PeerJ Preprints: Biological Oceanographyhttps://peerj.com/preprints/index.atom?journal=peerj&subject=1448Biological Oceanography articles published in PeerJ PreprintsFirst confirmation of the shell-boring oyster parasite Polydora websteri (Polychaeta: Spionidae) in Washington State, USAhttps://peerj.com/preprints/276212019-11-212019-11-21Julieta MartinelliHeather LopesLorenz HauserIsadora Jimenez-HidalgoTeri L KingJacqueline Padilla-GaminoPaul RawsonLaura SpencerJason WilliamsChelsea Wood
Invasions by the spionid polychaete Polydora websteri have resulted in the collapse of oyster aquaculture industries in Australia, New Zealand, and Hawaii. These worms burrow into the shells of bivalves, creating unsightly mud blisters that are unappealing to consumers and, when nicked during shucking, release mud and detritus that can foul oyster meats. Recent sightings of mud blisters on the shells of Pacific oysters (Crassostrea gigas) in Puget Sound, Washington, suggest a new spionid polychaete invasion. To determine the identity of the polychaete causing these mud blisters, we obtained Pacific oysters from two locations in Puget Sound and examined them for blisters and burrows associated with spionid infection. We then extracted polychaetes and sequenced mitochondrial (cytochrome c oxidase I [COI]) and nuclear (18S rRNA) genes to obtain species-level identifications for a subset of these worms. Our data confirm that P. websteri is present in mud blisters of Puget Sound oysters, constituting the first confirmed record of this species in Washington State. The presence of non-native P. websteri could threaten the sustainability of oyster aquaculture in Washington, which currently produces more shellfish than any other US state.
Invasions by the spionid polychaete Polydora websteri have resulted in the collapse of oyster aquaculture industries in Australia, New Zealand, and Hawaii. These worms burrow into the shells of bivalves, creating unsightly mud blisters that are unappealing to consumers and, when nicked during shucking, release mud and detritus that can foul oyster meats. Recent sightings of mud blisters on the shells of Pacific oysters (Crassostrea gigas) in Puget Sound, Washington, suggest a new spionid polychaete invasion. To determine the identity of the polychaete causing these mud blisters, we obtained Pacific oysters from two locations in Puget Sound and examined them for blisters and burrows associated with spionid infection. We then extracted polychaetes and sequenced mitochondrial (cytochrome c oxidase I [COI]) and nuclear (18S rRNA) genes to obtain species-level identifications for a subset of these worms. Our data confirm that P. websteri is present in mud blisters of Puget Sound oysters, constituting the first confirmed record of this species in Washington State. The presence of non-native P. websteri could threaten the sustainability of oyster aquaculture in Washington, which currently produces more shellfish than any other US state.Chronic trace metals effects of mine tailings on estuarine assemblages revealed by environmental DNAhttps://peerj.com/preprints/279242019-08-282019-08-28Angelo F BernardinoFabiano S PaisLouisi S OliveiraFabricio A GabrielTiago O FerreiraHermano M QueirozAna Carolina A Mazzuco
Mine tailing disasters have occurred worldwide and contemporary release of tailings of large proportions raise concerns of the chronic impacts that trace metals associated with tailings may have on the aquatic biodiversity. Environmental metabarcoding (eDNA) offers an yet poorly explored opportunity for biological monitoring of impacted aquatic ecosystems from mine tailings and contaminated sediments. eDNA has been increasingly recognized to be an effective method to detect previously unrecognized small-sized Metazoan taxa, but their ecological responses to environmental pollution has not been assessed by metabarcoding. Here we evaluated chronic effects of trace metal contamination from sediment eDNA of the Rio Doce estuary, 1.7 years after the Samarco mine tailing disaster, which released over 40 million m3of iron tailings in the Rio Doce river basin. We identified 123 new sequence variants (eOTUs) of benthic taxa and an assemblage composition dominated by Nematoda, Crustacea and Platyhelminthes; typical of other estuarine ecosystems. We detected environmental filtering on the meiofaunal assemblages and multivariate analysis revealed strong influence of Fe contamination, supporting chronic impacts from mine tailing deposition in the estuary. This was in contrast to environmental filtering of meiofaunal assemblages of non-polluted estuaries. Here we suggest that the eDNA metabarcoding technique provides an opportunity to fill up biodiversity gaps in coastal marine ecology and may become a valid method for long term monitoring studies in mine tailing disasters and estuarine ecosystems with high trace metals content.
