Thesis (M.S.)--University of North Carolina at Wilmington, 2004. / Includes bibliographical references (leaves : [35]-41).

Understanding the biogeography of reef fish assemblages is paramount to reef conservation, management, and conducting appropriate population survey designs. Reef fish assemblages are a multispecies complex of reef-associated fish and are shaped by multiple environmental and biological factors (e.g. temperature, depth, benthic habitat, and topographic relief), which determine the species constituents residing in an area. Assemblages typically change with latitude where the number of families, genera, and/or densities of species specific to warmer climates decrease poleward into colder climate regimes. The Florida Reef Tract (FRT) extends for 595 km from the Dry Tortugas in the south-west to Martin County in the north, crossing a sub-tropical to temperate climate transition. This study investigates the biogeography of reef fish assemblages throughout the FRT to determine if they correspond to previous regional delineations that were primarily based on coastal geomorphology. Multivariate density analyses show that depth, habitat, relief, and region are major factors in determining the assemblages. Four main ecoregions were evident based on depth, benthic habitat, relief and latitudinal region: Dry Tortugas (DT), Florida Keys (FK), Southeast mainland (SE), and Bahamas Fracture Zone (BF). DT split into four biogeographic assemblage regions primarily based on depth, and relief. FK split into five biogeographic assemblage regions with a sixth extending through Broward County primarily based on depth, habitat type, and relief. SE split into four biogeographic assemblage regions primarily based on depth, and region. BF split into three biogeographic assemblage regions primarily based on depth, and region. These sixteen assemblages represent the current composition of reef fish based on four factors. Numerous other factors also affect reef fish assemblages (e.g. past and present fishing pressure, mangrove nursery habitat, and coral death) that were not part of the analysis but are discussed. The final reef fish assemblage regions were associated with previous benthic habitat maps in order to view their spatial extent. Having a map of current biogeographic reef fish assemblages serves as a baseline and allows more accurate management and monitoring of future reef fish populations.

Relatively little is known about either the biological (i.e., predation) or physical (i.e., current, sedimentation) effects that artificial reefs may have on surrounding benthic infaunal communities. Following deployment of artificial reefs (concrete boulders) between the first and second reefs off Fort Lauderdale, Florida, on 30 October 2009, sediment cores were taken at 4 distances along three replicate 10-m transects on 13 and 26 September 2013, and 24 and 25 May 2014 at each of four artificial reef sites and four of their adjacent natural reef sites using SCUBA. Infauna (>0.5mm) were extracted from the sediment and identified to the lowest possible taxonomic level. Statistical analysis (PRIMER, PERMANOVA, SIMPER) focused on four main variables: type of reef, year, site, and distance. Type of reef, year, and site was significantly different between samples, while distance did not affect density. There is a clear separation of communities between the artificial and natural reefs. From 2013 to 2014, a slight shift occurred between communities suggesting the artificial reef community composition became slightly more similar to the natural reef. All four artifical reef sites were more taxonomically distinct at the phylum and class level then the natural reef, which had higher diversity, higher species richness and more low-density taxa. This two year study provides insight on infauna communities four and five years out from deployment, but follow up monitoring in 3-5 years could shed light on whether these patterns of shift to more similar assemblages between reefs will continue as the artificial reef matures. Environmental data collection including longer time-series datasets, longer transects, and physical and geological data could provide more knowledge of how the artificial reef infaunal communities are changing over time.

Spur and groove (SaG) morphology is a common ornamentation of reef-armored Holocene carbonate platform margins. Composed of margin-normal promontories constructed of coral framestone, termed “spurs”, interleaved with similarly orientated gullies, “grooves”, this morphology varies based on a host of physical controls. Primarily, the surrounding oceanographic conditions as well as the size and shape of the platform the SaG is encompassing, directly influence the development and organization of SaG. Since grooves act as conduits for carbonate sediment transport, this study seeks to examine the relationship between SaG organization dictated by platform size and shape and how that in turn influences platform-top sedimentation. The analysis reveals trends that suggest platform shape plays a larger role than platform size in allowing highly organized SaG to develop on multiple margins around the platform. In turn, those trends would suggest these sites to have more stable platform top sediment deposits. However, many variables go in to the creation and maintenance of platform top cays. While this study enhanced the current understanding of how oceanographic conditions influence SaG development and organization, expanding on the concepts and results found in this study coupled with coring data of SaG and platform-top cays, could further link the connection between SaG and sediment transport.

