Swan Bay is a shallow marine embayment of Port Phillip Bay, just north of Queenscliff, Victoria. It has been part of the Harold Holt Marine Reserves since 1977 and is a seagrass habitat. This study investigated the species of fish present in the inter-tidal zone of Swan Bay, collected information on their ecology, investigated the importance of Swan Bay compared to Port Phillip Bay as a nursery and/or breeding area and compared these results with those of similar seagrsss habitats. Field work was carried out monthly over a two year period, from April 1981 to April 1983, using beach seine nets at Swan Bay and Portarlington. Forty four species of fish were identified from Swan Bay and nineteen from Portarlington. Fish were most abundant during the summer and autumn months when seagrass growth was at a maximum and least abundant during winter due to the absence of seasonal residents and decreased numbers of permanent residents. Swan Bay was found to be an important nursery ground for two commercially-caught species: the Yellow-eye Mullet and the King George Whiting. Juvenile Yellow-eye Mullet were more numerous in Swan Bay than at Portarlington. Smell juvenile King George Whiting were more abundant at Portarlington than in Swan Bay where older juveniles were more numerous. The fish fauna of Swan Bay was found to be similar to western Port but the abundance of species varied. Atherinosome microstoma was the dominant species in terms of abundance and biomass. Diet was found to be different from that reported by Robertson (1979) at Western Port due to the different range of prey items.

Boundaries between adjacent habitats can create unique biotic and abiotic conditions, varying species compositions and abundances between the edge and interior of habitats. As habitats become fragmented, the relative amount of edge increases. Understanding the role that habitat edges have in determining species compositions and abundances is fundamental for conservation and management of habitats, particularly those under threat from fragmentation. Seagrass habitats are common nearshore habitats that harbour a rich and diverse faunal assemblage that are under threat worldwide from human disturbance. Human induced fragmentation, and the propensity of seagrass to form naturally patchy landscapes, makes it an ideal system to study the effects of edges on fauna. / Evidence of fish displaying edge effects in seagrass habitats is equivocal. Assessment of fish edge effects was done by sampling seven positions within seagrass habitats at fine spatial scales. Strong, consistent patterns in fish distributions demonstrated clear edge effects both within and alongside seagrass at these sites. The total number of fish sampled was greater at the seaward seagrass edge than the seagrass middle, but there was little difference between the seagrass middle and the shoreward seagrass edge. Four individual fish species showed preferences for the seagrass edges. Further investigation revealed that patch size could influence the magnitude of edge effects in seagrass beds. Fish were sampled in ten variously sized seagrass patches in three positions within each patch. Two species showed variations in edge effects across patches which could be attributed to the area of the patch. Changes in patch size can influence the magnitude of edge effects that species display, suggesting that patch area effects (fish density varying with patch size) could be caused by edge effects. / Food availability and predation are mechanisms commonly used to explain edge effect patterns. Gut analysis was done on Stigmatopora nigra sampled at the edge and middle of patches to determine if prey consumption varied between positions, and explain S. nigra distribution. There was little difference in prey consumed by S. nigra at the edge and middle of patches, suggesting that food was unlikely to be causing S. nigra edge effects, or that the influence of prey distribution was being masked by other factors such as seagrass structure. Predator abundances and foraging efficiency may vary at the edge and middle of patches, and consequently influence the distribution of prey fish within patches. Underwater videos were placed at four positions within seagrass habitats to assess predator distributions. Predatory Australian salmon, Arripis spp., spend more time over adjacent sand than other positions, while small potential prey species (King George whiting, Sillaginodes punctata, recruits) appear to prefer the middle of seagrass patches, possibly to avoid encounters with salmon. To test if the predator-prey distributions reflected actual predation pressure, a tethering experiment was done to determine if predation was causing edge effects in small fishes. / King George whiting recruits and pipefish (Stigmatopora spp.) were tethered at each of the four positions at different depths. Survival time of whiting recruits was greater in the middle of shallow seagrass patches than other positions. Few pipefish were preyed upon, and survival time was lower over sand adjacent to seagrass than at the seagrass edge or middle. Video footage revealed that salmon was the dominant predator of both whiting recruits and pipefish. The distribution of predators and associated predation can explain edge effects for some species (whiting) but other mechanisms, or a combination of mechanisms, are determining edge effects for other species (pipefish). / Edge effects were common amongst fish species in seagrass habitats, and included permanent, temporary and predatory species. Patch size was found to influence the extent of the edge effect. There was little evidence to support prey consumption as an underlying mechanism causing higher fish abundances at the interior or edge of patches, however there was evidence that predation could be causing edge effects. Changes in fish distributions within seagrass patches due to patch size and predation when seagrass undergoes fragmentation need to be considered by not only ecologists, but also by managers in the development of plans for seagrass conservation. Future studies should investigate the relative contribution of different edge characteristics in determining the degree of seagrass edge effects.

