The mechanisms that trigger blooms have been studied for decades, but are still keenly debated, due in part to a lack of data on phytoplankton stocks in winter and early spring. One drop of water from the Bay may contain thousands of phytoplankton. "Climate forcing of the spring bloom in Chesapeake Bay". These blooms tend to be more intense than spring blooms of temperate areas because there is a longer duration of daylight for photosynthesis to take place. Limnology and Oceanography 4(4) 425-440, Durbin, A.G. and Durbin, E.G. These maps show average chlorophyll concentration in May 2003–2010 (left) and November 2002–2009 (right) in the Pacific Ocean. [3] However, new explanations have been offered recently, including that blooms occur due to: At greater latitudes, spring blooms take place later in the year. The spring bloom is a strong increase in phytoplankton abundance (i.e. or the dinoflagellate Karenia brevis can produce toxins harmful to copepods, fish, and higher trophic levels like dolphins and humans. (1994). Succession occurs because different species have optimal nutrient uptake at different ambient concentrations and reach their growth peaks at different times. Therefore, the greatest number of phytoplankton are found near the water’s surface. However, vertical mixing also causes high losses, as phytoplankton are carried below the euphotic zone (so their respiration exceeds primary production). ", Kristiansen, S., Farbrot, T., and Naustvoll, L. (2001). The blooms are triggered by spring stream runoff, but more importantly by the 24-hour periods of sunlight that occur each spring. "Abandoning Sverdrup's Critical Depth Hypothesis on phytoplankton blooms". ammonium, nitrite, or nitrate). Phytoplankton are the autotrophic components of the plankton community and a key part of ocean and freshwater ecosystems. Diatoms dominated the phytoplankton assem-blage. Bloom initiation at our study site corresponded to an improvement in growth conditions for phytoplankton (increasing light, decreasing mixing layer depth) and was most consistent with the critical depth hypothesis, with the proviso that mixing depth (rather than mixed layer depth) was considered. Huisman, J., van Oostveen, P., Weissing, F.J. (1999). This lag occurs because there is low winter zooplankton abundance and many zooplankton, such as copepods, have longer generation times than phytoplankton. Similarly, Winder and Cloern (2010) described spring blooms as a response to increasing temperature and light availability. [8] Freshwater influences primary productivity in two ways. They found that during warm, wet years (as opposed to cool, dry years), the spatial extent of blooms was larger and was positioned more seaward. Abiotic factors include light availability, nutrients, temperature, and physical processes that influence light availability,[1][2][3][4][5] and biotic factors include grazing, viral lysis, and phytoplankton physiology. However, with the exception of coastal waters, it can be argued, that iron (Fe) is the most limiting nutrient because it is required to fix nitrogen, but is only available in small quantities in the marine environment, coming from dust storms and leaching from rocks. Substantial shifts in the extent and thickness of sea ice have cascading effects on marine primary production and polar ecosystems. One of the best times to observe phytoplankton blooms is during the spring. The onset of the spring bloom (OSB) occurs when phytoplankton growth exceeds losses and is promoted by a transition from deep convection to a shallow mixing layer concurrent with increasing light intensities in nutrient-enriched waters. Also, during these same years, biomass was higher and peak biomass occurred later in the spring. After initiation, the observed bloom developed slowly: over several months both depth-integrated inventories and surface concentrations of chlorophyll a increased only by a factor of ~2 and ~3 respectively. [3] Furthermore, in Long Island Sound and the Gulf of Maine, blooms begin later in the year, are more productive, and last longer during colder years, while years that are warmer exhibit earlier, shorter blooms of greater magnitude.[5]. The community structure of a phytoplankton bloom depends on the geographic location of the bloom … The North Atlantic phytoplankton spring bloom is the pinnacle in an annual cycle that is driven by physical, chemical, and biological seasonality. This is because most organisms are unable to fix atmospheric nitrogen into usable forms (i.e. "Spring bloom nutrient dynamics in the Oslofjord". The annual cycles of phytoplankton in the temperate and subpolar North Atlantic Ocean are characterized by pronounced blooms in spring (Yoder et al. Estuaries and Coasts 33: 448–470. First, because freshwater is less dense, it rests on top of seawater and creates a stratified water column. Miller, C.B. [1][2] This creates a comparatively high nutrient and high light environment that allows rapid phytoplankton growth.[1][2][7]. "Causes and consequences of variability in the timing of spring phytoplankton blooms". The spring bloom started around 18 April and lasted until the middle of May. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Phytoplankton spring bloom initiation: The impact of atmospheric forcing and light in the temperate North Atlantic Ocean. The spring bloom dominates the annual cycle of phytoplankton abundance in large regions of the world oceans. Phytoplankton spring blooms often consist of large diatoms inedible for zooplankton, but the zoospores of their fungal parasites may serve as a food source for this higher trophic level. [1][2][3][5] The most limiting nutrient in the marine environment is typically nitrogen (N). Shifts in the dominant phytoplankton species are likely caused by biological and physical (i.e. [1][2][13] This scenario has been observed in Rhode Island,[14][15][16] as well as Massachusetts and Cape Cod Bay. We estimated the total primary production during the spring bloom in 2002 to range 27–35 g C m−2. Introduction. Until roughly a decade ago, most scientists assumed that phytoplankton remained in a sort of stasis throughout the winter and spring until sea ice break-up. [2], Spring blooms typically last until late spring or early summer, at which time the bloom collapses due to nutrient depletion in the stratified water column and increased grazing pressure by zooplankton.
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