Variations In Environmental Parameters Research Articles

Lack of seasonal variation in the life-history strategies of the trematodeCoitocaecum parvum: no apparent environmental effect

Parasites with complex life cycles have developed numerous and very diverse adaptations to increase the likelihood of completing this cycle. For example, some parasites can abbreviate their life cycles by skipping the definitive host and reproducing inside their intermediate host. The resulting shorter life cycle is clearly advantageous when definitive hosts are absent or rare. In species where life-cycle abbreviation is facultative, this strategy should be adopted in response to seasonally variable environmental conditions. The hermaphroditic trematode Coitocaecum parvum is able to mature precociously (progenesis), and produce eggs by selfing while still inside its amphipod second intermediate host. Several environmental factors such as fish definitive host density and water temperature are known to influence the life-history strategy adopted by laboratory raised C. parvum. Here we document the seasonal variation of environmental parameters and its association with the proportion of progenetic individuals in a parasite population in its natural environment. We found obvious seasonal patterns in both water temperature and C. parvum host densities. However, despite being temporally variable, the proportion of progenetic C. parvum individuals was not correlated with any single parameter. The results show that C. parvum life-history strategy is not as flexible as previously thought. It is possible that the parasite's natural environment contains so many layers of heterogeneity that C. parvum does not possess the ability to adjust its life-history strategy to accurately match the current conditions.

Environmental parameters that determine species geographical range limits as a matter of time and space

AbstractAim To identify the ecological factors associated with the range borders of two amphibian species, to investigate geographical variation in environmental parameters that determine species range limits, and to develop a testable hypothesis on the species’ biogeographical history.Location Portugal and Spain.Methods We documented the distribution of two species of marbled newt (Triturus marmoratus and Triturus pygmaeus) from atlas data, survey data and six latitudinal transects. Countrywide ecogeographical models were constructed from presence‐only data and a suite of 19 environmental parameters. Local ecogeographical models were constructed along the contact zone.Results Triturus marmoratus and T. pygmaeus share a parapatric range border from coastal Portugal to central Spain. Ecogeographical models performed better in descriptive mode (for the country where they were developed) than in predictive mode (when extrapolated for the neighbouring country). This suggests the existence of spatial variation for parameters that determine the species range borders. Local models showed good performance in Spain and western Portugal. Parameters dominating the models were climatic (precipitation, temperature and solar radiation), geographical (altitude) and geophysical (soil permeability). Enclaves in the distribution of T. marmoratus/T. pygmaeus also corresponded with environmental parameters. Poor‐fitting local models were found in central Portugal, where the mutual range border of the two species coincides with the River Tejo.Main conclusions The fit and predictive performance of the ecogeographical models suggest that equilibrium conditions have been reached over most of the contact zone. Parameter selection, field observations and natural history knowledge led us to identify, in terms of reproductive strategy, a stable species with regular, but low annual recruitment (T. marmoratus) vs. an opportunistic species with fluctuating ‘all‐or‐nothing’ annual recruitment (T. pygmaeus). Ecological parapatry derives from the use of permanent ponds for breeding in T. marmoratus vs. ephemeral ponds used by T. pygmaeus. Enclaves in the distribution show that, historically, T. pygmaeus has been displacing T. marmoratus. In central Portugal, where the model fit is poor, the advance of T. pygmaeus is currently impeded by the River Tejo. We predict that once this barrier has been crossed, the contact zone will move c. 40 km to the north. As T. marmoratus and T. pygmaeus are hybridizing species, we predict the occasional presence of T. marmoratus genes in areas that have changed occupancy.

Lifetime reliability based design of an offshore vessel mooring

Moored floating vessels offer an attractive solution to oil and gas recovery in a range of water depths. The design of moorings for these compliant vessels require careful prediction of the lifetime response extremes. Reliability based predictions offer more accuracy than prescriptive schemes but at a higher computational expense: existing tools are in need of some improvement. Here a frequency-domain response model is coupled with a pseudo-asymptotic integration scheme to provide a rapid estimate of lifetime reliability and hence the extreme response at a design target level. The potential lifetime environmental and system parameter variation is consistently included. Reliability bounds and an associated convergence criteria are also defined. This methodology is tested on a representative FPSO in a wave-dominated environment. A comparison with traditional single-storm design methods highlights a significant variation in the 100-year excursion response. The convergence of bounds on the lifetime reliability at target levels consistent with existing design codes is shown. The provision of additional design information as a byproduct of the pseudo-asymptotic analysis is demonstrated.

