Re ECF Project: 2012-16

Project Title: Can stream drift be used to monitor climate change? Development of a protocol for assessing the effects of temperature rise on biodiversity in Hong Kong streams

Applicant: Professor David Dudgeon, School of Biological Sciences, The University of Hong Kong

Total Approved Grant: $464,500 (ECF & WWGF: 50/50)

Duration: 15/3/2014 to 14/9/2016

Project Status/Remarks: Completed

Freshwater animals are known to be sensitive to climatic warming. Annual mean temperatures in Hong Kong have increased by 0.7oC over the last 30 years. This project aims to compare the assemblage composition of stream invertebrates collected in 1983 with new samples (obtained using the same methods) made in 2013 and 2014, with a view to assessing the magnitude of both long-term (1983 vs 2013/14) and short-term (2013 vs 2014) changes in biodiversity. The results will be used to devise a protocol for long-term annual monitoring of stream biodiversity.

Summary of the Findings/Outcomes:
Macroinvertebrate drift samples were collected from Tai Po Kau Forest Stream on 64 dates between 2013 and 2016, yielding a database of >84,500 records (all insects) comprising 102 species. The project team compared drift composition in these three years (2013-16) with samples from one year (1983-84) three decades earlier in search of a long-term signal of environmental change, particularly climate warming. Drift dynamics showed strong seasonality in all years, with species richness and abundance declining during the cooler months. Half of the most numerous species showed significant seasonal (within-year) sensitivity to temperature. The blackfly Eusimulium (top-ranked in abundance: 13% of total individuals) were more numerous during cooler months; other species, such as the baetid mayfly Baetiella trispinata showed the opposite trend. The baetid Liebebiella vera exhibited consistent and strong within-year cycles correlated with temperature, but underwent a long-term decline in abundance (16% of individuals in 1983-84; <2% in 2013-16). This reduction in a dominant species, and lesser declines in some other baetids, was the major difference between historic and contemporary drift samples. Other shifts, largely represented by increases in Eusimulium and Anisocentropus maculatus caddisflies, were minor. Diversity and overall species richness did not alter, and the signal of environmental change was weak.