Energetics of underwater swimming in the great cormorant (Phalacrocorax carbo sinensis)

Resting metabolic rate (RMR), energy requirements and body core temperature were measured during underwater swimming in great cormorants (Phalacrocorax carbo sinensis) at the zoological garden in Neumünster, Germany, using gas respirometry and stomach temperature loggers. We used a 13 m long still water canal equipped with a respiration chamber at each end. Birds swam voluntarily in the canal at a mean speed of 1.51 ms^-1. Power input during underwater swimming averaged 31.4 W kg^-1. Minimal costs of transport of 19.1 J kg^-1 m^-1 were observed at a speed of 1.92 m s^-1. Body core temperature was stable in all birds within the first 60 min spent in the canal. After that, body temperature dropped at a rate of 0.14°C min^-1 until the birds voluntarily left the water. Our data indicate that great cormorants spend 2.7 times more energy than Adélie penguins (Pygoscelis adeliae) during underwater swimming. This can be essentially attributed to their poor insulation, their mode of locomotion underwater and differences in streamlining. RMR on land was related to body mass via VO₂=0.691 M^0.755 (where VO₂ is O₂-consumption in litre h^-1 and M is body mass in kg). In order to quantify the effects of external devices on energy consumption during underwater swimming, we tested a dummy data logger attached to the back of the cormorants as well as a ring on the leg. The ring had no apparent influence on the swimming energetics of the cormorants. In birds equipped with dummy loggers, swimming speed was not significantly influenced, but both power input and costs of transport increased by a mean of 19% for swimming speeds between 1.4 and 1.8 m s^-1.     

Environmental determinants of distribution and foraging behaviour of cormorants (Phalacrocorax spp.) in temperate estuarine habitats

The distribution and behaviour of cormorants in estuarine environments was examined on the central coast of New South Wales, Australia, with respect to habitat associations at different spatial scales. No consistent variation in abundance was found for four species of cormorants (great Phalacrocorax carbo, pied P. varius, little black P. sulcirostris, and little pied P. melanoleucos) with state of tide (high and low) and time of day (early, middle, and late) at five estuarine locations. Differences in abundance were found among locations that were not confounded by short-term temporal variation (i.e. time of day and tide). Differences in abundance were detected among habitats (e.g. bays, creeks, and headlands) separated by hundreds of metres to kilometres in different estuaries. Cormorants of all species were rare on the open coast and near the entrance of estuaries. Abundances of cormorants varied greatly within and among creeks, bays, and river channels. Presence of seagrass beds explained much of this variation and most of the cormorants swimming and feeding were found near seagrass. Mapping of seagrass beds and the positions of cormorants at scales of metres to hundreds of metres showed a close relationship between the presence of swimming and roosting beds and the presence of seagrass beds for P. melanoleucos and for P. carbo. We argue that cormorants make decisions to visit particular estuarine habitats, especially those with seagrass, where many types of prey (e.g. fish and crustaceans) are probably most abundant. These choices must be interpreted in the context of decisions that cormorants make on scales of hundreds to thousands of kilometres during periodic excursions to the interior of Australia. Further, environmental threats to seagrass beds could impinge on these mobile visitors to the same extent as on more permanent residents. Received: 14 February 2000 / Accepted: 17 July 2000     

Phosphate solubilizing actinomycetes in the estuarine environment: an inventory.

Sediment samples were collected from different stations of the Vellar estuary for isolation of total actinomycetes and phosphate solubilizing actinomycetes. Phosphatase activity in the sediments was also investigated Consistently a higher number of actinomycetes, phosphate solubilizing actinomycetes and phosphatase activity were recorded from the clay sediments than the sandy sediments at all the stations. In all, 7 strains showed positive phosphatase activity. Among them, one strain PS-3 exhibited good activity and was further investigated for optimum phosphorus solubilization at different pH (6, 6.5, 7, 7.5 and 8) and incubation (1st day to 20th day) periods. The solubilizing activity was maximum at the pH 7 and an incubation period of 13 days was required for an appreciable quantity of phosphorus to be leached into the medium. Based on the chemotaxonomical and conventional methods of identification, the strain PS-3 has been tentatively identified as Streptomyces galbus. The present study indicates that phosphatase enzyme and S. galbus along with other actinomycetes species would play a major role in solubilizing the phosphate in the estuarine ecosystem and increasing the soluble phosphate concentration thereby enhancing the productivity     

Comparison of bacterial and algal utilization of orthophosphate in an estuarine environment