Bacterivory in the common foraminifer Ammonia tepida: Isotope tracer experiment and the controlling factors

The majority of sediment dweller foraminifera are deposit feeders. They use their pseudopodia to gather sediment with associated algae, organic detritus and bacteria. Uptake of bacteria by foraminifera have been observed but rarely quantified. We measured uptake of bacteria by the common foraminifera Ammonia tepida using 15N pre-enriched bacteria as tracers. In intertidal flats, seasonal, tidal and circadian cycles induce strong variations in environmental parameters. Grazing experiments were performed in order to measure effects of abiotic (temperature, salinity and irradiance) and biotic (bacterial and algal abundances) factors on uptake rates of bacteria. In mean conditions, A. tepida grazed 78 pgC ind − 1 h − 1 during the first eight hours of incubation, after which this uptake rate decreased. Uptake of bacteria was optimal at 30 °C, decreased with salinity and was unaffected by light. Above 7 × 10 8 bacteria ml wt sed − 1 , uptake of bacteria remained unchanged when bacterial abundance increased. Algal abundance strongly affected algal uptake but did not affect uptake of bacteria. As uptake of bacteria represented 8 to 19% of microbes (algae plus bacteria) uptake, Ammonia seemed to be mainly dependant on algal resource.

Adaptive model-following control for slim voice coil motor type optical image stabilization actuator

An autofocusing optical image stabilization actuator (AFOISA) will become standard equipment quickly in megapixel resolution mobile phone cameras (MPCs). A slim AFOISA composed of two orthogonal directions has been developed based on magnetic analysis and it is an effective solution to address image quality of a charged coupled device to compensate 10–20Hz hand jitter in taking photos. However, environmental disturbance often occur irregular shake, such as when a photographer holds a MPC while walking or in a vehicle. Therefore, this paper develops an adaptive model-following control (AMFC) law including two proportional-integral-derivative controllers with position and speed feedback control, which is shown to be able to compensate for irregular shake of MPCs and to obtain fast response. Although irregular environmental shake cause parameter variation, an adaptation mechanism synthesizes an auxiliary input signal to assure that an AFOISA plant exactly behaves as a reference model. The time response by utilizing AMFC includes 30ms settling time and 5μm steady state error without any overshoot. Furthermore, a compensatory force can quickly cancel irregular disturbance. As a result, the present slim AFOISA satisfies the optical demands of MPCs.

How to measure uncertainties in environmental risk assessment

Environmental risk assessment is an essential element in any decision-making process in order to minimize the effects of human activities on the environment. Unfortunately, often environmental data tends to be vague and imprecise, so uncertainty is associated with any study related with these kind of data. Essentially, uncertainty in risk assessment may have two origins – randomness and incompleteness. There are two main ways to deal with these uncertainties – probability theory and fuzzy logic. Probability theory is based on a stochastic approach, using probability functions to describe random variability in environmental parameters. Fuzzy logic uses membership functions and linguistic parameters to express vagueness in environmental issues. We discuss the best way to deal with uncertainties in the environmental field and give examples of probabilistic and fuzzy-logic approaches applied to environmental risk assessment.

Temperature-Induced Changes in Structural and Physicochemical Properties of Vernix Caseosa

The skin of the third trimester fetus and early newborn exhibits a complex, multifunctional, highly hydrated but viscous skin-surface biofilm called vernix caseosa (VC). During birth, VC undergoes a substantial change from an aqueous and warm surrounding into a gaseous and colder environment postnatally. The aim of this study was to investigate the structural and physicochemical changes in VC, which accompany physiologically relevant variations in environment parameters, such as temperature and humidity. A remarkable difference was observed in water release and uptake properties: dehydration and rehydration processes take place two to four times faster at 37 degrees C than at room temperature (RT). The dehydration was irreversible; rehydration was only possible to a final weight of 55% (37 degrees C) and 46% (RT) of the pre-desiccation weight. Differential scanning calorimetry showed two different overlapping phase transitions within physiological temperature range. Investigation of the lipid organization by Fourier transform infrared spectroscopy and small-angle X-ray diffraction revealed a more disordered state of lipids at 37 degrees C than at RT, which might explain the faster dehydration and rehydration process at 37 degrees C as well as the changes in thermotropic rheological behavior. In conclusion, we demonstrated that VC properties adjust to the fundamental change from the intrauterine to the post-natal environment.

