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At least 847 records · Page 47Linked to original sources
USGS2012

Experimentally derived salinity tolerance of hatchling Burmese pythons (Python molurus bivittatus) from the Everglades, Florida (USA)

In a laboratory setting, we tested the ability of 24 non-native, wild-caught hatchling Burmese pythons (Python molurus bivittatus) collected in the Florida Everglades to survive when given water containing salt to drink. After a one-month acclimation period in the laboratory, we grouped snakes into three treatments, giving them access to water that was fresh (salinity of 0, control), brackish (salinity of 10), or full-strength sea water (salinity of 35). Hatchlings survived about one month at the highest marine salinity and about five months at the brackish-water salinity; no control animals perished during the experiment. These results are indicative of a "worst-case scenario", as in the laboratory we denied access to alternate fresh-water sources that may be accessible in the wild (e.g., through rainfall). Therefore, our results may underestimate the potential of hatchling pythons to persist in saline habitats in the wild. Because of the effect of different salinity regimes on survival, predictions of ultimate geographic expansion by non-native Burmese pythons that consider salt water as barriers to dispersal for pythons may warrant re-evaluation, especially under global climate change and associated sea-level-rise scenarios.

Florida↗
USGS2024

Structure and morphology of chars and activated carbons obtained from thermal treatment of coal and biomass origin materials, including their wastes: Results from the ICCP Microscopy of Carbon Materials Working Group

This paper describes the evaluation of petrographic textures in char and activated carbon derived from coal, coal by-products and biomass, formed during carbonization and activation processes. This work represents the results of interlaboratory exercises from 2016 to 2022 of the Microscopy of Carbon Materials Working Group in Commission III of the International Committee for Coal and Organic Petrology. The interlaboratory exercises were run on photomicrograph samples. For textural characterization of carbon materials, the existing American Society for Testing and Materials (ASTM) classification system for metallurgical coke was applied. Morphological differences were evaluated in 29 carbon material types, including 22 char samples, and 7 activated carbon (AC) samples obtained experimentally using conventional direct/indirect and microwave heating technologies. This approach gives an extended view on the identification of microporous carbons, and how a certain heat treatment develops a certain optical texture and structure in a raw material. The requested evaluation of carbon materials was related to their porosity, origin, extent, and characteristics, which are particular to each carbon material type. Because carbon matrices can form a wide range of optical textures during heat treatment it is important to demonstrate which carbon occurrences will have a crucial role in industrial applications dominated by adsorption phenomena. The interlaboratory exercises included 17 participants from 14 laboratories. Four sets of digital black and white and colour photomicrographs were distributed, which in total comprised 184 fields of different types of carbon material. The results were evaluated based on four levels: (i) optical texture (isotropic/anisotropic), (ii) optical type and size (punctiform, mosaic, fiber, ribbon, domain), iii) morphology (porous, non-porous/massive), and (iv) particle origin (precursor type). The statistical method applied to evaluate the results was based on “raw agreement indices”. Comparative analyses of the average values of the level of overall agreement showed homogeneity in the results, the mean value was 89%, with a minimum value of 87% and a maximum value of 91% for those who participated in at least three out of four exercises.

International Journal of Coal Geology↗
USGS2025

Bait trapping of waterfowl increases the environmental contamination of avian influenza virus (AIV)

Highly pathogenic avian influenza virus (HPAIV) H5Nx clade 2.3.4.4b has circulated in North America since late 2021, resulting in higher rates of morbidity and mortality in wild birds than observed in this region before. The objective of this study was to determine whether baiting, which is widely conducted in Canada and the United States as part of waterfowl management practices (e.g., duck banding), influences the occurrence of avian influenza virus (AIV) in wetlands. We used a quasi-experimental design, collecting superficial sediment samples ( n = 336) and fecal samples ( n = 242) from paired baited (treatment) and non-baited (control) sites at 2 wetlands in Saskatchewan, Canada, between August and September 2022. We visited sampling sites 3 times during the sampling period: prior to the commencement of baiting activities ( t0 ), approximately 14 days after t0 ( t1 ), and 24 days after t0 ( t2 ). We screened samples for AIV using real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) targeting the matrix gene and subjected the PCR-positive samples to next-generation sequencing. We used a mixed-effects logistic regression model to estimate the effect of baiting on the odds of AIV positivity in sediment samples, while controlling for clustering by wetland. At control sites, we did not detect evidence for a difference in the odds of AIV detection in sediment at t1 or t2 versus t0 ; however, at baited sites, the odds of AIV detection at t1 were 5.43 (95% CI = 1.99, 14.79) times the odds at t0 and at t2 the odds of AIV detection were 8.73 (95% CI = 3.29, 23.18) times the odds at t0 . We detected HPAIV clade 2.3.4.4b H5N1 in sediment at 1 treatment site following baiting. There was also a trend towards increased fecal AIV positivity and increased fecal and sediment AIV diversity in baited versus non-baited sites; however, there was insufficient power to determine if these findings were statistically significant. Overall, our results indicate that baiting is associated with localized increases in AIV environmental contamination, with baiting potentially creating concentrated areas of AIV accumulation. As such, wetland baiting activities may pose a risk to wildlife population health through the propagation of AIV in wetlands and the waterfowl using those environments and efforts to replace, refine, or reduce this activity may be warranted depending on local ecosystem contexts and cost-benefit analyses.

