The study documents seagrass patch dynamics over large spatial extents in Tampa Bay, Florida. Using GIS techniques a set of fine scale seagrass maps was created within locations previously identified as "patchy" seagrass or areas of seagrass loss. Thirty randomly selected landscape windows of various extents were mapped for the years 2004, 2006, and 2008 by visualizing 0.3 m resolution color imagery on-screen at a digitizing scale of 1:500 using a minimum mapping unit of 1 m2. Characteristics of seagrass patches and patterns of seagrass change were quantified using area-based and time interval metrics including total seagrass area, percent change in seagrass area, seagrass percent cover, and number of patches. Patterns of change were then reviewed at multiple levels of spatial organization and multiple temporal scales. Results from seagrass mapping generated from the fine scale (1 m2 resolution) and previously-reported broad scale (2.02 ha resolution) mapping approaches were also compared. The study documented seagrass patches ranging in size from 1 m2 to greater than 10,000 m2. The fine scale mapping data reported a net increase in seagrass cover from 2004 to 2008. However, only 19 landscape windows were either stable in cover or contributed to the gains in seagrass documented during the study. The remaining 11 landscape windows exhibited various temporal patterns in seagrass loss where patch contraction, complete patch mortality, seagrass fragmentation, and seagrass gap formation were all documented. Results from fine scale mapping indicate that the amount of total seagrass patch area represented by locations categorized as "patchy" in broad scale mapping were, on average, 44 percent less than estimated by the broad scale maps. Together these findings provide new information on how different mapping techniques may produce variable views of seagrass dynamics.

No description available.

Rhizophytic algae are large, abundant primary producers throughout tropical and subtropical areas worldwide where they grow as an understory in seagrass beds, as well as form mixed or monospecific beds of exclusively rhizophytic algal species. In this dissertation, "rhizophytic algae" refers to coenocytic green algae (Chlorophyta) in the order Bryopsidales that use a net of rhizoids to anchor in unconsolidated sediments. In the development of seagrass beds, rhizophytic algae colonize bare patches and are thought to facilitate seagrass colonization by stabilizing sediments and providing organic matter. However, despite their prominence little is known about many aspects of the ecology of rhizophytic algae. Detailed information on the abundance and biomass of rhizophytic algae at the species level is scarce and the belowground components are seldom quantified. Moreover, rhizophytic algal communities located along the central west coast of Florida have received very little study. At three shallow coastal sites in the Lower Florida Keys and one on the central west coast of Florida, I measured the abundance, biomass, organic content, and morphometric features of the above- and belowground portions of all rhizophytic algal species present along transects in seagrass-algal bed habitat. Relatively diverse assemblages of these algae were present both in areas with and without a seagrass canopy, though dense (greater than or equal to 50%) seagrass cover correlated with decreased algal richness. Rhizophytic algal densities at Keys sites ranged from 68 - 143 thalli m-2 with total dry weights of 76.4 - 226.7 g m-2 with only calcified species present. The west coast of Florida site had the highest aboveground organic biomass (180 g m-2), the highest abundance of rhizophytic algae (365 thalli m-2), and abundant uncalcifed algae of the genus Caulerpa. Morphometric characteristics varied within a species among sites and may reflect differences in abiotic variables such as sediment grain size. The anchoring structures of these algae, made up of fine rhizoids and attached sediment, occupied up to 5.3% of the total volume of the top 5 cm of substrate. My results indicate that across rhizophytic algal species, even within a genus, the production of belowground structure and potential influence on ecosystem function is highly variable and not necessarily related to the aboveground biomass. These results provide new information on belowground structure provided by rhizophytic algal species and characterize the rhizophytic algal community on the central west coast of Florida. The role of rhizophytic algae in seagrass bed succession has been recognized, but little is known about the rate and species composition of colonization of recently created bare patches. In a series of field experiments at three sites on the central west coast of Florida, recruitment by rhizophytic algae into created cleared areas was rapid and dominated by two species of Penicillus and Udotea flabellum. In three weeks, rhizophytic algae were able to recruit, grow to their full height, and bind sufficient sediment to create full-sized holdfasts. Additional field experiments described here show thalli of all of the rhizophytic algal species tested (three species in three genera) were able to regenerate from holdfasts (with small stubs of stipe attached) in a matter of weeks. Overall, my results suggest that belowground structures play a key role in recolonization by, and recovery of, rhizophytic algae after disturbance and are likely important to the long-term persistence of these algal populations. Bryopsidalean algae often have high concentrations of defensive compounds inside their thalli and these terpenoid secondary metabolites possess anti-fouling capability in laboratory tests. Because fouling is ubiquitous in marine environments and epibonts have harmful effects on their hosts, researchers have proposed that rhizophytic algae use these compounds to prevent fouling. For this to be an effective strategy, the compounds must be presented to potential colonizers on the external aboveground surfaces. Thus, I examined the chemistry of rhizophytic algal surfaces using extractions that avoid mechanical damage. Secondary metabolites were not detected in the surface extracts of four species while these compounds were detected in the whole plant extracts. My results, coupled with previous studies on the degradation of these metabolites in seawater and the presence of fouled plants in the field, and suggest non-polar secondary metabolites are not deployed onto the surfaces of rhizophytic algae as a defense against fouling.

