Bloom-forming potentially toxic dinoflagellates Prorocentrum cordatum in marine plankton food webs (original) (raw)
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Review of the Main Ecological Features Affecting Benthic Dinoflagellate Blooms
Cryptogamie, Algologie, 2012
B oth benthic and planktic dinoflagellates can produce harmful algal blooms. However most of the studies conducted so far emphasized on planktic species. In the present review, we assessed the main ecological factors affecting the population dynamics of bloomforming benthic dinoflagellates, with particular emphasis on Ostreopsis and Gambierdiscus. Based on the basic equation of population dynamics, we mainly focused on growth, predation, mortality, immigration and dispersion. Factors determining the dynamics of benthic dinoflagellate populations are very different from the well-studied case of planktic dinoflagellates. The relative movement of cells and water is the main difference as benthic dinoflagellates depend on af ixed substratum while planktic dinoflagellates depend on a water body. Any alteration in the substratum will affect benthic dinoflagellate populations, as for example the changes in seaweeds concentrations due to predation by sea urchins. We also evaluated the impact of global changes on dinoflagellates bloom occurrence.
Marine Ecology Progress Series, 2005
Growth and mortality rates of natural single Alexandrium spp. cells were measured by the Landry-Hassett dilution technique during different phases of blooms. Taxon-specific experiments were conducted between May and October 2002 during 3 intense blooms of A. taylori and A. catenella at different locations of the Mediterranean Sea. In addition, dilution experiments using chlorophyll a as a proxy for total phytoplankton biomass were used to estimate daily rates of net growth and mortality of the total phytoplankton community. A. taylori growth rates ranged from 0.04 to 0.67 d -1 and mortality rates from -0.20 to -0.65 d -1 . Growth rates of Gymnodinium sp., an accompanying dinoflagellate species during the A. taylori bloom studied, were similar to those measured for A. taylori, whereas their mortality rates (-0.58 to -0.82 d -1 ) were slightly higher. A. catenella growth and mortality rates were balanced (0.24 and 0.44 d -1 compared with -0.25 and -0.44 d -1 , respectively). The highest mortality rates (-0.65 d -1 ) were measured during the decline phase of 2 A taylori blooms. At the decline of the blooms, A. taylori and A. catenella showed considerable mortality, but microzooplankton grazing was not confirmed to be the main cause of the bloom termination. In general, growth was not limited by nutrients in the experiments. There were a few cases of a potential nutrient limitation in these areas and, in general, blooms were not conditioned by nutrients. When changes in biomass (chlorophyll a) were measured, non-linearity of data due to saturation was observed. The interpretation of these results required a split-function model. Saturated grazing (G s ) was 28.9 µg chl a l -1 d -1 , during which the saturating phytoplankton population represented a chl a concentration of 16 µg l -1 (P s ).
The Ecology of Harmful Dinoflagellates
Ecological Studies, 2006
Dinoflagellates are mostly estuarine and marine, with only ~250-300 of thẽ 2,000 known species inhabiting freshwaters (Graham and Wilcox 2000; Carty 2003). Most species are considered beneficial; dinoflagellates are dominant primary producers in the tropical and subtropical oceans, and are also abundant in late spring/summer plankton of temperate and subarctic seas, and in ice communities from the Antarctic to northern temperate lakes.About half of the known free-living species are exclusively heterotrophic (Gaines and Elbrächter 1987) and, thus, poorly fit the classical definition of algae. In fact, Graham and Wilcox (2000) referred to dinoflagellates as "fundamentally heterotrophic protists." Relatively few are harmful (~185 species; Smayda and Reynolds 2003), defined here as producing potent toxins (~60 estuarine and marine species; Burkholder 1998) and/or other bioactive substances that adversely affect beneficial organisms (Smayda 1997; Rengefors and Legrand 2001); causing disease or death of beneficial aquatic life by predation or parasitism; and/or causing undesirable changes in habitats. Although most harmful dinoflagellates are planktonic, free-living benthic species are important ciguatoxin producers, and various parasitic taxa also have a benthic habit, growing attached to or inside prey. In this chapter, general ecological features of harmful dinoflagellates are reviewed, followed by consideration of frameworks to advance understanding. A caveat is merited: generalizations about a given species are often based upon the characteristics of one strain as representative of all strains of that species in nature. The complex