Characterizing the Coastal Carbon Regime experienced by Longfin Inshore Squid, Doryteuthis pealeii, during Breeding Season
Ocean acidification, as a realm of study, is gaining ground as we begin to appreciate the immediate and relevant physical changes occurring in our oceans and as we learn more about its impacts on organisms and ecosystems. The global increase in atmospheric carbon dioxide levels since the advent of the Industrial Age due to anthropogenic input is a fairly well described and accepted phenomenon at this point, but is often bogged down in projections of future levels and potential impacts. One of the emerging and vital research avenues in OA, however, focuses on the dynamics of the coastal carbonate system, which can show drastic variability across temporal scales (Johnson et aI., 2013). Examination of the susceptibility of coastal regions to changes in carbon and pH levels is beginning to show that areas like the northwest Atlantic are at higher risk of rapid changes due to OA (Wang, 2013). Given a variable coastal region susceptible to shifts in CO2 and pH, the question becomes, what types of OA regimes are the organisms in that region experiencing throughout their life history?
Squid are a vital component of the pelagic food web, providing a link between trophic levels as both a significant predator and prey. Squid are also an important taxa for fisheries, with the Longfm Inshore Squid, Doryteuthis pealeii, being a major stock in New England. Kaplan et al. showed that paralarval D. pealeii are deleteriously impacted by extremely elevated CO2 conditions (2013). My thesis work will expand on this study and began by looking at the morphological and physiological impacts on paralarvae over a range of CO2 exposures during the 2013 breeding season. Early results indicate that delays to hatching time are seen at exposures of at least 1300ppm. This value would not be of concern until many years in the future based on standard atmospheric carbon models. Given, however, the strong spatial and temporal variability in coastal acidification, there is a potential that adults, eggs, and paralarvae are faced with harmful CO2/pH levels during the course of the breeding season.
The goal of my thesis research is to characterize the range of ecophysiological impacts that ocean acidification will have on squid, but currently the only funded component is focused almost entirely on metabolic and biogeochemical effects on para larvae through lab experimentation. In order to connect that research to the broader context of the OA problem, the physiology needs to be linked with the ecology and grounded by the natural physical conditions. Describing the actual OA regimes encountered by D. pealeii provides groundtruthing to establish a baseline for "modem conditions," as opposed to the 400ppm assumption, and helps to clarify the relevancy of projected impacts of increased acidification. There is also the potential that seasonal variability in acidification over the breeding period seen in the field could correlate to seasonal variation in impact/response to acidification conditions seen in the lab, which could expand into a significant thesis component.
In order to determine the CO2 environments D. pealeii are exposed to during the peak breeding season, field sampling for critical physical parameters (alkalinity, salinity, temperature, pH, and DIC) is needed. This would consist of monthly sampling trips, from April to October, to the locations of breeding schools. At these locations, we would take CTD readings and Niskin bottle samples at the surface and at the depth of the squid. This should entail three data points per trip, at two depths, for one trip per month, for a total of 42 samples. We will use the WHOI Balena, a small RHIB, to sample from. This proposed support would cover fuel costs for the trips and associated sampling supplies. This includes the sample bottles and to the processing of the water samples on a VINDTA for measurements of alkalinity and dissolved inorganic carbon.
The work leverages a NSF grant currently funding the expanded exploration OA impacts on D. pealeii paralarvae only covers lab-based study looking at morphology and physiology under artificial conditions. A later stage component of the grant allows for an in-lab experiment to see if adult females will preferentially delay egg-laying when exposed to increased levels of CO2, but does not allot any funds to expand and support that study by looking at natural exposure to the breeding population. In order to incorporate physical and ecological factors, and take a more interdisciplinary approach to the problem of OA and squid, support is needed from outside of this grant. Samples will be obtained using the Mooney Lab's CTD and Niskin samplers, but experimental and logistical costs remain to be covered in order for this component of the project, and my thesis research, to be carried out.
Johnson, Z. I., Wheeler, B. J., Blinebry, S. K., Carlson, C. M., Ward, C. S., & Hunt, D. E. (2013). Dramatic variability of the carbonate system at a temperate coastal ocean site (Beaufort, North Carolina, USA) is regulated by physical and biogeochemical processes on multiple timescales. Presented at Ocean Acidification PI Meeting, Washington D.C., September 2013.
Kaplan, M. B., Mooney, T. A., McCorkle, D. C., & Cohen, A. L. (2013). Adverse Effects of Ocean Acidification on Early Development of Squid (Doryteuthis pealeii). PLOS One, 8(5): e63714.Wang, Z. A., Wanninkhof, R., Cai W., Byrne, R. H., Hu, x., Peng, T., & Huang, W. (2013). The marine inorganic carbon system along the Gulf of Mexico and Atlantic coasts of the United States: Insights from a transregional coastal carbon study. Limnology and Oceanography, 58(1): 325-342.