Deepwater Horizon Oil Spill: Natural Resource Damage Assessment (NRDA) of the St. Joseph Bay bottlenose dolphin community

By Brian Balmer, MS, PhD Student, Chicago Zoological Society and University of North Carolina Wilmington

In response to the Deepwater Horizon oil spill, we were contracted to perform a Natural Resource Damage Assessment (NRDA) on the St. Joseph Bay bottlenose dolphin community. The overall goals of the NRDA process, which is part of NOAA’s Damage Assessment, Remediation, and Restoration Program (DARRP), are to:

1) Identify the extent of resources that were damaged

2) Determine methods for resource restoration

3) Assess the amount of restoration required to bring the

resources back to levels pre-oil spill

Although it was uncertain if the Deepwater Horizon oil spill would reach St. Joseph Bay, the bottlenose dolphins in this region are one of the best-studied communities along the northern Gulf of Mexico coast. Since 2004, there have been two health assessments and follow-up radio tracking on 29 individuals, 103 remote biopsy samples collected, and 165 photo-identification surveys performed on the St. Joseph Bay bottlenose dolphin community, with a catalog of over 350 individuals. Thus, the bottlenose dolphins in St. Joseph Bay could provide insight into possible effects that the oil spill might have on other coastal bottlenose dolphin communities in the more affected regions of the northern Gulf coast.

“X23” with “X29” and calf
“X23” with “X29” and calf travelling past oil containment booms in Crooked Island Sound, along the northern Gulf coast of Florida.

The goals for this particular NRDA assessment were to monitor the St. Joseph Bay (and vicinity) bottlenose dolphins before, during, and after the oil spill. Specifically, remote biopsy samples from individual dolphins were to be collected and analyzed for contaminants before oil reached the region as well as if/when oil actually entered St. Joseph Bay. Seasonal abundance estimates utilizing mark-recapture, photo-identification surveys were to be performed during the same time periods as the above mentioned biopsy sampling, as well as an additional set of surveys planned for February 2011. The St. Joseph Bay research is part of a larger study by NOAA that includes similar efforts in Barataria Bay and Chandeluer Sound in Louisiana, and Mississippi Sound.

The “pre-oil” surveys for this assessment were conducted during 17 – 30 June 2010. During this survey effort, 21 remote biopsy samples were collected, and 123 distinctive dolphins were identified. In addition, 14 of the 29 individuals that were captured during health assessments in 2005 and 2006 were re-sighted, of which 6 females had new calves that had not been sighted until these surveys. No oil was observed in the region, but remediation efforts were apparent, with oil containment booms positioned along much of the coastline surrounding St. Joseph Bay. Abundance estimates are typically low during the summer and winter, with year-round residents (approximately 120 individuals) inhabiting the St. Joseph Bay region. During spring and fall, a two to three fold increase of animals is observed in which the majority of individuals are suspected to be seasonal residents or transients to St. Joseph Bay. Interestingly, the abundance estimates generated from these June 2010 surveys were much higher than expected and more similar to the spring and fall time periods when an influx of animals is observed in the region.

At the beginning of August 2010, when it was evident that the oil spill was not going to come into direct contact with the St. Joseph Bay region, the second round of remote biopsying and photo-identification surveys for NRDA was performed. During this survey effort, an additional 17 biopsy samples were obtained and 18 of the 29 individuals that were captured during previous health assessments were sighted. Although photo analysis is not complete for this portion of the project, preliminary data suggest that the abundance estimates for August 2010 will be similar to “typical” summer estimates in St. Joseph Bay, with a lower number of individuals sighted, primarily those with long-term residency patterns to the region. No oil was observed during this survey period and our field crew was able to observe the oil containment booms along the St. Joseph Bay coastline being removed by the hard working remediation crews; an encouraging sight to witness when just a few months earlier the ecosystem of St. Joseph Bay was under threat from the worst marine oil spill in history.

Funding for this research was provided by NOAA’s Damage Assessment, Remediation, and Restoration Program.

