Geology topics

Michael T. Walsh

Publications and source records attributed to Michael T. Walsh.

5 recordsLinked to original sources

USGS2024

In vitro impacts of glyphosate on manatee lymphocytes

Exposure to contaminants, such as the herbicide glyphosate, can suppress protective immune functions. Glyphosate is the herbicide most used worldwide and has been found in the plasma of more than 50 % of the Florida manatees ( Trichechus manatus latirostris ) and all-year-round in their aquatic environment. Our objectives were to analyze the consequences of glyphosate exposure on their immune responses via T-lymphocyte proliferation assays and transcriptomics. We isolated peripheral blood mononuclear cells (mainly lymphocytes) of free-ranging manatees and performed T-cell proliferation assays. We used transcriptomics to understand the consequences of glyphosate in vitro exposure. The three doses chosen ranged from environmentally relevant concentrations at 10 to 10,000 µg.L −1 that is considered an environmental contamination scenario. Glyphosate caused a dose-dependent reduction in T-lymphocyte proliferation, with a significant mean reduction of 27.3 % at 10,000 µg.L −1 and up to 51.5 % in some individuals. Additionally, T-lymphocyte proliferation was significantly reduced in mid-winter compared to early winter. Transcriptomic analysis of peripheral blood mononuclear cells indicated that all doses of glyphosate (10, 1,000, and 10,000 µg.L −1 ) resulted in up-regulation of genes related to acute phase inflammation and inhibition of the T-lymphocyte proliferation pathway. Exposure to this contaminant along with other environmental stressors, such as extreme winters and red tide, might further affect the adaptive immune response of this threatened species.

Florida↗

USGS2021

Chronic exposure to glyphosate in Florida manatee

Florida manatees depend on freshwater environments as a source of drinking water and as warm-water refuges. These freshwater environments are in direct contact with human activities were glyphosate-based herbicides are being used. Glyphosate is the most used herbicide worldwide and it is intensively used in Florida as a sugarcane ripener and to control invasive aquatic plants. The objective of the present study was to determine the concentration of glyphosate and its breakdown product, aminomethylphosphonic acid (AMPA), in Florida manatee plasma and assess their exposure to manatees seeking a warm-water refuge in Crystal River (west central Florida), and in South Florida. We analyzed glyphosate’s and AMPA’s concentrations in Florida manatee plasma (n = 105) collected during 2009–2019 using HPLC-MS/MS. We sampled eight Florida water bodies between 2019 and 2020, three times a year: before, during and after the sugarcane harvest using grab samples and molecular imprinted passive Polar Organic Chemical Integrative Samplers (MIP-POCIS). Glyphosate was present in 55.8% of the sampled Florida manatees’ plasma. The concentration of glyphosate has significantly increased in Florida manatee samples from 2009 until 2019. Glyphosate and AMPA were ubiquitous in water bodies. The concentration of glyphosate and AMPA was higher in South Florida than in Crystal River, particularly before and during the sugarcane harvest when Florida manatees depend on warm water refuges. Based on our results, Florida manatees were chronically exposed to glyphosate and AMPA, during and beyond the glyphosate applications to sugarcane, possibly associated with multiple uses of glyphosate-based herbicides for other crops or to control aquatic weeds. This chronic exposure in Florida water bodies may have consequences for Florida manatees’ immune and renal systems which may further be compounded by other environmental exposures such as red tide or cold stress.

Florida↗

USGS2019

Serum iron analytes in healthy and diseased Florida manatees (Trichechus manatus latirostris)

