https://vital.seals.ac.za/vital/access/manager/Index ${session.getAttribute("locale")} 5 https://vital.seals.ac.za/vital/access/manager/Repository/vital:44790 Wed 27 Oct 2021 14:30:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45023 Wed 22 Jun 2022 15:05:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5665 Wed 21 Jul 2021 13:46:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5797 Wed 16 Feb 2022 10:58:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57006 Wed 09 Nov 2022 09:09:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:26641 Wed 03 May 2023 13:21:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45072 Wed 02 Mar 2022 12:24:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5834 Tue 31 Aug 2021 09:50:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:28390 Tue 27 Jul 2021 16:09:02 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65790 Tue 25 Jul 2023 16:09:04 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5809 Tue 24 Aug 2021 16:43:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5646 Tue 24 Aug 2021 16:36:46 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:19995 Tue 15 Aug 2023 11:32:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:21330 Tue 15 Aug 2023 11:29:32 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:42201 Tue 15 Aug 2023 11:29:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30710 Tue 15 Aug 2023 11:20:55 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5607 Tue 15 Aug 2023 10:51:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:27814 Tue 12 Oct 2021 15:49:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45200 Tue 07 Jun 2022 10:32:47 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45326 Thu 18 Nov 2021 15:47:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57288 Thu 13 Oct 2022 11:49:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:19994 Thu 13 May 2021 14:49:35 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5690 Thu 13 May 2021 14:46:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5670 Thu 13 May 2021 14:21:17 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5829 Thu 13 May 2021 13:43:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5765 50% of total chlorophyll-a at all these stations. Xl Within the IFZ (2 stations), nanophytoplankton dominated total integrated Chl-a biomass (range between 5.6 and 8.8 mg Chi-a. m-2) comprising, on average, 36% of the total. Picophytoplankton comprised an average of 12% of the total Chl-a biomass (range between 3.1 and 5.9 mg Chi-a. m-2) in the MIZ, 36% in the IFZ (range between 6.4 and 7.8 mg Chl-a . m-2) and 20% in the vicinity of the APF (range between 6.8 and 10.6 mg Chi-a. m-2). Total integrated primary production ranged between 316 and 729 mg C . m-2. d-1 at stations occupied in the vicinity of the MIZ, and between 292 and 317 mg C . m·2• d-l within the IFZ. At stations occupied in the region of the APF, total integrated production ranged between 708 and 926 mg C . m-2• dol. The contribution of various size fractions to total productivity generally displayed the same pattern as integrated Chl-a biomass. Microphytoplankton formed the most important contributor to total production at stations occupied in the MIZ and at the APF. Within the IFZ, nanophytoplankton dominated total daily production. Nutrient data suggest that concentrations of macro nutrients within the upper water column were above the threshold where growth would be limited. Preliminary results showed that concentrations of iron (Fe) were highest in the southern region of the MIZ and in the vicinity of the APF. During the second cruise, conducted in the vicinity of the Sub-Antarctic Front (SAF) and in the upstream, inter-island and downstream regions of the Prince Edward Islands, there was evidence of fresh water run-off from the islands, (i.e. decreased salinities and increased concentrations of ammonia and nitrate). Oceanographic data collected at the various production stations indicated that the upper water column was well mixed throughout the survey. Total integrated biomass during the study ranged between 8.5 and 20.1 mg Chi-a. m-2• No distinct patterns in total Chl-a biomass were evident. Picophytoplankton dominated total biomass comprising> 45 % of total pigment at all stations. Nanophytoplankton were the second most important contributor to total integrated biomass. Generally xu microphytoplankton contributed < 10 % of total ChI-a. Total daily integrated production was highest (442.6 mg Chi-a. m-2) at the single station occupied in the vicinity of the SAF. Outside this region, total areal production was lower, ranging from 94.5 to 353.0 mg C . m-2. d-1. With the exception of the station occupied in the vicinity of the SAF, total productivity was dominated by nanophytoplankton, which comprised between 48 and 66% of the total. Concentrations of macronutrients did not appear to be limiting to phytoplankton growth. The absence of a phytoplankton bloom in the vicinity of the islands appears to have been related to water column stability, which was influenced by the prevailing oceanographic regime during the survey. Previous studies have shown that when the SAF lies in close proximity to the islands, advecting forces prevail, resulting in the islands functioning as a flow-through system. During this study, the SAF lay immediately north of the islands. As a consequence no water was trapped in the leeward side of the islands. The results of the two cruises suggest that phytoplankton production in the four systems investigated: the Marginal Ice Zone (MIZ), Antarctic Polar Front (APF), Inter Frontal Zone (IFZ) and Prince Edward Islands (PEl), was largely controlled by water column stability. It is probable that the availability of iron, particularly in the region of the MIZ and APF, may have further contributed to the elevated production recorded in these two regions.]]