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Twine Line Winter/Spring 2018

OHSU-TL-1555

Twine Line Winter/Spring 2018. Twine Line gets ready for summer. Learn how travel benefits our state and the ways that research at Stone Lab is improving the quality of our drinking water, plus lots more in this issue of Twine Line.

VOLUME: 40 ISSUE: 1 LENGTH: 19 pages
Twine Line

2017 HABs Lake Erie HABs Forecast System (Kavanaugh)

EXT-1541

Slideshow explaining NOAA’s Harmful Algal Bloom Forecast System.

External Partner Publication

Great Lakes Sea Grant Network Education and Outreach on Asian Carp Report

OHSU-TB-1511

Report explaining the dangers, history, and status of Asian Carp in the Great Lakes, and it provides materials and contact info for those seeking more information or to educate others on Asian Carp.

LENGTH: 55 pages
Technical Bulletin

The Cuyahoga River Area of Concern

OHSU-FS-1505

The Cuyahoga River isn’t at risk of catching fire anymore, but that doesn’t mean it’s in great shape either. The Cuyahoga River is a designated Area of Concern. This fact sheet explains what that means, and what’s being done to fix it.

LENGTH: 1 page
Fact Sheet

De Novo Transcriptome Sequencing and Analysis of Male, Pseudo-male and Female Yellow Perch, Perca flavescens

OHSU-RS-1571
ABSTRACT:

Transcriptome sequencing could facilitate discovery of sex-biased genes, biological pathways and molecular markers, which could help clarify the molecular mechanism of sex determination and sexual dimorphism, and assist with selective breeding in aquaculture. Yellow perch has unique gonad system and sexual dimorphism and is an alternative model to study mechanism of sex determination, sexual dimorphism and sexual selection. In this study, we performed the de novo assembly of yellow perch gonads and muscle transcriptomes by high throughput Illumina sequencing. A total of 212,180 contigs were obtained, ranging from 127 to 64,876 bp, and N50 of 1,066 bp. The assembly RNA-Seq contigs (≥200bp) were then used for subsequent analyses, including annotation, pathway analysis, and microsatellites discovery. No female- and pseudo-male-biased genes were involved in any pathways while male-biased genes were involved in 29 pathways, and neuroactive ligand receptor interaction and enzyme of trypsin (enzyme code, EC: 3.4.21.4) was highly involved. Pyruvate kinase (enzyme code, EC: 2.7.1.40), which plays important roles in cell proliferation, was highly expressed in muscles. In addition, a total of 183,939 SNPs, 11,286 InDels and 41,479 microsatellites were identified. This study is the first report on transcriptome information in Percids, and provides rich resources for conducting further studies on understanding the molecular basis of sex determinations, sexual dimorphism, and sexual selection in fish, and for population studies and marker-assisted selection in Percids.

DOI: 10.1371/journal.pone.0171187 VOLUME: 12 ISSUE: 2
Reprint

Feeding Glycyrrhiza glabra (liquorice) and Astragalus membranaceus (AM) Alters Innate Immune and Physiological Responses in Yellow Perch (Perca flavescens)

OHSU-RS-1570
ABSTRACT:

The current work assessed the potential immunomodulatory and growth-promoting effects of Astragalus membranaceus (AM) and Glycyrrhiza glabra (liquorice) in Yellow perch (Perca flavescens). In this regard, fish with an average weight of 31 ± 1.0 g were divided into five groups, and fed daily with an additive-free basal diet (control); 1, 2, and 3% (w/w) Glycyrrhiza glabra, and the fifth diet was incorporated with a combination of 1% G. glabra-AM for a four-week period. Immunological, biochemical and growth parameters were measured; and sub-groups of fish were exposed to 1-week starvation. The results showed that incorporating AM and liquorice in the diet significantly improved Immunological [superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), Lipid peroxidase (LPx) and lysozyme activities], biochemical [Aspartate Aminotransferase (AST) and Alanine Transaminase (ALT) activities; and glucose and cortisol concentrations] and growth performance parameters [body mass gain (BMG), specific growth rate (SGR), length, condition factor (K) and feed conversion ratio (FCR)]. In addition, markedly up-regulated the expression of related genes [Insulin-Like Growth Factor-1 (IGF-1), Serum amyloid A (SAA), Complement Component C3 (CCC3), Alpha 2 Macroglobulin (A2M), SOD and GPx] in treated fish groups compared to the control. Conclusively, feeding AM and liquorice diets significantly increased (P < 0.05) growth performance, antioxidant and immune response profiles throughout the entire experiment, suggesting their beneficial rule as natural anti-stress agents.