Mine tailing disasters have occurred worldwide and contemporary release of tailings of large proportions raise concerns of the chronic impacts that trace metals associated with tailings may have on the aquatic biodiversity. Environmental metabarcoding (eDNA) offers an yet poorly explored opportunity for biological monitoring of impacted aquatic ecosystems from mine tailings and contaminated sediments. eDNA has been increasingly recognized to be an effective method to detect previously unrecognized small-sized Metazoan taxa, but their ecological responses to environmental pollution has not been assessed by metabarcoding. Here we evaluated chronic effects of trace metal contamination from sediment eDNA of the Rio Doce estuary, 1.7 years after the Samarco mine tailing disaster, which released over 40 million m3of iron tailings in the Rio Doce river basin. We identified 123 new sequence variants (eOTUs) of benthic taxa and an assemblage composition dominated by Nematoda, Crustacea and Platyhelminthes; typical of other estuarine ecosystems. We detected environmental filtering on the meiofaunal assemblages and multivariate analysis revealed strong influence of Fe contamination, supporting chronic impacts from mine tailing deposition in the estuary. This was in contrast to environmental filtering of meiofaunal assemblages of non-polluted estuaries. Here we suggest that the eDNA metabarcoding technique provides an opportunity to fill up biodiversity gaps in coastal marine ecology and may become a valid method for long term monitoring studies in mine tailing disasters and estuarine ecosystems with high trace metals content.Polymorphisms and distribution of South American manatees (Trichechus spp.)https://peerj.com/preprints/277872019-06-062019-06-06Cibele Rodrigues BonvicinoMaria Carolina VianaEdivaldo HC de OliveiraRenata Emin-LimaJosé de Sousa e Silva JúniorMaura Elisabeth M SousaSalvatore Siciliano
Traditionally, the morphological attributes and the range of Trichechus species have been clearly established. However, we herein show that morphological traits, like belly and pectoral flipper coloration in South American manatees may be polymorphic. Karyotypic analysis of T. manatus allowed the precise identification of this species and confirmed the variability of the observed morphological findings. Molecular analysis based on cytochrome b DNA and the D-loop mitochondrial region showed shared haplotypes between T. inunguis and T. manatus, suggesting the presence of an ancestral polymorphism. These findings showed the need of improving the identification of these species before implementing conservation strategies. Finally, we present a complete report on the extant distribution of these species in South America.
Traditionally, the morphological attributes and the range of Trichechus species have been clearly established. However, we herein show that morphological traits, like belly and pectoral flipper coloration in South American manatees may be polymorphic. Karyotypic analysis of T. manatus allowed the precise identification of this species and confirmed the variability of the observed morphological findings. Molecular analysis based on cytochrome b DNA and the D-loop mitochondrial region showed shared haplotypes between T. inunguis and T. manatus, suggesting the presence of an ancestral polymorphism. These findings showed the need of improving the identification of these species before implementing conservation strategies. Finally, we present a complete report on the extant distribution of these species in South America.Environment regime influence on Chlorophyll-a abundance and distribution in North Indian Oceanhttps://peerj.com/preprints/276622019-05-062019-05-06Thushani Suleka Madhubha ElepathageDanling Tang
North Indian Ocean region around India and Sri Lanka is a complex and rich coastal ecosystem undergoing various seasonal and inter-annual changes and various pressures. Hence the objective of this study was to assess the scales of coupling between chlorophyll-a concentration (chl-a) and the influencing variables and explore the nature of the spatiotemporal variability of them. The seasonal and annual variations of chl-a along the Bay of Bengal (BoB), Arabian sea (AS) and ocean region around Sri Lanka in relation to the physical and chemical oceanographic variables were analyzed using satellite observations covering the period of 2002-2018. The effects of diffuse attenuation coefficient, photosynthetically available radiation (PAR), sea surface temperature (SST), Wind speed, Eastward wind component, Nitrate, Black carbon column mass density, Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity were considered on a monthly time scale. Wavelet analysis and the Boosted Regression Trees (BRT) were used as the main analysis and