> Thu 13 May 2021 10:40:35 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5673 Thu 13 May 2021 10:25:25 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5884 Thu 13 May 2021 09:48:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5885 Thu 13 May 2021 09:25:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5642 Thu 13 May 2021 08:50:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5725 Thu 13 May 2021 08:49:43 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5701 Thu 13 May 2021 08:45:56 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5923 Thu 13 May 2021 08:22:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5860 Thu 13 May 2021 08:21:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5736 Thu 13 May 2021 08:19:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5945 Thu 13 May 2021 08:18:49 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5867 Thu 13 May 2021 08:16:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5934 Thu 13 May 2021 08:14:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5815 Thu 13 May 2021 08:14:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5653 2 cm; chaetognaths, medusae, ctenophores and mysids), with particular emphasis on the chaetognaths Eukrohnia hamata and Sagitta gazellae, were investigated during three surveys conducted in late austral summer (April/May) of 2001, 2004 and 2005 in the Polar Frontal Zone in the vicinity of the Prince Edward Islands (46º45’S, 37º50’E), Southern Ocean. The 2001 survey formed part of the Marion Offshore Variability Ecosystem Study (MOVES II), while the 2004 and 2005 surveys formed part of the Dynamics of Eddy Impacts on Marion’s Ecosystem study (DEIMEC III and IV respectively). Macrozooplankton samples were collected using WP-2, RMT-8 and Bongo nets. Results of the hydrographic survey indicated that the region of investigation, the Polar Frontal Zone (PFZ), is an area of high mesoscale variability. During the 2004 survey the Antarctic Polar Front (APF) and the Subantarctic Front (SAF) merged to form an intense frontal feature with subsurface temperature and salinity ranging from 8.5-7.5ºC and 34.15-33.88, respectively. A cyclonic cold core eddy, believed to have been spawned from the APF, was observed during the 2005 survey. Macrozooplankton abundance and biomass ranged from 0 to 43.731 ind. m⁻³, and from 0 to 41.55 mg wwt m⁻³ respectively, during the three surveys. Among the carnivorous macrozooplankton, chaetognaths (Eukrohnia hamata and Sagitta gazellae) were most prominent, contributing up to 85% of the total biomass during all three surveys. Elevated biomass values were found near and within the frontal feature during the 2004 survey, and also along the eddy edge during the 2005 survey. However, hierarchical cluster analysis did not reveal the presence of distinct zooplankton groupings associated with the various water masses encountered during the surveys and this is probably due to the high mesoscale variability in oceanographic conditions that are characteristic of the PFZ. The total average predation impact of the selected carnivorous macrozooplankton during the 2001, 2004 and 2005 surveys accounted for 4.93 ± 6.76%, 0.55 ± 0.51% and 4.88 ± 4.45 of the mesozooplankton standing stock, respectively. S. gazellae had the highest consumption rate in all three surveys, consuming up to 800 g Dwt 1000m⁻³d⁻¹ during the study. Of the two chaetognaths, E. hamata dominated the chaetognath standing stock. The combined abundance and biomass values of E. hamata and S. gazellae ranged from 0 to 43.73 ind. m⁻³ and from 0 to 41.551 mg wwt m⁻³ respectively, during the three surveys. Inter-annual variability in the chaetognath densities was apparent. Highest abundances and biomasses tended to be associated with specific water masses, confirming the existence of a relationship between zooplankton community structure and hydrographic conditions. Generally, about 90% of the chaetognaths contained no food in their guts. S. gazellae consumed a wider variety of prey. Oil droplets occurred in the guts of ≈ 51% of E. hamata. Cannibalism was low in both species, but greater in S. gazellae than E. hamata. During the three surveys, the feeding rate values of E. hamata and S. gazellae went up to 0.48 and 2.099 prey d⁻¹ respectively. S. gazellae also had a greater predation impact on the mesozooplankton standing stock than E. hamata. The mean predation impact of the chaetognaths combined was 0.31 ± 0.291%, 0.52 ± 0.28% and 0.53 ± 0.56% of the mesozooplankton standing stock during the 2001, 2004 and 2005 surveys, respectively. During all three surveys, the majority of individuals (≈ 76%) of the chaetognaths were at stage I maturity, suggesting that during the time of study the chaetognaths were not reproducing. In both species a significant difference (log-linear analysis, p < 0.05) in maturities between the years investigated was observed. In general, there were no differences in lengths and maturities between the different water masses encountered during the surveys. The lengths of E. hamata and S. gazellae ranged from 5 to 24 mm and from 9.4 to 63.6 mm, respectively.]]