Environmental causes of the fluctuations of red shrimp ( Aristeus antennatus) landings in the Catalan Sea

The fluctuations of catches of the deep-sea shrimp Aristeus antennatus (Risso, 1816) were analysed in the 6 ports of Catalonia where production is concentrated, based on monthly landings from 1988 to 2004. The 6 selected ports produced 300 t of red shrimp in 2004, or 80% of the total production in Catalonia. The series for each port showed clear interannual variability, with peaks of production in the early 1990s and more recently from 2001 to 2003. The time periods of the monthly data series, estimated by frequency analysis based on Fourier transform, varied around 7–8 years in the four central ports and 12–13 years in the two northern ports. Additionally, the different curves were not in phase: even in nearby ports, the maximum production is observed in different years. Since the North Atlantic Oscillation (NAO) index is an excellent proxy for long-term series of environmental variables, we aimed to explore relationships between the fluctuation of the NAO index and A. antennatus landings in the Catalan Sea. The correlation between the mean annual NAO index and the annual catches in each port was positive and significant with some time lags (from 1 to 3 years). The existence of clear patterns linking the NAO with marine ecological processes has been demonstrated in many studies, but the underlying ecological mechanisms are far from being well understood. The variations in environmental parameters linked to the NAO may act on biological organisms at different levels (individual, population) through physiology (metabolic and reproductive processes) or through trophic relationships, including ecological cascade effects. We propose that NAO-induced environmental variability may enhance food supply to A. antennatus and hence strengthen the reproductive potential of particular year classes, which result in increased catches 1 to 3 years later, although other possible effects of environmental variability on the population dynamics of this species are worth investigating.

Ameisen als Schlüsseltiere in einem Grasland—Studien zu ihrer Bedeutung für die Tiergemeinschaft, das Nahrungsnetz und das Ökosystem (Ants as Keystone Species in a Dry Grassland: Studies of their Importance for Animal Community, Food Web and Ecosystem Function), C. Platner. Biodiversity and Ecology Series 1. Universitätsverlag Göttingen (2006). 170pp., €16, ISBN:978-3-938616-05-5.

Fish communities are an important cultural, recreational and commercial resource that also have an important role in the functioning of marine ecosystems. Around the world fish assemblages are experiencing pressures from anthropogenic activities, and marine spatial planning is being established to mitigate these impacts and assist with biodiversity conservation. Information about how fish assemblages are structured across a range of spatial scales which encompass variations in physical, biotic and environmental parameters will assist marine spatial planning and management. We investigated differences in reef fish assemblage composition over three reef lines across an inshore to offshore gradient (3–23 m depth) at two marine reserves (70 km apart) in the Perth metropolitan region, Western Australia. There were significant increases in the number of individuals, species richness, and relative abundance of fish species across the shallow shelf depth gradient in the two locations. There were distinct fish assemblages associated with each reef line, correlated to depth and distance from shore. The differences across the shelf gradient, even over this small depth range, were greater than the differences between the two locations. These findings have implications for marine spatial management and the design of marine reserves that aim to conserve biodiversity. It may be most appropriate for such marine reserves to encompass a wide depth gradient, rather than a large longshore area. At the very least, cross and longshore patterns in fish assemblages should be taken into consideration and used to guide spatial management plans for biodiversity conservation.

