Submitted by Carlos Augusto Rolim da Silva Junior (carlos_jrolim@hotmail.com) on 2016-02-17T17:17:41Z No. of bitstreams: 1 arquivototal.pdf: 2218956 bytes, checksum: a548059b9522dd6db92240b0b0c48fee (MD5) / Made available in DSpace on 2016-02-17T17:17:41Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2218956 bytes, checksum: a548059b9522dd6db92240b0b0c48fee (MD5) Previous issue date: 2013-05-08 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Coral reefs are recognized as the largest biological structures in the oceans. They formed by building organisms (e.g. scleractinian corals and calcareous algae). In the last five decades, there have been declines in coral cover worldwide. Overfishing, pollution and increased coastal sedimentation are pointed as the main impacts responsible for declines in abundance of reef-building organisms and increases in abundance of non-building ones (e.g. algae), a process known as "phase shift". The zoanthid Palythoa caribaeorum is abundant in the Atlantic, particularly in Brazil. It is able to tolerate high environmental variability and displays the highest growth rate among all Anthozoans. Moreover, it has elaborated strategies of competition for space, which makes it competitively superior to most other benthic invertebrates. The present work was performed in the Abrolhos Bank, Bahia, with the following main objectives: 1) to describe the spatio-temporal patterns in cover of P. caribaeorum across the Abrolhos Bank, 2) evaluate the relative influence of distance offshore, depth, latitude and biomass of fish zoanthid predators in the abundance of P. caribaeorum; 3) describe the benthic succession in two areas in which P. caribaeorum was excluded (one next to the coast and subject to high sedimentation levels and another far from the coast and subject to low sedimentation). The study of spatio-temporal patterns was conducted in six reefs from 2006 to 2008: Parcel dos Abrolhos (five sites), Archipelago (five sites), Timbebas (three sites), Itacolomis (eight sites), Parcel das Paredes (two sites) and Sebastião Gomes (one site). The exclusion experiment was conducted from 2006 to 2009 in the top of the reefs of sites Arenguera (Parcel das Paredes) and PAB4 (Parcel dos Abrolhos). Four 5 x 5 m areas were selected at each site. Two of them were manipulataded (all P. caribaeorum removed) and the other two were not manipulated (control). Three treatments were applied within each area: 1) closed cage, to exclude reef fish known to predate P. caribaeorum, 2) open cage (control for the effect of the cage), 3) without cage. The methods used were photo-quadrats (benthic assessments) and stationary visual census (fish assessments). The results showed that P. caribaeorum dominates the top of the reefs, with insignificant coverage in the wall. This suggests the preference of P. caribaeorum for horizontal inclination and high light levels. The relative cover of P. caribaeorum was higher in the sites PAB4, PAB5, TIM2, TIM3, ARENG and SG, and was positively influenced by depth and negatively influenced by distance offshore. The five most abundant reef fish species recognized as predatos of zoanthids in terms of biomass were A. saxatilis, P. paru, P. arcuatus, H. ciliares, and C. striatus. In the exclusion experiment, a slow recovery of P. caribaeorum was recorded in the manipulated areas, with no differences in recolonization rates between the two sites (near or away from the coast). Settlement of P.caribaeorum at the manipulated areas may have been inhibited by the proliferation iof fast growing epilithic algae, particularly inside closed cages. The overall average growth rate was higher in ARENG (0.23 cm-2.day-1) than in PAB4 (0.12 cm-2.day-1) in the manipulated area. However, in the control area of PAB4 P. caribaeorum showed a growth rate of 3.18 cm-2.day-1, while in the control area of ARENG it declined (-0.25 cm-2.day-1). Total coverage of P. caribaeorum declined in the control area of ARENG due to a bleaching event that occurred throughout the study. Conclude that: 1) environmental variables such as depth and distance from the coast, are more important than biotic (eg predation) in the dynamics of P. caribaeorum, 2) despite the coverage of P. caribaeorum present negative relationship with distance from the coast, recolonization