I would like to recognize my co authors on this program Irv - PDF document

I would like to recognize my co ‐ authors on this program – Irv Mendelssohn, Qianxin Lin, Aixin Hou, and John Fleeger from Louisiana State University studying different aspects of this program. Stefan Bourgoin from Atkins has been my partner on the study of the macroinvertebrate communities. 1

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As a team, we are studying the plant ‐ microbial ‐ benthic ecosystem of the marsh edge and the impact of the oil spill on that system. This system is responsible for building the marsh surface elevation and controlling oil degradation, surface erosion, soil nutrient cycling, and is the base of the marsh food chain, both grazing and detrital. An oil spill can upset this balance and exacerbate wetland loss. There are several studies on the initial impacts of this and other spills on coastal wetlands; however there is little information on the long ‐ term impacts and recovery of these systems. We began this particular study 30 months after the Deepwater Horizon Oil Spill (November 2012). There was evidence of the spill still obvious at the heavily oiled stations with bare marsh sediment platforms and residual oil crust. The vegetation is beginning to visually recover. The overall goals of this program are to (1) document longer ‐ term impacts of the oil spill on the plant ‐ microbial ‐ benthic system; (2) quantify rates of, and controls on, the system recovery; and (3) evaluate the effectiveness of remediation techniques for accelerating recovery and long ‐ term sustainability of the system. 3

Initially, the program has included the continued sampling of 21 stations; 7 each representing various oiling levels based upon SCAT data, field observations, and initial Total Petroleum Hydrocarbon (TPH) sampling data from the sites. The sampling has occurred from November 2012 to October 2014 at intervals of 30, 36, 41, 43, 48 and 54 months after spill. Qianxin Lin and his team has been responsible for collecting TPH samples, aboveground biomass and stem density (total, live, dead) for Spartina alterniflora, and Juncus roemerianus , belowground Biomass (total at 0 – 6cm and 6 – 12cm). They are also responsible the soil parameters – soil shear strength and soil accretion. Plant Parameters Aboveground Biomass and Stem Density (Total, Live, Dead, Spartina, and Juncus ) Belowground Biomass (Total, 0 – 6cm, 6 – 12cm) Soil Parameters Soil Shear Strength Soil Accretion Organisms Soil Bacteria Benthic Microalgae Benthic Meiofauna Macroinvertebrates ( Uca spp. and Littoraria irrorata ) Aixin Hou has been analyzing the soil bacteria. John Fleeger has been working on the benthic microalgae and benthic meiofauna. Stefan Bourgoin and I have responsible for collecting and analyzing data on the fiddler crab ( Uca spp.) and periwinkle snail ( Littoraria irrorata ). 4

The field study was carried out in coastal salt marshes in and around Bay Jimmy in northern Barataria Bay, Louisiana, one of the most severely oiled coastal marsh regions, covering a sampling area of about 8 km x 5 km. Seven field stations (replicates) were randomly selected from a larger population that received heavy, moderate and reference (non ‐ oiled) marshes based on SCAT data and earlier field observations, resulting in a total of 21 field stations. These stations were established in early January 2011, about 7 months after the oil spill. Surface oil samples were collected and analyzed for TPH. Plant above ground biomass (live and dead) and stem density were analyzed. Lin et al. (2012 and in press) contains early data and analysis from these stations 7, 9, 18, and 24 months after the spill. Fleeger et.al. (in press) contains early data at these stations on the benthic microalgae and benthic meiofauna 18 and 24 months after the oil spill. 5

