Anne Kuhn

Population genetic diversity and fitness in multiple environments

BackgroundWhen a large number of alleles are lost from a population, increases in individual homozygosity may reduce individual fitness through inbreeding depression. Modest losses of allelic diversity may also negatively impact long-term population viability by reducing the capacity of populations to adapt to altered environments. However, it is not clear how much genetic diversity within populations may be lost before populations are put at significant risk. Development of tools to evaluate this relationship would be a valuable contribution to conservation biology. To address these issues, we have created an experimental system that uses laboratory populations of an estuarine crustacean, Americamysis bahia with experimentally manipulated levels of genetic diversity. We created replicate cultures with five distinct levels of genetic diversity and monitored them for 16 weeks in both permissive (ambient seawater) and stressful conditions (diluted seawater). The relationship between molecular genetic diversity at presumptive neutral loci and population vulnerability was assessed by AFLP analysis.ResultsPopulations with very low genetic diversity demonstrated reduced fitness relative to high diversity populations even under permissive conditions. Population performance decreased in the stressful environment for all levels of genetic diversity relative to performance in the permissive environment. Twenty percent of the lowest diversity populations went extinct before the end of the study in permissive conditions, whereas 73% of the low diversity lines went extinct in the stressful environment. All high genetic diversity populations persisted for the duration of the study, although population sizes and reproduction were reduced under stressful environmental conditions. Levels of fitness varied more among replicate low diversity populations than among replicate populations with high genetic diversity. There was a significant correlation between AFLP diversity and population fitness overall; however, AFLP markers performed poorly at detecting modest but consequential losses of genetic diversity. High diversity lines in the stressful environment showed some evidence of relative improvement as the experiment progressed while the low diversity lines did not.ConclusionsThe combined effects of reduced average fitness and increased variability contributed to increased extinction rates for very low diversity populations. More modest losses of genetic diversity resulted in measurable decreases in population fitness; AFLP markers did not always detect these losses. However when AFLP markers indicated lost genetic diversity, these losses were associated with reduced population fitness.

An overview of toxicant identification in sediments and dredged materials

The identification of toxicants affecting aquatic benthic systems is critical to sound assessment and management of our nations waterways. Identification of toxicants can be useful in designing effective sediment remediation plans and reasonable options for sediment disposal. Knowledge of which contaminants affect benthic systems allows managers to link pollution to specific dischargers and prevent further release of toxicant(s). In addition, identification of major causes of toxicity in sediments may guide programs such as those developing environmental sediment guidelines and registering pesticides, while knowledge of the causes of toxicity which drive ecological changes such as shifts in benthic community structure would be useful in performing ecological risk assessments. To this end, the US Environmental Protection Agency has developed tools (toxicity identification and evaluation (TIE) methods) that allow investigators to characterize and identify chemicals causing acute toxicity in sediments and dredged materials. To date, most sediment TIEs have been performed on interstitial waters. Preliminary evidence from the use of interstitial water TIEs reveals certain patterns in causes of sediment toxicity. First, among all sediments tested, there is no one predominant cause of toxicity; metals, organics, and ammonia play approximately equal roles in causing toxicity. Second, within a single sediment there are multiple causes of toxicity detected; not just one chemical class is active. Third, the role of ammonia is very prominent in these interstitial waters. Finally, if sediments are divided into marine or freshwater, TIEs perforMed on interstitial waters from freshwater sediments indicate a variety of toxicants in fairly equal proportions, while TIEs performed on interstitial waters from marine sediments have identified only ammonia and organics as toxicants, with metals playing a minor role. Preliminary evidence from whole sediment TIEs indicates that organic compounds play a major role in the toxicity of marine sediments, with almost no evidence for either metal or ammonia toxicity. However, interpretation of these results may be skewed because only a small number of interstitial water (n = 13) and whole sediment (n = 5) TIEs have been completed. These trends may change as more data are collected.

