SCIENCE CHINA Earth Sciences • RESEARCH PAPER •
December 2014 Vol.57 No.12: 3073–3083 doi: 10.1007/s11430-014-4939-8
Phytoplankton and chlorophyll a relationships with ENSO in Prydz Bay, East Antarctica ZHANG HaiSheng1,2*, HAN ZhengBing1,2, ZHAO Jun1,2, YU PeiSong1,2, HU ChuanYu1,2, SUN WeiPing1,2, Yang Dan1,2, ZHU GenHai1,2, LU Bing1,2, Hans-UIrich PETER3 & Walter VETTER3 2
1 The Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China; Laboratory of Marine Ecosystem and Biogeochemistry, State Oceanic Administration, Hangzhou 310012, China; 3 Institute of Ecology, Friedrich Schiller University, Jena, D-07743, Germany
Received November 11, 2013; accepted March 24, 2014; published online October 10, 2014
The historical data of phytoplankton and chlorophyll a (Chl a) (1990–2002) obtained during the Chinese National Antarctic Research Expedition (CHINARE) in the Prydz Bay have been integrated. The results showed that the temperature, salinity, nutrients, and oxygen of seawater changed when El Niño/La Niña occurred. The variation of biological communities reflected the response of ecosystem to environmental changes. During El Niño period, Chl a concentration and phytoplankton community structure changed significantly, and the relative proportion of diatoms increased while dinoflagellates decreased. During La Niña period, the proportion of diatoms decreased, but the golden-brown algae and blue-green algae increased significantly. The variation of phytoplankton population directly affected the biodiversity of the bay, which were also quite sensitive to the marine environment changes. Meanwhile, the satellite remote sensing data of 2002–2011 (December–March) have been used to study the temporal connection change of Chl a and phytoplankton in the Prydz Bay. We found that there were significant differences in the monthly variation characteristics of satellite remote sensing Chl a and sea surface temperature (SST), which had some links with sea ice melting and El Niño/La Niña events. We found that the start time of bloom advanced, lagged or synchronized with the changes of the SST, and we also found the occurrence time of phytoplankton bloom corresponded with the sea ice melting inner bay. To some extent, this study will help us understand the relationships between ENSO events and the phytoplankton bloom in the Southern Ocean. Prydz Bay, Antarctica, phytoplankton, chlorophyll a, sea ice melting, El Niño/La Niña, satellite remote sensing Citation:
Zhang H S, Han Z B, Zhao J, et al. 2014. Phytoplankton and chlorophyll a relationships with ENSO in Prydz Bay, East Antarctica. Science China: Earth Sciences, 57: 3073–3083, doi: 10.1007/s11430-014-4939-8
With the understanding of ENSO (El Niño/La Niña), scientists began to notice the impacts of El Niño/La Niña on marine plankton populations (Yoder and Kennelly, 2003), and they found that phytoplankton growth speed and changes in community structure are closely related to global warming and El Niño/La Niña (Gloersen, 1995; Jiang, 2000; Corwith *Corresponding author (email:
[email protected])
© Science China Press and Springer-Verlag Berlin Heidelberg 2014
and Wheeler, 2002; Whitney and Welch, 2002; Behrenfeld et al., 2006; Harris et al., 2009; Reiss et al., 2009). Murtugudde et al. (1999) and McClain et al. (2004) found that marine primary productivity anomalies are highly correlated to Multivariate ENSO Index (MEI), especially for the interannual variation of marine ecosystem. Behrenfeld et al. (2001) used Aqua satellite remote sensing data to represent the trends of the global ocean Chl a and marine primary productivity from 1997 to 2006, and found that although the earth.scichina.com
