Production and standing stocks of the kelp Macrocystis laevis Hay at the Prince Edward Islands,Subantarctic

Summary The recently described species Macrocystis laevis Hay is endemic to the Prince Edward Islands. Aerial photographs of Marion Island were used to outline the distribution of the kelp and to assess its cover. M. laevis occurs along the lee shore of the island, between the 5 and 20 m isobaths. Plant densities and gross plant morphology were measured by divers during April/May 1988. Net production was estimated from growth measurements taken in April/May 1988 and 1989 and again during August 1989. The mean biomass of kelp was 0.67 kgC·m^–2 within the kelp beds. Net production was estimated at 7.7 gC·m^–2·d^–1 and 11.5 gC·m^–2d^–1 during the months of April and August respectively. M. laevis had a uniform frond-length frequency distribution, which suggests that only the oldest fronds are lost by wave action or senescence. Based on calculations for M. laevis and Durvillaea antarctica (the two species making up most of the macrophyte biomass) macrophytes are more productive per unit area than the phytoplankton but contribute less to the seas around the Prince Edward Islands by virtue of their small spatial coverage. Neither of the kelps lose much material as particulate or dissolved organic carbon through fragmentation. The extent of grazing on live M. laevis fronds is unknown, and only D. antarctica contributes to a macrofaunal detrital community. The contribution of M. laevis production to the nearshore ecology of the islands seems limited, as we suspect that almost all of its production is exported to the open ocean pelagic system.     

Cadmium, copper and zinc in octopuses from Kerguelen Islands, Southern Indian Ocean

 Concentrations of cadmium, copper and zinc were measured in 34 octopuses over a large range of size and weight, caught in the Kerguelen shelf waters. Compared with levels normally encountered in European cephalopods, Cd concentrations in both species were very high: 30.7–47.1 and 27.3–54.4 μg/g dry weight in Graneledone sp. and Benthoctopus thielei, respectively; Cu concentrations were generally low while Zn concentrations exhibited similar levels. Distribution of Cd in tissues showed that the high levels of Cd in Kerguelen octopuses resulted from very high levels of the metal in the digestive gland (369 and 215 μg/g dry wt in Graneledone sp. and Benthoctopus thielei, respectively). The digestive gland accumulated about 90% of the total Cd in the whole animal. Due to the very high concentrations of Cd in the Kerguelen octopuses, we hypothesize that these species play an important role in the process of Cd transfer throughout the food chain to top vertebrate predators in this area. Received: 2 June 1997 / Accepted: 30 October 1997     

Subantarctic krill, Euphausia vallentini Stebbing, preyed upon by penguins around Crozet Islands (Southern Indian Ocean): population structure and annual cycle

Dietary studies performed on three planktivorous penguins, Eudypteschrysolophus, E.chrysocome and Pygoscelis papua, provided alarge collection of well-preserved Euphausia vallentiru at differentperiods of the year. The change of carapace-length distributions,gut fullness and sexual maturity stages of E.vallentini aredescnbed. and a scheme for the life history of this speciesis proposed from this set of data. Its main characteristicsare as follows: mating peak in October-November; recruitmentof post-larval individuals from December-January onwards; fastgrowth until May; zero winter growth between June and mid-Augustdue to a minimum feeding activity Feeding activity reaches itshighest level from August to early October and is coincidentwith maturation, growth recovery, enhancement of sexual dimorphismand beginning of breeding season. Assuming that juveniles are1 year old when they begin to be recruited in penguin stomachs,E.vallentini is supposed to have a 2-year-life span in Crozetwaters. Two-year-old individuals are supposed to die in summeror autumn Juveniles can reach sexual maturity as early as November-Decemberwhen they are 1 year old and 16 mm body length: however, theyare unlikely to mate in significant numbers at this age. Inspite of specific limitations, the present sampling method iswell suited to routine surveys of local euphausiid populations.     

Helminths from introduced small mammals on Kerguelen, Crozet, and Amsterdam Islands (southern Indian Ocean).

Four monoxenous nematodes and 1 heteroxenous cestode were found in 4 species of introduced small mammals on isolated sub-Antarctic islands of the Indian Ocean. In the Kerguelen Archipelago, Syphacia obvelata, Passalurus ambiguus (Nematoda: Oxyuridae), and Rodentolepis straminea (Cestoda: Cyclophyllidae) were respectively found in the house mouse Mus musculus, the rabbit Oryctolagus cuniculus, and the black rat Rattus rattus. One accidental nematode, Trichostrongylus sp. (Nematoda: Trichostrongylidae), was also found in a black rat on Kerguelen. On Possession Island (Crozet Archipelago), R. straminea was present in the black rat. On Amsterdam Island, the brown rat R. norvegicus harbored 2 species, R. straminea and Nippostrongylus brasiliensis (Nematoda: Heligmonellidae). The small number of founder hosts and the depauperate terrestrial communities on these remote islands explain the low diversity in the helminth communities of these introduced mammals compared with continental populations.     

Ontogeny of aquatic behaviours in Antarctic fur seal (Arctocephalus gazella) pups in relation to growth performances at Kerguelen Islands

In diving marine predators, such as pinnipeds, the development of diving and foraging skills prior to weaning might be critical to post-weaning survival. Here, we examined the effect of pup mass growth on the amount of time devoted to aquatic activities and the dive performance of Antarctic fur seal, Arctocephalus gazella, pups on Kerguelen Island. Maternal attendance and mass-specific growth rate were assessed for 85 pups. Two types of monitoring were applied: visual observations of behaviours for 60 pups and the deployment of time-depth recorders (TDRs) on 19 female pups. At approximately 2 months of age, pups demonstrated minimal diving behaviour, but displayed considerable aquatic activity. While mothers were foraging at sea, pups fasted on land (6.0 ± 1.3 d). As the mass-specific growth rate was different between sexes, only data on female pups were analysed (n = 31). Mass-specific growth rate was related to maternal attendance patterns and impacted the amount of time allocated by pups to aquatic activities. The time spent in the water by pups was quadratically related to fasting progress. This study shows the importance of growth and fasting progress on the quantity of time pups devoted to aquatic activities. Our results suggest that greater post-weaning survival of heavier pups may be due not only to their greater body reserves, as reported in several studies, but also possibly to from their greater aquatic skills and physiological adaptations developed during the suckling period.     

Benthic seasonality in an intertidal mud flat at Kerguelen Islands (Austral ocean). The relationships between meiofaunal abundance and their potential microbial food

Summary Samples were taken weekly for one year at an intertidal mudflat at the Halage des Swains, Morbihan Sound, Kerguelen Islands, for meiofauna, their suspected microbial food (bacteria and diatoms) and associated chemical and physical factors. Organic carbon and nitrogen content, bacterial abundance and biomass, pigment content and daily primary production, were significantly correlated (Spearman rank) to the temperature. Meiofauna exhibited very high abundances (up to 14 000 ind./10 cm^–2) without seasonal trend but with distinct short term oscillations of population densities. No direct correlation occurred between meiofauna (85.9% nematodes and 10.8% copepods) and temperature. Total meiofauna abundance was positively correlated to bacterial biomass in the oxidized layer, to organic content below redox potential discontinuity layer, and negatively correlated to the hourly primary production. The data suggest that nematodes are correlated to bacterial biomass and organic content in the sediment. Effect of ambient temperature on development time of nematofauna could be described by a Belehradek function. Even though some correlations existed, this study shows that peaks of meiofaunal abundance are not correlated to potential food abundance variability. Thus, the limitation of meiofauna community and its annual pattern is reasonably governed by the development time and reproductive strategy of the few co-dominant species of the main taxa.     