DOI: 10.1016/j.fsi.2016.04.024 VOLUME: 54 LENGTH: 10 pages
Reprint

Characterization of The Persistent Cyanobacterial Bloom, Planktothrix in Sandusky Bay, Lake Erie

OHSU-TD-1512
ABSTRACT:

Planktothrix sp. is less studied than other bloom-forming cyanobacteria. The aim of this study was to determine characteristics of the Planktothrix bloom in Sandusky Bay. Using the 2013 Sandusky Bay metagenome and 2014 summer samples, it was found that the bloom in Sandusky Bay has limited diversity and is continuously dominated by Planktothrix. Nutrient profiles of the Bay suggest nitrogen limitation throughout the bloom season. Physical parameters recorded in Sandusky Bay are suboptimal for many known bloom-forming cyanobacteria. Given this information, it is not yet understood how Planktothrix survives and dominates Sandusky Bay. Future work will look further at community members playing a role in the nitrogen cycle in the Bay. Additionally, the succession of genotypes will be determined over time as the environmental parameters will be monitored over a longer period of time to determine how survival of Planktothrix is supported.

Thesis / Dissertation

Microcystin Concentrations in Lake Erie Walleye and Implications for Public Health

OHSU-TD-1511
ABSTRACT: Cyanobacterial harmful algal blooms (HABs) degrade water quality of western Lake Erie and create negative economic impacts on an annual basis. Public health is at the forefront of concern because these blooms are often toxic due to an abundance of Microcystis. This genus of cyanobacteria produces the toxin microcystin, which causes gastrointestinal illnesses, damages the liver, and is capable of promoting tumors or death of animals (Poste et al 2011). The World Health Organization (WHO) has set values for microcystin in drinking water, recreational contact, and total daily consumption, but no standards exist for concentrations of microcystin in food. Because microcystin can accumulate in fish tissues, and fishing and fish consumption are important economic and cultural practices in Lake Erie, there is a potential health risk to humans via consumption of fish inhabiting waters with high concentrations of microcystin. Walleye is one of the most significant sportfish of Lake Erie, and a previous study found this species can have greater microcystin concentrations than yellow perch and white perch studied in the same time period (Wituszynski 2014). For these reasons, this study quantified microcystin levels in walleye tissue using an enzyme-linked immunosorbent assay (ELISA) and compared to public health thresholds used by the Ohio Department of Natural Resources (ODNR). Samples were harvested at different times and from locations in attempt to understand the seasonal correlation between bloom intensity and microcystin concentration, and impacts of variations in bloom intensity at different locations. The effects of chronic exposure of fish to microcystin has not been widely studied for Lake Erie, and no studies presently exist which have examined year-to-year variation in microcystin content in fish. Thus, by comparing this study to a similar study conducted in 2013 (Wituszynski 2014), we can aid in identifying correlation between annual variation in HABS, determine if previous exposure has an effect on accumulation in fish, and understand when microcystin concentrations in fish tissues may be at its peak when compared to HAB intensity.
LENGTH: 21 pages
Thesis / Dissertation

Summer phytoplankton nutrient limitation in Maumee Bay of Lake Erie during high-flow and low-flow years

OHSU-RS-1503

Manuscript comparing Maumee Bay phytoplankton growth from 2010-2012

ABSTRACT:

