Showing papers by "University of Maine published in 1988"

Paleoecology and the Coarse-Filter Approach to Maintaining Biological Diversity

Abstract: The difficulties of saving millions of species from extinction often cause conservationists to focus on a higher level of biological organization, the community. They do so for two reasons: (1) communities are considered important biological entities in their own right; and (2) conserving representative samples of communities is seen as an efficient way to maintain high levels of species diversity. This approach will work if the chosen communities contain almost all species. Because it potentially saves most but not all species, community conservation is a “coarse-filter” approach to the maintenance of biological diversity, and contrasts with the “fine-filter” approach of saving individual species. Paleoecological information on the distribution of plant taxa in North America, however, indicates that most modern plant communities are less than 8,000 years old and therefore are not highly organized units reflecting long-term co-evolution among species. Rather, they are only transitory assemblages or co-occurrences among plant taxa that have changed in abundance, distribution, and association in response to the large climate changes of the past 20,000 years. During periods when climate changes are large, communities are too ephemeral to be considered important biological entities in their own right. Large climatic changes are also likely to occur during the next century because of increased concentrations of CO2, and we therefore propose that the coarse-filter approach to selecting nature reserves should be more strongly influenced by the distribution of physical environments than by the distribution of modern communities. Ideally, nature reserves should also encompass a broad enough range of environments to allow organisms to adjust their local distribution in response to long-term environmental change and should be connected by regional corridors that would allow species to change their geographic distributions. Resumen: Las dificultades en salvar millones de especies de extincion muchas veces lleva a los conservacionistas a enfocarse a un nivel mas alto de organizacion biologica: la comunidad. Ellos lo hacen por dos razones: 1. las communidades son consideradas entidades biologicas importantes en su derecho, y 2. conservando ejemplos representativos de las communidades se considera manera eficiente de mantener niveles altos de diversidad de especies. Esta aproximacion aproche trabaja si las comunidades escogidas contienen casi todas las especies. Al salvar potencialmente la mayoria, pero no todas las especies, la conservacion de comunidades es solo una aproximacion gruesa para el mantenimiento de la diversidad biologica, y contrasta con la mayor resolucion que representa el de salvar especies individuales. Sin embargo, informacion paleoecologico sobre la distribucion de la taxonomia de plantas en Norte America indica que las comunidades mas modernas de plantas tienen menos de 8,000 anos y por eso no son unidades bien organizadas reflejando coevolucion de largo plazo entre las especies. Mas bien, son ensamblajes transitorios o concurrentes entre la taxonomia de plantas que ban cambiado su abundancia, distribucion y asociacion en respuesta a cambios grandes climaticos de los ultimos 20,000 anos. Durante periodos cuando los cambios de clima son grandes, comunidades son muy efimeras para considerarse entidades biologicos importantes Cambios grandes climaticos tambienson probables durante el proximo siglo por las concentraciones crecientes de CO2, y nosotros, por esta razon proponemos que la aproximucion gruesa de seleccionar reservas de la naturaleza debe ser mas influenciada por la distribucion de ambientes fisicos que por la distribucion de comunidades modernas. Idealmente, las reservas de la naturaleza tambien deben considerar un rango suficientemente amplio de ambientes diferentes para permitir a los organismos a ajustar su distribucion local en respuesta a cambios ambientales de largo plazo. Asi mismo las reservas deben, en lo posible, formar corredores regionales que permitan a las especies cambiar su distribucion geograficas.

Forest fragmentation and avian nest predation in forested landscapes.

