Remote sensing of intertidal morphological change in Morecambe Bay, U.K., between 1991 and 2007

Tidal Flats are important examples of extensive areas of natural environment that remain relatively unaffected by man. Monitoring of tidal flats is required for a variety of purposes. Remote sensing has become an established technique for the measurement of topography over tidal flats. A further requirement is to measure topographic changes in order to measure sediment budgets. To date there have been few attempts to make quantitative estimates of morphological change over tidal flat areas. This paper illustrates the use of remote sensing to measure quantitative and qualitative changes in the tidal flats of Morecambe Bay during the relatively long period 1991–2007. An understanding of the patterns of sediment transport within the Bay is of considerable interest for coastal management and defence purposes. Tidal asymmetry is considered to be the dominant cause of morphological change in the Bay, with the higher currents associated with the flood tide being the main agency moulding the channel system. Quantitative changes were measured by comparing a Digital Elevation Model (DEM) of the intertidal zone formed using the waterline technique applied to satellite Synthetic Aperture Radar (SAR) images from 1991–1994, to a second DEM constructed from airborne laser altimetry data acquired in 2005. Qualitative changes were studied using additional SAR images acquired since 2003. A significant movement of sediment from below Mean Sea Level (MSL) to above MSL was detected by comparing the two Digital Elevation Models, though the proportion of this change that could be ascribed to seasonal effects was not clear. Between 1991 and 2004 there was a migration of the Ulverston channel of the river Leven north-east by about 5 km, followed by the development of a straighter channel to the west, leaving the previous channel decoupled from the river. This is thought to be due to independent tidal and fluvial forcing mechanisms acting on the channel. The results demonstrate the effectiveness of remote sensing for measurement of long-term morphological change in tidal flat areas. An alternative use of waterlines as partial bathymetry for assimilation into a morphodynamic model of the coastal zone is also discussed

Solent Disturbance and Mitigation Project Phase II: Predicting the impact of human disturbance on overwintering birds in the Solent.