Thalassia testudinum Banks and Solander ex König is the dominant seagrass in the Gulf of Mexico, Caribbean and the West Coast of Florida, yet little rhizome elongation, new short shoot production, or new rhizome meristem production data has been collected via direct measurement. A study of the rhizome growth of T. testudinum was completed in December 2004 in southern Tampa Bay that determined growth after 26.5 months. Two PVC planting frames each containing four rhizomes with 2 short shoots, two rhizomes with 4 short shoots, and two rhizomes with 8 short shoots were planted next to existing T. testudinum beds at 5 sites (n = 10 planting frames). The rhizome apical meristem was removed from half of each set of short shoot units on each planting frame. Plants initially lacking a rhizome meristem produced more new long shoot meristems than those planted with an intact meristem, and larger planting units produced more new rhizome meristems than smaller ones, P = 0.001 and P < 0.001, respectively. The total number of rhizome meristems per planting unit (new meristems + initial meristem) was greater in plantings initially lacking a long shoot meristem in the 2, 4 and 8 short shoot size classes. Only the two short shoot plants benefited from an intact rhizome meristem at planting time, elongating 66.4 cm versus 60.4 cm for plants initially lacking a rhizome meristem at 26.5 months. In the 4 and 8 short shoot classes, plants that lacked a rhizome meristem at planting outpaced those with a meristem, producing 192.1 and 277.9 for 4 and 8 short shoot plants compared to 120.9 cm and 177.7 cm for plants with a meristem during the same time period. The greatest growth rate increases were due to lateral branching on planting units that lacked a rhizome meristem in the two largest size classes (4 and 8 short shoots); the differences between plants with an intact rhizome meristem and those without with the size classes pooled did not prove to be statistically different, P = 0.112. Differences among the size classes were significant, however, P < 0.001. Analysis of new short shoots was analogous to the results for rhizome elongation, with the presence of an initial rhizome factor proving insignificant, P = 0.401, and the initial number of short shoots factor proving significant, P < 0.001. The rhizome growth, new short shoot production, and new rhizome meristem production data determined by direct measurements in this study appear to be the first planting unit measurements for this species under natural conditions.

The Tay estuary is situated on the east coast of Scotland. The estuary is dominated by sediment biotopes, including mudflats which support sparse beds of two nationally scarce seagrass species, Zostera marina var. angustfolia (Hornem.) and Z. noltii (Hornem.). Seagrasses have been described as ecosystem engineers, shaping their sediment environment, and this may increase sediment deposition and stability. In this thesis the ecosystem engineering characteristics of seagrass habitats are explored. In 2008, the distribution of Zostera spp. in the Tay estuary was surveyed and mapped for the first time. Sediments within beds of Z. marina and Z. noltii were compared to investigate the influence of seagrasses on sediment characteristics. To explore the role of seagrass in sediment deposition and erosion, and coastal stability, sediment depth measurements were made in patches of Z. noltii, Z. marina and bare sediment over one year. The role of the root/rhizome system on sediment retention over winter was also considered. Sediment deposition in Z. noltii beds, and the influence of the plants on near-bed flow dynamics was further explored in the laboratory, using an 8 m seawater flume. In the field the retention of particles over 2 and 14 tides was measured, and the results of this experiment led to a study of the influence of leaf and sediment biofilms on particle retention, using the novel method of magnetic particle induction (MagPI). The efficacy of artificial seagrass beds and Z. noltii transplantation as habitat restoration techniques were compared over one year. During the trial, sediment deposition and changes in sediment characteristics were determined, and the protection given to saltmarsh cliffs fringing the study plots was assessed. Mechanisms underlying the results are suggested and the findings discussed. This study provides an insight into the ecology of seagrass in the Tay estuary and its role as an ecosystem manager. It may offer valuable data which could be utilised for future conservation policies, habitat restoration schemes and management planning of the area.