Bacterial utilization of orthophosphate in an estuarine environment has been differentiated from algal utilization by using flow-filters of 5.0, 1.2 and 0.45 m poresize. Examination by light microscopy showed that most of the bacterial population passed through a 5.0-m filter, whereas most algae were retained. In all experiments, bacterial and algal cell numbers and biomass were estimated. P-uptake by algae and bacteria was closely correlated with cell biomass. P-uptake by algae was high only in the summer months, whereas P-uptake by bacteria was high throughout the year. Neither algal nor bacterial P-uptake, however, was correlated with temperature or dissolved orthophosphate, total organic phosphate or total phosphate concentrations. Cell biomass of algae at a given time had a high correlation with dissolved organic phosphate levels in 2 weeks prior to sampling (r=0.830) and a low correlation in the 2 weeks following sampling (r=0.0005). Algal cell numbers had a high correlation with bacterial cell numbers (r=0.950). The biomass of algae and bacteria also had a high correlation (r=0.902). The rate of P-uptake from the water by algae and bacteria varied with season and with the species composition of the natural population.     

Respiratory responses of the estuarine mysid Neomysis integer (Peracarida: Mysidacea) in relation to a variable environment

The euryhaline mysid Neomysis integer (Peracarida: Mysidacea) is a common member of the hyperbenthos of the upper reaches of European estuaries. In the East Looe River Estuary (Cornwall, England), this species experiences extensive tidal and seasonal changes in temperature (3 to 15 °C) and salinity (1 to 34‰). In this investigation, the effects of temperature (5, 10 and 15 °C) and salinity (1, 10, 20 and 30‰) on the oxygen consumption of male and female N. integer are reported, and are related to field measurements to identify the adaptive responses of the respiratory physiology to such a variable environment. The general responses were similar for each sex; however, at any given temperature/salinity combination, male N. integer consumed more oxygen than females. The general trends were increased oxygen consumption with increasing temperature (Q₁₀ values ranged from ∼1.7 to 2.5) and decreased oxygen consumption with increasing salinity. Temperature and salinity interacted at high water antagonistically to minimise changes in mysid oxygen-consumption. When related to tidal fluctuations in temperature and salinity experienced by N. integer inhabiting the East Looe River Estuary, the results reveal how the respiratory physiology of this species is adapted to its variable environment. Received: 16 June 1998 / Accepted: 15 December 1998     

Active pharmaceutical ingredient (api) from an estuarine fungus, Microdochium nivale (Fr.)

Various marine habitats sustain variety of bio-sources of ecological and biotech potentials. Pharmaceutical potential compound Cyclosporine A was reported from marine fungus Microdochium nivale associated with Porteresia coarctata, a marine salt marsh grass from mangrove environment distributed along the Central West Coast (CWC) of India. This study involves association of M. nivale with P. coarctata plant, fermentation conditions, purification of Cyclosporine A, chemical characterization etc. Its antifungal inhibition and MIC (Minimum inhibitory concentration) against Aspergillus strains (A. niger, A. japonicus, A. fresenii), yeasts and dermatophytes (Candida sp., Cryptococcus neoformans, Trichophyton mentagrophytes, T. tonsurans, T. violaceum, Microsporium gypsum and Fusarium sp.) were evaluated. However, the MIC against A. japonicus, C. neoformans, Candida sp. and T. tonsurans were confirmed to be as low as 12.5-25 mg disc(-1). The antifungal properties of Cyclosporine A against Aspergillus species, yeast and dermatophytes revealed that CyclosporineAwould be a potential compound for life threatening diseases caused by above fungi in both human and animals. Furthermore, we have reported herewith another source of Cyclosporin Aderived from filamentous fungus, M. nivale. occurring in marine environment.     

13C label identifies eelgrass (Zostera marina) Carbon in an Alaskan estuarine food web

The food web of Izembek Lagoon, Alaska draws most of its carbon from eelgrass (Zostera marina) and phytoplankton. The¹³C:¹²C ratios of these primary producers are sufficiently different to enable their contributions to consumers to be estimated from consumer¹³C:¹²C ratios. Although the technique is conceptually simple, carbon inputs from other sources and isotope fractionations occurring in the food web limit its precision. Isotopic data nevertheless helps to establish the major carbon fluxes through the community and to assess the importance of eelgrass carbon to individual animals. It is particularly useful when dealing with detritus food chains, where direct observations of animal feeding habits are difficult to make. The Izembek community draws much of its carbon from eelgrass. Detritus food chains provide the major pathway for assimilation of eelgrass carbon by the community, but grazers are also important. Eelgrass carbon is more important to benthic animals than to the eelgrass epibiota and the fishes, which depend mainly on phytoplankton carbon.Publication No. 381 of the Institute of Marine Science, University of Alaska.     

