Wed, Aug 17, 2022: 8:30 AM-8:45 AM
512E
Background/Question/MethodsPrecipitation is a master variable that drives stream ecosystem structure and function by controlling hydrologic variability and predictability and influencing riparian vegetation. We know little how spatial variation in rainfall drives community secondary production, a key component of energy flow. We collected macroinvertebrates and fishes in standardized reaches of nine coastal streams across a steep rainfall gradient (54 to 94 cm yr-1) in south Texas throughout 2020. We estimated annual secondary production and biomass using appropriate methods for each taxon.
Results/ConclusionsStreams differed considerably in both annual biomass and secondary production. As expected, most (72–95%) of the production was driven by fast growing invertebrate taxa including chironomids and oligochaetes. We found that both annual fish production and annual invertebrate standing stocks declined with increasing annual rainfall. For example, fish annual production averaged 1.8 ± 1.5 (SD) g AFDM m-2 yr-1 across sites, and our linear model predicted an average change in 2.4 g AFDM m-2 yr-1 across the 40 cm yr-1 rainfall gradient. Difference in community composition rather than species-specific shifts in turnover rates across the gradient drove the patterns we observed in production and biomass. Many stream ecosystems are vulnerable to fluctuations in hydrology, which will be altered by future shifts in precipitation patterns associated with climate change. Our work indicates that these changes in rainfall patterns may drive regime shifts and energy flow patterns of aquatic food webs.
Results/ConclusionsStreams differed considerably in both annual biomass and secondary production. As expected, most (72–95%) of the production was driven by fast growing invertebrate taxa including chironomids and oligochaetes. We found that both annual fish production and annual invertebrate standing stocks declined with increasing annual rainfall. For example, fish annual production averaged 1.8 ± 1.5 (SD) g AFDM m-2 yr-1 across sites, and our linear model predicted an average change in 2.4 g AFDM m-2 yr-1 across the 40 cm yr-1 rainfall gradient. Difference in community composition rather than species-specific shifts in turnover rates across the gradient drove the patterns we observed in production and biomass. Many stream ecosystems are vulnerable to fluctuations in hydrology, which will be altered by future shifts in precipitation patterns associated with climate change. Our work indicates that these changes in rainfall patterns may drive regime shifts and energy flow patterns of aquatic food webs.