Abstract: The size of forest fragments, the use of land bordering fragments, and the distance of nests from an edge all affect the frequency of predation upon bird nests in Maine (USA), an area where the forest has been fragmented by roads, but not significantly reduced in area We placed artificial nests containing quail eggs in forests of different sizes and at various distances from the edge to test which of these factors was most important in describing predation Predation was greatest in small tracts surrounded completely by land Large areas and those bordered on at least one side by a large water body had lower predation rates This suggests that influx of predators from nearby habitats may be responsible for much of the nest predation in forest fragments

Welfare Measurements Using Contingent Valuation: A Comparison of Techniques

Abstract: Three commonly used techniques of asking contingent valuation questions are compared: iterative bidding, payment cards, and dichotomous choice. The results reveal that no single contingent valuation technique is neutral in the elicitation of hicksian surplus and each technique has its strengths and weaknesses. The iterative bidding estimates contain a starting point bias, while the payment card and dichotomous choice estimates were influenced by the interviewers soliciting the contingent values. Finally, the analysis of dichotomous choice responses involves unresolved issues that warrant further investigation. On the other hand, dichotomous choice is the easiest technique to administer in a survey setting.

Relationship of Preference Judgments to Typicality, Novelty, and Mere Exposure:

Abstract: Two theories of aesthetic preference are reviewed. According to Berlyne's psychobiological theory, the main determinants of aesthetic preference are collative variables such as complexity and novelty, and preference is generally related to its determinants in an inverted-U manner. Recent findings contrary to these predictions are briefly reviewed. According to Martindale's cognitive theory, the main determinant of aesthetic preference is prototypicality or meaningfulness, and preference is usually related to its determinants in a monotonic or U-shaped fashion. Three experiments concerning preference for semantic category exemplars are reported. Typicality accounted for eight or nine times more of explained variance in preference than did long-term novelty, short-term novelty, or mere exposure. Preference was related to both typicality and collative variables by monotonic or U-shaped functions.

Experimental verification of episodic acidification of freshwaters by sea salts

Abstract: Short-term acidification of streams and lakes can cause fish kills and other adverse biological effects1,2. Such acid episodes may be due to acid deposition or the result of natural processes. The 'seasalt effect' is a natural process in which episodic input of seasalt-rich precipitation to acid soils can cause acidification of runoff3. Several cases of acid episodes observed in coastal regions of Norway4 and eastern United States5 have been ascribed to the seasalt effect. To test experimentally this effect we dosed a small pristine catchment in western Norway with dilute sea water. Runoff chemistry responsed immediately; pH dropped from 6.1 to 5.1, alkalinity from 20 to –2 µequiv. l–1 and labile monomeric aluminium increased from 15 to 95 µg l–1. This experiment verifies that high inputs of sea salts can cause natural acidification episodes due to cation exchange in small catchments with acidic soils.

Determination of atrazine residues in water and soil by enzyme immunoassay.

Abstract: Atrazine, a triazine herbicide, is the second most widely used pesticlde in the United States with approximately 79 million pounds of active ingredient being applled each year (Anonymous 1987) as a preor post-emergent weed-control agent in the U.S. for corn, sorghum, sugarcane and pineapple. Because of its extensive use, possible seasonal stability and inadequate toxicological data (Wilson et al. 1987), there is a need for monitoring atrazine in water and soil. Municipal and private water sources should be monitored periodlcally in areas of frequent atrazine use. In soil, atrazine carry over may be injurious to certain rotational crops and thus the soil should be analyzed before planting (Ferris and Haigh 1987).

Dehalogenation in marine sediments containing natural sources of halophenols.

Abstract: Halophenols such as 2,4-dibromophenol (DBP) occur naturally in some marine sediments, as a consequence of various animal and algal activities. In an earlier study, DBP was observed in the burrow microenvironment of the hemichordate Saccoglossus kowalewskii. At the concentrations found in the burrow lining, aerobic respiration appeared to be inhibited significantly relative to anaerobic catabolism. This effect, as well as factors contributing to the degradation of DBP, has been documented further here. Results from the addition of radiolabeled DBP to oxic and anoxic sediment slurries and growth experiments with aerobic and anaerobic enrichments suggested that aerobes did not significantly metabolize DBP and that concentrations likely to be encountered on the inner surfaces of the burrow wall were inhibitory. In contrast, only minimal inhibition of growth occurred for anaerobes exposed to 1 mM DBP; in addition, DBP was substantially degraded in both enrichments and sediments under anaerobic conditions. Dehalogenation with the consequent production of phenol appeared to initiate anaerobic degradation. Sulfate-reducing bacteria did not dehalogenate DBP but appeared to degrade phenol. Decreased bacterial numbers and marked differences in the concentration and chemical speciation of iron in sediments from S. kowalewskii burrows may be attributed to toxic effects of DBP on aerobic bacteria.

