Siphonophores from surface waters of the Colombian Pacific Ocean (original) (raw)
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Aquatic Ecology, 2009
Environmental factors determining the spatial pattern of the whole siphonophore community, as well as the hydrological occurrence ranges, small-scale vertical distribution, and spatial niche breadth and overlap of 23 siphonophore species collected off a riverine system in the southern Gulf of Mexico were analysed. A total of 149 zooplankton samples were collected in different strata of the water column (from 0 to 100 m) over a grid of 23 oceanographic stations during low (April) and high (October) rainy periods. Temperature and salinity measurements were taken with a CTD probe. Considering both seasons, salinity fluctuated between 30.7 and 37.0, and temperature between 18.2 and 29.0°C. Under these conditions, the hydrological occurrence ranges of species were analysed. Data on siphonophore biovolumes in the upper 30-m layer were subjected to a regression tree (RT) analysis taking the zooplankton biomass, the distance to the shore, the temperature, and the salinity as predictable variables. Results of the RT analysis showed that the distance from the shore, food availability, and temperature were among the most important factors affecting siphonophore spatial distribution. Food availability had a positive influence on the siphonophores distribution, whereas temperatures higher than 28.1°C seemed to depress most siphonophore populations. Diphyes dispar moderately dominated the community and represented 30% of the total biovolume. The calycophorans Abylopsis tetragona, A. eschscholtzi, Diphyes bojani, and Chelophyes appendiculata were the most generalist species as revealed by their niche breadth values, and Enneagonum hyalinum endured the widest salinity conditions (30.7-37.0) and was mainly distributed in coastal waters. The second most abundant species, the physonect Agalma okeni, exhibited a low mean niche overlap value with the calycophoran species. We hypothesise that differences in diet composition between physonects and calycophorans are the main cause of those low niche overlap values.
The ecology of plankton in biological oceanography: a tribute to Marta Estrada’s task
Scientia Marina
Plankton ecology has been the object of intense research and progress in the last few decades. This has been partly due to technological advances that have facilitated the multidisciplinary and high-resolution sampling of ecosystems and improved experimentation and analytical methodologies, and to sophisticated modelling. In addition, exceptional researchers have had the vision to integrate all these innovative tools to form a solid theoretical background in ecology. Here we provide an overview of the outstanding research work conducted by Professor Marta Estrada and her pioneering contribution to different areas of research in the last four decades. Her research in biological oceanography has mainly focussed on phytoplankton ecology, taxonomy and physiology, the functional structure of plankton communities, and physical and biological interactions in marine ecosystems. She has combined a variety of field and laboratory approaches and methodologies, from microscopy to satellite observations, including in-depth statistical data analysis and modelling. She has been a reference for scientists all over the world. Here, her contributions to plankton ecology are summarized by some of her students and closest collaborators, who had the privilege to share their science and everyday experiences with her.
Journal of Plankton Research, 2006
We analyze for the first time the spatial distribution of siphonophores in relation to water masses along a 3750-km oceanic transect between the Chilean coast and the Easter Island (278 S), a sector scarcely known of eastern South Pacific Ocean. Thirty-one siphonophore species were identified; Sulculeolaria turgida and Vogtia glabra were recorded for the first time in this sector. The most abundant species were Muggiaea atlantica (29.2%), Eudoxoides spiralis (24.5%) and Lensia subtilis (13.1%). Two different siphonophore assemblages east and west of 76 W, associated respectively with Subantarctic Water and Subtropical Water masses, can be used as water mass indicators. The former included the three most abundant species, whereas the latter showed greater species richness. This study provides basic knowledge on spatial distribution of siphonophores, which is important to develop future research focused on understanding the ecological role and biological processes driven by planktonic organisms in the southeastern Pacific Ocean.
