Parotid gland metastasis in Merkel cell carcinoma of the head and neck: A series of 14 cases

Merkel cell carcinoma (MCC) is a rare cutaneous cancer of neuroendocrine cell origin that occurs frequently on the head and neck. With a high incidence of local recurrence and regional and distant metastasis, it carries a poor prognosis. We performed a retrospective study to determine the prognostic implications of parotid gland metastasis in MCC of the head and neck. Our study population was made up of 14 patients—13 men and 1 woman, aged 62 to 87 years (mean: 75.9)—who underwent a parotidectomy for the diagnosis of MCC over a period of 10 years and 9 months. Ten patients had a primary skin lesion of the head and neck and 4 presented with a parotid mass and an unknown primary. In all, 13 of the 14 patients were found to have parotid involvement—either a direct extension of MCC into the gland or a positive intraparotid lymph node; some patients had both. All patients underwent tumor excision, and 10 underwent neck dissection. Eleven patients received adjuvant radiotherapy; none received adjuvant chemotherapy. Of the 10 patients who underwent a neck dissection, 6 were found to have a cervical lymph node metastasis on pathologic examination. Follow-up ranged from 1.3 to 39.2 months (mean: 12.4). Three patients were lost to follow-up shortly after surgery, although some information was available on 2 of them. At the final follow-up, mortality data were available on 12 patients; of these, 11 had died. The lone survivor was the patient without a parotid metastasis. Among those known to have died, survival ranged from 1.6 to 49.2 months (mean: 16.0). We conclude that parotid metastasis in patients with MCC of the head and neck is associated with a dismal survival rate that is even worse than the poor survival associated with cervical node involvement.

Utility of the Surgical Apgar Score in Head and Neck Squamous Cell Carcinoma

Objectives To recognize the utility of the surgical Apgar score (SAS) in a noncutaneous head and neck squamous cell carcinoma (HNSCC) population. Study Design Retrospective case series with chart review. Setting Academic tertiary medical center. Subjects and Methods Patients (n = 563) undergoing noncutaneous HNSCC resection between April 2012 and March 2015 were included. Demographics, medical history, intraoperative data, and postoperative hospital summaries were collected. SASs were calculated following the published schema. The primary outcome was 30-day postoperative morbidity. A 2-sample t test, analysis of variance, and χ² (or Fisher exact) test were used for statistical comparisons. A multivariable logistic regression analysis was conducted to identify independent predictors of 30-day morbidity. Results Mean SAS was 6.2 ± 1.5. SAS groups did not differ in age, sex, or race. Sixty-five patients (11.6%) had a SAS between 0 and 4, with 40 incidences of morbidity (61.5%), while 31 (5.5%) patients with SAS from 9 to 10 had 3 morbidity occurrences (9.7%). Results show that 30-day postoperative morbidity is inversely related to increasing SAS ( P < .0001). Furthermore, lower SAS was associated with significantly increased operative time (SAS 0-4: 9.3 ± 2.6 hours vs SAS 9-10: 3.0 ± 1.1 hours) and lengths of stay (SAS 0-4: 10.0 ± 7.3 days vs SAS 9-10: 1.6 ± 1.0 days), P < .0001. SAS remained highly significant after adjusting for potential confounding variables in the multivariable analysis ( P < .0001). Conclusions An increasing SAS is associated with significantly lower rates of 30-day postoperative morbidities in a noncutaneous HNSCC patient population.

Utility of the Modified Surgical Apgar Score in a Head and Neck Cancer Population

Objective The Surgical Apgar Score (SAS) is a validated postoperative complication prediction model. The purpose of this study was to investigate the utility of the SAS in a diverse head and neck cancer population and to compare it with a recently developed modified SAS (mSAS) that accounts for intraoperative transfusion. Study Design Case series with chart review. Setting Academic tertiary care medical center. Subjects and Methods This study comprised 713 patients undergoing surgery for head and neck cancer from April 2012 to March 2015. SAS values were calculated according to intraoperative data obtained from anesthesia records. The mSAS was computed by assigning an estimated blood loss score of zero for patients receiving intraoperative transfusions. Primary outcome was 30-day postoperative morbidity. Results Mean SAS and mSAS were 6.3 ± 1.5 and 6.2 ± 1.7, respectively. SAS and mSAS were significantly associated with 30-day postoperative morbidity, length of stay, operative time, American Society of Anesthesiologists status, race, and body mass index ( P < .05); however, no significant association was detected for age, sex, and smoking status. Multivariable analysis identified SAS and mSAS as independent predictors of postoperative morbidity, with the mSAS ( P = .03) being a more robust predictor than the SAS ( P = .15). Strong inverse relationships were demonstrated for the SAS and mSAS with length of stay and operative time ( P < .0001). Conclusion The SAS serves as a useful metric for risk stratification of patients with head and neck cancer. With the inclusion of intraoperative transfusion, the mSAS demonstrates superior utility in predicting those at risk for postoperative complications.