Restricted Genetic Variation in Populations of Achatina (Lissachatina) fulica outside of East Africa and the Indian Ocean Islands Points to the Indian Ocean Islands as the Earliest Known Common Source

The Giant African Land Snail, Achatina ( = Lissachatina) fulica Bowdich, 1822, is a tropical crop pest species with a widespread distribution across East Africa, the Indian subcontinent, Southeast Asia, the Pacific, the Caribbean, and North and South America. Its current distribution is attributed primarily to the introduction of the snail to new areas by Man within the last 200 years. This study determined the extent of genetic diversity in global A. fulica populations using the mitochondrial 16S ribosomal RNA gene. A total of 560 individuals were evaluated from 39 global populations obtained from 26 territories. Results reveal 18 distinct A. fulica haplotypes; 14 are found in East Africa and the Indian Ocean islands, but only two haplotypes from the Indian Ocean islands emerged from this region, the C haplotype, now distributed across the tropics, and the D haplotype in Ecuador and Bolivia. Haplotype E from the Philippines, F from New Caledonia and Barbados, O from India and Q from Ecuador are variants of the emergent C haplotype. For the non-native populations, the lack of genetic variation points to founder effects due to the lack of multiple introductions from the native range. Our current data could only point with certainty to the Indian Ocean islands as the earliest known common source of A. fulica across the globe, which necessitates further sampling in East Africa to determine the source populations of the emergent haplotypes.     

Reproductive compatibility and genetic and morphometric variability among populations of the predatory mite,Amblyseius largoensis (Acari: Phytoseiidae), from Indian Ocean Islands and the Americas

The red palm mite (RPM), Raoiella indica Hirst (Acari: Tenuipalpidae), is an invasive phytophagous mite that was recently introduced into The Americas. The predatory mite Amblyseius largoensis Muma (Acari: Phytoseiidae) has been the only natural enemy consistently found in association with RPM. This study aimed to determine if A. largoensis populations from the Indian Ocean Islands (La Réunion and Mauritius) and the Americas (Brazil, Trinidad and Tobago and the USA) consist a taxonomic unit or a group of cryptic species. First, the morphological variability among the A. largoensis populations from these areas was evaluated through morphometric analyses of 36 morphological traits. Then, their genetic variability and phylogenetic relationships were assessed based on two target DNA fragments: the nuclear Internal Transcribed Spacer and the mithochondrial 12S rRNA. Finally, reproductive compatibility of the populations from La Réunion and Roraima, Brazil was evaluated. Morphometric differences between the A. largoensis specimens from La Réunion Island and the Americas were observed, most of them on the length of the setae. Molecular analysis indicated that the A. largoensis populations from the Indian Ocean Islands and the Americas belong to the same taxonomic entity, although to two well defined genetic groups. Crossings involving the A. largoensis populations from La Réunion Island and Roraima, Brazil revealed complete reproductive compatibility between these populations. Information on the morphometric and genetic variability among studied A. largoensis populations can be further exploited in future studies to follow colonization of Indian Ocean Islands populations in the Americas, in the case of field releases.     

In and out of Madagascar: Dispersal to Peripheral Islands, Insular Speciation and Diversification of Indian Ocean Daisy Trees (Psiadia, Asteraceae)

Madagascar is surrounded by archipelagos varying widely in origin, age and structure. Although small and geologically young, these archipelagos have accumulated disproportionate numbers of unique lineages in comparison to Madagascar, highlighting the role of waif-dispersal and rapid in situ diversification processes in generating endemic biodiversity. We reconstruct the evolutionary and biogeographical history of the genus Psiadia (Asteraceae), a plant genus with near equal numbers of species in Madagascar and surrounding islands. Analyzing patterns and processes of diversification, we explain species accumulation on peripheral islands and aim to offer new insights on the origin and potential causes for diversification in the Madagascar and Indian Ocean Islands biodiversity hotspot. Our results provide support for an African origin of the group, with strong support for non-monophyly. Colonization of the Mascarenes took place by two evolutionary distinct lineages from Madagascar, via two independent dispersal events, each unique for their spatial and temporal properties. Significant shifts in diversification rate followed regional expansion, resulting in co-occurring and phenotypically convergent species on high-elevation volcanic slopes. Like other endemic island lineages, Psiadia have been highly successful in dispersing to and radiating on isolated oceanic islands, typified by high habitat diversity and dynamic ecosystems fuelled by continued geological activity. Results stress the important biogeographical role for Rodrigues in serving as an outlying stepping stone from which regional colonization took place. We discuss how isolated volcanic islands contribute to regional diversity by generating substantial numbers of endemic species on short temporal scales. Factors pertaining to the mode and tempo of archipelago formation and its geographical isolation strongly govern evolutionary pathways available for species diversification, and the potential for successful diversification of dispersed lineages, therefore, appears highly dependent on the timing of arrival, as habitat and resource properties change dramatically over the course of oceanic island evolution.     