The tropical seascape is herein defined as a landscape made up of five ecosystems: coastal terrestrial forests, mangrove forests, seagrass beds, coral reefs and the deep sea. Previous studies have shown that men and women use the tropical seascape in different ways. If the seascape was to change as a result of anthropogenic climate change, then men and women could potentially be affected differently by those changes. The seascape is particularly vulnerable to the predicted rise in sea-level and ocean warming, but the coastal terrestrial forests and mangrove forests are in addition vulnerable to the increased storms and hurricanes a warmer climate is predicted to lead to. While men and women utilizes these ecosystems in many different ways, this study found, based on the literature reviewed, that in a worst-case scenario all parts of the seascape could potentially be destroyed and none of the activities performed there today could be performed in the future. The deep sea would not be destroyed, but the fish living there would move to higher latitudes and deeper waters, effectively ending the fishing practices in the tropical waters. To save the tropical seascape anthropogenic climate change would have to stop on a global scale, since the problem cannot be solved on a local or regional level.

Caulerpa taxifolia is a marine alga notorious for its introduction and subsequent colonization of the Mediterranean Sea. It is recognized as one of the 100 worst invasive species, and it is suggested that much of its expansion may have been at the expense of native seagrass beds. To date, the bulk of research on C. taxifolia has centred on quantifying expansion and methods of eradication. There are few quantitative data on the relationship between C. taxifolia growth and environmental characteristics (e.g. light, temperature, nutrients). Furthermore, once C. taxifolia has been introduced to a system it is exceptionally difficult and expensive to eradicate. Accordingly the implications, both positive and negative, of this new habitat type must be considered in the context of the new habitat mosaic into which it fits. Australia is unique in that it has both native and invasive populations of C. taxifolia. These populations offer not only an opportunity to examine the dynamics of C. taxifolia beds and their associated communities at different latitudes and temperature and light regimes, but especially in the context of a high diversity marine coastal environment. The objectives of this thesis were to use native (Moreton Bay, Queensland) and invasive (Pittwater, New South Wales and Port River, South Australia) populations of C. taxifolia to: 1) quantify the relationship between environmental drivers (light, temperature, nutrients) and C. taxifolia growth, and 2) examine differences in habitat use and function between seagrass, C. taxifolia, unvegetated substrate. Most of the locations in Australia where large C. taxifolia beds occur are adjacent to urban areas that have a degraded water quality. Manipulative experiments in Moreton Bay demonstrated that nutrients stimulate C. taxifolia growth, however, light availability and seasonality appear to influence the response of C. taxifolia growth to nutrients. Short-term manipulative experiments were conducted across a range of seasons and locations, to capture the effects of temperature on growth. Temperature was the dominant factor affecting rate of stolon extension in both native and invasive locations. Colonization potential of C. taxifolia appears to be driven by ambient water quality (light and nutrients) and bed expansion is driven by temperature in systems where nutrients are saturating. Epifaunal communities sampled by beam trawl were dominated by the families Palaeomonidae, Terapontidae, Scorpaenidae, Monacanthidae, Syngnathidae, Gobiidae, and were largely similar between seagrasses and C. taxifolia; however, syngnathids were absent from C. taxifolia beds. I examined habitat use patterns between seagrass (Zostera muelleri), C. taxifolia, and unvegetated substrate. Fish preferred seagrass to C. taxifolia; however, in the absence of a seagrass fish used C. taxifolia. While C. taxifolia may have similar structural benefits to some seagrasses, there are fewer food resources available within C. taxifolia beds. Furthermore, grazing may be limited to a few specialist grazers. Within the habitat mosaic, C. taxifolia will provide some benefit over an unvegetated substrate; however, that benefit might mask losses in system quality or resilience by decreasing the threshold level for change within the community. Therefore, should a perturbation occur (e.g. sudden drop in water temperature, filamentous algal bloom) a system comprised solely of seagrass could withstand such stress; however, a habitat mosaic of seagrass and C. taxifolia could have a rapid and dramatic loss in its ability to sustain a diverse faunal community. Ultimately, it is most important to protect the system from anthropogenic degradation so it is more resilient to environmental changes.