Parotid gland metastasis in Merkel cell carcinoma of the head and neck: A series of 14 cases

Merkel cell carcinoma (MCC) is a rare cutaneous cancer of neuroendocrine cell origin that occurs frequently on the head and neck. With a high incidence of local recurrence and regional and distant metastasis, it carries a poor prognosis. We performed a retrospective study to determine the prognostic implications of parotid gland metastasis in MCC of the head and neck. Our study population was made up of 14 patients-13 men and 1 woman, aged 62 to 87 years (mean: 75.9)-who underwent a parotidectomy for the diagnosis of MCC over a period of 10 years and 9 months. Ten patients had a primary skin lesion of the head and neck and 4 presented with a parotid mass and an unknown primary. In all, 13 of the 14 patients were found to have parotid involvement-either a direct extension of MCC into the gland or a positive intraparotid lymph node; some patients had both. All patients underwent tumor excision, and 10 underwent neck dissection. Eleven patients received adjuvant radiotherapy; none received adjuvant chemotherapy. Of the 10 patients who underwent a neck dissection, 6 were found to have a cervical lymph node metastasis on pathologic examination. Follow-up ranged from 1.3 to 39.2 months (mean: 12.4). Three patients were lost to follow-up shortly after surgery, although some information was available on 2 of them. At the final follow-up, mortality data were available on 12 patients; of these, 11 had died. The lone survivor was the patient without a parotid metastasis. Among those known to have died, survival ranged from 1.6 to 49.2 months (mean: 16.0). We conclude that parotid metastasis in patients with MCC of the head and neck is associated with a dismal survival rate that is even worse than the poor survival associated with cervical node involvement.

Time-dependent pretreatment with bevacuzimab increases tumor specific uptake of cetuximab in preclinical oral cavity cancer studies

Inadequate delivery of therapeutics into tumors has been suggested as a reason for poor response. We hypothesize that bevacizumab, an antibody to vascular endothelial growth factor (VEGF), can improve cetuximab uptake in squamous cell carcinoma tumors. Athymic nude mice were implanted with OSC19 and SCC1 human cancer lines in a subcutaneous flank model. Mice were imaged daily for 14 days after intravenous tail vein injections of the following groups: IgG-IRDye800 (Control), cetuximab-IRDye800 (CTX800 Only), bevacizumab-IRDye800 (BVZ800 Only), cetuximab-IRDye800 + bevacuzimuab-IRDye800 (Simultaneous), and unlabeled bevacizumab followed by cetuximab-IRDye800 3 days later (Neoadjuvant). Within single-agent groups, the CTX800 Only tumor-specific uptake (TSU) was significantly higher than BVZ800 Only at Day 13 (TSU 8.6 vs 2.8, P < 0.001). The Simultaneous treatment with BVZ800 and CTX800 demonstrated no increase in antibody delivery. However, administration of unlabeled bevacizumab 3 days prior to CTX800 (Neoadjuvant group) resulted in significantly higher tumor specific delivery than administration of both antibodies at the same time (11.8 vs Simultaneous 5.0, P < 0.001). This difference can be attributed to a slower decline in tumor fluorescence intensity (-6.8% vs. Simultaneous -11.5% per day, respectively). Structural changes in pericyte coverage and functional vessel changes demonstrating decreased proliferation and tumor growth corroborate these fluorescence results. Although simultaneous administration of bevacizumab with cetuximab failed to increase antibody delivery to the tumor, pretreatment with bevacizumab improved TSU reflecting an increase in tumor-specific uptake of cetuximab as a result of vessel normalization.