Algal production inMaumee Bay in western Lake Erie is highly affected by inputs of nitrogen (N) and phosphorus (P) from the Maumee River, which drains predominantly agricultural lands, leading to the formation of cyanobacterial blooms. In a 3-year study, precipitation and discharge ranged from relatively low (2012) to relatively high (2011) with corresponding changes in the size of the cyanobacterial bloom. This study aimed to quantify the relation between river discharge and algal nutrient limitation in Maumee Bay. During the summer growing seasons, 20 nutrient enrichment bioassays were performed to determine which nutrient (P or N) might limit phytoplankton growth; and ambient N and P concentrations were monitored. The bioassays suggested that phytoplankton growth shifted from P-limited to N-limited during summer of the low and intermediate discharge years (2012 and 2010, respectively), whereas during the high discharge year (2011) phytoplankton were nutrient-replete before becoming N-limited. Phosphorus-replete growth during the high discharge year likely was due to high P loads from the river and dissolved P concentrations greater than 1 μmol/L. Symptoms of N-limited growth occurred during August and September in all three years and during July of 2012 when NO3 − plus NH4 + concentration was less than 7.29 μmol/L suggesting lowor no correspondence between N-limitation and size of the cyanobacterial bloom. Occurrence of a relatively small cyanobacterial bloom in 2012 following the record-breaking bloom in 2011 suggests the possibility of fast-reversal of eutrophication in Maumee Bay if P loading from the watershed could be decreased.

DOI: 10.1016/j.jglr.2014.04.009 VOLUME: 40 ISSUE: 3 LENGTH: 7 pages
Reprint

Oxygen use by Nitrification in the Hypolimnion and Sediments of Lake Erie

OHSU-RS-1540
ABSTRACT:

Nitrification is an oxygen consumptive process, consuming 2 mol of oxygen permol of ammonium oxidized. Hypolimnion
and sediment sampleswere collected during the summers of 2008–2010 in Lake Erie to determine the
total oxygen consumption and oxygen consumption fromnitrification by blocking nitrification with selective inhibitors.
Oxygen consumption by nitrification in the hypolimnion was 3.7 ± 2.9 (mean ± 1 SD) μmol O2/L/d,
with nitrification accounting for 32.6 ± 22.1% of the total oxygen consumption. Nitrification in the hypolimnion
contributed more to oxygen consumption in the eastern sites than western sites and was lowest in September.
The nitrification rate did not correlatewith environmental factors such as oxygen, nitrate or ammonium, or nitrifier
numbers. Oxygen consumption by nitrification in sediment slurries was 7.1 ± 5.8 μmol O2/g/d, with nitrification
accounting for 27.0 ± 19.2% of the total oxygen consumption with the lowest rates in July and the lowest
percentages in June. Oxygen consumption by nitrification in intact sediment coreswas 682 ± 61.1 μmol O2/m/d
with nitrification accounting for 30.4 ± 10.7% of the total oxygen consumption. Nitrification rates in intact cores
were generally highest in September. The proportion of oxygen consumed by nitrification corresponds closely
with what would be predicted from complete oxidation of a Redfield molecule (23%).While nitrification is unlikely
to be the dominant oxygen consumptive process, the rates observed in Lake Eriewere sufficient to theoretically
deplete a large portion of the hypolimnetic oxygen pool during the stratified period.

VOLUME: 40 ISSUE: 1 LENGTH: 5 pages
Reprint

Organic and inorganic nitrogen utilization by nitrogen-stressed cyanobacteria during bloom conditions

OHSU-RS-1502

Manuscript on nitrogen utilization by cyanobacteria

ABSTRACT:

Cyanobacterial blooms often occur in lakes that have high phosphorus (P) and low nitrogen (N) concentrations, and the growth rate of the blooms is often constrained by N. For these reasons, many researchers have suggested that regulation of both P and N is required to control eutrophication. However, because N occurs in many bioavailable forms, regulation of a particular form may be beneficial rather than regulation of all N forms. To address how N-stressed cyanobacteria respond to various N inputs, N enrichment experiments (nitrate, ammonium, urea, and alanine) were performed during N-limited cyanobacterial blooms in Maumee and Sandusky Bays of Lake Erie and in Grand Lake St. Marys (GLSM). Bioavailable N (nitrate, urea, and ammonium) concentrationswere also determined. Microcystis aeruginosa dominated the Maumee Bay bloom, where the highest growth rates were in response to ammonium additions, and lowest growth rates were in response to nitrate. Urea and the amino acid alanine resulted in intermediate growth rates. Planktothrix agardhii dominated the Sandusky Bay and GLSM blooms, where nitrate, ammonium, and urea addition resulted in similar growth rates. Additions of alanine did not stimulate growth of the Planktothrix blooms. Incubations using stable isotope 15N showed the cyanobacteria had a preference for ammonium, but the other forms were also assimilated in the presence of ammonium. These results show that cyanobacterial blooms will assimilate multiple forms of N to support growth. Thus, if lake managers do decide that N abatement is necessary, then all forms of bioavailable N need to be constrained.

