Tuamotu Atolls Research Articles

Relationships between bacterioplankton and phytoplankton biomass, production and turnover rate in Tuamotu atoll lagoons

As a part of a multi-disciplinary study of the biological production in 12 Tuamotu atoll lagoons, we assessed phytoplankton and bacterioplankton biomass and production. The only consis- tently significant differences were those existing between lagoons, without any other spatial or seasonal signal. Compared with the surrounding oligotrophic ocean, lagoons displayed an increase in trophic status related to their hydraulic regime (water renewal rate and atoll rim morphology). Bacterioplankton biomass was correlated to phytoplankton biomass (power function, slope 1). Besides these quantitative differ- ences corresponding to the classical 'inverted trophic pyramid', potential exoproteolytic activity in the lagoons increased, relative to bacterial production, with increasing oligotrophy, hinting at an increased reliance on polymeric dissolved organic matter (DOM). In increasingly oligotrophic lagoons, phytoplankton (although less abundant) may increase its ratio of exuded DOM, but sessile benthic fauna (especially corals) was also found to be more abundant and might enrich the water column with high-nitrogen DOM.

Progress in pathological characterization of Syndrome 85 in the black-lip pearl oyster Pinctada margaritifera

A programme of zoosanitary survey of the populations of black-lip pearl oyster ( P. margaritifera) has been developed in French Polynesia during 1996 and 1997. Based on histological and ultrastructural examinations, the study of pearl oysters sampled in several pearl farms from the Society Islands, Tuamotu Atolls and Gambier Archipelago, has been particularly turned to enzootic pathological problems. Particular attention has been given to the shell disease and to the necrosis of the adductor muscle, symptoms that had accompanied the mass mortality in 1985. Virus–like particles, about 40 nm in diameter, were detected in membrane bound vesicles from the necrosized muscle tissue. A new Rickettsia-like organism found in epithelial cells of the digestive tubules was described, while parasites previously reported, such as cestodes and gregarines, were recognized in some animals. Apart from the pathology, a thorough study of ‘parasite-like bodies’ discovered in the pearl sack epithelium showed dysfunction in the periostracal secretion.

Nutrient stimulation of bacterioplankton growth in Tuamotu atoll lagoons

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 21:125-137 (2000) - doi:10.3354/ame021125 Nutrient stimulation of bacterioplankton growth in Tuamotu atoll lagoons J.-P. Torréton1,*, V. Talbot1, N. Garcia2 1Institut de Recherche pour le Développement, Laboratoire HEA, BP 5045, 34032 Montpellier cedex 1, France 2CNRS, Laboratoire d¹Océanographie et de Biogéochimie UMR 6535 (COM-OSU), Campus de Luminy, 13288 Marseille, France *Present address: Institut de Recherche pour le Développement, Université Montpellier II, UMR 5556, Case 093, 34095 Montpellier cedex 05, France. E-mail: torreton@ird.fr ABSTRACT: Knowledge of the factors regulating bacterioplankton growth is of considerable importance in attempts to understand the functioning of biogeochemical cycles and particularly their evolution after perturbation. We first tested the effect of nutrient additions on the growth of bacterioplankton assemblages collected from 10 atoll lagoons of various morphologies in the Tuamotu Archipelago and in oceanic surface waters surrounding them. Then, we examined these responses in relation to ambient nutrient concentrations and bacterioplankton community turnover rates in these lagoons. The lagoons studied exhibited a range of NH4 (~0 to 0.7 μM), NO2+NO3 (~0 to 0.5 μM), and PO4 (~0 to 0.3 μM) concentrations. Responses were assessed on bacterioplankton grown in seawater cultures during 2 seasons (end of rainy season, end of dry season) and amended with NH4-N, PO4-P or glucose-C in all possible combinations. The 10 lagoons investigated exhibited various responses to nutrient additions. Including co-stimulations, bacterioplankton growth was stimulated by C, N and P additions in 4, 10 and 4 cases, respectively. One atoll lagoon showed inconsistent responses during both cruises. Another one showed no response to any nutrient addition. On the other hand, the oceanic subsurface samples showed a systematic stimulation by glucose, in one case with a concomitant positive effect of N. Expressed as percentages of the unamended controls, responses to ammonium and phosphorus additions in the different lagoons investigated appeared to decrease with increasing ammonium and phosphorus concentrations, respectively. This correspondence suggests that in situ concentrations reflect the nutrient status of bacterioplankton in the sites visited. NH4-N appeared as the most frequently stimulatory nutrient in the atolls investigated. This is in agreement with the close log-log correlation (p < 0.001) observed between bacterioplankton turnover rates and DIN/PO4 ratio. KEY WORDS: Atoll lagoon · Bacterioplankton · Nutrient limitation · Ammonium · Phosphorus Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 21, No. 2. Publication date: March 31, 2000 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2000 Inter-Research.

