The dynamics of organic production in the Rockall Channel area

1986 ◽  
Vol 88 ◽  
pp. 207-220
Author(s):  
B. Zeitzschel
Keyword(s):  
Spring Bloom ◽  
Standing Stock ◽  
Euphotic Zone ◽  
Organic Production ◽  
Substantial Part ◽  
Cell Aggregates ◽  
Nutrient Depletion ◽  
New Production ◽  
Faecal Pellets ◽  
The Stability

SynopsisFor the onset of the phytoplankton spring bloom in temperate waters, the irradiance, the concentration of accumulated nutrients and the stability of the water column are of great importance. The “new” production in spring is produced mainly by chain forming diatoms.The dissipation of the spring bloom is due to nutrient depletion in the stabilised surface layer, loss of cells by sinking and grazing by herbivorous zooplankton. After the nutrient concentration is lowered, the rate of production will depend primarily on the rate of replenishment of nutrients. In open ocean environments we find “regenerated production” which is due to exudated and excreted nutrient salts e.g. ammonium. The dominating group of phytoplankters are small flagellates. It is argued that a substantial part of the phytoplankton standing stock in spring is lost from the euphotic zone due to direct sinking of cells or accelerated sinking of cell-aggregates. It is postulated that faecal pellets of micro- and mesozooplankton are retained and recycled in the mixed layer, whereas macrozooplankton faecal strings transport a considerable amount of organic matter to the benthal.

Behavior of Cu, Ni and Cd during nutrient depletion in a spring bloom in Funka Bay

1998 ◽  
Vol 54 (6) ◽  
pp. 619-627 ◽  
Author(s):  
Isao Kudo ◽  
Katsuhiko Matsunaga
Keyword(s):  
Spring Bloom ◽  
Nutrient Depletion ◽  
Funka Bay

scholarly journals Non-Chemical Weed Management in Vegetables by Using Cover Crops: A Review

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 257 ◽  
Author(s):  
Husrev Mennan ◽  
Khawar Jabran ◽  
Bernard H. Zandstra ◽  
Firat Pala
Keyword(s):  
Weed Control ◽  
Cover Crops ◽  
Weed Management ◽  
Water Conservation ◽  
Crop Residues ◽  
Production Systems ◽  
Organic Production ◽  
Substantial Part ◽  
Vegetable Production ◽  
Negative Effects

Vegetables are a substantial part of our lives and possess great commercial and nutritional value. Weeds not only decrease vegetable yield but also reduce their quality. Non-chemical weed control is important both for the organic production of vegetables and achieving ecologically sustainable weed management. Estimates have shown that the yield of vegetables may be decreased by 45%–95% in the case of weed–vegetable competition. Non-chemical weed control in vegetables is desired for several reasons. For example, there are greater chances of contamination of vegetables by herbicide residue compared to cereals or pulse crops. Non-chemical weed control in vegetables is also needed due to environmental pollution, the evolution of herbicide resistance in weeds and a strong desire for organic vegetable cultivation. Although there are several ways to control weeds without the use of herbicides, cover crops are an attractive choice because these have a number of additional benefits (such as soil and water conservation) along with the provision of satisfactory and sustainable weed control. Several cover crops are available that may provide excellent weed control in vegetable production systems. Cover crops such as rye, vetch, or Brassicaceae plants can suppress weeds in rotations, including vegetables crops such as tomato, cabbage, or pumpkin. Growers should also consider the negative effects of using cover crops for weed control, such as the negative allelopathic effects of some cover crop residues on the main vegetable crop.

scholarly journals Climate Driven Changes in Timing, Composition and Magnitude of the Baltic Sea Phytoplankton Spring Bloom

2019 ◽  
Vol 6 ◽  
Author(s):  
Olle Hjerne ◽  
Susanna Hajdu ◽  
Ulf Larsson ◽  
Andrea S. Downing ◽  
Monika Winder
Keyword(s):  
Baltic Sea ◽  
Secondary Production ◽  
Spring Bloom ◽  
High Water ◽  
Aquatic Systems ◽  
Substantial Part ◽  
Phytoplankton Blooms ◽  
The Baltic Sea ◽  
Benthic Secondary Production ◽  
The Baltic

