Differential responses of the dinoflagellate Cochlodinium polykrikoides bloom to episodic typhoon events

To better understand the effect of typhoons on the harmful alga Cochlodinium polykrikoides, we investigated cell population dynamics in relation to hydrographic conditions in Korean coastal waters before and after the passage of typhoons. After typhoon Lingling passed through the Yellow Sea, significant accumulation of C. polykrikoides on the southern coast of Namhae Island was associated with southerly winds on September 8, 2019. Similar to field observations of red tide, a particle transport model simulation showed that the virtual particles were greatly influenced by wind-driven currents associated with typhoons, particularly when diel vertical migration was included in the model. However, a bloom of C. polykrikoides disappeared immediately after the passage of typhoon Tapah on September 23, 2019. Because of the different patterns of bloom behavior after the passage of these typhoons, characteristics of other typhoons that affected the Korean peninsula during previous C. polykrikoides blooms were investigated. Analysis of typhoon properties including wind direction, precipitation, and wave height and energy suggested that high wave energy during the passage of a typhoon plays a critical role in the termination of C. polykrikoides blooms, because of its generation of high turbulence relative to other factors. In our study, the wave energy associated with typhoon Tapah (753.6 kJ m^?2 over 48 h) was much higher than that associated with typhoon Lingling (441.7 kJ m^?2 over 48 h). The results indicate that typhoons have an important role in determining the accumulation and termination of C. polykrikoides blooms through the physical effects of wind direction and wave energy.

     

Harmful algal bloom (HAB) in the East Sea identified by the Geostationary Ocean Color Imager (GOCI)

Harmful Cochlodinium polykrikoides blooms have frequently appeared and caused fatal harm to aquaculture in Korean coastal waters since 1995. We investigated the applicability of GOCI, the world's first Geostationary Ocean Color Imager, in monitoring the distribution and temporal movement of a harmful algal bloom (HAB) that was discovered in the East Sea near the Korean peninsula in August 2013. We identified the existence of C. polykrikoides at a maximum cell abundance of over 6000 cells/mL and a chlorophyll a concentration of over 400 mg/m³. In areas of C. polykrikoides blooms, GOCI remote sensing reflectance (R_rs) spectra demonstrated the typical radiometric features of a HAB, and from the diurnal variations using GOCI-derived chlorophyll concentration images, we were able to identify the vertical migration of the red tide species. We also found that the formation and propagation of the HAB had relations with cold water mass in the coastal region. GOCI can be effectively applied to the monitoring of short-term and long-term movements of red tides.     

Applications of Satellite Ocean Color Sensors for Monitoring and Predicting Harmful Algal Blooms

The new satellite ocean color sensors offer a means of detecting and monitoring algal blooms in the ocean and coastal zone. Beginning with SeaWiFS (Sea Wide Field-of-view Sensor) in September 1997, these sensors provide coverage every 1 to 2 days with 1-km pixel view at nadir. Atmospheric correction algorithms designed for the coastal zone combined with regional chlorophyll algorithms can provide good and reproducible estimates of chlorophyll, providing the means of monitoring various algal blooms. Harmful algal blooms (HABs) caused by Karenia brevis in the Gulf of Mexico are particularly amenable to remote observation. The Gulf of Mexico has relatively clear water and K. brevis, in bloom conditions, tends to produce a major portion of the phytoplankton biomass. A monitoring program has begun in the Gulf of Mexico that integrates field data from state monitoring programs with satellite imagery, providing an improved capability for the monitoring of K. brevis blooms.     