Patterns of sulfate reduction and the sulfur cycle in a South Carolina salt marsh

Abstract: Rates of sulfate reduction and the magnitude of various sediment parameters related to the sulfur cycle were measured at about quarterly intervals for a 3-yr period at sites in a South Carolina salt marsh containing tall- or short-form Spartina alternij70ra. Sulfate reduction rates were greater at all times in the short-form sites and decreased markedly with depth. Seasonal changes were highly correlated with ambient temperature except in May and August when interactions with plants may have affected rates directly. In the short-form site, the annual integrated sulfate reduction rate accounted for about 47. 5–6 7 .OO/o of the estimated belowground plant production. Dissolved sulfides and pH varied seasonally in the short- but not tall-form sites; seasonal minima in the short-form site occurred during May and were probably due to oxidation of the sediment with the onset of plant production. Mechanisms resulting in oxidation were not evident however. Chromium-reducible sulfur, which is primarily pyrite, was substantially greater in the tall- than short-form site but apparently stable temporally at both sites. The differences in pool sizes of pyrite were probably due to differences in iron dynamics and the extent of sulfide oxidation. Microprofiles of dissolved oxygen were consistent with greater oxidation at the short-form site since the penetration of oxygen was deeper. Differences in sediment texture and tidal inundation may have contributed to greater oxygen inputs at the short-form site.

Zonation of deep water benthic algae in the gulf of maine1

Abstract: Algal community structure is described for a deep-water rock pinnacle in the Gulf of Maine. Three depth zones of algal dominance were apparent consisting of 1) leathery macrophytes (to 40 m), 2) foliose red algae (to 50 m) and 3) crustose algae (fleshy crusts to 55 m and coralline crusts to 63 m). Microscopic filamentous and erect calcareous algae were also present but inconspicuous. Upright macroscopic filamentous and thin sheet-like forms were not observed on the pinnacle. Sea anemones (Metridium senile) dominated some vertical faces and abrupt prominences in the shallowest regions of the pinnacle (to 24 m) and locally appeared to set the upper vertical limits of kelp and possibly foliose reds. Laminaria sp. formed an open park-like canopy from 24 to 30 m whereas Agarum cribrosum, the deepest kelp, grew as isolated individuals to 40 m. Peyssonnelia sp. and Leptophytum laeve were the deepest occurring fleshy (to 55 m) and calcareous crusts (to 63 m), respectively. The occurrence of these algae at record depths for the Gulf of Maine and for cold water marine environments may be the result of an absence of large herbivores and the high productivity potential of the benthos in these relatively clear waters. By compiling data on depth distribution patterns world-wide, it is evident that the three zone structure of algal morphologies observed in the Gulf of Maine is a global phenomenon.

Pretreating landfill leachate with peat to remove metals

Abstract: In this investigation, the capacity of peat to treat two different landfill leachates was determined. Freundlich isotherms showed that, for the tested metals (Cd, Cr, Cu, and Pb), an increased time of contact increased the level of adsorption over the entire range of influent values studied. In addition, metal interaction may play an important role in the adsorption of metals from leachate, as the various metal ions compete for the available adsorption sites on the peat. Column studies using two leachates, one from a municipal refuse fill (Al, Ca, Cd, Fe, Mg, Na, and Pb), and one from a fill which receives mainly oil and fly ash (Al, Ca, Cr, Fe, Mg, Mn, Na, Pb, and V), were conducted to establish design parameters for full-scale design. The efficiency of treatment was evaluated as a function of factors important for developing filter design criteria. Further considerations were given to filter longevity and ease of replacement, as well as for the ultimate disposal of the peat from the filters. For the municipal leachate a compaction density of 0.12 g mL−1 gave the best results as clogging occurred at higher densities, whereas 0.18 g mL−1 provided the best removal for the industrial leachate. While peat is incapable of adequately removing metals to acceptable levels for direct discharge, peat can provide substantial removal as a pretreatment process at low hydraulic loadings. Desorption of up to 50% was found when deionized water was applied to spent columns so ultimate disposal of the peat would require a dry environment.

