11 research outputs found
WEST: A northern California study of the role of wind-driven transport in the productivity of coastal plankton communities
Hydrography, nutrients and chlorophyll during El Niño and La Niña 1997-99 winters in the Gulf of the Farallones, California
Nutrient and chlorophyll concentrations were measured in January 1997, 1998 and 1999 in the Gulf of the Farallones, CA at locations stretching north/south from Point Reyes to Half Moon Bay, and seaward from the Golden Gate to the
Farallon Islands. The cruises were all carried out during periods of high river flow, but under different climatological
conditions with 1997 conditions described as relatively typical or ‘neutral/normal’, compared to the El Niño warmer
water temperatures in 1998, and the cooler La Niña conditions in 1999. Near-shore sea-surface temperatures ranged from cold (9.5–10.5°C) during La Niña 1999, to average (11–13°C) during 1997 to warm (13.5–15°C) during El Niño 1998. Nutrients are supplied to the Gulf of the Farallones both from San Francisco Bay (SFB) and from oceanic sources, e.g. coastal upwelling near Point Reyes. Nutrient supplies are strongly influenced by the seasonal cycle of fall calms,
with storms (commencing in January), and the spring transition to high pressure and northerly upwelling favorable
winds. The major effect of El Niño and La Niña climatic conditions was to modulate the relative contribution of SFB to nutrient concentrations in the coastal waters of the Gulf of the Farallones; this was intensified during the El Niño winter and reduced during La Niña. During January 1998 (El Niño) the oceanic water was warm and had low or
undetectable nitrate, that did not reach the coast. Instead, SFB dominated the supply of nutrients to the coastal waters Additionally, these data indicate that silicate may be a good tracker of SFB water. In January, delta outflow into SFB
produces low salinity, high silicate, high nitrate water that exits the bay at the Golden Gate and is advected northward
along the coast. This occurred in both 1997 and 1998. However during January 1999, a La Niña, this SFB feature was
reduced and the near-shore water was more characteristic of high salinity oceanic water penetrated all the way to the
coast and was cold (10°C) and nutrient rich (16 μM NO3, 30 μM Si(OH)4). January chlorophyll concentrations ranged
from 1–1.5 μg l 1 in all years with the highest values measured in 1999 (2.5–3 μg l 1) as a result of elevated nutrients
in the area. The impact of climatic conditions on chlorophyll concentrations was not as pronounced as might be expected
from the high temperatures and low nutrient concentrations measured offshore during El Niño due to the sustained
supply of nutrients from the Bay supporting continued primary production
Calculating new production from nitrate reductase activity and light in the Peru current upwelling
8 pages, 3 figures, 3 tablesWe have calculated new production from phytoplankton nitrate reductase (NR) activity and light in the euphotic zone of the Peruvian upwelling system at 15° S. The calculation is based on unique measurements from the Coastal Upwelling Ecosystem Analysis (CUEA) JASON expedition from September 1976. The new production at the 50% light level in the euphotic zone ranged from 3.49 µM C h−1, 12 km downstream from the upwelling center to 0.15 µM C h−1, 46 km further downstream over the 4000 m deep Peru Trench where the upwelling was relatively weak. It compared well with 14C carbon productivity measurements whose range was 0–4.2 µM C h−1 and 0–1.5 µM C h−1 for the 6 h (gross) and 24 h (net) productivity, respectively. In nitrogen units, the overall new production ranged from 4 to 510 nM of N h−1. The oceanographic conditions found during September 1976 made this upwelling site an ideal one to calculate new production. Temperature in the center of the upwelling in September of 1976 reached 14.07 °C, while NO3− ranged from 6.65 to 7.5 µM, and NH4+ stayed below 0.1 µM. Chlorophyll, averaging 3.85 µg L−1 for the section stations in September 1976, was similar to what it was for all the stations 6 months later in March 1977 (3.23 µg L−1). NR, averaging 0.20 µM N h−1 for the section stations in September 1976, was twice what it was for all stations, 6 month later in March 1977 (0.09 µM N h−1).SGG. was self-funded. NSF (USA) grant, OCE 75-23718A01, to TTP, funded JASON-76. TTP was supported by TIAA-CREF, Social Security (USA), and al by the Canary Islands CEI: Tricontinental Atlantic CampusPeer Reviewe
Hydrography, nutrients and chlorophyll during El Niño and La Niña 1997–99 winters in the Gulf of the Farallones, California
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The genome of the diatom Thalassiosira pseudonana: Ecology, evolution, and metabolism
Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for {approx}20% of global carbon fixation. We report the 34 Mbp draft nuclear genome of the marine diatom, Thalassiosira pseudonana and its 129 Kbp plastid and 44 Kbp mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, utilization of a range of nitrogenous compounds and a complete urea cycle, all attributes that allow diatoms to prosper in the marine environment. Diatoms are unicellular, photosynthetic, eukaryotic algae found throughout the world's oceans and freshwater systems. They form the base of short, energetically-efficient food webs that support large-scale coastal fisheries. Photosynthesis by marine diatoms generates as much as 40% of the 45-50 billion tonnes of organic carbon produced each year in the sea (1), and their role in global carbon cycling is predicted to be comparable to that of all terrestrial rainforests combined (2, 3). Over geological time, diatoms may have influenced global climate by changing the flux of atmospheric carbon dioxide into the oceans (4). A defining feature of diatoms is their ornately patterned silicified cell wall or frustule, which displays species-specific nano-structures of such fine detail that diatoms have long been used to test the resolution of optical microscopes. Recent attention has focused on biosynthesis of these nano-structures as a paradigm for future silica nanotechnology (5). The long history (over 180 million years) and dominance of diatoms in the oceans is reflected by their contributions to vast deposits of diatomite, most cherts and a significant fraction of current petroleum reserves (6). As photosynthetic heterokonts, diatoms reflect a fundamentally different evolutionary history from the higher plants that dominate photosynthesis on land. Higher plants and green, red and glaucophyte algae are derived from a primary endosymbiotic event in which a non-photosynthetic eukaryote acquired a chloroplast by engulfing (or being invaded by) a prokaryotic cyanobacterium. In contrast, dominant bloom-forming eukaryotic phytoplankton in the ocean, such as diatoms and haptophytes, were derived by secondary endosymbiosis whereby a non-photosynthetic eukaryote acquired a chloroplast by engulfing a photosynthetic eukaryote, probably a red algal endosymbiont (Fig. 1). Each endosymbiotic event led to new combinations of genes derived from the hosts and endosymbionts (7). Prior to this project, relatively few diatom genes had been sequenced, few chromosome numbers were known, and genetic maps did not exist (8). The ecological and evolutionary importance of diatoms motivated our sequencing and analysis of the nuclear, plastid, and mitochondrial genomes of the marine centric diatom Thalassiosira pseudonana