Hydrobiologia, 2007
Siphonophores are exclusively marine cnidaria and their predatory role in plankton foodwebs is well recognised. In this study, we analyse the structure and the spatial extent of siphonophore assemblages in relation to changes in freshwater outflows and food availability in the southern Gulf of Mexico during a high (October) and a low (April) outflow periods. A total of 149 samples were collected using a 505 lm multiple closing net at 1-6 levels (0-100 m) of the water column, depending on the bathymetry. Data on siphonophore species biovolumes (ml 100 m -3 ) were treated by means of the Bray-Curtis Dissimilarity Index, and two distinctive assemblages were identified: the 'inner' and the 'outer' assemblages, located over the inner and outer shelves. Temperature, salinity, zooplankton biomass, and siphonophore species were included in a Principal Component Analysis (PCA) to identify the factors associated with each assemblage. Geographical distribution of the assemblages practically remained the same during both seasons and its cross-shelf variability was stronger than the verti-
Marine Biodiversity, 2017
This study identifies the abundance and spatial distribution of siphonophores collected during spring of 2011 between the Reloncaví Fjord and the Boca del Guafo Passage, in the Chiloé Inland Sea (CIS), Chile. Nine species of siphonophore were identified (three Physonectae and six Calycophorae), of which Agalma elegans, Cordagalma ordinatum and Lensia meteori were recorded for the first time in the waters of the CIS. The dominant species were Muggiaea atlantica (88.0%) and Lensia conoidea (9.5%). The highest occurrence frequency was recorded for M. atlantica (81.2%) and L. conoidea (62.5%). Eudoxids were collected only for M. atlantica (52.1%), L. conoidea (43.7%) and Dimophyes arctica (4.2%). The highest siphonophore densities were found in the northern microbasin (Reloncaví Fjord, Reloncaví and Ancud gulfs), an area characterised by a predominance of estuarine waters (greater vertical stratification, lower temperatures and salinity, and a higher concentration of dissolved oxygen). The vertical distribution patterns showed that M. atlantica is found throughout the water column in the northern microbasin, though with preference for the depths of 0-50 m. In the southern microbasin it was distributed mainly in deeper waters (>50 m). L. conoidea tends to avoid the surface estuarine layer (0-25 m) and is mainly distributed through deeper layers (>25 m). The association with environmental variables shows that temperature and dissolved oxygen have a significantly influence over dominant species. Siphonophorae community showed unimodal responses to the environmental gradients and high interspecific variability compared with previous campaigns in the same geographical area.
Scientia Marina, 2014
Siphonophores collected in Chilean Patagonian fjords, between the Gulf of Penas and the Trinidad Channel in 2008 were analysed. A total of 12 species were recorded, of which Muggiaea bargmannae, Lensia subtilis, Praya dubia and Sphaeronectes fragilis were identified for the first time in this sector of the Patagonian fjords. M. bargmannae represents a new record for the southeastern Pacific. The most abundant species were Muggiaea atlantica (78.6%), Lensia conoidea (8.7%) and Dimophyes arctica (8.5%). M. atlantica, the dominant species, showed high densities in both oceanic and interior waters. L. conoidea and D. arctica, on the other hand, were principally collected in interior waters. M. atlantica was collected in less saline (<30), more oxygenated (6-7 mL L -1 ) shallow strata (0-50 m), while L. conoidea and D. arctica were collected below 50 m depth in more saline (30-33) and less oxygenated (4-6 mL L -1 ) waters. The eudoxids of these species followed the same horizontal and vertical distribution patterns as their polygastric stages. These results confirm the success of M. atlantica in the colonization of all the southern fjords and document an increase with respect to the results obtained for the same geographical area in the spring of 1996. They also allowed us to infer that salinity and dissolved oxygen vertical gradients play an important role in determining the depth distribution patterns of these species.
The special location (40-42°S in the Southwestern Atlantic Ocean) and the hydrodynamic regime (limited water exchange with open ocean) in San Matías Gulf (Argentina) seem to produce a particular fauna of planktonic cnidarians whose their abundances are mainly shaped by the Gulf circulation. Four oceanographic cruises, covering 93 stations in three different seasons during 2007 and 2008 were carried out to quantify species richness and abundance, as well as to analyse the distribution of these cnidarians. We identified 20 species of hydromedusae and one siphonophore, increasing the total number of hydromedusae for the area to 23. This value is similar to the one found in the abutting Argentine continental shelf (20), but with a different assemblage composition. Hydromedusae abundances found were low, except for a bloom of the Leptomedusa Obelia spp. during the cold season. The only siphonophore found in the area, Pyrostephos vanhoeffeni, has previously been thought to be endemic to Antarctic and sub-Antarctic waters, this being the first record for temperate waters of the Southwest Atlantic Ocean.
