Summer 2016 – GoMRI Researcher Interview with Dr. Frank Hernandez
– JULY 29, 2016
(From Summer 2016 Newsletter) Dr. Frank Hernandez from the University of Southern Mississippi answered a few questions about his RFP-II project, Resolving Deepwater Horizon Impacts on Highly Variable Ichthyoplankton and Zooplankton Dynamics in the Northern Gulf of Mexico, and his role as co-PI of the Consortium for Oil Spill Exposure Pathways in Coastal River-Dominated Ecosystems (CONCORDE).
1. Thank you so much for talking with us! Tell us a bit about your research. What are the goals of your project?
The goals of my RFP-II project are to investigate possible impacts of the Deepwater Horizon oil spill on marine fish early life stages using a long-term data set. Most marine fish eggs and larvae are planktonic, and during the oil spill these “ichthyoplankton” life stages would have been particularly vulnerable. I was fortunate to have been a co-investigator on a long-term plankton survey that was initiated at the Dauphin Island Sea Lab in late 2004 and continued through 2011. These samples provided valuable baseline collections to examine pre- impact, impact, and post-impact estimates of larval fish abundance, distribution, and community composition. With the support of GoMRI, I was able to continue the plankton collections at the University of Southern Mississippi during the summer months of 2013, 2014, and 2015, and examine other factors that influence larval fish survival, including larval fish growth, diet, and body condition.
2. What is your background and how did you get involved with this kind of work?
My background is in fisheries oceanography, with an emphasis on the biology and ecology of larval fishes. I first got involved with ichthyoplankton while working on my MS thesis at the University of North Carolina at Wilmington. I had always been a “fish guy,” but these life stages were completely foreign to me. I had to forget about dichotomous keys and field guides because larval fishes look nothing like their adult forms. Each specimen I examined under the microscope was a puzzle, and I enjoyed the challenge of identifying them. The larval stage is a critical period in the life of fishes, and natural and anthropogenic processes that affect their survival often lead to variable year class success. So not only are larval fish fun, they are very informative! I therefore continued my studies of larval fishes through my PhD work at Louisiana State University and my subsequent research career.
3. What are some of the most significant or exciting findings so far in your work with GoMRI?
To date, we’ve seen that the planktonic communities in the northern Gulf of Mexico appear to be relatively resilient to the impacts of the oil spill, at least in our study region. In terms of numbers of fish larvae, we do not see any significant drop in post-spill abundances for the species we have examined. Similarly, we see resiliency in many of the zooplankton taxa we have examined, which are larval fish food. A major challenge for anyone examining impacts is discerning between Deepwater Horizon effects versus the natural variability in the ecosystem. With Red Snapper larvae, for example, we have found that variable environmental conditions, particularly river discharge, are related to overall larval body condition. However, even after accounting for the effects of these environmental factors, we observed that larval Red Snapper collected during and after the oil spill are in generally poorer condition than larvae collected in years prior to the spill. Although we cannot definitively link poor larval condition of Red Snapper to the oil spill, we have ruled out many other factors, so more investigation is needed.
4. You mention the challenge in differentiating between the impacts of the oil spill versus natural variability in the ecosystem; can you talk about some of the ways in which you are able to discern between the two?
This is a difficult task. One thing we try to do is estimate the amount of environmental “noise” in the patterns we observe by using time series data for variables such as river discharge, temperature, and salinity, among others. We can calculate the ranges of “normal” environmental conditions historically encountered for our sampling region, and compare these ranges with conditions encountered during Deepwater Horizon (2010). If any of the 2010 parameters are outside of our expected conditions, then we must consider that factor as a possible contributing cause.
5. Do you see poorer conditions present in a single year, or do these conditions persist in years following the oil spill as well? If so, how long would you anticipate it would take for larval health to return to “normal?”
For Red Snapper, we’ve observed relatively poor larval body condition for specimens collected in 2010, 2011, and 2013 (unfortunately we did not have data for 2012). We are currently identifying specimens from 2014 to include in our analysis. Again, there are a number of environmental and anthropogenic factors that may account for this, some we have not investigated. It could be due to other environmental factors that play a role in survival during the larval stage, such as predator and prey abundances (something we hope to address next). Or, it could be something that is impacting the spawning adults and affecting larval condition through “maternal effects.” Our work on the larval stages is only one piece of the puzzle, and we hope to fully address some of these questions about long-term effects by combining our findings with those of GoMRI colleagues working with juvenile and adult Red Snapper, thus incorporating all life stages.
6. You have been funded as an individual investigator through RFP-II and also as a co-PI on RFP-IV-funded consortium CONCORDE. Are there similarities between your RFP-II project and your work with CONCORDE? Differences?
I am very fortunate and excited to be a part of CONCORDE. There are certainly similarities in that I am using some of the same approaches to investigate variability in larval fish growth, diet, and condition. For the RFP-II project, the questions were directly related to Deepwater Horizon impacts, and the historic baseline survey allowed me to examine those questions. With CONCORDE, the environmental driver of interest is river discharge. Nutrient inputs and productivity cycles pulse with variable river discharge, and these affect larval fish dynamics, so it’s a very exciting system to examine. Another difference is the scale of the project. I was a single investigator on my RFP-II project, and was able to support a few technicians, a postdoc and graduate student to conduct the research. The exciting thing about CONCORDE is that we have a small army of investigators, postdocs, and graduate students from numerous institutions, and all of us are working toward a common set of goals and using some very sophisticated technology to address our hypotheses. It’s been a very cool experience to say the least.
7. If funding were not an issue, what would you add to your project?
Time, time, and more time! As much as I enjoy larval fish taxonomy, it is a time-consuming task to sort through plankton samples and identify fish larvae. As a result, we often have to focus our efforts on a few target species, as we’ve done with our project (e.g., Red Snapper, Spanish Mackerel). But there are many other species that were present during the oil spill, and we’ve shown that they can have different responses, so doing similar analyses with more species would be informative. Also, we do not have descriptions for the larval stages of many fish species in the Gulf, so often our identifications are limited to the genus or family level. Molecular identification (e.g., DNA barcoding) of as many specimens as possible would be an extremely valuable contribution to the research effort. And lastly, in the years since the oil spill I have heard many plenary speakers and scientific presenters at conferences repeatedly extol the value of baseline data and monitoring efforts. And yet, there is no concerted effort or funding source to support these initiatives. I’ve been able to extend my original plankton time series for a few years with GoMRI support, but this summer is the first since 2005 that my lab is not on the water collecting plankton samples along our historic transects. I know scientists working in other aspects of the Gulf ecosystem are similarly frustrated, so this is not only a personal desire, but a cause that I think many would support. We must find a way to support baseline data collection and monitoring efforts in the Gulf of Mexico.