This study conducted the first high-resolution investigation of the ichthyofaunal assemblages on a high-latitude coral reef in the Western Indian Ocean (WIO). Two-Mile reef, in South Africa, is a large, accessible patch-reef, and was selected as a candidate study area. Although the effect of season in structuring coral reef fish communities is most-often overlooked, the relationship between these fish communities and their habitat structure has been investigated. In South Africa, however, neither of these potential community-level drivers has been explored. As coral reefs worldwide are faced with high levels of usage pressure, nondestructive underwater visual census (UVC) techniques were identified as the most appropriate survey methods. This study had two primary aims that were; (1) to identify the most suitable technique for the UVC of coral reef fishes, and to test variations of the selected technique for appropriateness to implementation in long-term monitoring programs, and (2) to determine if possible changes to ichthyofaunal community structure could be related to trends in season and/or habitat characteristics. A review of the literature indicated that the most appropriate UVC method for surveying epibenthic coral reef fishes is underwater transecting. To compare the traditional slate-based transects to variations that implement digital image technology, slate transects were compared to a first-attempt digital photographic transect technique, and digital videographic transects. Videographic transects produced the most favourable species richness, abundance, and standard deviations of the three techniques. Diversity was not significantly different between transect techniques. The minimum required sample size was lowest for videographic transects (17 replicates), intermediate for photographic transects (27 replicates) and highest for slate transects (37 replicates). Videographic and photographic transects required greater analysis time to generate counts, but required lower observer training time. While videographic transects produced the lowest proportion of species considered unidentifiable, all three transect techniques showed similar functionality to surveying epibenthic coral reef fishes. Videographic transects were therefore identified as the most appropriate UVC technique for this study. Videographic transects at shallow (6 – 14 m), intermediate (14 – 22 m) and deep (22 – 30 m) depths in mid-winter and mid-summer, sampled a total of 41 families consisting of 209 species and 18172 individuals, dominated by pomacentrids in abundance and labrids in richness. The fish assemblages on Two-Mile Reef were found to be similar in composition to lower-latitude WIO reefs. Overall ichthyofaunal abundance and richness was significantly higher in summer than in winter, and was higher at shallow sites than at intermediate and deep sites. A multivariate approach confirmed differences between seasons at shallow depths but not between seasons at intermediate and deep depths. The fish assemblages on Two-Mile Reef can therefore be described as being comprised of four relatively distinct communities: a shallow, winter community; a shallow, summer community; a year-round intermediate community; and a year-round deep community. The distributions of discriminating species indicated that high abundances of the algal-feeding pomacentrids are observed only at shallow and intermediate sites while high abundances of the zooplanktivorous serranid subfamily, the Anthiinae, are observed predominantly at deep sites. Assessment of all measured supplementary variables indicated that of all factor combinations, observed patterns could be ascribed most strongly to depth. Quantification of reef characteristics indicated that as depth increases, habitat complexity decreases, benthic communities shift from dense coral domination to sparse sponge domination, and algal biomass and cover decreases. The ability of the videographic transect technique to detect changes in community structure with season and depth indicates that season and depth should be accounted for in future high-latitude ichtyofaunal surveys, and that the videographic transect technique is suitable for implementation in long-term monitoring programs on coral reefs. The similarity in fish assemblages between Two-Mile Reef and lower latitude regions suggests that the protocol for surveying epibenthic coral reef fishes, resulting from this study, is relevant throughout the continental WIO.

