491 research outputs found
Water and Sediment Temperature Dynamics in Shallow Tidal Environments
No full textThe purpose of the present study is to investigate the water and sediment temperature dynamics in shallow coastal environments. Indeed, water and sediment temperature dynamics are a first order control of many physical and biological processes in aquatic ecosystem, driving the short and long term evolution of the ecosystem.
Given the scarcity of studies and data from the literature that investigate in particular the heat fluxes at the sediment-water interface (SWI), we conceived and performed an ad hoc, one-year-long field campaign was performed in the Venice lagoon to collect water and sediment temperature data. The collected data show that, in our study site, temperature is uniform within the water column, and enabled us to estimate the net heat flux at the sediment-water interface. Based on these results we developed a "point" model for describing the temperature dynamics of the sediment-water continuum in shallow tidal environments. Modeling the flux at the SWI as the sum of a conductive component and of the solar radiation reaching the bottom, we found the latter being negligible. Our analysis further revealed that, in general, horizontal advection driven by tidal currents is an important process also at our study site despite we placed it quite close to a divide. For applying the "point" model we therefore selected, in our data set, only periods when advection is negligible, that correspond to periods characterized by neap tide and small temperature difference between sea and lagoon. The results we obtained following our numerical approach are quite satisfactory showing the capability of the model of reproducing, in the selected conditions, the temperature dynamics both in the water column and within the sediments. Both the analysis of the data and model results show that the heat exchange between water and sediment is crucial for describing sediment temperature but plays a minor role on the water temperature. This observation suggests that, as a first approximation, the water temperature dynamics can be modeled neglecting the heat exchange between water and sediments.
Using the developed numerical model we further investigated the effect of different turbidity conditions of the water column on the water and sediment temperature and on the photosynthetic capacity of the microphytobenthos (MPB), i.e. communities of microalgae commonly present in coastal environments and colonizing the uppermost layer of bed sediments. We found that the water temperature dynamics is poorly affected by the different conditions investigated, while the sediment temperature variation is significant, especially for very shallow water depth (i.e. ≤0.5 m). Considering the average annual budget, the photosynthetic rate of the MPB is found to be better promoted by clear water conditions, being the light availability the major limiting factor for the photosynthetic process. These results suggest the possibility of investigating a positive feedback between water column turbidity and the MPB proliferation, driven by its photosynthetic capacity. In fact, the abundance of MPB provides a bio-stabilization of the sediment bottom, creating a biofilm that limits sediment resuspension and thus reduces the water column turbidity
Data for: Water and sediment temperature dynamics in shallow tidal environments: the role of the heat flux at the soil-water interface.
No full textWater and sediment temperature data collected in a shallow tidal flat located in the Northern part of the Venice lagoon (see figure 1 in the manuscript).The bottom elevation at the measuring station is 0:65 m below mean sea level, and the local tidal range is about 0.80 m during a spring tide and 0.50 m during a neap tide.5 sensors (ControlByWeb, Xytronix Inc. Utah, USA) were deployed in the sediment (depth of 5, 25, 50, 100, and 150 cm below the sediment surface) and 4 sensors in the water column (10, 40, 70, 100 cm above the sediment surface). Data were collected with a 5 minutes resolution
On the feedback between water turbidity and microphytobenthos growth in shallow tidal environments
No full textShallow tidal environments (e.g. bays, estuaries, lagoons) represent one of the most productive ecosystems in the
world, and they are threatened by current climate change and increasing human pressure. Monitoring the bio-morphodynamic
evolution of these environments is therefore a crucial task that requires a detailed and holistic scrutiny. The present study aims to
investigate the temperature of the water–sediment continuum, its effect on the related microphytobenthos (MPB) growth and the
related bio-stabilization of the bed sediment surface under different water depth and water turbidity conditions. We investigated
the vertical energy transfer and the temperature dynamics by applying a 1-D model to a shallow coastal lagoon. Our results show
that the water temperature does not substantially change under different turbidity conditions, whereas the sediment temperature
exhibits important changes. Two major factors driving the MPB photosynthetic growth are the sediment surface temperature and
the light availability at the sediment bed, which can both be computed using the vertical energy transfer model. We observed
that, in general, clear water conditions better promote MPB growth over the entire year. The limiting factor for the photosynthetic
process is usually the light availability at the bottom, which increases under clear water conditions. As MPB provides a
bio-stabilizing effect on the bed sediments by producing a biofilm on the sediment surface that reduces sediment resuspension,
our results suggest a positive feedback between MPB growth and water column turbidity. Furthermore, MPB growth and the related
sediment bio-stabilization are clearly affected by the seasonal variation of surface sediment temperature and light availability. This
seasonal variation of MPB growth rate and surface sediment bio-stabilization must be considered when studying the long-term
morphodynamic evolution of tidal environments
Short-term sedimentation on salt-marsh surface: analysis of the interplay between fair-weather conditions and storm events
No full textHow do storm events and fair-weather conditions affect sedimentation patterns on salt marshes?