Saskatchewan↗
USGS2014

Effects of smallmouth buffalo, Ictiobus bubalus biomass on water transparency, nutrients, and productivity in shallow experimental ponds

The smallmouth buffalo Ictiobus bubalus is a native benthivore to floodplain lakes in the Yazoo River Basin, USA. Based on evidence from other benthivorous fish studies we hypothesized high biomasses of I. bubalus contribute to poor water quality conditions. We tested this hypothesis in shallow (< 1.5 m) 0.05 ha earthen ponds at three stocking biomasses over a 10-week period during the summer of 2012. The most notable results from the permutational multivariate analysis of variance suggest I. bubalus at high and moderate biomasses significantly (p < 0.05) enhanced turbidity and suspended solid levels while decreasing Secchi depth. Our results suggest that effects of I. bubalus on water clarity may have considerable ecological implications in natural habitats such as shallow floodplain lakes.

Bulletin of Environmental Contamination and Toxico↗
USGS2024

Biocrusts modulate carbon losses under warming across global drylands: A bayesian meta-analysis

Biocrusts are critical biological components of drylands and play an important role in soil carbon (C) cycling. However, the effect of biocrusts on soil CO 2 exchange across global gradients of temperature and moisture is poorly understood. Moreover, their response to climate change remains highly uncertain. Bayesian hierarchical meta-analyses were performed on 47 published studies to quantify the impact of biocrusts on net soil exchange (NSE) of carbon- the difference between respiration and photosynthesis. Meta-analyses were also used on 23 studies to examine the effects of experimental warming on NSE in biocrusts. Meta-regressions further explored the thermal and wetness sensitivities of biocrust NSE and potential adaptation of biocrust responses to climate change. The development of biocrusts in dryland soils significantly increased NSE by 66.5 [22.2, 112.2] g C m −2 yr −1 , despite seasonal fluctuations, indicating a net loss of carbon to the atmosphere. Experimental warming, on average, increased biocrust NSE by 22.9 [-0.1, 40.8] g C m −2 yr −1 per °C. However, across the spatial climate gradient, aridity limited the effects of warming, while high temperature decreased the thermal sensitivity of biocrust NSE, thus supporting the thermal adaptation of biocrusts. These results emphasize the critical role of biocrusts in modulating soil carbon exchange in response to climate warming across drylands, with particularly high thermal sensitivity in cool and moist regions. This highlights the need to incorporate biocrusts into global carbon budgets and models for a comprehensive understanding of their impact on the carbon cycle.

Soil Biology and Biogeochemistry↗
USGS1999

Dietary and culture influences on macrophage aggregate parameters in gilthead seabream (Sparus aurata) juveniles

Macrophage aggregates (MAs) are structures in the spleen, kidney and sometimes liver of fishes which have various functions such as recycling/storing/detoxification of cellular wastes and exogenous substances. They have been also reported to be important in the specific immune response and are used as health indicators. Changes in MA density, size and pigment content have been used in national and local monitoring programs in the U.S. as indicators of contaminant exposure. However, MA number and structure can also be affected by other factors, including general stress or nutritional status of fish. An experiment was conducted to study the effects of vitamin E and n −3 highly unsaturated fatty acid (HUFA) deficiencies and stocking density on spleen and kidney MAs of gilthead seabream, one of the most important species for Mediterranean aquaculture. Fish were held at two stocking densities, high and low, and fed experimental diets. Diet NE had no supplemental vitamin E, Diet NFA was deficient in n −3 HUFA and Diet C was a control diet. Number, size and shape factor of MAs were measured using image analysis. The percentage of tissue occupied by MAs was calculated from these measurements. The results showed that high stocking density alone increased the number of splenic but not kidney MAs of fish fed the control diet. A deficiency of n −3 HUFA alone also increased the number of splenic but not kidney MAs at both stocking densities. Vitamin E deficiency alone had no significant effect on MAs in either organ. However, the combined effect of vitamin E deficiency and high stocking density increased the number and size of kidney but not splenic MAs. This study indicates that specific dietary deficiencies can influence MA accumulation and that splenic MAs may be more responsive to general stress than kidney MAs.