Resolving the intra-specific succession within Cochlodinium polykrikoides populations in southern Korean coastal waters via use of quantitative PCR assays

While the toxic dinoflagellate Cochlodinium polykrikoides is known to form blooms that are maintained for extended periods, the genetic differentiation of these blooms are currently unknown. To assess this, we developed a real-time PCR assay to quantify C. polykrikoides at the intra-specific level, and applied this assay to field samples collected in Korean coastal waters from summer through fall. Assays were successfully developed to target the large-subunit ribosomal RNA region of the three major ribotypes of C. polykrikoides: Philippines, East Asian, and American/Malaysian. Significant linear relationships (r² ≥ 0.995) were established between C_t and the log of the copy number for each ribotype qPCR assay. Using these assays, C. polykrikoides blooms in Korean coastal waters were found to be comprised of Philippines and East Asian ribotypes but not the American/Malaysian ribotype. The Philippines ribotype was found to be highly abundant during summer bloom initiation and peak, whereas the East Asian ribotype became the dominant ribotype in the fall. As such, this newly developed qPCR assay can be used to quantify the cryptic ecological succession of sub-populations of C. polykrikoides during blooms that light microscopy and previously developed qPCR assays cannot resolve.     

Dynamics of bacterial community structure during blooms of Cochlodinium polykrikoides (Gymnodiniales,Dinophyceae) in Korean coastal waters

Recent studies of dinoflagellates have reported that blooms can be closely related to the characteristics of the associated bacteria, but studies of the correlation between the toxic dinoflagellate, Cochlodinium polykrikoides and their associated bacterial community composition has not been explored. To understand this correlation, changes in bacterial community structure through the evolution of a C. polykrikoides bloom in Korean coastal waters via clone library analysis were investigated. Although there were no apparent changes in physio-chemical factors during the onset of the C. polykrikoides bloom, the abundance of bacteria bourgeoned in parallel with C. polykrikoides densities. Alpha-, gamma-proteobacteria and Flavobacteria were found to be dominant phyletic groups during C. polykrikoides blooms. The proportion of gamma-proteobacteria was lower (11.8%) during peak of the bloom period compared to the post-bloom period (26.2%). In contrast, alpha-proteobacteria increased in dominance during blooms. Among the alpha-proteobacteria, members of Rhodobacterales abruptly increased from 38% of the alpha-proteobacteria before the bloom to 74% and 56% during the early bloom and peak bloom stages, respectively. Moreover, multiple sites concurrently hosting C. polykrikoides blooms also contained high portions of Rhodobacterales and principal component analysis (PCA) demonstrated that Rhodobacterales had a positive, significant correlation with C. polykrikoides abundances (p ≤ 0.01, Pearson correlation coefficients). Collectively, this study reveals the specific clades of bacteria that increase (Rhodobacterales) and decrease (gamma-proteobacteria) in abundance C. polykrikoides during blooms.     

Cochlodinium polykrikoides blooms and eco-physical conditions in the South Sea of Korea

Eco-physical conditions for the initiation and termination of Cochlodinium polykrikoides blooms in the South Sea of Korea are examined in this paper. The C. polykrikoides blooms generally occur in the sea near Naro-Do in late August every year. The submarine canyon near Naro-Do plays an important role in surface water intrusion from the open ocean driven by northeasterly winds. In late August, the monsoonal wind system in Korea changes from southwesterly to northeasterly winds, causing Ekman transport of warm, fresh Changjiang Diluted Water (CDW) into the sea near Naro-Do and creating a front between inland sea water and CDW. Along the front, aggregation of single C. polykrikoides cells in the CDW and downwelling yield favorable eco-physical conditions for development of C. polykrikoides blooms. When typhoons and strong northeasterly winds bring vertically well-mixed East China Sea water into the sea near Naro-Do again in September, the eco-physical conditions favor diatom growth and lead to the termination of C. polykrikoides blooms.     

Alteration of plankton communities and biogeochemical cycles by harmful Cochlodinium polykrikoides (Dinophyceae) blooms

