Phenology of pelagic seabird abundance relative to marine climate change in the Alaska Gyre

Abstract

In relation to climate change, a common finding from long-term studies on marine ecosystems is earlier annual peaks of abundance for many organisms. Here, we test the hypothesis of unidirectional change in the seasonal abundance of pelagic seabirds in association with change in marine climate and primary productivity in the Alaska Gyre. To test this hypothesis, we analyzed data on hydrographic conditions and seasonal at-sea abundance of seabirds along a 1425 km transect (Line P) over 11 yr, 1996 to 2006. Long-term sea surface temperature (SST) data show warming in the study region, advanced and delayed temperature peaks and northwestward isotherm displacement. Using negative binomial regression, we tested seasonal trends in the relative abundance of 15 seabird species and compared abundances to a multivariate ocean climate index we developed with principal component analysis from in situ measurements of water temperature, salinity, density and nitrate concentrations. Overall, 5 species showed no change, 1 declined, and 9 species as well as all species combined showed increasing abundance. By season, 3 species increased in winter, 7 in late spring, and 6 in late summer. Eight of 15 species showed relationships with our environmental index. Increases in seasonal seabird abundance may be related to lengthening of the 'growing season', as demonstrated by temporal temperature shifts and expansion of peak chlorophyll concentrations. Seabirds of the Alaska Gyre are probably responding to changes in forage nekton that are related to this extended growing season by shifting their migration to later dates.

Revisiting the footprints of climate change in Arctic marine food webs: An assessment of knowledge gained since 2010

“…Phenological changes in lower trophic levels have effects on higher trophic levels. The prolonged growth season and the subsequent increase of primary and secondary production have had positive effects on 9 of 15 seabird species investigated near the sub-Arctic Alaska Gyre, while only one species declined in abundance (Thompson et al, 2012).…”

“…Ecological footprints of climate change are related to each other in manifold ways, for instance by sharing the same or similar drivers (single or multiple) or resulting in (or from) other footprints in a cascading-impact chain. For example, the increase in marine primary production has hadand very likely will have -cascading positive effects on the higher trophic levels of marine food webs, from zooplankton to seabirds and whales (Thompson et al, 2012;George et al, 2015;Waga et al, 2019).…”

Seabirds and climate change: roadmap for the future

“…However, as found in our meta-analysis, studies of seabird distribution and range shifts in relation to climate change were under-emphasized. Thompson et al (2012b), however, report on a related topic, namely seasonal variation in distribution and abundance of seabirds in the southeast Gulf of Alaska.…”

Effects of Climate Change and Fisheries Bycatch on Shy Albatross (Thalassarche cauta) in Southern Australia

“…We did not evaluate the impacts of the environment on all possible demographic elements however, breeding success is considered to have the strongest response to environmental conditions [ 6 , 68 ]. Future work could include relationships with adult and juvenile survival rates, at-sea distributions, timing of breeding, recruitment to the breeding colony, and the breeding success of inexperienced birds relative to those of experienced birds, all of which have been shown to respond to environmental variability in some seabirds [ 22 , 69 , 70 ].…”