BIANZO: biodiversity of three representative groups of the Antarctic Zoobenthos: comparative structure, distribution and fucntion

Report (2007)

Biology of Posidonia

in Larkum, Anthony WD; Orth, Robert J; Duarte, Carlos M (Eds.) Seagrasses: Biology, Ecology and Conservation (2006)

The aim of this chapter is to place emphasis on the dynamics of Posidonia systems in order to detect key ecosystem processes and to put in evidence the large differences between the Mediterranean and ... [more ▼]

The aim of this chapter is to place emphasis on the dynamics of Posidonia systems in order to detect key ecosystem processes and to put in evidence the large differences between the Mediterranean and Australian systems. These key processes shall be the basis to formulate new working hypothesis in order to verify newly emerging concepts and propose management plans in order to ensure the sustainability of the system. [less ▲]

Applications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems

in Marine Pollution Bulletin (2004), 49(11-12), 887-891

Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators ... [more ▼]

Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

Contributions of benthic and planktonic primary producers to nitrate and ammonium uptake fluxes in a nutrient-poor shallow coastal area (Corsica, NW Mediterranean)

in Journal of Experimental Marine Biology and Ecology (2004), 302(1), 107-122

By using the stable isotope N-15, we have measured in situ the uptake of nitrate and ammonium by the seagrass Posidonia oceanica, its leaf epiphyte community, the brown macroalgae Halopteris scoparia and ... [more ▼]

By using the stable isotope N-15, we have measured in situ the uptake of nitrate and ammonium by the seagrass Posidonia oceanica, its leaf epiphyte community, the brown macroalgae Halopteris scoparia and the suspended particulate organic matter (SPOM). In Revellata Bay (Gulf of Calvi, Westem Corsica), which is a very nutrient-poor region, the specific uptake rates (V) (mug N g N 1 h(- 1)) of SPOM measured at ambient concentrations are 10-1000 higher than those of benthic primary producers. Macroalgae have intermediary v, between the seagrass leaf and leaf epiphytes. V are quite variable and the reasons for this variability remain unclear. Despite the difference of specific uptake rates found between benthic and pelagic primary producers, when integrating the uptake fluxes for a water Column of 10 m depth, the contribution of benthic primary producers to N uptake fluxes (g N m(-) (2) h(-) (1)) is significant, corresponding on average to 40% of total uptake flux. This results from the dominance in terms of N biomass of benthic primary producers in this shallow nutrient-poor area. When reported for the entire volume of the Revellata Bay, the contribution of benthic primary producers is reduced to 5 - 10% of total N uptake flux. Although this contribution could appear relatively low, it results in a significant direct transfer of inorganic nitrogen from the water column to the benthic compartment. By this transfer, the benthic plants act as a biological pump incorporating the pelagic N into the benthic compartment for a time longer than the characteristic time of phytoplankton dynamics (month-years vs. day-week). (C) 2003 Elsevier B.V. Alt rights reserved. [less ▲]

The crustacean scavenger guild in Antarctic shelf, bathyal and abyssal communities

in Deep-Sea Research Part II-Topical Studies in Oceanography (2004), 51(14-16), 1733-1752

Peracarid crustaceans form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. Although several studies are available about ... [more ▼]