Population dynamics and secondary production in an estuarine population of Nephtys hombergii (Polychaeta: Nephtyidae)

From July 1978 to March 1980, a study was made on the distribution, population dynamics and secondary production of Nephtys hombergii Audouin et Edw. occurring in the sublittoral industrialised region of Southampton Water in south England. The distribution of the worm was related to the silt content and copper level of the sediment, the greatest densities of N. hombergii being found in sediment containing 60 to 100% silt. Breeding occurred at a low level throughout the year, with a maximum in July to September and November to January in the second year of growth. Spawning occurred when the oocytes measured 200m in diameter, and unshed gametes were resorbed. Annual production varied between 0.092 and 4.32 g C m^-2 yr^-1 (ash-free dry weight) and amounted to 1.9–39.4% of the total macrofaunal production at the sampling stations. The production:biomass (P:B) ratio of the species varied between 1.6 and 2.9.     

Population dynamics and secondary production in an estuarine population of Caulleriella caputesocis (Polychaeta: Cirratulidae)

Between July 1978 and March 1980, the distribution, population dynamics and secondary production of Caulleriella caputesocis St. Joseph, 1864, in Southampton Water, South England, were investigated. The distribution of the polychaete was related to amount of silt and copper-content of the sediment, the highest densities occurring in sediment containing 60 to 100% silt and less than 50 ppm copper. Breeding occurred at a low level throughout the year, usually when the worms were over one year old, with peak breeding between May and September. C. caputesocis in Southampton Water is monotelic, and oocytes measured 120 to 160 m in diameter at spawning. Unshed oocytes were resorbed. Annual secondary production varied between 0.01 and 5.90 g C m^-2 yr^-1 and P:B ratio of the species ranged between 0.84 and 7.09.     

Diet quality affects an attractive white plumage pattern in dark-eyed juncos (Junco hyemalis)

Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.     

High levels of genetic subdivision of marine and estuarine populations of the estuarine catfishCnidoglanis macrocephalus (Plotosidae) in southwestern Australia

The cobblerCnidoglanis macrocephalus (Valenciennes) is an endemic marine and estuarine catfish from southern Australia. Conflicting views on the degree of isolation of the estuarine populations underscore general questions about genetic divergence in coastal species. Although estuaries are widely recognized as ecologically important, little work has been done on their role in favouring genetic divergence. In order to estimate the extent of genetic subdivision among nearshore marine and estuarine populations, electrophoretic variation of enzymes was examined in seven marine and six estuarine populations of cobbler from sites spanning 1500 km along the southwest Australian coastline. Among all populations, the mean standardized variance in allelic frequencies (F _ST) for six polymorphic loci was 0.277, a high value comparable to those of other shallow-water teleosts whose life-history characteristics and habitat preferences restrict their dispersal capability. The pattern of genetic identities between populations showed divergence between west and south coast sites. Within these regional groups, however, there was substantial heterogeneity, much of which was associated with estuaries. Among all six estuarine sites, the averageF _ST was 0.333, 40% higher than the value of 0.237 for the marine sites. Low estimates of the genetically effective number of migrants suggest population subdivision between marine and estuarine environments and between similar habitat types. This study indicates the importance of habitat in affecting the connectedness of populations, even in apparently open marine systems.     

Food sources of macrobenthos in an estuarine seagrass habitat (Zostera noltii) as revealed by dual stable isotope signatures

Stable carbon and nitrogen isotope analysis was used to examine the resources and position of macrobenthos in an estuarine seagrass food web in two sampling moments, during summer and winter. The contribution of each food source to the carbon requirements of consumers was estimated by a mixing model. The used carbon sources were largely seagrass associated, although seagrass tissues were utilized by only few species, and equally contributed to microphytobenthos and suspended particulate organic matter. Based on isotopic data, Lucinidae bivalves have an alternative trophic pathway via symbiosis with chemoautotrophic bacteria. Resource utilization inside and adjacent to seagrass beds did not differ significantly, implying that seagrass-associated inputs extend well beyond the borders of the vegetation patches.     