Cochlodinium polykrikoides is a globally distributed, ichthyotoxic, bloom-forming dinoflagellate. Blooms of C. polykrikoides manifest themselves as large (many km²) and distinct patches with cell densities exceeding 10³ ml⁻¹ while water adjacent to these patches can have low cell densities (<100 cells ml⁻¹). While the effect of these blooms on fish and shellfish is well-known, their impacts on microbial communities and biogeochemical cycles are poorly understood. Here, we investigated plankton communities and the cycling of carbon, nitrogen, and B-vitamins within blooms of C. polykrikoides and compared them to areas in close proximity (<100 m) with low C. polykrikoides densities. Within blooms, C. polykrikoides represented more than 90% of microplankton (>20 μm) cells, and there were significantly more heterotrophic bacteria and picoeukaryotic phytoplankton but fewer Synechococcus. Terminal restriction fragment length polymorphism analysis of 16S and 18S rRNA genes revealed significant differences in community composition between bloom and non-bloom samples. Inside the bloom patches, concentrations of vitamin B₁₂ were significantly lower while concentrations of dissolved oxygen were significantly higher. Carbon fixation and nitrogen uptake rates were up to ten times higher within C. polykrikoides bloom patches. Ammonium was a more important source of nitrogen, relative to nitrate and urea, for microplankton within bloom patches compared to non-bloom communities. While uptake rates of vitamin B₁ were similar in bloom and non-bloom samples, vitamin B₁₂ was taken up at rates five-fold higher (>100 pmol⁻¹ L⁻¹ d⁻¹) in bloom samples, resulting in turn-over times of hours during blooms. This high vitamin demand likely led to the vitamin B₁₂ limitation of C. polykrikoides observed during nutrient amendment experiments conducted with bloom water. Collectively, this study revealed that C. polykrikoides blooms fundamentally change microbial communities and accelerate the cycling of carbon, some nutrients, and vitamin B₁₂.     

First occurrence of Cochlodinium blooms in Sabah, Malaysia

Harmful algal blooms (HABs) resulting in red discoloration of coastal waters in Sepanggar Bay, off Kota Kinabalu, Sabah, East Malaysia, were first observed in January 2005. The species responsible for the bloom, which was identified as Cochlodinium polykrikoides, coincided with fish mortalities in cage-cultures. Determinations of cell density between January 2005 and June 2006 showed two peaks that occurred in March–June 2005 and June 2006. Cell abundance reached a maximum value of 6 × 10⁶ cells L⁻¹ at the fish cage sampling station where the water quality was characterized by high NO₃–N and PO₄–P concentrations. These blooms persisted into August 2005, were not detected during the north–east monsoon season and occurred again in May 2006. Favorable temperature, salinity and nutrient concentrations, which were similar to those associated with other C. polykrikoides blooms in the Asia Pacific region, likely promoted the growth of this species. Identification of C. polykrikoides as the causative organism was based on light and scanning microscopy, and confirmed by partial 18S ribosomal DNA sequences of two strains isolated during the bloom event (GenBank accession numbers DQ915169 and DQ915170).     

Development and field application of rRNA-targeted probes for the detection of Cochlodinium polykrikoides Margalef in Korean coastal waters using whole cell and sandwich hybridization formats

The dinoflagellate, Cochlodinium polykrikoides Margalef, has been responsible for mass mortalities of both wild and farmed fish along the Korean coast on virtually an annual basis since 1982. Economic impacts to the fishing and aquaculture industries are extensive, with a loss of USD $95 million reported in 1995 alone. The use of taxon-specific molecular probes for harmful algal species is recognized as a promising approach for the early detection of bloom formation and as part of an effective mitigation strategy. We have developed and successfully applied large subunit ribosomal RNA (LSU rRNA)-targeted probes in both whole cell and sandwich hybridization assay (SHA) formats for the species-specific detection of C. polykrikoides in Korean coastal waters. Sequences of the D1–D3 variable regions used to design probes were identical between five Korean and one Hong Kong C. polykrikoides isolates, while sequences for several N. American Cochlodinium isolates differed to varying degrees from the former. The automated SHA detected C. polykrikoides at levels as low as 1–3 cells/L in the field, demonstrating its suitability for detecting the target species at pre-bloom concentrations. This method should thus prove valuable to existing monitoring programs aimed at providing aquaculture interests with an early warning of frequently devastating bloom events.     