Nitrogen (N) has traditionally been regarded as the primary limiting nutrient to algal growth in marine coastal waters, but recent studies suggest that phosphorus (P) can be limiting in carbonate-rich environments. To better understand the importance of P. alkaline phosphatase activity (APA) was measured in reef macroalgae in seven counties of south Florida ; several significant trends emerged : 1) APA decreased geographically from the highest values in Dada>Monroe>Palm Beach>St. Lucie>Broward>Martin>Lee counties 2) APA varied temporally with increasing nutrient-rich runoff in the wet season 3) APA varied due to taxonomic division Phaeophyta>Rhodophyta>Chlorophyta 4) Nutrient enrichment experiments demonstrated that increased N-enrichment enhanced P-limitation while increased P decreased P-limitation. These results suggest that high APA observed in carbonate-rich waters of Dade County and low APA in Broward County resulted from high nutrient inputs associated with anthropogenic nutrient pollution. / by Courtney Kehler. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Wave and tides are important drivers of circulation, sediment transport and water exchanges between ocean and lagoon in atolls, which in turn, affect the formation and stability of reef islands. Through a combination of field measurements and numerical modelling, this thesis examines the wave- and tidally-induced processes at Rocas Atoll and their implications on sediment dynamics. This comprehends the morphological responses of reef islands, including the effects of sea level rise. Wave, current, tide and topo-bathymetric data were collected during three expeditions to Rocas Atoll, totaling 75 days of in situ measurements. A spectral wave model has been implemented and validated for the Rocas Atoll. Our results demonstrated that the mechanism of circulation and the wave propagation that affects the reef islands morphology are controlled by the interaction of wave climate with the atoll topography. Being under mesotidal setting, there is a strongly tide modulated process in Rocas. The offshore wave climate is dominated by southeast trade wind wave and swell from south and north mid-latitude hemispheres. The swell occurrence has a marked seasonality whereas the southeast wind waves persist during the whole year. Offshore waves are filtered by the reef rim resulting in a more homogenous lagoon wave climate, which is controlled by tide and reef topography. Offshore extreme events are promoted by energetic swells, either from north or south hemispheres. However, extreme events in the lagoon only occur when such offshore events are combined with spring high tide. Wind waves that persistently break on the windward side of the atoll plays an important role on the overall circulation. They pump water into lagoon creating wave- generated currents that flow from the windward to the leeward side of the atoll. A water level threshold exists due to the large tidal oscillation, blocking inflow by wave pumping at lower water levels. This results in periodic variations in the relative importance of tidal controls in lagoon circulation along a tidal cycle interval. Such mechanism described for Rocas Atoll can be extended to other similar mesotidal atolls. The reef islands are located on the leeward of the atoll and present higher morphological changes in response to northern swell. However, no significant net erosion was observed on daily and seasonal time scale, with eroded parts being compensated by accretion on adjacent parts. Conversely, Farol Island had a substantial accretion on a decadal time scale changing from an elongated ridge morphology to horse-shoe shape with three ridges and an intertidal central depression. The changes in the planform configuration were characterized by ocean shoreline erosion and lagoon shoreline progradation, representing net lagoonward migration. Cemitério Island remains stable for the same period, anchored by exposed consolidated sediments on both shores. Results indicate the resilient nature of reef islands and their potential adjustment to changes in boundary conditions. In terms of wave refraction, Rocas Atoll works as a platform reef due to its morphology. Wave vectors converge mainly on the leeward side and an interference zone can be observed from the windward side trough the lagoon. Such refraction pattern controls the location of reef islands and shingle bank on Rocas. Sea level rise displaces the wave convergence zone according to the incident wave incidence climate (swell or wind wave). This indicates that under sea level rise scenarios areas prone to sediment accumulation may become less stable, although not implying in the erosion of reef islands. The results provided an unprecedented dataset for Rocas Atoll, which improves the understanding about the mechanisms that control its reef islands morphodynamics and their ability adapt to changes in boundary conditions. / Os processos induzidos por ondas e marés em atóis são importantes forçantes da circulação, transporte de sedimentos e troca de água entre a laguna e oceano, que por sua vez, afetam