162,291 research outputs found
Impact of the infaunal Manila clam, Ruditapes philippinarum, on sediment stability.
No full textThe interactions between physical, chemical and biological processes influencing lagoonal and coastal bottoms are poorly understood, despite their ecological and economic importance in relation to aquaculture, and particularly shellfish farming. In such systems, it is known that the biota may play an important role in determining the erosion potential of intertidal and subtidal sediments. An increase in erosion rate may result from bioturbation due to burrowing organisms, particularly bivalves, associated with physical disturbance due to tidal currents. Within this framework, a laboratory benthic annular flume system (AFS) was deployed to evaluate the relationship between sediment stability of a subtidal mudflat and density of the infaunal Manila clam, Ruditapes philippinarum, under the influence of different current velocities. There was a significant correlation between mean erosion rate and current velocities in all treatments with clams (P < 0.001). There was also a significant correlation between mean erosion rate and R. philippinarum density (P < 0.001), reflecting bioturbation enhanced sediment erosion. The effects of clam density on sediment erodibility were more marked at the lower current velocities. In the control, the critical erosion velocity (Ūcrit) was about 32 cm s-1. With increasing R. philippinarum density, Ūcrit decreased down to the minimum value of about 20 cm s-1 at a density of 206 clams m-2. Our study led to the conclusion that the burrowing activity of R. philippinarum reduces sediment stability, particularly at relatively low current velocities (25 cm s-1) and at densities below those found in the clam cultivation areas
Parameterisation of bivalve functional traits for mechanistic eco-physiological Dynamic Energy Budget (DEB) models
No full textMechanistic models such as those based on dynamic energy budget (DEB) theory are emergent ecomechanics tools to investigate the extent of fitness in organisms through changes in life history traits as explained by bioenergetic principles. The rapid growth in interest around this approach originates from the mechanistic characteristics of DEB, which are based on a number of rules dictating the use of mass and energy flow through organisms. One apparent bottleneck in DEB applications comes from the estimations of DEB parameters which are based on mathematical and statistical methods (covariation method). The parameterisation process begins with the knowledge of some functional traits of a target organism (e. g. embryo, sexual maturity and ultimate body size, feeding and assimilation rates, maintenance costs), identified from the literature or laboratory experiments. However, considering the prominent role of the mechanistic approach in ecology, the reduction of possible uncertainties is an important objective. We propose a revaluation of the laboratory procedures commonly used in ecological studies to estimate DEB parameters in marine bivalves. Our experimental organism was Brachidontes pharaonis. We supported our proposal with a validation exercise which compared life history traits as obtained by DEBs (implemented with parameters obtained using classical laboratory methods) with the actual set of species traits obtained in the field. Correspondence between the 2 approaches was very high (>95%) with respect to estimating both size and fitness. Our results demonstrate a good agreement between field data and model output for the effect of temperature and food density on age-size curve, maximum body size and total gamete production per life span. The mechanistic approach is a promising method of providing accurate predictions in a world that is under in creasing anthropogenic pressure
Influence of biota on spatial and temporal variation in sediment erodability and material flux on a tidal flat (Westerschelde, The Netherlands)
No full textAnnular flumes were used to quantify benthic-pelaqic exchanges in relation to changes in current velocity and sediment biota. Various physical, chemical and biological parameters were determined for 4 sites on the Molenplaat tidal flat in the Westerschelde (The Netherlands) during 2 field campaigns in May-June and August-September 1996. These Pcluded: the mass of sediment eroded, maximum and mean erosion rates, critical erosion velocity (Ucrit), suspension feeding/biodeposition rate, oxygen and ammonium fluxes, density of macrofauna species, chlorophyll a (chl-a), colloidal carbohydrate, and physical properties of the sediment. The study showed marked and statistically significant spatial and temporal differences in the potential for sediment erosion. Sites in the centre of the tidal flat were less erodable than those on the edge. All sites on the tidal flat had a significantly (p < 0.001) lower erosion potential in June (i.e. higher Ucrit and lower erosion rates) compared to September. The presence of a well-developed microphytobenthos community in June resulted in a statistically significant relationship between Ucrit and chl-a/colloidal carbohydrate (r = +0.85, p = 0.01). There was a significant relationship (r = +0.88, p = 0.005) between sediment erodability (mass of sediment eroded and erosion rate) and the density of the clam Macoma balthica, a major bioturbator of the surface sediments. Analysis of the data also demonstrated significant relationships between clearance rate and Cerastoderma edule biomass (r = +0.91, p < 0.001), and between sedment chl-a/colloidal carbohydrate and C. edule biomass (r = +0.92; p < 0.001), reflecting the influence of suspension feeders on both the water column and the sediment, through their biodeposits. The significant increase in sediment erodability between June and September reflected the shift in the overall balance between the major 'biostabilisers' (microphytobenthos) and 'bio-destabilisers' (bioturbating bivalves). Ths interpretation of field-derived correlations is consistent with previously established relationships and mechanistic understanding derived from controlled flume experiments.<br/