Ocean color observations of a surface water transport event: Implications for Pseudo-nitzschia on the Washington coast

A persistent patch of high biomass water, associated with the Juan de Fuca Eddy, is often observed in surface chlorophyll a images off the southwest coast of Vancouver Island, Canada. Outbreaks of toxic Pseudo-nitzschia spp. along the Washington, USA, coast are believed to correlate with the transport of waters from Juan de Fuca Eddy southward to Washington beaches. A time series of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite ocean color images from late May 1999 of coastal waters off Washington and Vancouver Island, processed for surface chlorophyll a concentration and spectral remote sensing reflectance, captured a transport event where water from the Juan de Fuca Eddy was transported onto the Washington shelf. Strong upwelling-favorable winds appeared to deform the patch over an 8-day period and move it southward into Washington coastal waters with surface velocities of approximately 8–16 km d⁻¹. SeaWiFS and sea surface temperature imagery showed the local phytoplankton response to wind-driven coastal upwelling restricted to a narrow (10–15 km) region along the Washington coast. Although we did not observe transport of high biomass water originating in the Juan de Fuca Eddy to Washington beaches in May 1999, transport of Pseudo-nitzschia cells could occur following a rapid shift to downwelling-favorable conditions. Tracking the trajectory of surface waters from the Juan de Fuca Eddy by remote sensing could be used to trigger conditional sampling for domoic acid along the Washington coast.     

Molecular cloning reveals co-occurring species behind red tide blooms of the harmful dinoflagellate Cochlodinium polykrikoides

Red tides caused by the marine dinoflagellate Cochlodinium polykrikoides Margalef pose significant environmental problems worldwide. Recently, the existence of severe blooms attributable to a single Cochlodinium Schütt species has been questioned by many researchers. Herein we investigated the dinoflagellate composition of harmful algal blooms (HABs) attributed to C. polykrikoides in Korean coastal waters at nine different stations (St.). The component species of Cochlodinium blooms were examined by using microscopic and gene-cloning methods. In the nine study areas, C. polykrikoides was the predominant species of HABs in St. 2, 4, 7, and St. 9. Based on the morphological identification, the bloom was initially thought to be caused only by C. polykrikoides; however, we detected additional bloom-forming dinoflagellates (Polykrikos schwartzii Bütschli and Polykrikos kofoidii Chatton), and diatoms (Pseudo-nitzschia americana (Hasle) Fryxell) along with C. polykrikoides. The parasitic dinoflagellates Amoebophrya Koeppen and Euduboscquella Coats, Bachvaroff & Delwiche were found to be co-located with Cochlodinium in our study, and for the first time, Cochlodinium fulvescens Iwataki, Kawami & Matsuoka was detected in Korea (west coast). These results suggest co-existence of multiple dinoflagellates in bloom populations of Cochlodinium and describe the composition of other dinoflagellate blooms (e.g., Polykrikos spp.) in Korean coastal regions. This co-occurrence may be considered during efforts to monitor and control HABs.     

Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA

We report on the emergence of Cochlodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Bay, NY, USA, during 2002–2006. Blooms occurred during late summer when temperatures and salinities ranged from 20 to 25 °C and 22 to 30 ppt, respectively. Bloom patches achieved cell densities exceeding 10⁵ ml⁻¹ and chlorophyll a levels exceeding 100 μg l⁻¹, while background bloom densities were typically 10³–10⁴ cells ml⁻¹. Light, scanning electron and ultrathin-section transmission electron microscopy suggested that cells isolated from blooms displayed characteristics of C. polykrikoides and provide the first clear documentation of the fine structure for this species. Sequencing of a hypervariable region of the large subunit rDNA confirmed this finding, displaying 100% similarity to other North American C. polykrikoides strains, but a lower similarity to strains from Southeast Asia (88–90%). Bioassay experiments demonstrated that 24 h exposure to bloom waters (>5 × 10⁴ cells ml⁻¹) killed 100% of multiple fish species (1-week-old Cyprinodon variegates, adult Fundulus majalis, adult Menidia menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation of the gills of moribund fish revealed epithelial proliferation with focal areas of fusion of gill lamellae, suggesting impairment of gill function (e.g. respiration, nitrogen excretion, ion balance). Lower fish mortality was observed at intermediate C. polykrikoides densities (10³–10⁴ cells ml⁻¹), while fish survived for 48 h at cell densities below 1 × 10³ cells ml⁻¹. The inability of frozen and thawed-, or filtered (0.2 μm)-bloom water to cause fish mortality suggested that the thick polysaccharide layer associated with cell membranes and/or a toxin principle within this layer may be responsible for fish mortality. Juvenile bay scallops (Argopecten irradians) and American oysters (Crassostrea virginica) experienced elevated mortality compared to control treatments during a 9-day exposure to bloom water (5 × 10⁴ cells ml⁻¹). Surviving scallops exposed to bloom water also experienced significantly reduced growth rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation, and apoptosis in gill and digestive tissues with gill inflammation specifically associated with areas containing C. polykrikoides cells. In summary, our results indicate C. polykrikoides blooms have become annual events on eastern Long Island and that bloom waters are capable of causing rapid mortality in multiple species of finfish and shellfish.     