Closure and Monotonicity Properties of Nonhomogeneous Poisson Processes and Record Values

Abstract: Interconnections between occurrence times of nonhomogeneous Poisson processes, record values, minimal repair times, and the relevation transform are explained. A number of properties of the distributions of occurrence times and interoccurrence times of a nonhomogeneous Poisson process are proved when the mean-value function of the process is convex, starshaped, or superadditive. The same results hold for upper record values of independently identically distributed random variables from IFR, IFRA, and NBU distributions.

Methanogenesis from Methylated Amines in a Hypersaline Algal Mat.

Abstract: Methane ebullition and high rates of methane production were observed in sediments of a hypersaline pond (180 per thousand) which contained sulfate in excess of 100 mM. The highest rates of methane production were observed in surface sediments associated with an algal mat dominated by a Spirulina sp. The mat contained a methylated amine, glycine betaine (GBT), at levels which accounted for up to 20% of the total mat nitrogen. GBT was apparently the source of trimethylamine (TMA), which was also present in the sediment at relatively high concentrations. Patterns of substrate metabolism by the methanogenic populations in sediment slurries suggested that TMA was a major methane precursor. Neither exogenous hydrogen nor acetate stimulated methanogenesis, while addition of a variety of amines including TMA, trimethylamine oxide, GBT, and choline resulted in substantial increases with yields of >70%. The temperature optimum for methanogenesis in this system was 45 to 55 degrees C, which coincided with the observed sediment temperature. Patterns and rates of methane production in this and other hypersaline algal mats may be determined by a complex interaction between salinity, the use of methylated amines for osmoregulation by algae, and the formation of TMA by fermentation.

Fibromyalgia: generalized pain intolerance and manifold symptom reporting.

Abstract: We tested the current criteria for fibromyalgia. Pain tolerance was measured at tender point and control point sites using a pressure algometer, and responses to 6 standard psychological self-reports were obtained from 125 patients with generalized nonarticular rheumatism, rheumatoid arthritis, or osteoarthritis. Among patients with generalized nonarticular rheumatism, published symptom criteria for fibromyalgia did not correlate significantly with the number of tender points. Only lower generalized pressure point pain tolerance distinguished fibromyalgia from other generalized nonarticular rheumatism. Generalized nonarticular rheumatism mean scores were much higher than controls on tests measuring the tendency to report physical symptoms, including headaches and functional bowel syndrome. It is probable that patients with fibromyalgia do not differ in any important physical or psychological respect from other patients with generalized nonarticular rheumatism except for the presence of tender points. However, the presence of tender points is merely a reflection of the patient's general pressure pain sensitivity and is not indicative of any special localized pathological phenomenon. The concept of fibromyalgia as an entity separate from the rest of generalized nonarticular rheumatism may be an artifact of a physician's approach to the patient. Most patients with generalized nonarticular rheumatism demonstrate an abnormally high frequency of reporting manifold disagreeable symptoms and probably come to the attention of many medical disciplines.

Draw resonance in film casting of viscoelastic fluids: A linear stability analysis

Abstract: In order to understand the role of viscoelasticity on draw resonance in the isothermal film casting process, a steady state analysis and a linear stability analysis for three-dimensional flow disturbances have been conducted. The constitutive equation used is a modified convected Maxwell model, with shear-rate dependent viscosity and fluid characteristic time. The numerical results indicate that the flow is stable below a lower critical draw ratio and above an upper critical draw ratio. Shear thinning in viscosity reduces the lower critical draw ratio and somewhat increases the upper critical draw ratio—thereby enlarging the region of instability. Slower shear reduction in fluid characteristic time dramatically decreases the upper critical draw ratio but has no significant effect on the lower critical draw ratio; therefore, fluids with higher characteristic time are more stable.