DOI: 10.1007/s10811-013-0118-0 VOLUME: 26 ISSUE: 1 LENGTH: 10 pages
Reprint

Length-Weight Relationships of the Mimic Shiner Notropis volucellua (Cope 1865) in the Western Basin of Lake Erie

OHSU-RS-1551
ABSTRACT:

Gender relationships between total and standard length (mm) were compared to weight (mg) in the mimic shiner,
Notropis volucellus for the western Lake Erie basin in the vicinity of the Bass Islands. Length and weight relationship (n=300),
length-frequency distribution, and sex ratios (n=884) from a single date from Gibraltar Island in June 2012 were analyzed for
coastal shoreline and tributaries. A strong positive correlation was found between length and weight for both males and females.
In females, a significant positive correlation exists between standard length (SL) and body weight (F=671.5, d.f.=135) and between
total length (TL) and body weight (F=681.4, d.f.=135). In males, there was also a strong positive correlation between SL and body
weight (F=1744.9, d.f.=160) and between TL and body weight (F=1656.6, d.f.=160). Combining data for the two sexes helped
determine a strong relationship between SL and body weight (F=1908.3, d.f.=299) and between TL and body weight (F=1885.9,
d.f.=299) that was consistent with the results from the individual sexes. The growth patterns of male and female mimic shiner
differed significantly for both SL (F=0.76, p>0.05, d.f.=159-134) and TL (F=0.76, p>0.05, d.f.=159-134). Age I females ranged
from 29–51 mm TL and Age I males ranged from 30–46 mm TL based on 884 individuals from Gibraltar Island. Age II females
ranged from 57–61 mm TL and Age II males ranged from 54–56 mm TL. Mimic shiner exhibit indeterminate growth and gender
influences growth patterns.

VOLUME: 112 ISSUE: 2 LENGTH: 6 pages
Reprint

DNA Barcoding to Confirm Morphological Traits and Determine Relative Abundance of Burrowing Mayfly Species in Western Lake Erie

OHSU-RS-1538
ABSTRACT:

Burrowing mayfly species of the genus Hexagenia are well known indicators of environmental health in lakes and rivers. Two species, H. limbata and H. rigida, are indistinguishable as nymphs and as adult females. Our objectives were to develop a genetic technique to distinguish between the two species and identify morphological features that separate cryptic nymphs and adult females. Fifty nymphs were collected before emergence from 10 sites throughout the western basin of Lake Erie in 2004 and 2005. Using known specimens of adult aerial male H. limbata and H. rigida, we used the mitochondrial cytochrome c oxidase subunit 1 (COI) gene to identify a 16 base pair (bp) difference between species. DNA sequencing confirmed correct species identification based on differences in abdominal pigmentation patterns on adult female imagos in 19 of 20 cases; the lone exception was a female with very faint pigmentation. Pigmentation patterns between species were consistent on nymphs, subimagos and imagos of both sexes. Populations of both species are panmictic across the western basin of Lake Erie, but H. limbata is the numerically dominant species, representing 70 to 100% of nymphs at sites in both years. A separate lineage of H limbata was discovered in the samples. The ability to distinguish nymphs of the two species will aid in developing more sensitive ecosystem indicators.