The Solent coastline provides feeding grounds for internationally protected populations of overwintering waders and wildfowl, and is also extensively used for recreation. In response to concerns over the impact of recreational pressure on birds within protected areas in the Solent, the Solent Forum initiated the Solent Disturbance and Mitigation Project to determine visitor access patterns around the coast and how their activities may influence the birds. The project has been divided into two phases. Phase I collated and reviewed information on housing, human activities and birds around the Solent, and reviewed the potential impact of disturbance on birds. Phase II has involved a programme of major new data collection to (i) estimate visitor rates to the coast from current and future housing, (ii) measure the activities and distances moved by people on the shore and intertidal habitats, and (iii) measure the distances and time for which different bird species respond to different activities. The current report represents the culmination of Phase II, in which the primary data are used to predict whether disturbance may be reducing the survival of birds. Predictions are derived for wader species by developing detailed computer models of birds and disturbance within Southampton Water and Chichester Harbour. These models create a virtual environment within the computer incorporating the intertidal invertebrate food supply of the birds, the exposure and covering of this food through the tidal cycle, disturbance from human activities, and the energy requirements and behaviour of the birds as they avoid humans and search for food. The invertebrate food supply of birds in the models was derived from previous intertidal surveys, and the exposure of intertidal habitat predicted from a tidal model of the Solent. The models incorporate the costs that birds incur when avoiding human activities (e.g. increased density in non-disturbed areas, reduced time for feeding and increased energy demands when flying away), but also their abilities to compensate for these costs (e.g. by feeding for longer or avoiding more disturbed areas). The predictions indicate how disturbance may be effecting the survival of waders throughout the Solent. The following waders were included in the models: Dunlin Calidris alpina, Ringed Plover Charadrius hiaticula, Redshank Tringa totanus, Grey Plover Pluvialis squatarola, Black-tailed Godwit Limosa limosa, Bar-tailed Godwit Limosa lapponica (Chichester Harbour model only), Oystercatcher Haematopus ostralegus and Curlew Numenius arquata. A simpler approach was used to assess how disturbance may be effecting Brent Geese in the Solent. As with any models, the predictions of the models used in this project depend on the data with which they are parameterised and the assumptions they make about the real system. The current and future visitor rates used in the models were themselves predicted using statistical analyses of household survey and on-site visitor data. The responses of birds to disturbance were parameterised using on-site observations of the responses of birds to disturbance. Furthermore, models are a simplification of real systems, and it is important to recognise this when interpreting their predictions. The report considers how the model parameters and assumptions may influence predictions. These include: (i) the way in which the disturbance data were measured and assumptions made about how birds and people are distributed in space and time; (ii) the way in which the behaviour of birds to disturbance differs between sites; (iii) the effect of extreme weather on the birds; (iv) how rare or localised activities are incorporated into the models; and (v) how consumption of food by species other than waders is included. The project predicted changes in visitor numbers to the Solent coast. Local authorities in the Solent region provided projections of future housing developments in the region. These were combined with data on visitor rates to different parts of the coast and the distance travelled to visit the coast, to predict coastal visitor rates with current and future housing. Using current housing levels, 52 million household visits per year to the Solent coast were predicted (i.e. the shore from Hurst Castle to Chichester Harbour, including the north shore of the Isle of Wight). Using the housing data provided by local authorities, visitor numbers were predicted to rise by around 8 million household visits, to a total of 60 million, an overall increase of 15%. Within Chichester Harbour, the food supply surveyed was not predicted to be able to support the majority of wading birds modelled. This implied that either the invertebrate survey underestimated the intertidal food supply, or that other food was available either terrestrially, or from neighbouring intertidal sites such as Langstone Harbour. Similar invertebrate surveys have been used to parameterise 17 other similar models, and in all cases birds were predicted to have survival rates close to, or higher than those expected. Due to uncertainties with the Chichester Harbour invertebrate data, it was decided not to use the Chichester Harbour model to predict the effect of disturbance on the birds. However, it is important to note what the effect of low food abundance would be on the effect of disturbance on the birds. The impact of disturbance on survival and body condition will depend on the birds’ ability to compensate for lost feeding time and extra energy expenditure. Birds will be better able to compensate when more food is available, and so lower food abundance in a site will make it more likely that disturbance decreases survival and body condition. Within Southampton Water, in the absence of disturbance, all wader species modelled were predicted to have 100% survival and maintain their body masses at the target value throughout the course of winter. Disturbance from current housing was predicted to reduce the survival of Dunlin, Ringed Plover, Oystercatcher and Curlew. Increased visitor numbers as a result of future housing was predicted to further reduce the survival of Dunlin and Ringed Plover. Disturbance was predicted to have a relatively minor effect on the mean body mass of waders surviving to the end of winter, largely because the individuals with very low mass starved before the end of winter. The Southampton Water model provided evidence that current and future disturbance rates may reduce wader survival in this site. Hypothetical simulations were run to explore how intertidal habitat area, energy demands of the birds and the frequency of different activities may influence the survival of waders within Southampton Water. The survival rates of Dunlin, Ringed Plover, Oystercatcher and Curlew were predicted to be decreased by any reduction in intertidal habitat area (e.g. due to sea level rise) or increases in energy demands (e.g. due to disturbance at roosts or cold weather). Wader survival was predicted to increase if intertidal activities were moved to the shore. This meant that the disturbance from these activities was restricted to the top of the shore rather than the whole intertidal area, and so the proportion of intertidal habitat disturbed was reduced. Reductions in the number of dogs that were off leads were also predicted to increase the survival of some wader species. Removing bait digging from simulations did not increase wader survival. However, this happened because bait-digging was assumed to be a relatively infrequent activity. This does not mean that bait-digging could not adversely affect the birds if it occurs at a higher frequency, and the simulations did not incorporate the depletion of the invertebrate prey of the birds caused by bait digging, which would be an additional effect on the birds in addition to disturbance. Brent Geese were considered in the light of the Solent Waders and Brent Goose Strategy. Important issues are the size of individual sites, their spacing and the ease with which birds can move between the sites. A high proportion of each site needs to be further away from visitor access routes than the distances over which birds are disturbed to ensure that disturbance to the birds is minimised. This could be achieved through a network of larger sites or by preventing visitor access through, or close to, smaller sites. Both intertidal and terrestrial food resources are important to the birds, intertidal food typically being of higher food value but dying back and / or becoming depleted during the autumn / early winter. Previous models of Brent Geese have predicted that the loss of terrestrial habitat typically has the highest effect on survival, and so such habitat is predicted to be particularly important for the birds. Maintaining a suitable network of saltmarsh sites will be increasingly important as the total area of saltmarsh declines with sea level rise. The findings of the present project are in general support with the recommendations of the Solent Waders and Brent Goose Strategy. Predicted current visitor rates varied widely throughout the Solent, but were relatively high within Southampton Water. The highest percentage increases in visitor rates were on the Isle of Wight (50-75%). Wader survival was predicted to be decreased in Southampton Water when daily visitor rates to coastal sections were greater than 30 per ha of intertidal habitat. The potential impact of visitors on wader survival throughout the Solent was calculated by comparing visitor densities throughout the Solent (expressed relative to maximum intertidal habitat area) to the visitor densities predicted to decrease bird survival within Southampton Water. The intertidal food supply within Chichester Harbour was insufficient to support the model birds and so any disturbance (by reducing feeding area or time, or increasing energy demands) would have decreased predicted survival in this site. There is also doubt as to the food supply within the other harbours and so some caution is appropriate when applying the results from Southampton Water to these sites. Coastal sections with daily visitor rates over 30 per ha are identified. The predictions of the Southampton Water model suggest that birds within these sections may have reduced survival due to disturbance from visitors. Whether or not such visitor rates will reduce survival will depend on the food abundance in the coastal sections themselves as well as that in neighbouring sections. The area of overlap between an activity / development and the distribution of birds is often used as a measure of the impact of the activity on the birds, with 1% overlap often taken as the threshold for impact (note however that this 1% overlap does not necessarily mean that an activity will have an adverse effect on the survival or body condition of birds). Therefore, the percentage of intertidal habitat disturbed within each coastal section was calculated as an index of the potential impact of disturbance on the birds. Assuming the maximum intertidal area and only including intertidal visitors, over 50% of the area of many coastal sections was predicted to be disturbed, with an average of 42%

Impacto de depredadores y niveles de recursos sobre rasgos fisiológicos de Fissurella crassa (Archeogastropoda

Indexación: Web of Science; RedalycThe effects of predators on the density of prey and their resources have been widely studied; however, there is little evidence on the effects of the predators in conjunction with the availability of resources on the traits of the prey, which could affect foraging activities. In this study, the physiological state and the escape response of the intertidal herbivore Fissurella crassa were evaluated in two sites which differ in terms of the abundance of its predator Heliaster helianthus. The results suggest that the escape response of F. crassa in the site with greater predator density and lower resource availability could require a better body condition that is compensated with increments in foraging. The results highlight the need to address the physiological perspective in community ecology in order to understand the interactions within these communities.Los efectos de los depredadores sobre la densidad de presas y sus recursos ha sido ampliamente estudiado, sin embargo existe escasa evidencia sobre los efectos de los depredadores en combinación con la disponibilidad de recursos relacionados con los rasgos de las presas que pueden afectar la actividad de forrajeo. En este estudio se evaluó el estado fisiológico y la respuesta de escape del herbívoro intermareal Fissurella crassa en dos sitios con diferencias en la abundancia de su depredador Heliaster helianthus. Los resultados sugieren que la respuesta de escape de F. crassa en el sitio de mayor densidad del depredador y baja disponibilidad de recursos, podría requerir una mejor condición corporal que se compensé con un incremento en el forrajeo. Los resultados destacan la necesidad de abordar la perspectiva fisiológica en ecología de comunidades para entender mejor las interacciones dentro de estas comunidades.http://www.redalyc.org/articulo.oa?id=5784430400

Freezing tolerance and survival experiments with various intertidal organisms from Kachemak Bay, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2004Intertidal organisms at high latitudes experience multiple stresses created by freezing, including ischemia, free water reduction, and distortion and destruction of cells, and in response have adapted behavioral and physiological solutions. This study examined the response of intertidal organisms in Kachemak Bay, Alaska to freezing through laboratory experiments and field studies. Mytilus trossulus, Balanus glandula, Protothaca staminea and various limpets (Lottidae) survived freezing conditions to -10 and -20°C, depending on the season. Mytilus trossulus and B. glandula survived multiple freeze events at -10°C. Seasonal freeze response was not induced by exposure to low air temperature in M trossulus. Exposure to O⁰C was not fatal to any of the species studied: M trossulus, B. glandula, P. staminea, limpets, Fusitriton oregonensis, Katharina tunicata and Leptasterias hexactis. Preliminary results suggest that M trossulus and P. staminea have an ice nucleator. Freezing avoidance may be one cause for the differences seen in seasonal distribution patterns of F. oregonensis, Nucella lima, Onchidella borealis, Siphonaria thersites and Littorina sitkana. The current study demonstrated that intertidal organisms in this region exhibit differing responses to freezing. Some organisms survive freezing conditions by freeze tolerance, while others may avoid it by moving lower in the intertidal

The composition and resilience of rockpool fish assemblages on the central Hawke's Bay coast New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University