ABSTRACT The tropical and subtropical nearshore marine environments of Queensland, Australia sustain diverse and unique marine wildlife. Continuous population growth and land-use changes along the Queensland coastline are known to exert numerous anthropogenic pressures on these marine ecosystems, including the delivery of high sediment loads. Sediments also provide a transport pathway for persistent organic pollutants (POPs) from rural and urban catchments into the marine environment. While such pollutants are known to be elevated in marine sediment and biota from nearshore areas in Queensland, their input and distribution pathways, as well as exposure and associated risks to wildlife populations are only partially understood. Mounting evidence suggests that POPs may contribute to population declines in marine wildlife species; however, limited information is available regarding the accumulation and effects of these contaminants in endangered or threatened marine turtles. This study aimed to redress some of these information gaps using a case study approach in marine turtle habitats of Moreton Bay, and other embayments in Queensland. Among persistent organic pollutants (POPs), dioxins (polychlorinated dibenzo-p-dioxins; PCDDs) and to some extent also dioxin-like PCBs (polychlorinated biphenyls; PCBs) were found to be widespread and often present at elevated (ppb) levels in surface sediments from Moreton Bay. However, while PCDD/F toxic equivalencies (TEQs) are above international (Canadian) sediment quality guidelines at numerous sites in Moreton Bay, in general TEQs across the Bay are relatively low compared to those from contaminated locations near dense industrial activities. POP contamination in surface sediments across Moreton Bay was investigated by a combination of GIS spatial mapping, geostatistical and traditional statistical modalities. High spatial variability and complex spatial distribution patterns were revealed. High resolution GIS kriging model outputs from the mid to southern Bay facilitated identification of distinct sediment contamination zones, with highest PCB and PCDD/F levels present in nearshore locations, associated with nearby river systems. While primarily governed by organic carbon, a multitude of physical, chemical and hydrological factors were identified to influence the spatial variance of PCDD/F concentrations. The main parameters governing PCDD/F spatial distribution were identified as sediment geochemistry, water depth and anthropogenic alterations of the physical environment and, together, all quantifiable explanatory variables (including hydrodynamic flushing) explained ≈75% of spatial PCDD/F variance. Together, the interaction of these parameters results in complex distribution patterns and highly variable concentrations even among neighbouring sites of 1-3 km resolution. These results suggest that prediction models of POP distributions in the nearshore marine environment may require high-resolution validation, and highlights that the design of low resolution monitoring strategies can have profound impacts on the reliability of contaminant information or any subsequent extrapolations. This knowledge and methodology can be utilised to optimise on-going and future near-shore sediment monitoring programs both locally and in other regions around the world. Using the spatial distributions of dioxin-like contaminants within sediments, this study provided an opportunity to assess field-based relationships between habitat contamination and local marine biota contamination. Detectable levels of PCDD/Fs and dioxin-like PCBs were measured in all green, hawksbill, loggerhead and flatback marine turtle tissues. POP concentrations in sediments were found to significantly correlate with those in the herbivorous green turtle from different sediment contamination zones. These findings demonstrate that sediments represent an important secondary contaminant source and lead to redistribution of POPs to the marine food chain. POP concentrations and TEQs clearly increased from sediment to turtles as well as with increasing trophic levels in marine turtle species. The results from this study demonstrate that the extent of sediment contamination within foraging habitats governs marine turtle exposure, while, trophic status and to some extent age influence contaminant exposure within a particular contamination zone. Despite the relatively low TEQ in sediments from Moreton Bay, TEQ levels in green turtle sub-populations foraging from near-shore locations and higher trophic loggerhead and flatback turtles are similar or elevated compared to those reported for other marine wildlife from Moreton Bay and elsewhere, even compared to higher trophic species from locations impacted by dense