Marine Heat Wave Increased Variance and Decreased Productivity at Bering Strait during 2015–2016 ^†

Planktivorous auklets registered changes across two years of a marine heat wave (2015–2016). Colony attendance of crested auklets (Aethia cristatella) was reduced (35–50%) at Little Diomede I., AK, in the latter part of June 2016 compared to 2015. The pattern was similar for least auklets (A. pusilla). An anomalous marine distribution and anomalous consumption pattern were noted for crested auklets. A plot of δ¹⁵N/δ¹³C spanned three times the range in 2016 vs. 2015. Crested auklet RBC’s had lower δ¹³C values and higher δ¹⁵N in 2016. Least auklet growing primaries showed the same pattern. Advected production is important, but δ¹³C enrichment may have occurred later in 2016. Julian Date of sampling was more strongly correlated with δ¹³C of crested auklet RBCs in 2016 (r = 0.47, p < 0.001) than in 2015 (r = 0.31, p = 0.01). Crested auklets had higher baseline corticosterone (t_0.05(2)27 = 2.56, p < 0.05) and higher variances in 2016. The crested auklet’s citrus-like odorant was less evident in 2016 and ceased earlier in the summer. Bill pigmentation was incomplete in 11% of crested auklets (n = 82) in 2016. Planktivorous auklets are proxies for the marine ecosystem. Increased marine heat content may have imposed additive costs that decreased productivity of some top predators.