Submersion Period Research Articles

Arterial blood gas levels and cardiovascular function during varying environmental conditions in a mudskipper, periophthalmodon schlosseri

Changes in blood gas levels, blood pressure and heart rate were studied in chronically cannulated mudskippers, Periophthalmodon schlosseri, subjected to air exposure (6 h), aquatic hypoxia with access to air (water PO2 <0.9 kPa, 6 h) and forced submersion in normoxic water (12 h) at 30 degrees C. Air exposure did not affect either blood O2 and had little effect on blood CO2 levels, but blood pH increased slightly, but significantly. Blood ammonia concentration was elevated sixfold during air exposure. Aquatic hypoxia caused no significant changes in blood gas levels. When the fish was forcibly submerged, blood O2 saturation decreased rapidly to approximately 30 %. Blood PCO2 and total CO2 also decreased, but blood pH was unaffected by forcible submersion. Air exposure did not affect blood pressure or heart rate. Aquatic hypoxia did not affect blood pressure but transiently increased heart rate. In contrast, forced submersion significantly depressed heart rate throughout the period of submersion, while blood pressure decreased only transiently. Upon emersion, the heart rate immediately increased to above the control level when the fish took its first air breath.

Species diversity of freshwater hyphomycetes in some streams of Pakistan. III. Autumnal colonization of freshwater hyphomycetes on bait leaves

Significantly more species of freshwater hyphomycetes colonized bait leaves of alder (16 species) and willow (14 species) during early submersion period (1 wk) than those of oak (8 species). Production of conidia was also higher on alder and willow leaves than on oak leaves. Higher amounts of dry mass were lost from the alder (28.6%) and willow leaves (29.4%) than from the oak leaves (18.7%). Rapid loss of dry mass was accompanied by rapid development of a fungal community. Fungal species took a longer time (6 wk) to reach their peak of occurrence on oak than on willow and alder leaves (3–4 wk).Flagellospora curvula dominated the assemblages of freshwater hyphomycetes on alder and willow leaves, andLunulospora curvula dominated the assemblage on oak leaves. The freshwater hyphomycete community showed higher values of species diversity (H value) on oak leaves than on alder and willow leaves.

Effects of substratum on the recruitment and development of an intertidal estuarine fouling assemblage

The effect of four substrata (concrete, plywood, fibreglass and aluminium) on the recruitment of species and development of an intertidal estuarine fouling assemblage was examined in Quibray Bay of Botany Bay, New South Wales, Australia. Many species, including the oyster Saccostrea commercialis (Iredale & Roughley) and the barnacles Hexaminius sp., Balanus amphitrite Darwin and Balanus variegatus Darwin, recruited in greater numbers on concrete or plywood surfaces than on fibreglass or aluminium. As a result, patterns of change in the number of species through time were dependent on the substratum. Multivariate analyses indicated that assemblages on different substrata were significantly different after 1 or 2 months of submersion, but became more similar after longer periods (up to 4–5 months). The reasons for this gradual conformity varied depending on the season of submersion and the composition of the species settling in a particular season. The results of this study indicated that the nature of the substratum can affect both initial colonisation of particular species and the development of the assemblage over time. Because the effect of substratum varies with the period of submersion, comparisons of various studies on fouling assemblages using different natural and artificial substrata and for varying lengths of time are likely to be very difficult.

Black America: from community health care to crisis medicine.

This study traces the major policy shifts in medical care that have affected disadvantaged African-Americans and the response of this community's medical leadership to these changes. Since World War II policy has passed through three major phases. The first--engagement--ran from the mid-1960s through the mid-1970s. During this phase a community health policy orientation prevailed as national government targeted resources to health care programs for needy blacks and other poor Americans. From the late 1970s to the mid-1980s the period of submersion occurred: black community health professionals and political leaders experienced a new-found inclusion in health policy debate, but, at the same time, broader policy-making circles in government and health care reduced medical resources for the inner-city poor. Finally, in the third phase--crisis recognition--a network developed of community health advocates who seek to reorient the health system so that it addresses needs within urban American's "New Ghettos."

Changes in cardiac rhythm in man during underwater submersion and swimming studied by ECG telemetry.

