Environmental Physiology & Toxicology
Grosell Lab


The Lab, Spring 2014
Martin Grosell, Ilan Ruhr (and Chico), John Stieglitz, Ed Mager, Rachael Heuer, Theresa Mackey, Kevin Schauer, Christina Pasparakis and Zongli Yao


Visiting Scientists

Zongli Yao  (zyao@rsmas.miami.edu)

Hypersalinity and ocean acidification are co-occurring stressors in the marine environment. My research is focused on acid-base regulation and osmoregulation physiology of teleost fish exposed to hypersalinity and hypercapnia alone or in combination. Previous research has shown perturbed acid-base balance in fish transferred to hypersalinity or hypercapnia. To date, the combination of these factors has not been examined. The responses to these environmental stressors involve the gill as well as the intestine in an integrative manner and are likely subject to complex regulation. I intend to investigate these responses in the well-studied euryhaline fish, the gulf toadfish (Opsanus beta). The expectation is that lessons learned from the toadfish will also inform us about the physiology of fish living in other environments, such as freshwater and highly alkaline waters.


Postdoctoral Fellows

Ed Mager (emager@rsmas.miami.edu)

My research is focused on examining the acute and chronic effects in commercially important pelagic fish species that result from exposure to polycyclic aromatic hydrocarbons (PAHs), the primary class of toxic agents released from oil.  Specifically, I intend to characterize the PAH concentrations that cause acute mortality during the most sensitive early life stages (i.e. embryonic and larval), as well as examine the long-term effects of PAH exposure by evaluating various physiological parameters.  Previous research has shown that PAHs affect cardiac development and may cause anemia.  These effects would likely impair the ecological fitness of fish populations by reducing swimming performance (e.g. by affecting migration, foraging and/or predator avoidance).  I intend to investigate the potential effects on swimming performance and aerobic scope using swim tunnel respirometery, and evaluate impairment to cardiac development utilizing in vivo microscopic morphometrics.




Ph.D. Students

  Rachael Heuer (rheuer@rsmas.miami.edu)

Recent research has highlighted the formerly understated importance of marine teleost fish to the oceanic carbon cycle. My research interests lie in examining how projected ocean acidification levels will affect acid-base compensatory mechanisms in the gulf toadfish (Opsanus beta).  It has already been established that gastrointestinal HCO3- secretion is a vital component of the toadfish osmoregulatory process, a mechanism hypothesized to also play a role in acid-base balance. In my current research project, I am measuring concentration and rate changes of intestinal HCO3- secretion and rectal HCO3- excretion in toadfish exposed to elevated atmospheric carbon dioxide concentrations predicted for the end of the current and next centuries. I am also interested in quantifying changes in carbonate precipitate formation rates, dissolution potential and carbonate chemical composition as a result of hypercapnia.

  John Stieglitz (jstieglitz@rsmas.miami.edu)

My research focuses on aquaculture, physiology, and toxicology. I am investigating the effects of crude oil and chemical dispersants on economically important finfish species of the Gulf of Mexico, using aquaculture to gain insight into acute toxicity and sub-lethal physiological effects of these toxins on the early life stages of marine fish. As part of this research, I am working to develop sustainable aquaculture techniques and technology for use in hatcheries and offshore aquaculture sites, with specific focus on pelagic species such as tuna (Thunnus spp.), mahi-mahi (Coryphaena hippurus), cobia (Rachycentron canadum), goggle eye (Selar crumenophthalmus), and Florida pompano (Trachinotus carolinus) in an effort to further develop these species for use in marine finfish aquaculture and aquatic toxicology.

  Ilan Ruhr (iruhr@rsmas.miami.edu)

Marine fish face a suite of physical factors that affect their everyday lives. Most important of these is the high salt content of the oceans and because of this obstacle, fish must not only prevent the loss of water to their environment, but also absorb it efficiently into their bodies. In my research, I study how the effects of osmoregulatory challenges in the toadfish (Opsanus beta) intestine affect their ability to regulate ions and absorb water. I focus on guanylin and uroguanylin, a family of intestinal peptides, which activate the opening of intestinal chloride channels via a receptor-mediated cascade. This mechanism allows chloride ions (and bicarbonate ions) to exit the intestinal cell and enter the lumen of the intestine. The purpose of this study is to determine how guanylin and uroguanylin are transcriptionally regulated when environmental salinity changes. Further experiments will test the effects of varying pH levels in situ on the capability of toadfish to withstand different environmental salinity regimes.

  Kevin Schauer (kschauer@rsmas.miami.edu)

As part of their osmoregulatory strategy, marine bony fish produce CaCO3 precipitates in their intestine that are later excreted. Recent estimates suggest that 3 to 15% of the total oceanic carbonate is produced in this way. My research is focused on the organic material that is found in these CaCO3 precipitates. Preliminary data suggests that there are proteins, and likely other organic compounds as well, that are secreted in the intestine of marine fish to catalyze the formation of the CaCO3 precipitates. Using strategies such as mass spectrometry based proteomics and metabolomics, I aim to identify and characterize the organic portions of these precipitates.

  Christina Pasparakis  (cpasparakis@rsmas.miami.edu)

Project description coming soon...



Undergraduate Students

  Jessica Wingar  (j.wingar@umiami.edu)

Project description coming soon...

  Theresa Mackey  (t.mackey2@umiami.edu)

Project description coming soon...