No abstract

Abstract. 1. Capture efficiency was determined chiefly by insect type: Diptera 79–98%, Hymenoptera 60–83%, Homoptera 32–76%, Thysanoptera 27–62%, Acarina 12–40%.2. Grass length also affected efficiency, but to a lesser degree.3. Prolongation of the sampling period increased the proportions of some groups more than others.4. Capture efficiency for any group was not affected by the number of individuals present.5. Catch size did not vary with time of day.6. The method was unsatisfactory for wet grass.

During winter (1973), a very pure natural population of the diatom Navicula glaciei Van Heurck occurred in dense concentrations (up to 244 mg·m−2 chlorophyll a) in the sea ice at Signy Island, South Orkneys, Antarctica. Samples of algal material were collected for subsequent chemical analysis. The diatom had a composition of 33.77% ash, 21.81% lipid, 25.38% crude, protein, 19.04% crude carbohydrate and an intact calorific value of 15.384 KJ·g−1. Carbon, hydrogen, nitrogen and phosphorus formed 34, 5.3, 4.1 and 0.52% dry wt respectively. The material was analysed for the trace elements Na, K, Fe, Ca, Mg, Al, Zn, Cu, Pb, Mn, 137Cs. Fatty acid composition was dominated by 16:0 palmitic acid (20.46%), 16:1 palmitoleic acid (32.86%), and 20:5 docosahexaenoic acid (19.33%). To supplement a very scanty original description, a full taxonomic description is given in the text.

Marine planktonic primary production was studied in Borge Bay, Signy Island, the Antarctic, during the period January 1972–February 1974. Productivity was measured in situ by the radiocarbon uptake method. In 1972–1973 and 1973–1974, respectively, 86 and 289 gC m -2 a -1 was fixed in 16.5 m of water. The seasonal production cycle consisted of a rapid increase of a diatom standing crop dominated by Thalassiosira antarctica Comber, to a peak crop of 0.381 -1 m -2 standing cell volume, 605 mg chl a m -2 and 23.5 gC m -2 , by the first week of January. Mid-summer productivity was high, 4.8 gC m -2 d -1 being fixed on occasion but specific fixation rates were relatively low (maximum 1.12 mgC mg -1 chl a h -1 ). In late February the standing crop declined abruptly and during the winter period productivity and standing crop was small. Productivity and standing crop was greatly influenced by light climate and water stability.