modeling methods. The peaks of chl-a, diffuse attenuation coefficient, and nitrate were observed in September. In wind speed and eastward wind it was July and in black carbon column mass density, and PAR in March. In Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity, Diffuse attenuation coefficient for downwelling irradiance, and SST mean maximums were found in June, February, November, September, April respectively. In BRT model the estimated cross validation (cv) deviance, standard error (se), training data correlation, cv correlation, and D2 were 0.003, 0.002, 0.932, 0.949, and 0.846 respectively. According to the results, diffuse attenuation coefficient (90%), eastward wind component (3.7%) and nitrate (3%) were the most positively correlated variables with Chl-a occurrence. SST evidenced an inverse relationship with Chl-a. According to the model built <42 Einsteinm-2day-1 PAR, <0.986 surface emissivity, <70 Wm-2 open water net downward long wave flux, 28.2 -28.5 0C SST , 2 ms-1 Wind speed, 5 ms-1 - 6 ms-1 eastward wind, 4.8 x10-8 -7x10-8 kgm-3 sea salt surface mass concentration, and 0.1-0.5micromoleL-1 nitrate are favourable for the optimum level of phytoplankton occurrence. Since BRT deals robustly with non-linear relationships of the environmental variables it can be used in further studies of ecological modeling.
North Indian Ocean region around India and Sri Lanka is a complex and rich coastal ecosystem undergoing various seasonal and inter-annual changes and various pressures. Hence the objective of this study was to assess the scales of coupling between chlorophyll-a concentration (chl-a) and the influencing variables and explore the nature of the spatiotemporal variability of them. The seasonal and annual variations of chl-a along the Bay of Bengal (BoB), Arabian sea (AS) and ocean region around Sri Lanka in relation to the physical and chemical oceanographic variables were analyzed using satellite observations covering the period of 2002-2018. The effects of diffuse attenuation coefficient, photosynthetically available radiation (PAR), sea surface temperature (SST), Wind speed, Eastward wind component, Nitrate, Black carbon column mass density, Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity were considered on a monthly time scale. Wavelet analysis and the Boosted Regression Trees (BRT) were used as the main analysis and modeling methods. The peaks of chl-a, diffuse attenuation coefficient, and nitrate were observed in September. In wind speed and eastward wind it was July and in black carbon column mass density, and PAR in March. In Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity, Diffuse attenuation coefficient for downwelling irradiance, and SST mean maximums were found in June, February, November, September, April respectively. In BRT model the estimated cross validation (cv) deviance, standard error (se), training data correlation, cv correlation, and D2 were 0.003, 0.002, 0.932, 0.949, and 0.846 respectively. According to the results, diffuse attenuation coefficient (90%), eastward wind component (3.7%) and nitrate (3%) were the most positively correlated variables with Chl-a occurrence. SST evidenced an inverse relationship with Chl-a. According to the model built <42 Einsteinm-2day-1 PAR, <0.986 surface emissivity, <70 Wm-2 open water net downward long wave flux, 28.2 -28.5 0C SST , 2 ms-1 Wind speed, 5 ms-1 - 6 ms-1 eastward wind, 4.8 x10-8 -7x10-8 kgm-3 sea salt surface mass concentration, and 0.1-0.5micromoleL-1 nitrate are favourable for the optimum level of phytoplankton occurrence. Since BRT deals robustly with non-linear relationships of the environmental variables it can be used in further studies of ecological modeling.Detection of pelagic habitats and abundance of skipjack tuna in relation to the environment in the Indian Ocean around Sri Lankahttps://peerj.com/preprints/276632019-05-062019-05-06Thushani Suleka Madhubha ElepathageDanling Tang
Using remote sensing data of sea surface temperature (SST), chlorophyll-a (Chl-a) together with catch data, the pelagic hotspots of Skipjack tuna (SKPJ) were identified. MODIS/Aqua satellite data and the fish catch data were obtained during 2002-2016 period. Empirical cumulative distribution frequency (ECDF) model of satellite-based oceanographic data in relation to skipjack fishing was used for the initial statistical analysis and the results showed that key pelagic habitat corresponded mainly with the 0.4 – 0.7 mg m-3 Chl-a concentration. Chl-a represents the phytoplankton that attracts the food items of SKPJ like zooplankton and nekton The favorable SST range for SKPJ is 26 - 27 0C which provides suitable thermocline and an optimum level of upwelling to circulate nutrients needed for the primary production. The high total catches and CPUEs