Spring phytoplankton blooms contribute a substantial part to annual production, support pelagic and benthic secondary production and influence biogeochemical cycles in many temperate aquatic systems. Understanding environmental effects on spring bloom dynamics is important for predicting future climate responses and for managing aquatic systems. We analyzed long-term phytoplankton data from one coastal and one offshore station in the Baltic Sea to uncover trends in timing, composition and size of the spring bloom and its correlations to environmental variables. There was a general trend of earlier phytoplankton blooms by 1–2 weeks over the last 20 years, associated with more sunshine and less windy conditions. High water temperatures were associated with earlier blooms of diatoms and dinoflagellates that dominate the spring bloom, and decreased diatom bloom magnitude. Overall bloom timing, however, was buffered by a temperature and ice related shift in composition from early blooming diatoms to later blooming dinoflagellates and the autotrophic ciliate Mesodinium rubrum. Such counteracting responses to climate change highlight the importance of both general and taxon-specific investigations. We hypothesize that the predicted earlier blooms of diatoms and dinoflagellates as a response to the expected temperature increase in the Baltic Sea might also be counteracted by more clouds and stronger winds. A shift from early blooming and fast sedimenting diatoms to later blooming groups of dinoflagellates and M. rubrum at higher temperatures during the spring period is expected to increase energy transfers to pelagic secondary production and decrease spring bloom inputs to the benthic system, resulting in lower benthic production and reduced oxygen consumption.

Responses by benthic organisms to inputs of organic material to the ocean floor: a review

1990 ◽  
Vol 331 (1616) ◽  
pp. 119-138 ◽  
Keyword(s):  
Organic Material ◽  
Euphotic Zone ◽  
Ocean Floor ◽  
Sediment Surface ◽  
Benthic Organisms ◽  
Faecal Pellets ◽  
Reproductive Cycles ◽  
Benthic Ecosystems ◽  
Deposit Feeding ◽  
Northeastern Atlantic

Most of the photosynthetically produced organic material reaching the ocean-floor is transported as settling particles, among which larger particles such as faecal pellets and macroaggregates (marine snow) are particularly important. Recent studies in the northeastern Atlantic have demonstrated that macroaggregates originating from the euphotic zone settle at a rate of approximately 100-150 m d -1 to form a deposit (phytodetritus) on the sediment surface. Bacteria and protozoa (flagellates and foraminifers) rapidly colonize and multiply on phytodetritus, while large deposit feeding animals ingest it. Other inputs, for example Sargassum , wood and vertebrate carcasses, also evoke a rapid response by benthic organisms. However, the taxa that respond depend on the form of the organic material. The intermittent or seasonally pulsed nature of phytodetritus and many other inputs regulate the population dynamics and reproductive cycles of some responding species. These are often opportunists that are able to utilize ephemeral food resources and, therefore, undergo rapid fluctuations in population density. In addition, the patchy distribution of much of the organic material deposited on the ocean-floor probably plays a major role in structuring deep-sea benthic ecosystems.

New and regenerated primary production in a productive reservoir ecosystem

2010 ◽  
Vol 67 (2) ◽  
pp. 278-287 ◽  
Author(s):  
Leah M. Domine ◽  
Michael J. Vanni ◽  
William H. Renwick
Keyword(s):  
Primary Production ◽  
Euphotic Zone ◽  
Gizzard Shad ◽  
Phytoplankton Production ◽  
Total Production ◽  
Relative Importance ◽  
Dorosoma Cepedianum ◽  
New Production ◽  
Total Primary Production ◽  
The Difference

The concept of new and regenerated production has been used extensively in marine ecosystems but rarely in freshwaters. We assessed the relative importance of new and regenerated phosphorus (P) in sustaining phytoplankton production in Acton Lake, a eutrophic reservoir located in southwestern Ohio, USA. Sources of nutrients to the euphotic zone, including watershed loading, fluxes from sediments, and excretion by sediment-feeding fish (gizzard shad, Dorosoma cepedianum ), were considered sources of new P input that support new primary production and were quantified over the course of a growing season. Regenerated production was estimated by the difference between new and total primary production. New production represented 32%–53% of total primary production, whereas regenerated production represented 47%–68% of total primary production. P excretion by gizzard shad supplied 45%–74% of new P and 24% of P required for total production. In summary, fluxes of P from the watershed and those from sediment-feeding fish need to be considered in strategies to reduce eutrophication in reservoir ecosystems.

scholarly journals Photochemical production of ammonium in the oligotrophic Cyprus Gyre (Eastern Mediterranean)

2006 ◽  
Vol 3 (3) ◽  
pp. 449-474
Author(s):  
V. Kitidis ◽  
G. Uher ◽  
R. C. Upstill-Goddard ◽  
R. F. C. Mantoura ◽  
G. Spyres ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Significant Contribution ◽  
Eastern Mediterranean ◽  
Light Attenuation ◽  
Euphotic Zone ◽  
Surface Mixed Layer ◽  
New Production ◽  
Light Absorbance ◽  
Local Noon

