Science Focus: Long Term Ecological Research


Network of LTER sites throughout the world.

The Long Term Ecological Research (LTER) Network is a collection of 26 sites throughout the United States and its territories, plus Antarctica and Tahiti. Studies spanning decades provide insight into environmental changes over seasons and years across a variety of habitats. In 2004, the California Current Ecosystem (CCE) site was added to the network, with scientists collecting seawater samples on CalCOFI cruises. 

Chlorophyll samples are analyzed onboard, both from CTD niskin bottles and using the ALF (Automated Laser Fluorometry) system, which pumps surface seawater continuously. On roughly half of the science stations, size fractionations for chlorophyll-a are determined using 5 filters of different pore sizes, from 0.7 to 20 microns. The size of phytoplankton particles has a complicated, non-linear relationship to total phytoplankton and this ratio indicates the health and sustainability of the entire food web. 


Volunteers Hanna and Joel sample water from CTD niskin bottles.

Many other samples are collected and analyzed in labs back on shore, including for TOC (total organic carbon), POC (particulate organic carbon), pigments via flow cytometry and HPLC (High Performance Liquid Chromatography), and bacterial elements. Information ranging from phytoplankton distribution and growth to currents and upwelling are added into the global LTER database, as well as the CalCOFI dataset.



Hanna carefully removes the filter after 2 liters of seawater
have passed through it.

Out at sea, scientists and volunteers collect water samples from the CTD casts on every station. Work shifts are spread out and overlapping, so that there are always at least two people awake to sample. Some of the analyses require the water itself, in which case it is stored and brought back to the lab. In other cases, the water is pumped through a filter, and that filter, with the particles collected on it, gets analyzed. 

Onboard R/V Sally Ride, the LTER work is done in a lab van located on the back deck. Directly after sampling the CTD, the bottles of seawater are taken back to the van. A filtration rig, made up of plywood and PVC, allows for processing of multiple samples at a time. The volunteers, Hanna, Joel, and CC, set up the filtrations and preserve the sample for later analysis. 

Long term, interdisciplinary research projects are key to learning how and why the environment changes. CalCOFI and LTER-CCE are two preeminent studies providing invaluable information about the ocean off California’s coastline, one of the richest and most dynamic ecosystems on Earth.