Temperature and depth profiles recorded during dives of elephant seals reflect distinct ocean environments

The influence of the plankton community structure on carbon dynamics was studied in the surface waters of the Argentinean continental shelf (SW Atlantic Ocean) in summer and fall 2002, 2003 and 2004. The horizontal changes in plankton community respiration (R), net community production (NCP) and gross primary production (GPP) were (1) compared with the difference in the partial pressure of CO 2 (pCO 2 ) between the sea surface and the atmosphere (ΔpCO 2 ), (2) compared with oxygen saturation and (3) related to the microscopic phytoplankton assemblages. This area, which has recently been shown to be a CO 2 sink, had an average surface oxygen saturation of 108.1%, indicating that net photosynthesis could have played a dominant role in the CO 2 dynamics. At most stations, the production:respiration (GPP:R) ratio was greater than 1, indicating that planktonic communities were autotrophic; the average GPP:R ratio for the whole study was 2.99. Phytoplankton biomass (chlorophyll a) and NCP showed an inverse relationship with ΔpCO 2 and a direct relationship with %O 2 saturation when phytoplankton assemblages were dominated by diatoms (30% of the stations). This was not the case when small (≤5 µm) flagellates were the most abundant organisms. Although NCP was mostly positive for both groups of stations (i.e. diatom-dominated or small flagellate-dominated), other physical and biological processes are thought to modify the CO 2 dynamics when small flagellates are the prevailing phytoplankton group.

Section: Introductionmentioning

confidence: 99%

Role of plankton communities in seaair variations in pCO2 in the SW Atlantic Ocean

Schloss¹,

Ferreyra²,

Ferrario³

et al. 2007

“…As a result of this, it has been suggested that marine endotherms, appropriately equipped, could be used to measure and monitor the physical properties of the oceans in which they forage, with specific localities being ascribed specific measurements (e.g. Wilson 1992, 1999, Wilson et al 1993, Weimerskirch et al 1995, Boyd 1997, Campaña et al 2000, Georges et al 2000, Koudil et al 2000. Although this concept is gaining in popularity, there has never been any critical assessment of the features necessary in the technology to make the concept genuinely feasible, nor has the behaviour of marine endotherms been examined in detail to assess what features of their behaviour might prove advantageous for such a purpose.…”

Section: Introductionmentioning

confidence: 99%

Remote-sensing systems and seabirds: their use, abuse and potential for measuring marine environmental variables

Wilson¹,

Grémillet²,

Syder³

et al. 2002

166

115

We examined how seabirds might be used to study marine environmental variables, which necessitates knowing location and the value of the variable to be studied. Five systems can potentially be used for determination of location: VHF (Very High Frequency) telemetry, PTT (Platform Terminal Transmitters) telemetry, GLS (Global Location Service) geolocation methods, dead reckoning and GPS (Global Positioning System), each with its own advantages with respect to accuracy, potential number of fixes and size. Temperature and light were used to illustrate potential difficulties in recording environmental variables. Systems currently used on seabirds for measurement of temperature respond slowly to environmental changes; thus, they may not measure sea surface temperature adequately when contact periods with water bodies are too short. Light can be easily measured for light extinction studies, but sensor orientation plays a large role in determining recorded values. Both problems can be corrected. The foraging behaviour of seabirds was also examined in order to identify those features which would be useful for determination of marine environmental variables at a variety of spatial and temporal scales. Area coverage by birds is highly dependent on breeding phase and tends to be concentrated in areas where prey acquisition is particularly enhanced. The identification of these sites may be of particular interest to marine biologists. 'Plungers' and 'divers' are potentially most useful for assessment of variables deeper within the water column, with some divers spending up to 90% of their time sub-surface. Few seabirds exploit the water column deeper than 20 m, although some divers regularly exceed 50 m (primarily penguins and auks), while 2 species dive in excess of 300 m. The wide-ranging behaviour of seabirds coupled, in many instances, with their substantial body size makes them potentially excellent carriers of sophisticated environmental measuring technology; however, the ethical question of how much the well-being of birds can, and should, be compromised by such an approach needs to be carefully considered.

“…Such studies are now possible because animals can readily carry miniaturised sampling instruments that record both behavioural and environmental parameters (e.g. Wilson et al 1994, Campagna et al 2000, Georges et al 2000, Koudil et al 2000.…”

Section: Introductionmentioning

confidence: 99%

Utilisation of the oceanic habitat by king penguins over the annual cycle

Charrassin¹,

Bost²

2001

127

139

The distribution and behaviour of foraging seabirds depend on the physical features of the ocean at different time and space scales, but little is known for penguins. We investigated the foraging behaviour of king penguins in relation to oceanographic features over the birds' complete annual cycle. A total of 44 birds was followed between 1994 and 1997 at the Crozet Islands to monitor foraging habitat, diving behaviour, and sea temperature of the water column, using satellitetracking and time-temperature-depth recorders (TDR) carried by the birds. The study included breeding in summer, the winter period of chick raising, and the post-moult period in spring. King penguins foraged in 2 specific regions in response to the seasonal changes in local prey availability. In summer, satellite-tracked birds during the incubating and brooding stages (n = 14) preferentially exploited the polar front located 340 to 450 km to the south of their breeding site. TDR-equipped birds (n = 12) also foraged at the polar front in summer as indicated by the vertical temperature profiles. In autumn and winter, satellite tracks (n = 8) and sea temperature measurements of TDRequipped birds (n = 8) showed that birds with crèching chicks instead foraged in antarctic waters, with 70% of individuals reaching the latitude of the pack-ice limit (1600 km from the colony). This suggests better prey availability than in the polar frontal zone at that time. When the birds were at the latitude of the polar front, the thickness of the surface mixed layer (SML) ranged from 80 m in summer to 140 m in winter, the SML temperature was ~4°C and the thermocline had a mean maximum gradient of -0.5°C for each 10 m depth. When the birds were at their most southerly position, the depth of the SML ranged from 100 m in autumn to ~150 m in winter, while its temperature ranged from -0.8 to 2°C. The temperature gradient of the thermocline showed an inversion in autumn, and this gradient was positive in winter (mean maximum gradient of 0.3°C for each 10 m depth). Except for spring birds (n = 4) and for 1 winter bird, where the SML exceeded the diving range, all TDRequipped penguins (n = 19) dived preferentially in and below the depth of the thermocline, thereby minimising diving in the SML. Therefore, their prey may have been predictably concentrated below the SML through oceanographic processes. In king penguins, the strategy of going south could then have evolved in relation to the thinning of the SML towards the south at any time of the year.