Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / Hard benthic reefs are increasingly known as highly diverse biodiversity ecosystems where sponges constitute a significant proportion of inhabitants. Nearly 60% of the seabed over the inner and outer shelf on the Agulhas Bank comprises hard substrata, and in combination with the convergence of the cold Benguela and the warm Agulhas Currents serves to create a nutrient rich zone supporting multiple fish nurseries. Here we provide the first information on hard benthic reef habitats on the subphotic zone of the Agulhas Bank complex marine protected area, which include Alphard Banks, 72 Mile Reef and 45 Mile Reef, as well as the shallow reefs which include 12 Mile Reef, 6 Mile Reef, 7 Mile Reef, Marthas Reef and inshore reefs within the Tsitsikamma marine protected area. The aim is to provide baseline data on the sponge fauna by identifying species and describing the biodiversity of these hard reefs between the depths 10–200 m on the south coast of South Africa. / 2024

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Understanding how coral reefs have developed in the past is crucial for placing contemporary ecological and environmental change within appropriate reef-building timescales (i.e. centennial to millennial). On Australia’s Great Barrier Reef (GBR), coral reefs situated within nearshore settings on the inner continental shelf are a particular priority. This is due to their close proximity to river point sources, and therefore susceptibility to reduced water quality as the result of extensive modification of adjacent river catchments following European settlement in the region (ca. 1850 CE). However, the extent of water quality decline and its impact on the coral reefs of the GBR’s inner-shelf remains contentious and is confounded by a paucity of long-term (> decadal) datasets. Central to the on-going debate is uncertainty related to the impact of increased sediment loads, relative to the natural movement and resuspension of terrigenous sediments, which have accumulated on the inner-shelf over the last ~6,000 years. The main aim of this thesis was to characterise and investigate the vertical development of turbid nearshore coral reefs on the central GBR. This aim was achieved through the recovery of 21 reef cores (3 - 5 m in length) from five proximal turbid nearshore reefs, currently distributed across the spectrum of reef ‘geomorphological development’ within the Paluma Shoals reef complex (PSRC). The recovered reef cores were used to establish detailed depositional and palaeoecological records for the investigation of the (1) internal development and vertical accretionary history of the PSRC; and (2) compositional variation in turbid nearshore coral and benthic foraminiferal assemblages during vertical reef accretion towards sea level. Established chronostratigraphic and palaeoecological records were further used to assess the impact of post-European settlement associated water quality change in a turbid nearshore reef setting on the central GBR. Radiocarbon dating (n = 96 dates) revealed reef initiation within the PSRC to have occurred between ~2,000 and 1,000 calibrated years before present, with subsequent reef development occurring under the persistent influence of fine-grained (< 0.063 mm) terrigenous sediments. The internal development of the PSRC was characterised by discrete reef facies comprised of a loose coral framework with an unconsolidated siliciclastic-carbonate sediment matrix. A total of 29 genera of Scleractinian coral and 86 genera of benthic foraminifera were identified from the palaeoecological inventory of the PSRC. Both coral and benthic foraminiferal assemblages were characterised by distinct assemblages of taxa pre-adapted to sediment stress (i.e. low light availability and high sedimentation). At the genus level, no discernable evidence of compositional change in either coral or benthic foraminiferal assemblages was found, relative to European settlement. Instead, variations in assemblage composition were driven by intrinsic changes in prevailing abiotic conditions under vertical reef accretion towards sea level (e.g. hydrodynamic energy, light availability, and sedimentation rate). These findings therefore highlight the importance for considering reef ‘geomorphological development’ when interpreting contemporary reef ecological status. Furthermore, this research emphasises the robust nature of turbid nearshore reefs and suggests that they may be more resilient to changes in water quality than those associated with environmental settings where local background sedimentary conditions are less extreme (e.g. towards the inner/mid-shelf boundary). To this end, this thesis presents new baseline records with which to assess contemporary ecological and environmental change within turbid nearshore settings on the central GBR.