A previously reported method for electrocardiographic (ECG) telemetry in water using frequency-modulated current was improved to obtain more stable ECGs. The ECGs of seven healthy men were monitored using the improved method during and after whole-body submersion or underwater swimming. Bradycardia and arrhythmias were observed during the submersion, and transient tachycardia was detected after the start of underwater swimming, followed by bradycardia with arrhythmias. Three different types of arrhythmias were observed: sinus arrhythmia (SA), supraventricular extrasystole (SE) and ventricular extrasystole (VE). SA and SE tended to develop during the latter half of the period of submersion or underwater swimming, and especially after the restart of breathing. VEs were detected in only one subject during submersion, whereas they occurred in most subjects during and after underwater swimming. Individual variations were found in development of arrhythmias, one subject showing no arrhythmia. Bradycardia, SA and SE could depend on vagal suppression in underwater conditions, and VE may be related to the effect of muscular movement on cardiac function in addition to vagal inhibition.

The Bare Zone of Swedish Rocky Shores: Why Is It There?

Rocky shores world-wide are characterized by two factors; low species richness and zonation of dominant species, both related to changing water levels. In Swedish waters, sea level fluctuates by up to 2 m due to changes in atmospheric pressure, onand off-shore winds, and to a lesser extent, due to small tides. As pressure varies irregularly over time, sea level fluctuations are unpredictable. Yet, Swedish rocky shores have a zonation pattern which largely corresponds to that of tidal shores. However, two differences appear: firstly, littoral organisms of Swedish shores require more submersion time over the year than species of tidal shores, and secondly, a bare azoic zone separates the marine and terrestrial species. Non-tidally induced fluctuations of sea level increase the variance of submersion period length by several orders of magnitude, and the prolonged periods of either submersion or emersion act as disturbances in an already stressed environment. Grime's plant strategy hypothesis predicts that no plants withstand a habitat both under stress and disturbances. The bare zone of atidal shores seems to support this.

Modes of colonization of an heterogenous alluvial area on the edge of the garonne river by Phalaris arundinacea L

AbstractThe modes of colonization of a heterogenous alluvial area by Phalaris arundinacea L., a pioneer species, were studied on the edge of the Garonne river downstream of Toulouse (S.W. France). The heterogeneity of the location is essentially represented (1) by the type of soil: sands and gravels on the banks of the Garonne and silts in the hollows at a certain distance from the river; (2) by the period of submersion: zones flooded only during short periods and zones submerged during six months of the year; and (3) by the fertility of the substratum.The response of the Phalaris arundinacea population were measured using vegetation structure parameters and descriptions of the development cycle. Water plays the most important part in the identification of space colonization modes. Two types of individual plants appear. Those living in submerged environments for a very short time are characterized by both a high biomass and sexual reproduction energy allowance, and by unimodal growth. Those living in environments flooded over long periods are characterized by both a low biomass and sexual reproduction energy allowance, and by a bimodal growth in two successive generations: a submersion generation and a low‐water generation. Specific competition reduces the differences between the two types of individual plants from the point of view of population cover and of the structure and density of the individual plants. Phalaris arundinacea L. is shown to have a remarkable capacity for colonizing sites with distinctive ecological characteristics.

A preliminary study of buoyancy behaviour in Avicennia marina propagules

Propagules of A. marina (Forssk.) Vierh. were shown to be either ‘sinkers’, i.e. sink on shedding their pericarp, or ‘floaters’ i.e. remain buoyant after shedding their pericarp. While propagules from different estuaries showed big variations in buoyancy, generally mangroves in the north produced a high proportion of ‘floaters’ while those in the south produced mainly ‘sinkers’. The buoyancy of propagules appeared to be determined by the relative densities of the different parts of the cotyledons. Anatomical sections revealed that there was little difference between the different parts of ‘sinkers’, whereas in ‘floaters’ parts which were buoyant had a high proportion of intercellular air spaces and those which sank had closely- packed cells high in reserves. Some of the ‘sinkers’ were found to become buoyant after a period of submersion, although propagules from all estuaries did not behave in this way. Apparently those propagules which had a density close to that of sea water tended to become buoyant later and it was suggested that utilization of reserves reduced the original density to a level which enabled these propagules to float. The implications of variations in buoyancy of A. marina propagules for the further distribution of this mangrove along the southeast Cape coast are discussed.