This study refers to developed ecological model abroad, and established the seagrass model with MATLAB compiler. I also took the seagrass meadows in south Taiwan-Nanwan for my studying case, and simulated the dynamic effect of seagrass and epiphyte biomass, as well as nutrient, and attempted to go on probing into the cause with northeast monsoon and typhoon. The simulating site of this study was Nanwan, which is located at Hengchun Peninsula, the southern tip of Taiwan. The dominant species in this area is Thalassia hemprichii. South Taiwan is situated at a tropical climate, and the variation of air temperature is small. Additionally, Kurshio embranchment cause the variation of water temperature smaller, about 24 (¢J) to 30 (¢J).The northeastern monsoonal winds, formed downhill winds, are extremely forceful from October to April, so the wind speed is greater during this period than the rest of the year. In South Taiwan, dry-wet season is clearly. The dry season is from November to April, and the wet season is from May to October. The main rainfall comes from southwest monsoon, especially summer typhoon (June to September). The wind speed is raised abruptly by typhoon and makes water agitate, which not only cause the mortality raising but also the sediment turbulence. By Lin¡¦s research (2005), the growing area of seagrass meadow in Nanwan is a half-closed tidal pool where human makes huge effect and there is a lot of drainage of house and inn sewage. Furthermore, these seagrasses in Nanwan would be exposed to air during the period of poor tide and the emerged period is the longest of these three areas -Nanwan, Dakwan and Wanliton. The seasonal dynamic of seagrass, which is located in the high site of intertidal zone, is obvious, and the biomass is larger in summer than in winter; but that is not obvious in the low site and tidal pool. By the seasonal condition and some specially climate condition mentioned above, the analysis of simulate cases would be go on. Comparing of the modeling result and real measurement, the seasonal changing situation mostly match up. No matter high site (emerged and dried) or low site, there is the maximum of seagrass biomass (including above ground, below ground, or shoot density) in summer, and the minimum in winter. Typhoon causes the biomass losing abruptly in summer. R/S ratio (below-ground biomass division above-ground biomass) is bigger in winter than in summer. On one hand the inside nitrogen redistribution is larger in summer, because the larger growth rate occurs in summer, and the more nutrient is supplied from roots, on the other the redistribution is smaller in winter cause the less nutrient is supplied from roots. Epiphyte biomass has the maximum in summer, when the nutrient concentration of water is larger. In the section of the difference between low and high site seagrass, it is apparent that the high site seagrass would be exposed to air and dried by northeast monsoon. Although typhoon comes up, its influence is not so strong as northeast monsoon at high site. The maximum biomass still occurs in summer, and it is presumed that the living environment of high site seagrass is with more pressure by nature. The above-ground biomass of high site seagrass is smaller than low site, but the below-ground biomass is much lager at high site. Besides, shoot density is larger at high site. The biomass of epiphyte is larger at low site just opposite to shoot density. It is supposed that high site seagrass is emerged to air and limited by environment factors so above-ground biomass would be reduced and store up the sustenance to below-ground biomass. It is conjectured that the main factor with shoot density is affected by light density and below-ground biomass. In shallow water, the seagrass at high site could accept more light energy, moreover the below-ground biomass is sufficient and the recruitment rate is large, thus there are more shoots at high site. Epiphytes are also limited by water depth and wind, and the biomass of epiphyte at high site is smaller than at low site.

