Benthic foraminifera in the Arctic Ocean

We examine the quantitative composition of benthic foraminiferal assemblages of Rose Bengal-stained surface samples from 37 stations in the Laptev Sea, and combine this data set with an existing data set along a transect from Spitsbergen to the central Arctic Ocean. Foraminiferal test accumulation rates, diversity, faunal composition and statistically defined foraminiferal associations are analysed for living (Rose Bengal-stained) and dead foraminifers. We compare the results of several benthic foraminiferal diversity indices and statistically defined foraminiferal associations, including Fisher's alpha and Shannon-Wiener diversity indices, Q-mode principal component analysis and correspondence analysis. Diversity and faunal density (standing stock) of living benthic foraminifers are positively correlated to trophic resources. In contrast, the accumulation rate of dead foraminifers (BFAR) shows fluctuating values depending on test disintegration processes. Foraminiferal associations defined by Q-mode principal component analysis and correspondence analysis are comparable. The factor values of the correspondence analysis allow a quantitative correlation between the foraminiferal fauna and the local carbon flux, which may be used as a tool to estimate changes in primary productivity.

Benthic foraminifera off West Africa (1°N to 32°S)

Recent benthic foraminifera (> 125 µm) were investigated from multicorer samples on a latitudinal transect of 20 stations between 1°N and 32°S along the upper slope off West Africa. Samples were selected from a narrow water depth interval, between 1200 and 1500 m, so that changes in water masses are minimized, but changes in surface productivity are important and the only significant environmental variable. Live (Rose Bengal stained) benthic foraminifera were counted from the surface sediment down to a maximum of 12 cm. Dead foraminifera were investigated in the top 5 cm of the sediment only. Five live and five dead benthic foraminiferal assemblages were identified using Q-mode principal component analysis, matching distinct primary productivity provinces, characterized by different systems of seasonal and permanent upwelling. Differences in seasonality, quantity, and quality of food supply are the main controlling parameters on species composition and distribution of the benthic foraminiferal faunas. To test the sensitivity of foraminiferal studies based on the uppermost centimeter of sediment only, a comparative Q-mode principal component analysis was conducted on live and dead foraminiferal data from the top 1 cm of sediment. It has been demonstrated that, on the upper slope off West Africa, most of the environmental signals as recorded by species composition and distribution of the 'total' live and dead assemblages, i.e., including live and dead foraminifera from the surface sediment down to 12 cm and 5 cm, respectively, can be extracted from the assemblages in the top centimeter of sediment only. On the contrary, subsurface abundance maxima of live foraminifera and dissolution of empty tests strongly bias quantitative approaches based on the calculation of standing stocks and foraminiferal numbers in the topmost centimeter.

Vertical distribution of benthic foraminifers in the Arctic Ocean

The vertical distribution of living (Rose Bengal stained) benthic foraminifers was determined in the upper 15 cm of sediment cores taken along transects extending from the continental shelf of Spitsbergen through the Eurasian Basin of the Arctic Ocean. Cores taken by a multiple corer were raised from 50 stations with water depths between 94 and 4427 m, from areas with moderate primary production values to areas that are among the least productive ones in the world. We believe, that in the Arctic Ocean the vertical distribution of living foraminifers is determined by the restricted availability of food. Live foraminiferal faunas are dominated by potentially infaunal species or epifaunal species. Species confined to the infaunal microhabitat are absent in Arctic sediments that we examined, and predominantly infaunal living species are nowhere dominant. In general, an infaunal mode of life is restricted to the seasonally ice-free areas and thus to areas with at least moderate primary production during the summer period. Under the permanent ice cover living species are usually restricted to the top centimeter of the sediment surface, even though some are able to dwell deeper in the sediment under ice-free conditions.

Micropaleontology and stable isotope record of ODP Hole 178-1098C

Detailed study of four Holocene sediment intervals from Ocean Drilling Program Site 1098 (Palmer Deep, Antarctic Peninsula) reveals that in situ dissolution of calcareous foraminifers in the core repository has significantly altered and in some cases eliminated calcareous foraminifers. Despite dissolution, the foraminifer and supporting diatom data show that the most open-ocean and reduced sea-ice conditions occurred in the early Holocene. The influence of Circumpolar Deep Water was greatest during the early Holocene but continued to be important throughout the Holocene. An increase in sea-ice proximal diatoms at 3500 cal. BP documents an expansion in the amount of persistent sea ice. The inferred increase in sea ice corresponds with an overall increase in magnetic susceptibility values. Benthic foraminifers are present in all samples from the Palmer Deep, including the middle Holocene pervasively laminated sediments with low magnetic susceptibility values. The consistent presence of mobile epifaunal benthic foraminifers in the laminated sediments demonstrates that the laminations do not represent anoxic conditions. The uniform composition of the agglutinated foraminifer fauna throughout the late Holocene suggests that the Palmer Deep did not experience bottom-water-mass changes associated with the alternating deposition of bioturbated or laminated sediments.

