Parasite component community of Gulf Killifish, Fundulus grandis, in an oiled Louisiana saltmarsh

Abstract

Fish parasites comprise a large portion of marine biodiversity but so far have been underutilized as Gulf of Mexico bioindicators. Shifts in parasite diversity, prevalence, and intensity resulting from the 2010 BP Deepwater Horizon Oil Spill (DHOS) could indicate spill-related changes to water quality, abundances and immunological health of free-living organisms, or the Gulf of Mexico food web. Ectoparasites with direct life cycles (no intermediate host or food-web mediated transmission) may be sentinels for acute spill effects, as they are typically small, have high surface area to volume ratios, and remain immersed in seawater. Endoparasites with indirect life cycles (intermediate host[s] required) involving food-web mediated transmission may be sentinels for detecting chronic spill effects, as they reside in a host where they are less vulnerable to toxins and have larvae requiring predator/prey transmission. To test these ideas, one must have a species-level understanding of the parasite component community in a geographic area. Chapter 1 enumerates the parasite component community of Gulf killifish, Fundulus grandis (Cyprinidontiformes: Fundulidae) in Barataria Bay, LA. Using those data as a critical baseline and for the units of analysis, Chapter 2 statistically tests for differences in the structure of the parasite component community across 4 oiled sites and 4 reference (non-oiled) sites in Barataria Bay. Regarding the survey and inventory of parasites, the parasite component community includes 44 species (31 endoparasites; 13 ectoparasites) infecting 23 fish tissues. Of these parasite species, 10 are putatively new to science, 24 constitute new host records to F. grandis, and nearly all, 42 of 44 (95%), are putatively new locality records in LA. Regarding the use of those taxonomic units to test hypotheses concerning ecosystem functioning, no significant differences were detected between prevalence (aggregated) of ectoparasites (Monogenoidea, Hirudinida, Copepoda, Branchiura, Isopoda) and endoparasites (Myxozoa, Digenea, Cestoda, Nematoda, Acanthocephala) in oiled and non-oiled sites nor in mean intensity and prevalence (aggregated) of ectoparasites and endoparasites in oiled and non-oiled sites. However, significant differences were detected in species prevalence of acanthocephalans (19.6% in non-oiled sites vs. 2.9% in oiled sites), copepods (21.7% vs. 34.2%), and branchiurans (13.8% vs. 28.3). Seasonal effects were statistically detected in myxozoans (highest intensity of infection during May 2011) and digeneans (highest intensity in August 2011), and those seasonal patterns were not significantly different between oiled and non-oiled sites. Digenean metacercariae infecting gill and heart, monogenoideans infecting skin, and nematodes infecting body cavity each have a significantly higher log mean intensity in oiled sites. Species richness of ectoparasites and endoparasites was not significantly different between oiled and non-oiled sites and across seasons. Condition factor of F. grandis was not significantly different between oiled and non-oiled sites and across seasons.