Removal of ammonia toxicity in marine sediment TIEs: a comparison of Ulva lactuca, zeolite and aeration methods

Toxicity Identification Evaluations (TIEs) can be used to determine the specific toxicant(s), including ammonia, causing toxicity observed in marine sediments. Two primary TIE manipulations are available for characterizing and identifying ammonia in marine sediments: Ulva lactuca addition and zeolite addition. In this study, we compared the efficacy of these methods to (1) remove NH(x) and NH(3) from overlying and interstitial waters and (2) reduce toxicity to the amphipod Ampelisca abdita and mysid Americamysis bahia using both spiked and environmentally contaminated sediments. The utility of aeration for removing NH(x) and NH(3) during a marine sediment TIE was also evaluated preliminarily. In general, the U. lactuca and zeolite addition methods performed similarly well at removing spiked NH(x) and NH(3) from overlying and interstitial waters compared to an unmanipulated sediment. Toxicity to the amphipod was reduced approximately the same by both methods. However, toxicity to the mysid was most effectively reduced by the U. lactuca addition indicating this method functions best with epibenthic species exposed to ammonia in the water column. Aeration removed NH(x) and NH(3) from seawater when the pH was adjusted to 10; however, very little ammonia was removed at ambient pHs ( approximately 8.0). This comparison demonstrates both U. lactuca and zeolite addition methods are effective TIE tools for reducing the concentrations and toxicity of ammonia in whole sediment toxicity tests.

pH dependent toxicity of five metals to three marine organisms

The pH of natural marine systems is relatively stable; this may explain why metal toxicity changes with pH have not been well documented. However, changes in metal toxicity with pH in marine waters are of concern in toxicity testing. During porewater toxicity testing pH can change 1–2 units as porewater is transferred from in situ to a test container. These changes in pH may alter metal toxicity. Also, deliberately altering the sample pH is an important toxicity identification and evaluations (TIE) manipulation designed to detect changes in ammonia toxicity. If altering pH also changes metal toxicity, this may confound interpretation of TIE manipulation results. This study demonstrates that alteration of pH can also change the toxicity of Cu, Cd, Ni, Pb, and Zn to Mysidopsis bahia (mysid), Ampelisca abdita (amphipod) and Vibrio fischerii [Microtox solid phase test (MSP)]. Changes in toxicity with respect to pH were metal and organism specific with the following trends. For the MSP assay, as pH decreased there was a decrease in toxicity for Pb, Ni, Cd, and Zn and an increase in toxicity for Cu. For mysids, as pH decreased, there was a decrease in toxicity for Pb and an increase in toxicity for Cu and Ni. For amphipods, Cu was the only metal that showed decreased toxicity with decreasing pH; the toxicity of all other metals for amphipods remained constant. Results of this study indicate changes in metal toxicity with respect to pH must be considered for porewater testing and TIE interpretation. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 235–240, 1999

Toxicity characterization of an industrial and a municipal effluent discharging to the marine environment

Toxicity Identification Evaluation (TIE) methods have proven very useful in characterizing, identifying and confirming toxicants in environmental samples. This report describes the characterization of toxicants present in two effluents, industrial and municipal, discharged into the marine environment. A toxicity characterization consists of dividing an effluent sample into several relatively unique chemical fractions. Manipulations used to generate these fractions include aeration, filtration, chelation, oxidant reduction, reverse phase chromatography, and graduated pH adjustments. Marine toxicity tests used include mysids (Mysidopsis bahia), fish (Menidia beryllina and Cyprinodon variegatus), macroalga (Champia parvula) and sea urchins (Arbacia punctulata). Results of this TIE demonstrated that both effluents contained toxicity predominantly due to metals and organic contaminants. Ammonia toxicity in the municipal effluent was sample dependent. This study illustrates that the use of marine toxicity tests, TIE procedures and historical data can be combined to better understand the nature of toxicity discharged to the marine environment.

