A critical re-assessment of the primary productivity of the Yellow Sea, East China Sea and Sea of Japan/East Sea Large Marine Ecosystems
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Marine ecosystem
Primary productivity
China sea
Primary productivity
Stratification (seeds)
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The vertical distribution of chlorophyll a in the Gulf of California during the spring of 1992 showed a subsurface maxima between 10 and 50 m of depth. The average surface chlorophyll concentration was 0.71 mg m–3. It was linearly related to the integrated chlorophyll of the euphotic zone (r2 = 0.3 1, p < 0.001) and in the first optical depth (r2 = 0.56, p < 0.00l), estimated from a spectral model. The highest values of the integrated chlorophyll of the euphotic zone were found at the region of the large islands (62.76 mg m–2). The calculated values of integrated chlorophyll and incident irradiance were used to estimate primary productivity in the water column of the Gulf of California, throughout the parameter Ψ*. The predictions obtained with different values of this parameter were compared with measurements of primary productivity made in situ with the 14C method and estimated with natural fluorescente. Productivity increased to the north, reaching maximum values at the large islands region. Ψ*p = 0.039 + 0.017 m2 (gCla)–1 is proposed for spring in the Gulf of California.
Primary productivity
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Particulate organic carbon (POC) sinking out of the sunlit euphotic zone at the surface of the ocean feeds the deep sea and alters the CO 2 concentration of the atmosphere. Most of the sinking POC is reoxidized to dissolved inorganic carbon (DIC) before it hits the sea floor, but the mechanism for this is poorly understood. Here we develop a global model of the microbial loop in the aphotic zone based on new measurements of deep ocean bacterial metabolism. These together imply that a significant fraction of the decreasing POC flux with depth is converted to dissolved organic carbon (DOC) rather than directly to DIC as is commonly assumed, thereby providing the substrate for free‐living bacteria in the deep ocean. The model suggests the existence of a substantial DOC‐pool with a relatively fast turnover time in the deep sea. By implementing the microbial loop in a model of the global ocean circulation, we show that the observed gradient of DOC in the deep North Atlantic can be explained by the temperature dependence of bacterial metabolic activity in conjunction with the formation of deep‐water at high latitudes.
Microbial loop
Deep ocean water
Biological pump
Carbon fibers
Particulate organic carbon
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The vertical distribution of chlorophyll a in the Gulf of California during the spring of 1992 showed a subsurface maxima between 10 and 50 m of depth. The average surface chlorophyll concentration was 0.71 mg m-3. It was linearly related to the integrated chlorophyll of the euphotic zone (r* = 0.3 1, p < 0.001) and in the tirst optical depth (r* = 0.56, p < O.OOl), estimated from a spectral model. The highest values of the integrated chlorophyll of the euphotic zone were found at the region of the large islands (62.76 mg m”). The calculated values of integrated chlorophyll and incident irradiance were used to estimate primary productivity in the water column of the Gulf of California, throughout the parameter Y”. The predictions obtained with different values of this parameter were compared with measurements of primary productivity made in situ with the 14C method and estimated with natural fluorescente. Productivity increased to the north, reaching maximum values at the large islands region. Y’, = 0.039 + 0.017 m2 (gCla)’ is proposed for spring in the Gulf of California.
Primary productivity
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The fraction of primary production lost to sinking (the export ratio) increases with productivity in the ocean and decreases slightly with productivity in lakes. To explore why this distinction exists, we compared marine and freshwater regressions relating chlorophyll concentrations in the euphotic zone to each of the three variables that define the export ratio: primary productivity, carbon sinking fluxes, and euphotic zone depth. Chlorophyll was found to predict these three variables well ( r 2 = 0.54–0.90) in both lakes and the ocean. The differences between the marine and freshwater export ratio—productivity relationships stem primarily from a discrepancy in the primary productivity—Chl relationships. On average, a >10‐fold difference in Chl‐specific productivity exists between the most oligotrophic lakes (Chl = 0.2 mg −3 ) and oceanic regions with similar Chl concentrations. This difference disappears at higher concentrations of Chl because primary productivity: Chl ratios increase with productivity in lakes. In addition, carbon sinking rates average 2–3‐fold higher in the oceans than in lakes with similar concentrations of Chl. The trends of marine and freshwater export ratio‐production can be qualitatively reproduced with Chl‐based predictions of euphotic zone primary productivity, depth, and carbon sinking losses from regressions. Marine and freshwater ecosystems may differ systematically in the efficiency of nutrient recycling processes in the water column and in the nature of settling material.
Primary productivity
Biological pump
New production
Total inorganic carbon
Marine ecosystem
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Primary productivity
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China sea
Yangtze river
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Eukaryotic molecular diversity within the picoplanktonic size-fraction has primarily been studied in marine surface waters. Here, the vertical distribution of picoeukaryotic diversity was investigated in the Sargasso Sea from euphotic to abyssal waters, using size-fractionated samples (< 2 microm). 18S rRNA gene clone libraries were used to generate sequences from euphotic zone samples (deep chlorophyll maximum to the surface); the permanent thermocline (500 m); and the pelagic deep-sea (3000 m). Euphotic zone and deep-sea data contrasted strongly, the former displaying greater diversity at the first-rank taxon level, based on 232 nearly full-length sequences. Deep-sea sequences belonged almost exclusively to the Alveolata and Radiolaria, while surface samples also contained known and putative photosynthetic groups, such as unique Chlorarachniophyta and Chrysophyceae sequences. Phylogenetic analyses placed most Alveolata and Stramenopile sequences within previously reported 'environmental' clades, i.e. clades within the Novel Alveolate groups I and II (NAI and NAII), or the novel Marine Stramenopiles (MAST). However, some deep-sea NAII formed distinct, bootstrap supported clades. Stramenopiles were recovered from the euphotic zone only, although many MAST are reportedly heterotrophic, making the observed distribution a point for further investigation. An unexpectedly high proportion of radiolarian sequences were recovered. From these, five environmental radiolarian clades, RAD-I to RAD-V, were identified. RAD-IV and RAD-V were composed of Taxopodida-like sequences, with the former solely containing Sargasso Sea sequences, although from all depth zones sampled. Our findings highlight the vast diversity of these protists, most of which remain uncultured and of unknown ecological function.
Radiolaria
Abyssal zone
Mesopelagic zone
Deep chlorophyll maximum
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China sea
Yangtze river
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New production
Particulate organic carbon
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