industrial activities. High bioaccumulation potential of 2,3,7,8-PCDD/F and dioxin-like PCBs compounds were estimated for green turtles using biota to sediment accumulation factors. Selective accumulation of toxicologically more potent (i.e. lower chlorinated) PCDD/Fs was observed for higher trophic marine turtles, resulting in increasing TEQs for the carnivorous species. Biomagnification was also observed for some non-2,3,7,8-substituted dioxin congeners which typically do not accumulate in most biota. These results are proposed to be due to relatively high accumulation efficiency and/or low metabolic capacity for these POP compounds in marine turtles. These findings are also hypothesised to reflect temperature dependant, greater bioavailability of hydrophobic chemicals in sub-tropical and shallow marine systems. An additional pilot study revealed that in contrast to PCDD/Fs and PCBs, levels of persistent flame retardants (polybrominated diphenyl ethers; PBDEs) were relatively low in marine turtles and other marine species (dugong, fish and shellfish) from Moreton Bay. This suggests relatively low level input of these more recent industrial products into the marine environment. However, as elevated levels of PBDEs have been reported in blood from the general population of Australia, ongoing transport from the terrestrial to the marine system and redistribution of these contaminants, similar to PCDD/F and PCBs, would be expected to occur into the future. Limited information is available regarding the sensitivity of reptiles to and effects of POPs, however, studies have shown that reptiles are sensitive to POPs albeit with uncharacterised relative potency. In the absence of robust toxicological information for reptiles or marine turtles, the potential risks associated with PCDD/F and PCB exposure of Queensland turtle populations was evaluated using toxicity for sensitive biological endpoints observed in mammals and birds. Using probabilistic methodology for marine turtles from Queensland, the body burden of up to 31% and 55% of green and loggerhead turtles, respectively, are above the threshold levels where the most sensitive physiological effects are observed in mammals and birds. While this evaluation illustrates that the contaminants investigated have the potential to impact on the health of marine turtle populations, it must be highlighted that it is compromised by the lack of species-specific (and in this case, class-specific) information, the uncertainty of which is often considered to represent a factor of at least 10. The findings of the present study indicate that exposure to POPs has the potential to adversely affect the health of Queensland’s marine turtle populations, and highlight the need for robust information on reptile specific sensitivity to these compounds.

Made available in DSpace on 2014-12-17T14:01:58Z (GMT). No. of bitstreams: 1 AlineSM.pdf: 1989491 bytes, checksum: 8a1f759349023fd90f5d13c4289e236d (MD5) Previous issue date: 2008-03-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The mollusks present a great taxon variety and life habits in coral reefs being good environmental indicators. It is important to know the distribution pattern of the mollusks and the processes that influence it, so that disturbances in sea ecosystems could be monitored. The present study aims to accomplish the inventory and distribution of epibenthic mollusks in the Parracho of Maracaja?. 23 sites in different habitats of the Parracho were settled: 11 in the reef habitat, 3 in the sandy bottom and 9 in the seagrass bed. Qualitative and quantitative samplings have been done through snorkeling and scuba diving. Three band transects (10m?) were sampled in each site and the data were obtained to each m? of the transect, where the species were counted and the environmental variables (rugosity and recovery of the substratum) were valued. The data were submitted to multivariate analyses in order to find possible distribution patterns that could be associated to the substratum variables. The diversity indexes were calculated for each reef sites and compared with each other. A number of 46 species were registered. The reef habit at should to be the richnest area while the sandy bottom was poorest one. In the reef habitat, the mollusks were associated to rugosity and recovering of frondose algae and zoanthids, while for the seagrass bed, the animals exhibited a richness variation associated to the muddy and sandy sediment. There were found 3 species economically explored, what requires an appropriate management for the maintenance and conservation of the area resources in a sustainable way / Os moluscos apresentam uma grande variedade de t?xons e h?bitos de vida nos recifes de coral mostrando-se bons