Monitoring in the Western Pacific region shows evidence of seagrass decline in line with global trends     

Frederick T. Short  Robert Coles  Miguel D. Fortes  Steven Victor  Maxwell Salik  Irwan Isnain  Jay Andrew  Aganto Seno 《Marine pollution bulletin》2014

Seagrass systems of the Western Pacific region are biodiverse habitats, providing vital services to ecosystems and humans over a vast geographic range. SeagrassNet is a worldwide monitoring program that collects data on seagrass habitats, including the ten locations across the Western Pacific reported here where change at various scales was rapidly detected. Three sites remote from human influence were stable. Seagrasses declined largely due to increased nutrient loading (4 sites) and increased sedimentation (3 sites), the two most common stressors of seagrass worldwide. Two sites experienced near-total loss from of excess sedimentation, followed by partial recovery once sedimentation was reduced. Species shifts were observed at every site with recovering sites colonized by pioneer species. Regulation of watersheds is essential if marine protected areas are to preserve seagrass meadows. Seagrasses in the Western Pacific experience stress due to human impacts despite the vastness of the ocean area and low development pressures.  相似文献   

Incorporating resilience into sustainability indicators: An example for the urban water sector   总被引：2，自引：0，他引：2  

Anita Milman  Anne Short   《Global Environmental Change》2008,18(4):758

The development and use of indicators is common practice in efforts to promote urban sustainability. Indicators used to measure urban sustainability tend to focus narrowly on describing the current state of the urban system. Although a time series analysis using these indicators may lend insights into trends towards or away from certain ‘sustainability’ goals, existing indicators of urban sustainability do not provide information on the ability or the likelihood that the current system state can be maintained or improved over time. Indicators that incorporate a measure of system resilience would provide useful information on system sustainability. Through development of a new indicator, Water Provision Resilience (WPR), we provide an example of how measures of resilience could be incorporated into sustainability indicators. The new indicator adds six color codings to the existing indicator ‘percent of the population with access to safe water.’ Each color coding represents a measure of the ability of the water system to maintain or improve the current percent of the population with access to safe water in key areas of the water provision sector: supply, infrastructure, service provision, finances, water quality and governance. The metric is then applied to three cities. The goal in developing this metric is to provide a starting point for re-thinking the metrics used to measure progress and sustainability in order to incorporate the ability to absorb and adapt to stresses into sustainability analysis.  相似文献   

Habitat suitability curves for benthic macroinvertebrates from a small New Zealand river     

KA Shearer  JW Hayes  IG Jowett  DA Olsen 《新西兰海洋与淡水研究杂志》2013,47(2):178-191

We developed habitat suitability curves (HSC) using generalised additive models (GAMs) for nine benthic macroinvertebrate taxa from a small New Zealand river for hydraulic-habitat modelling assessments of instream flow requirements. We included interaction terms between the primary variables (water depth, velocity, substrate) when significant, to address a longstanding criticism of univariate HSC. To date, only large-river univariate HSC have been available and these have been used in hydraulic-habitat applications on small rivers, despite doubt over the transferability of HSC between rivers of different size and type. We tested the outcome on the predicted abundance–flow relationship of applying the small-river habitat suitability GAMs versus large-river GAMs for two taxa on the same small river. We found the effects of flow allocation were overestimated by the large-river GAMs relative to the small-river GAMs. Further research to develop general HSC for categories of river size and type is needed to better inform hydraulic-habitat modelling applications.  相似文献   

Lobster use of eelgrass habitat in the Piscataqua River on the New Hampshire/Maine Border, USA     

F. T. Short  K. Matso  H. M. Hoven  J. Whitten  D. M. Burdick  C. A. Short 《Estuaries and Coasts》2001,24(2):277-284

The relationship between lobsters and eelgrass beds was investigated in the Piscataqua River, which constitutes the lower portion of the Great Bay Estuary, New Hampshire and Maine. The goals of the study were to assess the numbers, size distribution, and sex distribution of lobsters in eelgrass beds, to determine whether lobsters in the eelgrass beds were transients or residents, and to investigate eelgrass density preferences among adolescent lobsters. Eighty percent of the lobsters collected from eelgrass beds were adolescents, measuring >40 to 70 mm carapace length (CL). Of the 295 lobsters collected at four different eelgrass beds, we found an average male-to-female ratio of 1.2. Tag/recapture efforts in eelgrass beds (1.5 to 4 mo interim period) yielded an average recapture of 5.5%. Twenty transects, each 10 m in length, sampled at two eelgrass sites revealed a lobster density of 0.1 m⁻². In mesocosm experiments, lobsters (53–73 mm CL) showed a clear preference for eelgrass over bare mud. Our investigations showed that adolescent lobsters burrow in eelgrass beds, utilize eelgrass as an overwintering habitat, and prefer eelgrass to bare mud.  相似文献   

