Vertical distributions of a planktonic harpacticoid and a calanoid (Copepoda) in a meromictic Antarctic lake

Abstract

Lake Abraxas (68" 29' S., 78' 17' E.) has been cut off from the sea for c. 6000 yr. In December, 1985, it had an ice cover 1.38 m thick, a thermocline at 5.2 m, and zero oxygen at 17.7 m and below. The salinity of the oxylimnion was in the range 14-19 g l-'. The calanoid, Paralabidocera antarctica (I. C. Thompson), had a maximum density just above a thermocline at 5.0 m, at which depth adult males outnumbered females almost 3 : 1. Immediately beneath the ice adult females outnumbered males 4 : 1. Immature copepodite stages were more abundant relative to adults near the oxycline than at higher levels. The planktonic harpacticoid, Amphiascoides sp., had a maximum density close to the oxycline at 17.2 m.

Temporal changes in zooplankton composition in a hypersaline, Antarctic lake subject to periodic seawater incursions

“…P. antarctica occurs in two of these to the total exclusion of all other zooplankton (Bayly & Burton, 1987), and in the other it is dominant over a planktonic harpacticoid (Bayly & Eslake, 1989). It is likely that the apparent intolerance to hypersaline waters exhibited by P. antarctica is also true for Zdomene sp., given that this also disappeared from Lake Fletcher plankton during winter.…”

“…Zooplankton samples were taken from a tidal race, which occasionally connected Lake Fletcher and Taynaya Bay, by streaming a 2 10 pm plankton net for varying periods of time. Vertical distribution of zooplankton within Taynaya Bay was determined using the method described by Bayly (1986) and Bayly and Eslake (1989). Figure 1 shows the location of Lake Fletcher and Taynaya Bay, and their hydrographic relationships, in the Vestfold Hills.…”

Stratified Marine Lakes of Palau (Western Caroline Islands)

“…The marine lakes of Palau are natural steady-state chemostats, permitting one to replicate field measurements of any biological or physical attribute from month to month, year to year, or decade to decade Burnett et al, 1989;Landing et al, 1991;Orem et al, 1991;Hamner, 1995). In the literature on mero mictic lakes, practically every publication extols the virtues of conducting research in simple, small, closed, and stratified aquatic ecosystems (McLaren, 1967a(McLaren, , 1967bBayly and Eslake, 1989). The same is true in the mesocosm literature, where attempts are also made to simplify.…”

“…For example, for the Arctic, Strom (1936) described a series of about 30 poorly ventilated Norwegian fjords, some of which are meromictic, as are many similarly landlocked fjords in North America, in Labrador (Carter, 1965) and on Baf fin Island (McLaren, 1967a(McLaren, , 1967b(McLaren, , 1969. In addition, there are at least 13 mero mictic marine lakes in the Vestfold Hills of Antarctica (Burton and Hamond, 1981;Bayly, 1986;Bayly and Burton, 1987;Bayly and Eslake, 1989). In temperate zones, Oyster Pond is an excellent example of a shallow meromictic kettle lake in the Mashpee Pitted Plain of Cape Cod (Emery, 1969).…”

Paratrochammina Minutissima N. Sp. In Brackish, Marine-Derived Lakes of the Vestfold Hills, East Antarctica

“…The zooplankton of both lakes was dominated by the calanoid copepod Paralabidocera antarctica, accompanied by an unidentified harpacticoid copepod in Abraxas Lake. These species have been recorded in the lakes previously (Bayly and Eslake, 1989;Swadling and others, 2004).…”