANTEDICOLA* 1 , Priscila GONÇALVES 1 , Carlos MENDONÇA-FILHO 2 , Ruy KIKUCHI 1 1 Geophysics and Geology Research Center, Universidade Federal da Bahia, Salvador, Brazil, 2 Institute of Geosciences, Universidade Federal da Bahia, s, Brazil The aim of this study is to validate use of Sr/Ca and Mg/Ca ratios in skeletons of Mussismilia braziliensis as geochemical indicators of sea surface temperature (SST) in the Abrolhos reef complex, Eastern Brazil. Upon completion of a 17-sample pilot study to customize the methodology, 393 samples of coral skeleton were cut at every 2mm were cut along the maximum grownth axis of 4 different cores drilled in 2003. Samples were ground, and organic matter eliminated with H2O2. Twenty milligrams of each sample were decomposed by gradually adding 10 mL of HNO3 0,5M, and analyzed with an ICP-OES. The ranges obtained were 203-2260 ppm for Mg and 4553-8194 ppm for Sr. Geochemical ratio averages of 244 samples were compared to average SST nighttime temperature data acquired by the satellite AVHRR Pathfinder Version 5.0 since 1985, considering yearly, half-yearly and quarterly time intervals. A progressive reduction of Sr/Ca ratios at CAB-2 since 1948 may be translated as SST increase. However, a fine adjustment of Sr/Ca and Mg/Ca to temperature variation was not yet possible. We tried a yearly, half-yearly and quarterly resolution comparison between elemental rates and temperature. The best adjustment between SST and Sr/Ca-Mg/Ca was obtained with half-yearly averaged temperature and elemental rates. In addition to comparing pairs of contemporaneous geochemical and temperature data series, a lag of one unit of time was applied in order to investigate possible delayed effects of sea surface temperature over the physiology governing the incorporation of Sr/Ca and Mg/Ca by the coralline skeletons. The application of such lag did not provide significant changes in data plotting for the yearly time interval, but showed an increase in the relationship of temperature and Sr/Ca- Mg/Ca in halfyearly time interval. 277

