Diel feeding rhythm of copepod size-fractions from Coliumo Bay, Central Chile

Abstract

SUMMARY: The feeding behaviour of the size fractionated copepod assemblage was studied over a diel cycle in Coliumo Bay. In this shallow environment the photic layer reached the bottom and salinity, temperature, and food availability were fairly homogeneous throughout the water column. All four size-fractions (250-500 µm, 500-1000 µm, 1000-2000 µm, >2000 µm) showed a period of high feeding activity during the night and low feeding activity during the day. The persistence of nocturnal feeding in the presence of high food concentration over the 24-h cycle is interpreted as a predator avoidance strategy: empty guts by day make copepods less conspicuous to their visual daytime predators.

Tetraselmis jejuensis sp. nov. (Chlorodendrophyceae), a Euryhaline Microalga Found in Supralittoral Tide Pools at Jeju Island, Korea

“…Further investigation of the similarity between these cells and three Chilean strains of Tetraselmis reported by Gonzalez et al [45] revealed that the ultrastructural arrangement of T. jejuensis is similar to that of the Dichato strain, despite the structures of the pyrenoid matrix differing. Although the environmental data for Coliumo Bay, where Dichato is located, was not provided at the time, we confirmed that the salinity of Coliumo Bay was approximately 1.36%, measured at depths ranging from 2 m to 5 m in November 1996 [50]. The finding that these cells proliferate vigorously at salt concentrations lower than 2.0% corresponds to the physiological characteristic of T. jejuensis surviving in extreme salt concentrations ranging from 0.3% to 1.6% (Table 3).…”

“…The fixed cells were collected on 3 µm pore size polycarbonate membrane filters (Whatman, Kent, UK) and washed thrice with 50% filtered seawater diluted with distilled water to remove residual salts. The membranes with attached cells were dehydrated in an ethanol series (10,30,50,70,90, and 100% ethanol, followed by two changes in 100% ethanol (Merck, Darmstadt, Germany), and were immediately dried using an automated critical point dryer (EM CPD300, Leica, Wetzlar, Germany). The dried filters were mounted on an aluminum stub (Electron Microscopy Sciences, Hatfield, PA, USA) using copper conductive double-sided tape (Ted Pella, Redding, CA, USA), and coated with gold using an ion sputter (MC1000, Hitachi, Tokyo, Japan).…”

Reproductive performance of small-sized dominant copepods with a highly variable food resource in the coastal upwelling system off the Chilean Humboldt Current

“…Acartia, Centropages and Paracalanus copepod species may be significant links for channelling primary production to higher trophic levels in the upwelling zone ecosystem (Calliari & Antezana 2001;González et al 2002;Vargas et al 2006Vargas et al , 2007. All these studies have stressed the relevance of small copepods feeding on the full food size-spectrum and transferring C through the microbial loop (González et al 2002;Vargas et al 2006Vargas et al , 2007.…”

“…In tropical zones, small-sized copepods have also been reported as mainly feeding upon food items smaller than diatoms (Calbet et al 2000). Because of their high and sustained production Acartia, Centropages and Paracalanus species may thus be relevant links to channel primary production (PP) to higher trophic levels in this ecosystem as suggested by Calliari & Antezana (2001), González et al (2002), and Vargas et al (2006. All these authors studied the distribution, secondary production and the relevance of feeding by these small-sized copepods preying on the complete food size-spectrum, as well as seasonal variability of feeding activity.…”

“…All these authors studied the distribution, secondary production and the relevance of feeding by these small-sized copepods preying on the complete food size-spectrum, as well as seasonal variability of feeding activity. They concluded that small species can be widely distributed along the Chilean coast (Calliari & Antezana 2001), and that the microbial loop mediated by copepod feeding may represent an important pathway for PP to move through trophic levels in the upwelling systems (González et al 2002;Vargas et al 2006Vargas et al , 2007.…”