were found within the months of September to December and the optimum levels of Chl-a, SST also were observed in similar months. Hence, the South-West monsoon season was identified as the best and peak season of SKPJ fisheries. SST and Chl-a are important indicators to detect the habitats of SKPJ and the maps prepared can be used in the future to cost-effectively and efficiently identify and demarcate the biological conservation regions or fisheries zones of SKPJ. According to GAM the 0.3 - 0.6 mg m-3 Chl-a, 28 - 28.5 0C SST in Western and 0.25 - 0.3 mg m-3 Chl-a and 28.5 - 28.80C SST in Eastern were found as highly correlated predictor variables value ranges with SKPJ abundance. The deviances explained in above areas in GAM were 90.8% and 61.4% respectively. The GAM was considered as a robustly dealing method with nonlinear relationships and it can be used to model the fish catch abundance with influencing variables significantly since it could predict the CPUE values greater than 90% similarly to nominal CPUEs in both subregions of the study area.
Using remote sensing data of sea surface temperature (SST), chlorophyll-a (Chl-a) together with catch data, the pelagic hotspots of Skipjack tuna (SKPJ) were identified. MODIS/Aqua satellite data and the fish catch data were obtained during 2002-2016 period. Empirical cumulative distribution frequency (ECDF) model of satellite-based oceanographic data in relation to skipjack fishing was used for the initial statistical analysis and the results showed that key pelagic habitat corresponded mainly with the 0.4 – 0.7 mg m-3 Chl-a concentration. Chl-a represents the phytoplankton that attracts the food items of SKPJ like zooplankton and nekton The favorable SST range for SKPJ is 26 - 27 0C which provides suitable thermocline and an optimum level of upwelling to circulate nutrients needed for the primary production. The high total catches and CPUEs were found within the months of September to December and the optimum levels of Chl-a, SST also were observed in similar months. Hence, the South-West monsoon season was identified as the best and peak season of SKPJ fisheries. SST and Chl-a are important indicators to detect the habitats of SKPJ and the maps prepared can be used in the future to cost-effectively and efficiently identify and demarcate the biological conservation regions or fisheries zones of SKPJ. According to GAM the 0.3 - 0.6 mg m-3 Chl-a, 28 - 28.5 0C SST in Western and 0.25 - 0.3 mg m-3 Chl-a and 28.5 - 28.80C SST in Eastern were found as highly correlated predictor variables value ranges with SKPJ abundance. The deviances explained in above areas in GAM were 90.8% and 61.4% respectively. The GAM was considered as a robustly dealing method with nonlinear relationships and it can be used to model the fish catch abundance with influencing variables significantly since it could predict the CPUE values greater than 90% similarly to nominal CPUEs in both subregions of the study area.An enigmatic decoupling between heat stress and coral bleaching on the Great Barrier Reefhttps://peerj.com/preprints/276862019-04-252019-04-25Thomas DeCarloHugo B Harrison
Ocean warming threatens the functioning of coral reef ecosystems by inducing mass coral bleaching and mortality events. The link between temperature and coral bleaching is now well-established based on observations that mass bleaching events usually occur when seawater temperatures are anomalously high. However, times of high heat stress but without coral bleaching are equally important because they can inform an understanding of factors that mitigate temperature-induced bleaching. Here, we investigate the absence of mass coral bleaching on the Great Barrier Reef (GBR) during austral summer 2004. Using four gridded sea surface temperature (SST) data products, validated with in situ temperature loggers, we demonstrate that the summer of 2004 was among the warmest summers of the satellite era (1982-2017) on the GBR. At least half of the GBR experienced temperatures that were high enough to initiate bleaching in other years, yet mass bleaching was not reported during 2004. The absence of bleaching is not fully explained by wind speed or cloud cover. Rather, 2004 is clearly differentiated from bleaching years by the slow speed of the East Australian Current (EAC) offshore of the GBR. An anomalously slow EAC during summer 2004 may have dampened the upwelling of nutrient-rich waters onto the GBR shelf, potentially mitigating bleaching due to the lower susceptibility of corals to heat stress in low-nutrient conditions. Although other factors such as irradiance or acclimatization may have played a role in the absence of mass bleaching, 2004 remains a key case study for demonstrating the dynamic nature of coral responses to marine heatwaves.
