Duane C. Gossiaux

The assimilation of contaminants from suspended sediment and algae by the zebra mussel, Dreissena polymorpha

Since their invasion into the Great Lakes, zebra mussels, Dreissena polymorpha, have increased the water clarity in Lake St. Clair and Lake Erie due to their extensive particle filtration. Because these particles contain sorbed contaminants, the potential for contaminant accumulation from both suspended sediment and algae were examined. Sediment or algae were dosed with selected radiolabeled polycyclic aromatic hydrocarbon congeners and/or hexachlorobiphenyl (HCBP). Assimilation efficiencies were measured and depended on food quality. Zebra mussels, 17 +/- 2 mm long, assimilated 58.3 +/- 13.5% of the pyrene and 44.7 +/- 5.8% of the benzo(a)pyrene (BaP) from sediment particles with a particle clearance rate of 493-897 ml/g tissue/h. However, assimilation efficiencies were 91.7 +/- 3.7% for pyrene, 91.9 +/- 1.4% for BaP, 96.6 +/- 1.4% for chrysene, and 97.7 +/- 0.5% for HCBP from suspended algae. Algal particle clearance rates for the mussels ranged from 47-143 ml/g tissue/h. Thus, zebra mussels efficiently accumulated non-polar contaminants sorbed to algae, while a smaller fraction of the sediment-associated contaminant was bioavailable. Furthermore, the contaminants sorbed onto suspended sediment particles were quickly removed from the water and deposited as pseudofeces. The pseudofeces production was positively correlated with filtration rate and suspended particle concentrations.

Evaluation of the human health threat associated with the hepatotoxin microcystin in the muscle and liver tissues of yellow perch (Perca flavescens)

During the summer of 2006, the western basin of Lake Erie experienced a bloom of the toxigenic cyanobacte- rium Microcystis aeruginosa. Across 11 sites, intracellular, particulate-bound microcystin levels in the seston increased to levels that exceeded World Health Organization guidelines for drinking water exposure (1 mg toxinL -1 ). In contrast, toxin concentrations in yellow perch (Perca flavescens) muscle tissue (n = 68) declined from June to August, were negatively related to algal toxin levels, and never exceeded a conservative chronic exposure concentration estimated using proposed United States Environmental Protection Agency (US EPA) guidelines. Microcystin concentrations in yellow perch liver exceeded US EPA chronic exposure guidelines, were on average 125 times higher than muscle toxin concentrations per unit dry weight, and varied little throughout the summer. With current guidelines, humans do not appear to be at risk when consuming the muscle tissue of Lake Erie yellow perch collected during large-scale cyanobacterial blooms. How- ever, this study highlights the need for a better understanding of the trophic transfer of cyanobacterial toxins through aquatic food webs in diverse ecosystems with an emphasis on understanding if these compounds could accumulate suffi- ciently to affect human health.

The contrasting roles of sedimentary plant-derived carbon and black carbon on sediment-spiked hydrophobic organic contaminant bioavailability to Diporeia species and Lumbriculus variegatus.

In bioavailability studies, the biota sediment accumulation factor (BSAF) is invoked to describe the thermodynamic partitioning of a hydrophobic organic contaminant (HOC) between the organism lipid and the organic carbon fraction of the sedimentary matrix and accounts for differences in bioavailability among sediments. Bioaccumulation experiments were performed with Lumbriculus variegatus and Diporeia species exposed in seven sediments dosed with 2,4,5,2,4,5-hexachlorobiphenyl (HCBP) and benzo[a]pyrene (BaP) or pyrene (PY) and 3,4,3,4-tetrachlorobiphenyl (TCBP). The BSAF values for the nonplanar HCBP were consistent with equilibrium partitioning theory (EQP) and averaged 2.87 for L. variegatus and 1.45 for Diporeia, while the BSAF values for the planar compounds (BaP, PY, TCBP) were generally lower than estimated from EQP (<1). Correcting the BSAF values of the planar compounds for enhanced sorption due to black carbon improved the BSAF values for L. variegatus, generally resulting in values consistent with EQP, but substantial variation remained for Diporeia. The BSAF values for the planar compounds showed significant positive correlations with plant-derived carbon in sediments (lignin and pigments) but were more consistent for L. variegatus than for Diporeia. These correlations imply that compounds sorbed to plant-derived carbon are more bioavailable since this material is more likely ingested providing a second exposure route.