rates were not higher at the site closest to shore, 3) coverage of P. caribaeorum increases in periods near the summer at both sites, and 3) low density of Palythoa was unfavorable for a faster process of recolonization. / Os recifes de corais são as maiores estruturas biológicas dos oceanos, formados, principalmente, por organismos construtores (ex. corais escleractíneos e algas calcárias). Nas ultimas cinco décadas, foram registrados declínios acentuados na cobertura de corais em todo o mundo. Sobrepesca, poluição e aumento da sedimentação costeira são apontados como os principais impactos responsáveis por esses declínios e pelo aumento na abundância de organismos não construtores (e.g. algas e zoantideos), processo conhecido como “mudança de fase”. O zoantídeo Palythoa caribaeorum é abundante no Atlântico Sul, particularmente no Brasil. Ele é capaz de tolerar alta variabilidade ambiental e apresenta a maior taxa de crescimento entre os antozoários, além de estratégias elaboradas de competição por espaço, as quais garantem sua superioridade competitiva sobre a maioria de outros invertebrados bentônicos recifais. O presente trabalho foi realizado no Banco dos Abrolhos, BA, e tem como objetivos principais: 1) descrever os padrões espaço-temporais de cobertura de P. caribaeorum ao longo do Banco dos Abrolhos, 2) avaliar a influência da distância da costa, profundidade, latitude e biomassa de peixes predadores de zoantídeo na abundância de P. caribaeorum, 3) descrever a sucessão bentônica em áreas nas quais P. caribaeorum foi retirada. O estudo dos padrões espaço-temporais foi conduzido em seis recifes de 2006 a 2008: Parcel dos Abrolhos (cinco sítios), Arquipélago (cinco sítios), Timbebas (três sítios), Itacolomis (oito sítios), Parcel das Paredes (dois sítios) e Sebastião Gomes (um sítio). O experimento de exclusão foi realizado de 2006 a 2009 no topo dos sítios Arenguera (Parcel das Paredes) e PAB4 (Parcel dos Abrolhos). Em cada sitio foram selecionadas quatro áreas de 5 x 5 m, sendo duas manipuladas (cobertura de P. caribaeorum retirada). Três tratamentos foram aplicados dentro de cada área: gaiola fechada, gaiola aberta e sem gaiola. Os métodos utilizados foram foto-quadrado (caracterização do bentos) e censo visual estacionário (quantificação de peixes). Os resultados mostraram que P. caribaeorum domina no topo dos recifes, com coberturas insignificantes na parede, demonstrando a preferência de P. caribaeorum por ambientes mais iluminados e horizontais. A cobertura relativa de P. caribaeorum foi maior nos sítios PAB4, PAB5, TIM2, TIM3, ARENG e SG, tendo sido influenciada positivamente pela profundidade e negativamente pela distância da costa. A biomassa de predadores variou entre os sítios mas não influenciou significativamente na distribuição da P. caribaeorum. As cinco espécies de predadores de P. caribaeorum mais abundantes em termos de biomassa foram Abudefduf saxatilis, Pomacanthus paru, Pomacanthus arcuatus, Holacanthus ciliares e Chaetodon striatus. No experimento de exclusão foi registrada recuperação lenta de P. caribaeorum na área manipulada, não sendo registrada diferença nos padrões de recolonização entre os dois sítios (próximo e afastado da costa). Um dos fatores que pode ter inibido o assentamento da P. caribaeorum na área manipulada foi a proliferação de algas epilíticas, principalmente dentro das gaiolas fechadas, fato conhecido como uma das primeiras fases de degradação nos ambientes recifais. A taxa de recolonização (i.e. assentamento seguido de crescimento) foi maior em ARENG (0,23 cm-2.dia-1) do que em PAB4 (0,12 cm-2.dia-1) na área manipulada. Entretanto, na área controle, PAB4 apresentou taxa de recuperação de 3,18 cm-2.dia-1 enquanto que em ARENG a área de P. caribaeorum declinou (-0,25 cm2.dia-1). Pode-se concluir: 1) variáveis ambientais, como profundidade e distância da costa, são mais importantes do que variáveis bióticas (i.e predação) na dinâmica de P. caribaeorum, 2) apesar da cobertura de P. caribaeorum apresentar relação negativa com a distância da costa, as taxas de recolonização não foram maiores no sítio mais próximo a costa, 3) a cobertura de P. caribaeorum aumenta em períodos próximos ao verão, em ambos os sítios e 3) a baixa densidade de Palythoa foi desfavorável para um processo mais rápido de recolonização.