Aquaculture↗
USGS2010

Ways of learning: Observational studies versus experiments

Manipulative experimentation that features random assignment of treatments, replication, and controls is an effective way to determine causal relationships. Wildlife ecologists, however, often must take a more passive approach to investigating causality. Their observational studies lack one or more of the 3 cornerstones of experimentation: controls, randomization, and replication. Although an observational study can be analyzed similarly to an experiment, one is less certain that the presumed treatment actually caused the observed response. Because the investigator does not actively manipulate the system, the chance that something other than the treatment caused the observed results is increased. We reviewed observational studies and contrasted them with experiments and, to a lesser extent, sample surveys. We identified features that distinguish each method of learning and illustrate or discuss some complications that may arise when analyzing results of observational studies. Findings from observational studies are prone to bias. Investigators can reduce the chance of reaching erroneous conclusions by formulating a priori hypotheses that can be pursued multiple ways and by evaluating the sensitivity of study conclusions to biases of various magnitudes. In the end, however, professional judgment that considers all available evidence is necessary to render a decision regarding causality based on observational studies.

Journal of Wildlife Management↗
USGS1954

Relationship of length of fish to incidence of sea lamprey scars on white suckers, Catostomus commersoni, in Lake Huron

During the course of experimental fishing operations conducted by the staff of Hammond Bay Fishery Laboratory (a field station of Great Lakes Fishery Investigations) in 1950-1951, length measurements and records of scarring incidence and number of scars per individual were obtained for a sample of 552 white suckers, Catostomus commersoni (Lacepede). The results of this study indicate that if information on the incidence of sea lamprey scars on white suckers is to be used to judge the relative abundance of sea lampreys and the damages inflicted by that parasite on the sucker stock, data must include records of the lengths of fish. It is to be suspected strongly that a similar conclusion applies in other localities and to other species preyed upon by the sea lamprey.

Copeia↗
USGS2015

Pulse-drought atop press-drought: unexpected plant responses and implications for dryland ecosystems

In drylands, climate change is predicted to cause chronic reductions in water availability (press-droughts) through reduced precipitation and increased temperatures as well as increase the frequency and intensity of short-term extreme droughts (pulse-droughts). These changes in precipitation patterns may have profound ecosystem effects, depending on the sensitivities of the dominant plant functional types (PFTs). Here we present the responses of four Colorado Plateau PFTs to an experimentally imposed, 4-year, press-drought during which a natural pulse-drought occurred. Our objectives were to (1) identify the drought sensitivities of the PFTs, (2) assess the additive effects of the press- and pulse-drought, and (3) examine the interactive effects of soils and drought. Our results revealed that the C 3 grasses were the most sensitive PFT to drought, the C 3 shrubs were the most resistant, and the C 4 grasses and shrubs had intermediate drought sensitivities. Although we expected the C 3 grasses would have the greatest response to drought, the higher resistance of C 3 shrubs relative to the C 4 shrubs was contrary to our predictions based on the higher water use efficiency of C 4 photosynthesis. Also, the additive effects of press- and pulse-droughts caused high morality in C 3 grasses, which has large ecological and economic ramifications for this region. Furthermore, despite predictions based on the inverse texture hypothesis, we observed no interactive effects of soils with the drought treatment on cover or mortality. These results suggest that plant responses to droughts in drylands may differ from expectations and have large ecological effects if press- and pulse-droughts push species beyond physiological and mortality thresholds.

Oecologia↗
USGS1990

Use of triticale as a replacement for wheat middlings in diets for Atlantic salmon

A study was conducted to determine the value of triticale (a hybrid between rye and wheat) as a substitute for wheat middlings in the diet of Atlantic salmon ( Salmo salar ). Data on growth and carcass composition of fish fed the experimental diets containing triticale were comparable to those of fish fed the control diet with wheat middlings. No differences in diet acceptability were apparent when triticale was substituted for wheat middlings in the basal ration. Though the effect of triticale substitution on pellet quality (i.e., durability) is not known, the results indicated that this hybrid grain can be used as a nutritional substitute for wheat middlings in the diet of salmonids, and that further evaluation of this potential feed ingredient is warranted.