a formação e estabilidade das suas ilhas recifais. Através da combinação de modelos numéricos e experimentos de campo, este trabalho teve por objetivo o estudo dos processos induzidos por ondas e marés no Atol das Rocas e suas implicações na dinâmica de sedimentos das ilhas recifais, considerando os efeitos do aumento do nível do mar. Experimentos de campo forneceram séries temporais de ondas, correntes, mares e informações topo-batimétricas ao longo de três expedições ao Atol das Rocas, totalizando 75 dias de levantamentos. Um modelo numérico de propagação de onda foi implementado e validado para a região. Os resultados demonstram que o mecanismo de circulação e de propagação de ondas, que afetam as ilhas recifais, é controlado pela interação do clima de onda com a topografia do atol, sendo fortemente modulados pelas flutuações de meso-maré. O clima de ondas ao largo do atol é dominado por vagas formadas pelos ventos alísios de sudeste e por ondulações geradas em latitude médias de ambos os hemisférios. A incidência das ondulações no atol apresenta uma forte sazonalidade enquanto que a vagas de sudeste persistem ao longo do ano. As ondas ao largo são filtradas pela borda do atol, resultando em um clima de ondas na laguna mais homogêneo e controlado pela maré e topografia do atol. Eventos extremos ao largo são ocasionados por ondulações energéticas tanto do hemisfério sul quanto do hemisfério norte. No entanto, os eventos extremos na laguna só ocorrem quando os eventos energéticos ao largo ocorrem em conjunto com maré alta de sizígia. As vagas que quebram constantemente no lado do atol exposto ao vento são importante forçantes na circulação geral do atol. A partir do processo de quebra, elas são responsáveis por bombear água para a laguna, criando intensas correntes geradas por ondas que fluem do lado exposto para o lado protegido. Este processo, modulado pela maré, resulta em variações periódicas da importância relativa da maré no controle da circulação. Foi também observada a presença de ondas longas dentro da laguna (infragravitacionais) provocada pela quebra do espectro de ondas incidente no recife. Através desses dados, o volume de fluxo de troca de água e o coeficiente de atrito no Barretão foram estimados. O mecanismo descrito para Rocas pode ser aplicado em outros atóis semelhantes sob regime de mesomaré, os quais ainda hoje têm sido pouco estudados. As ilhas recifais estão localizadas no lado protegido do atol e apresentam maiores modificações morfológicas em resposta a incidência de ondulações de norte. No entanto, não foi observado um balanço sedimentar negativo em escala diária e sazonal, com partes erodidas da ilha sendo compensadas por acresção nas partes adjacentes. Em escala decadal, a Ilha do Farol apresentou substancial acréscimo em área (59.6% em 75 anos), modificando sua forma alongada para uma forma de ferradura com formação de uma depressão central. Durante esse processo, o lado da ilha voltado para o oceano foi erodido, enquanto que o lado da laguna foi acrescido, caracterizando uma migração da ilha para a laguna. Não foram observadas modificações significativas na ilha do Cemitério, a qual está estabilizada atualmente pela presença de sedimentos consolidados expostos nos dois lados da ilha. Os resultados indicam que as ilhas são feições resilientes, capazes de se ajustar as mudanças nas condições de contornos. No processo de refração das ondas, devido a sua morfologia, o Atol das Rocas funciona com uma plataforma recifal. Os vetores de ondas convergem no lado protegido e zonas de interferência podem ser observadas no lado exposto e na parte central da laguna. A localização das ilhas e do banco Zulu está relacionada com o padrão de refração, que promovem locais favoráveis à deposição de sedimentos no atol. O aumento do nível do mar promove um deslocamento na posição de convergência das ondas de acordo com o tipo de onda incidente. Isto indica que neste cenário futuro, as áreas deposicionais podem se tornar mais instáveis no atol promovendo o deslocamento das ilhas, mas não necessariamente em uma erosão generalizada. Os resultados obtidos no desenvolvimento deste trabalho forneceram uma série de informações inéditas para o Atol das Rocas permitindo elucidar questões importantes acerca da capacidade de modificações das ilhas recifais em resposta aos processos oceanográficos dominantes no atol.

The role of Serrivomer beanii in bathypelagic food webs is poorly known, but abundance and biomass estimates from the 2004 G.O. Sars MAR-ECO Expedition suggest it to have a high level of importance. MAR-ECO, a Census of Marine Life field project, has allowed us to increase our knowledge of S. beanii through spatial analysis, including the congeneric species Serrivomer lanceolatoides, and trophic analysis. Serrivomer beanii abundance and biomass exhibited a decreasing trend along the northern Mid-Atlantic Ridge from north to south. In terms of size, S. beanii was found to increase as distance from the ridge decreased, suggesting a topographic aggregation strategy. The diet of S. beanii consisted of crustaceans, cephalopods, and teleosts. The trophic results of this study reveal a likely "alternative" trophic pathway in the deep mid-North Atlantic, and perhaps other, bathypelagic ecosystems: higher trophic-level predators are supported by micronektonic invertebrates as primary prey. / by Megan E. Geidner. / Thesis (M.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