Pathology quiz case: Plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy that possesses a heterogenous clinical and immunophenotypic presentation. The current case report describes an interesting and unique presentation of BPDCN as a primary paranasal sinus tumor without evidence of cutaneous or systemic involvement. As such, the report further contributes to the ongoing debate regarding the true putative origin of the neoplasm, as well as highlights the optimal diagnostic modalities, paramount importance of early diagnosis, and vast heterogeneity exhibited by this fascinating malignancy. The atypical presentation described here indicates the manifestations of BPDCN are more heterogenous than previously documented and thus can not be definitively ruled out in the absence of bone marrow, peripheral blood, or cutaneous involvement. Furthermore, atypical neoplastic presentations mandate flow cytometry and adjunctive immunohistochemistry for the definitive diagnosis of BPDCN, and early diagnosis of such neoplasms are critical for rapid initiation of treatment and improved outcomes.

Predictors of clinical outcome after tracheotomy in critically ill obese patients

OBJECTIVES/HYPOTHESIS

To identify patient factors associated with outcomes in critically ill obese patients requiring tracheotomy.

STUDY DESIGN

Single-institution, retrospective cohort study.

METHODS

Charts were reviewed for inpatients admitted to an intensive care unit from 2007 to 2010 with International Classification of Diseases, 9th Revision codes of obesity or morbid obesity and tracheotomy. Variables collected in the dataset include subject age, ethnicity, gender, body mass index, tracheotomy type, patient outcome, chief diagnosis, and medical comorbid conditions. The primary outcomes of interest were tracheotomy type and patient outcome at the time of hospital discharge. Logistic regression models were developed for the probability of each patient outcome using univariate and multivariate models.

RESULTS

One hundred two patients met inclusion criteria. The most common outcome was tracheostomy dependence (49%). Increased mortality was independently significantly associated with pulmonary hypertension (P = .019) and African American ethnicity (P = .045). Increased tracheostomy dependence was significantly associated with obstructive sleep apnea (P = .030). Increased decannulation was significantly associated with percutaneous tracheotomy (P = .016) and Caucasian ethnicity (P < .001).

CONCLUSIONS

Obese patients in the intensive care unit who undergo tracheotomy have a high likelihood of remaining tracheostomy dependent at the time of discharge from the hospital. The factors most commonly found to be significantly associated with poor outcomes were open tracheotomy, African American ethnicity, obstructive sleep apnea, and pulmonary hypertension.

Hardware removal after osseous free flap reconstruction

OBJECTIVE

Identifying risk factors for hardware removal in patients undergoing mandibular reconstruction with vascularized osseous free flaps remains a challenge. The purpose of this study is to identify potential risk factors, including osteocutaneous radial forearm versus fibular flap, for need for removal and to describe the fate of implanted hardware.

STUDY DESIGN

Case series with chart review Setting Academic tertiary care medical center.

SUBJECTS AND METHODS

Two hundred thirteen patients undergoing 227 vascularized osseous mandibular reconstructions between the years 2004 and 2012. Data were compiled through a manual chart review, and patients incurring hardware removals were identified.

RESULTS

Thirty-four of 213 evaluable vascularized osseous free flaps (16%) underwent surgical removal of hardware. The average length of time to removal was 16.2 months (median 10 months), with the majority of removals occurring within the first year. Osteocutaneous radial forearm free flaps (OCRFFF) incurred a slightly higher percentage of hardware removals (9.9%) compared to fibula flaps (6.1%). Partial removal was performed in 8 of 34 cases, and approximately 38% of these required additional surgery for removal.

CONCLUSION

Hardware removal was associated with continued tobacco use after mandibular reconstruction (P = .03). Removal of the supporting hardware most commonly occurs from infection or exposure in the first year. In the majority of cases the bone is well healed and the problem resolves with removal.

Fluorescently labeled therapeutic antibodies for detection of microscopic melanoma

OBJECTIVES/HYPOTHESIS

Detection of microscopic disease during surgical resection of melanoma remains a significant challenge. To assess real-time optical imaging for visualization of microscopic cancer, we evaluated three US Food and Drug Administration (FDA)-approved therapeutic monoclonal antibodies.

STUDY DESIGN

Prospective, basic science.