Aquaculture↗
USGS2020

Sphalerite oxidation in seawater with covellite: Implications for seafloor massive sulfide deposits and mine waste

Metal sulfide minerals exist in several marine environments and are in thermodynamic disequilibrium with oxygenated seawater from the time of their formation. Oxidation is both ubiquitous and heterogeneous, as observational and experimental evidence demonstrates that sulfide minerals may oxidize completely on decadal timescales (hydrothermal plumes) or incompletely in billions of years (mineral deposits); however, the processes, rates, and interactions among minerals as oxidative dissolution occurs are not well understood. Added impetus to understanding these processes exists due to the potential for mining of seafloor massive sulfide deposits and potential environmental impacts of that activity. Here, we present a laboratory-based experimental study on the galvanic oxidation of sphalerite and synthesized zinc sulfide and coupled to covellite. We find that, in contrast to single-mineral reactions, coupled mineral reactions are at least 2 orders of magnitude more rapid, light independent, and have a lower apparent activation energy for oxidation. These results begin to provide insight into observed differences between laboratory and environmentally observed oxidation rates and are a step in the direction of more accurately predicting environmental rates as well as any changes to those rates from anthropogenic disturbances.

ACS Earth and Space Chemistry↗
USGS2003

Effects of a fire-retardant chemical to fathead minnows in experimental streams

Background Each year millions of liters of fire-retardant chemicals are applied to wildfires across the nation. Recent laboratory studies with long-term fire-retardant chemicals indicate a significant photoenhanced toxicity of products containing sodium ferrocyanide corrosion inhibitors. Our objective of this study was to determine the toxicity of fire-retardant chemicals to fathead minnows during exposure in experimental outdoor streams. Methods Stream tests were conducted to determine the potential toxicity of a pulse of exposure as might occur when fire retardant chemical is rinsed from the watershed by rainfall. Two artificial 55-meter experimental streams were dosed with different concentrations of Fire-Trol® GTS-R, or uncontaminated for a control. Replicate groups of fathead minnows were added to screened containers (10 fish per container) and exposed to retardant chemicals in the recirculating flow of the stream for up to 6 hours. Results and Discussion Under field conditions toxicity of GTS-R only occurred in the presence of sunlight. When GTS-R was tested on sunny days, 100% mortality occurred. However, when tested during heavily overcast conditions, no mortality occurred. Conclusions Lethal concentrations of cyanide were measured when GTS-R with YPS exposures were conducted under sunny conditions, but not under cloudy conditions, indicating that a minimum UV level is necessary to induce toxicity as well as the release of cyanide from YPS. The toxicity observed with GTS-R was likely associated with lethal concentrations of cyanide. Rainwater runoff following applications of this fire-retardant at the recommended rate could result in lethal concentrations in small ponds and streams receiving limited water flow under sunny conditions.

Environmental Science and Pollution Research↗
USGS2007

A hybrid optimization approach to the estimation of distributed parameters in two-dimensional confined aquifers

ABSTRACT: In using non-linear optimization techniques for estimation of parameters in a distributed ground water model, the initial values of the parameters and prior information about them play important roles. In this paper, the genetic algorithm (GA) is combined with the truncated-Newton search technique to estimate groundwater parameters for a confined steady-state ground water model. Use of prior information about the parameters is shown to be important in estimating correct or near-correct values of parameters on a regional scale. The amount of prior information needed for an accurate solution is estimated by evaluation of the sensitivity of the performance function to the parameters. For the example presented here, it is experimentally demonstrated that only one piece of prior information of the least sensitive parameter is sufficient to arrive at the global or near-global optimum solution. For hydraulic head data with measurement errors, the error in the estimation of parameters increases as the standard deviation of the errors increases. Results from our experiments show that, in general, the accuracy of the estimated parameters depends on the level of noise in the hydraulic head data and the initial values used in the truncated-Newton search technique.