This thesis focuses on the investigation of reef communities of the Saint Peter and Saint Paul´s Archipelago (SPSPA) across an euphotic/mesophotic depth gradient. Sampling was performed on shallow and mesophotic areas (0 to 90 m depth) using SCUBA and a Remotely Operated Vehicle (ROV). The present work is composed of four chapters: Chapter 1 deals with the quantitative assessment of reef fish communities, which were divided in three distinct communities associated with different depth strata. Clear shifts in habitat use and in size-frequency distributions were recorded for some species. Abundance of black-corals and depth were the most important factors affecting the structure of fish communities, with a clear association of fish with branching black-corals in the mesophotic zone. Chapter 2 presents the first detailed qualitative assessment of benthic communities of the SPSPA. The influence of biotic and abiotic variables shaping the structure of the benthic communities was evaluated. A total of 77 benthic taxa belonging to six major functional groups were recorded. Macroalgae was the richest group (41 infrageneric taxa), with 17 new records for the SPSPA. Turf algae were the most abundant group on both shallow and mesophotic reefs. Two distinct communities were detected: a shallow one composed primarily by the zoanthid Palythoa caribaeorum (Duchassaing and Michelotti, 1861), the fleshy alga Caulerpa racemosa (Forsskål) J. Agardh, crustose coralline algae (CCA) and Bryopsis spp., and another deeper community dominated by CCA, bryozoans and scleractinian corals. Abiotic variables were the most important predictors of benthic community structure. Chapter 3 brings information on abundance, distribution size and associated fauna (epibionts) of black-corals. Although two species of black-corals, Tanacetipathes hirta (Gray, 1857) and T. thamnea (Warner, 1981), are known to occur in the SPSPA, they are undistinguishable underwater. Epibiosis, mainly by zoanthids and entanglement by fishing monofilament were important factors negatively affecting the health of black-coral colonies. Black-corals were intensively used as refuge by reef fish, especially by the endemic oblique butterflyfish Prognathodes obliquus (Chaetodontidae). A single black-coral colony repeatedly visited and monitored for ten years showed a decrease in vitality since the first observation, mainly related to fouling by algal detritus and entanglement by fishing monofilaments. Chapter 4 discusses the ecology (abundance, distribution and habitat preferences) of the fireworm Hermodice carunculata, a major predator on mesophotic zone of SPSPA. A total of 278 individuals of bearded fireworm were observed, with significant difference in abundance between euphotic and mesophotic zones. A direct association of H. carunculata with black-corals (Tanacetipathes spp.), the scleractinian Madracis decactis and depth was found. A final session with concluding remarks wraps up information on the ecology of Mesophotic Reef Ecosystems highlighting their possible importance for the stability and persistence of reef fish and benthic communities of the SPSPA, which are under threat of overfishing and climate change, thus requiring urgent protective measures. / O tema central desta tese é estudar a ecologia de comunidades recifais ao longo do gradiente de profundidade no Arquipélago São Pedro e São Paulo (ASPSP), com ênfase nos Ecossistemas Recifais Mesofóticos (ERMs). As amostragens foram realizadas da superfície até a zona mesofótica (0 a 90 m de profundidade), utilizando SCUBA e Veículos Submersíveis de Operação Remota (VSORs). Esta tese é composta por quatro capítulos. No Capítulo 1 foi realizado uma avaliação quantitativa das comunidades de peixes, as quais formaram três comunidades distintas associadas aos diferentes estratos de profundidade e ao uso de diferentes hábitats de acordo com mudanças ontogenéticas (tamanho do corpo). Corais-negros e profundidade foram os fatores mais importantes na estruturação das comunidades de peixes, com uso intenso dos corais-negros por peixes na zona mesofótica. O Capítulo 2 apresenta a primeira avaliação qualitativa das comunidades bentônicas do ASPSP, além de uma avaliação da influência de variáveis bióticas e abióticas na estruturação das comunidades. Foram registrados 77 táxons bentônicos pertencentes a seis grupos. Macroalgas foi o grupo mais rico (41 táxons), com 17 novos registros para o ASPSP. Algas formadoras de tufos (turf) constituíram o grupo mais abundante em ambos os ambientes, eufótico e mesofótico. Foram observadas duas comunidades distintas: uma superficial composta principalmente pelo zoantídeo Palythoa caribaeorum, a pela alga Caulerpa racemosa carnuda, algas calcárias incrustantes (CCA) e Bryopsis