Soil processes and sulfate loss at the Hubbard Brook Experimental Forest

Abstract: The Hubbard Brook Ecosystem Study was designed to evaluate element flux and cycling in a northern hardwood forest and the effects of disturbance on these processes. In the original experiment, an entire watershed was deforested and regrowth was inhibited for three years using herbicides. Initial effects of the treatment included: elevated stream discharge, large increases in streamwater solute concentrations and elevated losses of those ions from the watershed. In contrast, streamwater concentrations and net ecosystem output of sulfate decreased in response to the treatment. During the post treatment period, the concentrations of most dissolved ions declined relative to a reference watershed while, again in contrast, sulfate concentrations increased relative to the reference. In this paper we develop a hypothesis which links acidification and sulfate adsorption processes in the soil to explain the observed trends in sulfate losses from the Hubbard Brook Experimental Forest.

Halimeda bioherms along an open seaway: Miskito Channel, Nicaraguan Rise, SW Caribbean Sea

Abstract: A recent research cruise to examine small, detached carbonate platforms situated on the Nicaraguan Rise in the SW Caribbean Sea has revealed the presence of numerous Halimeda bioherms. Based upon interpretations from seismic reflection data some exceed 140 m in relief. This is the first documented occurrence of these green-algal buildups in the Caribbean/Bahama Bank region. The Halimeda bioherms form a nearly continuous band that borders the margins of the Miskito Channel—a shallow, open, 125 km long seaway. This 220 m deep channel bisects the Miskito Bank which is a major carbonate shelf. In seismic profile the bioherms appear acoustically “soft” and reveal a local relief of 20–30 m. Tops of these features lie in about 40–50 m of water. Samples from dredge hauls are coarse, poorly cemented packstones/grainstones which are dominated by largely unbroken, disarticulated Halimeda segments set in a poorly sorted sandy matrix. Exposed surfaces were stained brown. Very little living material was brought up in the dredges. The significance of these bioherms and their full extent in the Caribbean are not understood. Undoubtedly, further study will provide important answers concerning their role in the geologic development of Caribbean carbonate platforms.

Efferent neurotransmission of circadian rhythms in Limulus lateral eye

Abstract: We investigated efferent neurotransmission in theLimulus lateral eye by studying the action of pharmacological agents on responses of photoreceptor cells in vitro. We recorded transmembrane potentials from single cells in slices of retina that were excised during the day and maintained for several days in a culture medium. Potentials recorded in the absence of pharmacological agents resemble those recorded from cells in vivo during the day. Octopamine, a putative efferent neurotransmitter, induced changes in photoreceptor potentials that mimicked in part those generated at night by a circadian clock located in the brain. Specifically, octopamine (100 to 500 μM) decreased the frequency of occurrence of quantum bumps in the dark and increased the amplitude of photoreceptor responses to intermediate and high light intensities. Similar actions were produced by naphazoline (25 to 100 (μM, potent agonist of octopamine), forskolin (8 to 400 μM, activator of adenylate cyclase), IBMX (1 mM, inhibitor of phosphodiesterase), and 8-bromo-cAMP (500 μM, analogue of cAMP). 8-bromo-cGMP (500 μM, analogue of cGMP) decreased the rate of spontaneous quantum bumps only. Our results support the hypothesis that (1) octopamine is an efferent neurotransmitter of circadian rhythms in theLimulus eye and that (2) it activates adenylate cyclase to increase levels of the second messenger, cAMP, in photoreceptor cells. Circadian changes in photoreceptor responses to moderate intensities may be a specific action of cAMP, since cGMP has no effect. Circadian changes in the rate of spontaneous quantum bumps may involve a less specific intermediate, since both cAMP and cGMP reduce bump rate. Characteristics of the retinal slice preparation precluded a detailed study of the effects of pharmacological agents on retinal morphology.