Effect of salinity and temperature on feeding physiology and scope for growth of an invasive species (Brachidontes pharaonis - MOLLUSCA: BIVALVIA) within the Mediterranean Sea
No full textThe Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent model for the study
of “Lessepsian migration” and the successive colonization at new Mediterranean locations. This species in out
competing indigenous bivalves is particularly well adapted to Mediterranean conditions and this is likely due to
biological characteristics and physio-ecological plasticity. In the present paper, we report on clearance rate
(CR), respiration rate (RR) and Scope for Growth (SFG) of B. pharaonis collected from a Western Sicilian pond
(Southern Tyrrhenian, MED). Physiological variables were determined in response to a range of temperatures
from 11 ° to 20 °C and a broad range of salinities from 15 to 60 psu. Salinity and temperature had a significant
influence on CR of B. pharaonis as therewas a general reduction in CR with a decline in temperature from 20 °C
to 11 °C and declining salinity from 37 to 15 psu. RR showed a general temperature dependent relationship with
highest RR at 20 °C. SFG showed negative values at lowest salinity of 15 psu at all tested temperatures. SFG
values were generally the highest at 45 psu (at 11 °C and 20 °C), although SFG showed a maximum at 37 psu at
15 °C. SFG values were positive over the broadest range of salinities (25 to 60 psu) at 20 °C. The plasticity of the
physiological rates demonstrated that B. pharaonis had the capacity to maintain positive SFG and tolerate a
wide range of temperature/salinity conditions. Possible implications of high physiological plasticity of B.
pharaonis in competing against indigenous bivalves are discussed
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Oh! Tonight the moonlight\u27s shining back home, [first line of chorus]
No full textPerformers: Genevieve HomerPiano and Voice (with lyrics
Relating spatial and temporal variability in sediment chlorophyll a and carbohydrate distribution with erodibility of a tidal flat
No full textTrends in the spatial distribution of chlorophyll a (chl a) and colloidal and total carbohydrates on the Molenplaat tidal flat in the Westerschelde estuary, Netherlands, reflected spatial differences in physical properties of the sediment. Results from a Spearman Rank Order Correlation indicated that many of the physical and biological measures covaried. Multiple regression analyses describing the relationship between colloidal carbohydrates and sediment properties resulted in several highly significant equations, although in all cases chl a was able to predict colloidal carbohydrate content. Relationships between sediment surface chl a and colloidal carbohydrate, and sediment erodibility (i.e., critical erosion threshold, Ucrit, and mass of sediment eroded at a velocity of 30 cm s-1) determined in annular flume experiments were examined. Overall sediment erodibility was lowest (i.e., high thresholds, low mass eroded) for the siltiest sediments in June 1996 when chl a and colloidal carbohydrates were high (56.9 mg gDW-1 and 320.6 mg gluc.equ. gDW-1, respectively), and greatest (i.e., low thresholds, high mass eroded) at the sandier sediments in September 1996, when chl a and colloidal carbohydrates were low (1.0 mg gDW-1 and 5.7 mg gluc.equ. gDW-1, respectively). When sediments were grouped according to relative silt content, the most significant relationships were found in muddy sand with a fine-grained fraction (<63 mm) of 25-50%. Thresholds of erosion increased, while mass of sediment eroded decreased, with increasing chl a and colloidal carbohydrate. A similar trend was observed for the sand-muddy sand (63 mm 10-25%). In the sand (63 mm 0-10%), there were no relationships for Ucrit, whereas mass eroded appeared to increase with increasing chl a and colloidal carbohydrate. The increased carbohydrate may stick sand grains together, altering the nature of erosion from rolling grains to clumps of resuspension
Murder on the mountain: author talk with Peter J. Wosh
No full textAuthor talk by Peter J. Wosh on May 5th, 2022, on his book, "Murder on the Mountain: crime, passion, and punishment in gilded age New Jersey.
Mr. Melvin J. Collier, RWWL AUC, June 2011
No full textThis video is a conversation with Mr. Melvin J. Collier. Mr. Collier talks about his book, "From Mississippi to Africa: A Journey of Discovery". Daniel Le, AUC Woodruff Library, is the interviewer
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