Phytoplankton as indicators of global warming?

Abstract Terrestrial plants are sensitive indicators of global warming because their annual cycles growth and senescence changing as proceeds. Single celled algae distinct life forms capable population bursts in any season, so there is uncertainty about phytoplankton phenology a comparable indicator warming. We analyzed 4+ decades monthly chlorophyll measurements at two sites San Francisco Bay found abrupt shifts during summer months leading to 48‐day advance the pattern chlorophyll‐a accumulation one site 36‐day delay other. These large phenological changes were not associated with temperature, but they top–down control by bivalve filter feeders biological communities restructured (1) introduction non‐native clam, (2) shift atmospheric forcing NE Pacific. This study illustrates that necessarily responses or However, can be human disturbances natural climate oscillations having effects enough mask effect