Population Growth and Demography of Common Loons in the Northern United States

Abstract We used recent developments in theoretical population ecology to construct basic models of common loon (Gavia immer) demography and population dynamics. We parameterized these models using existing survival estimates and data from long-term monitoring of loon productivity and abundance. Our models include deterministic, 2-stage, density-independent matrix models, yielding population growth-rate estimates (λ) of 0.99 and 1.01 for intensively studied populations in our Wisconsin, USA, and New Hampshire, USA, study areas, respectively. Perturbation analysis of these models indicated that estimated growth rate is extremely sensitive to adult survival, as expected for this long-lived species. Also, we examined 20 years of count data for the 2 areas and evaluated support for a set of count-based models of population growth. We detected no temporal trend in Wisconsin, which would be consistent with fluctuation around an average equilibrium state but could also result from data limitations. For New Hampshire, the model set included varying formulations of density dependence and partitioning of stochasticity that were enabled by the annual sampling resolution. The best model for New Hampshire included density regulation of population growth and, along with the demographic analyses for both areas, provided insight into the possible importance of breeding habitat availability and the abundance of nonbreeding adults. Based on these results, we recommend that conservation organizations include nonbreeder abundance in common loon monitoring efforts and that additional emphasis be placed on identifying and managing human influences on adult loon survival.

Modeling Habitat Associations for the Common Loon ( Gavia immer ) at Multiple Scales in Northeastern North America

Common Loon (Gavia immer) is considered an emblematic and ecologically important example of aquatic-dependent wildlife in North America. The northern breeding range of Common Loon has contracted over the last century as a result of habitat degradation from human disturbance and lakeshore development. We focused on the state of New Hampshire, USA, where a long-term monitoring program conducted by the Loon Preservation Committee has been collecting biological data on Common Loon since 1976. The Common Loon population in New Hampshire is distributed throughout the state across a wide range of lake-specific habitats, water quality conditions, and levels of human disturbance. We used a multiscale approach to evaluate the association of Common Loon and breeding habitat within three natural physiographic ecoregions of New Hampshire. These multiple scales reflect Common Loon-specific extents such as territories, home ranges, and lake-landscape influences. We developed ecoregional multiscale models and compared them to single-scale models to evaluate model performance in distinguishing Common Loon breeding habitat. Based on information-theoretic criteria, there is empirical support for both multiscale and single-scale models across all three ecoregions, warranting a model-averaging approach. Our results suggest that the Common Loon responds to both ecological and anthropogenic factors at multiple scales when selecting breeding sites. These multiscale models can be used to identify and prioritize the conservation of preferred nesting habitat for Common Loon populations. RESUME. Le Plongeon huard (Gavia immer) est considere comme un representant emblematique et ecologiquement important de la faune dependante du milieu aquatique en Amerique du Nord. L’aire de reproduction du Plongeon huard a subi une contraction depuis le siecle passe en raison de la degradation de son habitat consecutive au derangement humain et a l’augmentation de l’occupation humaine sur les bords de lacs. Nous avons choisi le cas du New Hampshire, E.-U., car il y existe un programme de suivi a long terme effectue par le Loon Preservation Committee, qui collige les donnees biologiques sur l’espece depuis 1976. La population du Plongeon huard est repartie partout dans cet Etat, selon une grande variete de milieux lacustres, de conditions de qualite d’eau et de degres de derangement humain. Nous avons utilise une approche multi-echelles afin d’evaluer la relation entre le Plongeon huard et son habitat de nidification, dans trois ecoregions physiographiques naturelles au New Hampshire. Ces differentes echelles refletent d’autres caracteristiques relatives au Plongeon huard, comme les territoires, les domaines vitaux et les influences lac-paysage. Nous avons elabore des modeles multi-echelles ecoregionaux et les avons compares a des modeles tenant compte d’une seule echelle pour evaluer leur performance a distinguer correctement l’habitat de nidification du Plongeon huard. D’apres les criteres de la theorie de l’information, les observations empiriques soutiennent les modeles multi-echelles tout comme les modeles a une seule echelle, dans les trois ecoregions, resultat qui justifie une approche fondee sur la moyenne des modeles. Nos resultats U.S. Environmental Protection Agency, Atlantic Ecology Division, SRA International Inc., The Loon Preservation Committee, BioDiversity Research Institute, University of Rhode Island Department of Natural Resources Coastal Institute in Kingston Avian Conservation and Ecology 6(1): 4 http://www.ace-eco.org/vol6/iss1/art4/ laissent croire qu’au moment de selectionner son site de nidification, le Plongeon huard reagit tout autant aux facteurs ecologiques qu’aux facteurs anthropiques, a differentes echelles. Il est possible d’utiliser ces modeles multi-echelles pour determiner l’habitat de nidification de predilection des populations de Plongeon huard et pour en prioriser la conservation.