spp, e outra mais profunda dominada por CCA, briozoários e corais escleractíneos. As variáveis abióticas, particularmente profundidade e luz, foram mais importantes na estrutura da comunidade bentônica. O Capítulo 3 traz informações sobre a abundância, distribuição, tamanho e vitalidade de corais-negros. Duas espécies de corais-negros, Tanacetipathes hirta (Gray, 1857) e T. thamnea (Warner, 1981), foram identificadas. Epibiose por zoantídeos e estrangulamento por monofilamentos afetaram negativamente as colônias de coral negro, uma delas monitorada durante dez anos. Esta última apresentou uma diminuição da vitalidade devido principalmente à presença de algas e estrangulamento por monofilamento. Corais-negros formam um grupo-chave na zona mesofótica do ASPSP, sendo intensamente utilizados como hábitat por diversos peixes recifais, principalmente espécies endêmicas (e.g., o peixe-borboleta Prognathodes obliquus). O Capítulo 4 aborda a ecologia do principal predador de invertebrados bentônicos na zona mesofótica do ASPSP, o verme-de-fogo Hermodice carunculata, descrevendo sua abundância e distribuição batimétrica e discutindo seu potencial em impactar as comunidades bentônicas, especialmente os corais escleractínios e os corais-negros na zona mesofótica do ASPSP. Observou-se um total de 278 indivíduos, com diferença significativa na abundância entre as zonas eufótica e mesofótica. Foi encontrada uma associação direta entre H. carunculata e 1) corais-negros (Tanacetipathes spp), 2) o coral escleractíneo Madracis decactis e 3) profundidade. Sugere-se aqui que os ecossistemas mesofóticos são essenciais para a estabilidade para as comunidades recifais eufóticas do ASPSP, tornando urgente a necessidade de novos estudos, principalmente com foco no potencial impacto da pesca e mudanças climáticas.

Wave and tides are important drivers of circulation, sediment transport and water exchanges between ocean and lagoon in atolls, which in turn, affect the formation and stability of reef islands. Through a combination of field measurements and numerical modelling, this thesis examines the wave- and tidally-induced processes at Rocas Atoll and their implications on sediment dynamics. This comprehends the morphological responses of reef islands, including the effects of sea level rise. Wave, current, tide and topo-bathymetric data were collected during three expeditions to Rocas Atoll, totaling 75 days of in situ measurements. A spectral wave model has been implemented and validated for the Rocas Atoll. Our results demonstrated that the mechanism of circulation and the wave propagation that affects the reef islands morphology are controlled by the interaction of wave climate with the atoll topography. Being under mesotidal setting, there is a strongly tide modulated process in Rocas. The offshore wave climate is dominated by southeast trade wind wave and swell from south and north mid-latitude hemispheres. The swell occurrence has a marked seasonality whereas the southeast wind waves persist during the whole year. Offshore waves are filtered by the reef rim resulting in a more homogenous lagoon wave climate, which is controlled by tide and reef topography. Offshore extreme events are promoted by energetic swells, either from north or south hemispheres. However, extreme events in the lagoon only occur when such offshore events are combined with spring high tide. Wind waves that persistently break on the windward side of the atoll plays an important role on the overall circulation. They pump water into lagoon creating wave- generated currents that flow from the windward to the leeward side of the atoll. A water level threshold exists due to the large tidal oscillation, blocking inflow by wave pumping at lower water levels. This results in periodic variations in the relative importance of tidal controls in lagoon circulation along a tidal cycle interval. Such mechanism described for Rocas Atoll can be extended to other similar mesotidal atolls. The reef islands are located on the leeward of the atoll and present higher morphological changes in response to northern swell. However, no significant net erosion was observed on daily and seasonal time scale, with eroded parts being compensated by accretion on adjacent parts. Conversely, Farol Island had a substantial accretion on a decadal time scale changing from an elongated ridge morphology to horse-shoe shape with three ridges and an intertidal central depression. The changes in the planform configuration were characterized by ocean shoreline erosion and lagoon shoreline progradation, representing net lagoonward migration. Cemitério Island remains stable for the same period, anchored by exposed consolidated sediments on both shores. Results indicate the resilient nature of reef islands and their potential adjustment to changes in boundary conditions. In terms of wave refraction, Rocas Atoll works as a platform reef due to its morphology. Wave vectors converge mainly on the leeward side and an interference zone can be observed from the windward side trough the lagoon. Such refraction pattern controls the location