O presente estudo foi realizado no maior complexo recifal do Atlântico Sul, o Banco dos Abrolhos, e visou investigar a estrutura das comunidades de Tanaidacea, pequenos crustáceos da infauna comuns em substratos inconsolidado. Dois recifes foram analisados Sebastião Gomes (SG), localizado no arco costeiro, e Parcel dos Abrolhos (PA), localizado no arco externo. As coletas foram realizadas em julho de 2007 com a utilização de pegadores van Veen com área amostral 0,07m² em SG e 0,03m² no PA. O desenho amostral foi diferente nos dois recifes, em SG as amostras foram coletadas em 4 transectos (L, O, N e S) no entorno do recife, e no PA foram coletas no entorno e em um único transecto na direção da costa. Apesar do menor esforço amostral realizado no PA (0,81m²) comparado com SG (5,04m²), os tanaidáceos foram mais abundantes e mais diversificados no PA. Foram coletados 221 exemplares de 11 espécies em SG, e 417 indivíduos de 24 espécies no PA. O distanciamento recifal influenciou no perfil granulométrico das estações de SG, havendo diminuição do tamanho do grão, da contribuição carbonática e da heterogeneidade sedimentar. Estas características provavelmente estão ligadas à diminuição da riqueza e aumento da abundância, devido a ocorrência de uma espécie dominante. O transecto Sul de SG não apresentou nenhum Tanaidacea devido à ressuspensão sedimentar na base recifal causada, provavelmente, pela entrada de frentes frias na região. As características sedimentares no PA não variaram com o distanciamento recifal, sendo o sedimento muito heterogêneo e com altas taxas de carbonato biodetrítico em todas as estações. A comunidade de Tanaidacea do PA mostrou não estar relacionada aos fatores sedimentares analisados. / This study was conducted in the largest South Atlantic reef complex, the Abrolhos Bank, and aimed to investigate the Tanaidacea community structure, that are small infaunal crustaceans common in soft bottom. Two reefs were analyzed: Sebastião Gomes (SG), located in the inner arc of the reef complex, and Parcel dos Abrolhos (PA), located in the outer arc. In July 2007, samples were collected with van Veen grabs of 0.07 m² area in SG and 0.03 m² in PA. The samples were designed in four transects around SG, and a transect in PA. Despite lower sampling effort in PA (0.81 m²) than SG (5.04 m²), tanaids were more abundant and richer in PA. There were collected a total of 221 specimens belonging to 11 species in SG, and 417 individuals belonging to 24 species in PA. The distance from the reef influence the sediment granulometry around SG, decreasing grain size, rate of carbonates and sedimentary heterogeneity. The distance also decreased richness and increased the abundance of the dominant species. SG southern transect did not present tanaids probably due to sediment resuspension in the reef base caused by south cold fronts in winter. The PA sediment was unaffected by the distance from the reef and was very heterogeneous, with high rates of carbonates in all sample sites. The PA Tanaidacea community was not related to the sedimentary characteristics analyzed.

