Influences of temperature, salinity and irradiance on growth of Prorocentrum minimum (Dinophyceae) from the Mediterranean Sea

A Mediterranean clone of the red-tide forming dinoflagellateProrocentrum minimum was studied in vitro for its capacitiesto adapt to salinity, temperature and light. This clone is euryhalineand shows optimal growth between 15 and 35     

Is the invasion of Prorocentrum minimum (Dinophyceae) related to the nitrogen enrichment of the Baltic Sea?

The abundance of the invasive, bloom-forming dinoflagellate Prorocentrum minimum (Pavillard) Schiller and triangular, oval, and oval-round cell shapes were examined relative to salinity, temperature, and nutrient concentrations at the selected sites in the Baltic Sea. Based on the multiple regression and multivariate statistical analysis, all cell shapes of P. minimum had highly similar distribution relative to these environmental parameters as well as chlorophyll-a, nitrite + nitrate, ammonium, total nitrogen, phosphate, total phosphorus, and silicate. The species was related positively to total nitrogen, and negatively to salinity, temperature, nitrite + nitrate, and silicate:total nitrogen ratio. The results suggest that P. minimum could well adapt to low salinity and temperature and occurred particularly in coastal waters, rich in total nitrogen relative to silicate or other inorganic nutrients. These results indicate that the recent invasion of P. minimum into the Baltic Sea could have been enhanced by the DON enrichment. The results also support the suggestion that P. minimum is one morphospecies with no distinct subtaxa.     

Growth and bioluminescence of Noctiluca scintillans on varying algal diets

The effects of food concentration and food quality on the growthrate and bioluminescence potential of the heterotrophic dinoflagellateNoctiluca scintillans were examined. The growth rate of N. scinullansvaried greatly with the phytoplankton food it was provided,and those foods yielding higher growth rates also produced cellsthat were smaller in diameter, but with a greater bioluminescencepotential per unit volume. Small phytoplankton species, includingIsochrysis galbana and an unidentified chrysophyte responsiblefor the Texas brown tide, supported the lowest growth rates.Other small flagellates (Dunaliella tertiolecta) and dinoflagellates(Gyrodinium dorsum, Prorocentrum minimum) supported moderategrowth rates. The highest growth rates were supported by diatomsand prasinophytes. Maximum growth rates (0.5 day^-1) were obtainedwith the diatom Thalassiosira sp. at concentrations     

The correct position of flagellar insertion in Prorocentrum and description of Prorocentrum rhathymum sp. nov. (Pyrrhophyta)

For three Prorocentrum species, P. minimum (Pavillard) Schiller,P. rhathymum sp. nov., and P. triestinum Schiller, we have foundthat both flagella emerge from a single large pore. This arrangementis contrary to previous observations which suggested they arosefrom separate pores. Prorocentrum triestinum has only one anteriorpore, whereas P. minimum and P. rhathymum sp. nov. have an additionalauxiliary pore. The pores in all three species are formed bya series of small plates. The left and right valves on eachspecies can be identified by ornamentation unique to each valve.Prorocentrum rhathymum sp. nov., isolated from the planktonof Cinnamon Bay, Virgin Islands, is described. ² The Biological Laboratories, Harvard University, Cambridge,Massachusetts 02138 ³ Department of Botany, Duke University, Durham, North Carolina27706     

Characteristics of fluctuations in salinity and water quality in brackish Lake Obuchi

Fluctuations in the salinity and physicochemical characteristics of water quality were surveyed in brackish Lake Obuchi on the Shimokita Peninsula in Aomori, Japan. The mean salinity in the surface layer in all regions of Lake Obuchi was about 10 psu, whereas in the basin region at depths of greater than 3 m it was 20 psu. Furthermore, all the year round the halocline was formed at depths of 1–4 m. The maximum density gradient along a vertical axis in the center of the lake was observed at depths of 1–2 m in summer and 2–4 m in spring and fall. The depth of the maximum density gradient fluctuated with the seasons. In summer the water in the bottom layer was anoxic, and Fe, Mn, PO₄ ³⁻-P, and NH₄ ⁺-N supplied from the bottom sediment accumulated at high concentrations below the halocline. Thus, it was observed that the transfer of substances between the layers above and below the barrier formed by the halocline is suppressed. Although Lake Obuchi is small and shallow, the inflowing seawater easily resides, and a stable halocline readily forms because of the shape of its basin, which suddenly deepens on the Pacific Ocean side. Received: May 24, 1999 / Accepted: September 25, 1999     

Ecological niche partitioning of the invasive dinoflagellate Prorocentrum minimum and its native congeners in the Baltic Sea

This study analyses three decades of the peculiar bloom-formation history of the potentially toxic invasive planktonic dinoflagellates Prorocentrum minimum (Pavillard) Schiller in the SW Baltic Sea. We tested a research hypothesis that the unexpectedly long delay (nearly two decades) in population development of P. minimum prior to its first bloom was caused by competition with one or several closely related native dinoflagellate species due to ecological niche partitioning which hampered the spread and bloom-forming potential of the invader. We applied the ecological niche concept to a large, long-term phytoplankton database and analysed the invasion history and population dynamics of P. minimum in the SW Baltic Sea coastal waters using the data on phytoplankton composition, abundance and biomass. The ecological niche dimensions of P. minimum and its congener P. balticum were identified as the optimum environmental conditions for the species during the bloom events based on water temperature, salinity, pH, concentration of nutrients (PO₄³⁻; total phosphorus, TP; total nitrogen, TN; SiO₄⁴⁻), TN/TP-ratio and habitat type. The data on spatial distribution and ecological niche dimensions of P. minimum have contributed to the development of the “protistan species maximum concept”. High microplankton diversity at critical salinities in the Baltic Sea may be considered as a possible reason for the significant niche overlap and strong competitive interactions among congeners leading to prolonged delay in population growth of P. minimum preceding its first bloom in the highly variable brackishwater environment.     

Relationship between functional response and gut transit time in the calanoid copepod Acartia clausi: role of food quantity and quality

The relationship between ingestion rate and gut transit timeof the calanoid copepod Acartia clausi was examined in laboratoryexperiments with five different diets: (i) living cells of thediatom Thalassiosira weissflogii, (ii) detrital cells of thesame diatom, (iii) 50:50 mix of the two previous diets on aprotein basis, (iv) dinoflagellate cells of Prorocentrum micansand (v) Prorocentrum minimum. Ingestion followed a Holling type2 response for diets 1 and 4 and a linear one for diets 2, 3and 5. Gut transit time varied with food abundance only whenthe copepods were fed with the living diatom. The gut evacuationrate increased with the concentration of T. weissflogii withvalues of 0.010, 0.020, 0.032, 0.042 min^–1, correspondingto gut transit time of 97, 50, 31 and 24 min, measured at 50,110, 130 and 275 µg protein L^–1, respectively. Copepodsfed with dinoflagellates, mixed and pure detrital diets exhibitedlonger and similar gut transit times ranging from 85 to 166min, depending on diet. The coupling between ingestion rateand gut transit time measurements is discussed in the contextof copepod feeding strategies.     

ECTOCELLULAR GLUCOSIDASE AND PEPTIDASE ACTIVITY OF THE MIXOTROPHIC DINOFLAGELLATE PROROCENTRUM MINIMUM (DINOPHYCEAE)1

The activities of the enzymes α‐ and β‐glucosidase, and leucine aminopeptidase were measured in cultures of the dinoflagellate Prorocentrum minimum (Pavill.) J. Schiller and in field samples collected during dinoflagellate blooms occurring in tributaries of the Chesapeake Bay, Maryland, USA. Activities were measured using fluorogenic artificial substrates and partitioned among the >5 μm size fraction, small microbes fraction (0.1–5 μm), and dissolved phase (<0.1 μm). P. minimum and most other photosynthetic dinoflagellates are >5 μm in size and thus can be separated from the small microbes fraction, which contains most bacteria. Little to no glucosidase activity was detected associated with the >5 μm size fraction in cultures or in field samples, with most of the activity (67% to 93% in cultures, 54% to 100% in field samples) in the small microbes size fraction for both α and β glucosidase. In contrast, 67% to 90% of the total leucine aminopeptidase (LAP) activity in cultures was measured in the >5 μm fraction. Within a culture, LAP activity in the size fraction containing P. minimum decreased in response to ammonium and urea additions, but not in response to nitrate. In field samples, LAP activity was positively correlated with dinoflagellate abundance and chl a, and negatively correlated with ammonium concentration. During blooms, up to 34% of LAP activity was associated with the >5 μm fraction, indicating that when abundant, dinoflagellates may make a substantial contribution to ectocellular LAP activity in the water column.     

Spatial and temporal patterns of phytoplankton composition in subtropical coastal lagoon, the Indian River Lagoon, Florida, USA

A 2 year study of the phytoplankton community was carried outin the Indian River Lagoon, USA. In terms of biovolume, thephytoplankton community was generally dominated by dinoflagellates,diatoms or cyanobacteria. Mean phytoplankton standing cropswere highest in the most flow-restricted regions of the lagoon,which had the lowest mean salinity values and comparativelyhigh total nitrogen:total phosphorus ratios. In this region,blooms of dinoflagellates were common in the first year of thestudy, which was characterized by an El Niño event thatyielded exceptionally high rainfall levels and freshwater outflow.Picoplanktonic cyanobacteria blooms became more prominent inthe second year of the study, which was characterized by belowaverage rainfall conditions. In unrestricted flow regions ofthe lagoon, located near inlets to the Atlantic Ocean, diatomswere most often the dominant taxa. Regions of intermediate waterturnover rates and high external loading of phosphorus had aprevalence of diatom blooms. However, the average phytoplanktonstanding crops in the latter regions did not reach the levelsexperienced in the flow-restricted parts of the lagoon. In termsof individual phytoplankton taxa, the most common bloom-formingdiatoms in the Indian River Lagoon system included: Skeletonemacostatum, Dactyliosolen fragilissimus, Skeletonema menzelii,Cerataulina pelagica, Odontella regia, Chaetoceros lorenzianus,Rhizosolenia setigera and Thalassionema nitzschioides. The majorbloom-forming dinoflagellate species included: Pheopolykrikoshartmannii, Akashiwo sanguinea, Prorocentrum micans, the potentiallytoxic species Pyrodinium bahamense var. bahamense and Prorocentrumminimum. Several picoplanktonic cyanobacteria were also prominentmembers of the phytoplankton community, including Synechococcuselongates. The spatial and temporal patterns observed in someof these dominant species were attributable to patterns in keyenvironmental variables, including salinity, temperature andnutrient concentrations.     

INTERSPECIFIC VARIATION IN DARK NITROGEN UPTAKE BY DINOFLAGELLATES1

Seven species of marine dinoflagellates were grown in nitrogen-sufficient media under a 12:12 h L:D cycle, and then tested for their ability to take up nitrate and ammonium in the light and in the dark in short-term experiments with ¹⁵N-labelled substrate. The effect of the N substrate chosen, and the effect of sampling time in the L:D cycle, on the relative nitrogen content (the C:N ratio) was investigated at the same time. The physiological extremes in the material were represented by Prorocentrum minimum (Pav.) J. Schiller, which took up and presumably assimilated nitrate equally fast in the light and in the dark, and Gyrodinium aureolum Hulburt, which did not take up nitrate in the dark when in a state of nitrogen sufficiency. A strong coupling between nitrate assimilation and photosynthetic carbon assimilation in the latter species was suggested by the close similarity of the light saturation curves of ¹⁵NO₃^? and ¹⁴CO₂ incorporation, and by a complete blocking of ¹⁵NO₃^? incorporation by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Nitrogen starvation for 24 h induced a capacity in G. aureolum for taking up nitrate in the dark, or in the light in the presence of DCMU, a phenomenon that might be useful for identifying nitrogen limitation in this species in the field. Our study emphasizes the variability of dinoflagellate nitrogen nutrition and illustrates the difficulty of associating mass occurrences of dinoflagellates in nature with any particular nutritional mode.     

Changes in the phytoplankton community of a coastal,hyposaline lake in western Anatolia,Turkey

The phytoplankton composition of coastal, hyposaline (≅12 g l⁻¹) Lake Bafa in western Turkey, was investigated after the alteration of salinity levels in past decades. Lake Bafa, formerly a bay of the Aegean Sea, was separated from the sea as a result of alluvium deposits of the Meander River. After the construction of a sett for flood control in 1985, freshwater inflow was reduced and salinity increased, which caused some ecological changes. Phytoplankton samples were taken in August and November 2000, and February and May 2001, from the surface and at 5-m intervals in the water column at three stations. The phytoplankton community contained a mixture of freshwater and marine origin species. A total of 45 species from Bacillariophyceae, Chlorophyceae, Cyanophyceae, Chrysophyceae, and Dinophyceae were identified. Marineoriginated species such as Chaetoceros spp. (November and May), Thalassionema nitzschioides and Prorocentrum micans (August and November), and P. minimum (May) were dominant on the basis of numerical abundance. The occurrence of salinity-tolerant species such as T. nitzschioides, P. micans, and P. minimum has not been recorded in previous studies.     

Prorocentrum minimum (Dinophyceae) in the Baltic Sea: morphology, occurrence—a review

The potentially toxic dinoflagellate Prorocentrum minimum (Pavillard) Schiller has successfully established in the Baltic Sea in the last two decades. A review of the invasion history is presented as well as new data on the spatial and inter-annual variability of this species and its relation to salinity, temperature, and nutrient concentrations. A short literature review of the morphological characters of the Baltic P. minimum is also included.From 1993 to 2002, P. minimum was a regular component of the summer and autumn plankton flora of the Baltic Sea proper and the Gulf of Finland. Its abundance varied considerably inter-annually and did not show any clear trends during the period. Abundance of P. minimum was significantly higher in the nutrient-enriched Bay of Mecklenburg (German coast) and the southern Baltic proper than in the central and northern Baltic proper and the Gulf of Finland, where its abundance was mostly sparse. In coastal waters P. minimum occasionally reached densities of several million cells per litre and dominated phytoplankton biomass (>90%).Abundance of the Baltic P. minimum was generally not related to salinity or temperature. It could be a dominant species at both high and low salinity (over 15 and 4.8 PSU), and its temperature range was broad (from 2.7 to 26.4 °C). However, dense populations usually occurred from July to October at temperatures above 10 °C.Further, there appears to be a positive correlation between the success of P. minimum in the Baltic Sea and high concentrations of total phosphorus and nitrogen.This tolerant and morphologically variable dinoflagellate seems to be a morphospecies without subtaxa, which can expand its range in the Baltic Sea, especially in nutrient-rich coastal waters.     

Evidence of a new toxin in the red-tide dinoflagellate Prorocentrum minimum

Several clones of Prorocentrum minimum were isolated from variousFrench Mediterranean and English Channel sites. Mouse testsperformed using methanolic extracts from cultures revealed aneurotoxic activity in four clones. The water-soluble toxindetected worked rapidly, killing mice within a few minutes athigh doses. Toxin production in cultures was observed duringthe phase of decline and appeared to be weak or nil during thegrowth phase. Toxin production was stimulated by associatedbacteria in the culture, but a clone rendered axenic remainedable to produce toxins. The potential risks of human poisoningfrom consumption of shellfish harvested during or after toxicblooms of P.minimum are discussed.     

Free-living dinoflagellates in the southern Gulf of Mexico: Report of data (1979–2002)

The present study is a report of data of planktonic dinoflagellates which includes a list of 252 species, with 10 985 entries in the southern Gulf of Mexico along with information concerning their occurrence. Material for the present study consists of water and net samples obtained during 11 cruises collected at 608 sites between June 1979 and December 2002. Ceratium (47 spp.), Protoperidinium (28 spp.), Dinophysis (26 spp.), Oxytoxum (19 spp.) and Prorocentrum (15 spp.) were the most diverse genera. The most common species found are Ceratium breve, Ceratium contortum, Ceratium furca, Ceratium furca var. eugranum, Ceratium fusus. Ceratium fusus var. seta, Ceratium kofoidii, Ceratium macroceros, Ceratium massiliense, Ceratium pentagonum, Ceratium teres, Ceratium trichoceros, Ceratium tripos, Dinophysis caudata, Ornithocercus magnificus, Podolampas palmipes, Prorocentrum com‐pressum, Prorocentrum gracile, Prorocentrum micans, Protoperidinium divergens and Pyrophacus steinii. Thirteen species are potential toxin producers, among which Karenia brevis was responsible for fish mass mortalities. Other toxic species such as Amphidinium carterae, Dinophysis acuta, Dinophysis caudata, Dinophysis fortii, Dinophysis mitra, Dinophysis rotundata, Dinophysis tripos, Prorocentrum mexicanum, Prorocentrum micans and Prorocentrum minimum were present mostly in net samples. The non‐toxic species Ceratium furca, Pyrodinium bahamense var. bahamense, Scripp‐siella trochoidea and Gonyaulax polygram ma were found in blooms during the summer. Qualitative data show that dinoflagellates occurred mostly during July and August, associated with hydrographic conditions. A checklist of the species and their occurrence are given.     

Growth of harmful marine algae in multispecies cultures

Mixtures of harmful and harmless algae were grown in discontinuouslydiluted batch cultures under ammonium, nitrate and phosphatelimitation, and at different irradiances (20–500 µjnolquanta m^–2 s^–1). The species used were Chrysochromulinapolylepis, Emiliania huxleyi type B, Rhodomonas sp., the dinoflagellalesFibrocapsa japonica, Gymnodinium simplex, Gyrodinium aure-olum,Heterocapsa triquetra, Heterosigma carterae, Prorocentrum micansand Alexandrium tamarense, the diatoms Chaetoceros socialis,Cymatosira belgica, Ditylum brightwellii, Laudcria borealis,Odon-telta aunla, Pseudonitzschia pungens, Streptotheca tamesis,and the cyanobacterium Synechococcus. Their growth responsein the mixed algal cultures is discussed in relation to theirabundance in different natural habitats. In comparison withthe other non-diatoms, the mixotrophic C.polylepis grew fastunder all tested nutrient and light limitations.Emiliania huxleyigrew well under nitrogen (N) limitation (with nitrate as N source)and at irradiance levels from 15 up to 500 µmol quantam^–2 s^–1. No growth of calcifying cells could bedetected under N limitation when ammonium was used as N source.Rhodomonas grew reasonably well under ammonium-N limitationand grew fast at the highest irradi-ance. The dinoflagellateswere poor competitors compared to the Prymnesiophyceae. Theenvironmental fitness of the Prymnesiophyceae appears to beclosely related to the reproductive capacity of the vegetativestage, whereas the natural distribution of dinoflagellates seemsmore closely dependent on the generative reproduction-relatedspecific life cycle characteristics of the individual species.The marine diatoms include a mixture of both types of species.Some marine diatom species clearly have the capability to outcompetenon-diatoms under different types of nutrient and light limitationswhen silicate is in excess. Other diatoms seem to be poor competitors.     

Growth and competition of several harmful dinoflagellates under different nutrient and light conditions

Three near-shore type harmful dinoflagellates, Prorocentrum minimum, Prorocentrum donghaiense and Karlodinium veneficum, and one off-shore dinoflagellate, Karenia brevis, were grown in laboratory monocultures and mixed batch cultures. The dinoflagellate cultures were grown on treatments of two ambient nitrogen (N):phosphorus (P) ratios; two N substrates (nitrate and urea) and two light intensities. The microalgae Rhodomonas and Synechococcus were also added in separate treatments to the mixed culture treatments as potential food sources. All tested species grew well on both N substrates. In mixed culture, P. minimum outgrew K. veneficum, and P. donghaiense outgrew K. brevis in most treatments reaching higher growth rates and higher biomass. However, when a third algae, Rhodomonas, was added, the growth of P. minimum was inhibited relative to that of K. veneficum. In contrast, when grown with K. brevis, the growth rate of P. donghaiense was not significantly affected by the addition of potential prey. K. brevis had a longer growth phase, and kept growing after P. donghaiense reached stationary phase, suggesting better adaptation of K. brevis to low inorganic nutrient conditions. The growth of K. brevis was also significantly limited in the low light treatment. K. veneficum overgrew P. minimum in the presence of Rhodomonas, a potential nutrient source. The growth rates of both K. brevis and P. donghaiense were reduced with the presence of Synechococcus. In addition to nutrient competition, mixotrophy and allelopathy were likely mechanisms in determining the dominant species.     

Dynamics of potentially harmful microalgae in a confined Mediterranean Gulf—Assessing the risk of bloom formation

The population dynamics of potentially harmful microalgae was investigated in the semi-enclosed shallow Gulf of Kalloni, Greece (Aegean Sea, Eastern Mediterranean), during a 2-year period from August 2004 to March 2006. A total of 21 potentially harmful microalgae (bloom-forming and/or toxic) were identified including 3 diatoms and 18 dinoflagellates. The densities of each species were analyzed in time and space and in relation to environmental parameters. Some species such as Alexandrium insuetum, Heterocapsa circularisquama, Karlodinium veneficum, Scrippsiella trochoidea, and Ceratium spp. developed high cell concentrations, particularly during a Pseudo-nitzschia calliantha winter bloom. Other species such as Dinophysis caudata, Ostreopsis ovata, Prorocentrum minimum, and Protoperidinium crassipes were rare or appeared in small numbers. Densities of the most abundant species were closely associated with freshwater nutrient-rich inputs during winter, being negatively correlated with temperature and salinity and positively correlated with nitrogen. The spatial distribution of the abundant species exhibited a marked increase towards the inner part of the gulf, close to the main freshwater inputs, whereas some species were mainly concentrated in the dilute surface layer (1 m depth). Examination of the abundance–occupancy relationship revealed that the species more prone to bloom are those with wide spatial distribution and frequent presence throughout the year such as the diatom P. calliantha. Although blooms of cyst-forming species are rarer, an increased risk can be foreseen under favorable resource supply and environmental conditions during winter.     

Tidally driven distribution of phytoplankton blooms in a shallow, macrotidal estuary

The influence of the ebb tide on the abundance and distributionof bloom-forming species, as well as the mechanisms for theselection of those species which remain, were investigated inthe shallow, tidal-flushed Urdaibai estuary, north Spain. Phytoplanktonwas collected monthly from May to September 1998 during differenttidal conditions (neap-spring) at five stations along the salinitygradient of the estuary. During the neap tides of May, Leptocylindrusdanicus dominated in the lower estuary, together with Thalassiosiraguillardii and Peridinium foliaceum in the upper segment; T.guillardiiexperienced the broadest displacement along the estuary. Duringthe June and July cruises, coinciding with mid-tidal amplitudesand high temperatures, Peridinium quinquecorne densely aggregatedin the upper estuary at the slack high tide, whereas Chaetocerossalsugineum bloomed at the intermediate stations. Cyclotellaatomus and Protoperidinium achromaticum reached high concentrationsin the upper zone only during the late stages of the ebb. Duringthe spring tides of September, Prorocentrum minimum, Heterocapsapygmaea and Heterocapsa rotundata appeared in the lower marineestuary, being washed out at low tide. By contrast, the diatomsSkeletonema costatum, Thalassiosira guillardii and Cyclotellaatomus were the most abundant species in the upper reaches,peaking during the ebb. Physical trapping and high water residencetimes served to retain blooming species in the upper estuary.The intense growth of the estuarine diatoms may compensate forthe advective seaward losses of cells during the ebb, thus allowingthe development of stable populations in the estuary. Only Peridiniumquinquecorne seems to combine an endogenous tidal rhythm witha photic response to remain in the tidal area of the estuary.     

An Ultrastructural Study of Mitosis in a Marine Dinoflagellate: Prorocentrum minimum1

An ultrastructural study on mitosis in the marine dinoflagellate Prorocentrum minimum is described. Early in mitosis the nuclear membrane invaginates in the area of the Golgi apparatus. Additional membrane-lined channels form within the nucleus as the Golgi apparatus separates and moves toward opposite spindle poles. Microtubules appear within the channels and make contact with distinct kinetochore-like structures on the cytoplasmic side of the channels adjacent to the site of chromosome attachment. By mid-mitosis two or three parallel channels dissect the nucleus perpendicular to the suture plane of the cell. Chromosome separation thus occurs perpendicular to the suture plane. An additional group of microtubules extends posteriorly from the flagellar apparatus towards the nucleus but has no apparent role in mitosis. Mitosis in P. minimum is compared to that of P. micans and to other dinoflagellates.     

Sampling harmful benthic dinoflagellates: Comparison of artificial and natural substrate methods

This study compared two collection methods for Gambierdiscus and other benthic harmful algal bloom (BHAB) dinoflagellates, an artificial substrate method and the traditional macrophyte substrate method. Specifically, we report the results of a series of field experiments in tropical environments designed to address the correlation of benthic dinoflagellate abundance on artificial substrate and those on adjacent macrophytes. The data indicated abundance of BHAB dinoflagellates associated with new, artificial substrate was directly related to the overall abundance of BHAB cells on macrophytes in the surrounding environment. There was no difference in sample variability among the natural and artificial substrates. BHAB dinoflagellate abundance on artificial substrates reached equilibrium with the surrounding population within 24 h. Calculating cell abundance normalized to surface area of artificial substrate, rather than to the wet weight of macrophytes, eliminates complications related to the mass of different macrophyte species, problems of macrophyte preference by BHAB dinoflagellates and allows data to be compared across studies. The protocols outlined in this study are the first steps to a standardized sampling method for BHAB dinoflagellates that can support a cell-based monitoring program for ciguatera fish poisoning. While this study is primarily concerned with the ciguatera-associated genus Gambierdiscus, we also include data on the abundance of benthic Prorocentrum and Ostreopsis cells.