Photosynthetic picoplankton in French Polynesian atoll lagoons:estimation of taxa contribution to biomass and production by flow cytometry

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 162:57-70 (1998) - doi:10.3354/meps162057 Photosynthetic picoplankton in French Polynesian atoll lagoons: estimation of taxa contribution to biomass and production by flow cytometry L. Charpy1,*, J. Blanchot2 1ORSTOM, COM, Traverse de la Batterie des Lions, F-13007 Marseille, France 2ORSTOM, CNRS, Station Biologique, BP 74, F-29682 Roscoff, France *E-mail: lcharpy@com.univ-mrs.fr Picophytoplankton was studied by flow cytometry in 11 Tuamotu (French Polynesia) atoll lagoons and in the surrounding ocean. The respective contribution of Prochlorococcus, Synechococcus and picoeukaryotes on biomass and primary production was evaluated. Red fluorescence was demonstrated to be a proxy for chlorophyll. The relative sizes of the 3 picoplankton groups were estimated using forward light scattering measured in Takapoto lagoon on living cells. The average diameters for Prochlorococcus, Synechococcus and picoeukaryotes were estimated as 0.62 ± 0.08 (SD), 0.89 ± 0.09 and 3.11 ± 0.22 µm, respectively. The lowest values occurred before sunrise and the highest in the afternoon. Cellular carbon content was estimated using C/biovolume ratios from the literature. The average biomass for Prochlorococcus,Synechococcus and picoeukaryotes was calculated as 60 ± 20, 178 ± 52 and 4695 ± 834 fg C cell-1 respectively. Synechococcus formed the predominant group in terms of abundance and carbon biomass and had the highest planktonic primary production in most lagoons. As it is generally scarce in deep water with limited light availability, its biomass contribution was reduced in deep lagoons. Average lagoonal picoplankton abundance varied by a factor of 200 for the different populations and was affected by the geomorphology of the atolls. In very shallow lagoons, no general trend could be observed, as the dominant group appeared to depend on the water renewal rate within the lagoon. In the surface layer of the surrounding ocean the community structure was dominated by Prochlorococcus. However, the observed percentage of Synechococcus (>10%) is usual for the coastal zone. In the upper 120 m of ocean waters surrounding Takapoto, the integrated picoplankton biomass (1242 mg C m-2) consisted of 65% Prochlorococcus, 1% Synechococcus and 34% picoeukaryotes. Flow cytometry · Cyanobacteria · Prochlorococcus · Chlorophyll · Primary production · Atoll lagoons · Diurnal cell size variations Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 162. Publication date: February 12, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Phosphorus pathways in atolls: interstitial nutrient pool, cyanobacterial accumulation and Carbonate-Fluoro-Apatite (CFA) precipitation

Significant dissolved phosphate concentrations were measured in reef interstitial waters and in small brackish ponds (free water and underlying interstitial water) occupying the emerged rim of the Tuamotu atolls, French Polynesia. These ponds are the sites of accumulation of organic matter of pure microbial origin, in the form of thick stromatolitic cyanobacterial mats called kopara by Tuamotu natives. The profiles of dissolved phosphate interstitial waters seem to show a positive trend with depth. Within kopara, the phosphorus pathway after biological uptake is studied by measuring the C and P concentrations in raw material and in humic substances (humin, fulvic and humic acids) in order to examine the liberation of P from organic matter. For comparison, the same analysis is led on the residual organic matter of phosphate samples from Mataiva deposit (Tuamotu). The results show a relative enrichment in phosphorus with age of kopara, and a similar distribution of humic substances in kopara and phosphate samples. Other work on hydrocarbons from kopara and phosphate samples demonstrates the strong relationship of these materials. If such evolution of organic matter can be observed in kopara ponds, it should be possible to generalize to closed atoll-lagoons which function as mega kopara ponds and where phosphorus-rich layers are present (e.g., the Niau atoll). The different steps leading to atoll phosphogenesis, viewed as phosphorus sink in cyanobacterial mats to final massive CFA accumulation, could then be rationally explained. The interstitial nutrient pool can be a necessary and sufficient factor to provide phosphorus for the kopara growth and accumulation.