Poster Mini-Symposium 4: Coral Reef Organisms as Recorders of Local and Global Environmental Change 4.63 Coral Morphology As An Indicator of Sedimentation Rate; Cañada Honda, Dominican Republic Allicia DAVIS* 1 , Dennis HUBBARD 2 1 Dept. of Geological Sciences, Indiana University, Bloomington, IN, 2 Geology Dept., Oberlin College, Oberlin, OH Coral distribution, abundance, and morphology were measured in a subaerially exposed Holocene coral reef in Cañada Honda, which is located in the western Dominican Republic. Four coral facies (branching, mixed, and two distinct massive-coral beds) have been identified. The lowermost massive-coral facies is focused on for this study. The facies is divided into two beds, by a probable storm layer. Six vertical transects were done throughout the two beds with sampling occurring at 20-cm intervals. Twenty corals at each transect were described in terms of morphology, degree of bioerosion, and vertical position within a facies. Samples of typical corals were collected for lab analyses. The lower bed of the facies, M1, is distinguished by the prominence of Montastrea spp., while Siderastrea spp. dominates M2, the higher bed. Differences in colony morphology also distinguish the facies: M1 has more corals with ‘pancake’ morphologies (i.e. draping of successive layers) while M2 shows a more diverse range of shapes, including domes, inverted cones, and ‘pancakes.’ All shapes can be associated with multiple coral species, but Montastrea spp. strongly tends toward the ‘pancake’ morphology. The excellent exposure at Cañada Honda allows for the correlation of growth form with sedimentation rate and degree of bioerosion. Overall, conical forms tend to be more bioeroded, regardless of species or facies. Therefore, they either grew faster or encountered slower sedimentation, resulting in colonies with longer exposure times and more bioerosion. High and variable sedimentation rates lead to periodic swamping of pancake-shaped colonies, which then overgrew the sediment as deposition slowed. Rapid burial led to less bioerosion. Annual growth bands revealed in X-radiographs can be used to quantify this relationship. Comparison of coral growth-rates in various forms may allow for the assignation of absolute values to terms such as “fast” or “slow” with respect to sedimentation in fossil reefs. 4.64 Reconstruction Of Climatic Variability Induced By The Pna Pattern in The Southern Gulf Of Mexico: Geochemical Evidences From Coral Growth Bands Constanza RICAURTE* 1 , Jose CARRIQUIRY 1 , Julio VILLAESCUSA 1 , Guillermo HORTA 2 1 Instituto de Investigaciones Oceanologicas, Universidad Autonoma de Baja California, Ensenada, Mexico, 2 Facultad de Estudios Superiores Iztacala, Universidad Autónoma de México, Mexico D.F., Mexico The climatic conditions of the Gulf of Mexico region are strongly influenced by largescale extra-tropical variability in the atmospheric circulation of, well-known as Pattern Pacífic/North american (PNA) (Slowey and Crowley, 1995). Although coral records have been extensively used to study tropical climatic events as El Niño and the South Oscillation, little has been made to understand the influence of extra-tropical phenomena like PNA on the tropical regions, such as the southern Gulf of Mexico. In this work we show that the rate of skeletal growth and the calcification rate of the coral Montastraea faveolata, collected from the Veracruz Reef System, in Mexico, is influenced by the effects of the PNA, which in turn affects sea surface temperature (which was reconstructed from Sr/Ca and Mg/Ca ratios). The rate of skeletal growth (cm year-1) of the coral Montastrea faveolata increases during the positive phase of the PNA pattern (in winter), characterized by negative anomalies in SST, while the rate of calcification (gr cm-2 year-1) increased during the negative phase of the PNA pattern (in summer) which is characterized by positive anomalies of SST. This means that the corals’ annual growth respond to longer-term (decadal?), extreme variability of SST. The close relationship between the coral growth rate and calcification rate with PNA variability, suggest that corals are not only responding to SST changes, but to broader climatic conditions resulting from atmospheric climate patterns developing in the region. These results also indicate that it is possible to reconstruct the historical variability of the PNA in timescales that exceed those available from instrumental records. 4.65 Enso Variability Recorded in The Growth Rate Of Southwestern-South Atlantic Corals Danielly GODIVA* 1 , Heitor EVANGELISTA 2 , Abdelfettah SIFEDDINE 3 , Zelinda LEÃO 4 , Nivaor RIGOZO 5 , Barbara SEGAL 6 , Tércio AMBRIZZI 7 , Milton KAMPEL 8 , Ruy KIKUCHI 4 1 Geoquímica Ambiental, Universidade Federal Fluminense, Rio de Janeiro, Brazil, 2 Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil, 3 Institut de Recherche pour le Développement, Paris, France, 4 Universidade Federal da Bahia, Salvador, Brazil, 5 FAETEC, São José dos Campos, Brazil, 6 Museu Nacional, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 7 Universidade de São Paulo, São Paulo, Brazil, 8 Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil The knowledge of the effects produced by El Niño Southern Oscillation (ENSO) to marine communities from the Southwestern-South Atlantic (SWSA) is restricted to observations from recent years. To extend these observations back in time, we conducted a study of coral skeleton from the Abrolhos Coral Reef Bank (ACRB), Brazil, and compared them to meteorological and oceanographic parameters in order to better understand the impact of ENSO during past decades. Here, we present an evidence of potential El Niño impacts in the SWSA inferred from the sclerochronology of the massive coral Favia leptophylla. The application of spectral analysis (wavelet decomposition and the iterative regression) to coral growth length and to meteorological-oceanographic parameters (air temperature, sea surface temperature and precipitation) as well as to the Southern Oscillation Index (SOI) and solar irradiation indicated a major significant inverse relationship between SOI and coral growth length in the 4–8 years frequency band. We propose that coral growth rate in the SWSA could be affected by El Niño Southern Oscillation (ENSO) events through an ‘‘atmospheric bridge’’. Although more work is needed to better define the relationship between coral growth rate and the SOI, we found that during El Niño years, southerly cold fronts do not reach the ACRB, reducing the water turbidity and favoring coral growth. 4.66 Sclerochronology And Geochemistry Of Brazilian Corals To Reconstruct Southwestern- South Atlantic Climate Variability Danielly GODIVA* 1 , Heitor EVANGELISTA 2 , Abdelfettah SIFEDDINE 3 , Bruno TURCQ 3 , Thierry CORRÈGE 4 , Nivaor RIGOZO 5 , Ruy KIKUCHI 6 , Zelinda LEÃO 6 , Milton KAMPEL 7 , Renato CAMPELLO 8 1 Geoquímica Ambiental, Universidade Federal Fluminense, Rio de Janeiro, Brazil, 2 Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil, 3 Institut de Recherche pour le Développement, Paris, France, 4 Université Bordeaux 1, Talence, France, 5 FAETEC, São José dos Campos, Brazil, 6 Universidade Federal da Bahia, Salvador, Brazil, 7 Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil, 8 Geoquímica Ambiental, Universidade Federal Fluminense, Niterói, Brazil It has been shown that interannual variations of environmental parameters (e.g. sea surface temperature (SST), salinity, P/E balance and sediment supply) are recorded in the high and low density growth bands of coral skeleton. Here, we investigate the potential of Siderastrea stellata and Favia leptophylla, Southwestern-South Atlantic (SWSA) zooxanthellate corals, as archives of physical and biological changes in the marine environment, induced by oceanic-atmospheric processes. The coral samples were obtained from different Brazilian coastal sites exposed to different environmental and anthropogenic forcing factors. The SST and salinity will be studied through the geochemical composition (stable oxygen, Sr, Ba, Mg, Ca) of coral skeletons. Preliminary sclerochronology studies from X-ray radiographs on corals from Buzios (22º 44’ S 41º 88’ W - 22º 75’ S 41º 53’ W) and Abrolhos (17º 52’ S 39º 14’ W - 18º 01’ S 38º 66’ W) showed a different growth pattern between the two sites. The Abrolhos corals growth present a linear decrease for the past 35 years whereas the Buzios corals seem to have a more stable growth rate despite the fact that they grow in shallower waters and are sometimes exposed during low tides. The Morlet wavelet decomposition and the iterative regression applied to SWSA coral growth band length and to climatic parameters (SST, air temperature, precipitation, Southern Oscillation Index and solar irradiation) indicate growth cyclicities around 2-3 years, 4- 7 years, and a decadal component that seem to correlate with the physical parameters. A more precise sclerochronology study using a digital X-ray apparatus will be conducted, as well as geochemical analyses on specific transects. 278