O presente estudo foi realizado no maior complexo recifal do Atlântico Sul, o Banco dos Abrolhos, e visou investigar a estrutura das comunidades de Tanaidacea, pequenos crustáceos da infauna comuns em substratos inconsolidado. Dois recifes foram analisados Sebastião Gomes (SG), localizado no arco costeiro, e Parcel dos Abrolhos (PA), localizado no arco externo. As coletas foram realizadas em julho de 2007 com a utilização de pegadores van Veen com área amostral 0,07m² em SG e 0,03m² no PA. O desenho amostral foi diferente nos dois recifes, em SG as amostras foram coletadas em 4 transectos (L, O, N e S) no entorno do recife, e no PA foram coletas no entorno e em um único transecto na direção da costa. Apesar do menor esforço amostral realizado no PA (0,81m²) comparado com SG (5,04m²), os tanaidáceos foram mais abundantes e mais diversificados no PA. Foram coletados 221 exemplares de 11 espécies em SG, e 417 indivíduos de 24 espécies no PA. O distanciamento recifal influenciou no perfil granulométrico das estações de SG, havendo diminuição do tamanho do grão, da contribuição carbonática e da heterogeneidade sedimentar. Estas características provavelmente estão ligadas à diminuição da riqueza e aumento da abundância, devido a ocorrência de uma espécie dominante. O transecto Sul de SG não apresentou nenhum Tanaidacea devido à ressuspensão sedimentar na base recifal causada, provavelmente, pela entrada de frentes frias na região. As características sedimentares no PA não variaram com o distanciamento recifal, sendo o sedimento muito heterogêneo e com altas taxas de carbonato biodetrítico em todas as estações. A comunidade de Tanaidacea do PA mostrou não estar relacionada aos fatores sedimentares analisados. / This study was conducted in the largest South Atlantic reef complex, the Abrolhos Bank, and aimed to investigate the Tanaidacea community structure, that are small infaunal crustaceans common in soft bottom. Two reefs were analyzed: Sebastião Gomes (SG), located in the inner arc of the reef complex, and Parcel dos Abrolhos (PA), located in the outer arc. In July 2007, samples were collected with van Veen grabs of 0.07 m² area in SG and 0.03 m² in PA. The samples were designed in four transects around SG, and a transect in PA. Despite lower sampling effort in PA (0.81 m²) than SG (5.04 m²), tanaids were more abundant and richer in PA. There were collected a total of 221 specimens belonging to 11 species in SG, and 417 individuals belonging to 24 species in PA. The distance from the reef influence the sediment granulometry around SG, decreasing grain size, rate of carbonates and sedimentary heterogeneity. The distance also decreased richness and increased the abundance of the dominant species. SG southern transect did not present tanaids probably due to sediment resuspension in the reef base caused by south cold fronts in winter. The PA sediment was unaffected by the distance from the reef and was very heterogeneous, with high rates of carbonates in all sample sites. The PA Tanaidacea community was not related to the sedimentary characteristics analyzed.

El análisis de estructuras paleokársticas ha atraído, en los últimos años, el interés de numerosos investigadores a la información que aportan a la geología aplicada y la paleogeomorfología. Estudios recientes se han centrado en la aplicación de técnicas de exploración del subsuelo debido a la escasez de afloramientos. En la presente Memoria se analizan íntegramente las formas de hundimiento pretéritas que afloran discontinuamente con gran detalle, en los acantilados de las costas meridional (plataforma de Llucmajor) y oriental (plataforma de Santanyí) de Mallorca, a lo largo de más de 75 km de línea de costa, afectando a las rocas carbonáticas del Mioceno superior. El estudio se ha centrado en la distribución geográfica, evolución geológica y las características geomorfológicas de estos paleocolapsos, con especial énfasis en su génesis, su relación con la arquitectura y distribución de las facies, así como en las formas y productos asociados.Los paleocolapsos han sido descritos en su contexto litoestratigráfico y estructural dentro de las mencionadas plataformas carbonáticas, siendo este trabajo una contribución al conocimiento del karst en estas unidades geológicas y su relación con las fluctuaciones marinas. La karstogénesis queda reflejada en estas formas pretéritas donde se han observado depósitos y formas de disolución ligadas a la dinámica kárstica controlada, en el caso que nos ocupa, por las fluctuaciones del nivel del mar: brechas, sedimentos detríticos, cementos, así como distintos tipos y volúmenes de porosidad. La mayor parte de estas formas (sobre un total de 177), cuyas dimensiones en sección varían desde pocos metros hasta afloramientos con 28 m de altura y más de 100 m en la horizontal, se ubican en la plataforma de Santanyí a excepción de dos estructuras ubicadas en la plataforma de Llucmajor.El análisis geológico y su relación con los paleocolapsos muestra como en la plataforma de Llucmajor éstos afectan a las facies de la Unidad Complejo Arrecifal (facies de back reef y frente arrecifal). Sin embargo, en la plataforma de Santanyí, los paleocolapsos afectan tanto a parte del Complejo Arrecifal (facies de back reef), como a la totalidad de la Unidad Calizas de Santanyí. A partir del estudio de la arquitectura de facies del Complejo Arrecifal en la plataforma de Llucmajor se ha establecido el modelo deposicional en la plataforma de Santanyí. Sin embargo, ésta última se encuentra compartimentada como consecuencia del control de dos fallas en dirección de orientación E-O en S'Algar y Na Magrana, donde se localiza el contacto entre facies de lagoon externo y talud arrecifal. No obstante, la cartografía y análisis de los lineamientos en dicha plataforma ha permitido identificar dos familias principales con dos direcciones dominantes; NE-SO y NO-SE, siendo la dirección E-O menos representativa. Se han observado fracturas distensivas y pequeñas fallas inversas miocenas asociadas al proceso de colapso, así como fracturas y fallas postmiocenas, y fracturas cuaternarias.El estudio de la geometría en sección de los paleocolapsos pone de relieve que la formas en "V", "U" y conoidales son las más comunes. Han sido identificadas dos partes diferentes en un paleocolapso tipo: una inferior donde se observa la paleocavidad ubicada en la base del paleocolapso (lagoon externo y/o frente arrecifal), con una geometría irregular de dimensiones entre 1 m y 9 m rellena por sedimentos adyacentes y suprayacentes a ésta; y una parte superior, coincidente con los bordes de la estructura (lagoon interno/Calizas de Santanyí) buzando con inflexión conoidal hacia la paleocavidad.Se han identificado cuatro tipos de brechas (crackle, crackle-laminae-split, de mosaico y caótica) en las estructuras de paleocolapso asociadas cada una de ellas a distintos niveles estratigráficos y, en algunos paleocolapsos, con una gradación vertical y lateral. Son característicos de estos depósitos los sedimentos detríticos (matriz) y los cementos asociados (vadosos y freáticos). En general, el cemento domina sobre la matriz en la zona inferior del paleocolapso, mientras que por encima, es la matriz la que domina sobre el cemento. El análisis por difracción de Rayos X de la matriz indica para la muestra total que la calcita es el mineral principal y el cuarzo el mineral secundario. En la fracción arcilla, la moscovita, la illita y la caolinita son los minerales más comunes. De ello, junto con el estudio de láminas delgadas en estos depósitos, donde se han observado tamaños de grano en el cuarzo superior a 2 mm, se deduce un ambiente de sedimentación subsuperfical y otro subaéreo de lo que se extrae un origen, proceso de transporte y sedimentación diversos, así como la evolución cristaloquímica en determinados minerales. Los cementos son de naturaleza calcítica, con contenidos relativamente altos en magnesio para los freáticos y bajos para los vadosos. Para el estudio de la porosidad en los paleocolapsos se ha procedido a su clasificación en dos tipos principales, interclasto e intraclasto, a partir de las cuales se ha estudiado la macro y microporosidad. La brecha caótica de colapso es la que presenta volúmenes de porosidad más elevados y tipologías diversas. El análisis de isótopos estables muestra una gran homogeneidad entre la composición isotópica de los cementos, con valores en &#948;18O y &#948;13C ligeros, lo que indica condiciones análogas de precipitación, con dominio de aguas dulces sobre las saladas. Tanto la marca del oxígeno como del carbono parecen indicar que los cementos se depositaron en un período interglaciar coincidente con algún estadio isotópico impar.El estudio de la arquitectura de facies de la plataforma de Llucmajor ha permitido elaborar un modelo genético de ocurrencia para los paleocolapsos y su ubicación espacio-temporal. Dicho modelo, ha sido corroborado por la relación entre la distribución de facies y paleocolapsos en la plataforma de Santanyí, por la observación en algunos paleocolapsos de sedimentos a techo de la Unidad Calizas de Santanyí que sellan la estructura, así como por el tipo de brechas características de colapsos sinsedimentarios (brecha crackle-laminae-split), que muestran una deformación dúctil de los materiales cuando éstos no estaban completamente consolidados, dando lugar a formas laxas de bajo ángulo. Los procesos genéticos que dieron lugar a los paleocolapsos kársticos están directamente relacionados con la alta frecuencia de fluctuación del nivel del mar durante el Mioceno superior, la misma que controló la arquitectura de facies y la posición del