Dataset for modeling the hydrological patterns and salinity fluctuations of a Mediterranean confined coastal lagoon system (La Pletera salt marsh area, NE Spain).

This dataset is related to the research article entitled "Effects of morphology and sediment permeability on coastal lagoons' hydrological patterns" (W. Meredith, X. Casamitjana, X. D. Quintana, A. Menció) [1], and was obtained in the La Pletera salt marshes in Catalunya between 2016 and 2019, to model the water balance and salinity fluctuations of 6 permanent lagoons using the General Lake Model (GLM). As no inflow and outflow data were available, water level and bathymetric data were used to calculate the net balance of inflows and outflows according to the observed daily volume fluctuations. Meteorological data were obtained from the L´Estartit Meteorological station north of the lagoons. Daily solar radiation was measured in Mas Badia (La Tallada, ∼10km from the La Pletera) in 2016 and 2017 and in situ with radiation sensors in 2018 and 2019. Together with the bathymetry and water levels of the lagoons, calculated inflows and calibrated salinity and temperature data are provided to further confined coastal lagoons system modeling where inflow and outflow data are not available. Meteorological data and observed lagoon salinity and temperature are provided for comparison. As this is one of the few datasets that have modeled coastal water bodies less than 3m in depth using the GLM, the data presented here can be useful in stress testing the General Lake Model to other coastal lagoon systems, as well as to other global aquatic ecosystems.

Interactions between Fragmented Seagrass Canopies and the Local Hydrodynamics.

The systematic creation of gaps within canopies results in fragmentation and the architecture of fragmented canopies differs substantially from non-fragmented canopies. Canopy fragmentation leads to spatial heterogeneity in hydrodynamics and therefore heterogeneity in the sheltering of canopy communities. Identifying the level of instability due to canopy fragmentation is important for canopies in coastal areas impacted by human activities and indeed, climate change. The gap orientation relative to the wave direction is expected to play an important role in determining wave attenuation and sheltering. Initially we investigated the effect of a single transversal gap within a canopy (i.e. a gap oriented perpendicular to the wave direction) on hydrodynamics, which was compared to fully vegetated canopies (i.e. no gaps) and also to bare sediment. The wave velocity increased with gap width for the two canopy densities studied (2.5% and 10% solid plant fraction) reaching wave velocities found over bare sediments. The turbulent kinetic energy (TKE) within the gap also increased, but was more attenuated by the adjacent vegetation than the wave velocity. As expected, denser canopies produced a greater attenuation of both the wave velocity and the turbulent kinetic energy within an adjacent gap, compared to sparse canopies. Using non-dimensional analysis and our experimental data, a parameterization for predicting TKE in a canopy gap was formulated, as a function of easily measured variables. Based on the experimental results, a fragmented canopy model was then developed to determine the overall mixing level in such canopies. The model revealed that canopies with large gaps present more mixing than canopies with small gaps despite having the same total gap area in the canopy. Furthermore, for the same total gap area, dense fragmented canopies provide more shelter than sparse fragmented canopies.

Filtering capacity of Daphnia magna on sludge particles in treated wastewater.

A great challenge in water reuse is the reduction of suspended particle concentration in wastewater. In particular the reduction of the presence of small particles in suspension which cause a cloudy appearance in the water and, which also make disinfection difficult. The present study evaluates the filtering capacity of a population of Cladodera (Daphnia magna) in secondary effluents from a wastewater plant. The study was performed in both a mesocosm and the laboratory, in an effort to compare the grazing on sludge particles by Daphnia versus the settling rate of those sludge particles. The particle volume concentration of small particles (with a diameter below 30 µm) was used to evaluate the efficiency of the proposed biotreatment system for small particles. Both laboratory and mesocosm results showed that the suspended particle volume concentration decreased with time due to the Daphnia filtration, with the highest reduction in experiments carried out with the highest Daphnia concentration. In the mesocosm experiments, the Daphnia diameter was also found to play an important role, with an allometric relationship between the filtering rate of Daphnia and the Daphnia nondimensional diameter. In laboratory experiments, the effect of D. magna in the suspended concentration of small particles was in the range of 10.1-29.4%, according to the range of Daphnia concentration of 10-50 ind/l. For laboratory experiments, sedimentation was responsible for 62.2% of the suspended particle concentration reduction. For the mesocosm experiments, the reduction in the particle concentration attributed to the Daphnia filtration ranged between 2.5 and 39%, corresponding to Daphnia concentrations of between 5 and 100 ind/l (i.e. biovolumes of 8-60 ind/l).

A study of the evolution of the particle boundary layer in a reservoir, using laser particle sizing.

The dynamics of the particle boundary layer in the Boadella reservoir was studied using an in situ laser optical particle-sizing instrument. This layer was found at the bottom of the reservoir from summer until the end of the year, when the reservoir was fully mixed. Most of the particles in this layer are remnants of the summer algae bloom and are trapped in the boundary layer due to the thermal stratification. The phytoplankton bloom is mainly composed of diatoms, with diameter d approximately 5 microm and green algae with diameter d approximately 15 microm. Inorganic particles and decomposed organic particles with d < 3 microm are also encountered in the boundary layer. On the other hand, particles with diameter between 30 and 100 microm are mostly found in the epilimnion of the reservoir. These are a mixture of aggregates of inorganic particles, colonies of phytoplankton, zooplankton, detritus, etc. Different mixing events occurring during autumn resuspended the small particles in the boundary layer, while the greater particles settled down. The extent of the resuspension has been parameterized with a non-dimensional number that balances the stress across the interface and the strength of the stratification.

Seasonal development of a turbid hydrothermal lake plume and the effects on the fish distribution.

Measurements of the suspended particle concentration in a lake demonstrate the presence of a turbid hydrothermal plume. The plume, generated from a warm source develops upward carrying a suspension of particles from the bottom. It is found that the vertical structure of the plume depends on the stratification of the water column, which in turn depends on the seasonal meteorological conditions. During the stratified period of the lake, the plume is constricted to the hypolimnion zone. At the beginning of the summer season, the plume reaches the bottom of the metalimnion meanwhile at the end of this season the plume does not. In the mixed period of the lake, the plume develops in the whole water column and reaches the surface of the lake, where particles accumulate and spread around the center. Measurements of the vertical fish distribution in the stratified period show that the plume can constrict the fish habitat due to an increase of suspended particles transported by the plume.