Abundance of thraustochytrids and bacteria in the equatorial Indian Ocean, in relation to transparent exopolymeric particles (TEPs)

Thraustochytrid protists are often abundant in coastal waters. However, their population dynamics and substrate preferences in the oceanic water column are poorly understood. We studied the abundance and distribution of thraustochytrids, bacteria and TEPs in the equatorial Indian Ocean waters during September 2003, October 2004 and September 2006. Thraustochytrids and bacteria were abundant, suggesting high biological productivity of the region. Thraustochytrids were positively related to bacteria during October 2004 but not at other times, suggesting overlapping or varying substrate preferences at different times. Thraustochytrid and bacteria were positively related to TEPs only in a few stations during October 2004, but were mostly positively related to TEPs generated from in situ water in a roller table experiment. TEPs from natural samples during October 2004 had a much greater affinity to the lectin Concanavalin A than to Limulin compared with those in September 2006 and from the roller tank experiments. The chemical composition of TEPs might explain their relationship with thraustochytrids. Thraustochytrids averaged a higher biomass than bacteria in two of the three cruises, but were less frequent and more patchily distributed compared with bacteria.     

Demographic, reproductive, medical, and environmental factors in relation to gastroschisis.

To identify risk factors for gastroschisis other than drug use in pregnancy, an analysis of data collected in a case-control surveillance program of birth defects (1976-1990) was conducted. Drug use is considered in Werler et al., Teratology, 45:361-367, 1992. Maternal demographic, reproductive, and medical factors, and first trimester environmental exposures, were compared between 76 gastroschisis cases and 2,581 malformed controls. A strong inverse association was found for maternal age: relative to women 30 years or older, relative risks for 25-29, 20-24, and less than 20-year-old women were 1.7, 5.4, and 16, respectively. Multivariate relative risks (and 95% confidence intervals) for alcohol use were as follows: for 1-5 drinks per week, 1.6 (0.7-3.4); for greater than or equal to 6 drinks per week, 2.5 (0.9-6.8); for a maximum of 1-4 drinks at any one time, 0.8 (0.4-1.6); and for a maximum of greater than or equal to 5 drinks, 2.8 (1.2-6.5). With the effect of age taken into account, no associations were identified for cigarette smoking, consumption of caffeinated or decaffeinated coffee, unplanned pregnancy, 12 or less years of education, or a parity of two or more. Other medical and reproductive factors, including weight gain, vaginal bleeding, nausea or vomiting, influenza, "other" infection, and history of spontaneous abortion or elective abortion did not increase the risk.     

Heat shock protein responses to salinity, food deprivation, and temperature in the invasive ground beetle Merizodus soledadinus at the Kerguelen Islands

The ground beetle Merizodus soledadinus was introduced a century ago to the Kerguelen Islands. It has since become invasive and has colonized most coastlines east of this archipelago. In invaded intertidal zones, M. soledadinus has to deal with substrates that can reach high salinity levels. In addition to saline stress, the rapid spread of this invasive insect on the Kerguelen Islands may result in starving during dispersal, especially during winter periods. In order to gain a further understanding of the factors that have contributed to the success of this insect in invading the Kerguelen Islands, we assessed the variability in the expression of heat shock cognate 70 (HSC70) in M. soledadinus. HSC70 are constitutively expressed by insects, and we examined if the expression of HSC70 could picture the health degree of the ground beetles exposed at a range of environmental conditions, for example, varying temperatures (0, 4, 8, 12, and 20 °C), trophic status (fed and food-deprived individuals), and saline conditions (salinities of 0, 35, and 70). We found that HSC70 expression decreased with increasing salinity. HSC70 expression was not modified in response to non-extreme thermal variations or short-term food deprivation, which did not appear to be stressful conditions for M. soledadinus given the survival results. We concluded that HSC70 expression may serve as a molecular indicator of the levels of well-being of this ground beetle when exposed to a range of environmental perturbations.     