Time‐dependent lethal body residues for the toxicity of pentachlorobenzene to Hyalella azteca

The study examined the temporal response of Hyalella azteca to pentachlorobenzene (PCBZ) in water-only exposures. Toxicity was evaluated by calculating the body residue of PCBZ associated with survival. The concentration of PCBZ in the tissues of H. azteca associated with 50% mortality decreased from 3 to 0.5 micromol/g over the temporal range of 1 to 28 d, respectively. No significant difference was observed in the body residue calculated for 50% mortality when the value was determined using live or dead organisms. Metabolism of PCBZ was not responsible for the temporal response because no detectable PCBZ biotransformation occurred over an exposure period of 10 d. A damage assessment model was used to evaluate the impact and repair of damage by PCBZ on H. azteca. The toxicokinetics were determined so that the temporal toxicity data could be fit to a damage assessment model. The half-life calculated for the elimination of PCBZ averaged approximately 49 h, while the value determined for the half-life of damage repair from the damage assessment model was 33 h.

Comparative Efficacy of Potential Chemical Disinfectants for Treating Unballasted Vessels

The release of ballast water from transoceanic vessels is a major vector for the introduc- tion of nonindigenous species into the Laurentian Great Lakes. This study assessed the effectiveness of treating unballasted transoceanic vessels using three different biocides: glutaraldehyde plus a surfactant adjuvant (Disinfekt 1000 ®), sodium hypochlorite (NaOCl), and SeaKleen™ (menadione and menadione metabisulfite 2:8). Efficacy against several classes of aquatic organisms was evaluated using 24 h acute toxicity experiments and 11 day ballast tank simulation experiments. The results indicate substantial, compound-specific variations in organism sensitivity. For water-only exposures, NaOCl and SeaKleen™ were most effective: NaOCl had the lowest LC90 (90% lethal concentration value) for the oligochaete Lumbriculus variegatus (1.0 mg L-1), while SeaKleen™ had the lowest LC90 for the amphipod Hyalella azteca (2.5 mg L-1). Sediments profoundly affected efficacy, particularly for NaOCl: At a 1:4 sediment- water ratio, the estimated LC90 for L. variegatus was > 2,000 mg L-1. Sediment quality also impacted efficacy: Sediments with higher organic carbon content typically required greater biocide concentrations to achieve comparable toxicity. Efficacy was further evaluated with 11 day bioassays using sediments from unballasted vessels. Results indicated that NaOCl and Disinfekt 1000 ® were more effective than predicted based on small scale sediment-water exposures. Overall, the data suggest that although NaOCl may be effective under water-only conditions, the higher concentrations required in the presence of sedi- ments may cause corrosion problems for ballast tanks. Because of this, less reactive, non-oxidizing bio- cides such as SeaKleen™ and Disinfekt 1000 ® may be better candidates for treating sedimented tanks.

Effect of Temperature on the Accumulation Kinetics of PAHs and PCBs in the Zebra Mussel, Dreissena polymorpha☆

The role of temperature on the accumulation and elimination kinetics of selected poly-cyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyl (PCB) congeners was examined for the zebra mussel, Dreissena polymorpha. Uptake and elimination rates were measured at intervals over a three year period in laboratory toxicokinetics studies in which zebra mussels were maintained at ambient field temperatures or acclimated to higher or lower temperatures. The uptake rate coefficients (ku) for benzo(a)pyrene (BaP) and 2,2’,4,4’,5,5’-hexachlorobiphenyl (HCBP) increased in proportion to temperature over a range from 4 to 20C when measured at the field-collected temperature. Both ku and the elimination coefficient (kd) also decreased with increasing organism size. However, no relationship with temperature was found for the ku of BaP in the following year nor was there a relationship between ku and temperature for pyrene and pentachlorophenol (PCP) when the kinetics were measured at field-collected temperatures. In laboratory acclimation studies, ku for three compounds (BaP, HCBP, and PCP) showed a significant positive relationship with temperature over the 4–20C range. Pyrene accumulation kinetics however, still exhibited no relationship with temperature. These results contradict the concept that uptake of contaminants changes over a season with temperature thereby, influencing contaminant toxicokinetics. Furthermore, the kd values observed for these compounds indicate that elimination was slow, and no relationship of kd was exhibited with water temperature, season, or year.