METHODS

Melanoma cell lines (A375 and SKMEL5) were xenografted into the ears of immunodeficient mice. Bevacizumab, panitumumab, tocilizumab, or a nonspecific immunoglobin G (IgG) were covalently linked to a near-infrared (NIR) fluorescent probe (IRDye800CW) and systemically injected. Primary tumors were imaged and then resected under fluorescent guidance using the SPY (Novadaq, Toronto, Ontario, Canada), an NIR imaging system used in plastic and reconstructive surgeries to evaluate perfusion. Mice were also imaged with the Pearl Impulse small animal imager (LI-COR Biosciences, Lincoln, NE), an NIR imaging system designed for use with IRDye800CW. Postresection, small tissue fragments were fluorescently imaged and the presence of tumor subsequently confirmed by correlation with histology.

RESULTS

All fluorescently labeled therapeutic monoclonal antibodies could adequately delineate tumor from normal tissue based on tumor-to-background ratios (TBR) compared to IgG-IRDye800CW. On serial imaging, panitumumab achieved the highest TBRs with both SPY and Pearl (3.8 and 6.6, respectively). When used to guide resections, the antibody-dye conjugates generated TBRs in the range of 1.3 to 2.2 (average, 1.6) using the SPY and 1.9 to 6.3 (average, 2.7) using the Pearl. There was no significant difference among the antibodies with either imaging modality or cell line (one-way analysis of variance).

CONCLUSIONS

Our data suggest that FDA-approved antibodies may be suitable targeting agents for the intraoperative fluorescent detection of melanoma.

Analysis and Review of Outcomes for Cutaneous Squamous Cell Carcinoma Involving the Parotid

Objectives:

An in depth analysis of outcomes following parotidectomy for a cutaneous squamous cell carcinoma.

Methods:

Retrospective review (2003-2012).

Results:

Forty-nine percent of 218 patients presented with a primary lesion (n = 107), and 51% presented with a recurrence (n = 111). Parotid lymph nodes were positive in 52% of patients; 81% had a concurrent neck dissection, and 28% had cervical lymph node metastases. Eighteen percent had both positive parotid and cervical lymph nodes. The majority of margins were negative (49%), with 19% being < 2mm. Preoperative radiation therapy did not decrease the incidence of cervical ( P = 0.27) or parotid ( P = 0.37) lymph node involvement, perineural invasion ( P = 0.08), positive margins ( P = 0.31), facial nerve sacrifice ( P = 0.43), or rate of recurrence ( P = 0.87). The overall 2- and 5-year survival rates were 0.71 and 0.58. Overall 5-year survival was lower for patients presenting with recurrent (0.49) vs. primary disease (0.69; P = 0.04). In addition, decreased overall 5-year survival rates were associated with cervical lymph involvement (0.47 vs. 0.62; P = 0.01) and preoperative radiation therapy (0.39 vs. 0.67; P = 0.037). Interestingly, there was no difference in overall survival when stratified by parotid lymph node involvement ( P = 0.85), margin status ( P = 0.67), perineural invasion ( P = 0.42), temporal bone resection ( P = 0.14), facial nerve sacrifice ( P = 0.92), or type of parotid operation performed ( P = 0.51).

Conclusions:

In this patient population, cervical, but not parotid, lymph node involvement was associated with poor outcomes. Furthermore, radiation therapy prior to a definitive operation resulted in worse outcomes and did not decrease the incidence lymph node metastases.

Hardware Failure after Osseous Free Flap Reconstruction

Objectives:

Understand the underlying reasons for hardware failure after osseous free flap reconstruction.

Methods:

A retrospective chart review of 224 patients undergoing 241 vascularized osseous mandibular reconstructions between the years of 2004-2012 was conducted with a minimum of 6 months follow-up.

Results:

There were 33 (14.7%) patients who underwent removal of the support implant with the most common reason being infection, exposure, or both. The average length of time to removal was 16.3 months, with a bimodal distribution: the majority of removals occurred within the first year, and the second group occurred in the third year. Of patients who had the hardware removed after 3 months, there were 12 (36.4%) who had malunion at the time of removal. In those patients, the inciting factor was resolved upon removal for 18.2% (n = 6) of cases.