Human Interactions and Impacts

By Randall S. Wells, PhD

By mid-May 2010, it was believed by many that the Deepwater Horizon oil spill was destined to be a major environmental catastrophe for the Gulf of Mexico. Communities all around the Gulf and beyond were bracing for the potential arrival of oil. Because of the Loop Current, a major current sweeping northward toward Louisiana from the Yucatan Channel, and then southward along the edge of the west Florida shelf, and because of the uncertainties associated with wind-driven water movements accompanying the upcoming hurricane season, there was much concern about oil approaching the west coast of Florida. In preparation for the possibility of oil reaching Sarasota Bay, we

“Clown”(FB89), in 1999
“Clown”(FB89), was first documented in nearshore Gulf waters 29 years ago, but had not been seen since 1999

obtained a grant from the Morris Animal Foundation’s Betty White Wildlife Rapid Response Fund that enabled us to establish baselines in terms of concentrations of environmental contaminants in tissues of dolphins in Sarasota Bay and within 5 miles of the Gulf beaches, and to determine the abundance and distribution of these animals in advance of the arrival of oil. The grant also supported follow-up sampling and surveys after the oil arrived. Comparisons of before- and after-exposure data would allow identification of impacts of the oil spill. In addition, post-exposure samples could also be compared to data collected over periods of decades preceding the oil spill to provide a deeper understanding of impacts.

2010 Biopsy-Map
Map of tissue sampling locations from health assessments and remote biopsy darting.

From 13 May through 12 October, 61 tissue samples were collected from dolphins through health assessment operations and remote biopsy sampling. Samples were collected with rigorous NOAA Natural Resource Damage Assessment (NRDA) protocols for chain of custody, and they have been provided to NOAA, where they will be analyzed with other samples collected from around the Gulf. Photographic identification surveys were performed through the 150 square mile Gulf study area as well as Sarasota Bay, where regular monthly surveys are conducted throughout the year. Thousands of identification photographs were obtained, and are currently going through photo-analysis.

Preliminary analyses suggest that there was no major influx or loss of dolphins from the Gulf waters or Sarasota Bay. Many of the dolphins documented from the Gulf waters already exist in our photo-identification catalog for the west coast of Florida, some with sighting histories extending back decades, reinforcing the idea of long-term residency in coastal waters outside of bays.

Fortunately, the oil did not reach Sarasota Bay. The samples and data collected will be used as control data in comparison with data from oiled areas in the northern Gulf, and they will be used for future comparisons to evaluate the possibility of more subtle, long-term ecological changes.

All photos © Sarasota Dolphin Research Program under NMFS permit #522-1785

Genetic analyses of social structure: Paternity and relatedness in Sarasota Bay

This project represents 25 years of genetic work on the Sarasota Bay bottlenose dolphin community. Over this time, we have brought a diverse array of genetic tools to the investigation of social structure in a well-known core population of dolphins. To date, we have developed DNA microsatellite panels from blood samples taken during capture-release efforts for 238 bottlenose dolphins of the Sarasota Bay community; 129 females and 109 males. Of the 238 dolphins sampled, 102 of these were calves born in the community to known mothers. Over the past two years we have also added 73 biopsy samples from dolphins sampled independent of the capture-release operations.

We are in the process of completing paternity exclusions for all the calves. Analyses have been completed for 71 of the calves and yield the following preliminary conclusions:

  1. 51 calves were sired by a male in the community.
  2. Four males sired from 3-5 calves each; five males sired at least two calves each.
  3. The most successful males were FB60, FB10, then FB46 and FB76.
  4. 20 calves (28%) were not sired by males in the community – as we have reported previously, the Sarasota Bay dolphin community is not a genetically isolated population.
Petey (FB10), one of Sarasota’s most successful sires.
Petey (FB10), one of Sarasota’s most successful sires.

We are currently engaged in finishing the paternity exclusions for the rest of the calves and completing the integration of the biopsy samples. In addition to helping us define the breeding structure of this community, these paternity assignments will allow us to correlate presence, behavior, morphology and health with breeding success.

