Sam C. Wainright

The Role of Tidal Salt Marsh as an Energy Source for Marine Transient and Resident Finfishes: A Stable Isotope Approach

Abstract Stable isotope ratios of carbon, nitrogen, and sulfur (δ13C, δ15N, and δ34S) in bay anchovy Anchoa mitchilli and white perch Morone americana from Delaware Bay were a function of capture location and, for restored tidal salt marshes, possibly a function of the relative position of the marsh restoration trajectory. White perch collected in polyhaline restoration and reference (Moores Beach) sites had stable isotope signatures that reflected contributions from both benthic microalgae and Spartina alterniflora. Isotope values from white perch captured at the reference site were slightly enriched compared with those captured at the restoration sites. At upper estuary oligo–mesohaline locations, Phragmites australis contributed to the isotopic composition of both species. Although P. australis was not dominant at the reference marsh (Mad Horse Creek), it also seemed to influence the flow of nutrients into these species. White perch were not collected in open waters of Delaware Bay, but bay anchovy we...

Assimilation of carbon and nitrogen from pollen and nectar by a predaceous larva and its effects on growth and development

Abstract.  1. Predaceous insects may benefit from feeding on non‐prey foods, such as pollen, nectar, and honeydew, because they can provide nutrients that help maintain metabolism and enhance overall nutrient intake. Yet, the extent to which predaceous insects can assimilate non‐prey food and the importance of diet mixing during particular life history stages is poorly understood. In this study the relative contribution of an omnivorous diet to the growth and survivorship of a predaceous larva was tested in a hypothetical situation in which nutritionally optimal prey was not available. The study system comprised a predaceous larva (second‐ and third‐instar larvae of the green lacewing Chrysoperla carnea), nutritionally poor prey (larvae of Drosophila melanogaster), and non‐prey food (pollen suspension, a mixture of bee pollen and artificial nectar (1 M sucrose solution)). Chrysoperla carnea larvae in the mixed diet treatment were provided with both Drosophila larvae and pollen suspension, while those reared on the prey and non‐prey diet treatments received only Drosophila larvae or pollen suspension respectively.

13C/12C composition of marine dissolved organic carbon

Abstract The stable isotopic composition of marine dissolved organic carbon (DOC) was measured with a high temperature, sealed tube combustion technique. The δ 13 C values of DOC ( DO 13 C ) were approximately −22‰ for all samples that were collected (1) in a monthly survey conducted in Woods Hole Harbor, (2) in a spatial survey across Georges Bank during a spring bloom period, and (3) in depth profiles near Bermuda, Georges Bank and in the eastern Equatorial Pacific. The DO 13 C values were uniform in waters of varying DOC content, including low DOC deep waters and high DOC surface waters, indicating little overall isotopic fractionation during formation and degradation of marine DOC. The −22‰ DO 13 C values are similar to those observed for average marine particulate and sedimentary organic material, and exclude a large contribution from −27‰ terrestrial DOC to ocean pools.

Evaluation of ENDECO 1184C dissolved oxygen recorders for use in temperate estuaries

Abstract Pulsed Clarke-type electrodes, a relatively new type of dissolved oxygen (DO) sensor, were intended to minimize problems associated with sensitivity to flow and biofouling-problems which affect most oxygen sensors. The commercially available devices (ENDECO/YSI, Inc., Model 1184C), which include temperature and conductivity sensors and a data logger, are designed for coastal environmental monitoring at depths to 30 m. In order to evaluate their performance under field conditions, a series of field deployments and laboratory calibrations was conducted, and the instrument output was compared with precision Winkler titrations. Accuracy of reported DO concentrations varied both between instruments and with time. Errors typically ranged from 0 to 3 mg/l. Thus frequent calibration seems to be a requirement for the accurate use of these units. The recommended 1-point calibration update did not improve accuracy. In the laboratory, the response to varying DO concentrations at constant temperature was highly linear over a range of approx. 5–14 mg/l; both accuracy and response time decreased at low DO concentrations, somewhere between 0 and 1.5 mg/l. Potential sources of inaccuracy in DO measurements include (1) statistical error associated with the estimation of calibration constants, and (2) operation of the instrument near the extremes of the temperature range used to calibrate it. We found support for the claim that the instruments are relatively insensitive to fouling.