DOI: 10.1016/j.jglr.2011.11.010 VOLUME: 38 ISSUE: 1 LENGTH: 6 pages
Reprint

Expansion of Tubenose Gobies Proterorhinus semilunaris into Western Lake Erie and Potential Effects on Native Species

OHSU-RS-1539
ABSTRACT:

The Eurasian freshwater tubenose goby Proterorhinus semilunaris (formerly Proterorhinus marmoratus) invaded the Laurentian Great Lakes in the 1990s, presumably via ballast water from transoceanic cargo ships. Tubenose gobies spread throughout Lake St. Clair, its tributaries, and the Detroit River system, and also are present in the Duluth-Superior harbor of Lake Superior. Using seines and bottom trawls, we collected 113 tubenose gobies between July 2007 and August 2009 at several locations in western Lake Erie. The number and range of sizes of specimens collected suggest that that tubenose gobies have become established and self-sustaining in the western basin of Lake Erie. Tubenose gobies reached maximum densities in sheltered areas with abundant macrophyte growth, which also is their common habitat in native northern Black Sea populations. The diet of tubenose gobies was almost exclusively invertebrates, suggesting dietary overlap with other benthic fishes, such as darters (Etheostoma spp. and Percina sp.), madtoms (Noturus spp.), and sculpins (Cottus spp.). A single mitochondrial DNA haplotype was identified, which is the most common haplotype found in the original colonization area in the Lake St. Clair region, suggesting a founder effect. Tubenose gobies, like round gobies Neogobius melanostomus, have early life stages that drift owing to vertical migration, which probably allowed them to spread from areas of colonization. The Lake St. Clair-Lake Erie corridor appears to have served as an avenue for them to spread to the western basin of Lake Erie, and abundance of shallow macrophyte-rich habitats may be a key factor facilitating their further expansion within Lake Erie and the remainder of the Laurentian Great Lakes.

DOI: 10.1007/s10530-011-9962-5 VOLUME: 13 ISSUE: 12 LENGTH: 9 pages
Reprint

The Effects of Dreissenid Mussels on the Survival and Condition of Burrowing Mayflies (Hexagenia spp.) in Western Lake Erie

OHSU-RS-1542
ABSTRACT:

Burrowing mayflies (Hexagenia limbata and H. rigida) are once again prominent members of the benthic community in western Lake Erie. However, this community is now dominated by dreissenid mussels. We conducted a laboratory experiment and field sampling to investigate whether survival and condition of Hexagenia were affected by the presence, density, and quality of dreissenid mussels. In a laboratory experiment, Hexagenia survival was higher in microcosms without dreissenid mussels. We also found Hexagenia density to be higher at field sites with low dreissenid density, suggesting that Hexagenia survival is higher in these areas as well. In microcosm treatments with low dreissenid density, Hexagenia survival was higher in treatments with live dreissenids than in treatments containing only dreissenid shells. These findings suggest that while dreissenid shells degrade the quality of soft sediments for Hexagenia, some of the negative effect is offset by the presence of live dreissenids. The positive effect of live dreissenids is likely due to additional food resources made available to Hexagenia by the filtering activity of dreissenids. Neither dreissenid density nor shell “type” (shells alone or live dreissenids in shells) had an effect on Hexagenia condition. Thus, the interactions between these dominant benthic invertebrates are complex. Recovery of Hexagenia populations in western Lake Erie is likely affected by both changing environmental conditions due to anthropogenic activities and the introduction of exotic species into the benthic community. The results are likely to be continued instability of the benthic food web and unpredictable consequences for human utilization of this ecosystem.

DOI: doi:10.1016/j.jglr.2011.04.006 VOLUME: 37 ISSUE: 3 LENGTH: 5 pages
Reprint

Identifying Relationships between Catches of Spawning Condition Yellow Perch and Environmental Variables in the Western Basin of Lake Erie

OHSU-RS-1543
ABSTRACT:

Although the reproductive behavior of yellow perch Perca
flavescens has been well documented in small systems, relatively
little is known about the spawning preferences of yellow perch in
large systems, such as the Laurentian Great Lakes. During 2006
and 2007, we compared the presence and abundance adult yellow
perch during the spring spawning season with environmental
variables in the western basin of Lake Erie. We also estimated the
timing of yellow perch spawning by comparing the relative abundance
of gravid and spent females collected in our trawls and then
comparing the proportion of gravid females with environmental
conditions at our sampling sites. Overall, the probability of catching
adult yellow perch and the catch per unit effort increased with
increasing bottom temperatures in the spring, whereas the probability
of catching gravid females increased with increasing Secchi
depth. However, the relationships between our catch metrics and
environmental variables were not consistent across years, possibly
as a result of the very strong 2003 year-class, which became
first-year spawners in 2006.We also documented that yellow perch
spawning occurred when bottom temperatures were between 11◦C
and 15◦C in the western basin; these temperatures were reached
on different dates in different parts of the basin and in different years. Thus, we suggest that management agencies consider basing
the start of the commercial fishing season on prevailing bottom
temperatures rather than using a set date across years and sites.

DOI: 10.1080/00028487.2011.545018 VOLUME: 140 ISSUE: 1 LENGTH: 5 pages
Reprint

Summer and Winter Spatial Habitat Use by the Lake Erie Watersnake

OHSU-RS-1544
ABSTRACT:

In an effort to provide information to guide habitat management for the Lake Erie watersnake Nerodia sipedon
insularum, a federally threatened and Ohio state endangered species, we used radiotelemetry to obtain spatial habitat
data for adult snakes during the summer active season and during winter hibernation. During the summer active
season, terrestrial habitat use was limited to a narrow band of shoreline. Among individuals, maximum distance inland
from shore ranged from 1 to 50 m (mean = 8 m) and linear extent of shoreline ranged from 30 to 1,360 m (mean =
261 m). Winter hibernation occurred at varying distances inland with individual hibernation sites ranging from 1 to
580 m (mean = 29 m) from shore. Habitat use did not differ between males and females. Existing U.S. Fish and Wildlife
Service habitat management guidelines suggest that ground-disturbing activities within potential hibernation areas
(defined as terrestrial habitat within 161 m of shore) should be avoided in winter to prevent harm to hibernating
snakes. They suggest further that excavation and removal of shrubs, standing or downed trees, root masses, animal
burrows, piled rocks, cliffs, or bedrock within 21 m of shore should be avoided in summer to prevent harm to active
snakes. Given that Lake Erie watersnakes have recovered to the point where delisting is being proposed, these habitat
guidelines appear to be sufficient. However, maintaining voluntary compliance with habitat guidelines and meeting
the need for continued public outreach will be vital to ensure long-term persistence.

DOI: 10.3996/052010-JFWM-013 VOLUME: 1 ISSUE: 2 LENGTH: 8 pages
Reprint

Oxyradical scavenging capacity by the S9 fraction of Hexagenia Spp. Nymphs From the Western Basin of Lake Erie: Neutralisation of Three Potent Oxidants

OHSU-RS-1545
ABSTRACT:

Oxidative stress is a general response of aquatic organisms to environmental contamination. Metals and organic compounds capable of redox cycling cause proliferation of reactive oxygen species (ROS) within organisms. Harm results from ROS-mediated DNA damage, lipid peroxidation, enzyme degradation and compromised intermediary metabolism. Variations in concentrations or activities of antioxidants have been proposed as biomarkers of toxicant-mediated oxidative stress in aquatic organisms. The total oxyradical scavenging capacity (TOSC) assay provides an index of biological resistance to ROS. Burrowing mayflies (Hexagenia spp.) are key indicator species of the health of numerous water bodies, including Lake Erie. TOSC has been used to evaluate the ROS scavenging capacity of tissues from a number of marine and freshwater invertebrates. This is the first study to evaluate ROS scavenging capacity in Hexagenia nymphs. Hexagenia nymphal tissue was homogenised in TRIS buffer containing a protease inhibitor cocktail and then differentially centrifuged to obtain a 9000 g supernatant (S9). The specific TOSC values (±SD, n=3) per μg protein are 2.08±0.43 for peroxyl radicals, 3.06±0.19 for hydroxyl radicals and 0.36±0.02 for peroxynitrite (n=3 to 4 determinations). These values for peroxyl radical scavenging capacity were equivalent to 11.9% and 77.0% that of Trolox (a water soluble analogue of vitamin E) and reduced glutathione TOSC equivalents, respectively, on a per μg basis. These results show that Hexagenia nymphal S9 is capable of neutralising peroxyl radicals and hydroxyl radicals effectively, but neutralises peroxynitrite considerably more weakly. The efficacy of this parameter as a biomarker of exposure to or effect of environmental contaminants will require controlled exposure analysis.