Ocean warming threatens the functioning of coral reef ecosystems by inducing mass coral bleaching and mortality events. The link between temperature and coral bleaching is now well-established based on observations that mass bleaching events usually occur when seawater temperatures are anomalously high. However, times of high heat stress but without coral bleaching are equally important because they can inform an understanding of factors that mitigate temperature-induced bleaching. Here, we investigate the absence of mass coral bleaching on the Great Barrier Reef (GBR) during austral summer 2004. Using four gridded sea surface temperature (SST) data products, validated with in situ temperature loggers, we demonstrate that the summer of 2004 was among the warmest summers of the satellite era (1982-2017) on the GBR. At least half of the GBR experienced temperatures that were high enough to initiate bleaching in other years, yet mass bleaching was not reported during 2004. The absence of bleaching is not fully explained by wind speed or cloud cover. Rather, 2004 is clearly differentiated from bleaching years by the slow speed of the East Australian Current (EAC) offshore of the GBR. An anomalously slow EAC during summer 2004 may have dampened the upwelling of nutrient-rich waters onto the GBR shelf, potentially mitigating bleaching due to the lower susceptibility of corals to heat stress in low-nutrient conditions. Although other factors such as irradiance or acclimatization may have played a role in the absence of mass bleaching, 2004 remains a key case study for demonstrating the dynamic nature of coral responses to marine heatwaves.Century-scale changes in phytoplankton phenology in the Gulf of Mainehttps://peerj.com/preprints/274252018-12-122018-12-12Nicholas R RecordWilliam M BalchKaren Stamieszkin
The phenology of major seasonal events is an important indicator of climate. We analyzed multiple datasets of in situ chlorophyll measurements from the Gulf of Maine dating back to the early 20th century in order to detect climate-scale changes in phenology. The seasonal cycle was consistently characterized by a two-bloom pattern, with spring and autumn blooms. The timing of both spring and autumn blooms has shifted later in the year at rates ranging from ~1 to 9 days per decade since 1960, depending on the phenology metric, and trends only emerged at time scales of >40 years. Bloom phenology had only weak correlations with major climate indices. There were stronger associations between bloom timing and physical and chemical variables. Autumn bloom initiation correlated strongly with surface temperature and salinity, and spring bloom with nutrients. A later spring bloom also correlated with an increased cohort of Calanus finmarchicus, suggesting broader ecosystem implications of phytoplankton phenology.
The phenology of major seasonal events is an important indicator of climate. We analyzed multiple datasets of in situ chlorophyll measurements from the Gulf of Maine dating back to the early 20th century in order to detect climate-scale changes in phenology. The seasonal cycle was consistently characterized by a two-bloom pattern, with spring and autumn blooms. The timing of both spring and autumn blooms has shifted later in the year at rates ranging from ~1 to 9 days per decade since 1960, depending on the phenology metric, and trends only emerged at time scales of >40 years. Bloom phenology had only weak correlations with major climate indices. There were stronger associations between bloom timing and physical and chemical variables. Autumn bloom initiation correlated strongly with surface temperature and salinity, and spring bloom with nutrients. A later spring bloom also correlated with an increased cohort of Calanus finmarchicus, suggesting broader ecosystem implications of phytoplankton phenology.Differential expression of the glucose transporter gene glcH in response to glucose and light in marine picocyanobacteriahttps://peerj.com/preprints/274232018-12-102018-12-10José Ángel Moreno-CabezueloAntonio López-LozanoJesús DíezJosé Manuel García-Fernández
Background
Our team discovered that Prochlorococcus can take up glucose, in a process that changes the transcriptional pattern of several genes involved in glucose metabolization. We have also shown that glcH encodes a very high affinity glucose transporter, and that glucose is taken up by natural Prochlorococcus populations. We demonstrated that the kinetic parameters of glucose uptake show significant diversity in different Prochlorococcus and Synechococcus strains. Here we tested whether the transcriptional response of glcH to several glucose concentrations and light conditions was also different depending on the studied strain.