Journal of the American Water Resources Associatio↗
USGS2009

Modeling the effects of environmental disturbance on wildlife communities: Avian responses to prescribed fire

Prescribed fire is a management tool used to reduce fuel loads on public lands in forested areas in the western United States. Identifying the impacts of prescribed fire on bird communities in ponderosa pine (Pinus ponderosa) forests is necessary for providing land management agencies with information regarding the effects of fuel reduction on sensitive, threatened, and migratory bird species. Recent developments in occupancy modeling have established a framework for quantifying the impacts of management practices on wildlife community dynamics. We describe a Bayesian hierarchical model of multi-species occupancy accounting for detection probability, and we demonstrate the model's usefulness for identifying effects of habitat disturbances on wildlife communities. Advantages to using the model include the ability to estimate the effects of environmental impacts on rare or elusive species, the intuitive nature of the modeling, the incorporation of detection probability, the estimation of parameter uncertainty, the flexibility of the model to suit a variety of experimental designs, and the composite estimate of the response that applies to the collection of observed species as opposed to merely a small subset of common species. Our modeling of the impacts of prescribed fire on avian communities in a ponderosa pine forest in Washington indicate that prescribed fire treatments result in increased occupancy rates for several bark-insectivore, cavity-nesting species including a management species of interest, Black-backed Woodpeckers (Picoides arcticus). Three aerial insectivore species, and the ground insectivore, American Robin (Turdus migratorius), also responded positively to prescribed fire, whereas three foliage insectivores and two seed specialists, Clark's Nutcracker (Nucifraga columbiana) and the Pine Siskin (Carduelis pinus), declined following treatments. Land management agencies interested in determining the effects of habitat manipulations on wildlife communities can use these methods to provide guidance for future management activities. ?? 2009 by the Ecological Society of America.

Ecological Applications↗
USGS2006

Determination of the platinum - Group elements (PGE) and gold (Au) in manganese nodule reference samples by nickel sulfide fire-assay and Te coprecipitation with ICP-MS

Platinum group elements (PGE) and Au data in polymetallic oceanic ferromanganese nodule reference samples and crust samples obtained by inductively coupled plasma mass spectrometry (ICP-MS), after separation and pre-concentration by nickel sulfide fire-assay and Te coprecipitation, are presented. By optimizing several critical parameters such as flux composition, matrix matching calibration, etc., best experimental conditions were established to develop a method suitable for routine analysis of manganese nodule samples for PGE and Au. Calibrations were performed using international PGE reference materials, WMG-1 and WMS-1. This improved procedure offers extremely low detection limits in the range of 0.004 to 0.016 ng/g. The results obtained in this study for the reference materials compare well with previously published data wherever available. New PGE data arc also provided on some international manganese nodule reference materials. The analytical methodology described here can be used for the routine analysis of manganese nodule and crust samples in marine geochemical studies.

Indian Journal of Marine Sciences↗
USGS2020

A 450-year record of environmental change from Castle Lake, California (USA), inferred from diatoms and organic geochemistry

A 39-cm sediment core from Castle Lake, California (USA) spans the last ~ 450 years and was analyzed for diatoms and organic geochemistry (δ 15 N, δ 13 C, and C:N), with the goal of determining sensitivity to natural climate variation and twentieth century anthropogenic effects. Castle Lake is a subalpine, nitrogen-limited lake with ~ 5 months of annual ice cover. Human impacts include light recreational use, past fish stocking, and experimental use by the Castle Lake Research Station. The base of the core (below 32 cm; pre mid-1700s) represents the period of maximum ice cover. In contrast, the end of the Little Ice Age (mid 1700s–early 1800s) is dominated by cyclotelloids (mostly Discostella stelligera ), indicating significant open-water periods, a condition that persisted into the early 1900s. Cyclotelloids began to decline in the 1960s and were replaced by the Fragilaria tenera grp. (peak in 1970s), succeeded by Asterionella formosa (peak ~ 2010), and accompanied by a reduction in δ 15 N values and a decrease in C:N that may represent increased atmospheric nitrogen deposition. Another anthropogenic signal was discerned in the core and was interpreted to be the result of an ammonium nitrate fertilization experiment of the epilimnion that was conducted in 1980 and 1981. This signal was manifested in the core largely by a negative excursion in δ 15 N, possibly caused by fractionation during denitrification in surface sediment. A phytoplankton monitoring dataset collected by the Castle Lake Research Station from 1967 to 1984 corroborates the timing of increased araphid euplanktonic species in the 1970s, and increases in two benthic diatoms ( Staurosirella pinnata and Tabellaria fenestrata) , entrained in the phytoplankton tows during the experimentation years. Both ice cover and nitrogen addition appear to be strong drivers that affected the lake diatoms, although additional drivers, such as fish stocking and associated cascade effects need further exploration. These data will be helpful for interpreting longer core records from Castle Lake, should the opportunity arise, as well as cores from similar systems in the region.

