COS 267-2 - Dark waters of SGang Gwaay: limnological changes uncover a history of avian activity, invasive species, human settlement, and climate change over millennia

Background/Question/Methods

The Rhinoceros Auklet (Cerorhinca monocerata) is a puffin-like bird that breeds on forested and grassy islands scattered in the North Pacific, but otherwise lives at sea. The majority (~73%) of the global population is on the islands of Haida Gwaii, BC (Canada). In the past millennia, the species’ habitat has changed significantly; ocean temperatures have shifted, and brush cover has been modified by invasive Sitka black-tailed deer (Odocoileus hemionus sitkensis) and human activities (e.g., logging). The species’ behavior and multiple stressors make it difficult to understand current population trends. Furthermore, the most recent comprehensive survey only dates to 1985 and population responses to stressors cannot be untangled. The Rhinoceros Auklet colony on SGang Gwaay, an island in Haida Gwaii, BC is located in proximity to a pond as well as the former settlement at Ninstints. Sediment cores collected from this pond offer a window onto past avian activity as it relates to the island’s history. Using a multi-proxy approach, we are reconstructing the Rhinoceros Auklet colony of SGang Gwaay over ~1300 years.

Results/Conclusions

Sediment chlorophyll a profiles, inferred using visible range spectroscopy (VRS), suggest an increase in primary production at 314 years BP (26.25 cm). Additionally, the inferred lake-water total organic carbon concentration decreases at the same core depth. Preliminary results of diatom assemblages show that acidophilic species such as Eunotia incisa become the most abundant at depth of 28.0 cm indicating possible acidification of lake water from increases in bird fecal inputs. Stable nitrogen isotopes, fecal sterol and stanols, and diatom assemblages will help untangle whether the increase in primary production is induced by seabird nutrient inputs and/or climatic change. Future research will additionally examine the use of fecal stanols and eDNA for tracking relationships between human settlement, invasive species, and population fluctuations in Rhinoceros Auklets on SGang Gwaay.