Coral reefs ecosystems are deteriorating and facing dramatic changes. These changes suggest a shift in dominance from corals to other benthic organisms. Particularly in the Caribbean Sea, with corals dying, sponges have become the leading habitat-forming benthic animals. However, little is known about what life-history traits allow organisms to proliferate in a marine system that is undergoing change. Thus, the objective of this dissertation was to try to understand the current increase of encrusting excavating sponges on deteriorating Caribbean coral reefs through the study of reproduction, recruitment and dispersal potential of the widely distributed and currently expanding species, Cliona delitrix. Different methodological approaches were used, such as histology, electron microscopy, quantification of sponges in the field, genetics, and mathematical modeling. Results are presented in four different chapters. It was found that Cliona delitrix has an extended reproductive cycle in Florida, USA, from April - May to around November - December depending on a >25°C sea-water temperature threshold. C. delitrix gametogenesis is asynchronous and it has multiple spawning events. C. delitrix is recruiting abundantly on Caribbean coral reefs, preferentially on recent coral mortality than on old coral mortality. The increase in C. delitrix and other excavating sponges can be explained by the repeated spawning and by the coincidence in time and space of larval production with the availability of new dead coral, which tend to overlap during the warmest months of the year. Eggs or larvae of C. delitrix appear to survive enough to be transported by currents over larger distances. It was found that dispersal ranges for Cliona delitrix may reach as far as ~315 km in the Florida reef track, and over ~971 km in the South Caribbean Sea, between Belize and Panama. Thus, reproduction, dispersal, and recruitment patterns of C. delitrix along with oceanographic currents, and eddies that form at different periods of time, are sustaining the spread of this sponge on coral reefs. According to mathematical models carried out, C. delitrix increase on reefs fluctuates depending of coral mortality events and available space on old dead coral (colonized by algae and other invertebrates). However, under temperature anomalies, these sponges will 2 tend to increase and take over the reef system only if heat stress and coral mortality is moderate. Under massive mortality events both corals and sponges will tend to decline, although sponges at a slower rate than corals. In general, coral excavating sponges have been favored by coral mortality, especially during past few decades. However as bioeroders, their success is also limited by the success of calcifying corals. In a reef management context and based on this dissertation’s findings, it is suggested that excavating sponges, and especially Cliona delitrix, should be more formally included in reef monitoring programs. Their increase can be used to track coral mortality events on reefs (past and future), and also can be used as another major bioindicator of health on coral reefs.

Mesobenthic amphipods (2-15 mm) constitute an important faunal component of coastal ecosystems, and often represent a major trophic link between primary producers and fishes. However, obtaining basic demographic data on these taxa is often hindered by a lack of suitable non-destructive, quantitative, collection techniques. Although artificial substrates have been advocated for collecting data at these lower trophic levels, recent studies suggest that they may not accurately represent the natural benthic assemblage. This study evaluated how a structurally-complex artificial substrate (3-dimensional) simulated the natural substrate of a shallow Acropora reef environment. Assemblage development was followed on a series of artificial substrate units (ASUs) at 2-week intervals over a 14-week period; adjacent natural substrate was sampled monthly. Multivariate analyses were applied to determine the (dis)similarity of assemblages between the two substrate types. Statistical analyses showed significant differences in assemblage structure between artificial and natural substrates. However, no significant differences were found between sites or habitats within substrate type. Samples from the ASUs were dominated by Elasmopus balkomanus, Bemlos kunkelae, Neomegamphopus kalanii, and Ericthonius punctatus. Taxa abundant on the natural substrate, but numerically poor on the ASUs, included Chevalia carpenteri, Apolochus sp., Gammaropsis atlantica, and Globosolembos smithi. Assemblage dissimilarities depended chiefly on differences in species composition and relative abundance largely contributed to the dissimilarity between the two substrates.

La dissolution biogénique réalisée par les microperforants constitue une des principales forces de destruction des récifs coralliens. Ce processus, stimulé par certains facteurs du changement global comme l'acidification, est encore peu connu et donc mal intégré dans les modèles de prédiction du devenir des récifs. Pour mieux comprendre ce processus et sa dynamique temporelle, des blocs de squelette corallien ont été exposés, sur un récif en Nouvelle-Calédonie, aux microperforants entre 1 et 12 mois et au cours de six séries temporelles; trois commençant en été et trois en hiver. Ainsi, les taux de dissolution biogénique ainsi que la diversité et l'abondance des microperforants ont été déterminés. En parallèle, un suivi de paramètres externes, abiotiques et biotiques, a été réalisé. Cette étude a mis en avant i/ trois étapes dans le processus de dissolution biogénique, décrites par un modèle logistique de croissance, contrôlées par les espèces microperforantes et par l'intensité du broutage ; ii/ les interactions entre les paramètres externes et la dynamique des successions de communautés microperforantes décrites dans un modèle conceptuel ; iii/ l'influence de paramètres externes sur la dynamique temporelle de la dissolution biogénique. Ainsi, Ostreobium quekettii, l'agent le plus actif dans la dissolution biogénique, est recruté plus rapidement et la dissolution biogénique augmente lorsque les squelettes sont exposés à des températures plus élevées ou soumis à une augmentation des nutriments. Ces résultats suggéreraient, dans le contexte du changement global, une accélération de la dissolution biogénique fragilisant d'autant plus les récifs coralliens. / Biogenic dissolution of carbonates due to microborers is one of the main destructive forces in coral reefs. Unfortunately this biogeochemical process received low attention and thus is considered as negligible by prediction models of coral reefs future while this process seems to be stimulated by global change factors such as acidification. In this context, dead coral skeletons were exposed, on a reef in New Caledonia, to microborers for six temporal series from 1 to 12 months of exposure (three started in summer and three in winter). Study of coral blocks allowed to determine together biogenic dissolution rates, the diversity and the abundance of microborers. In parallel, external biotic and abiotic parameters were recorded monthly and/or continuously. This experiment highlighted for the first time; I/ three steps in the temporal dynamics of the biogenic dissolution, described by a growth logistic models, driven by microborer communities and grazing intensity; II/ The interactions between microboring community successions and external parameters described by a conceptual model; III/ the influence of external parameters on the dynamic of biogenic dissolution. Thus, results showed an early installation of Ostreobium quekettii, the main agent of the biogenic dissolution and an increase of this process due to higher seawater temperature or nutrients. This suggests, in the context of global change, an acceleration of the biogenic dissolution weakening even more coral reef ecosystems.

Photo-oxidative stress is one of the key factors that can induce bleaching in reef organisms. With the decline of coral reefs and recurrent bleaching events, many studies have focused on understanding the mechanism behind this phenomenon. Two of the hypotheses that explain how the photosynthetic performance of the symbiont is affected and influences bleaching are: (1) disruption of the photosynthetic pathway by direct damage to the photosystem II (PSII), and (2) by inhibition of the Calvin-Benson cycle. In this dissertation I examine different aspects of photosynthetic performance in symbiont-bearing reef organisms and how this is influenced by symbiont loss and changes in photic stress as a result of different levels of irradiance modulated by time of the year (e.g., season) and depth; and take a closer look into primary productivity by symbionts with controlled laboratory experiments. Field experiments during 2012–2013 at Tennessee Reef, FL, assessed the photosynthetic performance of PSII in the diatom-bearing foraminifer, Amphistegina gibbosa, and the anthozoans: Palythoa cariabeorum, Siderastrea siderea, and Montastraea cavernosa. Data collected for the bleaching trends of A. gibbosa revealed that bleaching rates are higher in the summer months than in winter. Photochemical efficiencies of PSII in A. gibbosa, as measured with PAM fluorometry on the day of collection, were more variable in the shallow site (6 m) than in the deeper site (18 m). Also, photochemical efficiencies at the shallow site were lower during the summer months than during winter months. At the 18 m site, photochemical efficiencies did not exhibit a clear seasonal trend. Depth also had an effect on the measured photochemical efficiencies of the anthozoans. Photochemical efficiencies were lower and more variable in colonies at 6 m compared to colonies from 18 m. Although previous studies have reported seasonal effects on the photochemical efficiency of some coral colonies, that trend was not apparent in this study. Photoacclimation and productivity were assessed for A. gibbosa using rapid light curves (RLC) and photosynthesis vs. irradiance curves (P-E). Maximum relative electron transport rate (rETRmax) as described by RLCs was significantly different between A. gibbosa without visual signs of bleaching and those with severe bleaching. Individuals with partial bleaching had a rETRmax that was intermediate between the other two categories. The P-E curves showed a similar trend. In this case individuals that were non- or partly bleached had significantly higher photosynthesis maxima than those with severe bleaching. The onsets of photosynthesis and saturation irradiance were not significantly different among the categories of bleaching analyzed. Results from this dissertation suggest that A. gibbosa has the capability to detect and digest damaged symbionts, that the symbionts even in the deeper chambers react in a similar way to irradiance, but that in severe cases of bleaching the symbionts may not produce enough energy to sustain the requirements of the host, even in non-stressful conditions.