Paleoecology of late-glacial peats from the bering land bridge, Chukchi Sea shelf region, northwestern Alaska     

Scott A. Elias  Susan K. Short  R. Lawrence Phillips 《Quaternary Research》1992,38(3)

Insect fossils and pollen from late Pleistocene nonmarine peat layers were recovered from cores from the shelf region of the Chukchi Sea at depths of about 50 m below sea level. The peats date to 11,300−11,000 yr B.P. and provide a limiting age for the regional Pleistocene-Holocene marine transgression. The insect fossils are indicative of arctic coastal habitats like those of the Mackenzie Delta region (mean July TEMPERATURES = 10.6–14°C) suggesting that 11,000 yr ago the exposed Chukchi Sea shelf had a climate substantially warmer than modern coastal regions of the Alaskan north slope. The pollen spectra are consistent with the age assignment to the Birch Interval (14,000–9000 yr B.P.). The data suggest a meadow-like graminoid tundra with birch shrubs and some willow shrubs growing in sheltered areas.  相似文献   

Quaternary inheritance of coastal landforms,Cobourg Peninsula,northern territory     

C. D. Woodroffe  E. A. Bryant  D. M. Price  S. A. Short 《The Australian geographer》1992,23(2):101-115

In contrast to the abundant evidence of former shorelines on the sea floor of the Sahul Shelf in northern Australia, little evidence has been reported for late Pleistocene coastal landforms along the modern coast of north Australia. Using radiocarbon, thermoluminescence and uranium/thorium dating techniques, however, it can be shown that the present coastal morphology on the Cobourg Peninsula is partly inherited from features both deposited and eroded during the late Quaternary. Shore platforms, in particular, are veneered with ferricretes, some of which can be U/Th dated. In places bedforms are preserved within the ferricrete, suggesting that the platform existed at, and was modified during, the Last Interglacial, and probably formed during earlier interglacials. TL dating indicates that sands around Cape Don were deposited when sea level was lower, but may have been reworked during a Holocene high stand. A sequence of beach ridges at Smith Point indicates Holocene progradation over an earlier planation surface, and also provides support for slight Holocene emergence.  相似文献   

Functional trajectory models for assessment of transplanted eelgrass,Zostera marina L., in the Great Bay Estuary, New Hampshire     

N. Tay Evans  Frederick T. Short 《Estuaries and Coasts》2005,28(6):936-947

Functional trajectory models were used to assess the restoration of ecological functions in two transplanted eelgrass (Zostera marina L.) beds compared to three natural, reference beds in the Great Bay Estuary, New Hamsphire. Functional trajectory models describe the development of ecological functions over time in restored habitats relative to levels of function in natural habitats. We present the first application of trajectory models to transplanted seagrass and evaluate the utility of these models as a tool for assessing seagrass restoration. The project was an analysis of 9 yr of monitoring data, the longest monitoring of transplanted eelgrass to date. We used trajectory models to assess the time course of development of functions in transplanted beds by evaluating statistical trends, and to determine functional equivalence, defined as the time when functions in a transplanted bed reach an asymptote and are no more than 1 standard deviation below the reference mean. The functions modeled included primary production, 3-dimensional habitat structure, faunal use, and sediment filtering and trapping. Measured proxies for primary production and habitat structure increased logistically (sigmoidally) with time, reaching functional equivalence after 3 yr. In transplanted beds, trends in habitat use by infaunal invertebrates and fish were logarithmic, and values were functionally equivalent 2–4 yr after transplanting. We saw no trend in sediment filtering and trapping capacity of transplanted eelgrass over the 9 yr. Measures of function in both reference and transplanted beds fluctuated due to natural and anthropogenic disturbances. After reaching equivalence, measures of function in transplanted beds tracked those in reference beds, exhibiting long-term persistence and rebounding from disturbances similarly to reference beds. Trajectory models can illustrate the time course of eelgrass bed development, aiding the design of monitoring programs and the evaluation of ecological functional equivalence in seagrass restoration projects.  相似文献   

Production and nutrient dynamics of aSyringodium filiforme Kütz. Seagrass bed in Indian River Lagoon,Florida     

