Relationship between chlorophyll a concentration, light attenuation and diving depth of the Southern elephant seal Mirounga leonina.
Recently, a number of Antarctic marine environmental studies have used oceanographic parameters collected from instrumented top predators for ecological and physical information. Phytoplankton concentration is generally quantified through active measurement of chlorophyll fluorescence. In this study, light absorption coefficient (K(0.75)) was used as an indicator of phytoplankton concentration. This measurement, easy to obtain and requiring low electric power, allows for assessing of the fine scale horizontal structuring of phytoplankton. As part of this study, Southern elephant seals (SES) were simultaneously equipped with a fluorometer and a light logger. Along the SES tracks, variations in K(0.75) were strongly correlated with chlorophyll, a concentration measured by the fluorometer within the euphotic layer. With regards to SES foraging behaviour, bottom depth of the seal's dive was highly dependent on light intensity at 150 m, indicating that the vertical distribution of SES's prey such as myctophids is tightly related to light level. Therefore, change in phytoplankton concentration may not only have a direct effect on SES's prey abundance but may also determine their vertical accessibility with likely consequences on SES foraging efficiency.
Marine Predator Department, Centre Biologique de Chizé, Villiers en Bois, France. jaud.thomas@gmail.com
Thomas
T
Jaud
Anne-Cécile
AC
Dragon
Jade Vacquie
JV
Garcia
Christophe
C
Guinet
D000818:Animals; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D004242:Diving / Q000502:physiology*; D005260:Female; D008027:Light; D008954:Models, Biological; D046048:Seals, Earless / Q000502:physiology*; D012621:Seasons
D002734:Chlorophyll; D000077194:Chlorophyll A