The relationship between dietary trophic level, parasites and the microbiome of Pacific walrus ( Odobenus rosmarus divergens )

Abstract

Arctic species are likely to experience rapid shifts in prey availability under climate change, which may alter their exposure to microbes and parasites. Here, we describe fecal bacterial and macroparasite communities and assess correlations with diet trophic level in Pacific walruses harvested during subsistence hunts by members of the Native Villages of Gambell and Savoonga on St Lawrence Island, Alaska. Fecal bacterial communities were dominated by relatively few taxa, mostly belonging to phyla Fusobacteriota and Firmicutes. Members of parasite-associated phyla Nematoda, Acanthocephala and Platyhelminthes were prevalent in our study population. We hypothesized that high versus low prey trophic level (e.g. fish versus bivalves) would result in different gut bacterial and macroparasite communities. We found that bacterial community structure correlated to diet, with nine clades enriched in walruses consuming higher-trophic-level prey. While no parasite compositional differences were found at the phylum level, the cestode genus Diphyllobothrium was more prevalent and abundant in walruses consuming higher-trophic-level prey, probably because fish are the intermediate hosts for this genus. This study suggests that diet is important for structuring both parasite and microbial communities of this culturally and ecologically important species, with potential implications for population health under climate change.

The gills and skin microbiota of five pelagic fish species from the Atlantic Ocean

“…Considering the high number of wild sh species and the importance of sh biomass in the ocean's animal biomass (Bar-On et al 2018), the taxonomic and functional microbiome diversity of the various sh tissue/organs remains practically untapped. This could be attributed to the multiple and ample challenges in wildlife microbiome studies, for which the frequently considered descriptive and exploratory work of microbiota pro ling is considered the rst major advancement and the rst hypothesis-generating step towards the understanding of host-microbiome ecology in wild animal species, especially in body sites other than the gastrointestinal tract (Couch et al 2022), such as the skin and gills in sh.…”

Multi‐decadal trends in biomarkers in harp seal teeth from the North Atlantic reveal the influence of prey availability on seal trophic position

“…Trophic position, reflecting the trophic ecology of predators, is also utilised in population dynamic studies, as body condition and reproduction of marine predators are linked to their diet (Arnould et al, 2011; Øigård et al, 2013; Ronconi et al, 2014). In addition, trophic position is one of the key drivers of contaminant burdens (Borgå et al, 2004; Braune et al, 2015; Brown et al, 2016; Carravieri et al, 2014) and trophically derived parasite loads (Couch et al, 2022; Vestbo et al, 2019) in predators. It is therefore crucial to accurately detect decadal changes in trophic position of marine predators in order to understand how food webs are being reshaped and the consequences of these modifications on population dynamics and contaminant bioaccumulation, which could, in turn, be used in ecosystem‐based management.…”

Comparative Microbial Community Analysis of Fur Seals and Aquaculture Salmon Gut Microbiomes in Tasmania

“…Metacommunity analysis utilizes the knowledge of the diversity of species and changes in community structures to elucidate the extent of interactions within and between species assemblages, including microbial communities found in nature [16,[24][25][26][27]. Comparing full microbial communities using microbiome analysis between geographic regions and trophic levels as a way of analyzing bacterial movements is an up-and-coming field of research [23,28,29]. Such work at the interface between wild fur seals, aquaculture, and human development would be very useful in laying the groundwork for biocontamination monitoring and management.…”