Poster Mini-Symposium 4: Coral Reef Organisms as Recorders of Local and Global Environmental Change<br />

4.59<br />

Maracajau Reefs (In Northeastern Brazil) -An Ecosystem Under Severe Thermal<br />

Stress<br />

Elga MAYAL 1 , Sigrid NEWMANN-LEITAO 2 , Elga MAYAL* 1<br />

1 Zoology, UFPE, Recife, Brazil, 2 Oceonography, UFPE, Recife, Brazil<br />

All reefs in which corals grow or grew in Northeastern Brazil have a base of sandstone or<br />

sometimes another rock type cropping out of the sea floor. Where corals occur, there is<br />

also a great profusion of algae which usually grow on the seaward side of the reef, where<br />

the wave action is strong (Laborel,1965). Reefs, thus, are excellent sentinels of the<br />

quality of their environment. Proper monitoring of reefs can identify changes in water<br />

quality or impacts from land-based activities. Reefs are good environment quality<br />

indicators because even the slightest change in hydrology and many anthropogenic<br />

impacts may result in community structure changes.<br />

This research provides baseline information on the hydrological conditions and on the<br />

coral and plankton communities at the Maracajaú reef ecosystem. Studies were<br />

performed from February to June 2000, covering the transition from dry to rainy season.<br />