> Thu 13 May 2021 08:13:35 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5773 Thu 13 May 2021 08:13:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5917 Thu 13 May 2021 08:10:07 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5787 Thu 13 May 2021 08:05:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5832 Thu 13 May 2021 07:35:55 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5781 Thu 13 May 2021 07:26:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5833 Thu 13 May 2021 07:22:04 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5729 Thu 13 May 2021 07:19:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5657 Thu 13 May 2021 07:18:37 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5693 Thu 13 May 2021 07:16:52 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5712 Thu 13 May 2021 07:16:42 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5812 Thu 13 May 2021 07:15:27 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5910 Thu 13 May 2021 07:15:12 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5676 Thu 13 May 2021 07:14:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:28392 Thu 13 May 2021 07:14:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:6036 Thu 13 May 2021 07:14:05 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5767 Thu 13 May 2021 07:13:47 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:30400 Thu 13 May 2021 07:07:53 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5668 Thu 13 May 2021 07:07:20 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5593 Thu 13 May 2021 07:06:29 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:21183 Thu 13 May 2021 07:06:04 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5874 Thu 13 May 2021 07:05:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5735 Thu 13 May 2021 07:03:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:20500 Thu 13 May 2021 07:01:36 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5592 Thu 13 May 2021 06:59:47 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:34163 Thu 13 May 2021 06:59:15 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5639 Thu 13 May 2021 06:57:23 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5696 0.05 in all cases). A key feature of the two investigations was the virtual absence of juveniles (total length < 15 mm) among the amphipod population, supporting the suggestion that they exhibit strong seasonal patterns in reproduction. Gut content analysis during both years indicated that for both the male and female amphipods’, copepods were the most prevalent prey species found in stomachs, followed by chaetognaths and pteropods. Results of electivity studies indicate that T. gaudichaudii is an opportunistic predator, generally feeding on the most abundant mesozooplankton prey. Results of in vitro incubations indicated that the total daily feeding rate of T. gaudichaudii during 2004 ranged from 11.45 to 20.90 ind. m⁻³ d⁻¹, which corresponds to between 0.12 and 1.64% of the total mesozooplankton standing stock. In 2005, the feeding rate ranged between 0.1 and 1.73% of the total mesozooplankton standing stock. The low predation impact of T. gaudichaudii during this study can be related to their low abundances and high interannual variability throughout the region of investigation.]]> Thu 13 May 2021 06:57:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5808 Thu 13 May 2021 06:54:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65375 Thu 11 Jan 2024 18:15:11 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5857 Thu 05 Aug 2021 14:16:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:71935 Thu 04 Apr 2024 19:11:09 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:71933 Thu 04 Apr 2024 19:04:14 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:71926 Thu 04 Apr 2024 16:59:13 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:71925 Thu 04 Apr 2024 16:51:48 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65380 Sun 21 Jan 2024 14:30:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65792 Sun 21 Jan 2024 14:23:44 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:44749 Sun 14 Nov 2021 08:55:46 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45018 Sat 13 Nov 2021 20:08:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:44958 Sat 13 Nov 2021 20:02:02 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:19965 Sat 09 Sep 2023 09:32:33 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:71957 Sat 06 Apr 2024 13:33:28 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:42895 Mon 31 May 2021 10:04:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5745 Mon 30 Aug 2021 14:30:22 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:56789 Mon 26 Sep 2022 11:21:46 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:57239 Mon 24 Oct 2022 16:23:01 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65782 Mon 24 Jul 2023 09:30:24 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:28157 Mon 19 Jul 2021 10:53:40 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45266 Mon 15 Nov 2021 15:27:51 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5656 Mon 12 Jun 2023 15:39:03 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65668 Mon 10 Jul 2023 19:32:30 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65360 Mon 10 Jul 2023 08:48:06 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:50131 Mon 05 Sep 2022 12:59:57 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5734 Mon 05 Jul 2021 09:29:39 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65359 Mon 03 Jul 2023 14:52:08 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:65358 Mon 03 Jul 2023 12:32:02 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:49994 Fri 22 Jul 2022 09:08:31 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:5721 Fri 14 Jan 2022 10:57:18 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:28158 Fri 06 Aug 2021 10:26:50 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45049 Fri 01 Jul 2022 14:30:38 SAST ]]> https://vital.seals.ac.za/vital/access/manager/Repository/vital:45060 Fri 01 Jul 2022 12:49:32 SAST ]]>