The Marine Environmental Sciences Consortium (MESC) are awarded a grant to acquire a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) instrument for its Dauphin Island Sea Lab (DISL) in Alabama. This instrument will enable DISL and regional scientists to investigate myriad questions related to the marine ecosystem in the northern Gulf of Mexico and elsewhere, as well as to conduct archaeological and biogeochemical research. Example of the types of research to be conducted include 1) examining habitat utilization and metapopulation structure in marine fishes; 2) relating anthropogenic sources of nutrients in coastal waters to local and regional freshwater input; 3) employing Si isotope dilution protocols to examine silcon cycling processes and the global carbon cycle; and, 4) examining the environmental history of fish and shellfish resources of Native Americans in the southeastern US via LA-ICP-MS analysis of otoliths and shells found in middens.
The LA-ICP-MS instrument will have substantial broader impacts by facilitating research on a wide range of topics well-aligned with public and governmental needs. Marine education activities also will be strengthened by exposing DISL undergraduate and graduate students to the latest technology through coursework and research projects. The instrument and results of studies undertaken with it will enhance the education and outreach activities of DISL's Discovery Hall Program, which is a well-regarded K-Gray program that educates over 5,000 students annually through its year-long program and through the NSF-sponsored COSEE Gulf of Mexico program. Lastly, the novelty and enhanced research capabilities that the LA-ICP-MS instrument will bring to DISL will greatly assist efforts in recruiting students from underrepresented groups, which will occur among member universities of the MESC and through the Alabama Alliance for Graduate Education and Professoriate.
The purpose of this project was to acquire a Laser Ablation-Inductively Coupled Plasma-Mass Spectrometer (LA-ICP-MS; Figure 1) to support marine science research and education the Dauphin Island Sea Lab (DISL) in the northern Gulf of Mexico. An LA-ICP-MS is an instrument that is used to measure trace concentrations of elements or isotopes down to very low (parts per quadrillion) concentrations. These concentrations can be measured in solutions, like seawater, or the laser can be utilized to blast small (< 10 mm) pits into solid materials and then the vapor from these blasts is analyzed by the ICP-MS to measure elements at trace levels. The relevance of this is that key environmental processes often rely on trace levels of micronutrients that need to be measured to examine ecosystem function and productivity. However, many elements in freshwater, brackish, or saltwater ecosystems also can be harmful to wildlife or people even at ultra-trace levels. Without sophisticated instruments, those pollutants could be present but never detected. Another application of LA-ICP-MS technology is examining the incorporation of trace metals into hard structures of aquatic animals with (vertebrates) and without (invertebrates) backbones. One example of this is analyzing laser transects across clam or oyster shells to determine if the animals have been exposed to harmful metals at some stage of their lives. This is possible because clams shells and oysters lay down growth rings as the animal grows. Therefore, not only can the presence of harmful elements be detected, but their concentrations can be related back to a specific year or time period in the animal’s life. Fishes have similar time-keeping structures in their bodies. For example, bony fishes have earstones, or otoliths, in their heads that aid in balance and hearing but also lay down growth zones into which metals from the environment are incorporated. Elasmobranchs, like sharks and rays, do not have otoliths in their heads, but we have recently learned that their vertebrae, which have distinct growth zones like clam shells or bony fish otoliths, also incorporate metals from the environment as the shark or ray grows. Sometimes these metals are analyzed to estimate exposure to pollutants. However, certain naturally occurring elements, like strontium (Sr) or barium (Ba), serve as useful indicators of freshwater, brackish water, or saltwater environments (Figure 2). This is because Sr typically is much higher in the ocean and Ba is typically much higher in rivers, thus gradients in their concentrations can indicate freshwater versus saltwater residency of the fish. This is particularly useful for fishes like salmon or bull sharks that can spend part of their lives in rivers or lakes and part of their lives in the ocean. Another application of LA-ICP-MS technology is examining micronutrients in seawater that affect phytoplankton growth and cell division. Phytoplankton are critically important to the global carbon cycle, and also are impacted by the rise in CO2 (carbon dioxide) concentrations in the air and sea. One way to examine the dynamics of a particularly important group of phytoplankton, the diatoms, is via analysis of silcon (Si) concentrations in the ocean. Diatoms have shells or tests composed of a type of silicon glass (biogenic SiO2) that they form themselves, thus silicon is an important nutrient for diatom growth and reproduction. Despite the importance of diatoms in the oceanic foodweb, and their role in the global carbon budget, there is actually very little information on silica (dissolved Si) profiles in the water column around the world. This is mostly due to the fact that methods to measure silica are time consuming and expensive. However, the new ICP-MS at the DISL has the ability to run seawater samples directly, which greatly simplifies sample preparation for silicon analysis methods. Methods being developed at DISL promise to allow inexpensive and quick analysis of silicon stable isotopes (isotopes that do not undergo radioactive decay) that will be useful to examine silicon cycling in different ecosystems around the world. In turn, this will allow greater understanding of processes effecting diatom productivity as well as the global carbon budget. A final but important purpose for DISL’s purchase of a new LA-ICP-MS system is to provide students exposure to cutting-edge science and technology. This is already paying dividends as DISL graduate students are employing the LA-ICP-MS system to fingerprint blacktip shark nurseries with trace metal concentrations in the vertebrae of juveniles, to examine manatee migration routes based on elemental signatures incorporated into the earbones of these marine mammals, and to examine the movement of a fish, red drum, from inshore nursery areas to offshore adult habitats. Other innovative undergraduate and graduate research projects are sure to follow as researchers at DISL and from around the region design new studies to take advantage of this world class technology.
