Monsoon oscillations regulate fertility of the Red Sea

Abstract

Tropical ocean ecosystems are predicted to become warmer, more saline, and less fertile in a future Earth. The Red Sea, one of the warmest and most saline environments in the world, may afford insights into the function of the tropical ocean ecosystem in a changing planet. We show that the concentration of chlorophyll and the duration of the phytoplankton growing season in the Red Sea are controlled by the strength of the winter Arabian monsoon (through horizontal advection of fertile waters from the Indian Ocean). Furthermore, and contrary to expectation, in the last decade (1998-2010) the winter Red Sea phytoplankton biomass has increased by 75% during prolonged positive phases of the Multivariate El Niño-Southern Oscillation Index. A new mechanism is reported, revealing the synergy of monsoon and climate in regulating Red Sea greenness.

Synergistic Use of Remote Sensing and Modeling to Assess an Anomalously High Chlorophyll-a Event during Summer 2015 in the South Central Red Sea

“…Other authors have investigated the (instantaneous) monthly correlation between various geophysical variables and Chl-a in the Red Sea [31,68]. However, Figure 8 is suggestive of a strong lag correlation of two months between DAOD anomalies and Chl-a anomalies and SST anomalies and Chl-a anomalies for the SCRS.…”

Nutrient Limitation in Central Red Sea Mangroves

“…Unlike the coverage of mangroves in other regions, the area covered by mangroves in the Red Sea remains relatively stable (Almahasheer et al, 2016a). Nutrient inputs to the Red Sea are dominated by inputs from the Indian Ocean (Murray and Johns, 1997;Johns and Sofianos, 2012;Churchill et al, 2014;Raitsos et al, 2015), leading to a gradient of oligotrophication toward the north (Ismael, 2015), concurrent with an increase in salinity due to high evaporation losses (Talley, 2002). On the other hand, the sea surface temperature declines from south to north (Rushdi, 2015).…”

“…In the absence of rivers and negligible precipitation, such as in the Red Sea, nutrient inputs from the Indian Ocean (Murray and Johns, 1997;Johns and Sofianos, 2012;Churchill et al, 2014;Raitsos et al, 2015), sub-surface mixing (Triantafyllou et al, 2014;Yao et al, 2014), and atmospheric sources are likely to be the most significant path for new nutrient input (Brindley et al, 2015), including nitrogen fixation and inputs of phosphorus and iron with dust deposition (Aerts and Chapin, 1999;Schroth et al, 2009). The Red Sea receives one of the highest dust inputs of all the oceans (Jish Prakash et al, 2015), and mangrove canopies may intercept dust during periods of dust storms, thereby increasing iron supply above that corresponding to passive dust deposition.…”

“…The Central Red Sea is the most oligotrophic part of the basin, which is clearly evident in the Chl a concentrations there, which are the lowest in the Red Sea (Raitsos et al, 2013). The monsoons and prevailing regional winds play a key role in driving the mechanisms that supply nutrients and consequently regulate the seasonal and interannual variability of Chl a concentrations in the Red Sea (Raitsos et al, 2015). The lack of riverine input and negligible precipitation mean that the main nutrient source is the monsoonal-driven horizontal intrusion of nutrient-rich waters from the Indian Ocean (Murray and Johns, 1997;Johns and Sofianos, 2012;Churchill et al, 2014;Raitsos et al, 2015).…”

“…The monsoons and prevailing regional winds play a key role in driving the mechanisms that supply nutrients and consequently regulate the seasonal and interannual variability of Chl a concentrations in the Red Sea (Raitsos et al, 2015). The lack of riverine input and negligible precipitation mean that the main nutrient source is the monsoonal-driven horizontal intrusion of nutrient-rich waters from the Indian Ocean (Murray and Johns, 1997;Johns and Sofianos, 2012;Churchill et al, 2014;Raitsos et al, 2015). The intruding water flows northward along the African and Arabian coasts of the Red Sea, hardly reaching the Central Red Sea (Churchill et al, 2014).…”