Abundance Of Dinoflagellates Research Articles

Factors regulating primary producers' assemblages in Posidonia oceanica (L.) Delile ecosystems over the past 1800 years

Posidonia oceanica (L.) Delile meadows are highly productive coastal marine ecosystems that provide multiple ecosystem services. The seagrass is not always the major contributor to total primary production, however, little is known about long-term changes in the composition of primary producers within seagrass meadows. Understanding compositional shifts within the community of primary producers is crucial to evaluate how climate and anthropogenic change affect the functioning of seagrass ecosystems. Here we analysed marker pigment composition in seagrass cores from two bays of the Cabrera Island (Balearic Islands, Spain) to asses long-term changes in phototrophic community composition and production in seagrass meadows, and identify the environmental factors triggering those changes. The proxy dataset was explored using principal component analyses (PCA): one including the pigment dataset to look for associations between producers' groups, and another one combining the pigment dataset with plausible local and global regulatory factors to assess the environmental drivers of change. Analyses of characteristic pigments and morphological fossils (cysts) showed that the abundance of dinoflagellates increased over the last 150–300 years, coeval with a rise in solar irradiance and air temperature. When compared among embayments, pigments from cyanobacteria predominated in seagrass meadows located at Es Port, a sheltered bay receiving higher terrestrial runoff; whereas pigments from diatoms, seagrasses and rodophytes were more common at Santa Maria, an exposed bay with clearer waters. Water depth also played a role in controlling the phototrophic community composition, with greater abundance of diatoms in the shallowest waters (<5 m). Overall, our results suggested that historical and spatial variation in seagrass meadows' phototrophic community composition was influenced by the interaction between local factors (catchment-bay characteristics) and global climate processes (energy influx). Together these patterns forecast how marine primary producers and seagrass ecosystem structure may respond to future global warming.

Distribution and potential toxicity of benthic harmful dinoflagellates in waters of Florida Bay and the Florida Keys

Few studies have been carried out on benthic dinoflagellates along the Florida Keys, and little is known about their distribution or toxicity in Florida Bay. Here, the distribution and abundance of benthic dinoflagellates was explored in northern and eastern Florida Bay and along the bay and ocean sides of the Florida Keys. Isolates were brought into culture and their toxicity was tested with oyster larvae bioassays. Seven genera were detected, including Prorocentrum, Coolia, Ostreopsis, Amphidinium, Gambierdiscus, Fukuyoa (all included potentially toxic species) and Sinophysis. In general, distribution increased with water temperature and nutrient availability, especially that of phosphate. This study documented the first record of Coolia santacroce in the Florida Keys.Potential toxic effects of Gambierdiscus caribaeus, the abundance of which exceeded 1000 cells g−1 fw at some sites, were established using oyster larvae as a bioassay organism. These findings suggest a potential risk of ciguatera fish poisoning in this area.

Abundance and reproduction variables of two species of harpacticoid copepods along an increasing salinity gradient

Spatial and temporal complexities of reproductive behaviour and sex ratios of two harpacticoid species Canuella perplexa Scott T. & Scott A., 1893 and Bryocamptus sp. were evaluated monthly from September 2007 to August 2008. Collections were made from four ponds at different salinities in the solar saltern of Sfax, Tunisia, considering other environmental features as well. The salinities ranged from 38.0 to 86.1 psu. With rising salinity, the abundance of C. perplexa adults declined from 4550 ± 4160 ind m−3 (pond A1, salinity = 41.5 ± 2.3 psu) to 880 ± 780 ind m−3 (pond C31, salinity = 71.0 ± 4.3 psu). The abundance of Bryocamptus sp. adults increased from 3560 ± 2810 ind m−3 (A1) to 10,080 ± 6890 ind m−3 (C31). The abundance of total adults of C. perplexa was negatively correlated with both salinity (r = − 0.441, n = 18, p < 0.05) and abundance of dinoflagellates (r = − 0.291, n = 18, p < 0.05) and positively correlated with suspended matter (r = 0.389, n = 18, p < 0.05), temperature (r = 0.354, n = 18, p < 0.05), and abundance of diatoms (r = 0.410, n = 18, p < 0.05). The abundance of adults of Bryocamptus sp. displayed only a positive correlation with salinity (r = 0.452, n = 18, p < 0.05). In both species, the sex ratio (males/females) was driven by the variability of female abundance but never exceeded 1.0. For C. perplexa, the egg number per female ranged between 28 and 31; the ovisac length was between 0.39 ± 0.002 and 0.45 ± 0.018 mm. The egg diameter ranged from 0.062 ± 0.001 to 0.065 ± 0.002 mm, and the total length of ovigerous females ranged between 1.2 and 1.35 mm. For Bryocamptus sp., the egg number per female ranged between 19 and 22, the ovisac length between 0.28 ± 0.008 and 0.31 ± 0.003 mm, the egg diameter between 0.041 ± 0.001 and 0.044 ± 0.001 mm, and the total length of ovigerous females between 0.6 and 0.74 mm. The outcome of this study demonstrated that under extreme environmental conditions and increasing salinity the percentage of diatoms and dinoflagellates was found to be an essential factor in controlling the abundance and reproduction traits of both harpacticoids in this study. Furthermore, the sex ratios in these harpacticoid populations are complex as many factors can influence and alter the sex ratios in natural populations.

RELATIONSHIP OF ORGANIC MATERIAL WITH ABUNDANCE OF TOXIC BENTHIC DINOFLAGELLATA ON SEDIMENT IN WATERS OF TELUK BAKAU VILLAGE BINTAN REGENCY, RIAU ISLAND PROVINCE

Dinoflagellata was included in one of microalgae groups which are on waters of the sea and the river, it can be found on detritus floats, sediments, and also swim freely. This research done on May – June 2018 at waters of the mangrove bay village, Bintan Regency, Riau Island Province. The aims of this research was to know relationship between organic material concentration toward abundance of toxic benthic dinoflagellata on sediment. In addition, to analyzed organic material concentratin and amount of abundance of toxic benthic dinoflagellata on sediment in waters of Teluk Bakau. The method used was survey method which is the location of sampling is done by pursosive sampling. Measurement of water quality sampling done at any point, the surface water temperature range 31-33oC, 28-31 ‰ salinity, pH 8-9 and the current speed from 0.045 to 0.051 m / det.Perairan predominantly sandy gravel sediments, making an average of organic materials ditemukn at each station is 0.027%, 0.043%, 0.033%, 0.024%. The result of this research found 3 genus of toxic dinoflagellata, which are Prorocentrum, Gambierdiscus, and Ostreopsis. Poisonous dinoflagelatta can produced a several types of toxic that found the sea. The highest of abundance found at station 2 on 75,615 sel/m2 and the lowest found at station 1 on 35,176 sel/m2. the results of simple linear regression analysis the relationship between the concentration of organic material with the abundance of dinoflagellates has a positive relationship with the regression equation y = 32,913 + 556,13x

Composition and abundance of benthic microalgae from the Estuarine Complex of Paranaguá Bay (southern Brazil) with special emphasis on toxic species

Abstract This study addressed the occurrence and distribution of benthic microalgae, with emphasis on toxic species, on different substrates (macroalgae, seagrass and sediments) along the outer, euhaline zone of the Estuarine Complex of Paranagua Bay, southern Brazil, from July 2015 to May 2016. Canonical analysis of principal coordinates (CAP) was used to identify the potential environmental drivers of microphytobenthic assemblage structure. A total of 18 potentially toxic benthic microalgae species were reported, including 7 dinoflagellates, 9 cyanobacteria, one diatom and one euglenophyte. The abundance of all potentially toxic microalgae varied consistently along the investigated period. Dinoflagellates dominated the microalgae assemblage in July and September 2015. Mean densities on macrophytes ranged from 33.6 cells g-1 in May 2016 to 775.6 cells g-1 in September 2015, being positively correlated with dissolved nitrogen-nutrients, water transparency, salinity, and chlorophyll-a. Prorocentrum cf. lima was the most frequent and abundant dinoflagellate. Overall, the highest abundance of toxic species occurred in February 2016, when cyanobacterial mats dominated by Lyngbya cf. aestuarii were observed throughout the estuary associated with periods of heavier rainfall and higher turbidity (shallower Secchi depth). At that time, a selected microphytobenthic extract exhibited acute toxicity on nauplii of the brine shrimp Artemia salina in the laboratory.

Variability of dinoflagellates and their associated toxins in relation with environmental drivers in Ambon Bay, eastern Indonesia

The aim of the present work was to unravel which environmental drivers govern the dynamics of toxic dinoflagellate abundance as well as their associated paralytic shellfish toxins (PSTs), diarrhetic shellfish toxins (DSTs) and pectenotoxin-2 (PTX2) in Ambon Bay, Eastern Indonesia. Weather, biological and physicochemical parameters were investigated weekly over a 7-month period. Both PSTs and PTX2 were detected at low levels, yet they persisted throughout the research. Meanwhile, DSTs were absent. A strong correlation was found between total particulate PST and Gymnodinium catenatum cell abundance, implying that this species was the main producer of this toxin. PTX2 was positively correlated with Dinophysis miles cell abundance. Vertical mixing, tidal elevation and irradiance attenuation were the main environmental factors that regulated both toxins and cell abundances, while nutrients showed only weak correlations. The present study indicates that dinoflagellate toxins form a potential environmental, economic and health risk in this Eastern Indonesian bay.

Occurrence of epibenthic dinoflagellates in relation to biotic substrates and to environmental factors in Southern Mediterranean (Bizerte Bay and Lagoon, Tunisia): An emphasis on the harmful Ostreopsis spp., Prorocentrum lima and Coolia monotis

Harmful events associated with epibenthic dinoflagellates, have been reported more frequently over the last decades. Occurrence of potentially toxic benthic dinoflagellates, on the leaves of two magnoliophytes (Cymodocea nodosa and Zostera noltei) and thalli of the macroalgae (Ulva rigida), was monitored over one year (From May 2015 to April 2016) in the Bizerte Bay and Lagoon (North of Tunisia, Southern Mediterranean Sea). The investigated lagoon is known to be highly anthropized. This is the first report on the seasonal distribution of epibenthic dinoflagellates hosted by natural substrates, from two contrasted, adjacent coastal Mediterranean ecosystems. The environmental factors promoting the development of the harmful epibenthic dinoflagellates Ostreopsis spp., Prorocentrum lima and Coolia monotis were investigated. The highest cell densities were reached by Ostreopsis spp. (1.9 × 103 cells g−1 FW, in October 2015), P. lima (1.6 × 103 cells g−1 FW, in June 2015) and C. monotis (1.1 × 103 cells g−1 FW, in May 2015). C. nodosa and Z. noltei were the most favorable host macrophytes for C. monotis (in station L2) and Ostreopsis spp. (in station L3), respectively. Positive correlations were recorded between Ostreopsis spp. and temperature. Densities of the epibenthic dinoflagellates varied according to the collection site, and a great disparity was observed between the Bay and the Lagoon. Maximum concentrations were recorded on C. nodosa leaves from the Bizerte Bay, while low epiphytic cell abundances were associated with macrophytes sampled from the Bizerte Lagoon. The observed differences in dinoflagellate abundances between the two ecosystems (Bay-Lagoon) seemed not related to the nutrients, but rather to the poor environmental conditions in the lagoon.

Long-Term Phytoplankton Dynamics in a Complex Temporal Realm

Faced with an environment of accelerated change, the long-term dynamics of biotic communities can be approached to build a consistent and causal picture of the communities’ life. We have undertaken a 25-year monthly-sampling study on the phytoplankton of a meso-oligotrophic lake, paying attention to controlling factors of overall biomass (TB) and taxonomical group biomass (TGBs). Long-term series included decreased trends of TB and TGBs, and multi-scale periodicity. A decadal TB periodicity emerged related to nitrogen concentration and Cryptophytes. Annual periodicities were mainly related to air and water temperature controlling the abundance of Chlorophytes or Dinoflagellates. Intra-annual cycles could arise from autogenic processes. The analysis by periods revealed relevant dynamics (for example, Diatom periodicities), hidden in the analysis of the complete series. These results allow us to establish that: i) two organizational levels of phytoplankton change differently in time scales from months to decades; ii) controlling factors (climate, water physics and chemistry) act at different time scales and on different TGBs, and iii) different combinations of the “taxonomical group-control factor-trend and periodicity” set throughout the studied time explain total biomass dynamics. A holistic approach (multiple complementary analyses) is necessary to disentangle the different actors and relationships that explain non-stationary long-term phytoplankton dynamics.

Microalgal blooms in a eutrophic estuary (Golden Horn, Sea of Marmara) following a remediation effort

Abstract The present work describes microalgal blooms that occurred in a eutrophic estuary (Golden Horn, Sea of Marmara, Turkey) between October 2013 and September 2014 following a remediation effort. The relationships between bloom-forming microalgal species and environmental factors were investigated during the study period. The changing environmental conditions (e.g. increasing water transparency and salinity) after seawater transfer to the Golden Horn Estuary stimulated phytoplankton growth with dense algal blooms. Annual average values of Secchi depth, salinity and dissolved oxygen increased in comparison with those in an earlier study in 2009–2010. Nine microalgal species, which consisted of four diatoms, two dinoflagellates, one cryptophycean, one raphidophycean and one euglenophycean, formed the blooms with water discolorations during spring and summer. The species that reached the highest bloom density were Plagioselmis prolonga (62.4 × 106 cells l−1) among crytophyceans, Heterocapsa triquetra (21.8 × 106 cells l−1) among dinoflagellates and Skeletonema marinoi (39 × 106 cells l−1) among diatoms. The abundance of dinoflagellates and phytoflagellates increased particularly in the upper estuary when compared to diatoms and their rapid growth and bloom formation revealed that they have a wide range of tolerance to changing environmental conditions and a strong ability to compete with other species in this study area.

Spatial links of phytoplankton abundance and community structure between shelf and slope waters off Oregon, USA

Abstract Coastal upwelling is known for inducing nearshore primary production, which can be advected to the offshore environment through offshore Ekman transport. However, this nearshore−offshore phytoplankton link has been less characterized at the community level. This study focuses on two shelf and slope sites off Oregon during years of 2013−2017 to examine the shelf−slope covariations in diatom and dinoflagellate abundance and community structure at seasonal and annual timescales. In general, the temporal changes of diatom and dinoflagellate abundance were coherent between shelf and slope. However, some differences were also noticeable. For example, diatom and dinoflagellate bloom magnitudes were higher in 2017 and 2014 on the shelf, but were higher in 2014−2016 at the slope. Diatom abundance had a stronger shelf−slope correlation than dinoflagellate correlation particularly in spring. The community structure was significantly correlated between shelf and slope during the annual upwelling period and in spring season. Ekman transport and nutrients played a significant role in shaping the diatom abundance and community structure temporal patterns at the slope. This shelf−slope correlation study infers that the benefits of nearshore upwelling blooms to the offshore food chains are season dependent and under high interannual variability.

Plankton community responses to pulsed upwelling events in the southern Taiwan Strait

AbstractWe used field observations (mapping and time-series observations) and satellite data to investigate the changes of environmental factors and plankton community structure during four pulsed upwelling events in the southern Taiwan Strait (STWS) during August 2004 and July 2005. Based on the surface temperature, salinity, and concentrations of nitrate, oxygen, and chlorophyll a (Chl a), we identified three stages of upwelling: recent, mature, and aged upwelled water. Diatoms and Synechococcus dominated during the first two and third stages of the upwelling, respectively. In recently upwelled water, phytoplankton grew rapidly, and nutrient concentrations were relatively high. Diatoms accounted for &amp;gt;69% of the total Chl a in recently upwelled and mature water. As the upwelled water aged, the phytoplankton community shifted to coexistence of diatoms and Synechococcus. The microzooplankton community was dominated by aloricate ciliates and tintinnids during upwelling, but the abundance of heterotrophic dinoflagellates increased as the upwelled water matured. Microzooplankton grazing reached a maximum during the mature stage and approximately balanced phytoplankton growth in aged, upwelled water. Overall, our study revealed rapid changes in the plankton community during the different stages of upwelling that reflected the complex and dynamic nature of upwelling systems.

Benthic dinoflagellates: Testing the reliability of the artificial substrate method in the Macaronesian region

The suitability of the ‘artificial substrate’ method, i.e. standardized surfaces of fiberglass screens, for the quantification of four benthic harmful algal bloom (BHAB) dinoflagellates (Gambierdiscus, Ostreopsis, Prorocentrum and Coolia) was tested relative to estimates from natural macroalgal substrates. Sampling took place in a variety of intertidal and subtidal coastal habitats under different water motion conditions, at depths from 1 to 7 m, in two archipelagos of the Macaronesia region: The Canary Islands and Cape Verde. An immersion time of 24 h was sufficient to adequately estimate dinoflagellate abundances. Seven replicates were established as the ideal replication level, considering both reproducibility and sampling effort. In most cases, cell abundances of the four dinoflagellate genera showed lower variability on artificial substrates than on macroalgae, leading to more reliable estimates of abundances. The ratio of mean cell abundances on artificial substrates to mean cell abundances on macroalgae highly varied among sampling sites for each genus. This was especially true for Ostreopsis and Coolia. Thus, given the potentially harmful nature of benthic dinoflagellates, the transformation of abundances expressed as cells g−1 of macroalgae to abundances expressed as cells cm-2 is risky, and it should not be attempted in monitoring and management programs of harmful microalgae. In summary, results of this study support the use of artificial substrates in monitoring programs of BHAB dinoflagellates, while the risks of using macroalgae are stressed.

Photosynthesis by symbiotic sponges enhances their ability to erode calcium carbonate

Photosynthesis is an important driver of calcium carbonate deposition on tropical coral reefs largely due to the symbiosis of numerous invertebrates with photosynthetic dinoflagellates in the family Symbiodiniaceae. In bioeroding sponges, however, similar symbioses appear to support the decalcification of carbonate substrates. Compared to its role in calcification, the relative importance of photosynthesis to decalcification processes is less known. Here, the daytime and night-time chemical bioerosion rates of the common Indo-Pacific sponge Cliona orientalis were examined under varying levels of photosynthetic activity and/or varying abundances of intracellular dinoflagellates. Photosynthesis was manipulated either by preconditioning the sponges with the photosynthetic inhibitor diuron (DCMU), or by exposing them to short-term heat stress to achieve bleaching (loss of symbionts). DCMU reduced symbiont numbers and diminished their ability to evolve oxygen. Thermal stress caused a significantly greater loss of symbionts, but photosynthesis was less inhibited. In both cases, decreases in photosynthetic activity and symbiont densities led to proportionately lowered daytime chemical bioerosion rates. Moreover, increased rates of night-time bioerosion were linked to greater daytime rates of photosynthesis, rather than to the night-time respiration of the sponge holobiont. Our findings support the conclusion that photosynthetic products (photosynthates) and/or by-products (oxygen) stimulate sponge bioerosion. This work further reveals the importance of symbionts in the ecology of such sponges and in their ability to sustain high bioerosion activity in otherwise nutrient-poor ecosystems.

Inter-annual variability of oceanographic conditions and phytoplankton in Valparaíso Bay (~33°S), central Chile

The inter-annual variability of oceanographic conditions and phytoplankton abundance and biomass was studied using 10 years (1986-1996) of in situ observations at a fixed station in Valparaíso Bay (~33ºS). The time series analysis revealed that strong S-SW winds drive a quasi-permanent upwelling activity that maintain the nutrients availability in the water column to fuel the phytoplankton in the bay. The most important changes in bio-oceanographic conditions were observed during 1987 El Niño event, which was characterized by higher temperatures but lower values for salinity, nitrate, and phosphate concentrations, together with a decrease of phytoplankton biomass compared to 1988 La Niña event when colder, saltier, and nutrient-rich upwelled water were observed. High Aconcagua River discharges were observed during the El Niño conditions (1987-1988 and 1993), which led to a decrease in surface salinity and a high abundance of dinoflagellates. Two periods with differences in bio-oceanographic conditions were observed; 1988-1992 showed lower temperatures but higher nutrients (nitrate), phytoplankton biomass and abundance of diatoms than 1993-1996 period. Throughout the study period, positive trends in upwelling activity was registered accompanied by a fall in phytoplankton biomass and dinoflagellate abundance. This paper provides new evidences concerning the influence of El Niño Southern Oscillation (ENSO) in phytoplankton and oceanographic conditions in the coastal upwelling off central Chile.

First spatial distribution of potentially toxic benthic dinoflagellates in the Lesser Antilles (Guadeloupe and Martinique), Caribbean Sea

Abstract For the first time, distribution and abundances (cells per gram of fresh macrophyte weight) of potentially toxic benthic dinoflagellates were studied around Guadeloupe (20 sites) and Martinique (six sites) islands (Lesser Antilles, Caribbean Sea). Benthic dinoflagellates were identified at the genus level and cell counts were undertaken on different host species of macroalgae and seagrasses. Abundance values of potentially toxic benthic dinoflagellates were one order of magnitude higher in Guadeloupe than in Martinique. The highest abundances of benthic dinoflagellates were found in the northern part of Guadeloupe Island, while their distribution was more homogeneous in Martinique. Ostreopsis was the dominant genus in Guadeloupe and Martinique. Regarding biotic substrate preferences, Phaeophyceae hosted the highest total abundances of benthic dinoflagellates on both islands, while the lowest total abundances were observed on Ulvophyceae in Guadeloupe and Florideophyceae in Martinique. The genus Gambierdiscus, known as the causal agent of the ciguatera fish poisoning (CFP), developed on all macrophyte groups on both islands without showing any preferences towards biotic substrates. The presence of this potentially harmful dinoflagellate genus in both islands could explain the existence of local cases of CFP in Guadeloupe and Martinique islands.

Rearing of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) in BFT system with different photoperiods: Effects on the microbial community, water quality and zootechnical performance

In Biofloc Technology (BFT) Systems, there are changes in microbial communities during a shrimp culture cycle; usually, heterotrophic bacteria are replaced by a photoautotrophic or chemoautotrophic community, depending on the management employed. When the water is exposed to sunlight, it can abruptly change from a heterotrophic system (dominated by bacteria and protozoa) to a predominantly photoautotrophic system, with a dominance of microalgae. However, there is little information on the characterization and quantification of the microbial community in the culture of the Pacific white shrimp Litopenaeus vannamei in a BFT system with light restriction, especially the contribution of these microrganisms to the zootechnical performance of shrimp. The aim of this study was to evaluate the microbial community in a rearing environment with light restriction. The study was conducted in 12 tanks (800 L) with a storage density of 500 shrimp m−3 and an initial shrimp weight of 0.053 g. The experiment was designed with three treatments and four replicates distributed into the following groups: i) natural photoperiod - 12 h light/12 h dark (NP); ii) 24 h light (24hLI); and iii) 24 h dark (24hDA). Significant differences were found in water quality parameters (lower values of ammonia and nitrite in the 24hDA treatment), and higher values of CO2, light (Ix) and chlorophyll were observed for the NP and 24hLI treatments than for the 24hDA treatment (p < .05). Zootechnical performance registered higher values in final weight, final biomass, weekly growth rate and survival in the NP and 24hLI treatments than in the 24hDA treatment (p < .05). Proximal analysis of the biofloc showed higher concentrations of proteins and lipids in the NP and 24hLI treatments than in the 24hDA treatment (p < .05), and there was a greater abundance of bacteria (attached coccoid, free filamentous, and attached filamentous bacteria, Vibrio and Bacillus) in NP and 24hLI than in 24hDA (p < .05). There was a greater abundance of photoautotrophic flagellates, heterotrophic flagellates, ciliates, dinoflagellates, rotifers and nematodes in NP and 24hLI than in 24hDA (p < .05). The results show that light restriction favored nitrification. However, light exposition promoted an increased abundance of microrganisms, providing an additional food source and reflecting a lower rate of feed conversion, higher survival and better growth performance for L. vannamei.

Patterns and drivers of dimethylsulfide concentration in the northeast subarctic Pacific across multiple spatial and temporal scales

Abstract. The northeast subarctic Pacific (NESAP) is a globally important source of the climate-active gas dimethylsulfide (DMS), yet the processes driving DMS variability across this region are poorly understood. Here we examine the spatial distribution of DMS at various spatial scales in contrasting oceanographic regimes of the NESAP. We present new high-spatial-resolution measurements of DMS across hydrographic frontal zones along the British Columbia continental shelf, together with key environmental variables and biological rate measurements. We combine these new data with existing observations to produce a revised summertime DMS climatology for the NESAP, yielding a broader context for our sub-mesoscale process studies. Our results demonstrate sharp DMS concentration gradients across hydrographic frontal zones and suggest the presence of two distinct DMS cycling regimes in the NESAP, corresponding to microphytoplankton-dominated waters along the continental shelf and nanoplankton-dominated waters in the cross-shelf transitional zone. DMS concentrations across the continental shelf transition (range &lt; 1–10 nM, mean 3.9 nM) exhibited positive correlations to salinity (r=0.80), sea surface height anomaly (SSHA; r=0.51), and the relative abundance of prymnesiophyte and dinoflagellates (r=0.89). In contrast, DMS concentrations in nearshore coastal transects (range &lt; 1–24 nM, mean 6.1 nM) showed a negative correlation with salinity (r=-0.69; r=-0.78) and SSHA (r=-0.81; r=-0.75) and a positive correlation to relative diatom abundance (r=0.88; r=0.86). These results highlight the importance of bloom-driven DMS production in continental shelf waters of this region and the role of prymnesiophytes and dinoflagellates in DMS cycling further offshore. In all areas, the rate of DMS consumption appeared to be an important control on observed concentration gradients, with higher DMS consumption rate constants associated with lower DMS concentrations. We compiled a data set of all available summertime DMS observations for the NESAP (including previously unpublished results) to examine the performance of several existing algorithms for predicting regional DMS concentrations. None of these existing algorithms was able to accurately reproduce observed DMS distributions across the NESAP, although performance was improved by the use of regionally tuned coefficients. Based on our compiled observations, we derived an average summertime distribution map for DMS concentrations and sea–air fluxes across the NESAP, estimating a mean regional flux of 0.30 Tg of DMS-derived sulfur to the atmosphere during the summer season.

Spatio-Temporal Pattern of Dinoflagellates Along the Tropical Eastern Pacific Coast (Ecuador)

Among marine phytoplankton, dinoflagellates are a key component in marine ecosystems as primary producers. Some species synthesize toxins, associated with human seafood poisoning, and mortality in marine organisms. Thus, there is a large necessity to understand the role of environmental variables in dinoflagellates spatial-temporal patterns in response to future climate scenarios. In that sense, a monthly four-year (2013-2017) monitoring was taken to evaluate dinoflagellates abundances and physical-chemical parameters in the water column at different depths. Sampling sites were established at 10 miles in four locations within the Ecuadorian coast. A total of 102 taxa were identified, corresponding to 8 orders, 22 families, and 31 genera. Eight potentially harmful genera were registered but no massive blooms were detected. The most frequent dinoflagellates were Gymnodinium sp. and Gyrodinium sp. Environmental variables showed different mixing layer thickness and a conspicuous and deepening thermocline/oxycline/halocline and nutricline depending on annual and seasonal oceanographic fluctuations. This study confirms that seasonal and spatial distribution of the environmental variables are linked to the main current systems on the Eastern Tropical Pacific, thus the warm Panama current lead to a less dinoflagellates abundance in the north of Ecuador (Esmeraldas), while the Equatorial Upwelling and the cold nutrient-rich Humboldt Current influence dinoflagellates abundance at the central (Manta, La Libertad) and South of Ecuador (Puerto Bolivar), respectively. Inter-annual variability of dinoflagellates abundance is associated with ENSO and upwelling conditions. Climate change scenarios predict an increase in water surface temperature and extreme events frequency in tropical areas, so it is crucial to involve policy-makers and stakeholders in the implementation of future laws involving long-term monitoring and sanitary programs, not covered at present.

Microdiversity and temporal dynamics of marine bacterial dimethylsulfoniopropionate genes

Dimethylsulfoniopropionate (DMSP) is an abundant organic sulfur metabolite produced by many phytoplankton species and degraded by bacteria via two distinct pathways with climate-relevant implications. We assessed the diversity and abundance of bacteria possessing these pathways in the context of phytoplankton community composition over a 3-week time period spanning September-October, 2014 in Monterey Bay, CA. The dmdA gene from the DMSP demethylation pathway dominated the DMSP gene pool and was harboured mostly by members of the alphaproteobacterial SAR11 clade and secondarily by the Roseobacter group, particularly during the second half of the study. Novel members of the DMSP-degrading community emerged from dmdA sequences recovered from metagenome assemblies and single-cell sequencing, including largely uncharacterized gammaproteobacteria and alphaproteobacteria taxa. In the DMSP cleavage pathway, the SAR11 gene dddK was the most abundant early in the study, but was supplanted by dddP over time. SAR11 members, especially those harbouring genes for both DMSP degradation pathways, had a strong positive relationship with the abundance of dinoflagellates, and DMSP-degrading gammaproteobacteria co-occurred with haptophytes. This in situ study of the drivers of DMSP fate in a coastal ecosystem demonstrates for the first time correlations between specific groups of bacterial DMSP degraders and phytoplankton taxa.

Oceanography of Harmful Algal Blooms on the Ecuadorian Coast (1997–2017): Integrating Remote Sensing and Biological Data

Ocean climate drivers and phytoplankton life strategies interact in a complex dynamic to produce harmful algal blooms (HABs). This study aims to integrate historical biological data collected during “red tide” events along the Ecuadorian coast between 1997 and 2017 in relation to five ocean variables derived from satellite remote sensing data to explain the seasonal drivers of coastal processes associated with HABs dynamics. Seasonality of the occurrence of HABs was assessed in relation to oceanographic variables by applying multiple correspondence analysis (MCA) to the Ecuadorian central coast (Zone 1) and at the outer and inner Gulf of Guayaquil (Zone 2). Sixty-seven HABs events were registered between 1997 and 2017. From a total of 40 species of phytoplankton identified, 28 were identified as non-toxic and the remaining 12 are well known to produce toxins. Dinoflagellates were the taxonomic group most highly associated with potential HABs events along the entire Ecuadorian coast. HABs appear to be constrained by the Humboldt coastal upwelling, high precipitation, and associated coastal runoff, with higher biomass abundance in the Gulf of Guayaquil than in the central coast. Results from the MCA reveal that in the central Ecuadorian coast (oligotrophic system), toxic HABs occurred with low abundance of dinoflagellates, while in the Gulf of Guayaquil (eutrophic system), toxic HABs corresponded to a high abundance of dinoflagellates. In both cases, high values were found for sea surface temperature, precipitation, and irradiance—characteristic of wet seasons or El Nino years. Non-toxic HABs occurred with a high abundance of dinoflagellates, ciliates, and centric diatoms, corresponding to colder waters and low levels of precipitation and irradiance. These findings confirm that dinoflagellates display several strategies that enhance their productive capacity when ocean conditions are warmer, allowing them to produce toxins at high or at low concentrations. Considering that the Gulf of Guayaquil is essential to tourism, the shrimp industry, fisheries, and international shipping, these findings strongly suggest the need to establish an ecosystem health research program to monitor HABs and the development of a preventive policy for tourism and public health in Ecuador.