Has zooplankton 24 hour vertical distribution pattern in Lough Derg (Ireland) been changed over the period of ∼90 years?

• Published in: Oceanological and Hydrobiological Studies
• Main Authors: Pociecha, Agnieszka, McCarthy, Thomas
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Walter de Gruyter GmbH 2011
• Subjects: Oceanography; Copepods; Rotifer
• Online Access: http://dx.doi.org/10.2478/s13545-011-0026-3

Abstract The vertical distribution of zooplankton was examined in Lough Derg, Ireland. Zooplankton was collected at one location every 2 m from the surface to the bottom during 24 hours at four-hour intervals. Zooplankton was identified to the species level and its density was calculated for each taxon, depth and hour. We recorded 9 rotifer, 3 copepod, and 4 cladoceran species. The highest total zooplankton density (rotifers, copepods, cladocerans, mysids and zebra mussel larvae) was recorded at 3 a.m. Rotifers preferred mainly a depth from 0 to 8 m, while copepods and cladocerans were observed within the whole water column during a 24 hour observation. It was a different pattern of diurnal migration than that Southern and Gardiner (1932) received, though they didn’t study rotifers. Probably food concentration and/or predators, or other environmental factors could influence the diel vertical migration of zooplankton from Loug Derg.