Today I chatted with Megan Stolen a research scientist at Hubbs-SeaWorld Research Institute in Florida. Megan is an expert in marine mammal biology and stranding investigation. She also studies North American river otters which includes citizen science approach, as part of One Health. She works at the interface of ecology, conservation medicine and forensics.
She explains how she got involved in the marine mammal field. She told us why during cetacean stranding, it is important to pass on information to the general public and how everybody can create change in the world. «Without explaining Science to the world, science does not really do anything as far as Conservation goes».
You can find more about Megan and her institution here: https://hswri.org/staff/scientists/megan-k-stolen-ms/
You want to know more about her work: check below:
Comparison of during bloom and inter-bloom brevetoxin and saxitoxin concentrations in Indian River Lagoon bottlenose dolphins, 2002-2011.
Fire, S.E., J.A. Browning, W.N Durden and M.K. Stolen. Aquatic Toxicology 218 (2020) 105371.
Harmful algal bloom (HAB) toxins have severe negative impacts on marine mammals, particularly for Florida bottlenose dolphins (Tursiops truncatus) which frequently experience mass mortality events. Dolphins on the Florida Atlantic coast inhabit a region endemic to two HAB species, Karenia brevis and Pyrodinium bahamense, which produce the neurotoxins brevetoxin (PbTx) and saxitoxin (STX), respectively. Although toxic HABs and associated dolphin mortality events have been reported from this region, there is a lack of available data necessary for comparing toxin exposure levels between bloom (‘exposed’) conditions and non-bloom (‘baseline’) conditions. Here we present a 10-year dataset of PbTx and STX concentrations detected in dolphins stranding in this region, and compare the toxin loads from HAB-exposed dolphins to those detected in dolphins recovered in the absence of a HAB. We analyzed liver tissue samples from dead-stranded dolphins (n=119) recovered and necropsied between 2002-2011, using an enzyme-linked immunosorbent assay (ELISA) modified for use with mammalian tissues. For dolphins recovered during baseline conditions, toxin-positive samples ranged in concentration from 0.27 to 1.2 ng/g for PbTx and from 0.41 to 1.9 ng/g for STX. For K. brevis-exposed dolphins, concentrations of up to 12.1 ng PbTx/g were detected, and for P. bahamense-exposed dolphins, concentrations of up to 9.9 ng STX/g were detected. Baseline PbTx values were similar to those reported in other regions where K. brevis blooms are more frequent and severe, but HAB-exposed PbTx values were considerably lower relative to these other regions. Since no baseline STX dolphin data exist for any region, our data serve as a first step towards establishing reference STX values for potential dolphin mortality events associated with STX-producing blooms in the future. This study demonstrates that although HABs in eastern Florida are only infrequently associated with dolphin mortalities, the presence of toxins in these animals may pose significant health risks in this region.
Bilateral polycystic kidneys and focal renal cystadenoma in a pygmy sperm whale, Kogia breviceps.
Rousselet, E. , M. Stolen, W.N. Durden, T. Mazza, N. Stacy, and D. Rotstein. 2018. Journal of Wildlife Diseases. Doi: 10.7589/2018-01-019
An adult male pygmy sperm whale ( Kogia breviceps) stranded alive at a beach in Florida, USA, in 2016. Main postmortem examination findings included bilateral multifocal variably sized renal cysts, focal renal cystadenoma, and mild dilation of the renal pelvises. The role of these renal lesions in the stranding of this whale is unknown.
Monitoring seasonal abundance of Indian River Lagoon bottlenose dolphins (Tursiops truncatus) using aerial surveys.
Durden, W.N., E. D. Stolen, T. A. Jablonski, S. A. Puckett, and M. K. Stolen. 2017. Aquatic Mammals.
Systematic long-term monitoring of
abundance and distribution is essential to management and conservation and necessary to assess mortality
trends and anthropogenic
impacts for cetacean stock assessment. Line-transect aerial surveys (n=42) were conducted to assess
bottlenose dolphin (Tursiops truncatus) abundance, distribution, and group composition in the Indian
River Lagoon (IRL) estuary
system, Florida, from 2005 to 2011. Multiple covariate distance sampling was used to estimate abundance, and
experimental trials were utilized to estimate dolphin availability. Abundance estimates varied seasonally,
ranging between 483 (95%
CI=345 to 672; summer 2008) and 1,947 dolphins (95% CI=1,198 to 2,590; winter 2009-2010), with a mean
abundance of 1,032 dolphins (95% CI=809 to 1,255). The largest abundance estimates for IRL dolphins occurred
during extremely cold
winter events, suggesting seasonal changes may influence dolphin movements. Mean visibility depth (125.14 ±
38.29 cm) suggested the availability bias did not largely influence estimates of dolphins in this shallow
estuary when surveys are
conducted under optimal sighting conditions. However, there was some evidence of seasonal changes in
availability that may influence abundance estimation, and this should be further investigated. Seasonal trends
and corresponding genetic
and movement data suggest Mosquito Lagoon may be a disjunct community from the IRL proper. This study provides
abundance data to assess the IRL bottlenose dolphin stock prior to the largest Unusual Mortality Event on
record for this
population, which occurred in 2013.
Detection of Brucella spp. in Bottlenose Dolphins (Tursiops truncatus) by a Real-Time PCR Using Blowhole Swabs.
