Impacts of Large-Scale Climate Patterns and Localized Disturbance Events on Primary Production in an Aridland River
Abstract
Aridland rivers are highly susceptible to anthropogenic impacts and changing climatic conditions. In the southwestern U.S., these systems are characterized by long duration high flows during late-spring snowmelt and short duration pulses of flow from high intensity monsoons in the summer from headwater and urban sources. However, knowledge of the influence of seasonally predictable flow disturbances on gross primary production (GPP), an in-stream source of organic matter, in aridland systems is limited. We assessed the impact of these two types of flow disturbances on GPP from summer to fall (June - October), using time-series data from an approximately ten-year period at one site on the Rio Grande, New Mexico. In June across years, monthly mean GPP and monthly mean discharge (Q) were inversely related (r2=0.56, p=0.021) with significantly lower GPP rates occurring during El Niño years (i.e., high snowmelt) and higher values in La Niña years (i.e., low snowmelt) (p=0.028). Variable flow regimes across years, mainly from snowmelt, resulted in substantial differences in cumulative GPP from June through October (80 to 232 gO2/m). Threshold responses in daily GPP occurred during different times of the year from two non-related types of disturbances: increasing snowmelt discharge, and elevated turbidity from monsoons. In June, daily GPP rates were less than 2 gO2m-2d-1 when Q exceeded 40 m3/s, while in July and August daily GPP was less than 1 gO2m-2d-1 when turbidity exceeded 1,000 NTU at Qs below the 40 m3/s threshold. We show that the timing and magnitude of disturbances shape temporal patterns and algal biomass accrual with threshold responses in GPP likely from the physical abrasion caused by scour and light limitation. The dynamic responses of GPP to snowmelt discharge and the turbidity pulses from summer monsoons offers insight on ecosystem resilience to large-scale climate patterns and local disturbances in aridland rivers.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMH207...06S
- Keywords:
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- 1807 Climate impacts;
- HYDROLOGY;
- 1813 Eco-hydrology;
- HYDROLOGY;
- 1833 Hydroclimatology;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY