Ammonium and free amino acid uptake by a deep-sea mussel (Bathymodiolus sp., undescribed) containing methanotrophic bacterial symbionts

The morphology of the lophophore and mouth was measured for freshly collected colonies of seven common bryozoan reef species at three sites along the central Caribbean coast of Panamá during the dry season, from the end of December 1988 through May 1989. Characters measured or scored include the number of tentacles, circumference of the lophophore, abanal and anal tentacle length, abanal and anal tentacle spacing, and perimeter of the mouth. Taxa studied include three species each of Stylophoma Levinsen, and Steginoporella (Smitt), and one species of Trematooecia Osburn. Individuals were collected from both continental and offshore fringing reefs from depths of 1 to>30 m. Terrestrial runoff from heavy tropical rains, sedimentation, and sea exposure vary greatly between sites. Congeneric species showed small but consistent differences in lophophore size, but little or no difference in spacing of tentacles or perimeter of the mouth. This suggests that closely related species feed on similarly sized particles despite their overall differences in zooidal size. Lopophore morphology also varied intraspecifically between reefs, particularly in the length of the tentacles and spacing between tentacles. Patterns of variation were similar for all species, which implies that species shift their diets in similar directions between the different reefs. The combination of these patterns suggests that niche diversification in feeding does not occur among congeneric species in the cheilostomes examined.     

A social appraisal of beverage containers recycling : A UK perspective

A social appraisal of the beverage container involves assessment of external costs. Analysis of available data shows that the returnable generates less external costs than the non-returnable, though refinement of the UK situation requires more detailed data. The ranking depends on the returnable's trippage rate, but it seems the returnable can achieve the trippage needed to make it socially preferable.     

The role of scientific studies in building consensus in environmental decision making: a coral reef example

We present a new approach for characterizing the potential of scientific studies to reduce conflict among stakeholders in an analytic-deliberative environmental decision-making process. The approach computes a normalized metric, the Expected Consensus Index of New Research (ECINR), for identifying where additional scientific research will best support improved decisions and resolve possible conflicts over preferred management actions. The ECINR reflects the expected change in agreement among parties over preferred management actions with the implementation and consideration of new scientific studies. We demonstrate the ECINR method based on a preliminary application to coral reef protection and restoration in the Guánica Bay Watershed, Puerto Rico, focusing on assessing and managing anthropogenic stressors, including sedimentation and pollution from land-based sources such as sewage, agriculture, and development. Structured elicitations of values and beliefs conducted at a coral reef decision support workshop held at La Parguera, Puerto Rico, are used to develop information for illustrating the methodology. The ECINR analysis was focused on a final study group of seven stakeholders, consisting of resource managers and scientists, who were not in agreement on the efficacy and respective benefits of reducing loadings from three sources: sewage, agriculture, and development. The scenario assumed that loadings would be reduced incrementally from each source through a series of management steps, which would be ranked in order of maximizing anticipated benefits. An examination of whether beliefs exhibited greater confidence and coherence between stakeholders when informed by plausible study results followed. The results suggest that new scientific research would be generally likely to bring people who initially disagreed to agree. Seventy-five percent of the hypothetical research results were projected to result in more agreement among the stakeholders. However, there can be situations where prior beliefs may be too different from the study results to shift perspectives enough to result in more agreement. Furthermore, in a few cases, hypothetical research results were projected to lead to more conflict among stakeholders. Priority research, according to the seven stakeholders, would be to quantify loadings from agriculture and sewage, and not loadings from development, since it is predicted to make little difference in the outcome. Assuming the stakeholders are conflict-averse, they would likely opt for research on sewage loadings as the highest priority. Though preliminary, these results suggest that ECINR can provide useful insights into the social implications of a research program.     

Metabolic maintenance costs of the suspension feeder Styela plicata

The bioenergetic basis of the biannual reproductive cycle of the solitary tunicate Styela plicata was investigated in order to evaluate hypotheses concerning the lack of larval settlement in summer. The rate of ingestion and absorption efficiency were measured in order to provide an estimate of the rate at which material was made available for maintenance, growth, and reproduction. At a given temperature the rate of ingestion was proportional to the 0.7 power of wet mass. the ingestion rate increased rapidly with increasing temperature between 12° and 18°C (Q₁₀3), but was independent of temperature between 18° and 28°C. Absorption efficiency was independent of temperature and body size and averaged approximately one-third for both carbon and nitrogen. Metabolic maintenance costs were estimated from measurements of oxygen consumption and excretion of ammonia and urea reported for s. plicata. These require only 18±11% of the carbon and 37±22% of the nitrogen absorbed from the gut of S. plicata over the temperature range 12° to 28°C. Metabolic maintenance makes no excessive demands on the material absorbed in the gut at a particular time of year, and a surplus of carbon and nitrogen substrate is available throughout the year for growth and reproduction. Predation on larvae and young adults may be responsible for the low rate of settlement observed in summer months.     