Controls on the initiation and development of blooms of the dinoflagellate Cochlodinium polykrikoides Margalef in lower Chesapeake Bay and its tributaries

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⁻¹) 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 °C 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 °C 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.     

Phylogenetic relationships of Cochlodinium polykrikoides Margalef (Gymnodiniales,Dinophyceae) from the Mediterranean Sea and the implications of its global biogeography

Although the diversity of dinoflagellates has been intensively studied in several locations in the Mediterranean Sea since the 1950s, it is only during the last two decades that the morphotype of the toxic unarmoured dinoflagellate Cochlodinium polykrikoides Margalef has been detected, coinciding with its apparent worldwide expansion in marine coastal waters. In this study, vegetative cells of C. polykrikoides morphotype from the Catalan coast (NW Mediterranean Sea) were detected and isolated, and the DNA from collected cells was sequenced. While in the Mediterranean Sea, detections are scarce and C. polykrikoides is consistently present at low concentrations, we reported exceptional blooms of this species, in which the maximum abundance reached 2 × 10⁴ cells L⁻¹. Partial LSU rDNA region sequences showed that most C. polykrikoides populations from the Catalan coast formed a new differentiated ribotype, but others were included within the ‘Philippines’ ribotype, demonstrating their coexistence in the Mediterranean Sea. Thus, the current biogeographic nomenclature of the ribotypes is likely to be invalid with respect to the available information from populations comprising the ‘Philippines’ ribotype. The phylogeny suggests the existence of cryptic species that should be evaluated for species-level status. Accordingly, the ribotype determination must be carefully evaluated for all detections and bloom events, since accurate characterization of the morphology, ecophysiology and distribution of the ribotypes are not well resolved.     

Long-term changes in Noctiluca scintillans blooms along the Chinese coast from 1933 to 2020

Noctiluca scintillans is one of the most common harmful algal species and widely known due to its bioluminescence. In this study, the spatial distribution, seasonal variations, and long-term trends of N. scintillans blooms in China and the related drivers were analyzed and discussed. From 1933 to 2020, a total of 265 events of N. scintillans blooms were recorded in Chinese coastal waters, with a total duration of 1052 days. The first N. scintillans bloom occurred in Zhejiang in 1933, and only three events were recorded before 1980. From 1981 to 2020, N. scintillans caused harmful algal blooms (HABs) almost every year, both the average duration and the proportion of multiphase HABs showed an increasing trend. 1986–1992, 2002–2004, and 2009–2016 were the three peak periods with a frequency of no less than five events of N. scintillans blooms per year. In terms of spatial distribution, N. scintillans blooms spread from the Southeast China Sea to the Bohai Sea after 2000, Guangdong, Fujian, and Hebei were the three provinces with the highest numbers of recorded events of N. scintillans blooms. Moreover, 86.8% of the events of N. scintillans blooms occurred in spring (March, April, and May) and summer (June, July, and August). Among environmental factors, the dissolved inorganic phosphate, dissolved silicate and chemical oxygen demand were significantly correlated with the cell density of N. scintillans during N. scintillans blooms, and most of N. scintillans blooms were recorded in the temperature range of 18.0–25.0°C. Precipitation, hydrodynamics, water temperature, and food availability might be the main factors affecting the spatial–temporal distribution of N. scintillans blooms along the Chinese coast.     