indicadores ambientais. ? importante conhecer sua istribui??o e os fatores de influ?ncia a fim de auxiliar no monitoramento de poss?veis dist?rbios no ambiente marinho. O presente estudo teve por objetivo realizar o levantamento e distribui??o dos moluscos epibent?nicos no Parracho de Maracaja?. Foram definidos 23 s?tios de amostragem nos diferentes habitats do Parracho sendo 11 no habitat recifal, 3 no fundo arenoso e 9 nas faner?gamas marinhas. Foram realizadas amostragens qualitativas e quantitativas atrav?s de mergulhos livres e aut?nomos para obten??o dos dados de moluscos e caracter?sticas do substrato. Em cada s?tio foram amostrados 3 transec??es em faixa de 10 m?, onde os dados foram registrados a cada m? da transec??o, sendo ent?o contadas as esp?cies e valoradas as vari?veis ambientais (rugosidade e cobertura do substrato). Os dados foram submetidos a an?lises multivariadas para encontrar poss?veis padr?es de distribui??o, associadas ?s vari?veis de substrato mensuradas. Tamb?m foram calculados os ?ndices de diversidade para os s?tios recifais e comparados entre si. Registraram-se 46 esp?cies, com maior riqueza no habitat recifal, seguida nas faner?gamas marinhas e com menor valor, no fundo arenoso. No habitat recifal, os moluscos apresentaram-se associados ? rugosidade e cobertura de algas frondosas e zoant?deos, enquanto nas faner?gamas, os animais exibiram uma varia??o de riqueza associada ao sedimento lamoso e arenoso. Foram encontradas 3 esp?cies exploradas comercialmente, sendo necess?rio o manejo adequado visando a manuten??o e conserva??o dos recursos para a regi?o

The 3-dimensional structural complexity of coral reef environments is positively correlated with measurements of biodiversity and biomass. EcoReefs are a type of artificial reef that resemble branching corals, such as Acropora cervicornis, which provide an environment of high structural diversity, and that are effective at recruiting and sustaining fish populations. Little is known, however, about the effects of EcoReefs on the surrounding environments in which they are deployed, so this study examined the results after installing Ecoreef modules in a seagrass environment. The installation occurred in March 2009 at Coco Cay in the Berry Island chain in the Bahamas and data was taken over the next two years to compare changes on Ecoreef deployment sites (experimental sites) to sites with no EcoReefs (control sites) and also an older and larger installation with both EcoReefs and Reefballs (Old Reef) that dates back to 2004. Two main categories of information were collected: at the same time (a) the changes in growth of two types of seagrass, Thalassia testudinum and Syringodium filiforme, and (b) the changes in fish populations in and around the EcoReef installations. Experimental sites consisted of 3 groups, 30-35 metres apart, each of 12 EcoReef modules in seagrass beds off the east side of the island. Both seagrass and fish data were collected within the module groups and also for the area 1 metre around the installation to see if there were any “halo” effects, i.e. where seagrass around a reef is cleared by resident fish populations. Seagrass measurements including direct measurements of blade length, width, percentage of epiphytic fauna, and the percentage of dead tissue on each blade were collected. Seagrass coverage was also estimated using a photographic technique. Fish counts were performed using a modified Bohnsack-Bannerot visual survey method, and augmented with transect counts. The results for seagrass indicated that there were some seasonal changes in growth and coverage. Fish populations accumulated rapidly on the Ecoreef modules: at the first-post installation collection data period 4 month later the experimental site fish populations were between 30 and 153 individuals, and remained at this level throughout the study, with a mean population per site of 84.4 individuals over the length of the study. Over the study period it was found that the majority of the fish (67%) on the experimental sites were haemulid, and scarid juveniles of less than 5 cm in length, in contrast to the older and larger mixed reef that had 73% above 5cm, including a stable population of 184 (+/- 24.5) grunts. The older site also had a distinct halo zone of cleared and cropped seagrass, whereas no halo zone was visible at the experimental or control sites, suggesting that the abundance and size of the fish establish and maintain this zone. The results from this study suggest that EcoReefs modules foster fish populations and cause changes in seagrass length, but do not result in the formation of a halo zone directly; the formation of this zone, where present, is likely the result of the fish species that settle on these structures.