Metabolomics identifies tissue-specific trends in butter clams (Saxidomus gigantea) across a subarctic fjord-type estuarine system.

Across the Circumpolar North, harvesting of marine shellfish resources is vital for continued subsistence, recreational, and commercial lifestyles. However, estuarine and intertidal systems of Southcentral Alaska experience landscape-scale challenges due to variable physical characteristics, freshwater discharge, water quality, food availability, and nutritional quality. Additionally, findings in more temperate environments may not be entirely applicable to the subarctic. The continued sustainability of this resource depends largely on our ability to understand and adapt to environmental challenges as they occur, requiring an integrated understanding of marine species' physiological states and the geographic conditions under which they subsist. This study applied a metabolomics approach to benthic clams for characterizing metabolite trends and identifying biomarkers reflecting hydrographic landscapes across a subarctic fjord-type marine ecosystem, Kachemak Bay, Alaska. Butter clams (Saxidomus gigantea) were collected at three sites during the spring season and segmented into tissue types: posterior adductor muscle, gill, mantle, siphon, and visceral mass. Results revealed tissue-specific divergence in metabolite profiles, which were driven by a hydrographic gradient along oceanic to more estuarine conditions. The more oceanic site of Jakolof Bay revealed lower levels in most metabolites in gill tissues, including amino acids and osmoregulators, coupled with increases in most metabolites in mantle, siphon, and visceral mass tissues. We show metabolite trends are highly tissue-specific and suggest future studies need to involve compartmentalization of tissues. Thus, metabolomics provides an unprecedented opportunity to map the phenotypes of these organisms across landscape types as environmental conditions change. This study establishes a baseline for deeper investigations involving detailed environmental co-variation with metabolic health of shellfish resources across the subarctic.