Worldwide, coral cover has declined at rates that have often exceeded 5% per year since the 1980’s. Populations of scleractinians (stony corals) in the Florida Keys reef tract have declined as well, with some communities declining at rates > 3% per year. Decreased water quality (e.g., steady increases in the ocean water temperatures and increased pollution, nutrients, or water turbidity due to coastal runoff) are commonly attributed to this decline. But actual linkages between variability and trends in these environmental parameters, and in stony coral diversity and ecosystem functions such as net community production, have not yet been well characterized. With this research, I examined the influence of water quality (water temperature, nutrients and turbidity) on stony coral diversity and net community productivity in shallow-water reef ecosystems of the Florida Keys between 1996 and 2010. Differences in stony coral diversity in Florida Keys patch reefs with respect to sea surface temperature (SST) variability are evaluated in Chapter Two. Habitat-specific differences in stony coral diversity with respect to changes in a suite of environmental parameters (water turbidity, nutrients, water temperature and depth) are addressed in Chapter Three. Differences in daytime net community production and light-adapted stony coral photosynthetic efficiencies among three reef sites with different turbidity levels and seasons (May and October) are presented in Chapter Four. Environmental parameters examined to characterize the differences in stony coral diversity across the Florida Reef Tract included satellite-derived sea surface temperature [SST] and Degree Heating Weeks [DHWs], field observations of bio-optical properties of the water, and nutrient concentrations. These parameters were compared with live coral cover and species richness, net community production, and coral photo-physiological observations. In Chapter Two, I found that stony coral cover and diversity was higher in patch reefs of the Florida Keys relative to offshore and deeper reefs. Generally, patch reefs were characterized by intermediate to high SST variability (≥7.0°C2). Intermediate SST variance (7.0–10.9°C2) was correlated with higher diversity indices for patch reefs of the Upper (Shannon Diversity: 1.2–1.5) and Middle Keys (Species Richness: 13–19), suggesting that stony coral species in these habitats are either adapted to intermediate temperature ranges or thermal acclimation has taken place for individual colonies. Additionally, I found that found that years for which cold and warm-water extremes coincided (i.e., highest SST variance), such as 1997-98 and 2009-2010, led to significant reductions in both H’ and SR. Coral bleaching and mortality were associated with exposure to cold- and warm-water temperature extremes and the combination of both extremes were associated with reductions in stony coral diversity. The highest species richness and abundance were found in patch reefs of the Middle Keys, despite exposure to the warmest water-temperature anomaly events (as indicated by DHWs exceeding the coral bleaching threshold of 4) observed during the summers of 1998 and 2010. In Chapter Three, I found that the environmental parameters that best explained the differences in stony coral diversity (species composition and abundance) on patch reefs of the Florida Keys were water turbidity, nutrients, surface water temperature, % surface oxygen saturation and chlorophyll a concentrations averaged over a period of 24 months, along with depth (F = 4.4, R2 = 0.66, R2adj. = 0.40, p < 0.05). Surface water turbidity and depth were the most relevant environmental parameters driving the differences in stony coral diversity (R2 = 0.17, p < 0.05, R2 = 0.10, p < 0.05, respectively). The influence of these environmental parameters decreased towards offshore shallow and deep reefs. In the Florida Keys, stony coral diversity was the highest at patch reefs of the Middle and Lower Keys where exposed to higher water turbidity and nutrients than those in the Upper Keys located in clearer waters. This suggests that, at long-term scales, corals in patch reef environments exposed to higher water turbidity and water temperature variabilities (as reported in Chapter Two) might be better able to withstand thermal and light-induced stress. Moreover, a short-term study (described in Chapter Four) indicated that the net community production (NEP) was similar among sites with different water turbidity levels (i.e., Cheeca Rocks and Crocker Reef; Upper Keys and Sugarloaf Key; Lower Keys) and seasons (May or October). However, the light-adapted photosynthetic efficiencies (F/Fm’) varied spatiotemporally. The highest F/Fm’ values (0.57–0.69) were found at the nearshore patch reef of Sugarloaf Key, Lower Keys, in October 2012. At this patch reef, high light attenuation (Kd (488) = 0.12 m-1) was associated with absorption by colored dissolved organic matter and exacerbated by particulates following thunderstorms. The lowest F/Fm’ values ( This study represents a baseline against which future observations on coral reef biodiversity and net community production in the Florida Keys reef tract may be evaluated.