Faecal Coliforms in Bivalve Harvesting Areas of the Alvor Lagoon (Southern Portugal): Influence of Seasonal Variability and Urban Development

Faecal coliform (FC) levels in surface water and clams (Ruditapes decussatus) and variations in environmental parameters were studied in two bivalve harvesting areas in the Alvor lagoon (southern Portugal). Land use and cover characteristics in adjacent subwatersheds were also analysed to assess their contributions as sources of faecal contamination. High FC levels in clams from the harvesting area in the most urbanized subwatershed (impervious surface coverage approximately 10.5%) were positively associated with rainfall and with the cooler periods of the year. FC levels in clams from the least urbanized subwatershed were generally very low and did not present any detectable seasonal trend. From these results, it was concluded that the periodic deterioration of the microbiological quality of clams derives from the cumulative impact of the reservoir of faecal contamination created in urbanized areas, entering into the lagoon during storm water runoff.

Proceedings of the Fifth Circumpolar Ecosystems Conference and Workshop, Churchill, Manitoba, Canada, February 2004—introduction

During February 2004, we co-chaired the Fifth Circumpolar Ecosystems Conference and Workshop, hosted by the Churchill Northern Studies Centre (CNSC). More than 50 international participants traveled to Churchill for this meeting, which originated as part of the CNSC mandate of arctic research and education. In 1989, Peter Scott organized the first CNSC-hosted meeting under the banner ‘‘Circumpolar Ecosystems in Winter.’’ At high latitudes, winter can be the dominant season that drives many physical and biological processes. Understanding these winter processes is critical in the context of climate change, and yet few researchers are actively studying environmental processes during winter. One of the purposes of these Churchill meetings was to address the need to increase winter research. This was obvious when the mandate of the meetings had to be expanded to include results of research in seasons other than winter to fill the program. For the Fifth Circumpolar Ecosystems Conference we chose to continue the field science theme for the workshop by focusing on ‘‘snow sampling methodology and instrumentation.’’ Here participants had the opportunity to examine a wealth of traditional and newer technologies available to measure snow cover characteristics at a variety of scales. The second aspect of the meetings was the presentation and publication of a collection of scientific papers. The theme for the symposium was ‘‘Northern Margins: Changing Transition Zones in Time.’’ The range of papers for this symposium reflects the wide range of interest in the transitional zones that occur throughout the circumpolar north— forest-tundra, fast ice–pack ice, continuous-discontinuous permafrost, snowpack temperature gradients, and snowpack melt, to name a few. The three papers included here characterize the diversity of topics covered in the symposium. Two papers highlight research in the northern treeline transition zone in the Churchill area, focusing on snowpack variation in one case, and revegetation methods in the other. The third paper demonstrates the importance of latitudinal variation in environmental parameters on marine food webs. The meeting was sponsored by Campbell Scientific Canada Corporation; Parks Canada; Clayton H. Riddell Faculty of Earth, Environment and Resources, University of Manitoba; Enviro-Test Laboratories; University of Winnipeg; Brandon University; Eskimo Museum; Town of Churchill; Manitoba Conservation; Inter-Universities North (now University College of the North); and the Churchill Northern Store. We thank the sponsors and the residents of Churchill and CNSC staff for their support and cooperation in this endeavor. Plans for the Sixth Circumpolar Ecosystems in Winter Symposium will be announced following the summer of 2007 as the CNSC has embarked on a facility renewal campaign that will result in a new research center. The proposed date of February 2009 will give the CNSC a chance to showcase their new facility by highlighting results of the 2007–2008 International Polar Year.

What environmental fate processes have the strongest influence on a completely persistent organic chemical's accumulation in the Arctic?

Fate and transport models can be used to identify and classify chemicals that have the potential to undergo long-range transport and to accumulate in remote environments. For example, the Arctic contamination potential (ACP), calculated with the help of the zonally averaged global transport model Globo-POP, is a numerical indicator of an organic chemical's potential to be transported to polar latitudes and to accumulate in the Arctic ecosystem. It is important to evaluate how robust such model predictions are and in particular to appreciate to what extent they may depend on a specific choice of environmental model input parameters. Here, we employ a recently developed graphical method based on partitioning maps to comprehensively explore the sensitivity of ACP estimates to variations in environmental parameters. Specifically, the changes in the ACP of persistent organic contaminants to changes in each environmental input parameter are plotted as a function of the two-dimensional hypothetical “chemical space” defined by two of the three equilibrium partition coefficients between air, water and octanol. Based on the patterns obtained, this chemical space is then segmented into areas of similar parameter sensitivities and superimposed with areas of high default ACP and elevated environmental bioaccumulation potential within the Arctic. Sea ice cover, latitudinal temperature gradient, and macro-diffusive atmospheric transport coefficients, and to a lesser extent precipitation rate, display the largest influence on ACP-values for persistent organic contaminants, including those that may bioaccumulate within the polar marine ecosystems. These environmental characteristics are expected to be significantly impacted by global climate change processes, highlighting the need to explore more explicitly how climate change may affect the long-range transport and accumulation behavior of persistent organic pollutants.

