Spring plankton energy content by size classes in two contrasting environments of a high latitude ecosystem: The Beagle Channel

BRUNO, DANIEL O.; VALENCIA-CARRASCO, CONSTANZA; PACI, MARÍA A.; LEONARDUZZI, EZEQUIEL; CASTRO, LEONARDO; RICCIALDELLI, LUCIANA; IACHETTI, CLARA M.; CADAILLON, ANDREANA; GIESECKE, RICARDO; SCHLOSS, IRENE R.; BERGHOFF, CARLA F.; MARTÍN, JACOBO; DIEZ, MARIANO; CABREIRA, ARIEL; PRESTA, MARÍA L.; CAPITANIO, FABIANA L.; BOY, CLAUDIA C.

JOURNAL OF MARINE SYSTEMS

ELSEVIER SCIENCE BV

Año: 2023

0924-7963

his study aimed to characterise the energy density (ED), using a micro-bombcalorimeter, of different plankton fractions: microplankton (23-67 μm; includingphytoplankton and small heterotrophs), microzooplankton (67-200 μm),mesozooplankton (200-2000 μm), and fish larvae, at two micro-basins separated by asill (the Mackinlay strait) and with different topography and hydrography in the BeagleChannel. For that purpose, two sampling sites (west (F1) and east (F2) of the Mackinlaystrait), two strata (surface and near-bottom layers) and diel variations (diurnal andnocturnal hours) were considered. Also, patterns among plankton fractions’ ED andwater properties (temperature, salinity, total alkalinity, pH, and dissolved inorganiccarbon) were analysed by redundancy analysis. ED values of the plankton fractionsdiffered among sites, strata and sampling time. Surface microplankton at F1 showedhigher ED than at F2. A trend of higher ED values of microzooplankton was observedat the surface than at the near-bottom layer of F1, whereas similar values between bothlayers (surface and near-bottom) were observed at F2. Mesozooplankton was theplankton fraction that most contributed to the site-depth-time of sampling differences inED. For instance, the ED of mesozooplankton was higher at the near-bottom than thesurface layer during diurnal and nocturnal hours of F1, while the opposite was observedfor nocturnal hours at F2. ED of microplankton was associated with conditions of lowervalues of total alkalinity and salinity but higher temperature, whereas microzooplanktonwas associated with the opposite conditions. The ED of mesozooplankton wasassociated with conditions of higher pH and diurnal hours. It is proposed that the energyflow patterns of the plankton community in the Beagle Channel differ in the two micro-basins formed by the MacKinlay strait (east and west of it), with lower and morehomogeneous ED values between fractions and layers east of the strait characterised bydepleted-in-nutrients waters