Conclusions:

Removal of the supporting hardware most commonly occurs from infection or exposure in the first year. In the majority of cases, the bone is well healed and the problem resolves with removal.

Use of panitumumab-IRDye800 to image cutaneous head and neck cancer in mice

OBJECTIVE

To assess the feasibility of panitumumab in real-time fluorescent imaging and histologic processing of cutaneous squamous cell carcinoma (cSCC) in mice.

DESIGN

A near-infrared (NIR) fluorescent probe (IRDye800CW) was covalently linked to a monoclonal antibody-targeting epidermal growth factor receptor (panitumumab) or nonspecific IgG and injected into mice bearing flank xenografts from a cSCC cell line (SCC-13 or SRB-12; n = 7), human split-thickness skin grafts (STSGs; n = 3), or a human tumor explant (n = 1). The tumor and lymph nodes were imaged and dissected using fluorescence guidance with the SPY imaging system and verified with a charge-coupled NIR system. An NIR scanning device (Odyssey) was used to measure fluorescence intensity in histological sections.

SUBJECTS

Immunodeficient mice.

SETTING

In vivo and in vitro imaging lab.

RESULTS

Tumor tissue could be delineated from the human STSG with tumor-to-background ratios of 4.5 (Pearl) and 3.4 (SPY). Tumor detection was substantially improved with panitumumab-IRDye800 compared with IgG-IRDye800. Biopsies positive for fluorescence were assessed by histology and immunohistochemistry (n = 18/18) to confirm the presence of tumor, yielding a 100% sensitivity. Biopsies of nonfluorescent tissue negative for malignancy (n = 18/18) yielded a specificity of 100%. Furthermore, the SPY system was able to detect residual disease as small as 200 µm in diameter. In addition, the Odyssey confirmed fluorescence of microscopic disease (in tumor samples of frozen and paraffin-embedded histologic specimens) but not in adjacent noncancerous tissue.

CONCLUSIONS

These data suggest panitumumab-IRDye800 may have clinical utility in detection and removal of subclinical cSCC using Food and Drug Administration-approved imaging hardware.

Identification of the optimal therapeutic antibody for fluorescent imaging of cutaneous squamous cell carcinoma

Intraoperative, real-time fluorescence imaging may significantly improve tumor visualization and resection and postoperatively, in pathological assessment. To this end, we sought to determine the optimal FDA approved therapeutic monoclonal antibody for optical imaging of human cutaneous squamous cell carcinoma (cSCC). A near-infrared (NIR) fluorescent probe (IRDye800) was covalently linked to bevacizumab, panitumumab or tocilizumab and injected systemically into immunodeficient mice bearing either cutaneous tumor cell lines (SCC13) or cutaneous human tumor explants. Tumors were then imaged and resected under fluorescent guidance with the SPY, an FDA-approved intraoperative imaging system, and the Pearl Impulse small animal imaging system. All fluorescently labeled antibodies delineated normal tissue from tumor in SCC13 xenografts based on tumor-to-background (TBR) ratios. The conjugated antibodies produced TBRs of 1.2-2 using SPY and 1.6-3.6 using Pearl; in comparison, isotype control antibody IgG-IRDye produced TBRs of 1.0 (SPY) and 0.98 (Pearl). Comparison between antibodies revealed them to be roughly equivalent for imaging purposes with both the SPY and Pearl (p = 0.89 SPY, p = 0.99 Pearl; one way ANOVA). Human tumor explants were also imaged and tumor detection was highest with panitumumab-IRDye800 when using the SPY (TBR 3.0) and Pearl (TBR 4.0). These data suggest that FDA approved antibodies may be clinically used for intraoperative detection of cSCC.

Risk factors for supraglottoplasty failure

OBJECTIVE

To review outcomes after supraglottoplasty for laryngomalacia and identify risk factors for supraglottoplasty failure.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary care children's hospital.

SUBJECTS AND METHODS

Retrospective case series evaluating patient outcomes after supraglottoplasty at an academic medical center between 2004 and 2010. Surgical failure was defined as need for revision surgery, tracheostomy tube placement, or gastrostomy tube insertion. Multivariable logistic regression was performed to identify risk factors for failure.

