Stony Brook, NY, August 13, 2013 - Earlier this year, Sea Grant scholar Theresa Hattenrath-Lehmann
was recognized as one of Stony Brook University
(SBU)'s top graduate students for this year's edition of the Graduate Student Achievements.
In addition to several travel awards, she was also awarded the Best Student Poster Award (Maureen Keller Award) and the Best Student Poster (15th International Conference on Harmful Algae, Changwon, Korea).
An exceptional graduate student during the past six years under the advisement of SBU School of Marine and Atmospheric Sciences (SoMAS) investigator Chris Gobler
, Hattenrath-Lehmann has made a series of critical discoveries regarding the toxic algae Alexandrium
that have, in the words of the Executive Director of Citizens Campaign for the Environment, “…literally saved lives of Long Islanders.”
Since 2008, on at least six occasions, Hattenrath-Lehmann has discovered the outbreak of toxic Alexandrium
blooms in waters of Long Island that were open to shellfishing and has immediately alerted the New York State Department of Environmental Conservation
, which subsequently analyzed shellfish and, indeed, found they were contaminated with Paralytic Shellfish Poisoning (PSP) and closed the shellfish beds.
Certain dinoflagellate populations of the genus Alexandrium
can bloom and cause a toxic 'red tide.' Shellfish that readily feed upon a species of Alexandrium
during these blooms become toxic themselves and can cause PSP, which is a major economic problem for the shellfish industry.
Additionally, Hattenrath-Lehmann has also made tremendous progress in discovering the cause of these blooms. And, last but not least, she recently discovered a second threat to the health of New York citizens, specifically blooms of Dinophysis
that cause Diuretic Shellfish Poisoning (DSP).
This work is tied to one of Gobler's New York Sea Grant
-funded two-year Long Island Sound-centric harmful algal bloom projects that wraps up this year. The focus of this study is the composition of primary producers of Long Island Sound (LIS), which Gobler says has undergone a fundamental phase shift during the past decade as intense PSP- and DSP-producing dinoflagellate blooms have become annual events within multiple nearshore regions. Another contributing factor is the relative abundance of dinoflagellates within the open waters of LIS, which has concurrently increased.
This project is based on the hypothesis that this phase shift has been initiated by a series of anthropogenic alterations to LIS ecosystems (those caused or produced by humans), including nitrogen loading, organic matter loading, and factors related to climate change including increasing temperatures and increasing concentrations of CO2.
"Since all of these factors except temperature can be directly or indirectly managed on a watershed level," says Gobler, "determining the primary causes of PSP- and DSP-producing dinoflagellate blooms and dinoflagellate dominance in Long Island Sound will be the first step toward developing plans to control and mitigate these events."
Another Sea Grant scholar, Laura M. Treible
, presented her graduate studies research at SBU SoMAS' Student Symposium earlier this year. She is pictured above at the Symposium with former NYSG Director Jim Ammerman
. Photo by James Pearce.
While at SBU, Treible has been a scholar on two projects, the first of which was the NYSG-funded “Impacts of Climate Change on the Export of the Spring Bloom in Long Island Sound” with investigators Gobler and Darcy Lonsdale
The rationale here is a warming trend: between 1976 and 2001, seawater temperatures in LIS have increased by 1.5 degrees Celsius, which represents typical patterns seen along the northeast US coast. "It is well established that temperature affects numerous ecological and evolutionary processes," says Lonsdale. More specifically, as was the rationale for this multi-year project that wrapped up in 2012, it has been demonstrated in other temperate coastal waters that during warm winters, the winter-spring bloom is suppressed and abundances of zooplankton (a primary food source in the aquatic ecosystem) increase while nutrient levels remain high, which help to "feed" potential algae blooms.
Thus, it has been hypothesized that increased zooplankton grazing is the mechanism of bloom suppression. However, until this project, this hypothesis had yet to be tested in LIS or elsewhere in the U.S. "Clearly, continued temperature-driven suppression of the spring bloom brought about by global warming will significantly alterthe mixing of nutrients between the Sound's benthos [bottom] and the pelagic habitat [water column] as well as the production of coastal fisheries," continues Lonsdale. And, although the study was conducted in Long Island Sound, she adds that the results are applicable to other coastal systems.
The second NYSG-funded project that Treible worked on, which encompassed her thesis, was “Influence of Gelatinous Zooplankton on Nutrient Cycles, Hypoxia, and Food Webs Across Long Island Sound,” also being conducted by Gobler and Lonsdale. Treible was awarded the Sea Grant Thesis Completion Award to finish up her Master's thesis this past spring semester for this two-year project, which wraps up in 2013.
Here, Treible provided some notes from her thesis presentation given at the symposium:
Gelatinous zooplankton blooms have been increasing in magnitude and frequency globally. Seasonal variations in food availability and temperature can trigger a population bloom and subsequent crash in coastal and estuarine waters. When determining nutrient budgets, an important process is the recycling of nutrients within a system (also known as "benthic pelagic coupling").
Gelatinous zooplankton, including the most common species in LIS, the ctenophore Mnemiopsis leidyi
, are capable of significant rates of nutrient regeneration, which is important, as nutrient levels is one of the key factors in determining the probability of an algal bloom forming and thriving.
During 2011, the population biomass of M. leidyi
was monitored and nutrient regeneration rates (such as ammonium and phosphate) were calculated based on laboratory experiments. Ammonium, a waste product of metabolism of animals, is an important source of nitrogen for many plant species. If levels of nitrogen and phosphorus are high — nutrients whose sources usually come from land as run-off from things such as fertilizers — that only helps build the case for the algae to proliferate. When algae from these blooms later die off, they create an anoxic, or low-oxygen, environment that can kill fish and other organisms.
Preliminary results from 2011 indicate that ctenophores in LIS have the potential, at times, to overturn these nutrients at relatively substantial rates. However, in 2012, the ctenophore bloom never occurred, suggesting that rates of nutrient regeneration by gelatinous zooplankton also can vary widely on an interannual basis, complicating the assessment of the nutrient budget for LIS.
"To date, gelatinous zooplankton have received little research
attention in LIS," says Lonsdale. "Our efforts are resulting in new information on
the population dynamics of ctenophores and jellyfish and
contribute to a greater understanding of the structure and
function of the planktonic food web and nutrient cycling."
— Compiled by Paul C. Focazio