Particulate organic matter in sixteen Tuamotu atoll lagoons (French Polynesia)

The s t and~ng stock and chemical composition of suspended particles were monitored In 16 Tuamotu atoll lagoons and surrounding oceanic water between 1983 and 1996 Temporal and spatial variability was estimated from 18 surveys performed in Takapoto. Atoll lagoon partlculate organic matter (POM) concentrations were compared using data taken during the same months (March and November) and at the same time (morning). It appears that the lagoonal particulate organic carbon concentration depends on the latltude of each lagoon. We interpret this result as an influence of the waters deriving from the Peruvian and equatorial upwellings. Phytoplankton biomass (chlorophyll) concentration was inversely related to the water exchange between lagoon and ocean. Therefore, the best atolls for pearl oyster farming seem to be those located north of the Tuamotu Archipelago and with snlall exchange with the occan. POM concentration cvas 2 to 5 tunes higher in the atoll lagoons than in the surrounding oceanlc water, wlth a hlgher C:N ratio and a lower N:P ratio. The small size of organic particles (70 '% < 3 pm) and the low contl-ibution of phytoplankton to particulate organlc carbon (POC) (S to 19%) in the lagoons must be taken into account when calculating the potential of pearl oysters, which cannot exceed the nutritional potential of Tuamotu atoll lagoons.

Bacterioplankton Production Determined by DNA Synthesis, Protein Synthesis, and Frequency of Dividing Cells in Tuamotu Atoll Lagoons and Surrounding Ocean

This study compares three independent methods used for estimating bacterioplankton production in waters from the lagoon (mesotrophic) and the surrounding ocean (oligotrophic) of two atolls from the Tuamotu archipelago (French Polynesia).Thymidine and leucine incorporation were calibrated in dilution cultures and gave consistent results when the first was calibrated against cell multiplication and the second against protein synthesis. This study demonstrates that determining conversion factors strongly depends on the selected calculation method (modified derivative, integrative, and cumulative). These different estimates are reconciled when the very low proportion of active cells is accounted for.Frequency of dividing-divided cells (FDDC) calibrated using the same dilution cultures led to unrealistically high estimates of bacterial production. However, highly significant correlations between FDDC and either thymidine- or leucine-specific incorporation per cell were found in lagoon waters in situ. These correlations became more positive when oceanic data were added. This suggests that the FDDC method is also potentially valid to determine bacterioplankton growth rates after cross calibration with thymidine or leucine methods. If recommended precautions are observed, the three methods tested in the present study would give reliable production estimates.

Phytoplankton biomass and production in two Tuamotu atoll lagoons (French Polynesia)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 145:133-142 (1996) - doi:10.3354/meps145133 Phytoplankton biomass and production in two Tuamotu atoll lagoons (French Polynesia) Charpy L Nutrient concentrations, phytoplankton biomass (chlorophyll a, chl a) and primary production (14C uptake) were measured over a 5 yr period (1990 to 1994) in the atoll lagoons of Takapoto (4 yr water residence time; with pearl oyster aquaculture) and Tikehau (0.5 yr residence time; without pearl oyster but with a fishery), French Polynesia. In both atolls, phosphate and silicate concentrations (0.1 µM PO4 and 0.8 µM SiO2) were lower inside the lagoon than in surrounding oceanic surface waters. Picoplankton <1 µm dominated phytoplankton biomass (61%) and productivity (55%) in both lagoons. Average assimilation numbers were high (13 mg C mg-1 chl a h-1) and average chl a doubling rates of the <1 µm fraction were estimated to be 1.1 and 1.3 d-1 in Takapoto and Tikehau, respectively. Average daily primary production during the 1991 to 1994 period in Takapoto and Tikehau lagoons was estimated to be 0.8 and 0.7 g C m-2 d-1, respectively. Nutrients · Phytoplankton · Production · Pearl oyster · Atoll lagoon · French Polynesia Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 145. Publication date: December 31, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Particulate organic matter fluxes in a Tuamotu atoll lagoon (French Polynesia)

The standing stock and chemical composition of suspended particles (< 35 pm) were monitored in the lagoon of Tikehau Atoll from 1983 to 1987 and in surrounding oceanic waters (upper 250 m) during 4 cruises. Trapping rate of particulate material was measured between 1986 and 1987 and net export of particulate organic matter (POM) was roughly estimated using monthly average lagoon POM concentration and monthly average flow of water measured in the passage and the reef-flat spillways. Results showed that deep chlorophyll maxima in oceanic waters could reach 0.24 mg m-3 and were observed between 100 and 200 m even when ATP, POC, PON and POP concentrations were higher in the upper 100 m. POM concentration was homogeneous in the lagoon but varied considerably with time especially following 2 hurricanes in 1983. POM concentration was 30 to 40% higher in samples taken close to the bottom than in the water column. An oceanic station near the atoll was strongly influenced by the lagoonal discharge but POC export from the lagoon to the ocean represents only 6% of phytoplankton production. The POM content of Tikehau lagoon lies within the range recorded for coral reef areas and is made up of suspended particles 50 % of which are smaller than 5 pm. Their sedimentation (350 mg C m-' d-l) represents 80 'YO of phytoplankton production.