In this area, there is an offshore coral reef formation, where corals were observed in loco<br />

and water samples were collected to obtain hydrological and plankton data. Six<br />

Scleratinians species were identified. Stable isotope analysis on the carbonate fraction of<br />

Favia gravida fragments showed that these corals are under severe thermal stress.<br />

Chlorophyll-a varied from 1.1mg m-³ to 9.3mg m-³, with higher values during the rainy<br />

season. Average zooplankton wet weight biomass were 117.0mg m-³(microzooplankton)<br />

and 15.7mg m-³(mesozooplankton). 136 Phytoplankton and 61 zooplankton taxa were<br />

identified. Seasonal forcing determined the micro- and mesozooplankton community<br />

structure, rather than the coastal offshore gradient.<br />

Our results will help to assess anthropogenic disturbances and assist decision-making<br />

processes by helping local resource managers to understand the implications of actions<br />

associated with particular coral communities. These connections will help in developing<br />

management plans for coral reefs and other coastal and marine resources in Brazil.<br />

4.60<br />

Seawater Isotopic Composition Variation in Abrolhos Reef Complex, Brazil<br />

Ricardo DOMINGUES* 1 , Alexandre COSTA 2 , Ruy KIKUCHI 3<br />

1 Instituto de Geociências, Universidade Federal da Bahia, Salvador, Brazil, 2 Instituto de<br />

Física, Universidade Federal da Bahia, Salvador, Brazil, 3 Geophysics and Geology<br />

Research Center, Universidade Federal da Bahia, Salvador, Brazil<br />

Coral skeletons provide powerful tools for investigating past environmental conditions of<br />

their growth sites, especially information about sea surface temperature (SST). The<br />

precise understanding of d18O and d13C in coral skeletons demand that their behavior in<br />

seawater is well known as well. The aim of this study was to evaluate isotopic<br />

composition of sea water along one year in Abrolhos Reef Complex and contribute to set<br />

the basis for the use of stable isotope proxies for temperature in the South Atlantic. From<br />

December 2005 to September 2006, water samples were taken in Abrolhos Archipelago<br />

twice a month during low tide and high tide. These samples were analyzed in a Delta Plus<br />

mass spectrometer, following instructions of the International Atomic Energy Agency<br />

(IAEA Guidelines/ Manual for Operation of an Isotope Hydrology Laboratory). Sea<br />

water content of d18O varies from 1.5‰ (SMOW) in summer (February) to 1.0‰<br />

(SMOW) in winter-spring (September). This seasonal trend in the sea water isotopic<br />

composition for the Abrolhos region may be due to the precipitation/evaporation balance,<br />

since the low values of d18O occurred in the rainy season, thus leaving the water lighter.<br />

A similar variability occurs with d13C. During fall and winter, its values vary from about<br />

0 to -1.5‰ while during the summer, its value varies from 0.5 to 1.0‰.<br />

4.61<br />

Montastrea cavernosa thermal stress bioindicator in the South Atlantic<br />

Elga MAYAL* 1 , Mara FISNER 2 , Alcides SIAL 3 , Valderez FERREIRA 3 , Isabelle SOARES 1<br />

1 UFPE, Recife, Brazil, 2 Oceonography, UFPE, Recife, Brazil, 3 Geology, UFPE, Recife, Brazil<br />

We work with species collected from the Atol das Rocas in 1999, and from Tamandaré, south<br />

region of Pernambuco, in 2002 and 2003. Some analysis of stable isotopes C and O were done,<br />

being as follows: 41 analyses in the Atol das Rocas in 7 specimens; 11 analyses in Tamandaré<br />

in 2002 in 2 specimens, and 57 analyses in 2003 in 4 specimens. Both places are units of<br />

preservation These 109 analyses have shown that in all these years of collection, with the<br />

