Biogeochemical tracers found in the hard parts of organisms are frequently used to answer key ecological questions by linking the organism with the environment. However, the biogeochemical relationship between the environment and the biogenic structure becomes less predictable in higher organisms as physiological processes become more complex. Here, we use the simultaneous combination of biogeochemical tracers and fish growth analyzed with a novel modeling framework to describe physiological and environmental controls on otolith chemistry in an upwelling zone. First, we develop increasingly complex univariate mixed models to describe and partition intrinsic (age effects) and extrinsic (environmental parameters) factors influencing fish growth and otolith element concentrations through time. Second, we use a multivariate mixed model to investigate the directionality and strength between element-to-element and growth relationships and test hypotheses regarding physiological and environmental controls on element assimilation in otoliths. We apply these models to continuous element (Na, Sr, Mg, Ba, Li) and growth increment profiles (monthly resolution over 17 years) derived from otoliths of reef ocean perch (Helicolenus percoides), a wild-caught, site-attached, fully marine fish. With a conceptual model, we hypothesize that otolith traits (elements and growth) driven by environmental conditions will correlate both within an otolith, reflecting the time dependency of growth and element assimilation, and among individuals that experience a similar set of external conditions. We found some elements (Sr:Ca and Na:Ca) are mainly controlled by physiological processes, while other elements (Ba:Ca and Li:Ca) are more environmentally influenced. Within an individual fish, the strength and direction of correlation varies among otolith traits, particularly those under environmental control. Correlations among physiologically regulated elements tend to be stronger than those primarily controlled by environmental drivers. Surprisingly, only Ba:Ca and growth are significantly correlated among individuals. Failure to appropriately account for intrinsic effects (e.g. age) led to inflated estimates of among individual correlations and a depression of within individual correlations. Together, the lack of among-individual correlations of otolith traits in properly formulated models and the biases that can be introduced by not including appropriate intrinsic covariates suggest that caution is needed when assuming multi-elemental signatures are reflective solely of shared environments.
Sr:Ca data
Strontium trace element data (Sr:Ca) from ocean perch otoliths for each discrete monthly time period extracted from laser ablation ICP-MS data. These data are used in the univariate mixed modeling analysis for the response variable of Sr:Ca. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. SrCa: value of the Sr:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
SrCadata.txt
Na:Ca data
Sodium trace element data (Na:Ca) from ocean perch otoliths for each discrete monthly time period extracted from laser ablation ICP-MS data. These data are used in the univariate mixed modeling analysis for the response variable of Na:Ca. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. NaCa: value of the Na:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
NaCadata.txt
Mg:Ca data
Magnesium trace element data (Mg:Ca) from ocean perch otoliths for each discrete monthly time period extracted from laser ablation ICP-MS data. These data are used in the univariate mixed modeling analysis for the response variable of Mg:Ca. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. MgCa: value of the Mg:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
MgCadata.txt
Ba:Ca data
Barium trace element data (Ba:Ca) from ocean perch otoliths for each discrete monthly time period extracted from laser ablation ICP-MS data. These data are used in the univariate mixed modeling analysis for the response variable of Ba:Ca. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. BaCa: value of the Ba:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
BaCadata.txt
Li:Ca data
Lithium trace element data (Li:Ca) from ocean perch otoliths for each discrete monthly time period extracted from laser ablation ICP-MS data. These data are used in the univariate mixed modeling analysis for the response variable of Li:Ca. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. LiCa: value of the Li:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
LiCadata.txt
Growth increment data
Growth increment measurements from ocean perch otoliths for each discrete monthly time period. These data are used in the univariate mixed modeling analysis for the response variable of Growth. IDCode: unique identifier for each fish. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. Growth: measured value of the growth increment for a discrete monthly time period (μm). Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
growthdata.txt
Environmental data
Environmental (extrinsic) variables used in the univariate mixed modeling analyses to partition monthly variation of the response variables (Na:Ca, Sr:Ca, Mg:Ca, Ba:Ca, Li:Ca or Growth) between intrinsic and extrinsic drivers. Month: A code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). BonneyUI: Monthly upwelling index for the Bonney Coast region of southern Australia (See Figure 2 and Table 1 for details). BottomTemp: monthly mean bottom temperature (C) for Bonney upwelling region (See Table 1 for details). Chl-a: levels of chlorophyll a (mg/m3) in the Bonney upwelling region (See Table 1 for details).
AllEnviData.csv
Data for all response variables
Data for all response variables (Na:Ca, Sr:Ca, Mg:Ca, Ba:Ca, Li:Ca and Growth) collected from ocean perch otoliths for each discrete monthly time period. Element:Ca data are extracted from laser ablation ICP-MS data and Growth data are growth increment measurements. These data are used in the multivariate mixed modeling analysis to estimate within and among individual correlations. Age.years.cap: age of the fish in years at date of capture. Age.month.cap: age of the fish in months at date of capture. Month.code.cap: month code for the date of capture, e.g. 75 = Dec 1996. FishID: = IDCode. Growth: measured value of the growth increment for a discrete monthly time period (μm). NaCa, SrCa, MgCa, BaCa, or LiCa: value of the Element:Ca ratio for that discrete monthly time period (μmol/mol) extracted from the laser ablation ICP-MS data. Month: a code designating the specific month and year of each monthly resolved increment (i.e. 75 = Dec 1996, 76 = Jan 1997, etc.). Age: age when each monthly increment was formed (total months). fMonth = Month (as factor).
alldata.csv