No full textDinamica della temperatura in corpi idrici poco profondi: importanza dello scambio termico con il fondale
No full textL’obiettivo del presente contributo riguarda nello specifico lo studio della dinamica della temperatura
in bacini poco profondi, approfondendo in particolare il ruolo dello scambio termico con il fondale. A tale
scopo è stata concepita e realizzata una campagna di misure ad hoc in laguna di Venezia. La Laguna
rappresenta infatti un perfetto esempio dell’ambiente che si desidera descrivere, ampiamente studiato sia
per la sua rilevanza storica che per la complessità del suo ecosistema. La Laguna è un bacino poco
profondo, caratterizzato da una superficie di circa 550 km2, una profondità media di circa 1.5 m e
un’escursione di marea di circa 1.0 m, che comunica con il mare per mezzo delle tre bocche di porto di
Lido, Malamocco e Chioggia.
Le misure eseguite hanno permesso di caratterizzare il flusso termico all’interfaccia acqua fondale e di
sviluppare un modello puntuale per descrivere l’evoluzione della temperatura della colonna d’acqua.
Messo a punto e testato il modello puntuale, il passaggio successivo sarà quello di sviluppare un modulo
per la descrizione della dinamica della temperatura della colonna d’acqua da accoppiare in un modello
bidimensionale della Laguna che permette di modellare l’idrodinamica, la generazione delle onde da
vento, il trasporto dei sedimenti e l’evoluzione del fondale (Carniello et al., 2014). Questo permetterà di
ricostruire l’evoluzione spaziale e temporale della temperatura dell’acqua in laguna di Venezia,
considerando anche il trasporto convettivo di calore inevitabilmente trascurato nel modello puntuale
temperature dynamics in very shallow water bodies: the role of heat fluxes at the soil-water interface
No full textWater Temperature represents one of the crucial factors driving the ecological processes in water bodies. Many contributions are available in the literature that describe temperature dynamics in deep basins as lakes or seas. Those basins are typically stratified which makes important to represent the vertical profile of the water temperature. Dealing with shallow water bodies, such as rivers, shallow lakes and lagoons, simplifies the problem because the water temperature can bu assumed uniform in the water column. Conversely, the heat exchange at the soil-water interface assumes an important role in the water temperature dynamics. Conversely, the heat exchange at the soil-water interface assumes an important role in the water temperature dynamics. Notwithstanding, very few studies and data about this process are available in the literature. In order to provide more insight on the soil contribution to water temperature dynamics, we performed ad hoc field measurements i the Venice lagoon. We selected a location on a tidal flat in the northern part of the lagoon, close to the Sant'Erasmo Island, where we measured the temperature within the first 1.5 m of the soil. We used the data to characterize the heat flux at the water-soil interface in different periods of the year and to develop a "point" model for describing the evolution of the temperature in the water column. The insight on the process provided by the data and by the point mode: i) enabled us to determine the soil thermal properties; ii) confirms the uniform profile of the water temperature in the water column; iii) demonstrates that the heat flux at the soil-water interface is comparable with other fluxes at the air-water interface and iv) highlights the important role exerted by advective water fluxes
Sediment deposition patterns on salt marshes: the role of standard conditions and storm events
No full textWater and soil temperature dynamic in very shallow tidal environment: the role of the heat flux at the soil-water interface
No full textWater and soil temperature are crucial factors affecting
the biological and ecological processes in enclosed or
semi-enclosed ecosystems like lakes, estuaries, bays and
lagoons (Guarini et al. (2000)). The understanding of
these processes is relevant considering the role of inland
water bodies in processing a large amounts of organic carbon
(Battin et al. (2009)). Furthermore, water temperature
of inland and coastal water bodies is one of the main factor
that can be considered as a signal of climate change
(Adrian et al. (2009)).
The aim of this study is to investigate the evolution of the
temperature profile in the water column and within the
soil in a shallow tidal environment. In particular, we want
to analyze the heat exchange at the interface between soil
and water (SWI), its role for the evolution of the temperature
in the water column and of the vertical temperature
profile within the soil. The present study aims at investigating
the temperature dynamics at the sub-daily time
scale and is based on the analysis of temperature data collected
in the Venice lagoon, located in the North East of
Italy and characterized by a Mediterranean climate
Monitoring temperature dynamics in shallow tidal lagoons combining in situ observations, satellite retrievals, and numerical modeling
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