Description of Vahlkampfia signyensis n. sp. (Heterolobosea), based on morphological, ultrastructural and molecular characteristics

Vahlkampfia signyensis n. sp. was isolated from two soil sites at Signy Island, South Orkney Islands, maritime Antarctic. Trophozoites of the species had a typical vahlkampfiid morphology, showed eruptive movement and did not form flagellates. However, Vahlkampfia signyensis differs from other described species of the genus in a range of morphological and ultrastructural characters, as well as in its 5.8S rDNA sequence. According to its 5.8S rDNA sequence, the new species is most closely related to Vahlkampfia avara. An isolate of the new species had a temperature growth optimum of only 10 °C, and did not grow at either 30 °C or 37 °C. The low optimal growth temperature is adaptively significant for life in the maritime Antarctic

Evidence for geographic isolation and signs of endemism within a protistan morphospecies

The possible existence of endemism among microorganisms resulting from and preserved by geographic isolation is one of the most controversial topics in microbial ecology. We isolated 31 strains of "Spumella-like" flagellates from remote sampling sites from all continents, including Antarctica. These and another 23 isolates from a former study were characterized morphologically and by small-subunit rRNA gene sequence analysis and tested for the maximum temperature tolerance. Only a minority of the Spumella morpho- and phylotypes from the geographically isolated Antarctic continent follow the worldwide trend of a linear correlation between ambient (air) temperature during strain isolation and heat tolerance of the isolates. A high percentage of the Antarctic isolates, but none of the isolates from locations on all other continents, were obligate psychrophilic, although some of the latter were isolated at low ambient temperatures. The drastic deviation of Antarctic representatives of Spumella from the global trend of temperature adaptation of this morphospecies provides strong evidence for geographic transport restriction of a microorganism; i.e., Antarctic protistan communities are less influenced by transport of protists to and from the Antarctic continent than by local adaptation, a subtle form of endemism

Research challenges at the land-sea interface

The land–sea interface, or Coastal Transition Zone (CTZ), is the area that links terrestrial and marine habitats. We use here the definition of [Schaefer, 1972]: “the sea and the land adjacent to the interface, encompassing that region where terrestrial activities importantly impinge on the marine environment, marine resources and marine activities, and where marine activities importantly impinge on the environment, resources, and activities of the land”. The precise spatial scale and extent of the interface in this definition is (appropriately, we feel) ambiguous, as it depends on both the attributes of the interface at any given location, as well as the processes or features being examined. Like many ecotones, the CTZ is an area of intense interactions and enhanced productivity and biodiversity ([Levin et al., 2001]). The coastal zone is also a “keystone” habitat, providing human and ecosystem services out of proportion to its areal extent (e.g., [Costanza et al., 1997]). The coastal zone represents only 8% of the earth, but provides 20% of the oceanic production ( [Liu et al., 2000. K.K. Liu, K. Iseki and S.Y. Chao, Continental margin carbon fluxes. In: R.B. Hanson, H.W. Ducklow and J.G. Field, Editors, The Changing Ocean Carbon Cycle, Cambridge (2000), pp. 187–239.Liu et al., 2000]). Further, 60% of humans, 3.8 billion people, live within 100 kilometers of the sea ( [Vitousek et al., 1997]). This region is a nexus for transportation, production of energy, and food resources for humans. The importance of this region, both to humans and to terrestrial and aquatic ecosystems, makes it crucial that we understand the processes and interactions in this habitat. The coastal transition zone, however, presents a number of difficult research challenges. While these challenges are qualitatively similar to those faced by scientists in other habitats, they are magnified in the coastal transition zone. The goal of this paper is to describe the difficulties that confront the researcher interested in the CTZ, and to offer some ideas for ways in which we as scientists can approach these challenges more fruitfully