Seagrass productivity is largely limited by nutrient and light availability. However, increasing evidence suggests that sedimentary geochemical processes may play an essential role in seagrass productivity/health. Much of this work has been largely phenomenalistic and has not clearly identified the spatio-temporal behavior of the major geochemical parameters involved in diagenesis of seagrass sediments. In this study, a much broader range of both dissolved and solid phase chemical parameters in eelgrass vegetated sediments was investigated. Parallel measurements were made on adjacent unvegetated sediments (<10 m) to more clearly refine the specific influences of seagrass (Zostera marina) on chemical gradients in associated sediments. Previous studies have pointed strongly toward diurnal ??ventilation?? of sediments vegetated with seagrass by the exudation of photosynthetically produced oxygen. However, strong lateral variability of sediment geochemical parameters among and between seagrass vegetated and unvegetated sediments made the observation of diurnal effects sufficiently difficult. Changes resulting from temporal variability were difficult to discern within the spatial variability. A critical question that is often not dealt with in the study of the early diagenesis of sediments is what spatial and temporal sampling intervals are required to account for the dominant source of variability. The auto-covariance function (ACF) was used to determine the optimum scaling length for sample intervals (?x) of ?H2S and Fe2+. Characteristic scale lengths obtained for sediments from seagrass environments are not significantly different from those observed for unvegetated sediments and averaged 13.7?? 2.2 mm. Lateral variations in our scales analyses showed that scale length approximated our sampling interval and that lateral sampling intervals were smaller than the vertical sampling intervals. Our results indicate that macrofauna dwelling in the sediment, the seagrass root/rhizomes, and aggregations of bacteria, microalgae, and meiofauna may be responsible for the vertical and lateral variability. Model calibrations and sensitivity analyses from a sediment-seagrass diagenetic model revealed that changes in physical parameters of the sediments (irrigation, advection, and porosity, for example) had the greatest effect on organic carbon and total dissolved sulfides. This study revealed that sedimentary geochemical parameters that are both vertically and laterally heterogeneous may also affect seagrass productivity.

Remote sensing reflectance data collected with a remotely operated vehicle (ROV) were used to derive bottom albedo and optical properties for a shallow marine environment near Lee Stocking Island, Bahamas. Optical model inversion techniques were applied to hyperspectral measurements of remote-sensing reflectance to derive water absorption and backscatter coefficients. Using these derived water properties, path attenuation and radiance effects were removed from bottom observations to derive bottom albedos. Histograms from multispectral, hyperspatial video images were used to determine the albedo range of optical end members observed in scenes of sand and seagrass. Variations of spectral signatures for optical end members caused by path-adjacency effects are shown to influence the reflectance measurements. Low-altitude albedo histograms for heterogeneous scenes demonstrate higher contrast between sand and seagrass than is observed at higher altitudes, even after correction for path radiance and attenuation effects. For example, reflected light from bright sand scatters into the field of view of dark seagrass, while less light scatters out from the seagrass into the field of view of sand. This decreases the apparent sand albedo, and increases that for seagrass when viewed from higher altitudes, including aircraft. Evidence provided suggests that simple bottom classifications based upon expected albedo values for scene end members are in error unless the water depth is very shallow.

The Padthaway Ridge is overlain by a thin veneer (< 20 m) of Oligo-Miocene bioclastic carbonates representing the southern most extent of the Mannum Formation, Murray Supergroup, and Murray Basin limestones. The Mannum Formation is composed of warm-temperate carbonates rich in irregular echinoids, coralline algae, benthic foraminifers, and relict particles. The respective lithology are mostly structureless, burrow-mottled, and cross-cut by Thalassinoides burrows. These sediments are interpreted to have resulted from carbonate production along shallow, illuminated seafloors under high mesotrophic conditions. The composition and texture is similar to that of modern temperate seagrass accumulations with the exception of the abundant mobile infauna and bioturbation, which are more akin to associated intercalated and adjacent barren sands. The Mannum Formation is therefore interpreted as an amalgamation of these two environments. The ubiquitous relict grains and Fe-stained cements in the lithologies of the Mannum Formation are thought to be the product of Fe redox pumping within the subsurface of seagrass meadows, whereby consolidated sediments endured prolonged and repeated exposure to juxtaposed destructive and constructive diagenetic conditions at the redox boundary. Fluctuations in the organic carbon and oxygen influx to the subsurface are primarily a function of auto- and allogenic controls on seagrass density (i.e. turbidity, light, depth, hydrodynamics). The overlying Glenforslan Formation is interpreted as a seagrass-influenced deposit that accumulated under warm-temperate, low mesotrophic conditions and more rapid rates of sedimentation. Relict grains, however, are absent from the Glenforslan Formation. The subtle change in trophic resources is thought to have caused a significant shift in primary and secondary production, from organic carbon- to carbonate-dominated. Assessment of previously described temperate seagrass facies together with this research comprise reliable criteria for identification of temperate seagrass depositional settings. The signal of multigenerational accumulation, especially prominent in the Mannum Formation, represents an amalgamation of environments that would be difficult to assess in modern settings. The key attributes of temperate grass facies proposed herein allow for more accurate reevaluation of seagrass influenced, and relict rich lithologies in the rock record. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-12-14 17:18:16.853