Challenges for mapping cyanotoxin patterns from remote sensing of cyanobacteria

Using satellite imagery to quantify the spatial patterns of cyanobacterial toxins has several challenges. These challenges include the need for surrogate pigments - since cyanotoxins cannot be directly detected by remote sensing, the variability in the relationship between the pigments and cyanotoxins - especially microcystins (MC), and the lack of standardization of the various measurement methods. A dual-model strategy can provide an approach to address these challenges. One model uses either chlorophyll-a (Chl-a) or phycocyanin (PC) collected in situ as a surrogate to estimate the MC concentration. The other uses a remote sensing algorithm to estimate the concentration of the surrogate pigment. Where blooms are mixtures of cyanobacteria and eukaryotic algae, PC should be the preferred surrogate to Chl-a. Where cyanobacteria dominate, Chl-a is a better surrogate than PC for remote sensing. Phycocyanin is less sensitive to detection by optical remote sensing, it is less frequently measured, PC laboratory methods are still not standardized, and PC has greater intracellular variability. Either pigment should not be presumed to have a fixed relationship with MC for any water body. The MC-pigment relationship can be valid over weeks, but have considerable intra- and inter-annual variability due to changes in the amount of MC produced relative to cyanobacterial biomass. To detect pigments by satellite, three classes of algorithms (analytic, semi-analytic, and derivative) have been used. Analytical and semi-analytical algorithms are more sensitive but less robust than derivatives because they depend on accurate atmospheric correction; as a result derivatives are more commonly used. Derivatives can estimate Chl-a concentration, and research suggests they can detect and possibly quantify PC. Derivative algorithms, however, need to be standardized in order to evaluate the reproducibility of parameterizations between lakes. A strategy for producing useful estimates of microcystins from cyanobacterial biomass is described, provided cyanotoxin variability is addressed.

Time-dependent toxicity of dichlorodiphenyldichloroethylene to Hyalella azteca.

Temporal effects on body residues of dichlorodiphenyldichloroethylene (DDE) associated with mortality in the freshwater amphipod Hyalella azteca were evaluated. Toxicokinetics and body residues were determined from water-only exposures that varied from 4 to 28 d, and DDE concentrations ranging from 0.0013 to 0.045 micromol L(-1). Uptake and elimination parameters were not affected significantly by the various temporal and concentration treatments. Uptake rate coefficients ranged from 134.3 to 586.7 ml g(-1) h(-1), and elimination rate coefficients ranged from 0.0011 to 0.0249 h(-1). Toxicity metric values included body residue for 50% mortality at a fixed sample time (LR50) and mean lethal residue to produce 50% mortality from individual exposure concentrations (MLR50) for live organisms and dead organisms. A twofold increase occurred in the MLR50 values calculated using live organisms compared to MLR50 values using dead organisms. Toxicity and kinetic data were fit to a damage assessment model that allows for the time course for toxicokinetics and damage repair, demonstrating the time-dependence of body residues to toxicity. The DDE appeared to act through a nonpolar narcosis mode of action for both acute and chronic mortality in H. azteca. Furthermore, the temporal trend in the toxic response using body residue as the dose metric is steep and found to be similar to another chlorinated hydrocarbon, pentachlorobenzene, but was more potent than that found for polycyclic aromatic hydrocarbons (PAHs).

Cyanobacterial harmful algal blooms are a biological disturbance to western Lake Erie bacterial communities

Human activities are causing a global proliferation of cyanobacterial harmful algal blooms (CHABs), yet we have limited understanding of how these events affect freshwater bacterial communities. Using weekly data from western Lake Erie in 2014, we investigated how the cyanobacterial community varied over space and time, and whether the bloom affected non-cyanobacterial (nc-bacterial) diversity and composition. Cyanobacterial community composition fluctuated dynamically during the bloom, but was dominated by Microcystis and Synechococcus OTUs. The blooms progression revealed potential impacts to nc-bacterial diversity. Nc-bacterial evenness displayed linear, unimodal, or no response to algal pigment levels, depending on the taxonomic group. In addition, the bloom coincided with a large shift in nc-bacterial community composition. These shifts could be partitioned into components predicted by pH, chlorophyll a, temperature, and water mass movements. Actinobacteria OTUs showed particularly strong correlations to bloom dynamics. AcI-C OTUs became more abundant, while acI-A and acI-B OTUs declined during the bloom, providing evidence of niche partitioning at the sub-clade level. Thus, our observations in western Lake Erie support a link between CHABs and disturbances to bacterial community diversity and composition. Additionally, the short recovery of many taxa after the bloom indicates that bacterial communities may exhibit resilience to CHABs.

Sediment characteristics influencing the bioavailability of nonpolar organic contaminants to Diporeia spp.

ABSTRACTOrganic carbon is considered the major variable affecting the bioavailability of non-polar, sediment-associated contaminants. Previously, variation in bioavailability for some Great Lakes sediments compared to a soil material was nearly a factor of 10 after carbon normalization. Because a soil might not truly represent sedimentary materials, sediments and soils were gathered from several locations in the United States, Canada, and Finland. The accumulation kinetics of the amphipod Diporeia spp. were measured for pyrene, benzo[a]pyrene (BaP), 2,4,2′,4′- tetrachlorobiphenyl (TCBP), and 2,4,5,2′,4′,5′-hexachlorobiphenyl (HCBP) sorbed to sediments and soils. The organic carbon content of the sediments ranged from 0.45–21.2% and 32.2–45.0% for soils. The bioavailability, measured as the uptake clearance (amount of source compartment cleared of contaminant per mass of organism per hour), was controlled by the amount of organic carbon, particularly for the chlorinated biphenyls. However, for polycyclic a...