California↗
USGS1990

Radarclinometry of the Earth and Venus from space-shuttle and Venera-15 imagery

The project to develop a line-integral approach to 2-dimensional radarclinometry and to bring it to the status of producing topographic maps from real radar images has been concluded. The final developments of the theory itself have involved a trial-and-error resolution of the curvature decision process at each integration step over range as follows: (1) Locally Indeterminate Azimuth-Azimuth Curvature is invoked if the range-directed path of integration is within 1 ??? in angle of the tangent to a local characteristic curve of the partial differential equation of radarclinometry (equivalent to a lapse in the necessity for an auxiliary curvature assumption); (2) Local Cylindricity is invoked if the local image isophote has a radius-of-curvature greater than 50 pixels; (3) Least-Squared Local Sphericity is invoked if the characteristic curve trends at greater than 70 ??? to the range direction (the auxiliary curvature assumption is becoming a sufficiently strong influence as to warrant the overconstraint), and (4) the default hypothesis, which is invoked most often, is the localization through the Euler/Lagrange equation from the calculus of variations of the global principle of minimization of the surface area of the terrain. The development of the set of line integrals into a 2-dimensional topographic surface is not practically achieved by branching the line integral at the range threshold, because the radarclinometry equations are too frequently coupled but weakly to the slope component in the direction of radar-azimuth, and under circumstances for which the powerfully influential auxiliary curvature assumption is too unrealistic. In other words, a line integration in radar-azimuth is far more frequently directed orthogonally to the local characteristic curve than is one carried out over range. Such orthogonality results in stepping the strike under the exclusive control of the curvature assumption. Instead, a quasi-surface-integration step is taken by modeling the dependence on initial strike of the gravitational potential energy of the vertical slab of terrain under the range-profile. The adopted starting strike for the range integral is the one which minimizes the gravitational potential energy. This radarclinometric method, in combination with my recently published method for determining an effective radar back-scattering function from one-dimensional slope statistics and image pixel-signal statistics, was applied to three images. First, to separate theoretical difficulties from experimental impediments, an artificial radar image was generated from a topographic map of the Lake Champlain West quadrangle in the Adirondack Mountains. Except for the regional trend in elevation, to which radarclinometry is insensitive by design, the agreement between the original and derived topography appears good. The morphologies agree and the range of relief is the same to within 4%. As an example of data of the highest quality available from space-borne radar at the present time, a SIR-B image of very rugged terrain in the coastal mountains of Oregon was similarly processed. The result, after filtering to redistribute photoclinometric errors about the two-dimensional spatial spectrum, agrees with ground truth almost as well. As an example of the worst possible data, in terms of signal-to-noise ratio and radar incidence angle (no detraction from the praise due the first high resolution space-borne radar-imaging of Venus intended), a Venera-15 image segment in Sedna Planitia just north-east of Sapho was processed, using Venera altimetry and Pioneer roughness data for slope statistics, in spite of the resolution mis-match. Considerably more trial-and-error filtering was required. The result appears plausible, but an error check is, of course, impossible. ?? 1990 Kluwer Academic Publishers.

Earth, Moon and Planets↗
USGS1988

Food availability controls seasonal cycle of growth in Macoma balthica (L.) in San Francisco Bay, California

A 2-yr field study of growth in the bivalve Macoma balthica (L.) at four locations in San Francisco Bay, California, U.S., showed that the timing and rate of growth (increase in shell length) were related to food supply. This clam feeds on both planktonic and benthic microalgae, depending on availability. Growth was apparently food-limited during some months, during one year more than the other, and at some locations more than others. Tissue-weight changes were also related to food availability. The heaviest animals were found in that year and at those locations with the highest chl a concentrations. Tissue-weight gains usually coincided with increased shell-growth rate or with reproductive development, although some large animals showed weight gain independent of both of these factors during periods with mid-range chl a levels. Weight losses coincided with spawning or periods of low growth rate, except at one station where, during a period when most animals were reproductively ripe, food concentrations were high, and shell growth was rapid, animals lost weight. This study failed to show a relation between salinity and the timing or rate of change of either shell length or tissue weight. The mild temperatures (10-23 ??C water temperature) of the area studied resulted in no growth inhibition due to low temperature, but there was some indication that the high air temperatures found in these intertidal areas limited growth rates. ?? 1988.

Journal of Experimental Marine Biology and Ecology↗