Methods
Cultures were grown in the light, supplemented with five different glucose concentrations or subjected to darkness, and cells harvested after 24 h of treatment. qRT-PCR was used to determine glcH expression in four Prochlorococcus and two Synechococcus strains.
Results
In all studied strains glcH was expressed in the absence of glucose, and it increased upon glucose addition to cultures. The changes differed depending on the strain, both in the magnitude and in the way cells responded to the tested glucose concentrations. Unlike the other strains, Synechococcus BL107 showed the maximum glucose uptake at 5 nM glucose. Darkness induced a strong decrease in glcH expression, especially remarkable in Prochlorococcus MIT9313.
Discussion
Our results suggest that marine picocyanobacteria are actively monitoring the availability of glucose, to upregulate glcH expression in order to exploit the presence of sugars in the environment. The diverse responses observed in different strains suggest that the transcriptional regulation of glucose uptake has been adjusted by evolutive selection. Darkness promotes a strong decrease in glcH expression in all studied strains, which fits with previous results on glucose uptake in Prochlorococcus. Overall, this work reinforces the importance of mixotrophy for marine picocyanobacteria.
BackgroundOur team discovered that Prochlorococcus can take up glucose, in a process that changes the transcriptional pattern of several genes involved in glucose metabolization. We have also shown that glcH encodes a very high affinity glucose transporter, and that glucose is taken up by natural Prochlorococcus populations. We demonstrated that the kinetic parameters of glucose uptake show significant diversity in different Prochlorococcus and Synechococcus strains. Here we tested whether the transcriptional response of glcH to several glucose concentrations and light conditions was also different depending on the studied strain.MethodsCultures were grown in the light, supplemented with five different glucose concentrations or subjected to darkness, and cells harvested after 24 h of treatment. qRT-PCR was used to determine glcH expression in four Prochlorococcus and two Synechococcus strains.ResultsIn all studied strains glcH was expressed in the absence of glucose, and it increased upon glucose addition to cultures. The changes differed depending on the strain, both in the magnitude and in the way cells responded to the tested glucose concentrations. Unlike the other strains, Synechococcus BL107 showed the maximum glucose uptake at 5 nM glucose. Darkness induced a strong decrease in glcH expression, especially remarkable in Prochlorococcus MIT9313.DiscussionOur results suggest that marine picocyanobacteria are actively monitoring the availability of glucose, to upregulate glcH expression in order to exploit the presence of sugars in the environment. The diverse responses observed in different strains suggest that the transcriptional regulation of glucose uptake has been adjusted by evolutive selection. Darkness promotes a strong decrease in glcH expression in all studied strains, which fits with previous results on glucose uptake in Prochlorococcus. Overall, this work reinforces the importance of mixotrophy for marine picocyanobacteria.The spatial variability of qualitative and quantitative structure of planktonic protist communities in the North Atlantic Current (the Nordic Seas)https://peerj.com/preprints/273372018-11-112018-11-11Anna M KubiszynJózef WiktorMałgorzata MerchelJózef Wiktor
We investigated the spatial variability of qualitative and quantitative planktonic protist community structure in the Nordic Seas in relation to the environmental factors. Our study was conducted in the summers of 2015 and 2016 during cruises of the Institute of Oceanology PAS to the Norwegian and Greenland Seas. The samples were collected using Niskin bottles from the constant depths covering the euphotic zone (5 m, 15 m, 25 m, 35 m, 50 m) and then integrated, using trapezoidal formula, to represent protist community structure under the square meter of the water column, and fixed with an acidic Lugol's solution and, after 24hs, with a glutaraldehyde (both to a final concentration of 2%). Samples were analysed according to the Utermöhl method. The lack of a clear variability in the longitudinal-latitudinal qualitative protist community distribution was accompanied by the absence of distinct differences in the hydrography of the area. The highest total protist abundance was observed in the areas between 70-72 ºN and 74-76 ºN. The first more southerly-located peak was related to the presence of Bacillariophyceae, which numbers decreased northward, whereas the second peak was likely an effect of the increase in protist cells concentration in the frontal zones. In the longitudinal aspect, the eastward increase in Bacillariophyceae abundance was associated with the decrease in the other protist taxa. The observed communities were represented by four distinct types, distributed without any evident pattern: composed solely of Bacillariophyceae (1), Flagellates (2), Prymnesiophyceae (3) and a mixture of flagellates (Dinophyceae, Cryptophyceae) and Bacillariophyceae (4). Although our investigation seems to exclude the longitudinal-latitudinal protist zonation in the area, a further protist study under different hydrographic conditions is needed to confirm it.