Abstract. We investigated the photoproduction of ammonium (NH4+) in surface waters of the Cyprus gyre in the central Eastern Mediterranean in May 2002, in 8 on deck irradiations with freshly collected, filtered samples. NH4+ photoproduction (photoammonification) increased with time-integrated irradiance during the course of irradiations. Photoammonification rates around local noon were 0.4–2.9 nmol L−1 h−1. Normalised to time integrated irradiance, these rates were 0.9–3.8 pmol L−1 h−1/(W m−2) and were significantly correlated with Chromophoric Dissolved Organic Matter (CDOM) absorbance at 300 nm normalised to Dissolved Organic Carbon (DOC). These results are consistent with the notion that successive CDOM photobleaching in the surface mixed layer results in decreased DOC-normalised light absorbance concurrent with decreased dissolved organic matter reactivity with regard to photochemical NH4+ release. Combining our experimental data with estimates of annual solar irradiance and water column light attenuation yields an annual photoammonification rate for the Cyprus Gyre of 40±17 mmol m−2 a−1, equivalent to ~12±5% of the previously estimated annual nitrogen requirement of new production in this region. Based on this analysis, NH4+ photoproduction makes a small, but significant contribution to the nitrogen budget of the euphotic zone in the oligotrophic Cyprus Gyre.

scholarly journals Photochemical production of ammonium in the oligotrophic Cyprus Gyre (Eastern Mediterranean)

2006 ◽  
Vol 3 (4) ◽  
pp. 439-449 ◽  
Author(s):  
V. Kitidis ◽  
G. Uher ◽  
R. C. Upstill-Goddard ◽  
R. F. C. Mantoura ◽  
G. Spyres ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Eastern Mediterranean ◽  
Light Attenuation ◽  
Euphotic Zone ◽  
N Deposition ◽  
Surface Mixed Layer ◽  
Atmospheric N Deposition ◽  
New Production ◽  
Order Of Magnitude

Abstract. We investigated the photoproduction of ammonium (NH4+) in surface waters of the Cyprus gyre in the central Eastern Mediterranean in May 2002, in 8 on deck irradiations with freshly collected, filtered samples. NH4+ photoproduction (photoammonification) increased with time-integrated irradiance during the course of irradiations. Photoammonification rates around local noon were 0.4–2.9 nmol L−1 h−1. Normalised to time integrated irradiance, these rates were 0.9–3.8 pmol L−1 h−1/(W m−2) and were significantly correlated with Chromophoric Dissolved Organic Matter (CDOM) absorbance at 300 nm normalised to Dissolved Organic Carbon (DOC). These results are consistent with the notion that successive CDOM photobleaching in the surface mixed layer results in decreased DOC-normalised light absorbance concurrent with decreased dissolved organic matter reactivity with regard to photochemical NH4+ release. Combining our experimental data with estimates of annual solar irradiance and water column light attenuation yields an annual photoammonification rate for the Cyprus Gyre of 40±17 mmol m−2 a−1, equivalent to ~12±5% of the previously estimated annual nitrogen requirement of new production and in the same order of magnitude as atmospheric N deposition in this region. Based on this analysis, NH4+ photoproduction makes a small, but significant contribution to the nitrogen budget of the euphotic zone in the oligotrophic Cyprus Gyre.

scholarly journals A microcosm approach on the potential effects of the vertical mixing of water masses over the primary productivity and phytoplankton biomass in the southern Brazilian coastal region

2004 ◽  
Vol 52 (3-4) ◽  
pp. 167-182 ◽  
Author(s):  
Flávia Marisa Prado Saldanha-Corrêa ◽  
Sônia Maria Flores Gianesella
Keyword(s):  
Phytoplankton Community ◽  
Seawater Temperature ◽  
Time Lag ◽  
Mixing Layer ◽  
Vertical Mixing ◽  
Coastal Region ◽  
Euphotic Zone ◽  
Phytoplankton Growth ◽  
Growth Potential ◽  
New Production

The vertical mixing between South Atlantic Central Water (SACW) and Coastal Water (CW) was simulated through microcosm experiments using the autochthonous phytoplankton community (fraction < 150 mm), without nutrient enrichments. SACW is cold (T< 18°C) and nutrient rich, while CW is warmer (T> 20°C) and oligotrophic. The phytoplankton growth potential of SACW, CW and an equivalent mixture of both (SACW+CW) was compared, under 100, 30 and 10% of sunlight, at surface seawater temperature, in winter and summer conditions. Results demonstrate the importance of SACW as a natural eutrophication agent for the mixing layer, allowing the occurrence of new production by nutrient input, and also as a biological seeder through the development of its autochthonous phytoplankton community when it reaches the euphotic zone. The time lag for phytoplankton development during winter was around 4-5 days, against 1-2 days in summer. The hypothesis of physiological differences between surface and bottom phytoplankton populations from a deep (80 m) and thermally homogeneous water column (common winter feature) was also tested through the microcosm experiments. Results obtained clearly demonstrate that bottom water presented higher phytoplankton growth potential than the surface one.

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