To complete our understanding of the genetic and group structure of the Sarasota dolphin community, we are also particularly interested in defining the role of relatedness in observed social patterns. These data taken together with the paternity data will provide the basis for a comprehensive investigation of social unit structure in the Sarasota Bay dolphin community. In no other bottlenose dolphin community studied has it been possible to individually profile the entire community over five generations with both genetic analyses and long-term behavioral observations.

Genetic and contaminant sampling of mid-Sarasota Bay and new dolphins

Beginning in the mid-1990s there has been an unprecedented increase in the numbers of dolphins using Sarasota Bay, from a 20-year average of about 100-120 dolphins to more than 175 dolphins in the early 2000’s. Some of this increase was a result of recruitment through successful reproduction of long-term residents, but many of the animals appeared in the bay as juveniles or adults, originating elsewhere. Because these “newcomers” rarely enter waters shallow enough to support our standard capture-release techniques, we conduct biopsy darting to obtain genetic samples for examination of mitochondrial DNA haplotypes and microsatellites, and to determine sex as part of our long-term program of monitoring population structure. Blubber obtained from the biopsy darting is analyzed for organochlorine contaminant concentrations. In combination, genetic and contaminant profiles may provide indications of the origins of the animals, allowing evaluation of a previously-undocumented mechanism for variation in dolphin population structure.

Since 2003, 58 biopsy dart samples have been obtained from bottlenose dolphins that have not been previously handled during health assessments. Samples have been primarily collected from mid-Sarasota Bay but have extended from the Manatee River to Venice Inlet. Genetic analyses of these samples are currently being run by Dr. Debbie Duffield of Portland State University. Contaminant samples have been banked at the National Institute of Standards and Technology in Charleston, SC. In addition to the principal goal of collecting skin and blubber from previously unsampled individuals, over the years this project has trained a number of US and foreign researchers in the practice of biopsy sample collection and processing.

Assessing bottlenose dolphin health as an indicator of overall ecosystem health; an ongoing study in the Turtle/Brunswick River Estuary and Sapelo Island National Estuarine Research Reserve

For my dissertation, I am working with NOAA to compare bottlenose dolphin populations near EPA superfund sites in Georgia to those at a nearby national estuarine reserve. The Turtle/Brunswick River Estuary (TBRE) located in Glynn County, Georgia, includes the Turtle and Brunswick Rivers, St. Simons Sound, St. Simons Island, and Jekyll Island. The LCP Chemical manufacturing plant, to the west of the city of Brunswick, is currently on the National Priority List (NPL), a list of all toxic waste sites that are eligible for federal assistance toward clean-up.

The LCP Chemical NPL site covers approximately 550 acres of tidal marsh adjacent to the Turtle River and 15km upriver from St. Simons Sound. Over the past 70 years, LCP Chemical has operated an oil refinery, paint manufacturing plant, and chlor-alkali plant on this site. These industrial influences have resulted in high levels of mercury, polychlorinated biphenyls (PCBs), and semi-volatile contaminants within the soils, groundwater, and marsh biota surrounding the region. In addition to the LCP Chemical plant, three other NPL sites are in and around Brunswick; Terry Creek Dredge Spoil/Hercules Outfall, Hercules 009 Landfill, and Brunswick Wood Preserving. Hercules Inc., the company responsible for the Terry Creek Dredge Spoil/Hercules Outfall and Hercules 009 Landfill, manufactured an organochlorine pesticide known as toxaphene, from 1948-1980. The Terry Creek Dredge Spoil/Hercules Outfall is in close proximity to Dupree and Terry Creeks which empty into St. Simons Sound. High concentrations of toxaphene in all trophic levels surrounding this site have been identified.

