Evidence of hypoxic foraging forays by yellow perch ( Perca flavescens ) and potential consequences for prey consumption

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/1/FWB_2753_sm_fS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/91146/2/j.1365-2427.2012.02753.x.pd

Effects of Hypoxia on Consumption, Growth, and RNA:DNA Ratios of Young Yellow Perch

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end, we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic growth, and RNA : DNA ratios (an index of short‐term growth) of young yellow perch and (2) explored the effects of bottom hypoxia on young yellow perch growth in Lake Erie’s central basin by collecting individuals in hypoxicand normoxic regions of the lake and quantifying their RNA : DNA ratios. Yellow perch consumption and growth in our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA : DNA ratios responded strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding ration. We did, however, observe a positive correlation between yellow perch growth and RNA : DNA ratios at low temperatures (11°C). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA : DNA ratios. Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA : DNA ratios of yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141858/1/tafs1574.pd

A trophic bottleneck?: The ecological role of trout‐perch P ercopsis omiscomaycus in S aginaw B ay, L ake H uron

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97230/1/jai12023.pd

Improving QPF by blending techniques at the Meteorological Service of Catalonia

The current operational very short-term and short-term quantitative precipitation forecast (QPF) at the Meteorological Service of Catalonia (SMC) is made by three different methodologies: Advection of the radar reflectivity field (ADV), Identification, tracking and forecasting of convective structures (CST) and numerical weather prediction (NWP) models using observational data assimilation (radar, satellite, etc.). These precipitation forecasts have different characteristics, lead time and spatial resolutions. The objective of this study is to combine these methods in order to obtain a single and optimized QPF at each lead time. This combination (blending) of the radar forecast (ADV and CST) and precipitation forecast from NWP model is carried out by means of different methodologies according to the prediction horizon. Firstly, in order to take advantage of the rainfall location and intensity from radar observations, a phase correction technique is applied to the NWP output to derive an additional corrected forecast (MCO). To select the best precipitation estimation in the first and second hour (t+1 h and t+2 h), the information from radar advection (ADV) and the corrected outputs from the model (MCO) are mixed by using different weights, which vary dynamically, according to indexes that quantify the quality of these predictions. This procedure has the ability to integrate the skill of rainfall location and patterns that are given by the advection of radar reflectivity field with the capacity of generating new precipitation areas from the NWP models. From the third hour (t+3 h), as radar-based forecasting has generally low skills, only the quantitative precipitation forecast from model is used. This blending of different sources of prediction is verified for different types of episodes (convective, moderately convective and stratiform) to obtain a robust methodology for implementing it in an operational and dynamic wa

Polyethylene imine-based receptor immobilization for label free bioassays

Polyethylene imine (PEI) based immobilization of antibodies is described and the concept is proved on the label free assay of C-Reactive Protein (CRP). This novel immobilization method is composed of a hyperbranched PEI layer which was deposited at a high pH (9.5) on the sensor surface. The free amino groups of PEI were derivatized with neutravidin by Biotin N-hydroxysuccinimide ester and the biotinylated anti-CRP antibody immobilized on this layer. Direct binding assay of recombinant CRP was successfully performed in the low μg/ml concentrations using a label free optical waveguide biosensor

Indirect consequences of hypolimnetic hypoxia on zooplankton growth in a large eutrophic lake

Diel vertical migration (DVM) of some zooplankters in eutrophic lakes is often compressed during peak hypoxia. To better understand the indirect consequences of seasonal hypolimnetic hypoxia, we integrated laboratory-based experimental and field-based observational approaches to quantify how compressed DVM can affect growth of a cladoceran, Daphnia mendotae, in central Lake Erie, North America. To evaluate hypoxia tolerance of D. mendotae, we conducted a survivorship experiment with varying dissolved oxygen concentrations, which demonstrated high sensitivity of D. mendotae to hypoxia (≤2 mg O2 l−1), supporting the field observations of their behavioral avoidance of the hypoxic hypolimnion. To investigate the effect of temporary changes in habitat conditions associated with the compressed DVM, we quantified the growth of D. mendotae, using a 3 (food quantity) × 2 (temperature) factorial design laboratory experiment. Neither food quantity nor temperature affected short-term growth in body length of D. mendotae. However, D. mendotae RNA content (an index of short-term condition) decreased under starvation, indicating an immediate response of short-term feeding on condition. We further evaluated the effect of hypoxia-induced upward shifts in vertical distribution by quantifying the RNA content of D. mendotae from central Lake Erie before and during peak hypoxia. Despite high temperature and food quantity in the upper water column, RNA content in field-collected D. mendotae remained low during peak hypoxia. Furthermore, D. mendotae collected during peak hypoxia consisted of only small-bodied

Assessing the energy implications of replacing car trips with bicycle trips in Sheffield, UK

A wide range of evidence supports policies which encourage people to cycle more and drive less, for health and environmental reasons. However, the likely energy implications of such a modal shift have remained relatively unexplored. In this paper we generate scenarios for increasing the cycling rate in Sheffield between 2010 and 2020. This is done through the novel application of a simple model, borrowed from population ecology. The analysis suggests that pro-cycling interventions result in energy savings through reduced consumption of fuel and cars, and energy costs through increased demand for food. The cumulative impact is a net reduction in primary energy consumption, the magnitude of which depends on a number of variables which are subject to uncertainty. Based on the evidence presented and analysed in this paper, we conclude that transport policy has a number of important energy implications, some of which remain unexplored. We therefore advocate the formation of closer links between energy policy and transport policy in academia and in practice; our approach provides a simple yet flexible framework for pursuing this aim in the context of modal shift

Maturation Schedules of Walleye Populations in the Great Lakes Region: Comparison of Maturation Indices and Evaluation of Samplingâ Induced Biases

Maturation schedules, key determinants of fish stocks’ harvest potential and population dynamics, are influenced by both plastic and adaptive processes. Various indices are used to describe maturation schedules, and these have differential advantages for discriminating between plastic and adaptive processes. However, potential samplingâ related biases associated with different maturation indices have not been fully evaluated. We analyzed three maturation indices for walleyes Sander vitreus in Lake Erie; Saginaw Bay, Lake Huron; and Oneida Lake, New York: age and length at 50% maturity, midpoint of ageâ specific maturity ogives (ageâ specific length at which probability of maturity = 0.50), and midpoints of probabilistic maturation reaction norms (PMRNs; ageâ specific length at which probability of maturing in the following year = 0.50). We then compared estimated maturation indices to evaluate sensitivity of different maturation indices to samplingâ induced biases and to assess the relative importance of plastic versus adaptive processes in structuring interstock and temporal variation in maturation schedules. Our findings suggest that although small changes in sampling month, gear, and agencyâ related effects can bias estimates of age and length at 50% maturity and midpoints of maturity ogives, PMRN estimates appear to be robust to these biases. Furthermore, PMRN estimates are suggestive of potential adaptive variation in maturation schedules among walleye stocks and over time. For instance, Oneida Lake walleyes (which had relatively slow growth and low mortality rates) matured at a smaller size for a given age (smaller midpoints of PMRNs) than the other stocks. Temporally, walleyes in the western basin of Lake Erie matured at a larger size in recent years, as evidenced by increasing midpoints of PMRNs (1978â 1989 versus 1990â 2006 for Ohio Department of Natural Resources data and 1990â 1996 versus 1997â 2006 for Ontario Ministry of Natural Resources data). Our study highlights the necessity of monitoring maturation schedules via multiple maturation indices and the need to account for samplingâ induced biases when comparing maturation schedules.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141201/1/nafm1540.pd