Irregular pagination.Fish assemblages in rockpools on two intertidal platforms on the Central Hawke's Bay coast of New Zealand were studied from June 2000 to March 2001. Twenty-four species belonging to 14 families were collected from 226 rockpool censuses. The Tripterygiidae were the most speciose family, represented by 7 species. Fifty-seven percent of the total number of fish captured (n = 6133) belonged to a single species, the robust triplefin Grahamina capito. Common subtidal species contributed significantly to the taxocene, indicating that much of the rockpool fish fauna is an extension of that in the shallow subtidal fringe. However, two specialist intertidal species (Acanthoclinus fuscus and Bellapiscus medius) were relatively abundant in the collections. Significant relationships between rockpool fish assemblage structure, and rockpool habitat structure were discovered. Richness, abundance and biomass were generally greater in large pools with lots of shelter, located close to the low-tide mark. Further analysis revealed that assemblages in these pools contained many partial residents that were uncommon or absent from rockpools higher on the shore. Seasonality in the structure of rockpool fish assemblages was related primarily to recruitment events. During late spring and early summer, the abundance and density of resident species increased markedly as the result of an influx of settling larvae. However, species richness remained stable over the sampling period, probably because transient subtidal species (with the exception of the labrid, Notolabrus celidotus) did not contribute significantly to the rockpool fish community. The rockpool fish community appeared to be resilient: taxocene structure re-established between collection events. However, the level and rate of resilience appeared to be lower than described in other studies, as the effects of sampling were still measurable after 3-months. The recovery of richness, abundance and biomass of fish was seasonally dependent, being slow in winter and spring, but rapid during summer. Specialist intertidal species were generally the best recolonisers, whereas partial resident species were poor recolonisers, and relied mainly on larval recruitment to colonise rockpools

Characterization of Ground Water Discharge to Hampton Harbor

The project goals were to assess inter-tidal groundwater discharge and concurrent nutrient loading to Hampton Harbor. This will include maps of suspected groundwater discharge zones and measurements of nutrient loading. The principal means of assessment was an aerial survey of the study area during low tide using thermal infrared (TIR) imagery. The TIR imagery was used to detect and locate upwelling groundwater discharge zones within the harbor. The location of groundwater discharge zones as it relates to upgradient land use can be instructive for water quality

Ecological linkages: Marine and estuarine ecosystems of Central and Northern California

Three of California’s four National Marine Sanctuaries, Cordell Bank, Gulf of the Farallones, and Monterey Bay, are currently undergoing a comprehensive management plan review. As part of this review, NOAA’s National Marine Sanctuary Program (NMSP) has collaborated with NOAA’s National Centers for Coastal Ocean Science (NCCOS) to conduct a biogeographic assessment of selected marine resources using geographic information system (GIS) technology. This report complements the analyses conducted for this effort by providing an overview of the physical and biological characteristics of the region. Key ecosystems and species occurring in estuarine and marine waters are highlighted and linkages between them discussed. In addition, this report describes biogeographic processes operating to affect species’ distributional patterns. The biogeographic analyses build upon this background to further understanding of the biogeography of this region. (PDF contaons 172 pages

Morphological response of the saltmarsh habitats of the Guadiana estuary due to flow regulation and sea-level rise

In the context of rapid sea-level rise in the 21st century, the reduction of fluvial sediment supply due to the regulation of river discharge represents a major challenge for the management of estuarine ecosystems. Therefore, the present study aims to assess the cumulative impacts of the reduction of river discharge and projected sea-level rise on the morphological evolution of the Guadiana estuary during the 21st century. The assessment was based on a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters and empirical knowledge of the system. As methods applied to estimate environmental flows do not take into consideration the fluvial discharge required to maintain saltmarsh habitats and the impact of sea-level rise, simulations were carried out for ten cases in terms of base river flow and sea-level rise so as to understand their sensitivity on the deepening of saltmarsh platforms.Results suggest saltmarsh habitats may not be affected severely in response to lower limit scenarios of sea-level rise and sedimentation. A similar behaviour can be expected even due to the upper limit scenarios until 2050, but with a significant submergence afterwards. In the case of the upper limit scenarios under scrutiny, there was a net erosion of sediment from the estuary. Multiplications of amplitudes of the base flow function by factors 1.5, 2, and 5 result in reduction of the estimated net eroded sediment volume by 25, 40, and 80%, respectively, with respect to the net eroded volume for observed river discharge. The results also indicate that defining the minimum environmental flow as a percentage of dry season flow (as done presently) should be updated to include the full spectrum of natural flows, incorporating temporal variability to better anticipate scenarios of sea-level rise during this century. As permanent submergence of intertidal habitats can be significant after 2050, due to the projected 79 cm rise of sea-level by the year 2100, a multi-dimensional approach should be adopted to mitigate the consequences of sea-level rise and strong flow regulations on the ecosystem of the Guadiana Estuary. (C) 2016 Elsevier Ltd. All rights reserved