Planktonic foraminifera from the eastern Indian Ocean: distribution and ecology in relation to the Western Pacific Warm Pool (WPWP)

Faunal assemblages, principal component (PCA), canonical correspondence (CCA), and factor analysis are applied to planktonic foraminifera from 57 core-top samples from the eastern Indian Ocean. The foraminiferal lysocline occurs at 2400 m north of 15°S where carbonate dissolution is induced by the Java upwelling system, and occurs deeper south of 15°S where carbonate dissolution is characteristic of the oligotrophic regions in the Indian Ocean. Dissolution effects, the February standing stock at the time of collection of the plankton-tow material, and different production rates explain the different foraminiferal assemblages found between plankton-tow and core-top samples. Core-top samples are differentiated by PCA into four groups — Upwelling, Western Pacific Warm Pool (WPWP), Transitional, and Southern — that are related to environmental variables (temperature, salinity and nutrients); all environmental variables follow a strong latitudinal component as indicated by the CCA analysis. Similarly, three assemblages are recognized by factor analysis: Factor 1 (dominated by Globigerinoides sacculifer, G. ruber, Globigerinita glutinata and Globorotalia cultrata), factor 2 (dominated by Globigerina bulloides and Globorotalia inflata) and factor 3 (dominated by Neogloboquadrina dutertrei) explain more than 92% of the variance, and are related to sea-surface temperature, thermocline depth and nutrient levels. The seasonal influence of the Java upwelling system supplies nutrients, phyto- and zooplankton to the oligotrophic eastern Indian Ocean (factor 1). South of 24°S, a deep chlorophyll maximum, a deep euphotic zone, a deep thermocline, SSTs below 22°C, and brief upwelling pulses seem to explain factors 2 and 3. The ratio of G. sacculifer and N. dutertrei, two mutually excluding species, appears to indicate the southern boundary of the WPWP. This ratio is applied to core Fr10/95-11 to demonstrate past shifts of the southern boundary of the WPWP.     

Importance of the large copepod Paraeuchaeta antarctica (Giesbrecht, 1902) in coastal waters and the diet of seabirds at Kerguelen, Southern Ocean

The importance of the euchaetid copepod Paraeuchaeta antarcticain the subantarctic pelagic ecosystem was quantified in thecoastal waters of the Golfe du Morbihan at Kerguelen Islandsby comparing food samples from two diving seabirds with concurrentnet samples taken within the predator foraging area. Paraeuchaetaantarctica occurred in very high densities (up to 30 individualsm^-3 and 96 mg dry weight m^-3) in the water column, being moreabundant in the deepest part of the gulf than in shallow watersor at the more offshore shelf stations. The common diving petrelfeeds almost exclusively on crustaceans, its diet being dominatedby the amphipod Themisto gaudichaudii (52% by number and 84%by reconstituted mass) and P. antarctica (33% and 16%, respectively).Rockhopper penguins preyed upon crustaceans and fish, with fourtaxa being important, namely T. gaudichaudii (37% and 23%, respectively),Euphausia vallentini (24% and 41%), postlarval fish (10% and24%), and P. antarctica (13% and 3%). Paraeuchaeta antarcticadominated numerically in 21% of the diving-petrel food samplesand in 12% of penguin samples. The two bird species segregatedby preying upon different developmental stages of P. antarctica,diving petrels fed equally on CV of both sexes and CVI, whilepenguins fed on CVI only. Comparison of P. antarctica foundin net and food samples indicated no prey selection by commondiving petrels that caught the different copepod stages in proportionto their availability in the water column. On the other hand,the diving performance of penguins, which is better than thatof the petrels (mean maximum dive depths 69 m for penguins versus32 m in petrels), allows them to catch CVI in deeper waters,probably near the bottom. Our study shows that P. antarcticais a major component of the coastal macrozooplankton communityand a significant prey for two species of diving seabirds inhabitingKerguelen. This is also the first record of a copepod speciesas a prey for penguin, and the first to highlight P. antarcticain the food of austral seabirds.     