Population dynamics of three estuarine meiobenthic harpacticoids (Copepoda) in South Carolina

To elucidate the population dynamics of abundant meiofauna, a 15-month field study of 3 species of harpacticoid copepods was conducted in a South Carolina (USA) estuary. Per capita birth and death rates and average brood size (number of eggs per adult female) were lowest for Enhydrosoma propinguum (Brady), Microarthridion littorale (Poppe), and Stenhelia (Delavalia) bifidia (Coull) from November–February, indicating that food or density-independent factors such as temperature regulated winter densities. Reproduction for all species began in February, with the first appearance of copepodites approximately 1 month later. From March–October, M. littorale displayed high per capita birth and death rates (>0.6 individual^-1 day^-1), and high average brood size (8 to 9 eggs per adult female). As this species is epibenthic, and thus susceptible to grazing by detritivores, these data suggest that M. littorale was limited by predation. S. (Delavalia) bifidia displayed a sharp increase in density, birth rate and average brood size in July, but birth and death rates (0.3 individual^-1 day^-1) were always lower than those of M. littorale and average brood size gradually decreased from July–December. As this species burrows and is less susceptible to grazing predation, these data are consistent with the hypothesis that S. (Delavalia) bifidia became food-limited as population growth approached its carrying capacity. Although E. propinguum was the most abundant species, quantification of birth potential was not accomplished due to an underestimate of the number of ovigerous females. Therefore, little can be concluded about the mechanism of the summer density regulation of E. propinguum.Contribution No. 274 from the Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina.     

Evaluation of changes in the adaptive physiology of shore crabs (Carcinus maenas) as an indicator of pollution in estuarine environments

The major objective of this study was to determine whether there were significant differences in the physiological responses of shore crabs (Carcinus maenas L.) sampled from environments with varying degrees of contamination. Crabs collected from a range of sites were subjected to a standardised, environmentally realistic sequence of physiological challenges in the laboratory to determine if such measures would prove sensitive enough to differentiate among the sites. Heart-rate changes and osmoregulatory ability were measured. The results indicated that changes in osmoregulatory ability were sufficiently sensitive to detect differences in environmental contamination. The utility of physiological measurements in environmental monitoring is discussed. Received: 2 July 1997 / Accepted: 10 July 1997     

Monitoring of linear alkyl benzenes (LABs) in riverine and estuarine sediments in Malaysia

Environmental Geochemistry and Health - The aim of this a pioneering research is to investigate linear alkylbenzenes (LABs) as biomarkers of sewage pollution in sediments collected from four rivers...     

Temperature tolerance of the estuarine prawn Upogebia africana (Anomura,Crustacea)

Continuous temperature measurements were made in a typical South East African estuary. Mean summer (November to March) temperatures were in the range 19° to 24°C, and in winter (June to August) from 13° to 16°C. Large daily temperature fluctuations of 6° to 10°C occurred in summer; these appear to result from tidal movement of cool sea water into the estuary. In winter, temperature fluctuations were much smaller (3° to 5°C). The burrowing prawn Upogebia africana (Obtmann) was found to have an upper lethal temperature of 29°C in both winter and summer. The resistance time of prawns to temperatures above 30°C was much greater in summer than in winter. It was possible to acclimate winter prawns and increase their resistance time to a level comparable to that of summer individuals. A latent period of 40 h occurred before acclimation effects were detectable. Long-term exposure of prawns to high temperatures did not increase their resistance above that of summer prawns. Water at a temperature above this upper lethal temperature is not pumped through the burrows. This avoidance behaviour considerably increases the ability of U. africana to withstand short-lived temperature extremes.     

Frequency-domain sensitivity analyses of an estuarine ecosystem simulation model

A mathematical simulation model of the Narragansett Bay (RI) ecosystem which simulates realistic daily values of phytoplankton, several life stages of zooplankton, and three inorganic nutrients, was modified by removing all seasonally-changing environmental forcing functions. This unforced version of the model generated time-series values for the state variables which resulted only from internal mechanistic formulations, not from environmental inputs. Steady state time-series data for biotic responses were analyzed using variance spectral analysis, which partitions the variance of data among frequencies of oscillation. Periodicities at 0.035 and 0.068 cycles d^?1 dominated the response spectra for phytoplankton, and juvenile and adult zooplankton. The dominance of these oscillations generally prevailed in experimental runs using constant 1 January and 30 June environmental conditions, and in runs which perturbed the ecosystem with a random temperature component (±1.5 or ±3.0°C) about 1 January (3°C) or 30 June (18°C) temperatures. Biomass decayed to near-zero levels in a temperature perturbation of a version of the model from which nutrient regeneration by the benthos had been eliminated. This result was compared with the responses of microcosms from which a benthic component had been omitted. The dominance of periodicities at 0.035 and 0.068 cycles d^?1 cannot be attributed to any single mechanism within the phytoplankton or zooplankton formulations of the model. The lack of sensitivity of model components to temperature perturbations over a wide band of frequencies, and their insensitivity to gross changes in steady-state temperature values, suggest that further analyses should displace rate coefficients of internal mechanisms in order to identify the stability properties of major material cycles of the system.     