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ecological response was different in different latitude sea area, the general trend was forced by the El Niño/La Niña. The melting and freezing of sea ice corresponded with the variations of latent heat, which is the most significant feature in polar oceans. Chinese scholars have proposed a correlation between the Prydz Bay sea ice and ENSO (Bian, 1988; Chen et al., 2004; Yuan and Li, 2008), and then much more lines of evidence showed that the sea ice of the Western Antarctic Peninsula, Bellingshausen Sea, and Western Ross Sea was significantly associated with ENSO(Stammerjohn et al., 2008). Lizotte (2001) and Reiss et al. (2009) studied the relationships between ENSO and inter-annual variability of Antarctic SST, phytoplankton production (characterized by chlorophyll a), and proposed that the ENSO phenomenon has affected the ecosystem of the Antarctic waters. It suggested that the high latitude sea area is much more sensitive to ENSO; although the response and feedback mechanisms have not yet been conclusive between high latitudes and low latitude on global climate variation (ENSO), it has been widely recognized that the low-latitude oceans do influence the high -latitude oceans through ocean circulation and atmospheric circulation(Philander et al., 1984; McPhaden et al., 1998; Li and Mu, 1999; Chen and Wang, 2009). However, scientists gained a new understanding in recent researches of the Antarctic(White and Peterson, 1996; Cai and Baines, 2001; Liu and Yang, 2004; Cai et al., 2005), and proposed that there is a certain relationship between the Antarctic sea ice and ENSO cycle. Anomalies of sea ice (sea ice reduction) of key district subject to temperature, air pressure and wind, which affected ocean currents and impacted the ENSO occurrence and development, besides clearly lagged ENSO. The increase or decrease of the Antarctic sea ice extent anomalies directly affected the Antarctic Circumpolar Current (ACC) heating and cooling structure and meridional transport, which played a catalytic role in ENSO events. Yuan and Li (2008) proposed a conceptual assumption that there was a teleconnection between high-latitude ENSO events and the sea ice. What role did the Southern Ocean exactly play in this complex ENSO sea-air interaction? Especially the East Antarctic sea ice changes were more closely to the ENSO cycle, which warrants further exploration and research. In this study, we integrated the Chinese National Antarctic Research Expedition’s (CHINARE) historical in situ data of phytoplankton (1990–2002), and particularly studied the relationships between the El Niño/La Niña and the variations of phytoplankton species and Chl a. And we combined the satellite remote sensing data (2002–2011) of Chl a, SST and sea ice to obtain more continuous evidence, especially the occurrence of bloom response on SST and sea ice in the summer of the Antarctic marine phytoplankton blooms. It will help us further explore the polar environment and marine life evolution, and will provide a new understanding about response and feedback of the Southern Ocean to global warming.
December (2014) Vol.57 No.12
1
Study area
The Prydz Bay is located in the Indian Ocean Sectors of Southern Ocean. It is the third largest bay in the Antarctic continent, and is only smaller than the Weddell Sea and Ross Sea. It is adjacent to the Fram Bank to the west, adjacent to the Davis Station of Australia to the east, and is connected with the Amery Ice Shelf to the south. The investigation of phytoplankton, Chl a, and nutrients in the Prydz Bay was conducted during the CHINARE (1990–2002). From 2002 to 2011, there are three longitudinal sections during CHINARE, with P2 section located in shelf, slope, and deep-sea areas and P3 and P4 section in the Prydz Bay, near shore shelf, slope, and deep sea area (Figure 1).
2 Methods 2.1
Sampling and identification of phytoplankton
Surface water (500 cm3) was saved with neutral formalin immediately for analysis and identification of phytoplankton. In laboratory, we used Olympus-VANOX-AHB: LBmicroscope (made in Japan) to observe, identify and count phytoplankton. 2.2
Analysismethod of nutrients
Water samples were collected by Rosette Sampler at different depth: 0, 25, 50, 100, 150 and 200 m, and five kinds of nutrients (phosphate, silicate, nitrate, nitrite, and ammonium) were analyzed in situ from 1990 to 2011. According to GB12763.4-91, the water samples were filtrated through cellulose acetate membranes (pore size 0.45 m), and then analyzed by 7230G spectro photometer. The standard solution sare compounded by the Standard Substance Center of the Second Institute of Oceanography (CBW0817-08645). 2.3
Determination of Chlorophyll a
Samples collected by Rosette Sampler at different depth which was same to the nutrients’, and the analysis of chlorophyll a adopted extraction fluorometry (GB12763.6). Samples were collected by gentle pressure filtration (