of reef islands and shingle bank on Rocas. Sea level rise displaces the wave convergence zone according to the incident wave incidence climate (swell or wind wave). This indicates that under sea level rise scenarios areas prone to sediment accumulation may become less stable, although not implying in the erosion of reef islands. The results provided an unprecedented dataset for Rocas Atoll, which improves the understanding about the mechanisms that control its reef islands morphodynamics and their ability adapt to changes in boundary conditions. / Os processos induzidos por ondas e marés em atóis são importantes forçantes da circulação, transporte de sedimentos e troca de água entre a laguna e oceano, que por sua vez, afetam a formação e estabilidade das suas ilhas recifais. Através da combinação de modelos numéricos e experimentos de campo, este trabalho teve por objetivo o estudo dos processos induzidos por ondas e marés no Atol das Rocas e suas implicações na dinâmica de sedimentos das ilhas recifais, considerando os efeitos do aumento do nível do mar. Experimentos de campo forneceram séries temporais de ondas, correntes, mares e informações topo-batimétricas ao longo de três expedições ao Atol das Rocas, totalizando 75 dias de levantamentos. Um modelo numérico de propagação de onda foi implementado e validado para a região. Os resultados demonstram que o mecanismo de circulação e de propagação de ondas, que afetam as ilhas recifais, é controlado pela interação do clima de onda com a topografia do atol, sendo fortemente modulados pelas flutuações de meso-maré. O clima de ondas ao largo do atol é dominado por vagas formadas pelos ventos alísios de sudeste e por ondulações geradas em latitude médias de ambos os hemisférios. A incidência das ondulações no atol apresenta uma forte sazonalidade enquanto que a vagas de sudeste persistem ao longo do ano. As ondas ao largo são filtradas pela borda do atol, resultando em um clima de ondas na laguna mais homogêneo e controlado pela maré e topografia do atol. Eventos extremos ao largo são ocasionados por ondulações energéticas tanto do hemisfério sul quanto do hemisfério norte. No entanto, os eventos extremos na laguna só ocorrem quando os eventos energéticos ao largo ocorrem em conjunto com maré alta de sizígia. As vagas que quebram constantemente no lado do atol exposto ao vento são importante forçantes na circulação geral do atol. A partir do processo de quebra, elas são responsáveis por bombear água para a laguna, criando intensas correntes geradas por ondas que fluem do lado exposto para o lado protegido. Este processo, modulado pela maré, resulta em variações periódicas da importância relativa da maré no controle da circulação. Foi também observada a presença de ondas longas dentro da laguna (infragravitacionais) provocada pela quebra do espectro de ondas incidente no recife. Através desses dados, o volume de fluxo de troca de água e o coeficiente de atrito no Barretão foram estimados. O mecanismo descrito para Rocas pode ser aplicado em outros atóis semelhantes sob regime de mesomaré, os quais ainda hoje têm sido pouco estudados. As ilhas recifais estão localizadas no lado protegido do atol e apresentam maiores modificações morfológicas em resposta a incidência de ondulações de norte. No entanto, não foi observado um balanço sedimentar negativo em escala diária e sazonal, com partes erodidas da ilha sendo compensadas por acresção nas partes adjacentes. Em escala decadal, a Ilha do Farol apresentou substancial acréscimo em área (59.6% em 75 anos), modificando sua forma alongada para uma forma de ferradura com formação de uma depressão central. Durante esse processo, o lado da ilha voltado para o oceano foi erodido, enquanto que o lado da laguna foi acrescido, caracterizando uma migração da ilha para a laguna. Não foram observadas modificações significativas na ilha do Cemitério, a qual está estabilizada atualmente pela presença de sedimentos consolidados expostos nos dois lados da ilha. Os resultados indicam que as ilhas são feições resilientes, capazes de se ajustar as mudanças nas condições de contornos. No processo de refração das ondas, devido a sua morfologia, o Atol das Rocas funciona com uma plataforma recifal. Os vetores de ondas convergem no lado protegido e zonas de interferência podem ser observadas no lado exposto e na parte central da laguna. A localização das ilhas e do banco Zulu está relacionada com o padrão de refração, que promovem locais favoráveis à deposição de sedimentos no atol. O aumento do nível do mar promove um deslocamento na posição de convergência das ondas de acordo com o tipo de onda incidente. Isto indica que neste cenário futuro, as áreas deposicionais podem se tornar mais instáveis no atol promovendo o deslocamento das ilhas, mas não necessariamente em uma erosão generalizada. Os resultados obtidos no desenvolvimento deste trabalho forneceram uma série de informações inéditas para o Atol das Rocas permitindo elucidar questões importantes acerca da capacidade de modificações das ilhas recifais em resposta aos processos oceanográficos dominantes no atol.