Environmental Correlates of Growth and Stable Isotopes in Intertidal Species Along an Estuarine Fjord

Production and resource use by intertidal taxa were studied in the estuarine fjord of Puget Sound, Washington, USA. Along nearly 100 km, salinity is similar, and intertidal habitat and immersion time were kept consistent, thus allowing a focus on other environmental variables such as temperature and resource availability that could influence growth. Primary producers (ulvoid and fucoid macroalgae) and suspension feeders (oysters and barnacles) were transplanted on three beaches in each of three regions and assessed for individual-level growth, carbon and nitrogen ratios, and stable isotopes. In most transplants, δ¹³C and C/N showed no regional variation but δ¹⁵N was enriched up-estuary. Among environmental variables, chlorophyll a, total suspended solids, and particulate organic matter had small and/or inconsistent regional variation, but temperature was higher up-estuary. For the most intensively studied species (Pacific oyster, Crassostrea gigas) transplanted four times over 2 years, seasonal and regional variation in growth were best predicted by temperature rather than resource availability. Growth rates continued to increase into Totten Inlet, a shallow finger inlet at the head of Puget Sound. As indicators of environmental conditions, the growth and tissue chemistry of intertidal study taxa affirm that sources and amounts of resources show no strong gradients along this estuarine fjord, and they also support temperature as a key factor for performance, with species-specific responses. Higher temperatures may also have community-level impacts, given prior evidence linking beach temperatures to reduced intertidal diversity and biomass into Puget Sound.     

Transport of Crustacean Larvae Between a Low-Inflow Estuary and Coastal Waters

The effectiveness of larval behavior in regulating transport between well-mixed, low-inflow estuaries and coastal waters in seasonally arid climates is poorly known. We determined the flux of an assemblage of benthic crustacean larvae relative to physical conditions between a shallow estuary and coastal waters on the upwelling coast of northern California (38°18′N, 123°03′W) from 29 to 31 March 2006. We detected larval behaviors that regulate transport in adjacent coastal waters and other estuaries for only two taxa in the low-inflow estuary, but they were apparent for taxa outside the estuary. Vertical mixing in the shallow estuary may have overwhelmed larvae of some species, or salinity fluctuations may have been too slight to cue tidal vertical migrations. Nevertheless, all larval stages of species that complete development in nearshore coastal waters were present in the estuary, because they remained low in the water column reducing seaward advection or they were readily exchanged between the estuary and open coast by tidal flows. Weak tidal flows and gravitational circulation at the head of the estuary reduced seaward transport during development for species that completed development nearshore, whereas larval release during nocturnal ebb tides enhanced seaward transport for species that develop offshore. Thus, nonselective tidal processes dominated larval transport for most species back and forth between the low-inflow estuary and open coastal waters, whereas in adjacent open coastal waters, larval behavior in the presence of wind-induced shear was more important in regulating migrations between adult and larval habitats along this upwelling coast.     

Trends in Abundance Indices of Fishes in Maryland’s Coastal Bays During 1972–2009

Maryland’s coastal bays provide habitat for juveniles of many commercially and recreationally important species of shellfish and finfish. Since 1972, the Maryland Department of Natural Resources has conducted the Maryland Coastal Bays Trawl and Seine Survey to monitor the populations of key species. The survey has undergone substantial spatial and methodological changes affecting the interpretation of simple indices of abundance. We developed generalized linear models to standardize the indices of abundance of five commonly caught fish species: Atlantic menhaden Brevoortia tyrannus, weakfish Cynoscion regalis, spot Leiostomus xanthurus, bay anchovy Anchoa mitchilli, and summer flounder Paralichthys dentatus. Density declined significantly since 1972 for menhaden, bay anchovy, and spot in at least one region within the coastal bays. The northern bays had significantly higher densities than the southern bays for all species. Changes in abundance indices of the five species examined were not related to sea grass coverage, temperature, salinity, nitrogen-to-phosphorus ratios, and other habitat variables but were likely a result of stock-wide recruitment processes.     