Anaa (Tuamotu Islands, Central Pacific): An incipient rising atoll?

The 4–5 m high raised reefs in Anaa Atoll certainly date back to the last interglacial age. The Holocene reefs, which have yielded dates between 3200 and 2000 yrs B.P., are slightly more elevated than in other Tuamotu atolls, and appear to be rising at a relative rate of about 0.1 mm yr −1. This rising trend of the island is recent and may be the result of thermal rejuvenation effected when the part of the oceanic lithosphere on which the island is situated approached the hot spot of the Society Islands.

Southwestward extent of chlorophyll-enriched waters from the Peruvian and equatorial upwellings between Tahiti and Panama

The transition zone between waters deriving from the Peruvian and equatorial upwellings, and oligotrophic waters of the Central South Tropical Pacific, was examined by sea-surface chlorophyll sampling carried out by merchant ships on the Tahiti-Panama track. The results from 118 transects (December 1979 to September 1985) show that this transition is generally associated with convergences between the westward South Equatorial Current and eastward flows, as indicated by contemporaneous temperature sections obtained from expendable bathythermographs. The transition position varies between 5 and 17 S and variations occur mostly on time scales of a month or less. The Tuamotu atolls (15 to 22 S, 135 to 150 W) were observed to be reached by waters deriving from the upwellings on 14 % of the transects; this might help to explain the anomaldus abundance of life on these atolls. The 1982-1983 El Nino resulted in a fall in chlorophyll concentrations in the Eastern Tropical Pacific, but did not cause a significant change of the position of the transition.

Seamounts as recorders of hot-spot epeirogeny

Observations in the central Pacific suggest that older seamounts are uplifted if plate motion carries them over mantle hot spots. A depth-anomaly map of the area reveals several volcanic chains now located on younger hot-spot swells. Uplift is estimated by comparing the observed depth of a seamount summit or the observed stratigraphic section in an atoll with that predicted assuming standard subsidence of the sea floor after the seamount formed. Cretaceous seamounts on the margin of the Hawaiian Swell have standard summit depths, whereas those on the crest of the swell are at least 1,100 m shallower. Summit depth correlates with sea-floor depth anomaly, implying that the Hawaiian Swell has caused the uplift. Eocene fossils are exposed at the surface in the Tuamotu Atolls, whereas, according to the standard subsidence relation, Eocene deposits should be covered by 1,000 to 2,000 m of more recent material. The inferred uplift is consistent with the atoll9s present position atop the Society Swell. Possible evidence for 600 m of uplift in the Southern Cook Islands, however, is unexplained by swell height. The observed uplifts of the Cretaceous seamounts near Hawaii and of the Tuamotu Atolls put a limit on when the Hawaiian and Society Swells formed at their present locations of maximum elevation. The swells must have developed within the past several million years and probably formed at the same time as did the younger volcanic edifices on their summits.

La vie animale terrestre à Takapoto

La vie animale terrestre à Takapoto. The author puts together the data and reports from different specialists who studied, in relation to the UNESCO MAB project "Man and Biosphere", theme 7, the terrestrial biota of the atoll of Takapoto (Tuamotu archipelago, French Polynesia). In order to describe the atoll biota, the author makes out five different habitats, and comments upon the food-cycle structures that control the relations between flora and fauna. Although the determination of all the available species is not yet over as far as entomology is concerned, it is most likely that the animals of Takapoto had a "pioneer" action. This fauna settled very recently and has an universal origin. This is in perfect harmony with the theory of the re-emerging of the Tuamotu atolls. The animal and vegetal species are now spreading over Takapoto, mainly from the Australian and Asian regions, most often via Tahiti. However, due to the fast-developing continent to continent means of conveyance in the Pacific, the latest species that have reached the island may originate from farther countries. But for birds perhaps, the speciation does not seem, up to now, to have developed into new species adapted to the archipelago as it is the case for neighbour high islands like Tahiti or the Marquesas. The inhabitants of Takapoto can only live on and hold out by fulfilling their needs mainly with sea and lagoon products rather than very poor terrestrial ressources. Joining in the modern economic systems, the Paumotu — i.e. the inhabitant of the Tuamotu archipelago — will meet a difficult issue as for the ecology of those South Pacific atolls. The ecosystems of the Tuamotu archipelago enjoy a stable equilibrium, but they are far more fragile than any other because of their very poor ecological diversity.