RESULTS

The authors identified 95 children who underwent supraglottoplasty. After excluding patients with inadequate follow-up data, 74 patients were included. On the basis of chart review, 12 (16%) of those patients were defined as failures according to the criteria above. Age, history of prematurity (<34 weeks' gestational age), weight, growth curve percentile, neurologic/developmental problems, genetic syndrome, cardiac abnormality, synchronous airway lesions, and surgical technique were considered in risk factor analysis. Multivariable logistic regression was performed, revealing history of prematurity to be the only independent risk factor for failure (odds ratio = 4.85; 95% confidence interval, 1.07-22.1; P = .041).

CONCLUSIONS

Outcomes after supraglottoplasty were comparable to previous reports in the literature. History of prematurity should be considered a risk factor for surgical failure.

Response of zooplankton and phytoplankton communities to creosote-impregnated Douglas fir pilings in freshwater microcosms

Creosote has been used extensively as an industrial wood preservative for the protection of marine pilings, railway ties, and utility poles and is a common source of polycyclic aromatic hydrocarbons (PAHs) into aquatic environments. At present, there is little information by which to judge the potential for creosote leached from impregnated pilings to cause toxicity to biota in aquatic environments. The objective of the current study was to assess the effects of creosote on zooplankton and phytoplankton populations in freshwater microcosms in relation to changes in the concentration and composition of PAHs leached from creosote-impregnated Douglas fir pilings during an 83-day exposure period. The study consisted of single microcosms containing one half, one, two, three, four, and six treated pilings. Two microcosms that received untreated pilings were used as controls. The total surface area of pilings in each microcosm was normalized by adding the appropriate number of untreated pilings. Samples were collected periodically between -14 and 83 days pre- and postexposure to determine aqueous concentrations of 15 priority PAHs and to assess the response of zooplankton and phytoplankton communities. Plankton community response to creosote was analyzed using principle responses curves. Peak aqueous concentrations of sigmaPAH occurred at day 7, ranging from 7.3 to 97.3 microg/L. Zooplankton abundance decreased in all microcosms after introduction of the impregnated pilings, with the magnitude of response varying as a function of aqueous creosote concentration. Using inverse regression, a no-observed-effect concentration for the zooplankton community of 11.1 microg/L was estimated. In contrast, algal abundance and diversity increased in all treatments between 7 and 21 days and attained levels up to twice that in control microcosms. This trend most likely reflected decreased grazing pressure because of the decrease in zooplankton populations, but it may also have reflected growth stimulation resulting from exposure to various constituents within the creosote mixture. Our results indicate that creosote leached from impregnated pilings deployed under typical conditions (e.g., wharves) may cause transient toxicity to benthic or limnetic communities shortly after deployment, but this likely poses few long-term risks to aquatic freshwater plankton communities.

Response of phytoplankton communities to liquid creosote in freshwater microcosms

We assessed the response of phytoplankton communities in aquatic microcosms to single applications of liquid creosote. The creosote was applied to 14 microcosms at concentrations ranging from 0.06 to 109 mg/L. Two microcosms served as controls. Phytoplankton samples were collected from each microcosm one week and 1 d before treatment and at 7 and 21 d after treatment. Temporal changes (response-recovery) in phytoplankton community composition were assessed with principal response curves. Creosote had no direct toxic effect on the phytoplankton community based on total abundance and number of taxa. Population levels declined in all treatments between day -1 and day 7, but this trend mirrored a similar decline in the control microcosms. At both 7 and 21 d after treatment, population densities and number of taxa in most treatments exceeded those in the controls and exhibited a parabolic relationship relative to creosote concentration. This relationship was most pronounced at 21 d, at which time population densities and number of taxa at intermediate concentrations were up to twice those at low and high concentrations. This response pattern seems to represent an indirect response to impacts on zooplankton and a corresponding reduction in grazing pressure. In contrast, total algal biomass declined 52 to 97% relative to the controls at all but the lowest creosote concentration at 7 d. This apparent decline was due to a significant proliferation of the alga Closterium moniliforme in the controls and low creosote concentration. At 21 d, no difference was found in total biomass between treated and control microcosms. The results of this study suggest that creosote does not pose a significant direct risk to phytoplankton at concentrations likely to be encountered in most contaminated aquatic environments; however, stimulation of algal populations could occur in situations of long-term chronic exposure or spill events that remove predatory zooplankton populations.