DOI: 10.1080/02757541003643495 VOLUME: 26 ISSUE: 2 LENGTH: 9 pages
Reprint

Viral Hemorrhagic Septicemia Virus Infection in Yellow Perch, Perca Flavescens, in Lake Erie

OHSU-RS-1549
ABSTRACT:

Viral hemorrhagic septicemia virus (VHSV) infects wild and hatchery fish in Europe, Japan, and the Great Lakes and Pacific regions of North America. The virus was associated with a large die-off of yellow perch, Perca flavescens, in Lake Erie in 2006. To determine the infection pattern of VHSV, we sampled yellow perch during the spring, summer, and fall of 2007 and 2008 in the central basin of Lake Erie during routine sampling by the Ohio Division of Wildlife with bottom trawls in nearshore, mid-depth, and offshore locations near the Chagrin River. The Ohio Department of Agriculture’s Diagnostic Laboratories and the U.S. Fish and Wildlife Service’s La Crosse Fish Health Center tested for VHSV from homogenized samples obtained from yellow perch kidney, spleen, and brain. At each lake sample location, we also measured temperature, dissolved oxygen, and conductivity. In both years, we found yellow perch infected with VHSV during a three-week period starting in the last week of spawning to early June. A high proportion of adult male and female yellow perch tested positive for VHSV during the infection period in our sample population. Infection appeared to be associated with temperatures between 12 and 18 °C and with significantly higher yellow perch densities during spawning. No large mortalities of yellow perch were observed during the VHSV infection period in 2007 and 2008.

DOI: 10.1016/j.jglr.2009.11.004 VOLUME: 36 ISSUE: 1 LENGTH: 6 pages
Reprint

Transient Social–Ecological Stability: the Effects of Invasive Species and Ecosystem Restoration on Nutrient Management Compromise in Lake Erie

OHSU-RS-1546
ABSTRACT:

Together, lake ecosystems and local human activity form complex social–ecological systems (SESs) characterized by feedback loops and discontinuous change. Researchers in diverse fields have suggested that complex systems do not have single stable equilibria in the long term because of inevitable perturbation. During this study, we sought to address the general question of whether or not stable social–ecological equilibria exist in highly stressed and managed lacustrine systems. Using an integrated human–biophysical model, we investigated the impacts of a species invasion and ecosystem restoration on SES equilibrium, defined here as a compromise in phosphorus management among opposing stakeholders, in western Lake Erie. Our integrated model is composed of a calibrated ecological submodel representing Sandusky Bay, and a phosphorus management submodel that reflects the societal benefits and costs of phosphorus regulation. These two submodels together form a dynamic feedback loop that includes freshwater ecology, ecosystem services, and phosphorus management. We found that the invasion of dreissenid mussels decreased ecosystem resistance to eutrophication, necessitating increased phosphorus management to preserve ecosystem services and thus creating the potential for a shift in social–ecological equilibrium. Additionally, our results suggest that net benefits in the region following the invasion of dreissenids may never again reach the pre-invasion level if on-site phosphorus control is the sole management lever. Further demonstrating transient system stability, large-scale wetland restoration shifted points of management compromise to states characterized by less on-site phosphorus management and higher environmental quality, resulting in a significant increase in net benefits in the region. We conclude that lacustrine SESs are open and dynamic, and we recommend that future models of these systems emphasize site-specific perturbation over equilibrium, thereby aiding the development of management plans for building system resistance to undesirable change that are both flexible and sustainable in an unknowable future.

VOLUME: 15 ISSUE: 1 LENGTH: 28 pages
Reprint

Return and Increase in Abundance of Aquatic Flowering Plants in Put-In-Bay Harbor, Lake Erie, Ohio

OHSU-RS-1547
VOLUME: 95 ISSUE: 3 LENGTH: 5 pages
Reprint
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