Quality and quality changes during refrigerated storage in diploid and triploid oysters from Orbetello Lagoon (Italy)

The aim of this study was to evaluate the chemical and nutritional characteristics and quality decay during storage of diploid and triploid Pacific oysters (Crassostrea gigas) reared in Orbetello Lagoon (Grosseto, Italy), a site subject to high variations in environmental parameters. Specimens of diploid (D) and triploid (T) oysters of commercial size and similar age were sampled from an oyster farm (Soc. Coop. GIGAS) in autumn 2005 and in winter, spring and summer 2006. At each sampling date, D (n=60) and T (n=60) oysters were individually weighed, divided into 4 lots, stored under refrigerated conditions (+4°C), and analysed at different times after harvest (1, 3, 7 and 10 days). Oysters were individually weighed again at the different times, measured for maximum length, width and thickness, and opened. The weight of the soft part and shell and the volume of intervalvar liquor were recorded. pH of soft part, gill and mantle colour (CIE L*, a* and b*, Minolta Chromameter) and chemical characteristics (proximate and quantitative fatty acid composition in pooled samples) of soft parts were also analysed. Turbidity of intervalvar liquor was evaluated (by spectrophotometer). A total of 480 specimens (D+T) was studied. For morphological data, the model utilised for the statistical analysis (PROC GLM of SAS Software) included ploidy, season and their interaction as fixed effects; for parameters analysed during storage, the model included ploidy, storage time, season and the interaction between ploidy and storage time. Triploid oysters had greater average (p<0.001) length (102.1 vs 95.7mm), thickness (34.3 vs 28.4mm) and weight (99.3 vs 77.2g) than those diploid. The latter oysters had an inferior market value due to lower economic condition index [thickness/(0.5*(length+width)] (0.38 vs 0.45; p<0.001) and soft part percentage (8.20 vs 12.04%; p<0.001). Differences were also found in chemical characteristics: T showed greater average (p<0.001) dry matter (19.07 vs 14.90%), crude protein (9.47 vs 7.90% w.w.) and total lipid (1.71 vs 0.91%) contents and higher (p<0.01) percentages of C20:5n3 (10.36 vs 8.18%) and PUFAn3 (35.57 vs 28.15%), and lower MUFA (17.72 vs 19.73%; p<0.01) percentage. During storage, T had a higher average weight to length ratio (0.94 vs 0.74; p<0.001), lower weight loss percentage (8.84 vs 10.10%; p<0.05) and higher turbidity of intervalvar liquor (0.754 vs 0.394 absorbance units; p<0.001). T and D differed in colour, T having higher whiteness (L*) and yellowness (b*) of gills and mantle and lower redness (a*) of mantle. Certain parameters reliably reflected changes in oyster quality during storage: percentage weight loss increased significantly from 0% to 12.42% on days 1 and 10, respectively, like pH (days 1-3: 6.19-6.21; day 7: 6.34; day 10: 6.57; p<0.001) while weight/length ratio decreased (from 0.88 to 0.77 on days 1 and 10, respectively; p<0.05). Colour parameters did not change. During storage, trends of parameters were similar in D and T, the interaction between ploidy and storage time never reaching significance. In conclusion, the results confirmed that like D and T oysters from other areas, those from Orbetello Lagoon differ in market and chemical characteristics. The parameters analysed during storage demonstrated the poor average quality of diploid oysters. Further investigations are needed to elucidate the influence of season, which significantly affected almost all the quality parameters analysed, and to highlight the relation between season and quality decay during storage.