Lessons from History: Teacher and Student Conceptions of the Meaning of History

Abstract: The central purpose of this investigation is to describe and analyze teacher and student conceptions of the meaning of history. The study explores factors which shape conceptions of the meaning of ...

The psychophysics of retrospective and prospective timing.

Abstract: In two experiments, different groups of subjects heard four musical selections and then estimated the duration of each selection. Some groups made retrospective time estimates while others made prospective estimates. In both experiments, analyses of the psychophysical relation between perceived and actual duration showed that the slopes of straight-line fits were flatter and accounted for a smaller proportion of the variance under retrospective as compared with prospective conditions. In addition, in experiment 1, retrospective subjects were less accurate in rank ordering the selections from longest to shortest. There was also a serial-order effect, with selections estimated longer when they occurred early in the sequence. In experiment 2 the slopes decreased as the selections in a series became longer. Both retrospective and prospective estimates also exhibited a context effect, in that estimates of a given selection were influenced by the relative durations of the other three selections in the series. T...

Significance of past and recent heat-flow and radioactivity studies in the Southern Rocky Mountains region

Abstract: As reported in The Geological Society of America Bulletin of 1950, Francis Birch's innovative heat-flow research in the Colorado Front Range introduced frequently used terrain correction and thermal-conductivity measurement methods. That report also presented the first empirical evidence for a positive correlation between above-normal flux and radioactive roots in an isostatically compensated mountain area with a thick crust, an observation that strongly influenced continental heat-flow studies for the next 18 years. Birch's Front Range study clearly showed that reliable continental heat-flow research requires knowledge of bedrock radioactivity. This concept reached an unprecedented level of acceptance in 1968, when linear relations between heat flow and radiogenic heat production were discovered for three contrasting provinces in the United States. Subsequently, such lines have been central to virtually all heat-flow and radioactivity research on land. Heat-flow (Q) data for 139 boreholes provide new detail on thermal regimes in the Southern Rocky Mountains and bordering areas, as do radiogenic heat-production (A) data for 60 locales. Interpretations also emphasize reduced and residual heat-flow values; reduced values correspond to the intercepts of regional Q-A lines, whereas a residual value is the flux at a locale after the probable effect of near-surface heat production has been subtracted. The observed Q-A lines demonstrate that the Front Range and other easterly frontal ranges of the Southern Rocky Mountains in Colorado and northern New Mexico are characterized by a reduced flux (54-58 mWm-2) that is dramatically higher than that (∼27 mWm-2) in the Wyoming Basin-Southern Rocky Mountains area in southeastern Wyoming. Because the transitions between these provinces are narrow (≤50-60 km), sources in the upper crust must explain some of the contrasting reduced heat-flow values. In southeastern Wyoming, normal heat flow in Archean and early Proterozoic basement terranes probably reflects deep erosion that produced a thin (∼7 km) near-surface granitic layer that overlies a low-radioactivity lower crust. In the Colorado Front Range, Proterozoic, Mesozoic, and Cenozoic silicic rocks with relatively enriched radiogenic heat could comprise a 20- to 25-km-thick granitic layer in the upper crust that produces a large part of the above-normal reduced and residual flux. Here, partial melting of deep protolithic rocks in late Mesozoic and Cenozoic times could have produced a lower crust with low radiogenic heat production. By these views, Birch's "high heat flow-radioactive mountain root" model of the Colorado Front Range is confirmed if a large part of the topography is isostatically compensated by low-density pre-Miocene crystal-line masses in the upper crust. Background reduced heat flow in Colorado parts of the Southern Rocky Mountains and the eastern Colorado Plateau is high (54-68 mWm-2). Zones of unusually high residual flux (88-118 mWm-2) occur in the Rio Grande rift zone in the environs of the Colorado mineral belt in the Leadville-northern Sawatch Range region, eastern parts of the San Juan Mountains in southern Colorado, and in the Park Range-Mountain Parks area near the Colorado-Wyoming border. The flux in these areas implies unrealistically high equilibrium temperatures near the crustmantle boundary, and the 50- to 60-km-wide borders of the Leadville-northern Sawatch Range residual heat-flow anomaly must be caused by sources in the upper crust. There-fore, young (10- to 1-m.y. -old) intrusions in a late Cenozoic rhyolitic complex in the upper crust are preferred to explain gravity lows, late Cenozoic uplift and igneous activity, and the high residual flux in the Leadville-northern Sawatch Range area. Similar models may apply elsewhere in the northern rift zone. If this interpretation is correct, magmatic thickening of the crust, not extensional-subsidence mechanisms, probably explains late Cenozoic uplift and extension of the northern Rio Grande rift-Southern Rocky Mountains system. Because very high regional flux in the northern rift zone and the San Juan Mountains areas implies above-liquidus equilibrium temperatures in the lower crust and upper mantle, serious inconsistencies arise when steady-state thermal models are examined relative to volumes of late Tertiary volcanism, uniform crustal thickness, and the absence of unusually low P-wave velocities in the mantle in the Southern Rocky Mountains.

