01-05 December 2025
INCOIS, Hyderabad, India.
| Abstract Submission No. | ABS-04-0064 |
| Title of Abstract | Unexpected temperature trends in plankton growth and grazing along a 110°E transect in the eastern Indian Ocean |
| Authors | Michael R. Landry*, Raleigh R. Hood, Claire H. Davies, Karen E. Selph, Lynnath E. Beckley |
| Organisation | Scripps Institution of Oceanography, UCSD |
| Address | Scripps Institution of Oceanogcaphy, University of California, San Diego La Jolla, CA, United States Pincode: 92131 E-mail: mlandry@ucsd.edu |
| Country | United States |
| Presentation | Oral |
| Abstract | With mid- to low-latitude waters of the Indian Ocean (IO) warming faster than other major oceans, many questions can be raised about the potential impacts of increasing temperature on IO productivity and food webs. Most models predict a significant decline in intermediate consumers like zooplankton due to the combined effects of reduced nutrient input, enhanced metabolism, and phytoplankton size shifts that reduce availability to larger gragers. On R/V Investigator cruise IN2019V03 (May-June 2019), we investigated phytoplankton production, growth and grazing processes along the historic IIOE 110°E transect from 39.5 to 11.5°S in the eastern IO. Stations spanned a 14°C gradient in mean euphotic zone temperature from temperate and subtropical to tropical water masses. Production and grazing were strongly coupled over the transect and balanced on average. Increasing growth conditions (light and temperature) were mainly manifest as more rapid biomass turnover and mesozooplankton biomass accumulation, which was elevated by 3 fold in the warmest tropical waters. Biomass-normalized grazing of mesozooplankton also increased 6 fold over the transect, showing a strong temperature relationship (r2 = 0.87) that exceeded expected temperature effects on gut turnover and metabolic rates. Such results are explained by recent findings of enhanced food web efficiencies due to widespread mixotrophy and appendicularian-facilitated grazing pathways in the tropical water mass. Our results highlight the importance of using natural gradients of adapted complex communities like the eastern IO as natural laboratories for observation and hypothesis testing relating to the likely directions of climate change impacts. |
| Are you part of IIOE-2 endorsed project | yes |
| Endorsed Project Number | IIOE2-EP06 |
| Keywords | climate change, zooplankton, growth, grazing, food web efficiency |
| For Awards | no |