We investigated the spatial variability of qualitative and quantitative planktonic protist community structure in the Nordic Seas in relation to the environmental factors. Our study was conducted in the summers of 2015 and 2016 during cruises of the Institute of Oceanology PAS to the Norwegian and Greenland Seas. The samples were collected using Niskin bottles from the constant depths covering the euphotic zone (5 m, 15 m, 25 m, 35 m, 50 m) and then integrated, using trapezoidal formula, to represent protist community structure under the square meter of the water column, and fixed with an acidic Lugol's solution and, after 24hs, with a glutaraldehyde (both to a final concentration of 2%). Samples were analysed according to the Utermöhl method. The lack of a clear variability in the longitudinal-latitudinal qualitative protist community distribution was accompanied by the absence of distinct differences in the hydrography of the area. The highest total protist abundance was observed in the areas between 70-72 ºN and 74-76 ºN. The first more southerly-located peak was related to the presence of Bacillariophyceae, which numbers decreased northward, whereas the second peak was likely an effect of the increase in protist cells concentration in the frontal zones. In the longitudinal aspect, the eastward increase in Bacillariophyceae abundance was associated with the decrease in the other protist taxa. The observed communities were represented by four distinct types, distributed without any evident pattern: composed solely of Bacillariophyceae (1), Flagellates (2), Prymnesiophyceae (3) and a mixture of flagellates (Dinophyceae, Cryptophyceae) and Bacillariophyceae (4). Although our investigation seems to exclude the longitudinal-latitudinal protist zonation in the area, a further protist study under different hydrographic conditions is needed to confirm it.Seasonal changes in the abundance and biomass of copepod in the south-eastern Baltic Sea in 2010 and 2011https://peerj.com/preprints/266892018-09-052018-09-05Lidia Dzierzbicka-GlowackaAnna LemieszekEvelina GrinieneMarcin Kalarus
Background. Copepods are the major secondary producers in the World Ocean. They represent an important link between phytoplankton, microzooplankton and higher trophic levels such as fish. They are an important source of food for many fish species, but also a significant producer of detritus. In terms of their role in the marine food web, it is important to know how the environmental variability affects the population of Copepoda.
Methods. The study of the zooplankton community in the south-eastern Baltic Sea conducted during a 24-month survey (January 2010 to November 2011) resulted in 24 invertebrate species identified (10copepods, 7cladocerans, 4rotifers, 1ctenophore, Fritillaria borealis and Hyperia galba). Data were collected at two stations located on the open-sea deep-water station – the Gdańsk Deep (54o50’φN, 19o19’λE) and in the western, inner part of the Gulf of Gdańsk (54o32’ φN, 18o48.2 ’λE). Vertical hauls were carried out using two nets: a Copenhagen net with an inlet diameter of 50 cm and a mesh diameter of 100 µm (in 2010) and WP-2 net from KC Denmark with an inlet diameter of 57 cm and a mesh diameter of 100 µm (in 2011).