Rising carbon dioxide (CO2) concentrations in the atmosphere will increase the average pCO2 level in the world oceans, which will have a knock-on effect on the marine ecosystem. Coastal seagrass communities one of the most productive marine ecosystems are predicted to benefit from the increase in CO2 levels, but long-term effects of elevated CO2 on seagrass communities are less understood. Population reconstruction techniques was used to investigate the population dynamics of Cymodocea nodosa meadows, exposed to long term elevated CO2 at volcanic seeps off Greece and Italy. Effect of elevated CO2 was noticed on the growth, morphometry, density, biomass and age structure at CO2 seeps. Above to below ground biomass ratio of C. nodosa were higher at CO2 seeps than at reference sites. The plastochrome interval were similar at all CO2 seeps. The shoot age and shoot longevity of plants were lower at seeps than reference sites. The present recruitment (sampled year) of the seagrass were higher than long-term average recruitment of the communities near the seeps. Carbon to nitrogen ratios (%DW) of C. nodosa were higher in leaves at seeps. Annual leaf production was higher near the seeps. This study suggests increased production of C. nodosa under elevated CO2 levels, but other co-factors such as nutrients, trace metal toxicity must also be taken into consideration while predicting effects of future CO2 concentrations. Volcanic CO2 seeps are now being used as natural analogues for ocean acidification studies although these areas can be affected by trace element input and may alter ecosystem responses to gradient in carbonate chemistry. Here Fe and a range of trace elements (Cd, Co, Cu, Hg, Mn, Pb, Ni and Zn) were analysed from sediments and from the roots, rhizomes and leaves of seagrass at six CO2 seeps and reference sites off Greece and Italy. There were higher metal levels in sediment and seagrasses at all CO2 seeps than reference sites. Sediment Quality Guideline Quotient, a commonly used pollution index, indicated that some of the metals (Cd, Cu, Hg, Ni) were in high enough concentrations to have adverse biological effects, such as Cu at Ischia site and Hg at Vulcano. Higher accumulation of elements from sediments in roots and leaves at CO2 seeps were found from Bio Sediment Accumulation Factor index. There were higher levels of Cu, Fe, Mn and Zn in leaves and rhizomes for P. oceanica and higher levels of Cd, Co, Cu, Fe and Zn in C. nodosa compartments at CO2 seeps. Fe and Mn were found with positive correlation within sediment-roots and sediment-rhizomes, whereas Cd, Co and Pb were found with positive correlation in compartments of C. nodosa. In P. oceanica positive correlation were only observed for Cd within sediment-roots and plant compartments. Low pH and ocean acidification increased the concentration of elements at CO2 seeps than reference sites. Thus, caution is needed, when using volcanic seep systems as analogue for the effects of rising CO2, as metals can reach levels that are toxic to seagrass, masking any potential benefits of increased levels of carbon dioxide for seagrass productivity. Net community production (NCP) and community respiration (CR) were measured under air exposed and CO2 enriched conditions for intertidal Z. noltei meadows and unvegetated sediment communities during emersion in summer and winter seasons. Community production and respiration were measured in-situ using benthic chambers. CO2 flux under air and CO2 enriched conditions were measured over a series of short term incubations (30min) using an infra-red gas analyser. Incident photosynthetic active radiation (PAR) was recorded during the incubations covering the daily and seasonal variation. Linear regression model was used to test the effects of irradiance on net community production. NCP of Z. noltei community were higher under CO2 enriched conditions than air exposed conditions in both summer and winter seasons. There was no effect of CO2 on the CR rate of Z. noltei community in summer season. NCP of sediment community were higher in summer season and winter season under CO2 enriched conditions. Sediment CR rates were higher in winter than summer season. The light compensation point of Z. noltei and sediment community were lower in both seasons under CO2 enriched conditions. Seasonal budget of community production was higher in Z. noltei than sediment communities. A clear effect of PAR was noticed on the net community production of both communities. Higher PAR intensities resulted in higher NCP under CO2 enriched conditions for both communities. CO2 enrichment will have a positive effect on the intertidal communities during emersion.