nivel freático. Las oscilaciones del nivel freático causaron la alternancia de dominios freáticos y vadosos así como, de agua dulce y agua salada en la interfase, provocando la disolución de los parches coralinos y el posterior hundimiento del techo de las cavidades. El estudio integral de todos estos aspectos junto con el análisis de una red de paleocauces y una playa fósil, ha permitido realizar una reconstrucción paleogeográfica desde el Messiniense en la plataforma de Santanyí e identificar estructuras de paleocolapso postmiocenas y cuaternarias. Con estos datos se ha procedido a la comparación de los paleocolapsos kársticos con otras estructuras similares en el País Vasco y Las Islas de Malta, de lo que se extraen analogías y diferencias, determinadas fundamentalmente por el orden de fluctuación del nivel del mar. Por último, se discute el papel de los paleocolapsos kársticos como elementos que contribuyen en cierta medida a la ocurrencia de hidrocarburos en plataformas carbonáticas, pudiendo ser excelentes reservorios debido al gran número de afloramientos, el volumen de roca afectada y a su elevada porosidad y permeabilidad. / Paleokarst tend to differ from studies of recent and modern karst landforms though is important the genetic understanding of the karst processes for analysis a paleokarst structure. Paleokarst systems form an important class of carbonate record and they have a pronounced lateral and vertical spatial complexity that results from a complex history of formation. Most of the known karst systems are epigenetic and they are the result of near-surface karst processes during periods of subaerial exposure and latter burial compaction and diagénesis. Scale, porosity types and spatial complexities of these paleokarst systems depends on the carbonate rock solubility, paleoclimatic conditions, lowering of base level either by tectonic uplift or sea-level fall and time of subaerial exposure. Uplift, in addition, commonly induces fracturing and faulting that further control karst development. Ascertaining and predicting paleokarstic heterogeneities within carbonate rocks are strategic to fluids field development and optimum production. With current subsurface methods, however, most of the smaller-scale stratigraphic architecture and diagenetic facies are difficult to define. Predictive models for exploration and development are best made from outcrop studies of well-exposed examples. Accuracy for prediction of these models depends on the detailed understanding of the genetic factors controlling their geometries, scale, pore networks and spatial complexities of these potential karstic store. Miocene carbonates (Upper Tortonian-Lower Messinian) in Mallorca Island are composed of reefal (Reef Complex) and shallow water carbonates (Santanyí Limestone) that prograded across platforms surrounding paleoislands. The contact between the Reef Complex and the Santanyí Limestone is a subaerial erosion surface with paleokarst features. The shallow-water carbonates beds both the lagoonal beds of the Reef Complex and basal beds of the Santanyí Limestone, are affected by paleocollapse structures produced by roof collapse of caverns developed in the underlying Reefal Complex. These paleocollapse structures affecting to the carbonate platform allows to propose a genetic model to explain the origin of these paleosink, that are related to early diagenetic processes induced by high-frequency sea-level fluctuations, the same sea-level fluctuations that controlled the facies architecture of the carbonate platforms.Cartography and study of lineaments and fractures on Santanyí Platform have permitted identified two principals groups with two main directions: NE-SO and NO-SE. Have been observed distensiva fractures and Miocene small inverse faults related with de breackdwon phenomena. Moreover, postmiocenes and quaternary faults and fractures have been recognized.The geometry of paleocollapse structures is commonly (in section) as "V", "U" or funnel. The size is variable from few meters of long to thousands meters, and few meters of weigh to thirteen meters. Breccias has been classified as crackle, crackle-laminae-split, mosaic and chaotic types. Chaotic breccias grade from matrix-free, clasts-supported breccias to matrix-supported breccias. The matrix mineralogy is compose in the total sample for calcite in the major part and quartz in less quantity. However, same structures present quartz as principal mineral. To the clay fraction, caolinite, illite and moscovite are the most general mineral present.The geochimical sediment (carbonate) are filling a part of interclaste breccias porosity. This is commonly phreatic speleothems. Isotopic studies of this sediments show &#948;18O and &#948;13C contents negatives. This fact could indicate a fresh water environment deposition