Response of zooplankton communities to liquid creosote in freshwater microcosms

In this study, the response of zooplankton communities to single applications of liquid creosote in model aquatic ecosystems (microcosms) was evaluated. Liquid creosote was applied to 14 microcosms at concentrations ranging from 0.06 to 109 mg/L. Two microcosms served as controls. Zooplankton samples were collected from each microcosm on days 7 and 1 before treatment and on days 2, 5, 7, 14, 21, 28, 43, 55, and 83 following treatment. Temporal changes (response-recovery) in composition of the zooplankton community were assessed using principal response curves (PRC). Creosote induced a rapid, concentration-dependent reduction in zooplankton abundance and number of taxa, with maximum response (50-100% reduction in population densities) occurring between 5 and 7 d after treatment. Taxa that dominated at the time of treatment experienced the greatest impact, as indicated by large, positive species weight values (> 1) from the PRC analysis. Many of these taxa recovered to pretreatment or control levels during the posttreatment period, with the degree and duration of recovery being strongly dependent on concentration. Creosote had little effect on species composition at less than 1.1 mg/L, because changes in the types and relative proportion of species contributed from Cladocera, Rotifera, and Copepoda were comparable to those observed in control microcosms. However, a significant shift in species composition was observed at concentrations greater than 1.1 mg/L; these microcosms were generally dominated by low numbers of rotifers, some of which had not been collected before treatment. Community-level effect concentrations (EC50s) were 44.6 and 46.6 micrograms/L at 5 and 7 d, respectively, based on nominal creosote. Corresponding no-effect concentrations were 13.9 and 5.6 micrograms/L. The results of this field study indicate that creosote may pose a significant risk to zooplankton communities at environmental concentrations potentially encountered during spills and/or leaching events.

Short-term effects of herbicides on primary productivity of periphyton in lotic environments

: Freshwater algae are quite sensitive to herbicides that enter running water ecosystems through direct application, aerial drift, and/or watershed run-off. However, due to a lack of suitable methodologies, few studies examine the effects of such contamination on naturally occurring attached algal communities under field conditions (i. e., exposure regimes using pulsed doses or brief episodes of peak concentrations to simulate surface run-off during storm events). This paper describes a method for determining the acute short-term effects of four herbicides (hexazinone, atrazine, tebuthiuron and metolachlor) on the net primary productivity (NPP) of periphytic algae in the field using a portable bankside incubator; NPP was measured by monitoring changes in oxygen production (mg O2 per m(2)) upper surface of rock substrate per h and mg O2 h per mg chlorophyll using the light-dark technique. All herbicides with photosynthetic inhibition as a mode of action significantly reduced NPP. The lowest observed effect concentrations (LOECs) for the herbicides were 43 μg hexazinone l(-1), 109 μg atrazine l(-1) and 137 μg tebuthiuron l(-1). The no observed effect concentrations (NOECs) for these chemicals were <43 μg hexazinone l(-1), 93 μg atrazine l(-1) and 52 μg tebuthiuron l(-1). Metolachlor did not significantly reduce NPP at the concentrations that were tested (range 19.6-274 μg l(-1)). However, community respiration (which included respiration by invertebrates) was significantly reduced at the highest metolachlor concentration (274 μg l(-1)). Community respiration was not significantly affected by any concentration of the other three herbicides used.

Pesticide residues in freshwater and marine zooplankton: a review

A review of the scientific literature on pesticide residues in freshwater and marine zooplankton indicates that despite the great number of pesticides in current use, only residues of the persistent organochlorine insecticides, many of which have been restricted or removed from general use in North America, have been determined. Much of this information is outdated. In addition, with the exception of the Great Lakes on which limited information is available, reports on residues in freshwater zooplankton are rare. Information on residues of the newer, less persistent but heavily used pesticides is lacking. As an alternative to field sampling and chemical analysis of endemic populations of zooplankton, scientists have modeled the bioaccumulation of pesticides in zooplankton using either laboratory microcosms or mathematical equations. However, the extent and importance of trophic transfer to higher food levels through this intermediary group of organisms is still controversial. In addition, the relationship between accumulation of pesticides and toxicity to zooplankton remains unresolved.