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Papers by MIRELLA BORBA SANTOS FERREIRA COSTA

Regional Studies in Marine Science, 2021

Abstract Most of the studies on sea turtle nesting activity nowadays are focused on the impacts o... more Abstract Most of the studies on sea turtle nesting activity nowadays are focused on the impacts of climate change. However, there is a lack of studies gathering knowledge about the influence of coastal vulnerability to erosion and settlement to assess sea turtle nesting. This study aims to verify the influence of coastal erosion vulnerability over sea turtle nesting in five Brazilian Northeast beaches, in Pernambuco state, at Ipojuca coast. The main analyzed parameters were the urban settlement, coastal erosion indicators and the conservation status of the dunes by assessing shoreline change rates, backshore extension, vegetation cover and beaches morphodynamics associated aspects. Spearman’s rank correlation coefficient and tests of Kruskal–Wallis, Mann–Whitney, Shapiro–Wilk and Levene were employed as a set of statistical analyses. The results state that Eretmochelys imbricata is the predominant species that nests at the Ipojuca coast (93.2% of nesting females). There is a significant difference in the number of nests among the studied beaches (Kruskal–Wallis; p = 0.004). A strong and positive correlation between the backshore width and the number of nests was verified (Spearman’s rank correlation, rs = 0.881; p = 0.0002). The results indicate the preference for nesting on wave-dominated beaches, where the coastal reefs are absent and there is a well-developed backshore, mainly due to the lower urban settlement in these areas. Thus, efforts focused on preserving nesting beaches, especially those under high urbanization, are a key factor for sea turtle preservation.

Estuaries and Coasts, 2019

Reefs are known to provide coastal protection and important ecosystem services for many coastline... more Reefs are known to provide coastal protection and important ecosystem services for many coastlines around the world. Physical processes such as wave damping, sediment transport and nearshore hydrodynamics are closely related to the coastal protection services provided by reefs. The steep-fronted bathymetries of reefs cause abrupt wave transformations and wave damping alongshore, while reef roughness has an important contribution to coastal protection. Five Latin-American case studies are presented to illustrate the coastal protection offered by reefs and their contribution to wave damping. The methodologies applied (e.g. numerical modelling, field measurements) and reef conditions (e.g. reef degradation scenarios and contribution of reef roughness) are listed. Considerable efforts have been made towards diagnosing, understanding and modelling the hydrodynamic transformations induced by reefs. Based on physical and field surveys, roughness and friction parameters were derived in order to implement calibrated and validated numerical models. Discussion on the advantages and disadvantages of the different models applied in the study cases is provided as well as on the needs of highlighting physical processes and the analysis of reef hydrodynamics for supporting appropriate ecosystem-based management.

Pan-American Journal of Aquatic …, 2010

Ocean and Coastal Research

Processes on atolls and coral reef lagoons are defined by local wave and tide climates. Based on ... more Processes on atolls and coral reef lagoons are defined by local wave and tide climates. Based on the reconstruction of lagoon wave climate by downscaling offshore historical wave information, this study aims to assess the wave climate and wave extremes on a mesotidal atoll lagoon (Rocas Atoll, Brazil). Results show that the transformation of offshore waves, when propagating into the lagoon, results in a different and far more homogeneous wave climate. Atoll morphology and tides play a key role in controlling the directional and energy characteristics of the lagoon wave climate. Refraction processes and the reef passage make the side protected from the dominant SE waves the most energetic zone for lagoon wave propagation. Lagoon waves tend to propagate in opposite directions to offshore wind waves, showing the refraction effect of approaching waves when crossing the atoll rim and the channel. The tidal effect on the dissipation process is also a filter for extreme wave conditions. We highlight the dependence of the resulting lagoon wave climate on atoll morphology, thereby addressing its implications to geomorphological process inside the atoll.

Continental Shelf Research, 2022

Earth's Future, 2017

Large parts of tropical coastlines are influenced by the presence of reefs that shape its coastli... more Large parts of tropical coastlines are influenced by the presence of reefs that shape its coastline. Wave attenuation crossing reefs as they approach the coast results in accretionary coastal features developed in its shadow zones. With the aim of assessing the level of wave exposure of the coastline under different sea‐level rise scenarios, numerical modeling experiments have been designed considering a coastline segment of approximately 450 km in northeast Brazil. Results show the distribution of wave power along the area of interest, with higher values being found in areas without reefs. However, when considering sea‐level rise scenarios, it is behind the reefs where the maximum differences in wave power are observed. The increase in the free surface over the reef structures as a result of rising sea level reduces the wave attenuation effects caused by these structures. Thus, the waves hit the shore with greater force in the shadow zone protected by the reef. Here, we demonstrate...