Emergence of brown tides caused by Aureococcus anophagefferens Hargraves et Sieburth in China

Large-scale blooms suspected to be “brown tides” occurred in early summer for three consecutive years from 2009 to 2011 in the coastal waters of Qinhuangdao, China, and had significant negative impacts on the shellfish mariculture industry. To identify the causative species of the blooms, phytoplankton samples were collected from regions with and without bloom in the coastal waters of Qinhuangdao in 2011, and clone libraries were built using eukaryote-specific 18S ribosomal RNA gene (18S rDNA). Altogether 50 clones, including 17 clones from bloom area and 33 clones from nearby regions without bloom were amplified. Blasted in GenBank, 17 clones amplified from the bloom area were assigned to Pelagophyceae (8 clones), Mediophyceae (2 clones), Cryptophyta (2 clones), Dinophyceae (2 clones) and unidentified eukaryotic species (3 clones). Those from the non-bloom site were assigned to Cryptophyta, Eustigmatophyceae, Prasinophyceae, Coscinodiscophyceae, Mediophyceae, Raphidophyceae and Dinophyceae, but not Pelagophyceae. All 8 pelagophyte clones from the bloom area were 99.7–100% similar to a single species, Aureococcus anophagefferens Hargraves et Sieburth, the causative species of brown tides on the east coast of USA. For nearly the entire length of the 18S rDNA, there were 0–6 base pair differences between the 8 amplicons and those of A. anophagefferens from USA. Furthermore, all of the 8 clones were clustered into the same well-supported clade with A. anophagefferens (posterior probability = 0.99) in a phylogenetic tree established for pelagophytes and other related microalgae. In our previous studies, the causative species of the bloom was tentatively identified as a pelagophyte, haptophyte or silicoflagellate, based on the pigment profile of the size-fractioned phytoplankton samples. Based on this study, we conclude that blooms in the coastal waters of Qinhuangdao of the Bohai Sea were brown tides caused by A. anophagefferens. As far as we know, this is the first report of brown tide events caused by A. anophagefferens in China, which is the third country in the world reporting A. anophagefferens blooms in addition to USA and South Africa.     

Identification of the coastal zone of the central and eastern Gulf of Finland by numerical modeling,measurements, and remote sensing of chlorophyll <Emphasis Type="Italic">a</Emphasis>

A combination of numerical modeling results with measurement and satellite imagery data was used during the biologically active period for the determination of the coastal zone extent in the central and eastern Gulf of Finland. Adopting the approach that the coastal zone can be identified by the spatial distribution of biotic parameters, spatial variations and gradients of chlorophyll a (chl-a) concentrations were analyzed. The results showed that chl-a concentrations vary in a wide range over the biologically active period. During heavy blooms, the coastal zone may appear occasionally and depend on the spatial distribution of the bloom. On average, clear limits of the coastal zone could be defined for the central and eastern Gulf of Finland. In the central Gulf of Finland, water and material exchange are rather intensive, and the coastal zone is narrower than in the eastern Gulf. In the easternmost part of the Gulf of Finland, chl-a concentrations were permanently high in an area of about 100 km width due to the discharge of the Neva River. The study has shown that gradients of chl-a spatial distribution can be applied for determining limits of the coastal zone extent. The standardized gradient of zero is shown to be a threshold separating the coastal zone (standardized gradients > 0) from the open sea (standardized gradients < 0). Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Increased intrusion of warming Atlantic water leads to rapid expansion of temperate phytoplankton in the Arctic

The Arctic Ocean and its surrounding shelf seas are warming much faster than the global average, which potentially opens up new distribution areas for temperate‐origin marine phytoplankton. Using over three decades of continuous satellite observations, we show that increased inflow and temperature of Atlantic waters in the Barents Sea resulted in a striking poleward shift in the distribution of blooms of Emiliania huxleyi, a marine calcifying phytoplankton species. This species' blooms are typically associated with temperate waters and have expanded north to 76°N, five degrees further north of its first bloom occurrence in 1989. E. huxleyi's blooms keep pace with the changing climate of the Barents Sea, namely ocean warming and shifts in the position of the Polar Front, resulting in an exceptionally rapid range shift compared to what is generally detected in the marine realm. We propose that as the Eurasian Basin of the Arctic Ocean further atlantifies and ocean temperatures continue to rise, E. huxleyi and other temperate‐origin phytoplankton could well become resident bloom formers in the Arctic Ocean.     