Serum iron concentration is usually decreased in true iron deficiency and with inflammatory disease in man and domestic animals. Serum total iron binding capacity (TIBC) may be increased in true iron deficiency and decreased with inflammatory disease. This prospective study was designed to measure serum iron analytes in healthy free-ranging and housed Florida manatees (Trichechus manatus latirostris) of both sexes and various ages and to evaluate the effects of diseases common to manatees on these analytes. Blood samples were collected without anticoagulant from 137 healthy free-ranging manatees, 90 healthy housed manatees and 74 free-ranging diseased manatees, and serum was prepared by centrifugation. Serum iron concentration and unsaturated iron binding capacity were measured colourimetrically, and TIBC and percent transferrin saturation with iron were calculated. Serum amyloid A (SAA) was measured to assist in the health assessment of manatees and provide evidence of inflammation in diseased manatees. Based on the serum iron analytes, iron availability was lower in immature manatees compared with adults, and it was lower in housed manatees compared with free-ranging manatees. In contrast to other mammals studied, serum iron concentration was elevated rather than depressed in late pregnancy. Serum iron concentrations and transferrin saturation with iron percentages were significantly lower, and SAA concentrations were significantly higher, in diseased (ill and injured) manatees compared with healthy manatees. Serum iron concentration and transferrin saturation with iron values were negatively correlated with SAA concentrations, and manatees with the highest SAA concentrations had lower serum TIBC values. These findings indicate that inflammation is the major factor responsible for alterations in iron analytes in diseased manatees. Consequently, hypoferraemia may be used as supportive evidence of inflammatory disease in manatees (unless haemorrhage is also present). A decision threshold of ≤13.8 μmol/l was determined for hypoferraemia using receiver operating curve analysis. Based on studies in man and domestic animals, iron therapy is unnecessary for manatees with hypoferraemia associated with inflammation and has the potential for causing tissue damage and increased susceptibility to bacterial infections.

Florida↗

USGS2018

Serum proteins in healthy and diseased Florida manatees (Trichechus manatus latirostris)

A major goal of this study was to determine whether serum protein fractions of healthy Florida manatees differ with age, sex, or living environments (wild versus housed). A second goal was to determine which serum protein fractions vary in diseased versus healthy manatees. Serum protein fractions were determined using agarose gel electrophoresis. Healthy adults had slightly higher total serum protein and total globulin concentrations than younger animals. This largely resulted from an increase in gamma globulins with age. Total serum protein, albumin, alpha-1 globulin, beta globulin, and total globulin concentrations were slightly higher in housed manatees compared to wild manatees, but there was no significant difference in the albumin/globulin (A/G) ratio, suggesting a difference in hydration between these groups. No significant differences were attributable to sex or pregnancy. Serum albumin concentrations and A/G ratios were significantly lower for manatees with boat trauma, entanglements, emaciation, or cold stress compared to healthy manatees. Variable increases were seen in alpha-1globulins, alpha-2 globulins, beta globulins, and gamma globulins. These globulin fractions contain positive acute-phase proteins and immunoglobulins, and their increases may reflect acute or chronic active inflammation. Changes in serum protein fractions were not consistent enough to justify the use of serum protein electrophoresis as a routine diagnostic test for manatees. However, serum (or plasma) protein electrophoresis is required when accurate values for albumin and globulins are needed in manatees and in determining which protein fractions may account for a hyperproteinemia or hypoproteinemia reported in a clinical chemistry panel.

Comparative Clinical Pathology↗

USGS2016

Baseline reference range for trace metal concentrations in whole blood of wild and managed West Indian Manatees ( Trichechus manatus ) in Florida and Belize

The West Indian manatee ( Trichechus manatus ) is exposed to a number of anthropogenic influences, including metals, as they inhabit shallow waters with close proximity to shore. While maintaining homeostasis of many metals is crucial for health, there is currently no baseline reference range that can be used to make clinical and environmental decisions for this endangered species. In this study, whole blood samples from 151 manatees were collected during health assessments performed in Florida and Belize from 2008 through 2011. Whole blood samples (n = 37) from managed care facilities in Florida and Belize from 2009 through 2011 were also used in this study. The concentrations of 17 metals in whole blood were determined, and the data were used to derive a baseline reference range. Impacts of capture location, age, and sex on whole blood metal concentrations were examined. Location and age were related to copper concentrations as values were significantly higher in habitats near urban areas and in calves. Copper may also be a husbandry concern as concentrations were significantly higher in managed manatees (1.17 ± 0.04 ppm) than wild manatees (0.73 ± 0.02 ppm). Zinc (11.20 ± 0.30 ppm) was of special interest as normal concentrations were two to five times higher than other marine mammal species. Arsenic concentrations were higher in Belize (0.43 ± 0.07 ppm), with Placencia Lagoon having twice the concentration of Belize City and Southern Lagoon. Selenium concentrations were lower (0.18 ± 0.09 ppm) than in other marine mammal species. The lowest selenium concentrations were observed in rehabilitating and managed manatees which may warrant additional monitoring in managed care facilities. The established preliminary baseline reference range can be used by clinicians, biologists, and managers to monitor the health of West Indian manatees.

Aquatic Mammals↗