Results. The paper describes seasonal changes in the abundance and biomass of Copepoda, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They usually represented the main component of zooplankton. The average number of Copepoda at station P1 during the study period of 2010 was 3913 ind.m-3 (SD 2572) and their number ranged from 1184 ind. m-3 (in winter) to 6293 ind.m-3 (in spring). One year later, the average count of copepods was higher, i.e. 11 723 ind. m-3 (SD 6980) and ranged from 2351 ind. m-3 (in winter) to 18 307 ind.m-3 (in summer). Their average count at station P2 in 2010 was 29 141 ind. m-3 ranging from 3330 ind.m-3 (in March) to 67 789 ind. m-3 (in May). The average count of copepods in 2011 was much lower – 17 883 ind./m3 and ranged from 1360 ind./m3 (in April) to 39 559 ind./m3 (in May).
Discussion. The environment of pelagic animals changes with the distance from the shore and with the sea depth. Although the qualitative structure of zooplankton is almost identical with that of the coastal waters, the quantitative structure changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdańsk Deep and the inner part of the Gulf of Gdańsk. Copepoda dominated in the composition of zooplankton for almost the entire duration of the research.. Quantitative taxonomic composition of Copepoda at station P1 (the Gdańsk Deep) was different compared to station P2 (the western, inner part of the Gulf of Gdańsk) due to a high percentage of a crustacean preferring waters with lower temperature and higher salinity – Pseudocalanus sp.
Background. Copepods are the major secondary producers in the World Ocean. They represent an important link between phytoplankton, microzooplankton and higher trophic levels such as fish. They are an important source of food for many fish species, but also a significant producer of detritus. In terms of their role in the marine food web, it is important to know how the environmental variability affects the population of Copepoda.Methods. The study of the zooplankton community in the south-eastern Baltic Sea conducted during a 24-month survey (January 2010 to November 2011) resulted in 24 invertebrate species identified (10copepods, 7cladocerans, 4rotifers, 1ctenophore, Fritillaria borealis and Hyperia galba). Data were collected at two stations located on the open-sea deep-water station – the Gdańsk Deep (54o50’φN, 19o19’λE) and in the western, inner part of the Gulf of Gdańsk (54o32’ φN, 18o48.2 ’λE). Vertical hauls were carried out using two nets: a Copenhagen net with an inlet diameter of 50 cm and a mesh diameter of 100 µm (in 2010) and WP-2 net from KC Denmark with an inlet diameter of 57 cm and a mesh diameter of 100 µm (in 2011).Results. The paper describes seasonal changes in the abundance and biomass of Copepoda, taking into account the main Baltic calanoid copepod taxa (Acartia spp., Temora longicornis and Pseudocalanus sp.). They usually represented the main component of zooplankton. The average number of Copepoda at station P1 during the study period of 2010 was 3913 ind.m-3 (SD 2572) and their number ranged from 1184 ind. m-3 (in winter) to 6293 ind.m-3 (in spring). One year later, the average count of copepods was higher, i.e. 11 723 ind. m-3 (SD 6980) and ranged from 2351 ind. m-3 (in winter) to 18 307 ind.m-3 (in summer). Their average count at station P2 in 2010 was 29 141 ind. m-3 ranging from 3330 ind.m-3 (in March) to 67 789 ind. m-3 (in May). The average count of copepods in 2011 was much lower – 17 883 ind./m3 and ranged from 1360 ind./m3 (in April) to 39 559 ind./m3 (in May).Discussion. The environment of pelagic animals changes with the distance from the shore and with the sea depth. Although the qualitative structure of zooplankton is almost identical with that of the coastal waters, the quantitative structure changes quite significantly. The maximum values of zooplankton abundance and biomass were observed in the summer season, both in the Gdańsk Deep and the inner part of the Gulf of Gdańsk. Copepoda dominated in the composition of zooplankton for almost the entire duration of the research.. Quantitative taxonomic composition of Copepoda at station P1 (the Gdańsk Deep) was different compared to station P2 (the western, inner part of the Gulf of Gdańsk) due to a high percentage of a crustacean preferring waters with lower temperature and higher salinity – Pseudocalanus sp.