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Dryad

Variable energy storage and growth in the sea star Pisaster ochraceus

Abstract

The complete data set describes environmentally based variation in size-specific energy storage (dry mass pyloric caeca/dry body mass) and growth of live mass of the intertidal sea star Pisaster ochraceus in British Columbia, Canada. Variation in energy storage and live mass correspond to (1) naturally occurring or (2) experimentally induced changes in the zonation of their prey, the sea mussel Mytilus californianus and associated species. The relevant features of mussel zonation are the depth (vertical distance from a fixed tidal datum) of the lower boundary and the species/size composition of the lower boundary. Downward extensions of the boundaries comprised of masses of relatively young mussels incurred the greatest increases in energy storage and live mass.

Data are presented in 4 files:

(1) Energy storage - Observational study. Variation in energy storage at three sites sampled at irregular intervals from 2008 to 2014. Variables include live mass, dry mass of viscera, and dry mass of the remainder of the body of individual Pisaster ochraceus. Sample dates were chosen to represent natural inter-annual variation in mussel zonation, rather than tracking continuous time courses. 

(2) Storage-boundary depth relationships. Variables derived from observational study and include summary measures of energy storage (slope of the linear regression of dry viscera mass to dry body mass, for dry body masses< 120 g);  boundary depth (vertical distance from tidal datum); and the qualitative composition of the lower boundary.

(3) Energy storage and live mass - Experimental study. Records were made after 1-3 years of experimental manipulation of the mussel boundaries on experimental sites. Variables include initial live mass, final live mass, dry mass of viscera, and dry mass of the remainder of the body of individual Pisaster ochraceus recaptured in the three large-scale replicates of the translocation experiment. 

(4) Boundary depth - Experimental study.  Variables include the type of boundary manipulation, the change in boundary shore levels with respect to conventional tidal data, the resulting composition of the lower boundary, and years of manipulation. 

Further information on-site locations, methods of data acquisition, and definitions of the variables appear in Methods and Usage Notes below.