LCP Chemical National Priority List Site
LCP Chemical National Priority List Site

In contrast to the TBRE, the Sapelo Island National Estuarine Research Reserve (SINERR), located approximately 30km northeast of Brunswick, encompasses the fourth largest and one of the most pristine barrier island systems along the Georgia coast. The SINERR is a part of the National Estuarine Research Reserve System (NERRS) and is a focus of long-term ecological research projects such as water quality monitoring, primary productivity assessment, and fisheries sampling. Thus, the TBRE and SINERR offer the opportunity to investigate polluted and relatively pristine field sites that are geographically adjacent to each other. NOAA and its partners have recently conducted a study, which included portions of the TBRE and SINERR, to assess indicators of ecosystem health including nutrient loads, pathogen indicators, water quality, sediment contaminants, and oyster tissue contaminants. As a complementary project, contaminant exposures of bottlenose dolphins are also being measured.

Sapelo Island Naitonal Esuarine Research Reserve
Sapelo Island Naitonal Esuarine Research Reserve

Bottlenose dolphins are long-lived, apex predators that bio-accumulate persistent organochlorine contaminants (POCs) in their lipid-rich blubber. Along the southeastern United States, many dolphin populations demonstrate high levels of site-fidelity to localized regions. Thus, the bottlenose dolphin has been identified as a sentinel of coastal ecosystem health. Bottlenose dolphins also forage on a variety of recreational and commercial marine species, suggesting they may also be an indicator for human health risks in a particular region.

Remote biopsy dart samples from bottlenose dolphins in both regions have been obtained and a subset of these samples has been analyzed to identify persistent organochlorine contaminants (POC), including 66 PCB congeners, 7 PBDE congeners and a number of organochlorine pesticides. Chemical analyses are being conducted at the Hollings Marine Laboratory by the National Institute of Standards and Technology (NIST) laboratory. Preliminary data suggest extremely high levels of PCBs in dolphins sampled from the TBRE. Surprisingly, relatively high levels of PCBs were also found in dolphins sampled from SINERR. However, without knowing the ranging patterns of the biopsy-sampled individual dolphins, the origin of these contaminants is currently unknown. For this reason, photo-identification research to investigate the distribution and movement patterns of dolphins along this area of the Georgia coast is essential.

This project will be the first to evaluate and compare seasonal abundance, site-fidelity, habitat utilization patterns, and contaminant specificity for bottlenose dolphins across two geographically adjacent, yet ecologically different regions of the Georgia coastline. Intensive seasonal mark-recapture surveys utilizing photo-identification of individuals’ dorsal fins will be used to determine bottlenose dolphin abundance in both regions. Comparing sighting histories for all identified individuals will provide site-fidelity indices (i.e. amount of time dolphins are spending within each of the two areas) throughout the course of the study. Strahler Stream Order, a quantitative technique used to classify estuarine habitats, will be used in combination with sighting distribution to characterize habitat utilization of bottlenose dolphins within and between the TBRE and SINERR field sites. In addition to remote biopsy dart samples from known dolphins, sighting histories will be used to identify fine-scale geographic contaminant specificity of bottlenose dolphins in both regions; are there contaminant congeners specific to the TBRE and SINERR regions? In addition, these results may also identify a pathway for contaminants in a salt marsh estuarine ecosystem; are dolphins absorbing these contaminants by traveling between the TBRE and SINERR regions, or are the contaminants reaching the dolphins in another way, such as dolphin prey traveling between regions?

Assessing ecosystem health requires a multi-faceted analysis of all trophic levels of an ecosystem. Prior studies have identified high levels of PCBs and other contaminants surrounding NPL sites in Brunswick. The biopsy dart samples from bottlenose dolphins in both the TBRE and SINERR have provided preliminary evidence for elevated levels of PCBs in bottlenose dolphins within both regions. However, there are still numerous questions left unanswered to identify the overall health of these two ecosystems. Identifying bottlenose dolphin abundance, site-fidelity, habitat use, and contaminant specificity for these regions is one method toward providing insight into bottlenose dolphin health and thus ecosystem health within the TBRE and SINERR.

This research would not be possible without funding from NOAA Fisheries Service, Georgia Department of Natural Resources, and Chicago Zoological Society.