Este trabalho trata da construção de mapas quantitativos de alvos subaquáticos a partir de imagens de satélite. Especificamente, trata da estimativa de biomassa de prados de capim-agulha (Halodue. Wrightii) no litoral de Pernambuco a partir de imagens Landsat5. A coluna d’água altera, de maneira distinta e exponencial os diferentes comprimentos de onda eletromagnéticos distorcendo as correlações existentes entre os mesmos. Devido a isso, torna-se imprescindível eliminar a influência da coluna d’água a fim de que se possa fazer qualquer tipo de análise quantitativa relacionando alvos subaquáticos com a resposta espectral do mesmo. O método testado neste trabalho baseia-se na construção de bandas invariantes em relação à coluna d’água. As bandas invariantes em relação à coluna d”água são feitas a partir de pares de bandas. O coeficiente de determinação (r2) encontrado foi de 0,582 para o par de bandas (2,4) e de 0,709 para o par de bandas( 3,4) o que demonstra a eficiência do método testado. / This work approaches the making of quantitative maps of underwater targets based on satellite images, specifically, the estimate of biomass in seagrass (Halodue Wrightii) fields on Pernambuco’s coast taken from images of Landsat5. The water column distinctly and exponentially alters the different electromagnetic wave lengths, distorting the existing correlation between them. Because of this, it is crucial to eliminate the water column’s effect so that we can carry out different kinds of quantitative analysis relating underwater targets with their spectral response. The method tested in this work is based on the construction of bands that do not vary in relation to the water column. These invariable bands are made from pairs of bands. The determination coefficient (r2) found was 0.582 for the pair of bands (2.4) and 0.709 for the pair of bands (3.4), which shows the efficiency of the abovementioned method.

Este trabalho trata da construção de mapas quantitativos de alvos subaquáticos a partir de imagens de satélite. Especificamente, trata da estimativa de biomassa de prados de capim-agulha (Halodue. Wrightii) no litoral de Pernambuco a partir de imagens Landsat5. A coluna d’água altera, de maneira distinta e exponencial os diferentes comprimentos de onda eletromagnéticos distorcendo as correlações existentes entre os mesmos. Devido a isso, torna-se imprescindível eliminar a influência da coluna d’água a fim de que se possa fazer qualquer tipo de análise quantitativa relacionando alvos subaquáticos com a resposta espectral do mesmo. O método testado neste trabalho baseia-se na construção de bandas invariantes em relação à coluna d’água. As bandas invariantes em relação à coluna d”água são feitas a partir de pares de bandas. O coeficiente de determinação (r2) encontrado foi de 0,582 para o par de bandas (2,4) e de 0,709 para o par de bandas( 3,4) o que demonstra a eficiência do método testado. / This work approaches the making of quantitative maps of underwater targets based on satellite images, specifically, the estimate of biomass in seagrass (Halodue Wrightii) fields on Pernambuco’s coast taken from images of Landsat5. The water column distinctly and exponentially alters the different electromagnetic wave lengths, distorting the existing correlation between them. Because of this, it is crucial to eliminate the water column’s effect so that we can carry out different kinds of quantitative analysis relating underwater targets with their spectral response. The method tested in this work is based on the construction of bands that do not vary in relation to the water column. These invariable bands are made from pairs of bands. The determination coefficient (r2) found was 0.582 for the pair of bands (2.4) and 0.709 for the pair of bands (3.4), which shows the efficiency of the abovementioned method.

Nearshore marine habitats provide critical nursery grounds for juvenile fishes, but their functional role requires the consideration of the impacts of spatial connectivity. This thesis examines nursery function in seagrass habitats through a marine landscape (“seascape”) lens, focusing on the spatial interactions between habitats, and their effects on population and trophic dynamics associated with nursery function to rockfish (Sebastes spp.). In the temperate Pacific Ocean, rockfish depend on nearshore habitats after an open-ocean, pelagic larval period. I investigate the role of two important spatial attributes, habitat adjacency and complexity, on rockfish recruitment to seagrass meadows, and the provision of subsidies to rockfish food webs. To test for these effects, underwater visual surveys and collections of young-of-the-year (YOY) Copper Rockfish recruitment (summer 2015) were compared across adjacent seagrass, kelp forest, and sand habitats within a nearshore seascape on the Central Coast of British Columbia. Recruitment was positively influenced by the structural complexity of seagrass and adjacency to kelp forest sites, however a negative interaction between seagrass complexity and kelp forest adjacency suggests that predation modifies Copper Rockfish recruitment densities. In addition, using δ13C and δ15N isotopes to determine the basal contributions to seagrass food webs, kelp-derived nutrients were on average 47% ± 0.4 of YOY Copper Rockfish diets, which was 3x and 67x greater than the contribution of autochthonous seagrass production (seagrass epiphyte and seagrass blades, respectively). YOY Copper Rockfish diets in seagrass adjacent to sand habitats had the greatest amounts of kelp-derived nutrients and harpacticoid copepods, and concurrently had lower body condition compared to rockfish in the seagrass kelp edges and interior, feeding predominantly on seagrass epiphytes and calanoid copepods. This thesis provides further evidence that temperate seagrasses are nurseries for rockfish and that spatial elements of seascapes, including connectivity via habitat adjacency and variability in habitat structure, alter the recruitment and diets of rockfish in seagrass habitats. These seascape nursery effects are important considerations for marine planning, especially given the global decline of nearshore habitats. / Graduate