Peracarid crustaceans form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. Although several studies are available about scavengers from tropical and temperate seas, very little information has been published about such species living in Antarctic waters, particularly at greater depths. The present paper is based on a collection of 31 baited trap sets deployed in the Weddell Sea, Scotia Sea, and off the South Shetland Islands, and presents results on the geographical and bathymetric distribution of the different taxa and on the eco-functional role of scavengers. Some 68,000 peracarid crustaceans from 62 species were collected. About 98% of individuals belonged to the amphipod superfamily Lysianassoidea, and 2% to the isopod family Cirolanidae. Of these species, 31, including 26 lysianassoids (1400 individuals), were collected deeper than 1000 m. High species richness was discerned for the eastern Weddell Sea shelf compared with other Antarctic areas. The Antarctic slope also seems to be richer in species than other areas investigated in the world, while in the abyss, scavenger species richness appears to be lower in Antarctica. A richness gradient was thus observed from the shelf to the deep. For amphipods, a number of species extend their distribution from the shelf to the slope and only one to the abyssal zone. Amphipod species showed degrees of adaptation to necrophagy. The functional adaptations of the mandible and the storage function of the gut are discussed. Feeding experiments conducted on lysianassoid species collected at great depths and maintained in aquaria showed a mean feeding rate of about 1.4-4.1% dry body weightday(-1), which is consistent with data obtained from other species. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

Experimental determination of the feeding rate for some Antarctic amphipod species

Poster (2003, April)

Carbon and nitrogen isotopic ratios of the seagrass Posidonia oceanica: Depth-related variations

in Botanica Marina (2003), 46(6), 555-561

Nitrogen (delta(15)N) and carbon (delta(13)C) isotopic compositions of Posidonia oceanica were determined during three seasons along a bathymetric gradient (438 m depth).The delta(15)N values are low (2.2 ... [more ▼]

Nitrogen (delta(15)N) and carbon (delta(13)C) isotopic compositions of Posidonia oceanica were determined during three seasons along a bathymetric gradient (438 m depth).The delta(15)N values are low (2.2+/-0.9%) and variable.They do not show any relation to depth or sampling dates. There is a significant difference between the delta(15)N values of the youngest and the oldest leaves, probably as a result of N resorption and senescing during leaf ageing. The delta(13)C values of young Posidonia leaves vary with depth, showing the relationship between delta(13)C values and primary productivity rate, and the use of a bicarbonate/CO2 mixture as an inorganic carbon source. The delta(13)C values of the oldest P. oceanica leaves are depleted in C-13 compared to those of young leaves. This modification of the C-13 signatures in relation to leaf age is particularly important between 20 and 29 m depth. This modification could be related to photosynthetic rate change during ageing, but also to change in carbohydrate composition and content. [less ▲]

Structural and ecofunctional biodiversity of the amphipod crustacean benthic taxocoenoses in the Southern Ocean

in Belgian Scientific Research Programme on the Antarctic-Phase 4. Vol 1. Marine Biota and Global Change (2003)

Biodiversity pattern in the Southern Ocan: lessons from Crustacea.

in Huiskes, Ad (Ed.) Antarctic Biology in a Global Context (2003)

Experimental evidence for N recycling in the leaves of the seagrass Posidonia oceanica

in Journal of Sea Research (2002), 48(3), 173-179

A one-year in situ experiment using N-15 as a tracer was designed to assess the N recycling in the leaves of the seagrass Posidonia oceanica (L.) Delile. R oceanica was shown to partly recycle the ... [more ▼]

A one-year in situ experiment using N-15 as a tracer was designed to assess the N recycling in the leaves of the seagrass Posidonia oceanica (L.) Delile. R oceanica was shown to partly recycle the internal nitrogen pool of its leaves in order to contribute to new leaf growth. The leaves sampled in June 1999 contained 20% of the quantity of N-15 found in June 1998. N recycling caused a difference between N and biomass turnover rate (0.8 vs 1.3 y(-1)) of Posidonia leaves. This 40% difference should correspond to the contribution of recycled N to the annual N requirement of Posidonia leaves. The N recycling appears to be insufficient to significantly reduce the quantitative impact of N loss due to autumnal leaf fall. However, new leaf growth between June and October is mainly sustained by this recycling because the tracer concentration in new leaves was the same as in the other leaves. By contrast, tracer concentration decreased drastically between October 1998 and June 1999, showing the more important contribution of N uptake during winter and spring. Nevertheless, recycling occurs throughout the year as demonstrated by the presence of tracer in the youngest leaves of shoots sampled one year after the tracer addition. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]