F. T. Short  J. Montgomery  C. F. Zimmermann  C. A. Short 《Estuaries and Coasts》1993,16(2):323-334

A year-long analysis of the characteristics of the seagrassSyringodium filiforme and the associated dynamics of the nutrient pool in the sediment pore water was done to assess co-variation. Changes in seagrass growth rate and standing stock throughout the year were accompanied by seasonal changes in the nutrient pools. The link between plant production and morphometrics and the sediment nutrient pool was found to be predominantly physiological, with the plant balancing the ability to photosynthesize with the nutrients needed for maintaining production. Measurements of whole plant growth for this seagrass, rather than the more typical leaf growth measurements, show that the production of new shoots and rhizome elongation for these plants represents as substantial amount of growth that usually goes unmeasured. Further, these whole plant growth measures demonstrate the rapid lateral rhizome spread of this species, exceeding one meter per plant per year. The primary cause of seasonal variation in the yearly seagrass cycle was investigated. Correlation analysis supported the hypothesis that the major factor controlling seasonal variation in this seagrass was light. During the peak growing season, however, growth was not regulated by light but by nitrogen. Depletion of the sediment ammonium pool and reduction in pore water ammonium relative to adsorbed ammonium, as well as changes in N content of seagrass leaves, support our hypothesis of peak growing season nitrogen limitation. Our results forSyringodium filiforme in terrigenous sediments are in contrast to our recent findings of phosphorus limitation in this same species occurring in carbonate sediments.  相似文献   

Tafoni in the El Chorro area,Andalucia, southern Spain     

A. Mellor  J. Short  S. J. Kirkby 《地球表面变化过程与地形》1997,22(9):817-833

Using a combination of field, laboratory and micromorphological evidence, this study examines tafoni (singular, tafone) in the El Chorro area of Andalucia, southern Spain, and makes inferences concerning the processes responsible for their formation. Twenty-five tafoni were randomly selected for field examination. The morphology of these cavernous rock domes is characterized by a helmet-shaped outer roof and an arched-shaped cavern, often with a partially overhanging visor; measurements of height, width and depth of the caverns revealed marked variations in size. The presence or absence of lichen cover, surface varnish, overhanging visor, cavern backwall stripes, rock flaking, weathering pits and cavern floor sediments was also noted. Surface hardness values, obtained using a Schmidt hammer, are relatively low but significantly higher on the outer roof of the tafoni than on the inner cavern walls. Analysis of sediment samples collected from the cavern backwalls and floors indicates predominantly sandy textures, alkaline pH values and some base cation enrichment. Micromorphological analysis of thin sections, prepared from undisturbed blocks, reveals large quantities of pore-filling cement, consisting mainly of calcite, mineral grains affected by weathering and pseudomorphic replacement, and dark, rounded nodules with a metallic appearance. In terms of their formation, different processes appear to act on different parts of the landform. On the outer roof surfaces, case hardening, resulting from near-surface cementation and surface varnish development, is dominant. On the inner cavern surfaces, however, core softening, resulting from granular disintegration and flaking, dominates. Exfoliation weathering, running water and wind deflation also appear to play an important role in tafone formation. A phased model of tafone evolution is proposed whereby the features pass through four phases of development–initiation, enlargement, amalgamation and degradation; in the study area there are examples of tafoni in each of these phases. Much of the evidence suggests that the tafoni are actively developing under current environmental conditions. © 1997 by John Wiley & Sons, Ltd.  相似文献   

Uranium/thorium dating of ferricretes from mid- to late pleistocene glacial sediments,western Tasmania,Australia     

Paul C. Augustinus  Stephen A. Short  Henk Heijnis 《第四纪科学杂志》1997,12(4):295-308

The uranium/thorium (U/Th) dating method was applied to pedogenic/diagenic ferricretes developed within glacial drifts from the northern West Coast Ranges of Tasmania. The dates derived from the method are, by definition, minima for the sediments, with the ferricretes being secondary mineral deposits which appear in the form of bands, horizons or nodules comprised of indurated masses of iron oxy(hydr)oxides developed post-depositionally within the host sediment or soil. The absence of such deposits in well-identified drift sediments of the last glaciation suggests the development of ferricrete horizons in glacial drifts occurred during earlier interstadials and interglacials. This has been confirmed by the uranium/thorium dating of ferricrete bands within glacigenic sediments obtained from three drill cores from the Boco Valley. The ages derived were found to be consistent with estimates for the timing of glaciation derived from palaeomagnetic analyses, radiocarbon dating and relative dating techniques. The results show that the uranium/thorium method can be used to successfully date ferricretes obtained from within glacial sediments of ages <350000 yr and provides valuable information regarding the minimum age of the host sediment. © 1997 John Wiley & Sons, Ltd.  相似文献