Global phytoplankton decline over the past century

Abstract

In the oceans, ubiquitous microscopic phototrophs (phytoplankton) account for approximately half the production of organic matter on Earth. Analyses of satellite-derived phytoplankton concentration (available since 1979) have suggested decadal-scale fluctuations linked to climate forcing, but the length of this record is insufficient to resolve longer-term trends. Here we combine available ocean transparency measurements and in situ chlorophyll observations to estimate the time dependence of phytoplankton biomass at local, regional and global scales since 1899. We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of approximately 1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures. We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries.

Spring phenological responses of marine and freshwater plankton to changing temperature and light conditions

“…While climate-related phenological shifts toward earlier spring events are widespread across marine and freshwater habitats (Thackeray et al 2010), there is less consensus on bloom magnitude (Adrian et al 1999;Boyce et al 2010;Straile 2002;Taucher and Oschlies 2011). Our analysis confirms the general shift toward earlier blooms at increased temperature and supports predictions that the effects of climate change on plankton production will vary among sites, depending on resource limitation and species composition.…”

Implication of our technological species being first and early

“…One imaginable (if oversimplified) example of a biosphere extinction scenario is the depletion of atmospheric oxygen caused by the loss of photosynthesis in ocean phytoplankton and rain forests, possibly accelerated by rising global temperatures. Such a process may already be in progress (Boyce et al 2010;Roxy et al 2016). The (complete) extinction of aerobic life would reset the evolutionary clock back to the time photosynthetic oxygen first appeared in the atmosphere &2.5 Gyr ago, leaving insufficient time for the evolution of another technological species.…”

Influence of Basin‐ and Local‐Scale Environmental Conditions on Nearshore Production in the Northeast Pacific Ocean

“…Growth of California Current rockfish was related to the PDO at the basin scale and to SST, SSHa, and freshwater discharge at the local scale. In the California Current, cooler conditions NORTHEAST PACIFIC NEARSHORE PRODUCTION were previously linked to increases in pelagic production, including rockfish growth (Lenarz et al 1995;Black 2009), rockfish condition (Lenarz and Wyllie Echeverria 1986), salmon catch (Hare et al 1999), reproductive success of the common murre Uria aalge (Gladics et al 2015) and Cassin's auklet Ptychoramphus aleuticus Wolf et al 2009), forage fish abundance (Sydeman et al 2013), zooplankton biomass and species composition (Peterson and Schwing 2003;Keister et al 2011;Di Lorenzo et al 2013), and chlorophyll-a concentrations (Harris et al 2009;Boyce et al 2010). These previous results are consistent with our findings.…”

“…Cooler conditions and decreased water column stability associated with coastal upwelling indicate greater vertical mixing and nutrient availability to primary producers in the California Current (Chavez and Messié 2009;Demarcq 2009). Increases in nutrient availability cause bottom-up increases in phytoplankton and zooplankton abundances and subsequent increases in forage fish consumption (Peterson and Schwing 2003;Harris et al 2009;Boyce et al 2010;Keister et al 2011), condition (Astthorsson and Gislason 1998;Robards et al 2002;Takahashi et al 2012), and abundance (Hedd et al 2006;Thayer et al 2008;Sydeman et al 2013). Furthermore, cooler conditions can prompt favorable shifts in prey composition (Hedd et al 2006;Mackas et al 2007;Thayer et al 2008;Keister et al 2011;Gladics et al 2015).…”