An extensive Cochlodinium bloom along the western coast of Palawan, Philippines

A massive fish kill and water discoloration were reported off the western coast of Puerto Princesa, Palawan, Philippines in March 2005. Phytoplankton analysis revealed a near monospecific bloom of the dinoflagellate, Cochlodinium polykrikoides, with cell concentrations ranging from 2.5 × 10⁵ to 3.2 × 10⁶ cells per liter. Ground truth data were supplemented by processed satellite images from MODIS Aqua Level 2 data (1 km resolution) from January to April 2005, which revealed high surface chlorophyll-a levels (up to 50 mg/m³) offshore of west and southwest Palawan as early as February 2005. The bloom extended 310 km in length and 80 km in width at its peak in March off the central coast (Puerto Princesa). By April, the bloom declined in intensity, but was still apparent along the northern coast (El Nido). Fluctuations in chlorophyll levels off the western coast of Sabah, Malaysia and Brunei during this time period suggested that the bloom was not limited to the coast of Palawan. Satellite imagery from Sabah in late January revealed a plume of chl-a that is believed to be the source of the C. polykrikoides bloom in Palawan. This plume drifted offshore, advected northward via the basin-wide counterclockwise gyre, and reached nutrient-rich, upwelled waters near Palawan (due to a positive wind stress curl) where the dinoflagellate bloomed and persisted for 2 months from March to April 2005.     

Monitoring Karenia brevis blooms in the Gulf of Mexico using satellite ocean color imagery and other data

Harmful algal blooms (HABs) of Karenia brevis are a recurrent problem in the Gulf of Mexico, with nearly annual occurrences on the Florida southwest coast, and fewer occurrences on the northwest Florida and Texas coasts. Beginning in 1999, the National Oceanic and Atmospheric Administration has issued the Gulf of Mexico HAB Bulletins to support state monitoring and management efforts. These bulletins involve analysis of satellite imagery with field and meteorological station data. The effort involves several components or models: (a) monitoring the movement of an algal bloom that has previously been identified as a HAB (type 1 forecast); (b) detecting new blooms as HAB or non-HAB (type 2); (c) predicting the movement of an identified HAB (type 3); (d) predicting conditions favorable for a HAB to occur where blooms have not yet been observed (type 4). The types 1 and 2 involve methods of bloom detection requiring routine remote sensing, especially satellite ocean color imagery and in situ data. Prediction (types 3 and 4) builds on the monitoring capability by using interpretative and numerical modeling. Successful forecasts cover more than 1000 km of coast and require routine input of remotely sensed and in situ data.The data sources used in this effort include ocean color imagery from the Sea-Viewing Wide Field-of-View Sensor/OrbView-2 satellite and processed using coastal-specific algorithms, wind data from coastal and offshore buoys, field observations of bloom location and intensity provided by state agencies, and forecasts from the National Weather Service. The HAB Bulletins began in coordination with the state of Florida in autumn of 1999 and included K. brevis bloom monitoring (type 1), with limited advisories on transport (type 3) and the detection of blooms in new areas (type 2). In autumn 2000, we improved both the transport forecasts and detection capabilities and began prediction of conditions favorable for bloom development (type 4). The HAB Bulletins have had several successes. The state of Florida was advised of the potential for a bloom to occur at the end of September 2000 (type 4), and the state was alerted to the position of blooms in January 2000 and October 2001 in areas that had not been previously sampled (type 3). These successful communications of HAB activity allowed Florida agencies responsible for shellfish management and public health to respond to a rapidly developing event in a timely, efficient manner.