Journal of Marine Systems, 2012
A strong interest in the southern Patagonian shelf has emerged in recent years, along with the increasing recognition of its high biological productivity. Knowledge of the pelagic food web structure that supports the richness of this system is still developing, but there are indications that mesozooplankton occupy a pivotal position, as consumers of smaller plankton and as vital prey for fish and squid. All plankton communities in the size 2 μm-20 mm, total and size-fractioned chlorophyll a (Chl a), nutrients and hydrology were surveyed simultaneously in October 2005 between 47°S-55°S. Picoplankton, nanoplankton and microplankton were taxonomically and functionally (autotrophs, heterotrophs) sorted within each size fraction. Plankton data and trophic relationships were examined through multivariate statistics. At that time fairly homogeneous thermal conditions prevailed over most of the shelf but weak saline horizontal gradients were evident. N/P ratios indicated no N or P limitation for phytoplankton. Surface concentrations of total Chl a were particularly high in the Grande Bay area at ca. 51°S near shore (28.6 mg m − 3 ) and at ca. 47°S on the shelfbreak (7.7 mg m − 3 ). At both locations the contribution of the Chl a > 5 μm fraction was remarkably high. The dinoflagellate Prorocentrum minimum (10 · 10 6 cells L − 1 ) and the diatom Thalassiosira cf. oceanica (1.3 · 10 6 cells L − 1 ) were respectively blooming at these sites. Otherwise b 10 μm plankton prevailed overall. Copepods largely dominated the >200 μm fraction. Three mesozooplankton assemblages typical of the inner, middle, and outer shelf were identified. The inner and middle shelf assemblages overlapped slightly but were spatially separated from the outer shelf community. Adults and late copepodids of Drepanopus forcipatus were typical of the inner shelf assemblage. Middle-shelf species included the copepod Ctenocalanus vanus, the amphipod Themisto gaudichaudii and the chaetognath Sagitta tasmanica, while an assortment of taxa characterized the outer sector. Latitudinal patterns in mesozooplankton community composition were less noticeable than cross-shelf patterns. No clear distribution of phytoplankton and protozooplankton assemblages was apparent when the whole b 200 μm plankton community structure was considered. In contrast, communities in the optimal size food for copepods (> 10-200 μm) were slightly different across shelf. Overall, spatial patterns of mesozooplankton and food availability matched weakly, suggesting a poor coupling between consumers and their prey communities at the time. Significant correlations were found particularly with large autotrophs and heterotrophs.
Hydrobiologia
Code Morphotype + shape Taxa Code Morphotype + shape Taxa Cdia8 Centric diatoms-cylinder Coscinodiscus Cdia11 Climacodium Guinardia Centric diatom unidentified Rhizosolenia Thalassiosira Leptocylindrus Centric diatoms unidentified Cdia20 Pen9 Pleurosigma Unidentified morf. Navicula Ditylum Pennate diatom unidentified Pen13 Pennate diatoms-elliptic prism + 2 cylinders Pennate diatom unidentified Pen14 Diploneis Pen15 Pennate diatoms-rectangular Thalassionemataceae DIA10 Diatoms-prism on elliptic base Chaetoceros ADi15 Thalassionema sp.1 ADi10 Odontella aurita Thalassionema sp.2 Odontella sp.1 Thalassiothrix Pennate diatom unidentified Pennate diatom unidentified Athecate dinoflagellate unidentified Athecate dinoflagellate unidentified DIN1 Athecate dinoflagellate unidentified DIN3 Athecate dinoflagellate unidentified Thecate dinoflagellate unidentified Gymnodiniales Prorocentrum sp.1 Thecate dinoflagellate unidentified Protoperidinium sp.1 Dinophysis sp.1 Prorocentrum sp.2 Protoperidinium sp.2 DIN4 Athecate dinoflagellate unidentified DIN5 Athecate dinoflagellate unidentified Gymnodiniales Gymnodiniales Balechina sp.1 Gonyaulax sp.1 Protoperidinium sp.3 Prorocentrum sp.3 Protoperidinium sp.4 DIN6 Dinoflagellate-double cone Athecate dinoflagellate unidentified TDi2 Ornithocercus sp.1 Gymnodiniales Ceratium fusus Oxytoxum sp.1 Podolampas sp.1 TDi7 Protoperidinium sp.5 TDi19 Ceratium sp.1 Ceratium furca Ceratium hexacanthum Supplementary data-Appendix A: Morphotypes of phytoplankton based on geometric cell shape and codes used in the networks. Thecate dinoflagellate-ellipsoid + 2 cones + cylinder Centric diatoms-elliptic prism + 4 cones Thecate dinoflagellates-half sphere Thecate dinoflagellates-3 cones Centric diatoms-prism on triangle-base girdle view Athecate dinoflagellaterectangular box Athecate and thecate dinoflagellates-sphere Dinoflagellates-prolate spheroid Dinoflagellate-cone + half sphere Athecate dinoflagellate-prism on elliptic base girdle view Athecate and thecate dinoflagellatesellipsoid Pennate diatoms-prism on