Search results for "plankton"

Short-term variability of mesozooplankton in a Mediterranean Coastal sound (Stagnone di Marsala, Western Sicily)

2001

Short-term variations in mesozooplankton were studied during four 24-h periods at one station in a Mediterranean coastal sound (Stagnone di Marsala, western Sicily) in May, July and October 1996 and March 1997. Zooplankton samples were collected every three or six hours with a plankton net (mesh size 125 µm) towed horizontally at the surface. Hydrometric data (height of tide, speed and direction of current) were also recorded to assess the influence of the hydrodynamic conditions on fluctuations in zooplankton abundance and changes in population structure. The zooplankton assemblages were markedly dominated by copepods and their naupliar stages, which consistently accounted for more than 95…

Unveiling the Relationship Between Sea Surface Hydrographic Patterns and Tuna Larval Distribution in the Central Mediterranean Sea

2021

Thunnus thynnus (Atlantic bluefin tuna, ABT) and other tuna species reproduce in the Mediterranean Sea during the summer period. Despite the Central Mediterranean Sea, the Strait of Sicily in particular, being a key spawning site for many tuna species, little is known on the effects of oceanographic variability on their larval distribution in this area. The abundance and presence-absence of larval specimens for three tuna species (ABT, bullet tuna and albacore) were modeled in order to examine their relationships with environmental factors, by analysing historical in situ information collected during seven annual surveys (2010–2016). The results revealed that most tuna larvae for the three …

How do phytoplankton biomass and functional groups react to environmental constraints? A comparison in two different Mediterranean ponds

2009

Grouping organisms into functional grouping represents a way to better understand how the environmental constrains act on these organisms through the analysis of peculiar features, usually morphological, shared by the set of species. Since groups (Coda) react to environmental constrains with an analogous response, this approach was adopted to compare the structure and the biomass of phytoplankton assemblages in two different Mediterranean ponds, one temporary and the other permanent. A phytoplankton survey, carried out monthly in the brackish and shallow Biviere di Gela in 2005-2007, revealed a deep transformation in the structure of its phytoplankton assemblage as compared with similar dat…

Impact on the water column biogeochemistry of a Mediterranean mussel and fish farm

2002

We investigated and compared the impact of organic loads due to the biodeposition of mussel and fish farms on the water column of a coastal area of the Tyrrhenian Sea (Western Mediterranean). Physico-chemical data (including oxygen, nutrients, DOC and particulate organic matter), microbial variables (picoplankton and picophytoplankton density and biomass) and phytoplankton biomass (as chlorophyll-a) were determined on a monthly basis from March 1997 to February 1998. The results of this study indicate that both fish farm and mussel culture did not alter significantly dissolved inorganic phosphorus and chlorophyll-a values, while inorganic nitrogen concentrations were higher in mussel farm a…

The barren Messinian Tripoli in Sicily and its palaeoenvironmental evolution: suggestions on the exploration potential

2016

New observations on the Sicily Messinian Tripoli have yielded a variably thick diatomitic, calcareous and shaly rock interval marked by an upwards disappearance of calcareous and siliceous plankton (barren lithosome), coexisting with a variability in vegetal remains and significant amounts of amorphous organic matter (AOM). Facies analysis associated with biostratigraphy and palaeoecology of the several field and borehole sections has been framed in a well-accepted chronological scheme that points to this barren interval coinciding with the stratigraphic upper and younger part of some Tripoli sections (bituminous Tripoli) located in the northern part of the study area. Biostratigraphically,…

Zooplankton biodiversity and community structure vary along spatiotemporal environmental gradients in restored peridunal ponds

2015

<p>Zooplankton assemblages in neighboring ponds can show important spatial and temporal heterogeneity. Disentangling the influence of regional versus local factors, and of deterministic versus stochastic processes has been recently highlighted in the context of the metacommunity theory. In this study, we determined patterns of temporal and spatial variation in zooplankton diversity along one hydrological year in restored ponds of different hydroperiod and age. The following hypotheses regarding the assembling of species over time were tested: i) dispersal is not limited in our study system due to its small area and high exposure to dispersal vectors; ii) community dissimilarity among …

Listeria monocytogenes Differential Transcriptome Analysis Reveals Temperature-Dependent Agr Regulation and Suggests Overlaps with Other Regulons

2012

Listeria monocytogenes is a ubiquitous, opportunistic pathogenic organism. Environmental adaptation requires constant regulation of gene expression. Among transcriptional regulators, AgrA is part of an auto-induction system. Temperature is an environmental cue critical for in vivo adaptation. In order to investigate how temperature may affect AgrA-dependent transcription, we compared the transcriptomes of the parental strain L. monocytogenes EGD-e and its Delta agrA mutant at the saprophytic temperature of 25 degrees C and in vivo temperature of 37 degrees C. Variations of transcriptome were higher at 37 degrees C than at 25 degrees C. Results suggested that AgrA may be involved in the regu…

Structure of planktonic microbial communities along a trophic gradient in lakes of Byers Peninsula, South Shetland Islands

2013

AbstractA systematic limnological survey of water bodies of Byers Peninsula (Livingston Island, South Shetland Islands) was carried out during the summer of 2001/02. Abundances of microbial plankton were determined which allowed a delineation of the pelagic food web structure. We also report the nutrient status of these lakes. We demonstrate the occurrence of a trophic gradient that extended from upland lakes (oligotrophic) to the coastal ones (eutrophic). The study shows that a lake's morphology regulates the relative importance of the pelagic and benthic habitats, whereas nutrient loads mainly determine its trophic status. Yet, some of the variability observed could be also a legacy of th…

Size-fractionated δ15N and δ13C isotope ratios elucidate the role of the microbial food web in the pelagial of Lake Tanganyika

2003

Food web structure of the pelagic community in Lake Tanganyika was studied using the stable nitrogen and carbon isotopes 15N and 13C. Size-fractionated seston, zooplankton, shrimps, medusae and fish were sampled in the northern part of Lake Tanganyika. Picoplankton fractions as well as cyanobacteria-dominated nano/microplankton fractions had very low nitrogen isotope signatures typical for nitrogen-fixing organisms. Fractions containing mainly dead organic matter (and associated bacteria) or nano/microalgae (chlorophytes and diatoms) had δ15N 2 to 4‰ higher. The low δ15N signatures of small cyclopoids and shrimps suggest they are feeding on nitrogen-fixing cyanobacteria (picoplankton or lar…

2020

The composition of phytoplankton community is the basis for environmental monitoring and assessment of the ecological status of aquatic ecosystems. Community composition studies of phytoplankton have been based on time-consuming and expertise-demanding light microscopy analyses. Molecular methods have the potential to replace microscopy, but the high copy number variation of ribosomal genes and the lack of universal primers for simultaneous amplification of prokaryotic and eukaryotic genes complicate data interpretation. In this study, we used our previously developed directional primer-independent high-throughput sequencing (HTS) approach to analyze 16S and 18S rRNA community structures. C…