Protein Recycling in Bering Sea Algal Incubations

• Published in: Marine Ecology Progress Series
• Main Authors: Moore, Eli K., Harvey, H. Rodger, Faux, Jessica F., Goodlett, David R., Nunn, Brook L.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: ODU Digital Commons 2014
• Subjects: protein recycling; Bering Sea; Amino acid; Nitrogen cycle; Tandem mass spectrometry; Diatom; Cell death; Preservation; Ecology and Evolutionary Biology; Environmental Sciences; Oceanography
• Online Access: https://digitalcommons.odu.edu/oeas_fac_pubs/264; https://doi.org/10.3354/meps10936; https://digitalcommons.odu.edu/context/oeas_fac_pubs/article/1276/viewcontent/Harvey_protein.pdf

Protein present in phytoplankton represents a large fraction of the organic nitrogen and carbon transported from its synthesis in surface waters to marine sediments. Yet relatively little is known about the longevity of identifiable protein in situ, or the potential modifications to proteins that occur during bloom termination, protein recycling and degradation. To address this knowledge gap, diatom-dominated phytoplankton was collected during the Bering Sea spring blooms of 2009 and 2010, and incubated under darkness in separate shipboard degradation experiments spanning 11 and 53 d, respectively. In each experiment, the protein distribution was monited over time using shotgun proteomics, along with total hydrolyzable amino acids (THAAs), total protein, particulate organic carbon (POC) and nitrogen (PN), and bacterial cell abundance. Identifiable proteins, total protein and THAAs were rapidly lost during the first 5 d of enclosure in darkness in both incubations. Thereafter the loss rate was slower, and it declined further after 22 d. The initial loss of identifiable biosynthetic, glycolysis, metabolism and translation proteins after 12 h may represent shutdown of cellular activity among algal cells. Additional peptides with glycan modifications were identified in early incubation time points, suggesting that such protein modifications could be used as a marker for internal recycling processes and possibly cell death. Protein recycling was not uniform, with a subset of algal proteins including fucoxanthin chlorophyll binding proteins and RuBisCO identified after 53 d of degradation. Non-metric multidimensional scaling was used to compare the incubations with previous environmental results. The results confirmed recent observations that some fraction of algal proteins can survive water column recycling and undergo transport to marine sediments, thus contributing organic nitrogen to the benthos.