Food intake of Macoma balthica (mollusca) in relation to seasonal changes in its potential food on a tidal flat in the Dutch Wadden Sea

Food intake, absorption and presumed origin of the food were studied simultaneously throughout the year for a tidal flat population of Macoma balthica in the westernmost part of the Dutch Wadden Sea. The rate of food intake was calculated from the amount of chlorophyll a in the stomach and the rate of stomach evacuation. Highest rates of intake by Macoma were found during the first 4 hours of submersion and during the months April, May and June. During the emersion period and in winter the feeding activity was low. The total intake per submersion period was positively correlated with the concentration of chlorophyll a in the water, but not with that in the top layer of the sediment. Moreover, the season with high rates of intake coincided with the short maxima in spring for the concentrations of organic carbon and chlorophyll a in the water, but not with the longer seasonal maxima (from April to October) for these concentrations in the sediment. In the sediment mainly pennate diatoms were found, in the water centric diatoms. The algal species composition of the stomach content showed a strong resemblance to the composition of the water samples. Observations on siphon movements in the laboratory showed that Macoma spent more time with the siphon near the bottom than with the siphon extended into the water column. It is concluded that Macoma, although it behaves most of the time as a deposit feeder, depends for its food intake for the greater part on food present in the water column.

Osservazioni fitosociologiche sul «Lago Gurrida» (Sicilia Nord-Orientale)

Abstract Phytosociological observations on «Lago Gurrida» (N-E Sicily). The results of a phytosociological research on the vegetation of «Lago Gurrida» are given. It is a little marshy area at present partially bonified, which is localized at the base of the N-W slope of Etna and is fed mainly by the water of Flascio river. The natural vegetation is represented by very peculiar plant-communities which are linked to the lenght of the submersion period. The surveyed associations are the followings: Myriophylletum spicati Soo 1927, submerged monophytic vegetation belonging to Potametea; Eleocharido-Alismetum lanceolati ass. nov., hygrophilous association referred to Phragmition which is represented by a more hygrophilous subassociation (bolboschoenetosum) and by a less hygrophilous subassociation (alismetosum); Phragmitetum communis (W. Koch 1925) Schmale 1939 forming a dense monophytic vegetation; Carici otrtibae-Juncetum inflexi ass. nov. of Agropyro-Rumicion crispi, physionomically characterized by the do...

Microalgal food and the growth of the intertidal gastropods Nerita atramentosa Reeve and Bembicium nanum (Lamarck) at four heights on a shore

The rates of growth of two common intertidal gastropods, Nerita atramentosa Reeve and Bembicium nanum (Lamarck), were measured during ≈ 3 months in cages at four heights on a shore at Cape Banks, New South Wales. Replicate cages at each level were used to keep snails at constant densities throughout the experiments. Amounts of food on the substratum in each cage were measured as the concentration of chlorophyll in samples of the rock, which is known to be a reliable estimator of number of algal cells present. Rates of feeding were measured as the number of radular scrapes per min in snails removed to the laboratory, and the sizes of radulae were measured at the end of the experiments. Nerita did not increase in shell-length at the two higher levels on the shore, but grew at the two lower levels. Rate of growth was positively correlated with the amount of chlorophyll in the substratum, and was not apparently affected by the greater period of submersion (and concomitant time available for feeding) towards the lower levels on the shore. There was no difference in rates of feeding at the four heights. Radulae of snails from the lower levels were longer than those from higher on the shore, but this was attributable to the greater overall size of snails from lower levels (i.e. there was no significant difference in relative size of radula from one height on the shore to another). Bembicium increased in width of shell at all levels on the shore, but grew more quickly at all three lower levels than at the top of the shore. There was no difference in rate of feeding, nor in relative size of the radula from one level to another on the shore. Rate of growth was not significantly correlated with the amount of food available, nor with the period of submersion, nor the product of these two variables. The simplest explanation for these results was that sufficient food was available for maximal growth of Bembicium at the three lower levels, but not at the highest level. Thus, only where the amount of food was inadequate, at the highest level, was rate of growth reduced. These results are discussed with reference to the difficulties of determining the relative importance of influences on the growth of intertidal snails, because of inherent confounding of the period of submersion with different amounts of food at different heights on the shore.

A revision of the North-east Atlantic species of Ericthonius (Crustacea: Amphipoda)

Seven species of the amphipod genus Ericthonius are described and figured from the North-east Atlantic and associated seas and a key to their identification is provided. West Atlantic material is also considered where relevant to the taxonomy of East Atlantic species. Two species are re-established after a long period of submersion in synonymy, and one species new to science is described. The previous confusion in the literature of some of the species is discussed, and a synonymy of species described in key works is provided.