Our sampling focused on two sentinel macroinvertebrate specie groups in the marsh – fiddler crabs, Uca spp. and the marsh periwinkle ( Littoraria irrorata ). Fiddler crabs are one of the most abundant and conspicuous macroinvertebrates in most salt marshes making them an appropriate organism to study relative to marsh faunal injury. They are one of the most thoroughly studied shore crab in North America. Fiddler crab literature is quite robust, examining individual species population dynamics, life history and ecology. Fiddler crabs greatly influence the marsh through burrowing and feeding activities, e.g. enhancing effects on vegetation productivity and biomass, sediment and nutrient characteristics, biogeochemical cycles, microbial processes by aerating the marsh sediment, increasing soil drainage, and facilitating nutrient transport. Generally, the presence of fiddler crabs has been noted as indicating greater diversity of other marsh organisms and crab population densities can reflect the productivity of a wetland. Fiddler crabs have been shown to be sensitive to oil spills making them a valuable environmental indicator. Fiddler crab burrowing can also influence oil behavior. The burrows can serve as a source of secondary porosity, allowing oil to penetrate marsh sediments, in some cases leading to longer term sediment contamination. As indicated, they can influence sediment aeration and flooding, enhancing the degradation of oil in the sediment. Oil degradation and soil stability could also be enhanced indirectly where crab burrowing increases plant productivity and above and below ground biomass. Various fiddler crab species inhabit the northern Gulf of Mexico coast. Two species, in particular, are found in the Louisiana marshes. Uca spinicarpa prefers clayey substrates in brackish marshes ranging from nearly fresh to hypersaline. Uca longisignalis is restricted to sediments of terrigeneous origin ((i.e. mucky soils) and found primarily in lower salinity (upper estuaries). The two species can be found in close proximity but have preferred habitats based on elevation, vegetation and sediment character. The marsh periwinkle is also a common and conspicuous organisms in coastal salt marshes and is also an indicator species of the health of the salt marsh habitat. The most abundant periwinkle in the salt marshes of Louisiana is Littoraria irrorata . In areas dominated by short to intermediate form Spartina alterniflora , the species has been noted to occur in densities of at least 100 individuals/m 2 . Periwinkles are rasping detritivore/herbivore specialists, feeding on organic matter on the marsh surface during low tide and ascending the Spartina stems to feed upon standing ‐ dead Spartina and its associated microbial assemblages. As a detritivore, L. irrorata influences nutrient dynamics by expediting the decomposition of Spartina alterniflora and serves as an important link between primary and secondary The presence of Spartina alterniflora is directly liked to increased abundance, growth and survival of L. irrorata in “natural” marshes. Both fiddler crabs and marsh periwinkles can be severely impacted by oil spills, including direct mortality, reduced population densities, and sublethal effects. Recovery time following impacts for these organisms can vary substantially based on a variety of oiling and habitat conditions, from a year to several decades. 6

We are going to look at this data more closely, but in general, we have not seen a lot of difference in the fiddler crab burrow density between the treatments over time. The fiddler crabs tend to burrow in open areas within the marsh and, once the oil crust begins to dissipate in the nearshore area, the fiddler crabs will burrow in those areas. There was a short term shift in Uca species noted by Zengel et al. (2014) with Uca spinicarpa occupying some oiled areas in his study area. When we started our studies 30 months after the spill, all species collected have been Uca longisignalis . Note that the average number of burrows per m 2 is low, 10 and less. 7

This is data 6 months after the spill (October 2012) representing early impact data. Note that the crab burrow density is low (10 or so per m 2 ). This is approximately the same level that we are seeing in our study (10 or less burrows per m 2 ). These data were collected at 3 sites approximately 3 m from the shoreline. 8

Another set of early samples. These stations were located 1 ‐ 2 meter behind the oiled zone, so they represent areas deeper into the marsh where burrow density is typically higher. These were also in areas of “apparently healthy” vegetation. And a very light substrate oiling (sheen). This study shows early impacts at minimal oiling levels. McCall and Pennings (2012) sampled a wider geographic area than Silliman (2012). This may have been part of the reason for the higher burrow density. Mouton and Felder (1996) noted the variation in density of U. longisignalis along a 15 ‐ m transect. The burrow density was lowest near the water’s edge and highest in the middle to middle ‐ upper reaches of the transect. No marked change in elevation was noted beyond about 3 m from the water’s edge. 9

This study provides data on burrow densities after the spill in a period between the Silliman et al. (2012) study and our study. This study found that there were difference in burrow density in the first year with no treatment, but no differences between the treated areas and the reference. No differences were found with any of the areas in Year 2. So it is not surprising that we do not find differences starting at 30 months after the spill. Note that these burrow density are slightly higher, but in the range of those that we are finding at our study sites. 10