Communities and microhabitats of living benthic foraminifera from the tropical East Atlantic

Living (Rose Bengal stained) benthic foraminifera were collected with a multicorer from six stations between 2°N and 12°S off West Africa. The foraminiferal communities in the investigated area reflect the direct influence of different productivity regimes, and are characterized by spatially and seasonally varying upwelling activity. At five stations, foraminiferal abundance coincides well with the gradient of surface productivity. However, at one station off the Congo River, the influence of strong fresh water discharge is documented. Although this station lies directly in the center of an upwelling area, foraminiferal standing stocks are surprisingly low. It is suggested that the Congo discharge may induce a fractionation of the organic matter into small and light particles of low nutritional content, by contrast to the relatively fast-sinking aggregates found in the centers of high productivity areas. Quality and quantity of the organic matter seem to influence the distribution of microhabitats as well. The flux of organic carbon to the sea-floor controls the sequence of degradation of organic matter in sediment and the position of different redox fronts. The vertical foraminiferal stratification within sediment closely parallels the distribution of oxygen and nitrate in porewater, and reflects different nutritive strategies and adaptation to different types of organic matter. The epifauna and shallow infauna colonize oxygenated sediments where labile organic matter is available. The intermediate infauna (M. barleeanum) is linked to the zone of nitrate reduction in sediments where epifaunal and shallow infaunal species are not competitive anymore, and must feed on bacterial biomass or on metabolizable nutritious particles produced by bacterial degradation of more refractory organic matter. The deep infauna shows its maximum distribution in anoxic sediments, where no easily metabolizable organic matter is available.

Constitutio vnigenitus S.mi D.N. Papae Clementis XI /

Mode of access: Internet.

Metamorphoses Ovidii : argvmentis quidem soluta oratione, enarrationibus autem & allegoriis elegiaco versu accuratissimè expositae, summaq[ue] diligentia ac studio illustratae /

Includes index.

Confirmation of the existence of alloparasitoids in nature - host relationships of an Australian Coccophagus species that parasitizes mealy bugs

Heteronomous hyperparasitoids are parasitic wasps with sex-related host relationships that are unique to a group of genera in the chalcidoid family Aphelinidae. Females are primary parasitoids of various sedentary bugs (mainly, scale insects, mealy bugs, and whiteflies). Males, in contrast, are hyperparasitic, and they frequently develop at the expense of female conspecifics. Alloparasitoids constitute a special category of heteronomous hyperparasitoids, for their males never develop through female conspecifics. The existence of alloparasitic host relationships and the utility of the category 'alloparasitoid' have both been questioned. Here, we present results that confirm the existence of the alloparasitic way of life among heteronomous aphelinids. We investigated an undescribed species of Coccophagus (Hymenoptera: Aphelinidae), an Australian parasitoid that attacks the introduced lantana mealy bug, Phenacoccus parvus Morrison (Homoptera: Pseudococcidae), in Queensland. A year-long field survey regularly returned large numbers of female Coccophagus spec. near gurneyi individuals from P. parvus (total n = 4212), but only few males (n = 11). Males emerged from samples only when the encyrtid parasitoid Anagyrus diversicornis (Howard) (Hymenoptera: Encyrtidae) was present in samples in relatively high numbers. Laboratory oviposition tests confirmed that A. diversicornis is a male host and showed that males do not develop at the expense of conspecific females. Other studies show that males are attracted in numbers to virgin females held in cages above mealy bug-infested Lantana montevidensis (Spreng.) Briq. (Verbenaceae) in the field, demonstrating that they are common in the population as a whole. This confirms that the males need hosts other than conspecific females and that their usual hosts are present outside of the lantana/P. parvus system. The implications of these results for developing a realistic classification of heteronomous host relationships are discussed.

Summer dormancy in perennial temperate grasses

Background and Aims Dormancy has been extensively studied in plants which experience severe winter conditions but much less so in perennial herbaceous plants that must survive summer drought. This paper reviews the current knowledge on summer dormancy in both native and cultivated perennial temperate grasses originating from the Mediterranean Basin, and presents a unified terminology to describe this trait. Scope Under severe drought, it is difficult to separate the responses by which plants avoid and tolerate dehydration from those associated with the expression of summer dormancy. Consequently, this type of endogenous (endo-) dormancy can be tested only in plants that are not subjected to moisture deficit. Summer dormancy can be defined by four criteria, one of which is considered optional: (1) reduction or cessation of leaf production and expansion; (2) senescence of mature foliage; (3) dehydration of surviving organs; and (4, optional) formation of resting organs. The proposed terminology recognizes two levels of summer dormancy: (a) complete dormancy, when cessation of growth is associated with full senescence of foliage and induced dehydration of leaf bases; and (b) incomplete dormancy, when leaf growth is partially inhibited and is associated with moderate levels of foliage senescence. Summer dormancy is expressed under increasing photoperiod and temperature. It is under hormonal control and usually associated with flowering and a reduction in metabolic activity in meristematic tissues. Dehydration tolerance and dormancy are independent phenomena and differ from the adaptations of resurrection plants. Conclusions Summer dormancy has been correlated with superior survival after severe and repeated summer drought in a large range of perennial grasses. In the face of increasing aridity, this trait could be used in the development of cultivars that are able to meet agronomic and environmental goals. It is therefore important to have a better understanding of the genetic and environmental control of summer dormancy.