Patterns of Occurrence of Ascomycetes Associated with Decomposing Twigs in a Midwestern Stream

Packs of twigs from cherry, oak, silver maple, and sycamore trees were placed in an Illinois stream and samples were recovered periodically over 30 months. Ash-free dry weights remaining over time were determined and twigs were examined for Ascomycetes directly and after incubation. Twigs disappeared at rates much lower than those reported for leaves and provided an enduring substrata for fungi. Thirty-three Ascomycetes were collected: Pseudohalonectria lignicola and Savoryella lignicola are reported from the United States for the first time. Nectria lucidum, Pseudohalonectria lignicola, Leptosphaeria sp. 1, and Aniptodera sp. 1 occurred most frequently. With the exception of the decline of blastocladiaceous and saprolegniaceous species after one week, and the disappearance of N. lucidum after the first year, distinct changes in community structure did not occur during the submersion period. Generally, the numbers of species and the frequencies of occurrence of predominant species increased with increased time of submergence. Long-term incubation of substrata yielded the greatest number of Ascomycetes; incubation in light/dark conditions increased the number of species and the frequencies of occurrence of individual species over dark incubation.

'Stability' of the fouling communities on the pilings of two piers in South Australia.

The subtidal communities of sessile organisms on the pilings of two piers were observed by photography of fixed quadrats over a period of two years. Data are presented on species-composition, relative abundance of species, and maximum longevities of individuals and colonies. The fluctuations in various properties of the communities (e.g. measures of species diversity, and percentage vovers of species and phyletic groups) are tested by a priori defined criteria for "narrow stochastic boundedness" and most are found to be narrowly bounded, despite considerable turnover of space. We conclude that most properties of the community vary less through time-that is, the community is in a sense more "stable"-than fouling communities previously studied using small plates immersed for relatively short periods. Long-lived species are relatively more abundant on the pilings than in plate-studies. These differences are attributed to the large size and long period of submersion of the pilings. Our results appear similar to those of other studies on large, old substrata.

On the problem of the preservation of human bone in sea-water

Lack of suitable information about the fate of archaeological human bones in sea suggested that we should carry out a multidisciplinary investigation on the state of preservation of the skeletal remains of three individuals who were apparently drowned while sailing in Arabian ships wrecked during the 10th century A.D. off the Mediterranean coast of France. The bones and the slime which had penetrated into their cavities during their long period of submersion were investigated by the following methods. Bones: specific weight, histology, microradiography, electron microscopy, microscopy, microhardness, x-ray diffraction, calcium and phosphorus analysis, and 14C-dating. Slime: grain distribution, mineralogical analysis, and identification of microfauna and microflora. In spite of their long immersion in sea-water, the bones were, in general, well preserved. This is especially true of the organic bone matrix, whose histological and histochemical properties were like those of fresh bone. On the other hand, the inorganic fraction had increased, though its patterns corresponded to those of hydroxyapatite. Besides, some deterioration in the bones had been induced by unidentified microorganisms. All these findings and their genesis are discussed in detail.

Preliminary observations using an attached microphonic sensor to study feeding behaviour of an intertidal limpet

A simple field system to monitor feeding activity of grazing intertidal molluscs is described. Feeding behaviour of the patellid limpet Cellana ornata (Dillwyn) inhabiting high levels on a sheltered rocky shore was studied. Feeding in this species was found to be mainly restricted to diurnal submersion periods, during which it was continuous with radula rasping rate remaining more or less constant over the entire submersion period. This general pattern, however, varied between individuals and was influenced by waves; wave action in particular appears to be important in stimulating foraging. In an individual, studied regularly over an entire year, radula rasping rate was observed to be directly related to environmental water temperature.

On the problem of the preservation of human bone in sea-water

Lack of suitable information about the fate of archaeological human bones in sea suggested that we should carry out a multidisciplinary investigation on the state of preservation of the skeletal remains of three individuals who were apparently drowned while sailing in Arabian ships wrecked during the 10th century A.D. off the Mediterranean coast of France. The bones and the slime which had penetrated into their cavities during their long period of submersion were investigated by the following methods. Bones: specific weight, histology, microradiography, electron microscopy, microscopy, microhardness, x-ray diffraction, calcium and phosphorus analysis, and 14C-dating. Slime: grain distribution, mineralogical analysis, and identification of microfauna and microflora. In spite of their long immersion in sea-water, the bones were, in general, well preserved. This is especially true of the organic bone matrix, whose histological and histochemical properties were like those of fresh bone. On the other hand, the inorganic fraction had increased, though its patterns corresponded to those of hydroxyapatite. Besides, some deterioration in the bones had been induced by unidentified microorganisms. All these findings and their genesis are discussed in detail.