Tropical coral reefs provide important ecosystem goods and services that are supported by one or more ecosystem functions (e.g., recruitment, primary production, calcification, and nutrient recycling). Scleractinian corals drive most of these functions, but a combination of global and local anthropogenic stressors has caused persistent shifts from coral- to algae-dominated benthic reef communities globally. Such phase shifts likely have major consequences for ecosystem functions; yet, related knowledge is scarce in general, but particularly at the community level, under ‘in situ’ conditions, and under the influence of changing environmental variables. Thus, we conducted a series of interconnected in situ experiments in coral- and algae-dominated reef communities in the central Red Sea, combining traditional community ecology approaches with novel metabolic and biogeochemical assessments from December 2016 to January 2018. Specifically, we (i) examined the influence of coral-algal phase shifts on recruitment and succession patterns, (ii) assessed the role of benthic pioneer communities in reef carbon and nitrogen dynamics, (iii) developed a novel approach to measure functions of structurally complex reef communities in situ, and (iv) quantified biogeochemical functions of mature coral- and algae-dominated reef communities. The findings suggest that coral-algal phase shifts fundamentally modify critical reef functions at different levels of biological organization, namely from pioneer to mature reef communities. For example, community shifts, through a lower habitat complexity and grazing pressure, decreased the number of coral recruits by >50 %, thereby inhibiting the replenishment of adult coral populations. At the same time, a 30 % higher productivity (annual mean) and increased organic carbon retention in algae-dominated communities supported a fast biomass accumulation and community growth, altering the habitat-specific community metabolism and reef biogeochemistry. Seasonal warming amplified these functional differences between coral- and algae-dominated communities, likely promoting a positive feedback loop of reef degradation under predicted ocean warming. Overall, this dissertation provides quantitative data on critical functions of classical and phase shifted novel reef communities, on tipping points for the collapse of community functions, and potential future winners and losers. The knowledge gained with this thesis helps, thereby, to understand how phase-shifted reef ecosystems function and which services will be generated in comparison to coral-dominated reefs under near-future stress scenarios.

Periodically-harvested fisheries closures (PHCs) are a widespread form of community-based marine spatial management used throughout the Indo-Pacific that also is currently being intensively advocated by conservation organizations for supporting productive fisheries and healthy marine ecosystems. However, local implementation of PHCs has historically been designed to support occasional and efficient exploitation of fish stocks, and not necessarily sustainable fisheries yields and stock conservation. The efficacy of PHCs for achieving their historical cultural objectives of periodicity and efficiency of harvest, simultaneously with achieving contemporary fisheries objectives of fisheries productivity and conservation is undetermined. As a result, the utility of PHCs for supporting contemporary ecosystem-based fisheries management is uncertain given environmental, social and climate change. We developed a biological-economic fisheries model of PHCs to test the value of this form of marine resource management for achieving cultural, fisheries and conservation objectives under sustainable and overfishing scenarios. Our results reveal PHCs to be more effective at achieving the multiple objectives than either non-spatial or fully-protected area management when fisher impact on fish behavior is considered. These results describe the performance of PHCs in general when fish behavior is considered, but does not provide detailed guidance for a particular PHC. Thus, we modified and calibrated our biological-economic fisheries model with empirical data from Nakodu Village on Koro Island in Fiji. The calibrated model allowed us to estimate the effectiveness of Nakodu Village’s current PHC management and predict consequences of future management actions. Results suggest that 5-year PHC closures are optimal for simultaneously achieving fisheries productivity and conservation goals in Nakodu Village. These findings challenge the dogma that PHCs are simply a cultural legacy and warrant further investigation of the utility of PHCs for supporting ecosystem-based management beyond the Indo-Pacific.

