Temporal and spatial changes in body size and reproductive state of Nannocalanus minor (Copepoda) females across and along the Gulf Stream

The temporal and spatial trends of cephalothorax length andreproductive state of adult females of the cosmopolitan copepodspecies Nannocalanus minor are described across the Gulf Streamnear Cape Hatteras. NC. Consistent regional differences anda cross-stream gradient in size were found, with the largestanimals in the Slope Water, animals of intermediate size inthe Gulf Stream and the smallest animals in the Sargasso Sea.Distinct seasonal patterns in size were observed within eachcross-stream region (Slope Water, Gulf Stream and Sargasso Sea)and these patterns followed seasonal changes in environmentalconditions (temperature and sea surface pigment concentration).Body sizes of the Slope Water animals were inversely and linearlyrelated to temperature with no clear relationship to sea surfacepigment concentration, while body sizes of the Sargasso Seaanimals were correlated with pigment concentration (asymptotic,non-linear relationship) with no relationship to temperature.The lack of consistent regional and seasonal trends in reproductivestate suggested that continuous reproduction was a life historytrait for adults of this species. The potential effect of short-term,episodic events on the size distribution and reproductive stateof this species was investigated across and along a Gulf Streammeander during the BIOSYNOP project in 1988. Upwelling of nutrientsmay occur on the trailing flank of a meander, with enhancedprimary and, possibly, secondary production occurring downstreamin the leading flank of the meander. No specific meander effectwas observed for body size. More individuals were reproducingdownstream of the upwelling region, suggesting a response tothe enhanced primary production characteristic of the upwellingregion.