Morbidity in childhood near-drowning

An assessment of morbidity in near-drowning was made from a review of emergency room and hospital records of 72 patients, ages 9 months to 20 years, who suffered near-drowning during the period January 1972 through June 1974. Fifteen patients (21% evidenced severe anoxic encephalopathy; the remainder had no detectable neurologic deficits. Hypoxemia was demonstrated in 56 patients. Severe acidosis was not present unless respiratory failure occurred. Neither electrolytes, red blood cell hemolysis, nor cardiac arrhythmias presented a problem. Respiratory complications included pulmonary edema, aspiration pneumonia, atelectasis, shock lung, pneumothorax, and pneumomediastinum. All children requiring cardiopulmonary resuscitation in the emergency room suffered anoxic encephalopathy. The occurrence of seizures, fixed and dilated pupils, flaccid extremities, and lack of response to deep pain in the emergency room had almost universal correlation with resultant severe anoxic encephalopathy, as did a submersion period of six or more minutes. The morbidity of near-drowning is significant with regard to the number of children affected and the severity of the central nervous system insult received. The statement by the American Heart Association that resuscitative efforts in children should be continued for periods longer than ten minutes needs reevaluation, since neurologic recovery did not occur in any child requiring cardiopulmonary resuscitation (CPR) in the emergency room. More importantly, new methods of cerebral resuscitation need to be developed and established. In short, medical personnel need to think in terms of cardiopulmonary cerebral resuscitation (CPCR) rather than in terms of CPR.

Morbidity of Childhood Near-Drowning

An assessment of morbidity in near-drowning was made from a review of emergency room and hospital records of 72 patients, ages 9 months to 20 years, who suffered near-drowning during the period January 1972 through June 1974. Fifteen patients (21% evidenced severe anoxic encephalopathy; the remainder had no detectable neurologic deficits. Hypoxemia was demonstrated in 56 patients. Severe acidosis was not present unless respiratory failure occurred. Neither electrolytes, red blood cell hemolysis, nor cardiac arrhythmias presented a problem. Respiratory complications included pulmonary edema, aspiration pneumonia, atelectasis, shock lung, pneumothorax, and pneumomediastinum. All children requiring cardiopulmonary resuscitation in the emergency room suffered anoxic encephalopathy. The occurrence of seizures, fixed and dilated pupils, flaccid extremities, and lack of response to deep pain in the emergency room had almost universal correlation with resultant severe anoxic encephalopathy, as did a submersion period of six or more minutes. The morbidity of near-drowning is significant with regard to the number of children affected and the severity of the central nervous system insult received. The statement by the American Heart Association that resuscitative efforts in children should be continued for periods longer than ten minutes needs reevaluation, since neurologic recovery did not occur in any child requiring cardiopulmonary resuscitation (CPR) in the emergency room. More importantly, new methods of cerebral resuscitation need to be developed and established. In short, medical personnel need to think in terms of cardiopulmonary cerebral resuscitation (CPCR) rather than in terms of CPR.

Pulmonary gas exchange in freely diving weddell seals Leptonychotes weddelli

Composition of end-tidal samples collected from the first expiration after resting apneusis and after deep or prolonged dives was determined in voluntarily diving adult Weddell seals whose average weight was 425 kg. Also determined was respiratory exchange ratio (R) and oxygen consumption ( o 2 ). After an average resting apneusis of 4.5 min the end-tidal 0, tension (p a O 2 ) averaged 59 mm Hg and CO 2 tension (P a CO 2 ) averaged 50 mm Hg. After deep dives of an average submersion of 11.5 min the P A O 2 = 70mmHg and P a CO 2 =27 mm Hg. The exploratory dives, which ranged from 25–47 min, averaged P a O 2 =40 mm Hg and P a CO 2 = 36 mm Hg. It is concluded that the marked difference in the end-tidal composition of the deep dives is a result of hyperventilation preparatory for the dive and subsequent lung collapse and little gas exchange during the dive. Resting R was 0.69, but after dives R was highly variable. It began low and usually rose above 1.0 and subsequently fell to near 0.70. Mean resting O 2 was 309 ml × kg −1× hr −1 whereas O 2 after dives was initially as high as 2.4 L × kg −1× hr −1 but fell precipitously during the ventilation period. Mean overall o 2 which included both the ventilation and the submersion period was 254 ml × kg −1× hr −1. The reasons for diving o 2 being lower than resting O 2 are discussed and it is concluded that the cost of diving is not great.