exception of one specimen in 2003, the temperature registered was higher than 30ºC. The<br />

estimated temperatures with values equal or above 30ºC are considered as anomalous in this<br />

study.<br />

The samples were collected with SCUBA and apnea dives. The samples were washed with tap<br />

water and after immersed in a container with hydrogen peroxide 15% during 24 hours. Next, the<br />

samples were sliced; micro drilled and collected powders. The powder reacted overnight with<br />

orthophosphoric acid and was placed in a high vacuum extraction line. The gas was analyzed in<br />

a dual inlet, triple collector mass spectrometer. The C and O isotope ratios are reported on the<br />

PDB scale and the temperature was estimated assuming isotope equilibrium, between aragonite<br />

and seawater, for each sample, using the Horibe and Oba(1972) equation and d18O‰PDB, and<br />

paleosalinity using Craig&Gordon (1965) equation.<br />

The isotopic analysis obtained for specimens in Atol das Rocas for the year 1999, presented<br />

variations of d13C -0.412 to -1.836‰PDB ; d 18O -4.162 to -4.611 ‰PDB.<br />

The analysis obtained for specimens in Tamandaré for the year 2002, presented variations of<br />

d13C -3.269 to 2.647‰PDB ; d18O -4.122 to -4.506.‰PDB. In 2003, the isotopic analysis<br />

obtained presented variations of d13C -0.363 to -1.617 ‰PDB ; d18O -3.216 to -3.813<br />

‰PDB.<br />

4.62<br />

Sr/Ca and Mg/Ca Use As Temperature Proxy In A Southwestern Atlantic Endemic Coral<br />

Maria Cristina SANTEDICOLA* 1 , Priscila GONÇALVES 1 , Carlos MENDONÇA-FILHO 2 ,<br />

Ruy KIKUCHI 1<br />

1 Geophysics and Geology Research Center, Universidade Federal da Bahia, Salvador, Brazil,<br />

2 Institute of Geosciences, Universidade Federal da Bahia, s, Brazil<br />

The aim of this study is to validate use of Sr/Ca and Mg/Ca ratios in skeletons of Mussismilia<br />

braziliensis as geochemical indicators of sea surface temperature (SST) in the Abrolhos reef<br />

complex, Eastern Brazil. Upon completion of a 17-sample pilot study to customize the<br />

methodology, 393 samples of coral skeleton were cut at every 2mm were cut along the<br />

maximum grownth axis of 4 different cores drilled in 2003. Samples were ground, and organic<br />

matter eliminated with H2O2. Twenty milligrams of each sample were decomposed by<br />

gradually adding 10 mL of HNO3 0,5M, and analyzed with an ICP-OES. The ranges obtained<br />

were 203-2260 ppm for Mg and 4553-8194 ppm for Sr. Geochemical ratio averages of 244<br />

samples were compared to average SST nighttime temperature data acquired by the satellite<br />

AVHRR Pathfinder Version 5.0 since 1985, considering yearly, half-yearly and quarterly time<br />

intervals. A progressive reduction of Sr/Ca ratios at CAB-2 since 1948 may be translated as<br />

SST increase. However, a fine adjustment of Sr/Ca and Mg/Ca to temperature variation was not<br />

yet possible. We tried a yearly, half-yearly and quarterly resolution comparison between<br />

elemental rates and temperature. The best adjustment between SST and Sr/Ca-Mg/Ca was<br />

obtained with half-yearly averaged temperature and elemental rates. In addition to comparing<br />

pairs of contemporaneous geochemical and temperature data series, a lag of one unit of time<br />

was applied in order to investigate possible delayed effects of sea surface temperature over the<br />

physiology governing the incorporation of Sr/Ca and Mg/Ca by the coralline skeletons. The<br />

application of such lag did not provide significant changes in data plotting for the yearly time<br />

interval, but showed an increase in the relationship of temperature and Sr/Ca- Mg/Ca in halfyearly<br />

time interval.<br />

277

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