reality, instead, is that major intraspecific variability is common in harmful dinoflagellates, as in other harmful algae (reviewed in Burkholder et al. 2001; Burkholder and Glibert 2005)-so much so that opposite interpretations presented as conclusions have been gained from considering only individual strains, to the detriment of ecological understanding. High intraspecific variability in life-history traits, behavior, growth, nutrition, blooms, toxicity, and genetics has been documented for Ecological Studies, Vol. 189 Edna Granéli and Jefferson T. Turner (Eds.) Ecology of Harmful Algae © Springer-Verlag Berlin Heidelberg 2006 many harmful dinoflagellates. Strain differences are a fundamental characteristic in the ecology of these species, and should be a critical consideration in forming interpretations. Nutrients x turbulence = productive potential Nutrients x turbulence = gradient
Regional Studies in Marine Science
Benthic dinoflagellates contribute significantly to the primary production and thereby the sustenance of shallow marine environments. However, some of them are considered potentially toxic or harmful species posing a serious threat to this marine ecosystem. The paper describes an extensive bloom of the dinoflagellate Prorocentrum rhathymum for the first time from the Lakshadweep waters in the eastern Arabian Sea. The dinoflagellates were observed as an intense bloom in the Bangaram Lagoon of Lakshadweep archipelago. The cells of P. rhathymum (7.6 x10 5 cells L −1) were observed in mucilaginous aggregations with macroalgal debris and filaments of the cyanobacterium, Trichodesmium erythraeum. The bloom area was devoid of other microalgal species, and P. rhathymum was also observed to be attached to fresh macroalgal thalli in the nearshore areas (4.67 x10 4 cells g −1 wet weight of macroalgae). These observations suggest that the debris of macroalgae washed into the water column act as a substrate for the transport of P. rhathymum towards the water column. Warm sea surface temperature (SST, 29.7 • C) and stable conditions of the water column favoured the bloom of P. rhathymum in the Bangaram Lagoon during the spring inter-monsoon season. Coral reef ecosystems along the Indian EEZ are the least surveyed regarding the prevalence of harmful or toxic species, and most of the harmful algal bloom (HAB) events in these systems remain overlooked. Routine monitoring and meticulous bloom physiology studies can provide insights into the prevalence of HAB and prediction of such events in these diverse ecosystems.
Journal of Phycology, 2007
Harmful algal blooms (HABs) are common phenomena in coastal waters of the Mediterranean Sea. Most of these blooms are caused by dinoflagellates, including Alexandrium minutum as one of the most widespread species (Honsell et al. 1995). This specific organism is one of the toxic algae associated with paralytic shellfish poisoning (PSP) and is, therefore, the center of attention for many scientific studies worldwide. Dinoflagellates are characterized by optimum growth rates under low-turbulence conditions, whereas elevated cellular densities (i.e., bloom conditions) of small-sized species (like A. minutum) are usually coincident with high nutrient levels 1
Harmful Algae, 2013
Massive blooms of the dinoflagellate Cochlodinium polykrikoides occur annually in the Chesapeake Bay and its tributaries. The initiation of blooms and their physical transport has been documented and the location of bloom initiation was identified during the 2007 and 2008 blooms. In the present study we combined daily sampling of nutrient concentrations and phytoplankton abundance at a fixed station to determine physical and chemical controls on bloom formation and enhanced underway water quality monitoring (DATAFLOW) during periods when blooms are known to occur. While C. polykrikoides did not reach bloom concentrations until late June during 2009, vegetative cells were present at low concentrations in the Elizabeth River (4 cells ml À1) as early as May 27. Subsequent samples collected from the Lafayette River documented the increase in C. polykrikoides abundance in the upper branches of the Lafayette River from mid-June to early July, when discolored waters were first observed. The 2009 C. polykrikoides bloom began in the Lafayette River when water temperatures were consistently above 25 8C and during a period of calm winds, neap tides, high positive tidal residuals, low nutrient concentrations, and a low dissolved inorganic nitrogen (DIN) to dissolved inorganic phosphorous (DIP) ratio. The pulsing of nutrients associated with intense but highly localized storm activity during the summer months when water temperatures are above 25 8C may play a role in the initiation of C. polykrikoides blooms. The upper Lafayette River appears to be an important area for initiation of algal blooms that then spread to other connected waterways.