A portable extruder for accurate and precise high-resolution subsampling of unconsolidated sediment cores

Journal of Paleolimnology - We developed a portable extruder for precise and accurate high-resolution subsampling of unconsolidated sediment cores. This extruder is capable of producing subsamples...     

Distribution functions for energetic oxygen atoms in the earth's lower atmosphere

Direct photolysis of O₃ and quenching of $\text{O}\text{(}{}^1\text{D}\text{)}$ by N₂ provide abundant sources of fast oxygen atoms for the Earth's lower atmosphere. The concentration of atoms with energy above 0.7 eV may exceed the concentration of $\text{O}\text{(}{}^1\text{D}\text{)}$ for all altitudes below 18 km and these atoms may play an important role in lower atmospheric chemistry. Distribution functions for $\text{O}\text{(}{}^3\text{P}\text{)}$ are given for the energy interval 0.1-1.3 eV, for a range of altitudes from 0 to 62 km.     

Scattering properties of planetary regolith analogs

The physics of scattering of electromagnetic waves by media in which the particles are in contact, such as planetary regoliths, has been thought to be relatively well understood when the particles are larger than the wavelength. However, this is not true when the particles are comparable with or smaller than the wavelength. We have measured the scattering parameters of planetary regolith analogs consisting of suites of well-sorted abrasives whose particles ranged from larger to smaller than the wavelength. We measured the variation of reflectance as the phase angle varied from 0.05° to 140°. The following parameters of the media were then deduced: the single scattering albedo, single scattering phase function, transport mean free path, and scattering, absorption, and extinction coefficients. A scattering model based on the equation of radiative transfer was empirically able to describe quantitatively the variation of intensity with angle for each sample. Thus, such models can be used to characterize scattering from regoliths even when the particles are smaller than the wavelength. The scattering parameters were remarkably insensitive to particle size. These results are contrary to theoretical predictions, but are consistent with earlier measurements of alumina abrasives that were restricted to small phase angles. They imply that a basic assumption made by virtually all regolith scattering models, that the regolith particles are the fundamental scattering units of the medium, is incorrect. Our understanding of scattering by regoliths appears to be incomplete, even when the particles are larger than the wavelength.     

Feminism and Social Theory in Geography: An Introduction*

This essay introduces a collection of articles based on papers developed for a Fall 2004 speaker series at the University of Minnesota. The articles address the continued relevance of feminist geography and the unique contributions of feminist perspectives in various areas of geographic research. They also point out directions for needed future research. This introduction briefly reviews the successes of and remaining challenges to feminist geography, including material inequities yet unresolved in two other (nonresearch) “places” of academic life: teaching and the workplace. We discuss the ongoing underrepresentation of women and people of color on our faculties and in the front of classrooms.     

Towards a Better Understanding of Dynamic Interaction Metrics for Wildlife: a Null Model Approach

The ability to measure dynamic interactions, such as attraction or avoidance, is crucial to understanding socio‐spatial behaviors related to territoriality and mating as well as for exploring resource use and the potential spread of infectious epizootic diseases. In spite of the importance of measuring dynamic interactions, it has not been a main research focus in movement pattern analysis. With very few exceptions (see Benhamou et al. 2014), no new metrics have been developed in the past 20 years to accommodate the fundamental shift in the type of animal movement data now being collected and there have been few comparison or otherwise critical studies of existing dynamic interaction metrics (but see Long et al. 2014; Miller 2012). This research borrows from the null model approach commonly used in community ecology to compare six currently used dynamic interaction metrics using data on five brown hyena dyads in Northern Botswana. There was disconcerting variation among the dynamic interaction results depending on which metric and which null model was used, and these results highlight the need for more extensive research on measuring and interpreting dynamic interactions in order to avoid making potentially misleading inferences about socio‐spatial behaviors.