Wu, Q., J. Conway, K. M. Phillips, M. Stolen, W. N. Durden, D. Fauquier, W. E. McFee, and L. Schwacke. 2016. Diseases of Aquatic Organisms, 120: 241- 244, doi: 10.3354/dao03034
Blowhole swabs are a simple and non-invasive method for collecting samples from cetaceans and can be used for screening large numbers of animals in the field. This study reports a real-time PCR assay for the detection of Brucella spp. using blowhole swab samples from bottlenose dolphins Tursiops truncatus stranded in the coastal region of Virginia, South Carolina and northern Florida, USA, between 2013 and 2015. We used real-time PCR results on lung samples from the same dolphins in order to estimate the relative sensitivity and specificity of real-time PCR of blowhole swabs. Brucella DNA was detected in lung tissue of 22% (18/81) and in blowhole swabs of 21% (17/81) of the sampled dolphins. The relative sensitivity and specificity of real-time PCR on blowhole swabs as compared to the real-time PCR on lung samples was 94% (17/18) and 100% (63/63), respectively. These results indicate that real-time PCR on blowhole swabs may be used as a non-invasive test for rapid detection of Brucella spp. in the respiratory tract of dolphins. To our knowledge, this is the first report on the use of blowhole swabs for detection of bacterial pathogens by real-time PCR in bottlenose dolphins.
Individual specialization in the foraging habits of female bottlenose dolphins living in a trophically diverse and habitat rich estuary.
Rossman,S., P.H. Ostrom, M. Stolen, N.B. Barros, H. Gahdhi,, C. A. Stricker, and R.S. Wells. 2015. Oecologia 178 (2):415-425.
We examine individual specialization in foraging habits (foraging habitat and trophic level) of female bottlenose dolphins (Tursiops truncatus) resident in Sarasota Bay, Florida, USA, by analyzing time series of stable isotope (δ15N and δ13C) values in sequential growth layer groups within teeth. The isotope data provide a chronology of foraging habits over the lifetime of the individual and allowed us to show that female bottlenose dolphins exhibit a high degree of individual specialization in both foraging habitat and trophic level. The foraging habits used by adult females are similar to those they used as calves and may be passed down from mother to calf through social learning. We also characterized the foraging habits and home range of each individual by constructing standard ellipses from isotope values and dolphin sightings data (latitude and longitude), respectively. These data show that Sarasota Bay bottlenose dolphins forage within a subset of the habitats in which they are observed. Moreover, females with similar observational standard ellipses often possessed different foraging specializations. Female bottlenose dolphins may demonstrate individual specialization in foraging habits because it reduces some of the cost of living in groups, such as competition for prey.
A brevetoxin-associated mass mortality event of bottlenose dolphins (Tursiops truncatus) and Florida manatees (Trichechus manatus latirostris) along the east coast of Florida.
Fire S.E, L. Flewelling, M. Stolen, W. Noke Durden, M. de Wit, A. Spellman, Z. Wang. Marine Ecology Progress Series. 526:241-251.
A mass mortality of bottlenose dolphins Tursiops truncatus and Florida manatees Trichechus manatus latirostris co-occurred with a severe bloom of the toxic algal species Karenia brevis along the eastern coast of Florida, USA, between October 2007 and January 2008. Brevetoxin (PbTx), a potent neurotoxin produced by this marine alga, was detected in 69 and 92% of the tested carcasses of manatees and dolphins, respectively, at concentrations similar to those reported for earlier mortality events along the west coast of Florida. Brevetoxin was also detected in fetal and neonate dolphins, providing evidence of maternal transfer of the toxin in wild populations. This study is the first to document a brevetoxin-associated marine mammal mortality event along the Atlantic coast of Florida. It also demonstrates that, despite the rarity of K. brevis blooms in this region, significant negative impacts to marine mammals inhabiting this region can occur
Fatal Asphyxiation in Bottlenose Dolphins (Tursiops truncatus) from the Indian River Lagoon.
Stolen M., J. St. Leger, W.N. Durden., T. Mazza, E. Nilson (2013) PLoS ONE 8(6): e66828. doi:10.1371/journal.pone.0066828
Multiple single case reports of asphyxiation in dolphins caused by fish lodged in the esophagus exist. However, the significance of this cause of mortality in a single population has not been documented. We performed a retrospective evaluation of pathology records from stranded bottlenose dolphins (Tursiops truncatus) from the Indian River Lagoon to evaluate the impact of this cause of death on this population. From 1997 to 2011, asphyxiation due to choking was identified as the cause of death in 14 of 350 cases (4%). Sampling of an unrelated but adjacent population over this same period yielded 186 necropsy cases of bottlenose dolphins with no cases of asphyxiation. Asphyxiated animals presented with a fish lodged in the cranial esophagus associated with a dislocated and obstructed or compressed larynx. There was no clear sex predilection. Affected animals included 12 adults and two juveniles. The fish species involved included sheepshead, black chin tilapia and striped mojarra. In five cases, recreational fishing gear was also present. Cetacean choking is related to selection of prey fish species with strong dorsal spines and may be secondarily associated with fish attached to fishing gear. Prey abundance and dolphin behavior may influence these selections. Environmental alterations leading to changes in prey availability or increased interactions with fishing gear may change the significance of fatal choking in dolphin populations.
Effects of recreational fishing gear on bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon system, Florida.
Stolen, M.K., W.N. Durden, T. Mazza, N. Barros, J. St. Leger. 2013. Marine Mammal Science 29: 356-364