Synoptic study of variations in the fluorescence based maximum quantum efficiency of photosynthesis across the North Atlantic Ocean

Abstract

Using ship-based phytoplankton fluorescence techniques on a 9-d transect of the North Atlantic Ocean, we have produced the first synoptic view of variations in the maximum quantum yield of photosynthetic energy conversion (4,) on an ocean-wide basis. Based on our 4, measurements, the North Atlantic can be divided into two basins. The southeastern basin (from the African coast to the midocean ridge) is characterized by relatively little horizontal variation in 4, over vast stretches of the ocean. In the northwestern basin (from the midocean ridge to the Canadian coast), we measured lower values of 4, than in the eastern basin, particularly in the upper water column. Lowest surface values were found in an area of strong horizontal flow. Our results suggest that nutrient supply limits phytoplankton productivity over vast stretches of the North Atlantic in this period (early summer). However, surface values of 4, across the North Atlantic appear to be independent of nutrient concentration and distance to nitrate supply. We propose that horizontal advection may play an important role in determining the local conditions to which phytoplankton productivity parameters respond. Our results also suggest that an apparent relationship between remotely sensed variables (ocean color, sea surface height) and phytoplankton photosynthetic parameters exists that may provide the basis for the development of new algorithms used to estimate phytoplankton productivity from satellites.To understand the role of oceanic phytoplankton in global biogeochemical cycles, it is necessary to estimate phytoplankton productivity on a global scale. Ocean color remote sensing can now be used to estimate phytoplankton abundance on a global scale. Satellite sensors can also provide data on atmospheric transmittance, thus allowing estimation of incident irradiance on the ocean surface. However, satellite sensors cannot measure the reactivity (photosynthetic rate) of the phytoplankton pool directly. To estimate oceanic productivity, it is necessary to know l Present address:

Basin-scale variability of phytoplankton biomass, production and growth in the Atlantic Ocean

“…Nanomolar increases in nitrate concentration have been shown to support high surface productivity in Sargasso Sea waters (Glover et al, 1988), and an inverse correlation between integrated productivity and the depth of the nutricline has been previously reported in several nutrient-poor regions of the Atlantic Ocean (Herbland and Voituriez, 1979;Malone et al, 1993). The notion of the phytoplankton growth rate being nitrogen limited in vast areas of the Atlantic Ocean agrees with the observed geographical distribution of the maximum quantum e$ciency of photosynthesis (Geider et al, 1993;Olaizola et al, 1996) and the results of nutrient addition experiments in the North Atlantic . Finally, the correlation between the abundance of N -"xing cyanobacteria and growth rate found between the Equator and 203N during suggests that biological "xation of atmospheric nitrogen can also be an important mechanism in sustaining high biological rates in nutrient-impoverished surface waters (see Karl et al, 1997).…”

“…Nevertheless, despite the great diversity of physical processes operating over large spatial scales (e.g. Olaizola et al, 1996), we still found a signi"cant relationship between phytoplankton growth and the physical and chemical structure of the water column. Similarly, we have shown in a companion study that the light-saturated, chlorophyll a-normalized photosynthetic rate was inversely correlated to the depth of the nutricline (MaranoH n and Holligan, 1999).…”

“…As pointed out by Eppley (1981), horizontal and temporal variations need to be de"ned before any generalization about phytoplankton growth rates can be drawn. However, time series research programmes have no spatial resolution (Lohrenz et al, 1992;Karl and Lukas, 1996), and conversely the studies dealing with large spatial scales usually do not include a temporal component (Geider et al, 1993;Olaizola et al, 1996). Another dimension of the problem is that low-nutrient, open ocean regions have recently been estimated to contribute 80% of the global ocean production and 70% of the total export production .…”

Dynamics of phytoplankton community structure in the South China Sea in response to the East Asian aerosol input

“…7-8). The Fv/Fm ratio, which was driven by phytoplankton community structure as well as nutrient stress (Olaizola et al, 1996;Suggett et al, 2009), showed higher values in the High treatment at stations PM7 and S412 compared with the controls (Fig. 7).…”

Using chlorophyll a fluorescence to detect the onset of anthracene photoinduced toxicity in Lemna gibba, and the mitigating effects of a commercial humic acid

“…For example, room-temperature fluorescence induction is a powerful in vivo indicator of contaminant-related damage to photosystem quantum efficiency in higher plants (Krupa et al 1993;Prevot et al 1993;Streb et al 1993;Sgardelis et al 1994;Gensemer et al 1996;Huang et al 1997a). While Chl a fluorescence induction assays have been used widely in terrestrial plant stress physiology (Hipkins and Baker 1986;Krause and Weis 1991) and in studies examining patterns of marine algal photosynthesis (Falkowski et al 1991;Greene et al 1992;Hofstraat et al 1994;Olson and Zettler 1995;Olaizola et al 1996;Olson et al 1996), its use in freshwater plant contaminant studies is still in its infancy. Furthermore, low-temperature (77ЊK) chlorophyll fluorescence emission scans can present qualitative information regarding the structure and organization of photosystem reaction center pigments (Hipkins and Baker 1986;McCormac et al 1996;Marwood and Greenberg 1996).…”