High through‐put screening method for novel and circadian movement behavior and breathing in ENU mutagenic and consomic inbred strains of rats

The objective was to develop a high throughput method of screening novel and circadian movement behavior and breathing phenotypes in consomic and ENU knockout rats. The system developed consisted of 12 plethysmographic chambers with continuous airflow (3 L/min) to maintain ambient, continuously monitored conditions. While breathing was measured using standard plethysmographic methods, movement was acquired using horizontal and vertical sensors (VersaMax, Accuscan Inc). The rats were exposed to 12 hrs lights ON (0800 hrs) and 12 lights OFF (2000 hrs) schedule with food and water were continuously available. The protocol began at 1200 hrs on the 1st day and continued until the morning of the 4th day at which time a 10 min hypercapnic challenge was performed. The protocol was divided into Novel (1st 2 hours) and Adapted periods (remaining lights OFF and On periods). A total of 22 phenotypes are acquired. After initial testing and over 15 studies, the system maintains ambient conditions (FIO2 > 19.5%, FICO2 < 0.3%) with expected circadian variation in environmental parameters (e.g., chamber temperature). Examination of movement and breathing signals revealed a sustained high quality signal with minimal loss of data. These findings demonstrate this system will be effective in detecting differences in complex traits that can be further dissected into their genetic and molecular mechanism. This study was funded by NHLBI (U01 HL66579)

Radical past climatic changes in the Arctic Ocean and a geophysical signature of the Lomonosov Ridge north of Greenland

The Arctic Ocean is a landlocked basin, at present covered by perennial sea ice. During the past few decades a significant thinning and shrinking of the sea ice has been observed, and modelling studies indicate that the Arctic Ocean ice cover could, by the end of this century, almost disappear from most parts of the Arctic Ocean during peak summer seasons. It remains uncertain, however, whether the environmental changes are an enhanced greenhouse-warming signal or a result of natural (long-term) variability, but palaeoceanographic studies can contribute to our understanding of the natural variability of environmental parameters, e.g. sea-ice cover and oceanographic changes on time-scales of centuries to millennia. As part of the multidisciplinary EU project Greenland Arctic Shelf Ice and Climate Experiment (GreenICE), sediment coring and seismic reflection measurements have been undertaken in a hitherto unexplored part of the Arctic Ocean, the margin of the Lomonosov Ridge in the Lincoln Sea (Fig. 1). The aim of the project was to study the structure and dynamics of the sea-ice cover and attempt to relate these to longer-term records of climate variability retrieved from sediment cores. The main field work was carried out in May 2004 from an ice camp established by a Twin Otter aircraft on drifting sea ice at 85°N, 65°W, c. 170 km north of Alert, Arctic Canada. The camp was deployed over the shallowest part of the Lomonosov Ridge off the northern Greenland/Canada continental margin (Fig. 1). The sea-ice drift would normally be between east and south, but persistent easterly winds resulted in a fast drift trajectory towards the WSW, such that the camp drifted a distance of approximately 62 km during the two weeks camp period. At present the study area is heavily ice covered, and forecast models of future shrinking Arctic sea-ice cover suggest that this area is one of the least sensitive to warming in the Arctic. The results obtained from the GreenICE project challenge this view.

Egg production of the copepod Acartia hongi in Kyeonggi Bay, Korea

Many studies of copepod egg production have shown that food availability and temperature are major factors that influence copepod growth. However, coastal environments are complicated ecosystem and the relationships between growth of copepods and influencing factors are not always clear in nature. We conducted a study along an inner–middle–outer bay transect where variations in environmental parameters would be expected to affect the biomass and egg production rate of A. hongi from February 2001 to December 2001. In this study, we investigated the abundance and biomass with developmental stages and egg production rates of A. hongi in relation to various environmental factors. The copepod A. hongi occurred continuously throughout the year, with a peak abundance in May. In general, the variation in egg production rates showed a similar tendency with the variations in chlorophyll- a throughout the study period. This suggests that phytoplankton biomass is an important factor that affects the egg production of A. hongi. In addition, during the warm season, the egg production of A. hongi was also influenced by the ciliates abundance in the middle and outer bay. Consequently, the egg production of A. hongi is generally affected by food availability in Kyeonggi Bay.