$Research paper thumbnail of Wave refraction and reef island stability under rising sea level$

Global and Planetary Change, 2019

The location and stability of low-lying carbonated reef islands are closely related to wave refra... more The location and stability of low-lying carbonated reef islands are closely related to wave refraction over reef platforms, which create low energy wave convergence zones favorable for sediment deposition. Although there is great concern about the stability of reef islands in future decades, few studies have attempted to assess the effects of sea-level rise on wave refraction patterns and the migration of wave convergence zones, which may promote changes in island positions. To investigate the mechanisms of wave refraction over a shallow lagoon atoll (Rocas Atoll), we performed a detailed topo-bathymetric survey to simulate wave propagation for different water levels and wave conditions considering the complex atoll morphology. Our results show that the locations of convergence zones are not only influenced by wave direction and wave interactions with the elliptical reef shape but also controlled by topographic variations in the reef structure. In particular, the presence of a wide reef passage on the leeward margin of Rocas Atoll has an important role in the atoll wave refraction pattern. Model simulations show a displacement of the wave convergence zone and increase in wave energy under increased sea

Earth Surface Processes and Landforms, 2017

Reef islands are morphologically dynamic features located on atolls and platform reefs that are v... more Reef islands are morphologically dynamic features located on atolls and platform reefs that are very sensitive to wave‐induced processes on different timescales. The planform morphological evolution of reef islands is widely described; however, the mechanisms of the volumetric variations in response to wave energy are still poorly documented. To assess their multitemporal vertical and horizontal mobility, we performed a series of synchronous measurements of the volumetric changes and incident wave energies at two reef islands and a shingle bank at the Rocas Atoll in the South Atlantic Ocean. The results show the differences in the magnitudes and locations of the sediment mobility between the reef islands. Whereas one island remained stable on all timescales, with only small volumetric changes concentrated at its extremities, the other island (Farol Island) showed high mobility, especially during the energetic northern swell season. The gross volumetric change reached 10.03 × 103 m3 ...

Geomorphology, 2016

This study presents data from field experiments that focus on the influence of coral reef geometr... more This study presents data from field experiments that focus on the influence of coral reef geometry on wave transformation in the Metropolitan Area of Recife (MAR) on the northeast coast of Brazil. First, a detailed bathymetric survey was conducted, revealing a submerged reef bank, measuring 18 km long by 1 km wide, parallel to the coastline with a quasi-horizontal top that varies from 0.5 m to 4 m in depth at low tide. Cluster similarity between 180 reef profiles indicates that in 75% of the area, the reef geometry has a configuration similar to a platform reef, whereas in 25% of the area it resembles a fringing reef. Measurements of wave pressure fluctuations were made at two stations (experiments E1 and E2) across the reef profile. The results indicate that wave height was tidally modulated at both experimental sites. Up to 67% (E1) and 99.9% (E2) of the incident wave height is attenuated by the reef top at low tide. This tidal modulation is most apparent at E2 due to reef geometry. At this location, the reef top is only approximately 0.5 m deep during mean low spring water, and almost all incident waves break on the outer reef edge. At E1, the reef top depth is 4 m, and waves with height ratios smaller than the critical breaking limit are free to pass onto the reef and are primarily attenuated by bottom friction. These results highlight the importance of reef geometry in controlling wave characteristics of the MAR beaches and demonstrate its effect on the morphology of the adjacent coast. Implications of differences in wave attenuation and the level of protection provided by the reefs to the adjacent shoreline are discussed.

Coral Reefs, 2016

Most of the atolls found worldwide are under microtidal regimes, and their circulation mechanisms... more Most of the atolls found worldwide are under microtidal regimes, and their circulation mechanisms are widely documented and well known. Here, we describe the flushing mechanisms of a small-sized mesotidal atoll, based on water-level, wave and current data obtained during two different periods (total of 60 d). Rocas is the only atoll in the South Atlantic Ocean and is built primarily of coralline algae. Two reef passages connect the atoll lagoon to the ocean. Synchronous current profilers were deployed at the two reef passages, one inside and one outside the atoll, to characterize the influence of tides and waves on the circulation. Results showed that wind waves drove a setup on the exposed side of the atoll and that currents were predominately downwind, causing outflow at both reef passages. Waves breaking on the windward side supplied water to the atoll causing the lagoon water level to rise above ocean water level, driving the outflow. However, unlike microtidal atolls, at Rocas Atoll the water level drops significantly below the reef rim during low tides. This causes the reef rim to act as a barrier to water pumping into the lagoon by waves, resulting in periodic activation of the wave pumping mechanism throughout a tidal cycle. As result, inflow occurs in the wider passage during 27% of each tidal cycle, starting at low tides and reversing direction during mid-flood tide when the water level exceeded approximately 1.6 m (while overtopping the atoll's rim). Our findings show that tides play a direct role in driving circulation on a mesotidal atoll, not only by modulating wave setup but also by determining the duration of wave pumping into the lagoon.