Heavy metals and marine diatoms: Influence of dissolved organic compounds on toxicity and selection for metal tolerance among four species

Experiments were conducted to determine whether diatom clones isolated from waters (Corio Bay or Hobson's Bay, Australia) chronically contaminated with heavy metals were more metal-resistant than clones of the same species isolated from cleaner waters (Bass Strait). Four species (2 clones per species) and 3 metals (Cu, Zn, Cd) were examined. The growth response of each clone to metal additions was assessed in both Corio Bay water and Bass Strait water. Generally, Cu was readily chelated and the most toxic metal and Cd the least chelated and least toxic. Toxicity of Cu to growth was found to be directly related to cellular Cu levels, which in turn were mediated by dissolved organic compounds in seawater. Corio Bay water had a greater metal-complexing capacity than Bass Strait water, and metal additions generally proved more toxic to each clone when in Bass Strait water. Ultraviolet irradiation eliminated differences between the water types. Relative to Bass Strait clones, no trend of enhanced metal tolerance was noted among the Corio Bay and Hobson's Bay clones; on the contrary the Corio Bay and Hobson's Bay cells were generally less to lerant of metals than were their Bass Strait counterparts, being particularly affected when in Bass Strait water. The results suggest that metal additions to waters rich in dissolved organic compounds would likely have less effect (in terms of direct toxicity and as a selective agent for metal tolerance) on resident phytoplankters than similar additions to waters low in organics.Publication No. 274 in the Ministry for Conservation, Environmental Studies Series     

Odor familiarity and female preferences for males in a threatened primate,the pygmy loris<Emphasis Type="Italic"> Nycticebus pygmaeus</Emphasis>: applications for genetic management of small populations

Here we use sexual selection theory to develop a logistically simple, yet effective, method for the manipulation of female reproductive behavior for conservation goals. Mate choice leading to nonrandom mating patterns can exacerbate the loss of genetic diversity in small populations. On theoretical grounds, females should choose high-quality mates. A prediction stemming from chemical communication theory is that competitive males will be better able to saturate an area with scent marks. If this is true, females should mate preferentially with males whose odors they encounter most frequently. We tested this hypothesis with the pygmy loris, Nycticebus pygmaeus, a threatened and poorly studied nocturnal prosimian. For several weeks females were exposed repeatedly to the urine from a particular male, and were then allowed to choose between a male whose odors were familiar and one whose odors were novel. Females showed an unusually strong preference for the familiar-odor male, as indicated by several behavioral measures of mate preference. Conservation managers can use this method as a tool to obtain reproductive pairings that will maximize genetic compatibility and diversity. For example, unsuccessful males may be given the opportunity to reproduce. In captive populations, studbook managers often select pairs in order to optimize outbreeding, but these selected pairings may not coincide with the preferences of the individual animals involved. Although several authors have made theoretical arguments for manipulating mate choice for conservation, this is a novel test of a proximate mechanism that can be manipulated, cultivating applications rather than mere implications.     

The methane mussel: roles of symbiont and host in the metabolic utilization of methane

Methane mussels (Bathymodiolus sp., undescribed; personal communication by R. Turner to CRF) were collected in September 1989 and April 1990 from offshore Louisiana in the Gulf of Mexico. These mussels contain endosymbiotic methane-oxidizing bacteria and are capable of utilizing environmental methane as a source of energy and carbon. Oxygen consumption, methane consumption, and carbon dioxide production were measured in mussels with intact symbionts, functionally aposymbiotic mussels, and separated symbiont preparations under controlled oxygen and methane conditions, in order to study the roles of the symbionts and the hosts in methane utilization. The association was found to be very efficient in fixing methane carbon (only 30% of CH₄ consumed is released as CO₂), and to be capable of maximal rates of net carbon uptake of nearly 5 mol g^-1 h^-1. Rates of oxygen and methane consumption were dependent upon oxygen and methane concentrations. Maximal consumption rates were measured at 250 to 300 M O₂ and 200 to 300 M CH₄, under which conditions, oxygen consumption by the gill tissues (containing symbionts) had increased more than 50-fold over rates measured in the absence of methane. A model is proposed for the functioning of the intact association in situ, which shows the symbiosis to be capable of achieving growth rates (net carbon assimilation) in the range of 0.003 to 0.50% per day depending upon oxygen and methane concentrations. Under the conditions measured in the seep environment (200 M O₂, 60 M CH₄), a mussel consuming methane at rates found to be typical (4 to 5 mol g^-1 h^-1) should have a net carbon assimilation rate of about 0.1% per day. We suggest that the effectiveness of this symbiosis arises through integration of the morphological and physiological characteristics inherent to each of the symbiotic partners, rather than from extensive specialization exhibited by other deep-sea chemotrophic associations.