Effects of fish farming on flavonoids in Posidonia oceanica

This work is a first approach to flavonoid responses (total proanthocyanidins and total and simple flavonols) in Posidonia oceanica in function of nutrient enrichment (aquaculture activities — fish farming), in the western Mediterranean Sea (Calvi–Corsica–France). The first result is the presence of total and simple flavonoids in P. oceanica. The second result shows an increase in total proanthocyanidin and total flavonol concentrations near cages, which would be linked to the high grazing pressure induced by meadow enrichment. Concerning simple flavonols, only quercetin shows a response to fish farming, which could be due to its strong antioxidant capacity. The presence of fish farming, which causes variations in environmental parameters, could affect the functioning of P. oceanica meadows. Flavonoid concentrations in P. oceanica seem to be a possible bioindicator of nutrient enrichment for the management of the littoral environment.

Ivy (Hedera helixL.) Flower Nectar and Nectary Ecophysiology

The nectary of Hedera helix is situated above the inferior ovary and completely exposed to the external environment. It consists of parenchyma containing chlorophyll overlying vascular bundles with xylem and phloem. The nectar exudes from stomata. Nectary color varied from green to brown during the flowering period (mid‐September to early November). This change in color resulted from accumulation of anthocyanins in subepidermal layers of the parenchyma. Quantitative differences were observed in the photosynthetic pigments of nectaries and leaves. Their quantitative variations, associated with variation in environmental parameters (temperature and rainfall) during flowering, were different in the two organs: the quantity of photosynthetic pigments increased in leaves at the end of flowering, whereas an increase principally in β‐carotene was observed in nectaries, suggesting that the nectary protected the inferior ovary from sunlight. Nectar was produced in greater abundance but with lower sugar concentration at the start of flowering, but the total quantity of sugars it contained did not vary significantly during flowering. The relative concentration of sugars showed slight variations that were not associated with significant changes in pollinators, which were mainly bees and flies.

Refraction of Sound in a Horizontally Inhomogeneous, Time-Dependent Ocean

Measurements of the three-dimensional (3-D) structure of a sound-speed field in the ocean with the spatial and temporal resolution required for prediction of acoustic fields are extremely demanding in terms of experimental assets, and they are rarely available in practice. In this study, a simple analytic technique is developed within the ray approximation to quantify the uncertainty in acoustic travel time and propagation direction that results from an incomplete knowledge or purely statistical characterization of sound-speed variability in the horizontal plane. Variation of frequency of an acoustic wave emitted by a narrowband source due to a temporal variation of environmental parameters is considered for deterministic and random media. In a random medium with locally statistically homogeneous, time-dependent 3-D fluctuations of the sound speed, calculation of the signal frequency and bearing angle variances as well as the travel-time bias due to horizontal refraction is approximately reduced to integration of respective statistical parameters of the environmental fluctuations along a ray in a background, range-dependent, deterministic medium. The technique is applied to acoustic transmissions in a coastal ocean, where tidally generated nonlinear internal waves are the prevailing source of sound-speed fluctuations, and in a deep ocean, where the fluctuations are primarily due to spatially diffuse internal waves with the Garrett-Munk spectrum. The significance of 3-D and four-dimensional (4-D) acoustic effects in deep and shallow water is discussed

Variability of Ruppia cirrhosa in two coastal lagoons with differing anthropogenic stresses

The dynamics of Ruppia cirrhosa were studied over two years in two coastal lagoons on the Corsican coast (France, Mediterranean Sea). The lagoons differed in type of eutrophication: (1) Biguglia lagoon (urban and industrial effluent, agriculture, runoff from catchment area) and (2) Santa Giulia lagoon (tourist pressure in summer). Spatio-temporal variability of R. cirrhosa occurrence was monitored on permanent transects. We also monitored temporal changes in density, aboveground/belowground biomass and organic matter. Most of the parameters studied along the transects show variations with season and site. Density and aboveground biomass of R. cirrhosa in Biguglia lagoon were lower when Ulva species were present. This may be related to differences in nutrient availability. During the first year of the study, rainfall was greater with concomitantly higher nutrient inputs, which may account for the higher values of measured parameters in the first year. The results suggest that environmental parameter variations affect the functioning of R. cirrhosa meadows.