Macrobenthos and Meiobenthos from the Closed Lagoon of a Polynesian Atoll. Maturei Vavao (Tuamotu)

A bottom faunal study was undertaken in the lagoon of a Tuamotuan closed atoll. Sediments from five stations located along a transect from the inner lagoon margin to the lagoon center were collected by skin or SCUBA diving. Macroand meiobenthic faunal assemblages were studied in relation to hydrodynamic conditions, depth and sediment composition, and grain size. The macrofauna community is homogeneous throughout the lagoon floor including the molluscs Pinctada inaculata, Chama imbricata, Arca plicata, and A. ventricosa, and the echinoderm Halodeima atra, all of which occur in great numbers. Tridacna maxima is restricted to shallower waters and Pinna muricata to deeper, finer sediments. Meiofauna abundance increases with depth, fineness of sediment, and higher organic-matter content. Diversity is higher in shallow water stations and is greatly reduced at maximum depth (40 mi). Food interrelationships between macroand meiofauna are demonstrated by Halodeima atra which ingests a large amount of meiofauna, other macrofauna components being filter feeders. Predaceous species of the meiofauna occur in larger numbers in coarser shallow sediments, but as a whole most of the meiofauna components are deposit-feeders with the exception of molluscan larvae. Faunal assemblages, abundance, and diversity are compared to those of an open atoll lagoon (Mururoa, Tuamotu); different species distributions are discussed in relation to differing hydrodynamic conditions occurring in both types of lagoon. THE SYSTEMATIC SURVEY of the marine benthic fauna of the southern Pacific islands was initiated by the Singer-Polignac Foundation in 1960-1961. It sponsored expeditions to New Caledonia. From the results of Salvat's sampling and investigations of Saint Vincent Bay (New Caledonia) many papers were issued. Works on bottom sediments included papers on both macrofauna (Salvat 1964, 1965) and meiofauna (Delamare Deboutteville and RenaudMornant 1966, Higgins 1967, Inglis 1967, Laubier 1967a,b, Renaud-Debyser 1965, Renaud-Mornant 1967, Coineau 1970, and Jouin 1970. Lately, interest has turned to the atolls of the Tuamotu area, and scientific expeditions were made possible through the sponsorships of both the des Centres d'Experimentations Nucleaires, Service Mixte de Controle Biologique and the National Museum of Natural History, Paris.' Recent studies and observations of Polynesian atolls, mainly in the Tuamotus, have led to the distinction of two types of atolls occurring in this region. Their main characteristic is the presence or 1 Publication number S.ll after agreement between Direction Centre Experimentations Nucleaires and Museum-Mission III. absence of navigable passage through the reef into the lagoon. The lagoon of an open atoll is constantly exchanging waters with the open sea through one or several wide channels or deep passes, while a closed lagoon is more or less completely isolated from the ocean waters by continuous island formation. Some shallow inner-islet channels, called hoa by the natives, might be present but their depth never exceeds two meters. Through them, at high tide, ocean water is brought intermittently to the lagoon by the flood. The volume of water entering the lagoon is significantly affected by seasonal winds and ocean currents. The confinement or the constant renewal of the lagoon water is an important factor controlling the establishment and the distribution of marine forms throughout the lagoon. In his general survey of the molluscan fauna of the Tuamotu atolls, Salvat (1967) has pointed out the great disparity in the faunal community distribution in these two types of atolls. In a recent work (Salvat and Renaud-Mornant 1969) the present authors have made an attempt to evaluate the amount of macroand meiobenthos living in the deeper sediments of the Mururoa lagoon. This lagoon is surrounded by an open atoll having a wide passage on its leeward side. 36 BIOTROPICA 3(1): 36-55 1971 This content downloaded from 157.55.39.181 on Thu, 29 Sep 2016 04:13:48 UTC All use subject to http://about.jstor.org/terms To date no work has been done on the distribution of macroand meiobenthic populations in the lagoon sediment of a closed atoll. The study of the closed Maturei Vavao lagoon could bring valuable information on atoll ecology and faunal quantitative composition. The sampling of the lagoon was made by B. Salvat by skin or SCUBA diving and allows for an adequate quantitative survey of the fauna living on the surface layer and inside the upper centimeters of the sediments.