Stream fish assemblages in relation to environmental factors on a montane plateau (Nyika Plateau,Malawi)

Few studies have examined river fishes of Malawi. This study is one of the first to examine the stream fish assemblages on the Nyika Plateau in northern Malawi. Twenty four sites were sampled over three different periods in two river systems of the plateau. Eighteen species were collected and among these was Hippopotamyrus ansorgii, the first collection of this species in the Lake Malawi catchment. Three species, including a non-native trout, were common in the two systems studied. Correspondence analysis (CA) suggested gradients in species composition related to altitude and river type. Species succession, from a trout dominated upstream to a downstream dominated by indigenous species, was shown on the first CA axis. The second CA axis showed the assemblage of the plateau separated by river type. A direct gradient analysis method, canonical correspondence analysis (CCA), showed the importance of two stream position metrics (stream order and c-link), depth, water temperature and substrate type in determining species composition. According to variation partitioning in CCA, the spatial and temporal components respectively explained 46% and 3.6% variation in assemblage composition based on the all species data matrix, and 48.7% and 2.6% variation in assemblage composition based on the native species data matrix. The species collected were also discussed in relation to the morphological adaptations in their body forms to the environmental conditions of the streams studied.     

Salmonella infections in a marsupial, the quokka (Setonix brachyurus), in relation to seasonal changes in condition and environmental stress

An unusual abundance of Salmonella infections was studied in an island population of a wild marsupial, the quokka (Setonix brachyurus), which experiences starvation in summer associated with significant mortality. The frequency of infections was found to vary seasonally over most parts of the island, with high infection rates (70 to 100%) in summer and low infection rates (0 to 30%) in winter. In some samples, there was an average of as many as two isolations per animal, and up to five isolations were made from a single animal. By the end of summer, virtually all animals excreted Salmonella spp., with a median rate of excretion of approximately 3,000 Salmonella organisms per g of feces. The seasonal changes occurred over intervals of only weeks. The infections are believed to be associated with disruption of the digestive physiology of the animals caused by the poor quality of feed available in summer. This conclusion was supported by a quantitative study of the infections and by a field manipulation experiment which delayed the initiation of the infections as long as a food supplement was available. The proliferation of Salmonella spp. is discussed in terms of the ecology of the quokka and of the use of Salmonella spp. as indicators of environmental stress acting on the animals.     

Seaweed of the littoral zone at Cove Island in Long Island Sound: annual variation and impact of environmental factors

A site in the western part of Long Island Sound was monitored from January 2000 to May 2002. The littoral was divided into five different zones from the supra-littoral fringe (A) to the infra-littoral fringe (E). The midshore was dominated by Fucus vesiculosus L. and the sublittoral fringe by Chondrus crispus Stackh. There was a significant change in community structure over the years and the predominant change occurred between 2001 and 2002. The alternation in community structure was caused by an increase in abundance of species like Porphyra suborbiculata Kjellm., Porphyra leucosticta Type A and C (Neefus et al. 2000), Ceramium virgatum Roth, and Codium fragile subsp. tomentosoides (van Goor)Silva and a decrease in abundance in Fucus vesiculosus, Blidingia minima (Nägeli ex Kütz.) Kylin and Ulva lactuca L. The changes in community structure coincided with the change in environmental conditions. Air temperature as well as surface seawater temperature (depth <2 m) were the most important factors of those analyzed. Temperature seems to be the bottom-up force regulating the community structure.