Allocation of nitrogen and carbon in an estuarine salt marsh in Portugal

Above and below-ground biomass and nitrogen and carbon composition ofSpartina maritima, Halimione portulacoides andArthrocnemum perenne, dominating species in plant communities of the lower, middle and higher salt marsh, respectively, were compared in an estuarine salt marsh in Portugal. Plant and soil nitrogen and carbon pools were estimated. For all three species root biomass was significantly higher (70–92% of total biomass) than above-ground biomass. The percentage of root biomass was related to the location of the plants in the marsh: higher values were found in plants growing in the lower salt marsh where the sediment was more unstable and subject to tidal action, which stresses the role of the roots as an anchor. For all three species nitrogen concentrations were highest in leaves, reflecting the photosynthetic role of the tissue. For carbon higher concentrations were found in the stems, with the exception ofS. maritima. In general, lower nitrogen concentrations were found in summer, which can be explained by dilution processes due to plant growth. For both nitrogen and carbon, higher concentrations were found in the soil surface layers. Higher soil nitrogen and carbon levels were associated with higher organic matter contents. Most of the nitrogen in the salt marsh occurred in the sediments (0–40 cm) and only ca. 5.7–13.3% of the total was found in the plants. The greater portion (76.5%–86%) of carbon was found in the sediment.     

Abundance biomass comparison (ABC method): effects of an estuarine gradient,anoxic/hypoxic events and contaminated sediments

The ABC method for evaluating pollution-induced stress was tested using data from the Chesapeake Bay, Virginia, collected between 1985 and 1989. Three predictions were tested: (1) benthic communities from estuarine transitional regions with salinities near the range of 5 to 8 parts per thousand (horohalinicium) should be classified highly stressed due to major shifts in ionic composition producing physiological stress; (2) benthic communities from regions subjected to summer low dissolved oxygen conditions (anoxia or hypoxia) should be classified as highly stressed after such events; and (3) benthic communities from sediments contaminated with heavy metals and polynuclear aromatic hydrocarbons should be classified as highly stressed. Only partial support for each of these predictions was found and several problems with the ABC method were obvious. A small number of large-sized species, particularly in mesohaline and polyhaline regions of the estuary, greatly affected the analysis. Similar designations of stress could be produced by simply sampling only for these rare, large species. Regions of the estuary considered a priori as highly stressed were sometimes designated as unstressed due to (1) minor shifts in dominance patterns in benthic communities with low absolute numbers of individuals and biomass, e.g. in regions affected by anoxia/hypoxia, and (2) collection of rare, but large species, such as the tubiculous polychaete, Diopatra cuprea, in contaminated sediments. Regions of the estuary considered a priori as unstressed were sometimes designated as highly stressed due to dense recruitment events. Contrary to assumptions of the ABC method, increased sample size (replication) may result in the collection of rare, large-sized individuals in highly stressed communities. Partial dominance curves were applied to the data and (1) removed the effect of biomass dominants in contaminated sediments changing the classification of communities from unstressed to stressed, (2) did not change the stressed classification due to dense recruitment events, and (3) changed the classification of mesohaline and polyhaline communities from unstressed to stressed, even in the absence of low dissolved oxygen events or contaminated sediments. No single method or analysis is likely to produce stress classifications without unacceptable misclassifications. We propose that ecological stress, from any source, is best measured using multiple methods or analyses with different assumptions. The consistency of classification between different approaches would provide the robustness necessary to judge the reliability of a stress classification.     

Diet of some Antarctic nudibranchs (Gastropoda,Opisthobranchia, Nudibranchia)

Austrodoris kerguelenensis feeds on sponges of the genera Rosella and Scolymastra; Aegires albus, on Hexactinellida (Porifera); and Tritoniella belli, probably on non-determined synascidians. Bathydoris clavigera and B. hodgsoni are omnivorous.