In the Caribbean, Acropora cervicornis (staghorn coral) exemplifies the worldwide anthropogenic decline of reef-building corals. From the mid-Pleistocene through the mid-1900s, A. cervicornis was a dominant framework builder, providing complex habitat for reef organisms. Since the 1980s, populations of A. cervicornis have declined by as much as 98%. Despite the overall decline, scattered remnants persist, and some appear to be thriving. As in recent studies on other acroporids, if we can identify variation in traits related to resilience in the remaining A. cervicornis, and understand the genetic basis of such variation, we could better forecast the species’ future response to climate change, and inform ongoing restoration efforts. Here, I compare phenotypic and transcriptomic indicators of resilience in A. cervicornis from two nearby but environmentally-disparate habitats on Turneffe Atoll, Belize: Calabash Caye forereef and Blackbird Caye backreef. Blackbird exhibits significantly higher flow, light, average temperature, and temperature variation. Over four years, I conducted a longitudinal study of 122 tagged coral colonies. Corals from Blackbird and Calabash, which I confirmed to be genetically distinct based upon single nucleotide polymorphisms, exhibited pronounced differences in traits related to resilience including the proportion of healthy tissue, chlorophyll, growth, and wound-healing. By most measures, Blackbird corals displayed superior indicators of resilience. Through a two-year reciprocal transplant study involving 120 corals, I identified substantial environmental plasticity in these traits, e.g., Blackbird corals transplanted to Calabash exhibited higher chlorophyll levels and more rapid wound healing than when grown in Blackbird, exceeding the native Calabash corals. RNA sequencing and assembly of site-specific transcriptomes revealed greater diversity of transcripts and genes from photosynthetic symbionts at Blackbird but greater diversity of bacterial associates at Calabash. Single nucleotide polymorphism (SNP) analyses using RNAseq data determined that corals from the two sites were separate putative populations. Principal components analysis of gene expression in natives and transplants revealed a clear distinction based on site of origin, but also a clear effect of environment. Thousands of differentially expressed genes distinguished the sites, including many genes implicated in heat stress, oxidative stress and UV-light stress. This genetic and phenotypic diversity of remnant staghorn populations on Turneffe represents a potential basis for future re-expansion of this important framework builder through natural or assisted shifts toward resilient populations. / 2023-02-03T00:00:00Z

Coral reefs around the world are at risk from overexploitation and climate change, and coral reefs of the Red Sea are no exception. Science-based designation of marine protected areas (MPAs), within which human activities are restricted, has become a popular method for conserving biodiversity, restoring degraded habitats, and replenishing depleted populations. The aim of this project was to explore adaptable methods for designing locally-manageable MPAs for various conservation goals near Thuwal in the central Saudi Arabian Red Sea while allowing human activities to continue. First, the potential for using simple spatial habitat distribution metrics to aid in designing MPAs that are well-connected with larval supply was explored. Results showed that the degree of habitat patchiness may be positively correlated with realized dispersal distances, making it possible to space MPAs further apart in patchier habitats while still maintaining larval connectivity. However, this relationship requires further study and may be informative to MPA design only in the absence of spatially-explicit empirical dispersal data. Next, biological data was collected, and the spatial variation in biomass, trophic structure, biodiversity, and community assemblages on Thuwal reefs was analyzed in order to inform the process of prioritizing reefs for inclusion in MPA networks. Inshore and offshore reef community assemblages were found to be different and indicated relatively degraded inshore habitats. These trends were used to select species and benthic categories that would be important to conserve in a local MPA. The abundances of these “conservation features” were then modeled throughout the study area, and the decision support software “Marxan” was used to design MPA networks in Thuwal that included these features to achieve quantitative objectives. While achieving objectives relevant to fisheries concerns was relatively more challenging, results showed that it is possible to design a local MPA that achieves fisheries and biodiversity goals simultaneously. However, future work should focus on expanding the biological dataset and on acquiring socio-economic data in order to formulate a comprehensive local management plan.