Stable isotopes of algae and macroinvertebrates in streams respond to watershed urbanization, inform management goals, and indicate food web relationships

Watershed development and anthropogenic sources of nitrogen are among leading causes of negative impacts to aquatic ecosystems around the world. The δ15N of aquatic biota can be used as indicators of anthropogenic sources of nitrogen enriched in 15N, but this mostly has been done at small spatial extents or to document effects of point sources. In this study, we sampled 77 sites along a forest to urban land cover gradient to examine food webs and the use of δ15N of periphyton and macroinvertebrate functional feeding groups (FFGs) as indicators of watershed development and nitrogen effects on streams. Functional feeding groups had low δ15N variability among taxa within sites. Mean absolute differences between individual taxa and their respective site FFG means were < 0.55‰, whereas site means of δ15N of FFGs had ranges of approximately 7-12‰ among sites. The δ15N of periphyton and macroinvertebrate FFGs distinguished least disturbed streams from those with greater watershed urbanization, and they were strongly correlated with increasing nitrogen concentrations and watershed impervious cover. Nonmetric multidimensional scaling, using δ15N of taxa, showed that changes in macroinvertebrate assemblages as a whole were associated with forest-to-urban and increasing nitrogen gradients. Assuming an average +3.4‰ per trophic level increase, δ15N of biota indicated that detrital pathways likely were important to food web structure, even in streams with highly developed watersheds. We used periphyton and macroinvertebrate FFG δ15N to identify possible management goals that can inform decisions affecting nutrients and watershed land use. Overall, the δ15N of periphyton and macroinvertebrates were strong indicators of watershed urban development effects on stream ecosystems, and thus, also could make them useful for quantifying the effectiveness of nitrogen, stream, and watershed management efforts.

Performance of National Maps of Watershed Integrity at Watershed Scales

Watershed integrity, the capacity of a watershed to support and maintain ecological processes essential to the sustainability of services provided to society, can be influenced by a range of landscape and in-stream factors. Ecological response data from four intensively monitored case study watersheds exhibiting a range of environmental conditions and landscape characteristics across the United States were used to evaluate the performance of a national level Index of Watershed Integrity (IWI) at regional and local watershed scales. Using Pearson’s correlation coefficient (r), and Spearman’s rank correlation coefficient (rs), response variables displayed highly significant relationships and were significantly correlated with IWI and ICI (Index of Catchment Integrity) values at all watersheds. Nitrogen concentration and flux-related watershed response metrics exhibited significantly strong negative correlations across case study watersheds, with absolute correlations (|r|) ranging from 0.48 to 0.97 for IWI values, and 0.31 to 0.96 for ICI values. Nitrogen-stable isotope ratios measured in chironomids and periphyton from streams and benthic organic matter from lake sediments also demonstrated strong negative correlations with IWI values, with |r| ranging from 0.47 to 0.92, and 0.35 to 0.89 for correlations with ICI values. This evaluation of the performance of national watershed and catchment integrity metrics and their strong relationship with site level responses provides weight-of-evidence support for their use in state, local and regionally focused applications.

Use of Marine Toxicity Identification and Evaluation Methods in Determining Causes of Toxicity to Fish in a Marine Aquarium Facility

Abstract We obtained a water sample containing broken pieces of a tropical coral reef decor that was suspected of causing fish toxicity in a major aquarium. A toxicity identification and evaluation (TIE) was performed using three species: a mysid shrimp, Americamysis bahia; inland silverside Menidia beryllina; and an amphipod, Ampelisca abdita. Initial tests indicated that only the shrimp was sensitive to the unknown toxicant. The first phase of the TIE indicated that the toxicity to the shrimp could be eliminated by either the addition of EDTA or manipulation of the cation exchange column. Elevated concentrations of Cd were detected by inductively coupled plasma analysis, and metal toxicity was confirmed when the cation exchange column treatment successfully isolated the toxic metal. Analysis of affected fish tissue indicated Cd levels ranging from less than 0.3 ng/g in the muscle to 200 μg/g in the liver. This study demonstrates a unique application of TIE methods to diagnose toxicity problems in aquari...