Rhythmic activity of migrating juvenile American eels Anguilla rostrata

Abstract: Glass eels of the American eel Anguilla rostrata (Lesueur) utilize selective tidal stream transport, a series of semidiurnal vertical migrations in phase with the tide, to migrate up the Penobscot River estuary, Maine, U.S.A., in the spring. Glass eels, freshly collected during their migration, exhibited rhythmic activity with circatidal periodicities when tested in groups in the presence of a water current under constant conditions in the laboratory. Freshly collected groups of eels which had already completed their migration through tidal water did not exhibit circatidal activity rhythms under the same conditions. The activity rhythms of groups of eels freshly caught in tidal water appeared to be entrained by a 12.5 h cycle of water current reversals, but not by a 10.0 h cycle of current reversals. In other entrainment experiments water collected on flood and ebb tides was alternately added to the experimental tanks every 5.0 h. Under these conditions groups of eels freshly caught in tidal water did not display any rhythmic activity. Only 2 of 100 glass eels, freshly collected from tidal and non-tidal water, which were tested individually in static tanks, exhibited rhythmic activity. The activity rhythms would allow an eel to time its vertical migrations in the estuary despite varying environmental conditions.

Small‐Scale Features of Marine Sediments and Their Importance to the Study of Deposit Feeding

Abstract: Studies on deposit feeders usually involve parallel samples of both the animal of interest and the sediment in which it is living To most benthic ecologists, this means that a ’scoopful’ of sediment from the sample is removed to the laboratory for analysis of organic carbon and nitrogen, various measures of the mineral fraction, and other bulk properties To the organism, features of the sediment such as total weight of ’organic carbon’ per gram dry weight of inorganic material are probably not perceivable On the other hand, the quantity (number of mouthfuls?) of sediment needed in order to obtain sufficient amounts of digestible organic material is probably detected via metabolic feedback If the processes governing the successful maintenance of deposit feeder populations are to be understood, bulk measures of sediment properties must be augmented by methods that will give information relatable to the scale of the organisms under study (see Cammen, this volume) This recommendation was made by Ralph Johnson in 1974, but it has scarcely been heeded He urged benthic ecologists to devise measures of the food resource and its partitioning that were relevant to the requirements and activities of benthic animals In order to do this, biological and chemical techniques must be developed that investigate the environment at the correct spatial scale

Time Course of Acetylene Reduction in Nodules of Five Actinorhizal Genera

Abstract: The rate of acetylene reduction was measured as a function of time after addition of 10% acetylene in Alnus, Casuarina, Ceanothus, Datisca, and Myrica. The maximum rate occurred after 45 to 60 seconds and was maintained for an additional 0.5 to 4 minutes before a decline in rate to 30 to 90% of the maximum. The rate then recovered to a value of 63 to 98% of the maximum. Removal of the shoot and lower roots did not affect nodule activity.